Lightning Protection for Engineers (National Lightning Safety Institute NLSI, 2006 Year)

SAFETY IS THE PREVAILING DIRECTIVE (IEEE 1100-2005,3.1.5)

Dedication To Dad and Mom and Lynda and Lindsey. For your Guidance, Influence, Inspiration and Memories. Rich K., August 2006

But to him who's scientific There is nothing more te"ijic In the falling ofthe flight ofthunderbolts; Yes, in spite ofall my meekness IfI have a little weakness It's a passion for a flight ofthunderbolts. -

GILBERT AND SULLIVAN, The Mikado

I "Lightning Protection for Engineers" was revised and updated in May 2007 I

INTRODUCTION by Josephine Covino, PhD Chairperson, Lightning Protection Review Committee Department ofDefense Explosives Safety Board http://www.hqda.army.mil/ddesb/esb.html Washington DC In 1926 lightning visited the Naval Ammunition Depot at Lake Denmark NJ. The incident virtually destroyed the Depot and caused heavy damage to nearby Picatinny Arsenal and surrounding communities. Twenty one people were killed and fifty one others injured. Damage to the Navy area alone was $46 million in 1926 dollars. The problem of lightning safety is not unique to the USA. In June 1998 lightning destroyed a large Russian Army munitions depot in the Ural mountains, near the village of Losiniy 30 kIn northeast of Yekaterinburg. At least 14 army personnel including the base commander were killed and 1300 villagers were evacuated from the area. Sources report that 240 tons ofstores were destroyed. In 2002 at a railyard in Beira, Mozambique lightning insulted a military explosives depot with considerable damage and injuries. As an outgrowth of the Lake Denmark event, in 1928 Congress established the Department of Defense Explosives Safety Board (DDESB). 'Since then we have collected 55 verifIable lightning-caused accidents in our database. The lightning safety compliance regulation DDESB 6055.9 is mandatory for military explosives installations. While DDESB takes the lightning issue seriously, for the most part this is not the case with the commercial and industrial workplace. In Denver in 1996, a refrigerated warehouse was struck by lightning and the loss was $55 million. Recent substantiated data from the National Lightning Safety Institute places annual USA lightning costs and losses at about $4-5 billion per year. The general public too does not fully appreciate lightning's hazards. Boaters, golfers, school children and people from most other walks oflife too often are victims of lightning. Education and attention to detail are the keys to lightning safety. Lightning Protection For Engineers makes a valuable contribution to the literature for such groups as specifying architects and engineers, those Authorities Having Jurisdiction, educators, libraries and interested local, state, and federal officials. We all need to improve our understanding of lightning safety issues.

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A FEW WORDS ABOUT THE USE OF THIS BOOK. Lightning protection in an absolute sense is impossible because of the arbitrary, capricious, and stochastic nature of lightning strikes. Some twenty five million of them striking in the USA annually each have unique characteristics. The protection approach is highly site-specific, with many designs unique to individual facilities and structures. Mitigation of lightning insults is attempted through the deployment of a combination of exterior and interior defenses. The purpose of this Workbook is to describe and illustrate those defensive systems as they are applied in various situations. When employed in combination, the following sub-systems represent a layered defensive strategy, commonly called a Lightning Protection System (LPS). Air Terminals - an exterior defense. Lightning usually terminates on grounded objects sticking up in the air. Franklin rods are air terminals. Overhead steel cables and metal masts are air terminals. Steel towers are air terminals. Trees are air terminals. In the absence of taller objects, fences and blades of grass are air terminals. Old Ben's design developed in 1752 carried lightning from rods in the air via conductors to rods in the ground. This rod-configuration on buildings was and is based upon the Path of Least Resistance laws of physics. Nowadays, some vendors are promoting unconventional air terminal designs (ESE/DAS/CTS) seeking to gain advantage over competitors. Caveat Emptor. Of course, should lightning strike across the street from a protected facility center and couple into sensitive electronics via underground wiring, then no air terminals design of any classification has performed its role in protection. Grounding -an exterior defense. Low impedance and resistance grounding provides an efficient destination for the Lightning Beast. If site soils are composed of sand or rock they are resistive, not conductive. If surrounding soils are clays or dirt, they may be conductive. "Good Grounds" are achieved with properly configured volumetric efficiencies. We recommend buried bare 4/0 copper wire - the so called ring electrode or ring ground. Cadwelding© security fences, tower legs, and other adjacent metallics to the buried ring will augment the earth electrode sub-system. NEC 250 describes other grounding designs such as rods, plates, water pipes (beware plastic pipes underground), metal frame of bUildings, and concrete-encased electrodes. Choose your grounding design based upon localized conditions and the amount of available real estate at your location. NEC 250.56 suggests a target earth resistivity number of 25 ohms. Lower is better. Bonding - an interior defense. Without proper bonding, all other elements of the LPS are useless. Bonding of all facility incoming metallic penetrations - cables, conduits, pipes and wires - assures all of them are at equal potential. There are many interior "grounds" in modern buildings, such as computer grounds, AC power grounds,

lightning grounds, single point grounds, and multi-point grounds. All must be bonded so as to achieve the same potential. When lightning strikes, all grounded equipment must rise and fall equipotentially. This will eliminate the differential voltages in separate sensitive signal and data systems. Bonding serves to connect all conductors to the same "Mother Earth." Not convinced bonding is important? Check out NEC 250.90 through 250.106 for more details. Surge Suppression - an interior defense. Surge suppression devices (SPDs) all function either by absorbing the transient as heat or crowbaring the transient to ground (or some combination thereof). SPDs should be installed at main panel entries, critical branch or secondary panels, and plug-in outlets where low voltage transformers convert AC power to DC current and voltage. SPDs also ~hould be installed at signal and data line facility entry points and at electronic equipment. Telephone punch blocks should be Spo-protected. Beware the junk SPDs which proliferate the marketplace. Beware counterfeit or false UL and IEEE labeling. Beware of the "it sounds to good to be true" marketing hype employed by vendors. Insist on Certified Test Results to substantiate performance claims by manufacturers. Consider SPDs which have capabilities to remotely signal their operational performance. SPDs rank right behind Bonding in the hierarchy of important steps to mitigate the lightning hazard. Codes and Standards. There are excellent codes and standards, helpful codes and standards and superficial codes and standards. No one such document by itself provides comprehensive guidance for the lightning protection engineer. Familiarity with, many recognized codes and standards is vital for competency in lightning problem-solving.

NlSI Note about Sources: Some of this Workbook is original material and some is reproduced from other sources. Thanks to organizations such as Bellcore, IEEE, Erico, Dehn, MTL, IEC, NFPA, Polyphaser, lPC, MCG, Phoenix Contact, CITEl, APC, Telebyte, IEC, API, ICAE, NOAA, Vaisala, NASA, NCHRP, STC, Motorola, FAA, DOD, DOE, FAA, USGA, IClP, ILDC, ERA and others. Thanks also to individual friends worldwide in academia, business, government, industry, and the private sector.

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TABLE OF CONTENTS

1. Lightning Physics, Lightning Behavior And Lightning Safety Overview

1-22

2. Risk Assessment

23-40

3. The Grounding and Bonding Imperative

41-76

4. Exterior Lightning Protection for Structures

77-94

5. Interior Lightning Protection for the Electrical System of a Complex Facility

95-114

6. Communications Facilities, Exterior Lightning Protection

115-128

7. Communications Facilities, Interior Lightning Protection

129-150

8. Lightning Protection for High Risk Installations Containing Sensitive Electronics, Explosives, Munitions or Volatile Fuels

151-170

9. International View of Unconventional Air Terminals such as "ESE" and "DAS/CTS"

171-194

10. Lightning Safety for Outdoor Activities

195-214

11. References, Resources, Codes & Index

215-249

1

INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter One

LIGHTNING PHYSICS, LIGHTNING BEHAVIOR AND LIGHTNING SAFETY OVERVIEW

Early Creeks beli~ed that lightning W3S the weapon of 'Zeus.

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4 4 Chapter One Overview Lightning is arbitrary~ capricious~ rando~ stochastic and unpredictable. Science does not fully understand its phenomenology. However, investigations from today~ s researchers is considerable. While lightning creates major upsets and significant dollar losses to the economy~ safety from its effects is rarely employed proactively. Absolute protection is impossible but deployment of a holistic~ systematic approach can mitigate the hazards. gene~

many errors and misunderstandings dominate lightning protection efforts. "Lightning never strikes twice" is not correct. "Lightning rods provide safety for people" is not correct. New information slowly is altering the 19th Centmy Conventional Wisdom. In

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THUNDERSTORM CONVECTION PROCESS PRODUCES LIGHTNING Simplified Version: The Sun evaporates surface moisture, transforming it into clouds/gas/water vapor. Hot air causes clouds to rise over time. At about -15 C degrees, gas is transformed into solids/ice/hygrometeoriteslgraupuls. High winds (160 kmlhr) tumble the solids, with the collision process/.friction creating static electricity.

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"COLD' LIGHTNING IS A LIGHTNING FLASH WHOSE MAIN RETURN STROKE IS OF INTENSE CURRENT BUT OF SHORT DURATION. "HOT' LIGHTNING INVOLVES LESSER CURRENTS BUT LONGER DURATION. HOT LIGHTNING IS MORE 'APT TO START FIRES. COLD LIGHTNING GENERALLY HAS MECHANICAL AND/OR EXPLOSIVE EFFECTS.

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BEHAVIOR OF LIGHTNING - PART ONE As downward Leaders approach earth they may induce electrical and magnetic signatures upon grounded objects. Grounded objects may respond in stages: 1) accelerated electron behavior; 2) corona emissions; 3) launch of upward Streamers. When Leaders and Streamers connect, a preferential path to ground is established. Below are conditions for the Final Jump.

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BEHAVIOR OF LIGHTNING - PART TWO Leaders close to the ground enter a "Cone of Discrimination" where they may choose to strike one or more ground targets. Striking Distance is a function of Peak Current (below). Horvath (1969, 1971) concluded that ground corona current increases in response to elevated electric fields. A "glow-to-arc" transition from point discharge (corona) to upward Streamer stage can occur at about 10 to 50 mAo Peak Current is the determining agency.

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ATMOSPHERIC CHARGE REDISTRIBUTION (ACR)

Before, during and after lightning strikes to ground, highly mobile charged cloud centers redistribute themselves attempting to reach equilibrium with opposing polarity earth charges, including man-made (conductive) structures. This ACR creates strong electromagnetic fields similar to those of lightning. ACR can deliver voltage and current surges into conductors similar to those caused by cloud-to-ground lightning.

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RESISTIVE, MAGNETIC FIELD & ELECTRIC FIELD COUPLING The coupling of lightning transients into sensitive electronics can arise from different mechanisms as a result of direct and/or indirect (distant) lightning.

Resistive Coupling When a facility is struck by lightning, the current flow into the earth usually generates high voltages between . the power supply and the remote earth. Partial lightning currents then flow in electrical and signal & data conductors which are a part of the structure and which are connected to remote earth.

Magnetic Field Coupling Lightning current, flowing either in a conductor or in the lightning channel itself, produces a high magnetic field. Where the magnetic field attaches to -electrical and signal & data conductors it causes -voltages in loops fonned by these conductors.

Electric Field Coupling The nearby lightning stroke contains a high electric field which charges electricallyconductive objects like a large capacitor. The air becomes a dielectric mediuni. High voltages arise in electrical and signal & data conductors, even though the structure was not directly struck.

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THE LIGHTNING ATTACHMENT PROCESS

When lightning strikes at or nearby to a critical or high value facility, stroke currents will divide up among all parallel conductive paths between the attachment point(s) and earth. Division of current will be inversely proportional to the path impedance Z, (Z = R + XL, resistance plus inductive reactance). The resistance term will be very low, assuming effectively bonded metallic conductors. The inductance and corresponding related inductive reactance presented to the total return current will be determined by the combination of all the individual inductive paths in parallel-the more parallel paths, the lower the total impedance. Lightning can be considered current source, Le. output current is independent of load impedance. A given stroke wi II contain a certain amount of charge (coulombs = amps x seconds) that must be neutralized during the discharge process. If the return stroke is 50 kA, then that is the magnitude of current that will flow, whether it flows through one ohm or 1000 ohms. Therefore, achieving the lowest possible path impedance serves to minimize the transient voltage developed across the path through which the current is flowi~g [e(t) = I(t)R + L di/dt)]. ..

A risk management approach to lightning safety must assume the facility will be struck by lightning. Now what? By adopting a judicious combination of defenses, the lightning safety engineer can attempt to mitigate lightning's consequences. Since each facility is unique, as is each lightning flash, site-specific designs must be applied. Application of integrated approaches for air terminals, ground terminals, conductors, bonding, shielding, surge protection devices, etc. will depend on the geographic location and the perceived risk to the facility. National Lightning safety Institute 891 N. Hoover Ave . Louisville CO 80027

14

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Thunderstorm Days Per Year .

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Argentina 30-80 Colombia Cerromatoso 275-320 Brasil 40-200 USA Florida 90-110 Colorado 65-100 35-50 Japan Australia 10-60 Malaysia 180-·260 Indonesia 180-260 Bogor (1988) 322

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About 2000 global conti.nuons Thunderstorms deliver about· 75-100 strikes/sec. to earth.

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A network of sensors record cloud-to-ground lightning flashes. Approx. efficiencies are: detection of flashes 90% ; distance (ranging) 400-500 ffi. Operated by National Lightning Detection Network (NLDN) in USA and by other organizations in many other countries.

17

LITTLE-KNOWN LIGHlNING INFORMATION 1. LIGHTNING PROTECTION SYSTEMS PROVIDE LIMITED PROTECTION. "What we found out was that the lightning protection system played a limited role in directing current from a lightning strike...[instead] current traveled through the rebar, through concrete, through pipes, through cables, through vent stacks, and through the electrical system..." - Results of rockettriggered testing sponsored by US Government. Source: Marvin Morris, Electromagnetic Test and Analysis Dept., as quoted in Sandia Lab News, April 25, 1997, Sandia Natl Lab, Albuquerque NM 2. THE AVERAGE DISTANCE BETWEEN SUCCESSIVE FLASHES IS GREATER THAN PREVIOUSLYKNOWN. Old data said successive flashes were on the order of 3-4 Ian apart. New data shows half the flashes are some 9 Jan apart. The National Severe Storms Laboratory report concludes with a recommendation that: "It appears the safety rules need to be modified to increase the distance ::from a previous flash which can be considered to be relatively safe, to at least 10 to 13 Ian (6 to 8 miles). In the past, 3 to 5 km (2-3 miles) was as used in lightning safety education." Source: Separation Between Successive Lightning Flashes in Different Storms Systems: 1998, Lopez & Holle, from Proceedings 1998 Intl Lightning Detection Conference, Tucson AZ, November 1998. 3. A mGH PERCENTAGE OF LIGHTNING FLASHES ARE FORKED.

Many cloud-to-ground lightning flashes have forked or multiple attachment points to earth. Tests carried out in both the USA and Japan verify this in at least half of negative flashes and more than seventy percent of positive flashes have forked characteristics. Many lightning detectors cannot acquire accurate information about these multiple ground lightning attachments. Source: Termination ofMultiple Stroke Flashes Observed by Electro- Magnetic Field: 1998, Ishii, et al. Proceedings 1998 International Lightning Protection Conference, Birmingham UI< Sept. 1998. 4. LIGHTNING CAN SPREAD OUT SOME 60 FT. UPON STRIKING EARTH'S SURFACE.

Radial horizontal arcing has been measured at least 20 m. :from the point where lightning enters the earth. DePending upon soils characteristics, safe conditions for people and equipment near lightning tennination points (ground rods) may need to be re-evaluated. Source: 1993 Triggered Lightning Test Program: Environments Within 20 meters of the Lightning Channel and Small Are Temporary Protection Concepts: 1993, SAND94-0311, Sandia National Laboratory, Albuquerque NM

THE LIGHTNING PROTECTION PROCESS, per NASA TM.. 1999...209734

Develop Lightning Protection Requirements

Locate Strike Points Determine External Current Paths by Test and Analysis

Yes

Develop Design Requirements

Develop Lightning Model

Implement Design for Protection From Direct and Indirect Effects

Equipment Design

Determine Susceptibility of Each Piece of Equipment

Determine Internal Environment (Threat levels to EQui ment

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Lightning Protection Adequate

19

HOW TO GET TO LIGHTNING SAFETY?

FOR PERSONNEL PROTECTION: 1.

LIGHTNING HAZARD ANALYSIS

2.

LIGHTING SAFETY POLICY

3.

LIGHTNING DETECTION & ACTIVITY SUSPENSION

4.

POSTED WARNING SIGNAGE

FOR FACILITY PROTECTION: 1.

AIR TERMINALS AND CONDUCTORS TO GROUND

2.

GROUNDING DESIGNS FOR LOW IMPEDANCE ACCORDING TO LOCAL SITE REQUIREMENTS.

3.

BONDING ALL EXTERIOR AND INTERIOR CONDUCTORS.

4.

SURGE PROTECTION TO AC POWER, SIGNAL AND DATA LINES.

5.

INSPECTION, MAINTENANCE AND TESTING.

National Lightning safety Institute 891 N. fioover Ave Louisville CO 80027

MATRIX OF LIGHTNING PROTECTION SUB-SYSTEMS Apply these sub-systems as appropriate (YES or N/A) to specific facilities or structures.

DIRECT STRIKE

INDIRECT STRIKE

EXTERIOR LOCATION

INTERIOR LOCATION

PEOPLE SAFETY

STRUCTURE SAFETY

AIR TERMINALS

YES

N/A

YES

N/A

N/A

YES

DOWN· CONDUCTORS

YES

N/A

YES

YES

N/A

YES

BONDING

YES

YES

YES

YES

YES

YES

GROUNDING

YES

YES

YES

YES

YES

YES

SHIELDING

YES

YES

YES

YES

YES

YES

SURGE PROTECTION

YES

YES

YES

YES

YES

YES

DETECTION

YES

. YES

YES

YES

YES

YES

POLICIES & PROCEDURES

YES

YES

N/A

N/A

YES

YES

21

LIGHTNING MITIGATION GUIDELINE The premise of this Guideline is that lightning will strike our facility. Lightning cannot be "stopped" or prevented, and in this sense absolute protection against it is impossible. A pro-active, systematic approach of preparedness is the best defense against lightning consequences.

1. Strike Probability Study. -Historic 5 year lightning data from archives. -Future strike estimates via simulation.

2. Site Inspection. - Identify IlSafeiNot Safe" personnel zones. - Identify potential coupling (DC, capacitive and inductive) to critical and non-critical areas.

3. Lightning Detection & Personnel Notification. -Define criteria for cessation of activities. -Acquire appropriate lightning detection and signaling devices. -Integrate decisions into overall Safety Plan.

4. Comprehensive Employee Safety Education. -Provide all affected personnel with defensive - preparedness information.

5. Grounding Analysis. -Complete e/ectrogeo/ogical model. -Review merits of various grounding options. -Ensure grounds meet target resistance.

6. Air Terminal/Downconductor/Bonding/Shielding. -Evaluate existing system. -Consider design options. -Select & install appropriate devices.

7. Transient Voltage Surge Suppression. -Study all conductive penetrations. -Identify vulnerabilities. Define protective zones. -Install power and signal protection devices.

8. Implement Recommendations. -Verify correct installation of all devices. -Certify site as having adopted "best available technology" for lightning safety. -Establish site inspection and maintenance programs. ©2006 National Lightning Safety Institute (NLSI), Tel. 303-666-8817.

23

INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter Two

RIS'K ASSESSMENT

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Chapter Two Overview Risk analysis is interesting. To quote Einstein: "Statistics are useful, so long as you don't believe them." The risk of lightning to key structures is low, maybe 1:1,000,000. But the consequences can be very high. Some examples: A cellular phone site is taken off line and revenues cease; A security system fails and critical data is stolen; A E911 call center drops off line and there is no response to emergency calls; AC power is interrupted to a process control operation resulting in wasted product; A data processing center suffers corrupted "One's and Zero's" due to transients causing power anomalies. Assessing probabilities with lightning issues is a form of gambling. Pay the mitigation costs up front, or pay them afterwards. Lightning doesn't care.

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25

DETERMINING THE PROBABILITY OF LIGHTNING STRIKING A FACILITY By R.T. Hasbrouck, PE

National lightning Safety Institute Revised 4/18/04 One objective of a facility lightning hazard mitigation study is to determine the likelihood of its being struck by lightning. In this article, actual site-specific lightning strike data Is used to calculate probability.

Estimating Probability The probablUty of lightning striking a particular object situated on the earth (ground) is found by multiplying the object's lightning-attractive area by the local ground-flash density (lightning strikes to ground per km2 per year). The following example considers a low structure surrounded by 12 tall, grounded metal light poles.

caveats: It must be understood that calculations used for determining strike probability are based upon empirical relationships, generally accepted by the research community as reasonably representing the lightning phenomenon. The method presented here provides a reasonable estimate but should not be considered the "final word." Other, more complicated geometric methods can be used but, considering the capricious nature of lightning, it is unlikely they would provide significantly Improved results.

A complete cloud-to-ground lightning event, referred to as a flash, consists of one or more return strokes. Return strokes are hlgh-peak-amplltude (tens to hundreds of thousands of amperes) current pulses, each lasting for a few hundred microseconds. Analysis of a large quantity of lightning flash data shows the average number of strokes (multiplicity) per negative (the most common type of lightning) flash to be between three and four. Approximately 25% of all negative flashes- also exhibit several hundred amperes of continuing interval lasting hundreds of milliseconds following at least one return stroke. In a given current during flash, consecutive return strokes- may strike the ground Within several meters of each other, or as far apart as eight Ian. Analysis ~f data (as reported by Dr. Phil Krider) Indicates that flashes -exhibit- a "random walk," having a mean interstroke distance of 1.8 km. Ground-flash density data used In this paper is based upon the first stroke of each flash-detected by the National Ughtnlng Detection Network (see below)-regardless of stroke amplitude or flash multiplicity. The author is unaware of any strike probablUty estimates that take Into account the area encompassed by a multi-stroke flash and/or the current-amplitude distribution of stroke~ In the flash. Anally, note that the statistically less frequent positive lightning flash usually consists of a single stroke having average and maximum peak amplitudes that are significantly higher than for negative lightning. It Is accompanied by continuing current and has a total duration as long as one to two seconds.

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Cumulative Probability Lightning Attractive Area If the earth's surface beneath a storm doud were perfectly flat, lightning could be expected to strike any

of5

26 point on the earth with equal probability. For example, if an area of 0.1 krif experiences a ground-flash density of one flash per km 2 per year, the probability of its being struck is 0.1 In any given year (a return frequency of 10 years per flash). However, a conductive object that is taller than the surrounding area exhibits a lightning attractive area greater than the ground surface area it occupies. The probability of Its being struck Is a function of its ground surface area, height, and the striking distance between the tip of the downward-moving stepped leader and the object (Ref. 1). For negative lightning, the stepped leader Is a negatively charged channel that travels In discrete jumps from cloud to Earth, Striking distance, the stepped leaders final jump to the conductive object, varies with the amount of charge carried by the channel. (Note: For the sake of simplicity, striking distance calculations don't take Into account upward-moving, positively-charged streamers. These streamers emanate from conductive objects under the influence of the stepped leaders strong electric field-much as hairs rise up toward a statically charged comb held over one's head.) Since the magnitude of this charge also determines return-stroke peak-current amplitude, greater striking distances are associated with larger amplitude return strokes, i.e., they jump farther to reach the object (Ref. 2). Thus, for a given ground surface area and object height, the maximum lightning-attractive area will be associated with the stroke having the largest peak amplitude.

Ground-Flash Density In the United States, actual cloud-to.-ground lightning strike data Is detected and archived by the National Lightning Detection Network (NLDN), Global Atmospherics, Inc. (GAl-Tucson, AZ) analyzes the data and produces ground-flash density maps for user-specified areas. The map used for this study was based upon 29,207 negative and positive flashes-five years (1990-1994) of site-specific data-detected In an area of 1.3 x 104f km 2 • The average overall flash density was 0.45 flashes/km2/yr, ranging from < 0.25 to < 0.5 flashes/km 2/yr within a 4-km radius of the fadllty. The following should be taken Into account when considering the GAl data. NLDN detection efficiency (DE)-I.e., the percentage of all lightning flashes that were detected and recorded-improved over the five-year period during which our data was acquired. Initially, DE was reported as 65-700/0; the currently (1995) stated value is 85-90% (for Ipk > 5 kA). Assuming a five-year DE average of 75% (considered by GAl to be a reasonable estimate) gives a corrected facility flash-density range of < 0.33 to < 0.67. The median value of 0.5 flashes/km 2/yr was used for our probability calculations. Two points regarding this value of ground-flash density should be kept In mind. It Is based upon only five years (1990-95) of actual NLDN data-the network was quite new at the time this study was carried out. Analysis of data collected since that time probably would indicate a different value, although It seems doubtful that it would differ by very much. Significantly different values of ground-flash density are found in other parts of the country. However, even locations relatively dose to the area studied could have notably different values because of variations In topography. That Is one of the benefits of NLDN data, the ability to Identify differences between wide-area flash-density estimates, and site-speclflc values.

Return-Stroke Peak-Current Amplitude Over a number of decades, researchers have measured and recorded a variety of lightning parameters, with much of the data resulting from strikes to tall, instrumented steel towers. Along with current rate of rise and total charge transfer, peak return-stroke current Is considered to be one of lightning's most significant threat parameters. For the generally accepted frequency distribution of peak currents for negative lightning, the first-percentile value, 200 leA (I.e., 990/0 of all lightning Is of lower amplitude), Is generally considered to constitute a severe negative stroke. Although the NLDN detection efficiency Is less than 100%, GAl reports that it Is low-peak-current (i.e., < 5 leA) events that are missed, Thus, had all flashes been detected, the distribution of peak-current amplitudes would be expected to show a somewhat lower average value.

Facility Lightning Attractive Area

2of5

-.

t1I t1I

-.-. til til til

-----------I)

@ @

fJ ~ @ ~

f f

, f

," f f f

27

Since the twelve 32-meter-tall perimeter light poles for our study appeared to be likely lightning strike points-at least for large-amplitude flashes-they were used In calculating the facility's lightning-attractive area. For the sake of simplicity, structure height was not included in our equation. It is reasonable to expect that some low-amplitude strokes will bypass the poles and attach to the structure.

As previously discussed, attractive area must take into account the peak amplitude of return-stroke current. Thus, an attractive area must be calculated for each current amplitude. The following method for dealing with the distribution of return-stroke currents Is attributed to the late J. Stahmann of Boeing/Kennedy Space center (Ref. 3). Stahmann assigned return-stroke peak currents from a large body of available data to declles-i.e., 10% of the total number of flashes being considered were placed Into each of ten bins. The mean peak current per decile was then calculated.

Facility Strike Probability Stahmann's mean peak-current per decile values were used to find the per-decile attractive area. The effect of the tall light poles on attractive area CAe) can be seen In Table 1. Although the surface area encompassed by the poles is 45*103 m 2, the lightning-attractive area is 77*103 m 2 for a 6-kA stroke and 171*103 m 2 for a 112-kA stroke. The product of attractive area times ground-flash density prOVided per-decile probability, the sum of which gave a cumulative probability. The reciprocal of cumulative probability is the mean return period (average strike frequency). Our study determined that some point of the facility will be struck by lightning-of some amplitude-approximately once every 17 years.

Table 1. Cumulative Probability of Strike to Fadllty

Jpk

D.

r

AA

(leA)

(m)

(m)

(m 2)

1

6

33

33

76,764

3.8E-03

2

13

S3

48

93,489

4.7E-03

Decile

Po

..

.18

..65

56

101,496

s.1E-03

4

23

76

62

108,624

5.4E-03

5

28

88

68

115,399

s.8E-03

6

35

101

74

122,391

6.1E-03 :

7

ofS

45

118

81

130,658

R

(yr/fI)

#

3.

Pc

6.5E-03

28

S

57

138

89

140,196 7.0E-03

9

77

168

99

153,061

112

215

113

171,380 8.6E-03

I 7.6E-03

f

f 10

6E·02

17

«

t Area enclosed by light poles: I = 312 m, w h == height of poles above ground level Ipk

r

=144 m (I x w = 44,928)

= 32

= average peak return-stroke current per decile

Os == lightning striking distance

=10 x Ipko. 65

Fg = ground flash density

-m

«

-leA

~

-m

=radius of light pole's attractive area = (2 x Os x h - h2)o.5

M == attractive area/decile = (I

t t

-m

+ 2r) x (w + 2r) - 10 x [(4 • ")/4] x r2

=0.5 {using GAl flash density analvsls}

=cumulative probability =I

t

PO

R == mea,n return period (i.e., average strike frequency)

= 1/PC

- 'years/flash

Conclusion Reasonable strike probability estimates can be made using site-spedflc, ground-flash density values that are based upon actual lightning data. Strike estimates are Interesting, and although their results provide an Indication of lightning strike return frequency, they should not be considered as absolutes. Perhaps their most useful funetlon Is to permit determination of the relative effects of changes made to a facility. Examples of such changes are: increased lightning-attractive area-either by extending the fadlity's surface dimensions and/or height (adding a vent stack or tower); plating an Identical fadllty In a location having a significantly different ground-flash density.

References 1. Golde, R.H., "Proteetlon of Structures Against Lightning," Proceedings of the Institute of Electrical Engineers, Vol. 115, No. 10, pp. 1523-1529, 1968. 2. Golde, R.H., "The Ughtning Conductor," In Golde, Lightning, Vol. 2, p. 560, Academic Press, london, 1977 (the striking distance equation attributed to E.R. love). 3. Stahmann, J.R., "Launch Pad Lightning Protection Enhancement by Induced Streamers," Boeing Aerospace Operations, Kennedy Space Center, Rorlda, september 1968.

of5

•• ~

PO == strike probabiJity/dedle == AA x (0.1 x Fg) x 10-6 PC

••

•• •• •• •• •• • fi fi

•• •• •• •

•" •..

29

ANALYSIS OF NEED FOR PROTECTION With permission ftom Singapore Standards and Productivity Board Reproduced from Singapore Standmd CP33: 1996 Lightning Protection

2.1

GENERAL

Before proceeding with the detailed design of a lightning protection system, the following essential steps should be taken :

2.2

(a)

It should be decided whether or not the structure needs protection and, if it does what the special requirements are (see Clause 2.2 and Section 3).

(b)

A close liaison should be ensured between the architect, the builder, the lightning protection system engineer and the appropriate authorities.

(c)

The procedures for testing, commissioning and future maintenance should be agreed.

NEED FOR PROTECTION

2.2.1 General. Structures with inherent explosive risks, e.g. explosives factories, stores and dumps and fuel tanks usuaJly need the highest possible class of lightning protection system and recommendations for protecting such structures are given In Section 5.

For all other structures, the standard of protection recommended in the remainder of this Code is applicable and the only question remaining is whether protection is necessary or not. In many cases, the need for protection may be self--evident. for example: (a)

Where large numbers of people congregate;

(b)

Where essential public services are concerned;

. (c)

·Where the area Is one In which lightning Is prevalent;

(d)

.Wh~ there are very tall or isolated·Structures;·

(e)

Where there are structures of historic or cultural importance;

(f)

Where there are structures containing explosive or flammable

~ntents.

However, there are many cases for which it is not so easy to make a decision. In these areas, reference should be made to 2.2.2 to 2.2.8 where the various factors affecting the risk of being struck and the consequential effects of a strike are discussed. However, some factors cannot be asseSSed ·and ·these may override all other considerations. For example, a desire that there should be no avoidable risk to life or that the occupants of a bUilding should always feet safe may decide the question in favour of protection, even though it would normally be accepted that there was no need. No gUidance can be given in such matters but an assessment can. _ be made taking account of the-exposure risk· (that is. the· risk of the structure being· struck) and the following factors: (a)

Use to which the structure is put;

(b)

Nature of its construction;

31

CP33: 1996

2.2.3 Risks Associated With Everyday Uving. To help in viewing the risk from lightning in the context of the risks associated with everyday IMng, .Table 2.1 gives some figures based on 5S 6651 : 1992. The risk of death or injury due to accidents is a condition of lMng and many human activities imply a judgement that the benefits outweigh the related risks. Table 2.1 is intended simply to give an appreciation of the scale of risk associated with different activities. Generally, risks greater than 10.3 (1 in 1000) per year are considered unacceptable. With risks of 10'" (1 in 10000) per year, it will be normal for public money to be spent to try to eliminate the causes or mitigate the effects. Risks less than 10.5 (1 in 100 000) are generally considered acceptable, although public money may still be spent on educational campaign designed to reduce those risks Which are regarded as avoidable. 2.2.4 Suggested Acceptable Risk. On the basis of Subclause 2.2.3, the acceptable risk figure has been taken as 10-5 per year,.l.e. 1 In 100 000 per year.

.

"

Table 2.1. Comparative probability of death for an individual per exposure (order of magnitude only)

Activity

Risk 1 in 400

year of

(2.5 x 10-3)

Smoking (10 cigarettes per day)

1 in 2000

(5 x 10"')

All accidents

1 in 8000

(1.3 x 10' 4)

Traffic accidents

1 in 20 000

(5 x 10~

Leukaemia from natural causes

1 In 30000

(3.3 x 1005)

Work in industry, drowning

1 in 100 000

(1 x 10'

Poisoning

1 in 500 000

(2 x 10~

Natural disasters

1 in 1 000 000

(1 x 10-,

Rock climbing for 90 s..,- d~ng 50 mites by road*

1 in 2 000 000

7 )

(5 X 10.

Being struck by lightning

* These risks are conventionally expressed In this form rather than In terms of exposure for a year. NOTE. The source 01 this table Is as 6651 : 1992

2.2.5 Overall Assessment Of Risk. Having established the value of P, the probable number of strikes to the structure per year (see Subclause 2.2.2), the next step is to apply the weighting factors'. as given in Tables 2.2 to 2.6. This Is done by multiplying P by the appropriate factors to determine " whether the result, the overan risk factor, exceeds the acceptable risk of Po = 10-5 per year. 2.2.6 Weighting Factors. In Tables 2.2 to 2.6, the weighting factor values are given under the headings A to E"and denote a relative degree of importance or risk in each case. Tables 2.2 to 2.6 are mostly self-explanatory.

...... .... ....."". .-.. .... .-..-..-.. •.... • Q

30

CP33: 1996

(c)

Value of its contents or consequential effects;

(d)

The location of the structure;

(e)

The height of the structure (in the case of the composite structures, the overall height).

2.2.2 Estimation Of Exposure Risk. The probable number of srikes to the structure per year is the product of the 'lightning flash density' and the 'effective collection area' of the structure. The lightning flash density, Ng is the number of flashes to ground per km2 per year. Values of Ng vary from place to place. in Singapore the best estimate for the average annual density can be taken to be 12.6 flashes to ground per km2 per year. The effective collection area of a structure is the area of the plan of the structure extended in all directions to take account of its height. The edge of the effective collection area is displaced from the edge of the structure by an amount equal to the height of the structure at that point. Hence. for a simple rectangular bullding of length L, width Wand height H On m), the collection area has length (L + 2 H) m and width (W + 2H)m with four rounded corners formed by quarter circles of radius H (in m). This gives a collection area, Ac frn m', of: .

Ac == LW + 2LH + 2WH + .~ The probable number of strikes to the structure per year, P, is as follows:

It should first be decided whether this risk P is acceptable or whether some measure of protection is thought necessary. This is shown in Figure 2.1.

;'

~----

/

-.-.

---

"-

I

'\

\

f

I

I

t

!

Hm

I I

,

!Wm I

--±. I

I

L-----------~1

I

'7 I. ~

Lm

--- --

-l

.

I

Boundary of

,----. collec tlon area /

/ --_.-- ......

Figure 2.1 Plan of collection area

.-

•.,., ., .•.,, .,"., ., "•" ••

CP33: 1996

Table 2.4 gives the weighting factor for contents or consequential effects. The effect of the value of the contents of a structure Is clear, the term 'consequential effects' Is Intended to cover not only material risks to goods and property but also such aspects as the disruption of essential services of all kinds, particularly In hospitals. The risk to life Is generally very small but, If a bUilding is struck, fire or panic can naturally result. All possible steps should therefore be taken to reduce these effects, especially among children, the old and the sick. For multiple use buRdlngs, the value of weighting factor A applicable to the most severe use should be used.

Table 2.2. Weighting factor A (use of structure)

Use to which str.ucture Is put

Value of factor A

Houses and other buirdlngs of comparable size

0.3

Houses and other buildings of comparable size with outside aerial

0.7

Factories, workshops and laboratories

1.0

Office blocks, hotels. blocks of flats and other residential buildings other than those InclUded below

1.2

Places of assembly, e.g., churches, halls, theatres, museums. eXhibitions, department stores, post offices, stations. airports, and stadium structures

1.3

Schools, hospitals, children's and other homes

1.7

Table 2.3 Weighting factor B (type of co~stru~ion)

Type of construction

Value of factor B

Reinforced concrete or steel frame with metallic roof

0.4

Membrane structure with metallic frames

0.8

Reinforced concrete or steel frame with non-metallic roof

1.0

Timber or masonry with non-metallic roof

1.4

Timber or masonry with metallic roof

1.7

Any building with a thatched roof

2.0

NOTE. A structure of exposed metal which is electrically continuous down to ground level is excluded from the table as it requires no lightning proteCtion, beyond adequate earthing arrangements.

33

CP33: 1996

Table 2.4 Weighting factor C (contents or consequential effects)

Contents or consequential effects

Value of factor C

Ordinary domestic or office buildings, factories and workshops not containing valuable or specially susceptible contents

0.3

Industrial and agricultural bundings with specially susceptible* contents

0.8

Power stations, gas Installations, telephone exchange, radio stations

1.0

Key Industrial plants, ancient monuments and historic buildings, museums, art galleries or other buildings with specially valuable contents

1.3

Schools, hospitals. children's and other homes, places of assembly

1.7

* This means specially valuable plant or materials vulnerable to fire or the result of fire.

Table 2.5 Weighting factor 0 (degree of isolation)

Degree of isolation

Value of factor 0

Structure located in a large area of structures or trees of the same or greater height, e.g. in a large town or forest

0.4

Structure located in an area with few other structures or trees of similar height

1.0

Structures completely isolated or exceeding at least twice the height of surrounding structures or trees

2.0

Table 2.6 Weighting factor E (type of terrain)

Type

of terrain

. Value of factor E

Aat land at any level

0.3 .

On hillside

1.0

On hilltop

1.3

..

2.2.7 Interpretation Of Overall Risk Factor. The risk factor method given in this Code Is Intended to give guidance on what can, in some cases. be a difficult problem. If the result obtained is considerably less ·than· 10-5 (1 in 100 000) then, in the absence of. other overriding considerations. protection does not appear necessary; if the result is greater than 10.5, say for example 10'" (1 in 10000), then sound reasons would be needed to support a decision not to give protection. When it is thought that the consequential effects will be small and that the effect of a lightning strike will most probably be merely slight damage to the fabric of the structure. it may be economic not to Incur the cost of protection but·to accept the risk. Even though this decision is .made, it is suggested that the calculatIon is stm worthwhile as givIng some idea of the magnitUde of the risk being taken'"

CP33: 1996

Structures are so varied that any method of assessment may lead to anomalies and those who have to decide on protection have to exercise judgement. For example, a steel framed buDding may be found to have a low risk factor but, as the addition of an air tennlnation and earthing system will give greatly improved protection, the cost of providing this may be consIdered worthwhile.

A low risk factor may result for chimneys made of brick or concrete. However, where chimneys are free-standing or where they project for more than 4.5 m above the adjoining structure, they will require protection regardless of the factor. Such chimneys are, therefore, not covered by the method . of assessment. Similarly, structures containing explosives or flammable substances are sUbject to additional consideration (see Section 5). Results of calculations for different structures are given in Table 2.7 and a specific case is worked through in Subclause 2.2.8. NOTE.

Table 2.7 should be read in conjunction with Figure 2.2.

2.2.8 Sample Calculation Of Overall Risk Factor. A hospital is 10 m high and covers an area of 70 m x 12 m. The hospital' is located on flat land and isolated from other structures. The construction is of brick and concrete with a non·metallic roof.

To determine whether or not lightning protection is needed. the overall risk factor is calculated. as follows: (a)

Number of flashes per km2 per year. The value for Ng is 12.6 flashes per km2 per year.

(b)

Collection area. Using the first equation in 2.2.2 the collection area, ~ in m2, is given by: Ae = (70 x 12) + 2(70 x 10) + 2(12 x 10)

A.c

(c)

+ (~x 100)

= 840 + 1400 + 240 + 314

Probability of being struck. Using the second equation in 2.2.2 the probable number of strikes per year, P. is given by:

P

= Ae x N9 x 100G

P = 2794 m 2 x 12.6 x 100G P (d)

= 3.5 x 10.2 approximately

Applying the weighting factors. The following weighting factors apply: factor A factor B factor C factor 0 factor E

= 1.7 = 1.0 = 1.7 = 2.0 = 0.3

The overall multiplying factor

=A x B x C x Dx E =

1.7

Therefore, the overall risk factor = 1.7 x 3.5 x 10.2 = 5.9510'2. The conclusion is, therefore. that protection is necessary.

35

CP33: 1996

2.3

NEED FOR PERSONAL PROTECTION

A hazard to persons exists dUring a thunderstorm. Each year. a number of persons are struck by lightning part.iculariy when outdoors in an open space such as an exposed location on a golf course, or when out on the water. Other receive electric shocks attributable to lightning when Indoors. In built-up areas protection is frequently provided by nearby buftdlngs, trees. power lines or street lighting poles. Persons within a substantial structure are normally protected from direct strikes. but may be exposed to a hazard from conductive materials entering the structure (e.g. power. telephone, or TV antenna wires) or from conductive objects within the structure which may attain different potentials. Measures for the protection of persons within buildings or structures are set out in Section 7. Ughtning strikes direct to a person or close by may cause death or serious injury. A person touching or close to an object struck by lightning may be affected by a side flash. or receive a shock due to step, touch or transferred potentials, as described in Appendix A. When moderate to loud thunder is heard, persons out of doors shOUld avoid exposed locations and should seek shelter or protection in accordance with the gUidance for personal safety provided in Appendix G, particutariy if thunder follows within 15 s of a lightning flash (corresponding to a distance of less than 5 km). 2.4

NEED FOR PROTECTION OF PERSONS AND EQUIPMENT WITHIN BUILDINGS

As explained in Clause 2.3, persons and equipment within buildings can be at risk from lightning currents and associated voltages which may be conducted Into the b\Jildlng as a consequence of a lightning strike to the building or associated services. Some equipment (e.g. electronic equipment, including computers) is especially susceptible to damage from overvoltages transferred from external connections caused by lightning and such damage may occur even when the lightning strike is remote from the building. e.g. from a surge conducted into the building via the power and telecommunication cables. Measures may therefore need to be taken to protect persons and equipment within buildings and Section Seven provides further. advice on this SUbJect. Tt:t~~~sures recommended in· Section . Seven can be implemented even when a lightning protection system for the building structure has not beerl. provided. . The decision as to Whether to provide protection specifically directed to equipment will depend on the value placed on that equipment and on the cost and inconvenience which might resuit from the equipment being out of service for an extended period. The risk factor determined from Clause 2.2 will provide guidance on the likelihood of a building being subject to a lightning strike with consequent risk of damage occurring to equipment within the bUilding. However. since damage to equipment can result from lightning strikes to adjacent properties or to power or signal lines some distance away. the Index value may not be a sufficient indicator of the risk. The incidence of damage occurring to similar equipment within bundings in the vicinity may provide . . a better guide to the need to protect.

'lI!1II1!

36

"

"•" •.-.

CP33: 1996

Reference (a I

{bl

General arrangement

Collection area and method of calculation

R15

1S

, ... ----..,..~ l I \ ---!I I :

I-

i~

~, I

..(

'--t-~'C. r'",._--t-.' 14 ....JQ...;

8

f,

R9 yoV ,

6

I ~9

e

j~6

I "'-1_-

. i.lJ

R6

r------' F W----lRb 60

r-

R6

,

-'

I

4

" ~ (

A e .. 7 X 8 + 216 X 71 + IIS 2 + + 10 tapprox.l (or areas in black A c .. 405 m'

~~~6

1b~~

(el

"-R1C.

ti"'o--~

R6--.

j"

....

A c .. n 14 2 + 2(14 x 30) A e .. 1456 m 2

" - - - - c;:--"[

(~~ 114

~

.,-t

~:: 21 ...... _--~~ 21 40 '21" I....I.. _1_ .., '--R21 I

10

j

- -

",

b

.....•.

A c • 15 X 40 + 2121 X 401 + +2(21 X 151 + ,,21 2 A c • 4296 m1

,

I- - -, .

.

W

I

..,--- -r..---. .. 2' ~-J [-'~,--tl~

R21---,.

21

t

ldl

I

fIlA

r15~-- ----t SO 15 K- R15

i--~ f " Ie)

~i-

L._ I

fIlA

·14 X 50 -t 2115 x 50) + +2(15X 14)+1115' A c " 3327 m 2 A~

1S 14 1S

""l

: Ll r- 6

SO

:

,

~.

6..J

6

6

:

25

I

2S

.. ,

A c • 25 X 60 + 25 X 30 + 6 X 60 + + 6 X 50 + 6 X 25 + 6 x 25 + + 6 X 30 + 6 X 24 + 5/411 6' A c " 3675 m2

1

,./

1--:to -j :tn 6

If)

(~

R'3~ r',

..t 3

-~t3.

+ 2(9} +

A~=9+2(9)

Ac

= 73.3

m2

:.i

All dimensions are in metres. NOTE. This fi9ure should be used in conjunction wilk lab Ie V

Figure 2.2 Details of structures and collection areas

-"

..

113

2

Table 2.7 Examples of calculations for evaluating the need for protection

1

2

Ref. in Figure 2.2

Description of structure

4

3

6

7

8

9

10

Weighting factors

RIsk of being struok, P

;

Collection area, Ate

(a)

5

Rash density, Ng

Acx Ng

X

B Type of construction (Table 2.3)

C

0

E

Use of structure (Table 2.2)

Contents or consequential effects (Table 2.4)

Degree of Isolation (Table 2.5)

Type of country (Table 2.6)

A

P= 10-8

11

12

13

Overall multiplying factor (prodUcts of columns 6 to 10)

Overall risk factor (product of columns 5 to 11)

Recommendation

3327

12.6

41.9 x 10'"

1.2

1.0

0.3

0.4

0.3

0.043

1.8 x 10-3

Protection recommended

An office building, built with reInforced concrete and Is havIng nonmetallic roof

4296

12.6

54.1 x 10-3

1.2

1.0

0.3

0.4

0.3

0.043

2.3 x 10-3

ProtectIon recommended

A school, built with reinforced concrete and brick and Is having non~ metallic roof

1456

1.0

1.7

0.4

0.3

0.35

6.4 x 10-3

Protection recommended

An apartment. built with reinforced concrete and brick and Is having nonmetallic roof

(b)

(c)

. 12.6

18.3x 10'"

1.7

Table 2.7 Examples of calculatIons for evaluating the need for protectIon

1

2

Ref. in Figure 2.2

Description of structure

4

3

5

6

7

8 Weighting factors

Risk of beIng struck, P

Collection area, "c

Aash density,

p=

Ng

Ae x Ng X 10.8

A two storey detached bungalow, built with reinforced concrete and brick and is having non· metallic roof

405

12.6

5.1 x 10.3

(e)

A factory, built with reInforced concrete and steel framed encased and is having metallic roof

3675

12.6

46.3 x 10'3

1.2

0.4

0.3

(f)

A security guard post of 3mx3mx 3m, built with reinforced concrete and brick and Is having metallic roof

73.3 ,

12.6

9.24 x 10'4

0.3

0.4

0.3

(d)

10

9

B

e

11

12

13

Overall multiplying factor (products of columns 6 to 10)

Overall risk factor (product of columns 5 to 11)

Recommendation

A Use of structure (Table 2.2)

Type of construction (Table 2.3)

C Contents or consequential effects {Table 2.4}

0 Degree of Isolation (Table 2.5)

Type of country (Table 2.6)

0.3

1.7

0.3

0.4

-0.3

0.02

1.02 x 10'4

Protection recommended

0.4

0.3

0.017

7.9)( 10.3

Protection recommended

0.4

0.3

0.00432

4 x 10.8

Protection not required

.

NOTE. The risk of being struck, P (column 5), is multiplied by the product of the weighting factors (columns 6 to 10) to yield an overall risk factor (column 12). This should be s compared with the acceptable risk (10' ) for guidance on whether or not to protect. Risks less than 10.5 do not generally require protection; risk greater than 10.4 require protection; for risks between 10'5 and 10-4 protection is recommended (see Subclause 2.2.3 to 2.2.8)

Uke/ihood

Task:

I

Risk Analysis for Lightning Safe.ty - Example: Mining Activities

u

E (OS u

!!

rz: or:

0 I::

til)

National Lightning Safety Institute

Analysis by: Approved by:

";';

-. ..s

Date: Date:

Job Steps

Potential Hazards

A - Certain B - Likely C - Possible D - Unlikely E - Rare

Level of Risk

H M L L L

l.':

C>

"0 0

.

...

0

"(;j>

~,

::?Z

::?Z,

N

M

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H H M L L

R H H M M

:.E c.

15

S

a.


E B E B B· B H B H H

Control Measure

Mine control receives lightning detector alert I warning Unable to·make c~ntact, radio not working

L(Ct)

Geologist advised ofneed to notify drill crew. Ensure base station radio. kept in working order

Delay in contacting drill crew

H(C3)

Drill crew to monitor weather conditions for themselves at all times

Accident on rig when distracted by radio

L(D2)

Ensure rig safe before moving to answer radio

Slip I trip when moving to answer radio (particularly in. dark)

L(D2)

Ensure ongoing good housekeeping of rig site

Rig without base station not informed of alert

H(C3)

Drill crew with base station to notify other crew and maintain contact

Drill crew acts on alert

Not shutting down rig properly

L (01)

Ensure rig crew knowledgeable on emergency shut down procedures

Electrical activity

Lightning strike of rig crew

E(D5)

Drill crew to be in safe location during electrical activity

Drill crew receives all clear

No radio contact

L(Cl) .

Keep hand held radio charged and in working order and monitor channel 2 for all clear

Electrical activity not finished in vicinity of rig

H (C3)

Drill crew to monitor electrical activity in vicinity of rig

Not fonowing correct start up procedures

L(D!)

Ensure drill crew knowledgeable on start up procedures

Further electrical activity in area

H (C3)

Drill crew to continue monitoring weather conditions around the rig and keep radio on channel 2

Mine control contacts drill crew

Drill crew receives alert .

-_.-

Resume drilling activities

SHORT VERSION OF RISK ASSESSMENT (PERNLSI)

1. Lightning Behavior is not fully understood. In another 100 years, science may roll back the "Unknown" to the "Known." Today we can only agree that it is arbitrary, capricious, random, stochastic and unpredictable. 2. From a perspective of statistical probability the likelihood of lightning striking our facility or structure is remote. Perhaps one-in-a-million? 3. If lightning did strike our operations, damage from a lightning strike is calculable. Consequences range from "mild" to "catastrophic."

4. Our options are: 4.1 Do Nothing. Run with the Odds. Take our Chances. 4.2 Do Something. Get some information. Perform a Safety Assessment. Install defenses for people and for the facility. 5. Lightning doesn't care what we do.

41

INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter Three

THE GROUNDING AND BONDING IMPERATIVE

42

Chapter Three Overview GrOlUlCling (aka Earthing) means using a low resistance and conductive

Earth Electrode Subsystem (BES) to provide a safe destination for lightning's energy. A suitable BES employs volumetric efficiencies, not just 25 ohm or 10 ohm target resistance. BES designs are site-specific. Often times to just drive a few ground rods is an error of simplification. Bonding was recognized only recently as essential to good lightning protection. All metallic conductors, intended or otherwise, must be interconnected. Equalization of all potentials is mandated in the National Electrical Code. The US Air Force API 32-1065 says it all: "If you don't bond, your lightning protection system wont work:."

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43

DEFINITION OF TERMS USED IN GROUNDING by National Lightning Safety Institute (NLSI) www.lightnlngsafety.com

In order to promote a uniform understanding of grounding issues, the following Glossary is presented.

Concrete Encased Electrodes: The rebar in concrete can be an effective part of the grounding electrode subsystem. Since concrete is alkaline and hydroscopic (absorbent) in nature, this type ionizing and moist medium can create a large and effectiVe earth sink by using t"e foundation ground of any AFS. It is critical, however, that the rebar be connected to the primary ground electrode, buried ring electrode and/or other ground points in keeping with the concept of a wholly-unifonn and integrated single point ground for the entire facility. Concrete encased electrodes are recognized as a beneficial component of the earth electrode system. Current Magnitudes: Typical lightning current magnitudes peak in the 20-30kA range. However, magnitudes over 400kA have been recorded. Approximately 3% of magnitudes measure above 100kA. IEEE recommends that lightning protection engineers use 40kA as a design threshold for lightning protection sys~ems.

Deep Wells: Due the typical high cost of deep wells, other ~Iternatives first should be explored. These include: additional ground rods; connection of perimeter security fences to augment the ground grid; radial buried ground wires or ground ·straps .configured away from building corners;. treatment or augmentation of soils with artificial backfills; and low-cosldrip irrigation systems.

. .Driven' Rods: 'CoPPer conneCted to ground wires.

plated slee.l .rods are driven beloW grade and . .

Earth Electrode Subsystem: A network of electrically interconnected rods, plates, mats, or grids installed for the purpose of establishing a low resistance contact to earth. Equipotential Plane: A

grid, sheet, mass, or masses of conducting material which, wh,n bo~de~ together, o~rs a negligible.impedance. to current flow. Facility Ground System: The electrically interconnected systems of conductors and conductive elements that provide current paths to earth. The facility ground system includes the earth electrode subsystem, lightning

protection subsystem, signal reference subsystem, fault protection subsystem, as well as the bUilding structure, equipment racks, cabinets, conduits, junction boxes, raceways, duct work, pipes, towers, other antenna supports and other normally non-current carrying metallic elements.

Frequency and Skin Effect: Lightning Is a high frequency, high current pulse. At high frequencies and high currents, energy is transmitted along conductors with high skin effect Skin effect limits current flow to the extreme outer surfaces of conductors. Ground: Usually meaning the same as dirt or soil or earth. Ground Conductor Connections: Exothermic connections provide the IQwest inductance and the highest reliability of all connection alternatives. Even a low inductance path in a lightning circuit can invite large voltage gradients, which in turn may facilitate arcing to alternative paths. Gradients over 50kV/m are common in both air and earth situations. Such arcing, known as "side flash", may be the result of tight bends in above-grade wire conductors.

Ground Electrode: A conductor (usually buried) for the purpose of providing an electrical connection to ground.

Ground Ring: A ground wire of No.2 size encircling or surrounding a building, tower or other above-ground structure. Usually the ground ring should be installed to a minimum depth of 2.5 ft. and should consist of at least 20 ft. of bare copper conductor. It should be installed beyond the building drip line. Halo Grounded Ring: A grounded No.2 wire, installed around all four walls inside a small bUilding, at an elevation of approx. six inches below the ceiling. There are drops installed from the halo to the equipment cabinets and to waveguide ports, Interior cable trays etc. Halo rings serve as connector points to achieve ground references of interior metallic objects. These, in tum, are connected to the main ground bus bar.

Inductance and Voltage Poteotials: Lightning will follow the path of lowest inductance. The higher the frequency, the higher the inductive reactance value in calculating the total impedance of the circuit. Resistive values can be eliminated for all practical purposes in high frequency lightning conductor calculations for distances approximately 2000 feet or less. Impedance: The impedances of typical grounding electrode conductor wires linearly increase as a function of frequency.

45

Resistance of Electrode: Recommended NEC practice is to provide a resistance of less than 25 ohms for an earth ground. Local conditions will vary this target figure. Figures of 10 ohms or less are standard practice in several US Government standards. Volumetric efficiencies with large cross sectional areas means that impedance is more important than resistance. See IEEE 1100..1999, section 4.7 for more detailed information.

Shield: A housing, screen, or cover which substantially reduces the coupling of electric and electro-magnetic fields into or out of circuits or prevents the accidental contacts of objects or persons with parts or components operating at hazardous voltage levels.

Spark Gap: A short air space (dielectric) between two conductors. Types of Connectors: a} Mechanical, as in a threaded clamp; b) Pressure, as in a compression clamp; c) Thermal, as in CADWELO@, which results in a exothermic or molecular connection. Thermal connectors are said to be bonded, or electrically-joined.

46

FACTORS AFFECTING SOIL RESISTIVITY c) CHEMICAL COMPOSITION

A) PHYSICAL COMPosmON Different soil compositions give different avenge resistivities:

Certain minerals and salts can affect soil resistivity. Their levels can vary with time due to r.ainfa1l or flowing water.

Table 1 Table 3 EfTm orSoil Type on Rcslslivicy Soil TYl'"

Elfea orSalt on Rcsislivily For laIIdy loam. 15.2% moiuure

TypialllCliHivicy ohllH1l

Rcsisrivicy ohm·m

2· 2.7 ... ISO 60· 400 90 - 8000

Manhy Ground

loom ~nd Clay Ch.lk Sond l'co. Sondy Grovel

0.0 0.1 1.0

300· SOIl 1000 upwards

Rock

107.0 18.0

".6

5.0

10.0 20.0

B) MOlsnJRE Increased moisture content of the ground can rapidly decrease its resistivity.

1.3 1.0

Note that although the addition of salts can lower soil resistivity. they are not recommended due to corrosion and leaching. (See section on soil conditioning on page 16).

It is especially important to consider moisture content in areas of high seasonal variation in rain&ll. Wherever possible the earth electrode should be installed deep enough to reach the "water table" or "permanent moisture level".

Table 2

TopSoil

Sandy Loam

o

I,OOlhl()l

1.000 II 104

30

winter.

ElfcCl orT~mpmNrt on Resiuivity For sandy loam, IS,2% mouture

MoUture contenl'K • by weight

20

When the ground becomes frozen. its resistivity rises dr.amatically. An eanh that may be effective during temperate weather may become ineffective in

Table 4

EfTecl or Mobllne on Resilliv;ty

2.S 5 /0 15

D) 'l'EMPERATUllE

I\.nillivicy ohm·m

2500 1650 530

430

310 /20

105

/85

63

42

TcmpcRNf\! ·C F 20 10

o -5 .15

I\.csislivity ohm-rn

68 50

72 99 138

32 (ice) 23

300

14

790 3300

Please note that, if your soil tcmpcr.ature decreases from +20oC to • SoC, the resistivity increases more than ten times.

National LIgtltning safety Institute 891 N. Hoover Ave louisville CO 80027

47

RELATIVE ADVANTAGEIDISADVANTAGE OF PRINCIPAL TYPES OF EARTH ELECTRODE SYSTEMS Type

Advantages

Disadvantages

Vertical Rods

Simple design. Easy to install High impedance. Hard in good soils.Hardware readily to install in rocky soil. Step voltage on earth available. Can be extended to surface can be high reach the water table. under large fault currents or during a direct lightning strike.

Plates

Can achieve low resistance contact in limited area.

Most difficult to install. Should be installed vertically.

Horizontal Low impulse impedance. Bare Wires Good RF counterpoise (Radials) when laid in star pattern.

Subject to resistance fluctuations with soils drying. Not recommended with unstable soils.

Incidental Can achieve very low Electrodes resistance in certain (water pipes, applications. Ufer grounds, ... .buried tanks.)

Little or no control over future alternations. Must be employed with other. e~ectrodes, not as sole electrode.

Ring Ground Straightforward design.

Problems with asphalt and concrete around the facility? Not desireable where large rocks are near surface.

Easy to install around existing facility. Hardware readily available. Very efficient due to volume.

Note:. Engineered soils employing .various backfills and/or salts also should he consideredfor difficult locations and situations.

•

.48

EXAMPLES OF VARIOUS GROUNDING LA yours

4 4 4

4 4 4 4 4

4 4 4 4 4 4 4

4 4 4 4 4 Single Rod EaithingSatisfactory for simple applications where water level is high.

Multiple Rod . Earthing .'An effective method. Spacing of each rod is 2 x depth.

Radial Earthing Ideal for medium soil resistivity. Current· split 6 ways.

4 4 4

4 4 4 4 4

4 4 4 4

4

I I

~

Deep Drill EarthingRequired in dry

Limited Area

higher soil resistivity.

areas where

Multiple paths for lightning current.

Jround water is very low or rocky.

drill hole. Reduces voltage rise at the surface.

Radial Earthing Ideal in areas of

Earthing - Use deep

f f f f f f l l ~

49

SUPPLEMENTARY GROUNDING FOR BUILDINGS WITH BASEMENTS

(C)

(B)

(C)

(C)

Building Plan A - Supplementary ground field for building with structural steel columns or concrete columns using welded or wire-wrapped reinforcing bars . (B)

(B)

p

o

(C)·

(A)

I~

P

D

(e)

h

n

(A) OPGP Bus Bar .-0-

(C) 5/8" x 8' Ground Rod

n·

Building Plan C - Same as Plan A except that columns lack reliable electrical continuity and are not bonded to the supplementary field

Building Plan B - Same as Plan A except that ground rods are located at every column

(B) #2 AWG Bare Tinned Copper Wire

D

-

Exothermic Weld to Ground Rod Exofhermic Weld to #2 AWG, Bus Bar or Building Steel

SUPPLEMENTARY GROUNDING, BUILDINGS WITHOUT BASEMENTS p

't;

(e)

U

. U.

U

L (f)

Ground ring is 2' to 6' from perimeter of building

0

(f)

f\- H(C) Ir

(a)

0

D

L

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I

(a)

b. (e)

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b..

~

(e)

(a) #2 AWG solid tinned copper conductor (b) Grounding Electrode Conductor run between the main house service Panel and the main cold water pipe; sized per Table 2-2 (c) OPGP bus bar (d) PVC conduit (e) 5/8" X 8' copper clad steel ground rod (f) Exothermic weld connection

.I:.

51

RECOMMENDED GROUND ROD BONDING. 1. WELD TO ROD IN GROUND 2. OK TO BOLT TO ABOVE GROUND CONDUCTOR

Preferred Welded

O.K. Bolted

Ground Rod

52

SOME IDEAS (not in any Codes) FOR GROUNDING ADDITIVES AND BACKFILLS THESE CONCEPTS WILL INCREASER VOLUMETRIC EFFIQENCIES OF THE £ARmELECTRODE SUBSYSTEMINRESlSTWE EARTH COWmON8- ASKALL VENDORS FOR MSDS & READ CAREFULLY. SULPHUR CONTENT OFPRODUcrS SHOUW NOT EXCEED 5 %.

1. Coke Breeze - 85% carbon bound into a cinder-like matrix. Check MSDS for minimwn, lowest sulphur content variety. Use pebble size, not dust size. Should be installed in slurry form to encourage compaction.

.. Mid Continent Supply, Chicago IL tel.708-798-1110 .. Christianson Bros, Spanish Forks, UT tel. 801 ..798..9158. 2. Conductive Cements .... Carbon mixed into cement. Some types need residual moistW'e. Not recommended where vehicle traffic may crack concrete or where shifting or unstable soils exist. Should be installed in slurry form. Check MSDS. - Electric Motion Co, tel. 860-379-8515; .. ERICO tel. 800-248-9353. .. Sankosha Corp., tel. 310-320..1661 - Loresco Corp., 1-601-544-7490 www.loresco.com 3. Ground Augmentation Fill (GAF). Needs residual moisture. Avoid freezing conditions. Available from LEC, tel. 303-477-2828. Check MSDS. 4. Bentonite. Needs residual moisture. Not recommended in :freezing conditions. Available from Wyo-Ben Co., Billings MT, tel. 406..652-6351. 5. Drip Irrigation (as required). Use a leaky hose or a water container (an upsidedown 5 gallon plastic jerry can on platform works well) and drip-irrigate a slow trickle of 15% salts and 85% water onto the earth electrode area. Drip irrigation/leaky hose is available from Home Deport or equal. 6. Trenching. Deeper is better (to reach available moisture). Don't forget to do your "Locates" first !!!!! Install' backfill with 1/0 stranded copper or equivalent flat strap in below-grade trench approx. 30cm (12 in.) X 30cm, at least 1m (3 ft.) below grade not exceeding 10m (30 ft.)in length. Install yellow "Warning Tape." Compact and backfill with compacted native earth.

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53

TYPICAL DRIVE AND WALK GATE ENTRIES

3'·0" BEYOND FAATHEST SWING OF GATE

CN3LE EQUN..L Y $PACED

-2/0

BARE COPPER CABLE CONNECTION
t12f-~"*"t-M7'~IN=SIDE

--;~:::..--

'::....r-=-_....,.-<...-.-_-4It-

PLANT PLANT

-~OU~TSIDE

CONNECT TO GATE

FENCE PERIMETER . GROUND (SEE SECTION 15)

DRIVE GATE

3'-0" BEYOND f/lRTHEST SWING OF GATE CABLE EQUAlLY SPACED -2/0 BARE COPPER

CABLE

.CONNECTION

nyp.>

au SiOE

PUNT' INSIDE PLANT

2',0"

.I

FENCE PERIMETER GROUND (SEE SECTION 15)

WAlK GATE

NOTE: WHEN THE DIRECTION OF THE GATE SWING IS TO THE INSIDE OF THE SITE FENCE PLACE THE GRID ON THE INSIDE. WHEN THE DIRECTION OF THE GATE SWING IS BOTH TO THE INSIDE AND TO THE OUISIOE, PLACE THE GRID ON BOTH THE INSIDE N-ID OUTSIDE OF THE FENCE. OMIT THE GATE GRID WHEN THE FENCE GROUND IS ISOLATED fROM THE SITE GROUNDING SYSTEM AS INDICATED ON THE GROUNDING Pl.AN DRAWINGS.·

II 54

'-

f-.

''''BONDING TO FENCE SUPPORT POST DETAIL

,",

/.

,

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:--

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/

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t#6 awg Ba~ Copper Conductor (stranCSed)

Ul Rated Mechanical Connedor 410 awg CO&f:H!r Conductor (exothermic elel 80th Ends) '.

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NatiOnal UabtninD

safety aniitUte 891 N. Hoover Ave louisville CO 80021

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10' Jt 314" copper Clad Steel Ground Rod

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55

"UFER GROUND" EMPLOYING CONCRETE SUPPORTING FOUNDATION

Bare Copper Conductor

_

CADWE!..O To Copperbonded Rod

Copperbonded Ground Rod Driven 10 Feet

National Lightning safety Institute 891 N. Hoover Ave louisville CO 80027

CADWELD At Or Near Unstre~ed End Of Rebars

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56

,.

fill

,.,. ,.,.. ,.,. "..

RECOMMENDED SEPARATION DISTANCE OF EARTH ELECTRODE SUBSYSTEM FROM ENERGIZED CONDUCTORS (from MIL ST1J-419A)

". ".

.,.

GRADE LEVEL ~

1/0 AWG ~ BARE GUARD WIRE 10 IN.

L LO~OlO -- J~

CABLE _-...... SPREAD

PROTECTED CABLES

-(DIRECT BURIAL OR IN DUCT)

.. .._ _

(aJCABLE SPREAD L.ESS THAN 3 FEET

~%7////7///7//7///$ / //7/7/// //?/?m/7/7// GREATER THAN 12 IN. LESS THAN 18 IN.

--1

~

~ AT LEAST~

0000- -

lb)

National Lightning Safety Institute 891 N. Hoover Ave louisville CO 80027

12 IN. -

-- -

-

r

. 1/0 AWG BARE GUARD WIRE

10 IN.

1

--000--1.-

CABLE SPREAQ 3 FEET OR GREATER

...... .-, f1"

57

RECOMMENDED SERVICE GROUNDING FOR TYPICAL BUILpING ENTRY

#6 AGW bare copper wire jumper around water meter, and then AWG on to ground bus

I~

INTERSYSTEM BONDING POINT for connection of telephone, television, and radio' antennae grounding wires.

;:=~;;;;d:~r::::' #14AWG Minimum ;:: wires.

grade level 'CO metalliC water seN' 2ft.

Minimum

When steel conduit IS used to protect grounding WIre, 1-__..2Q..f8£lL_ _..1bOM all ends of the conduit to the grounding wire.

National Ughtning safety InBtitute

891 N. Hoover Ave

louisville CO 80027

OptIonal method Is to use a UFER ground. A 1/2 in. dla., 20 ft. long steel rod or #4 AGW bare copper wlre encased In the concrete footing.

59

FACILITY BONDING DETAIL ill

ItW ,

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power cable 220/380 Vl.':;

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telecommunication cable '-' .)

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water pipe

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disconnection spark 9~P

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4.

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THE PROBLEM...-.

,.,. ,.

POOR BONDING CREATES INDUCTIVE COUPLING OF SURGE CURRENT TO ADJACENT CIRCUITS

". ".

,..,.. ,..,..,

(MIL-HDBK 419 (B41) lind MIWTD-laB·114A (B42)

AIR TERMINAL

DOWN CONDUCTOR

CIRCUIT IMPEDANCE

SENSITIVE .) CIRCUIT .

(LOqP)

--

EARTH . ELECTRODE

SUBSYSTEM

National Ughtning safety InstitUte

891 N. Hoover Ave

LoutsvHle CO 80027

d1 & d2 :1& DISTANCES FROM DOWN CONDUCTOR

60

FACILITY BONDING DETAIL a)

Frame is continuou!\ bC'twcen Jocalion~ lmay be bonded between sepaJ'Cue 5Cctions)

Metal

Unprotected side

Protected "Ide

ofcable(s)

ofc:able{s)

cold-water

pipe with grounding ACpower

reeder to telecommunications equipment aR8

chlmp~

StructurAlJ building

steel frame is bonded to the ground

plane (penelrUtions and mounting

'eet)

Typical metill cable: ladde:r and equipment frame

One or ~""l:fal grounding elecuodts located around perimeter

of ground plane (if on grade levc:l)

61

BONDING BUILDING STEEL TO GROUND Beware the insulating abilities ofoxide-reducing paints. Bolted connections across steel columns or plates may not meet a low resistance bonding requirement. A bonding strap or tack-welds may be required.

Typical Installation Weld At Column Base. •

3 -01

=o I

N

\

.

Typical Down Conductor

National Ughtning .Safety Institute 891 N. Hoover Ave LoulsvUle CO 80027

First Floor

GROUND POTENTIAL EQUALIZTION

Creating an equipotential ground plane 'nDder lightning conditions is 'essential for the safety of equipment and personnel. All ground. electrodes must have a common reference in order to minimize potential differences.

OOWNCONDUcrOR EQUIPMENT GROUND PLATE .~

National Lightning safety ln$\ltute 891 N. Hoover Ave Louisville CO 80021

GROUND ELECfROOE CONDUCTOR

63

BONDING SEPARATE GROUND RODS

Home Computer, TV Set, Stereo, etc.

Separated Ground Rods

National Lightning 881etylnStltute 891 N. Hoover Ave louiSVille CO 80027

Failure 'to Bond AC Power Ground Rod to Separate Cable TV and/or Telco Ground Rods willcreate a voltage rise mismatch.,

64

l

l l ~

~ ~

~

4 4

BONDING OF GROUNDING CONDUCTOR TO ITS ENCLOSED CONDUIT

•f •

Remove Insulation at Contact Point - - - Insulated Circuit

Grounding Conductor

_

( ] - - - - - Split Bolt Conductor ~---- Ground Conductor

to Busing ).J~.-----

Ground Bushing

---Conduit

.National LIghtning. . safety tnSttIute . 8t1 N. HOover Ave LouIBvUIe CO 80027

4 4 f f

••

•• •• •

•• •• •• •• •• •• •• ,• •.. t

65

BONDING TO PREVENT SIDE FLASHING SHOWING LOCATIONS IN TYPICAL BUILDING

2

1. ~irTennination . 2. Down Conductor 3. Bond to Aerial 4. Bond to Vent 5. Bond to Re-Bar 6. Bond the Metal Staircase 7. Bond to Metal Window Fnme 8. Bond to Vent Pipe ~. Bond to Steel Door/Frame 10. Test Clamp 11. Indicating Plate °

°

National Lightning Safety Institute 891 N. Hoover Ave louisville CO 80027

12. Main EarthingOTenninal of Electrical Installaoon: 13. Earth Te~tion Point

66

.. .-.. ...... ...... .... ...... ...... ...... ...... ........ .-.. .-.. .. ....-.. .... r r

MISCELLANEOUS BONDING EXAMPLES(MBE) 1

Bus to facility ground and pipe grounding.

Attachments to ground bus.

r

.

-

7"

.~

--==-.--_---=::.Ji. . -

•

~c.;.1-- 1D

-

-Temporary bonding jumper to pail.

Jumper to ground bus.

,

..

_--

II II

Drum pump bond. Drum or pail bonding to ground bus.

'

67

MBE2

Drum and pail bonding.

Drum and pall bonding.

Mixer bonding.

Pipe and drum.

68

I

MBE3

""'.

.,.. ""

.,..,.

...... .... ..... ...... ........ ....

Swinging Door Bonding

til'

Sliding Do'or Bonding

,

i

.1 Shut Metal Hood.-Door1iB~·

(Typ. For 2) Colltng--. Overhead

Doclr

le Bart Copper Ground, CAOWELD Connection io Door TraCk. Door Operator And Shttt MellI Hood

To Stell Column•.

~.CAOWEu)

Connection io

0vef!1ud OoOt

Coiling Overhead Door Bonding .

National LIghtning

safelY InatitUte 891 N. Hoover A.ve

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MBE4

Rail Siding TypIcal Parts Needed For Static Grounding

Tank car bondin9 at siding.

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HIERARCHY OF BONDING JUMPERS

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•• • •• •• •• •

BONDING JUMPER CABLE INDUCTAN~

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Calculated Inductance (l1H) of Standard Size Cable

Length AWGNO.

6 in.

12 in.

36 in.

4/0

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0.238

0.914

110

0.108

0.259

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2

0.115

0.273

1.020

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0.122

0.287

1.063

0.129

0.301

1.105

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0.329

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BONDING TECHNIQUES RATED ON 1:10 SCALE OF EFFECTIVENESS (10 is best)

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Electrical Properties

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High Tempera-

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74

TYPICAL CONNECTOR TERMINATIONS

2-hole crim p type connector

mechanical type connector

com pression H-taps

heavy duty pipe clam p

com pression C-taps

conduit/ground rod clam p conduit bonding hU,b ,

.

'

exotherm ic to bus ,bar

exotherm ic to ' ground rod

ex6th e rm ic' junction

•• •• •• •• •• •• •• •• •• •• •• •• •• •• •• •• ••

.. .. .. .•

75

BONDING INSPECTION CHECKLIST (NLSI recommendation 1 milliohm or less) A.

General Overall Condition (check): Good

Excellent

B.

Poor

Resistance Measurements:

Location of Bond

c.

_

Resistance in milliohms

Deficiencies: Condition or . "

Location

. .NatiOnal ~Ing SBfety Institute

881 N. Hoover Ave LouIavlIIe CO 80027

Deficiency

. Comedve Action Taken

77

INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter Four

EXTERIOR LIGHTNING PROTECTION FOR STRUCTURES Air IcnalDab Db CWIly 1IIop"" roof.

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78

Chapter Four Overview

Air terminals (in the air) are intended to intercept lightning and conduct it along a preferred route to earth/ground. Lightning Rods are mounted directly on the structure to be protected. Masts, Poles and Overhead Shield Wires are placed next to or above the protected structure. All these types of air terminals are validated universally by the codes and standards. Other designs, promoted by vendors seeking commercial advantage, have been rejected by the scientific community. Caveat Emptor! Air terminals usually are an important sub-system in the hazard mitigation toolkit. However, if lightning strikes next to the structure to be protected, and not on it, then no air terminal design has contributed anything to the lightning protection design.

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79

APPROVED AIR TERMINAL DESIGNS (per USA Codes & Standards)

1. FARJ\DAY CAGE OR FARAnAY-LIKE CAGE. Fully enclosed metal box (impractical) Of, 1.1 Steel rebar reinforced concrete per Codes. 1.2 Interior shielding of exterior walls per EMC.

2. INTEGRAL (DIRECT) DESIGN. 2.1

Franklin Rods per Codes.

3. INDIRECT DESIGN

3.1

Free Standing Mast(s) per Codes. 3.2 ,Ov~rhead (catenary) shield wires per Codes.

Codes = NFPA-780, NASA E0012E, MIL 419A, AFI 32-1065, NAVSEA OP 5 and others. Also include international code IEe 62305.

National Lightning Safety Institute 891 N. Hoover Ave Louisville CO 80027

81

-. 82

FLORIDA ROCKET LAUNCH SITES Examples of Overhead Shield Wires (OSW) at Launch Sites SLC 40 (top photo) and SLC 41 (lower photo). The asset is the launch vehicle. The network or grid of grounded shield wires serve to capture both vertical and angled incoming lightnings before they can reach the high value equipment.

83

FRANKLIN AIR TERMINAL ARRANGEMENT ON FLAT-ROOFED STRUCTURE, PER NFPA-780. (PERIMETER RODS WITH 8m SEPARATION. ACROSS-ROOF RODS WITH 15m SEPARATION. DOWNCONDUCTORS TO GROUND WITH 33m SEPARATION.)

National Lightning Safety InstJtute

891 N. Hoover Ave Louisville CO 80027

• 84

LOCATION OF FRANKLIN AIR TERMINALS FOR VARIOUS ROOF CONFIGURATIONS, PER NFPA-780.

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85

TYPICAL FRANKLIN ROD CONFIGURATIONS AND DETAILS PER NFPA-780

GREATER THAN A·,O-

NOT TO ExceeD

Air terminal and bonding placement must attend to all details for effectiveness.

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AIR TERMINAl.

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•• •• •• •• •• •• •• •••

National Lightning Safety Institute 891' N; ffoover.Ave louisville CO 80027

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91

PREFERENCE FOR MAST AND ,OVERHEAD SHIELD WIRE AIR TERMINAL DESIGNS, AS CITED BY CODES 1. Per NFPA-780 (2000), Standard for the Installation of Lightning Protection Systems, Appendix K Protection ofStructures Housing Explosive Materials, K.2, p. 38 Design Consideration: UWhere the effects of electromagnetic coupling are of concern, a mast of overhead wire (catenary) systems might be preferred over integral systems unless a Faraday Cage or shield is required. The removal (isolation) of the down conductors will reduce the magnetic field strength in the structure and reduce the probability of a sideflash from a down conductor."

2. Per NASA E-0012E (2001), Standard for Facility Grounding and Lightning Protection, section 5.2.17, p. 31 Ordinance Facility Grounding and Bonding: "It is recommended that ordinance facilities with a perimeter of over 300 feet that require lightning protection have either a mast or overhead wire system as specified in KSC..STD..E0013 and AFR 91-43."

3. Per US Air Force AFI32-1065 (1998), Grounding Systems, section 14.5, p. 11 Explosives Facilities with Large Perimeters: . "New explosives facilities (including igloos) with a perimeter over 91.4 meters (300 feet) that require lightning protection and do not use the structural steel as the air terminals must nse either a mast system or an over~ead wire system. See Attachment 4 for requirements. Since these' systems provide better protection, and maintenance is easier, consider using this type of protection for other kinds of facilities."

92

CONE OF PROTECTION INTERPRETATION OF ELECTROGEOMETRIC MODEL Important Notes: 1. This is a Theoretical Assumption. Lightning may ignore it. 2. This protection concept does not include safety for people. Touch and Step Voltage issues still apply to persons. 3. Protection angle is a function of height of structure. For example, recommendations by USA NFPA -780 are: 3.1 Structures not exceeding 25 ft. (7.6m) are considered protected with a one-to·two angle. 3.2 Structures not exceeding 50 ft. (15m) are considered protected with a one-to-one angle.

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93

ROLLING SPHERE INTERPRETATION OF ELECTROGEOMETRIC MODEL Important Notes: 1. This is a Theoretical Assumption. Lightning may ignore it. 2. This protection concept does not include safety for people. Touch and Step Voltage issues still apply to persons. 3. Rolling Ball Radii varies according to Codes, for example: 3.1 USANFPA-780, R=46m 3.2 USA Dept Energy and Dept Defense, R = 33m 3.3 International Code IEC 62305 kA R % Protection Level I 3 20m 99 5 30m 75 Level II Level III 10 45m 50 Level IV 15 60m 50 4. British BS 66551, R:; 20m for buildings with explosives, flammables or sensitive electronic equipment contents.

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95

INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter Five

INTERIOR LIGHTNING PROTECTION FOR THE ELECTRICAL SYSTEM OF A COMPLEX FACILITY

Chapter Five Overview NFPA-780 v. 2004 now uses the "shall" descriptive for installing surge protection devices (SPD) at power and communications circuits. NLSI's treatment of the subject describes: SPD locations; how SPDs function towards transient waveforms; what's inside the SPD boxes; and installation recommendations. There are many poor-performing SPDs on the market, so Caveat Emptor again! Suggested due diligence will include separating reputable vendors from fly-by-nights and asking for Certified Test Results. Also, looking for conformity to the more stringent European lEe codes which award the CE label is a good idea. lEe requires a 10 X 350 us (vs IEEE 8 X 20 us) testing procedure. A first class detailed treatment of the SPD subject is contained in IEEE Std 1100, Recommended Practice for Powering and Grounding Electronic Equipment. This text should be in the librmy of every lightning protection engmeer.

97

CAPACITIVE AND INDUCTIVE COUPLING TO BUILDING INTERNAL WIRING ,

HOW SIDE FLASH CAN OCCUR

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'-

CategoryC 10kV/l01cA

I

I . I Category B

/ Category A /6kVISOOA

16kV/3kA

I

I I I 8ronc;h feeder >20m from

I IrOM'Ormet I I

SPD LOCATIONS PER IEEE

National Lightning Safety Institute 891 N. Hoover Ave Louisville co· 80027

99

AREAS NEEDING SPDs IN TYPICAL COMMERCIAL BUILDING

100

AREAS NEEDING SPDs IN TYPICAL

PROCESS CONTROL PLANT

Prot.
Ip..ot~~;;rtt.". #\0_...m,.-ratvnt. I",uhipt.. ......, " '

I,,""""".

IUlh/tl>o...-ovpIo., ...........,

lunitt. (fAwn, (wllI,"1 monitoring .-qviprnent

~

.uppiy 1"XI

c_

for itKoming POW*f"

In 00l0pMn. 'Y....... 1"1........ comm •• (av. M.cMm1 .ftd

!

oux.lUory ckrtoc..-nm. 4ioor 'Y'Nm' etc..

occ."

I

~f'

•uppty. I/O for control. lSD. ",.. .. go. -y.hfft•• Dcrtocomm. .. • nd fnHn DCS. IS232.... I,s. "'22.. IfM.ron.t. ~ •• l~m4oIftkcrtion. link. Muftipt.a..n

p......mon fo.- tra,"mttt.n • .......t

~ ..."".

..n.. . .

flow.

hmpef"'G'tunl. f\,. OM go•

101

PROBABLE WORST CASES OF TRANSIENT INSULTS FOR LOW, MEDIUM, AND HIGH EXPOSURE LEVELS AT VARIOUS LOCATIONS

- Mains power supply - Category C

• Mains power supply - Category B

System exposure level

Peak voltage

Peak current

System exposure level

Peak voltage

Peak current

High

20kV

10kA

High

6kV

3kA

Medium

10 kV

5kA

Medium

4kV

2kA

Low

6kV

3kA

Low

2 kV

1kA

Derived Irom OrigInal work In IEEE C62.41-1991 and reproduced from as 6651:1992

Derived from origInal work In IEEE C62.4 ,- 1991 and UL 1449 and reproduced from as 6651: 1992

- Mains power supply - Category A System exposure level

Peak voltage

Peak current

System exposure level

Peak voltage

Peak current

High

6kV

SOOA

High

5 kV

125A

Medium'

4kV

333 A

Medium

3kV

75A

2kV

167 A' .

Low

1.5kV .

37.5 A

Low ,

'

DerIVed Irom onginal work In UL 1449 and reptoduced from 6651:1992

as

- Data lines - Category C

,

,

Derived from origInal work in as 6651:1992

CCln IX K I 7 ond reprodllceet Irom

102

~

~

~ ~

C C

VOLTAGE (1.2 x 50) AND CURRENT (8 x 20) TRANSIENT SPECIFICATIONS, BASED UPON ANSI/IEEE TYPICAL WAVEFORMS

Voltage 90% \o----e~- Vpeak (6kV)

Time

1.2J..l.s 50/U Voltage transient Current

I

lpeak (3kA)

90%1---.........

10% Time

20J-ls Current transient

•f f f f f

•• •• •• •• •• •• •

•• ••.< •• ,,• ,, ,, ,, ,,

103

OVERVIEW OF SPD FUNCTIONS

1.

Generic

Gas tube

SIlicon avalanche diode

Varistor

P·lype

N·type

Graphic Symbols used to designate SPD components.

Thyristor SPOs

Voltage-Switching Type ("Crowbar")

Voltage-Limiting Type ("Clamp")

.'.' •••••••,

Prospective voltage

.... 0'

L-.- Sperkover or tum-on 2.

Typical Volt-Time characteristic for a voltage switching SPD.

Crowbars

o

I

I

I

I

1

2

3

4 Microseconds

l'

. .

..•......• '~I~~~'I~~'~~~~~

j ~

.

. 3.

. ....................................................... ........................ "

Typical I-V characteristic of a.clamping SPD.

Normal System Voltage

0.001

0.01

0.1

1

10

100

1000 Amperes

Restrict

4.

Basic two-step (hybrid) defense against surge impingement.

Protected circuit

(

First stage)

(second stage)

104

TRANSIENT LIMITING CHARACTERISTICS OF GENERIC SPD COMPONENTS, ASSUMING 8 X 20 VOLTAGE WAVEFORM.

. Volts

Volts ...

Time

Current

a) GDT waveform and circuit b) MOV waveform and circuit symbol' symbol

Volts

•4

•• •• •• •• •• • •• •• •• •• •• •• •

•• .•, •• •• •• •...

.'

Current'

,c) 'S':'ppression diode

waveform

, and circuit symbol" '

>

.'

'

•

...... ...

105

RELA TIVE ADVANTAGES AND DISADVANTAGES OF PRINCIPAL TYPES OF SPD PROTECTIVE ELEMENTS

Energy Protective level handling (sensitivity) capability

Component

Speed of response

Gas-filled discharge tube

Fast (microseconds)

fair

High

Fair

High-energy handling when $0 constructed. low-voltage ionization levels, versatile, selF-restoring, long-life, maintenance-free Initial high voltage resistance let through

Fast

Poor

High

Poor

Highly unstable and vulnerable to changes in environmental conditioM, will not divert transients under 600V which will destroy $OlicJ..stote equipment, requires maintenance

Slow (millisecond)

Good

High

Good

Good in olmost ell areas except speed of response -

Corban gop

fast

Poor

High

Poor

Fairly fast response, but nol completely self-restoring (in case of high-energy transients), ionization level too high to protect semiconductors, noisy in operation, requires maintenance

Zener diodes

Very fast (picoseconds)

Very good

low

Very good

fast respoM8, but seriously limited in energy· handling capability - will not protect equipment from external transients $uch as lightning or induction from power lines, easily damaged

Circuit breakers

Slow

fair

High

fair

Very slow, require maintenance, bulky

fuses

Very slow

Good

High

Fair

Require replacement. Responce time determined by fuse CUffent

Meta\.oxide varistor

Very fast

. Fair

High

Poor

'Soft' voltage clamping characteristic is not sufficiendy accurate for modern Iow-power semiconductor devices ,

Air

gap

Surge relay

Stability

Comments

the millisecond response cannot prevent the microsecond death of transistors requires maintenance, bulky

characteristics change over lifetime/and number of pulses absorbed

National Lightning safelY Institute 891 N. Hoover Ave louisville CO 80027

106

DESIRABLE SPD OPERATING CHARACTERISTICS (Adapted from G. Celli, ICLP 2003

Voltage protection level (Up): parameter that characterizes the perfonnance of the SPD in limiting the voltage across its tenninals; Residual voltage (UreJ.· peak value of .voltage that appears between the terminals of an SPD due to the leakage of a discharge current; . Maximum continuous operating voltage (UJ: maximum rms or de voltage which may be continuously applied to an SPD; Nominal discharge current (l,J: crest value of the current having a wave shape 8/20; Maximum discharge current (l~ .• crest value of a current through an SPD with 8/20 wave shape and ' magnitude according to the operating duty

,t~st

(lmax:>ln); . . .. . . . . . .. ... . . Impulse current (limp):, defined 'by 'a curr~nt value (Ipeak), 'a 'charge' (Q) and a specific'energy (W/R).

National Lightning safety Institute 891 N. Hoover Ave .Louisville CO 80027

'

107

THREE STAGE SPD COMBINES GOOD PROPERTIES OF DIFFERENT PROTECTION DEVICES TO MANAGE AN INPUT TRANSIENT OPTIMALLY.

>---e--t

VOLTIOE

DROP

ELEMENT2

L\V1= R.i LIGHlNI

or AV1 = l.diJdt

TRANS

VOL11GEI CURRENT SOURCE STIOE2

MOVDSlI~

PR O'1"B:TED INPUT

SWE1

mlUlNCHE

DIODE (SAD)

-Problem: A lightning surge strikes a signal input in electronic equipment. This surge can be represented by a voltage/current source with the open-circuit voltage/short-circuit current characteristics of the combination wave of page 43. The surge energy is diverted to ground as folloWS: 0) Current will not flow until the input voltage reaches the SAD's clamping voltage. The open circuit 1,2150 f.lS voltage curve applies. 1) The SAD fires in about 1 ns and clamps the voltage at about 18V thus protecting the exposed input effectively. Short circuit 8120 Os current curve applies approximately. Since the SAD can dissipate only 1500 Watts (80 Amps). the rising current must be redirected to a second stage. 2) As a second stage a MOV is usually chosen to keep the clamping characteristic, preventing short circuit of the signal source at low energy transients. The current or the rate of rise of the current, which now is entirely circulating through the SAD. creates a voltage AV1 across the Voltage drop element 1. When the total voltage AV1+VSAD reaches the MOVs clamping voltage (about 27V) the current flows through the MOV, protecting thus the SAD. 3) The still rising surge current develops a voltage drop AV2 across element 2. When AV2+VMOV reaches the gas tube firing voltage the gas tube turns on and directs most of the extremely high lightning energy to earth ground. A 90V gas tube will fire at its rated voltage in about 1 s. But its firing voltage depends on the rate of rise of the 'applied voltage. During the very fast lightning transient it will fire at about 650V. Solution: The three-stage SPD combines the time response, clamping characteristics and energy handling capabilities of different devices ensuring effective input protection and avoiding protection device failure. Courtesy Profs. C. Brio:to tprd M.. Simon, Univ. de 111 Republica, Montevideo Uruguay

108

C C C C

«

SURGE REFERENCE EQUALIZER (SRE)

« «

SREs eliminate the threat of potential differences where data and AC power lines are remotely grounded. Power and data lines are connected to the SRE. The SRE is installed at the point of use of the equipment. SREs are available at most electronics stores.

« « « 4 C C C

C

100

Fuse TIp

•(

Power Sup pression

(

L TELEPHONE LINE

Gas

tube

.

N

G

Ring 100

Surge reference equalizer

Service. . panel

...

/

Branch circuit

Metal water pi pe

Telephone protectors

109

SURGE PROTECTION CHECKLIST 1.0 The following factors justify the suitability of SPDs: 1.1

Surge damage has been suffered or is suspected.

1.2 Surge damage has been suffered by other nearby facilities or organizations.

1.3 A Risk Analysis indicates significant probabilities. 1.4 The consequences of surge damage are serious, despite a low probability. 1.5

Surge protection is specified by an insurance company -or parent organization.

1.6 Experience with surge protection elsewhere has validated their application. 2.0 What should SPDs protect? 2.1

Main Entry Panel

2.2

Selected Branch Panels according to criticality.

2.3

Telephone Lines and Telephone Switch.

2.4 Cables for Telemetry, Instrumentation, and Control 2.5

Antenna Cables

2.6

Security and Fire Alarm Systems

2.7

Outdoor Lighting.

110

4 4 4 4 4

4

4 4

4 4

RECOMMENDED SPD SPECIFICATIONS

« NLSI applies the below criteria in assessing merits of protection devices:

surge

1. UL 1449 Listed under TVSS for load side installation AND UL

1449 Listed for Surge Arrestor for line side installation. 2. Replaceable MOV modules. No spark gaps with impulse breakdown voltages. No use of potting' compounds to encapsulate MOVs. 3. Environmentally-neutral materials with no off-gassing. 4. All mode protection L-N, L-G, N-G, L-L. 5. Internally-fused disconnects on each phase for means of circuit protection from failed components. 6. SPD passes tests per IEEE Std C6234 sub 7.5 and 7.5.4 for loss of neutral protection. 7. Cable connection between bus and SPD minimum # 8 AWG. 8. Enclosure all steel with UL-approved fasteners. 9. No power consumption. No follow-on current. 10. Response time less than one nanosecond. Self-restoring response.. 11. Bipolar operation. Clamping operation is the same· for external or internal transients. ' 12. Continuous self-monitoring with indicator lamps for each mode , and remote alarm relays in each phase. Audible' alarm .with push~ to-test and push-to-silence abilities. 13. Independent, certified test results furnished. 14. Manufacturer compliance with ISO 9000 QC procedures. 15. Meets all requirements of FAA. Accepted by FAA for high threat environments..

« « « « « 4

« « « « « « « « 4 4 4 -4·

4 4 4 4 4 '4 ~ ~.

National Ughtning safety Institute 891 N. Hoover Ave LoulsvUleCO 80627

~

4 4

4 4 4

111

RECOMMENDED SPD INSTALLATION PRACTICES 1. SPDS should be installed as close as possible to their respective panels. Inches instead of feet is the Rule. Lead length is critical for the SPD to operate efficiently. For example, a #6 AWG cable length of five feet causes a voltage drop of 275V. Where possible, mount the SPD directly against the panel to be protected. 2. Avoid tight bends. Follow the NFPA-780 eight inch Rule to minimize inductance. 3. Leads should be twisted to reduce magnetic coupling. Refer to FAA-OI9d, Table V, page 35 for details. 4. SPD remote monitoring alarms should be placed in a fullyoperational area, not in a closet or in an infrequently-visited equipment room. 5. SPDs should be inspected regularly. During the lightning season look them over daily. Smell smoke? Many SPDs work via failure. A burned SPD module should be replaced promptly.

National Lightning safety Institute 891 N, Hoover Avo louisville CO 80021

112

SPD EVALUATION FORM The following tables can be used to compare different TVSS products or to document the different lVSS device specifications for the correct application. Note: the numbers provided are example specifications, typical for TVSS devices intended for a staged application.

Specifications/features desired Sample

Hardwired TVSS Model 1 Model 2 Model 3

Sample

240V 300V

120V 150V

Protection modes

5

3

UL

approved

x

-x-

Let through voltage

750 V

330 V -

Warranty

5 Yr.

1 Yr.

Pricing

$250

$65

Application voltage MCOV Peak surge current Filter freq. range Energy rating Response time

Operational indicators Diagnostic indicators Overcurrent protection Alarms

Manufacturer name

Communications TVSS Sample Model 1 Model 2 Model 3 Application voltage MCQV.

240V 300V

P.eak surge current' Filter freq. range Energy rating Response time Protection modes

5

UL

approved

x

Let through voltage

750 V

O'perational indicators Diagnostic indic,ators Overcurrent protection Alarms Warranty

1 Yr.

Pricing

$250

" Manufacturer name

Receptacle TVSS Model 1 Model 2

Model 3

113

USEFUL SPD FOLLOW-UP REFERENCES

1. IEEE Std 1100-2005 Powering and Grounding Electronic Equipment, Institute of Electrical and Electronic Engineers, NY NY 2005

2.. Internet Web Sites: 2.1. www.polyphaser.com 2.2 www.phoenixcontact.com 2.3 www.mtlsurgetechnologies.com 3. EMCfor Systems and Installations, Tim Williams and

Keith Armstrong, Newnes·Publishers, London 2000 4. Noise Reduction Techniques in Electronic Systems, HenryW. Ott, John Wiley, NY NY 1988. 5. Protection ofElectronic Circuits from Overvoltage, Ronald B. Standler, John Wiley, NY NY 1989. 6. Recommended Practice for Protecting Residential Structures and Appliances Against Surges, EPRI PEAC Corporation, EPRI~ 1999

National Lightning safety Institute 891 N. Hoover Ave Louisville CO 80027

Ode to the Missing Surge Protector Author Unknown, Supplied by National Lightning Safety Institute www.Iightningsafety.com

If a transient hits a pocket on a socket on a port And the bus is interrupted at a very last resort And the access ofthe memory makes your floppy disc abort Then the shocked packet pocket has an error to report. Ifyour cursor finds a menu item followed by a dash And the double-clicking icon puts your window in the trash And your data is corrupted 'cause the index doesn't hash Then your situations' hopeless and your system's gonna crash. Ifthe label on the cable on the table at your house Says the network is connected to the button on your mouse But your packets want to tunnel to another protocol That's repeatedly rejected by the pririter down the hall And your screen is all distorted by the side effects of gauss So your icons in the window are as fickle as a grouse Then you may as well reboot and go out with a bang 'euz sure as I'm a poet, the sucker's gonna hang.

National Lightning Safety Institute 891 N. Hoover Ave

louisville CO 80027 .

115

INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter Six

COMMUNICATIONS FACILITIES, EXTERIOR LIGHTNING PROTECTION

116

" •

•• .,.

.

" ,.,. ", ",

Chapter Six Overview

~etY applicati?D, Communications facilities often have a critical life..$ lie broadcasting especi~ly wit? E911, air traffic control and some on some .levels operations. This Chapter and the following Chapter 7 fo~ " for Engmee!s. of detail not contained elsewhere in Lightning ProtectiIJ can be applied However, many of the principles in these two ctmpte.t6 generally to other facilities. . ... . COnsider vari~us t Extenor lightnlng protection of communications SItes muS OiDg and bondmg ~esigns of towers, adjacent equipment buildings and grouJJ ~ce cannot be ISsues at both locations. Regular inspection and maintc ignored without peril. ent Installations Motorola R56 Quality Standards for Fixed Network EquiP'" is a recommended follow-up to information herein.

pll::S

", ",

.. •.. -,... f!I' fl-

". ".

".

".

... ,.,. ,.. ". ".

117

TOWER BONDING - SELF SUPPORTING TOWER

Grounding KM

I - ~ Grounding Kit

..

To Central Office

J ,

..

2 1001 (0.6 me'.r) minimum below graoe To Central Ground Field

116 Bare Copper

ClAOUHDIlOD_

National Lightning Safety Institute 891 N. Hoover Ave louisville CO 80027

."

118

TOWER BONDING - GUYED TOWER

BOND TO SHI8.0

BONO GUYS TOGETHER

AND TO A GROUND ROD

IfSBARE COPPER

TO CO GROUtJO FIB.O

•

•• •• •• ,• •• •• •• •• •• •• •• •• •• •• ~ ~ ~ ~

f f f

4 National lightning

Safety lnatftute 891 N. Hoover Ave louisville CO 80027

• • • _ _ 0.

_

.....

_

. _ - _• • • • '"

C

« « « 4 4

119

TOWER BONDING - BUILDING MOUNTED

' - - - Grounding Kits

DOD DOD

.....- - '2 Copper

....

To Central Office GroUnd Field

National lightning

safety InStitute 891 N. Hoover Ave Loulaville CO 80027

120

GUYED TOWER WITH EQUIPMENT BUILDING, GROUNDING CONFIGURATION

llnnBd AWG #2 solid or -.rancl811.nol>-InSutalllcl _ _ _ copperwue

TInned AWG #2 lOUd or

IUandad. non·inlulaled c:opperwite

~r

8

~--1~

__

ExltmII bUM bar 1II f1l\Iy point ClQIlIMC:Ied 10 lI>Cltmal ground ring UIlng lIMed AWG "2 ,olill or nandad, non-lnlutaled c:opPt' wira.

Grounding Guy Wires at anchors:

MONOPOLE TOWER WITH EQUIPMENT BUILDING, GROUNDING CONFIGURATION

llnnacl AWG ;n IOIld or llranded, non-insulated c:opper wlr1I

building

121

OPTIMUM GROUNDING DESIGN SHOWING PERFORMANCE WITH LIGHTNING ATTACK (Source: Polypbaser Corp.)

Recommended site grounding system about to be hit by lightning.

On a well designed ground system, the strike energy spreads out initially from the building.

Neglecting the coax currents, the strike energy moves outward from the tower base along the radial line.

As It spreads, " loses energy due to the spreading and I·R losses.

+--f--G""""OAOOS

""LIN

ENTR'f

As it reaches and saturates the radial system, It will traverse the building perimeter.

By the time It surrounds the building, the radials have spread out much of the energy.

122

TYPICAL COMMUNICATIONS SITE, EXTERIOR GROUNDING PLAN Pt.ANE MESH Sl7f.lSPACING BE MINIMAL SIZE PHACTICAL

.---_ EOUIPOTENTIAL S~IOULO

·STnUCTUUE

,

.,",

.-'

/f,

~

~

' J~r

K. .

METAL PIPES ENTERING

THE fACILITY-SHOULD GROUNDED AT TilE

, /

I ...... '-

.

B~' ".,. I ,JJ,

FACILITY ENTRY POINT

'~.., ,

,,\

"

\)

~/EA/R"T'tf

/" ,. ...... ,

f,

I"""

Y

I

/"

,

~"

,. ....

El.ECTRODE SUOSYSl EM ' ./" ROUNDING Fon fOlJlPOTENT~ LANE

·--·GHOUN[)ING FOH S TRucn JHf\L

STEEL

National Lightning safety Institute . 891 N. Hoover Ave Louisville CO 80027

,'-

I "

"

'''

""

... )

/

/

123

EXAMPLE OF EXTERIOR GROUNDING RING (ALSO CALLED COUNTERPOISE)

nNNED AWG 11'2 SOUD OR STRANDED NON-INSULAlED COPPeR

----------

GENERATOR

~X X ..,j... "

'l'

" "

)K I

)K

X X X X X X X X X X AlR CONOlnONER

~ X X X X X 2<~t

Tj

.,

/ . , .... _ ./

t---I-------·-----/--~---.__

I

*

~ .E"=~

I

>Ie:

* *f I

*/

BUILDING laCOANO

I

:

I :"

1-;l;;.~~I~--------------- ~ ' . /

..I...

I

/ ~

!

GROUND

/.---------~- .. --------..-?'~~w

./

~\X X X FENCE CORNER POST

*7*

GROUND RODS

xxX

FENCE

'

EXTERNAl GROUND

~ DOUBI.£

RING A MINIMUM OF

DOOR GATE

TWO FEET FROM BUllOlNG

~

OR Cl.AMPEACH GATE TO

Nons: IN WHERE GATE MATERIAl. IS iMPROPER FOR ~WELD. CUlMP WITH APPROVED MATERIALS.

,

SUPPORT' ~OC>o
,

-....,

124

ALTERNATIVE COAXIAL CABLE ROUTING FROM TOWER TO EQUIPMENT BUILDING

ADVANTAGES Low l dlldt voltage

DISADVANTAGES '} Coax must make tight bends.

InoUne

P,olllClo'

21 Coax enters at floor level.

BEST

l..-Llne

Prot.cIor

low L dVdt at tower

1) large L di/dt for in line protector unless large grounding surface area conductor is used for building CGK and protector. 21 Sloped line will intercept tower mag fields.

GOOD

Low l dildt at bUilding

11 Coax must enter at floor level. '2)

Slop~d

line will intercept tower mag fields.

OK

BulkhMcl Panel InoUne

Protector

ACCEPTABLE

1) Enters building high. 21 Does not intercept tower mag field.

Large straps cost more but are needed to reduce L di/dt voltage

Na' nal Lightning safety Institute , 891N. Hoover Ave

louisville CO $0021

125

BOND OUTER SHIELD OF COAXIAL CABLE AND ELLIPITCAL WAVEGUIDE TO TOWER LEG

Tower Leg

IC==::::=l.-- Bonding Clamp and Weather Seal

#6AWG

Elliptical Waveguide

Entry Plane

Transmission Line

Grounding klls should connect to tile entry p,lite at a ,common poln, and run In a downward dlrecllon tOWllld grOUnd,

To Cenlral Ottlce Ground Flekl

National Lightning

Safety Institute 69' N. Hoover Ave Louisville CO 60027

+

Connecllon 10 grouno flelo 5houIQ be eXlernal to the Central Offica I)uilolng

126

TYPICAL TREATMENT OF INCOMING COAXIAL CABLES Bond the cable sheath to the exterior building ground reference at the bulkhead. Install SPDs immediately at coaxial cables at the bulkhead. Assure that bulkhead is well-grounded. Bond cable trays to bulkhead.

llc••

-

GFIOUNOlHQ KIT ~NSIOEBOOTl

. 1ofJl.11Pti1.ltlCN COPPER stAAPs

TO AAOIAL SySTEM

The Idelll grounding 50lutlon 15 to. develop II single point ground 5Y51em III the bulkhead ell/TII/l(t panel. ProtectOT5 elln be mounted to this pllnel to prevent sUlgreu';'enl from going Into the tqllipmf/l'-

127

GROUNDING CHECKLIST FOR COMM. SITES TABLE I, EXTERIOR ITEMS External Ground Bar External Ground Ring Isolated Ground Bar

IGR IGZ MGB

Isolated Ground Ring Isolated Ground Zone Master Ground Bar

KEY:

EGB EGR 1GB

GENERAL:

All bends in ground wires are to have a minimal 8-inch bending radius. AC surge protector to be installed on the load side of the main ac disconnect. AC to tower lighting to be surge protected. IGZ cable tray to be isolated from all other cable trays. IGZ cable tray to be isolated from all casual contacts with ground. No ground wires in metal conduit unless conduit is bonded to ground at both ends. Table 1.

ITEM

v

ExtemalSite Grounding Checklist DESCRIPTION

CONDUCTOR

CONNECTION

All Siles (MTSO And CeU) Require:

Connections to the EGR (External Ground Ring): I 2

EGB IGR (each comer and every 16 feet between)

Note 2

CADWELD

#2 solid

CAD WELD

3

ground rods (every 16 feet) and under EGB

#2 solid

CADWELD

4

MGB

#2 solid

CADWELD

All Cell Siles Require:

Connections to the EGR (External Ground Ring): I

tower ground ring (2 connections recommended)

#2 solid

mechanical

2

lightning arrestor bracket

#2 solid

CADWELD

Connections to the tower: I

from tower ground ring

#2 solid

CADWELD

2

lOp of rf lines

ground kit

3

rf lines at exit from tower

ground kit

mechanical mechanical

4

guy wire to ground rods (guyed towers only) Connections to the tower ring:

#2 stranded

mechanical

I

#2 solid

2

from tower leges) from EGR (2 connections recommended) Miscellaneous external grounding connections (connect to nearest pointo! external system):

I

metal fencing within 7 feet

#2 solid

'Note 1

2

metal building parts

#2 solid

Note I

"

#2 solid

I

CADWELD "

CADWELD

..

3

fuel storage tanks

#2 solid

Note I

4

utility grounding electrode systems

#2 solid

Note I

5

metal objects more than 2 ft. sq. and within 7 ft.

#2 solid

Note 1

6

reinforcing bar in concrete floor (if accessible)

#2 solid

Note I

7

building skids or anchors (if accessible)

#2 solid

Note I

8

exterior cable tray, ice bridge generator grounding system (if applicable)

#2 solid

#2 solid

Note I Note I

generator chassis (if not otherwise grounded) Connections to the EGB (External Ground Bar):

#2 solid

Note 1

#2 stranded

mechanical

#2 stranded

mechanical

#2 solid

CAD WELD

9 10

2

waveguide entry window rf line ground kits at building entry

3

EGR

I

NOTES: I. All below ground connections muSl be exothermic. Above ground connections may be mechanical. 2. Either two #2 AWG solid wires or one 2-inch x I/I6-inch coooer strao must be used.

128

~ ~

~ ~

4 4 4

4

~ .

~ ~ C

~ C

C .. ~.

C C C

• C

~ C

C

129

INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter Seven

COMMUNICATIONS FACILITIES, INTERIOR LIGHTNING PROTECTION

. - Transient protectors should always be . installed between the source of the threat and the equipment we are trying to protect

130

4 4 4 4 4 4 4 4 4 4 4

Chapter Seven Overview

4 4 4 4

Several classifications of SPDs, signal reference grids, computer grounds, AC grounds, single-point grounds, multi-point grounds, lightning grounds, Halo Grounds, equipotential bonding, shielding, cable tray treatment, LANs, isolated equipment protectors ... this is a busy subject. Attention to detail is required to avoid calamity.

• •

FAA~

•

STD-019d Lightning and Surge Protection, Grounding, Bonding and Shielding for Facilities and Electronic Equipment. Critical operations at airport control towers - with safety from lightning's effects - are descnoed

•~

For further reading and much more depth on the subject, we suggest

• ~

here.

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TYPICAL COMMUNICATIONS SITE, INTERIOR GROUNDING PLAN

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132

"HALO GROUND" PROVIDES SHORTEST-DISTANCE BONDING BETWEEN EQUIPMENT CABINETS AND EARTH REFERENCE.

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.(1) - Equipment Lineup (2) - Power Plant (3) - Miscellaneous Unit (4) - Waveguide Hatchplate (5) - Antenna Tower Leg . (6) - E:ngine-AltematorEnclosure

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133

EXAMPLES OF INTERIOR GROUNDING & BONDING

Ground Grid BUILDING

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Power Protection Layout CAIU TAAY SYSTCM (MUST BE BONDeD TO

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PAOTl'CTOR

CONDUITINF1.OOR

OUT 10 GIIOUND 1.001\ lYPlCI\L, AU. CORNERS OF EOUIPMENT ROOM.

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4

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134

4 4 4 4 4 4

BONDING RAISED FLOOR IN COMMUNICATIONS OR COMPUTER ROOM TO ACHIEVE EQUIPOTENTIAL GROUNDING

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Walls

.

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Hdonal Ughtning

Safety Institute . 881 N. Hoover A.ve

Loulavilte CO 80027

.

•• •• •• • ~

~ ~ ~ ~

135

BONDING INTERIOR :METALLIC COrvtPONENTS TO OBTAlN EQUIPOTENTIAL GROUNDING

Structural steelwork (and re-oars)

Plumbins ana ;)ioewcrk

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Ave

LouisviIe CO 80027

• ••

136

•

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CABINET OR RACK BONDING DETAIL FOR ·COMMUNICATIONS EQUIPMENT

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Individual

Isolated

Electronic

Electronic

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Equipment

Ground Bus (SPG)

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Equipment Gtollldlng Conductor connected to ~ronlc EquIpment Rack . and

Electronic Equ~ Enclosures

~~ ... To SinglePoint' Grounding System

:\ AC p.ower line

. National Lightning

Safely Institute 891 N. ffoover Ave loUisville CO 80027

To Multipoint .Ground System .

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138

DETAILS OF CABLE TRAYS & DUCTS

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Continuity between sections Wires OK for 50J60Hz. but poor for higher frequencies· ShOlt, wice Straps (one eacn side) ~reterred

"

Bonding cable trays

and ducts to cabinets

c;S;

baSe of OlJct or tray bent down and fixed every 100mm

U-brackets wlttl multiple fixings are good at I'Ilgh frequencies· seam welclea JOInts are oest

U·braCket • seem welded. or fixed every 100mm

* MAINTAIN MINIMUM 2-INCH SEPARATION BETWEEN CONDUCTOR BUNDLES.

Nationai Lightning safety Institute·

. 891 N.. Hoover Ave

LouiSviUe CO 80027

CONTAOlllNTERCONNECT UNES

139

GROUNDING CHECKLIST FOR COMM. SITES TABLE 2, INTERIOR ITEMS Table 2. ITEM

Internal Site Grounding Checklist DESCRIPTION

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CONDUCTOR

CONNECfION

Connections to the MGB (Master Ground Bar): I

racks containing rf equipment

#6 stranded

mechanical

2

waveguide entry window

#6 stranded

mechanical

3

RMC (receiver multicoupler)

#6 stranded

mechanical

4

telephone protector grounding tenninal

#6 stranded

mechanical

5

generator chassis (if not otherwise grounded)

#6 stranded

mechanical

6

channel bank racks

#6 stranded

mechanical

7

EGR

#2 solid

mechanical

8

metal water utility pipe

#6 stranded

mechanical

9

multi-grounded neutral

#6 stranded

mechanical

10

building steel (if accessible)

#6 stranded

mechanical

11

IGR

#2 stranded

mechanical

12

1GB

#2 stranded

mechanical

13

ground bar of +24 Ydc power system

#6 stranded

mechanical

14

ground bar of -48 Ydc power system

#6 stranded

mechanical

Connections to the IGR (Internal Ground Ring): I

all racks not grounded to MGB or 1GB

#6 stranded

mechanical

2

ventilation louvers and ducts

#6 stranded

mechanical

3

cell site cable tray (multiple points)

#6 stranded

mechanical

4

metal door and window frames

#6 stranded

mechanical

5

metal battery racks

#6 stranded

mechanical

#6 stranded .

mechanical

.. '

6

Halon system

7

transfer switch enclosure

8·

miscel1ane~us significant

9

EGR (every 16 ft.)

10

MGB

metal Objects

#6 stranded

mechanical

#6 stranded

mechanical

#2 solid

mechanical

#2 stranded

mechanical

Connections to the 1GB (Internal Ground Bar): 1

MGB

#2 stranded

mechanical

2

cellular switch frame

#6 stranded

mechanical

3·

grounds from a~ o.ut.lets i~. the

#6 stranded

mechanical

#6 stranded

mechanical

st~ded

mechanical

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IGZ cable tray (one point only)

5

JOZ distribution frame

#6

6

modem frame

#6 stranded

mechanical

7

other EMX associated frames'

#6 stranded

. mechanical

..

140

..

•• •-

SPD & UPS LAYOUT FOR COMM. BUILDING

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141

SURGE PROTECTION ADDED FOR SUSCEPTffiLE EQUIPMENT

Surge/impulse

Surge/impulse Neutral

Feeder Panel board and SPD (typical)

Lateral

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S rvice equipment

t - - - I - - - - - - - ' i""----~Victim

..... . . . . equipment Service

g.rollnd~

Branch circuit typical)

Service ground

Central office feeder (COF) cuble or interbuilding cable

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Underground metal coldwater piping main service

-+

Plywood backing with SPDs and punch blocks (Q. elc.

a

Surge/impulse Metal cold-water piping system and telecommunications ground connection

Telecommunications ground and grounding conductor

Surge/impulse

142

SURGE PROTECTION CHECKLIST 1.0 The following factors justify the suitability of SPDs: 1.1

Surge damage has been suffered or is suspected.

1.2 Surge damage has been suffered by other nearby facilities or organizations.

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1.3 A Risk Analysis indicates significant probabilities.

t 1.4 The consequences of surge damage are serious, despite a low probability.

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1.5

Surge protection is specified by an insurance company or parent organization.

4 4 4

1.6 Experience with surge protection elsewhere has validated their application.

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2.0

~

What should SPDs protect? 2.1

Main Entry Panel

2.2 Selected Branch Panels according to criticality. 2.3

Telephone Lines and Telephone Switch.

2.4 Cables for Telemetry, Instrumentation, and Control 2.5

Antenna Cables

2.6

Security and Fire Alarm Systems

2.7 Outdoor Lighting. NAllClfIW.. tJGH1'NNG s.tIf£1'Y IGlmJ1'E If1 Nofttt HoowJr Ave. ~co 80027-22M

143

SPD LOCATIONS FOR SATELLITE SYSTEMS

RECEIVER / ACTUATOR

SPD

UTILITY GROUND

"'- SPD "

GROUND RODS EVERY 20'

SIGNAL& "- CONTROL CABLES

"-- SPD

Natio~all.ightning

safety Institute 891 N. Hqover Ave louisville CO 80027

. ffi~··

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144

MORE SPD APPLICATIONS FOR COMMUNICATIONS

o

SPD

Local Area Network Grounding

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GROUND RODS ~ COPPER CLAD STEEL 518" OIA. 10' LONG

. SWITCHER

8'-12' SEPARATION COAX TO SWITCHER

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CAOWElO OR CLAMP CONNECTION OF 'GROUND DOWN LEADS" AND GROUND ROO

SPD TOSWlTCHER GROUND SYSTEM AND OTHER GROUND RODS

" ' - - 3 OR MORE LOOPS IN COAX 12" DIA. TAPED TOGETHER tAYONFLOOR

145

RECOMMENDED SURGE PROTECTION FOR THE LAN

Office

Factory A

Bridge

Factory B

o

National Lightning safety Institute 891 N. Hoover Ave Louisville CO 80027

Tranlallver

146

ALTERNATIVE METHODS OF SHIELDING FOR SURGE PROTECTION & REDUCTION

Common Wire Types

~ Braid Shield

~

Shield Against Below average shielding characteristics against inductive and capacitive c~upling. Above average shielding characteristics against capacitive coupling. Average shielding characteristics against inductive and capacitive coupling.

Combination Shield

~ Foil Braid

Best shielding characteristics against inductive, capacitive and electrostatic coupling. Good shielding characteristics against inductive and coupling, Best shielding against electrostatic discharge. capa~itive

National Lightning . Safety Institute 891 N. Hoover Ave Louisville CO 80027

147

BONDING OF ALL CABLE SHIELDS TO TERMINAL STRIP

SIGNAL LIKE

OVERAll INSULATION

SHIELD

SI2E~

NO. 16 AWe OR LARGER- lENGTH: 2 INCHES OR LESS

'::::::::=d:;t~(j .. ~~-"£QUlPMtNl TO

-

tASE

TERMINAL STRIP

National LIghtning S8f8ty Institute

891 N. Hoover Ave

louisville CO 80021

148

NOISE OR "HUM" REDUCTION TECHNIQUES

• • • • •

Grounding Twisted Pair Wire Shielding Transient Protection Cast Iron Pipe

Analog Transmitters Drain Ground

National Lightning Safety Institute 891 N. Hoover Ave Louisville CO 80027

149

NOISE OR "HUM" REDUCTION TECHNIQUE USING "ISOLATED EQUIPMENT PROTECTOR"

GROUND LOOP - HUM

Grounded Protector

t Video/Data

t---~I /--

EqUIpment

t

Power

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Grounded Protector

COAX

t

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Power line Protectors

VideoJOata Equipmenl Power

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T ' - - - - - - - DIFFERENT GROUNDS

--

T

NOT JOINED TOGETHER

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Equipmenl

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Power Line Protectors

.

;;" ' - - - - - - - DIFFERENT

G~OUNDS

NOT JOINED TOGETHEA

National Lightning Safety Institute 891 N. Hoover Ave Louisvll!e CO 80027

T

150

··wrzs

151

INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter Eight

LIGHTNING PROTECTION FOR HIGH RISK INSTALLATIONS SUCH AS ELECTRIC POWER FACILITIES, EXPLOSIVES, MUNITIONS, & VOLATILE FUELS

Chapter Eight Overview Previous chapters in the book have examined subsystems or tools for mitigation of the lightning hazard. Chapter Nine integrates all of them into a homologuous approach. Got your Topological Shielding correctly organized? Have you completed your Decision Tree Checklist? A NLSI six page summary document "21 st Century Lightning Safety for Environments Containing Sensitive Electronics, Explosives and Volatile Substances" is included.

153

DECISION TREE FOyACIl:ITY LIGHlNING SAFETY com by National Lightning Safety InstitUte, www.ligh1Dingsafetv·

1.0 Is lightning protection beneficial? · 1.1 Risk Analysis and ProbabIlIty Study 1.2 Cost vs Benefit? 1.3 Assessment of Risk. 2.0 If Facility already haS been insulted by lightning, omit # 1. 2.1 Examine damaged components. 2.2 Determine vulnerabilities. 2.3 Perform Lessons Learned 3.0 Lightning protection is re.quir~. 3.1 See guidance contamed m IEC 61024, IEEE 142, IEEE 1100, FAA 019d, FAA 6950, MIL 4l9A, NASA E0012E NFPA-780 4.0 Examine Facility and speciJ)' sub-category protection requirements in accord~ce with: . 4.1 Air Terminal optiOns: F~anklm Rod, Overhead, Mast or Quasi-Faraday Cage deSIgns. 4.2 Bonding: Achieve equi-potential of all adjacent

metallics. 4.3 Shielding: EmploY where bene:ij.cial. 4.4 Surge Suppression: Protect all AC power, data, etc

IIOs.

4.5 Grounding: Achieve volumetric efficiencies. . . . 4.6 Lightning Detector: For st~stop of auxiliary AC power & for early ~at wammg; 4.7 Testing: Verify loW tmpedance paths. 4.8 Maintenance>periodic inspections, record-keeping 5.0 Develop Procedures and Policy for STOP/START of activities during lightning threat conditions. 5.1 Recognize impending threat situation 5.2 Notify affected areas to CEASE OPERATIONS 5.3 Personnel to safety locations .

. 5.4 Reassess threat 55- Notify ALL CLEAR - RESUME OPERATIONS

154

PRlNCIPLES OF TOPOLOGICAL SHIELDING (Adapted from Rakov, 2003)

Ground wire

Zone 0 Earth

Zone 1 is located at the building exterior, where bonding and SPDs are applied to all incoming (penetrating) conductors. Example: the treatment of coaxial cables from an adjacent tower as they enter the facility. The shield wires are bonded to ground and the signal lines of the cables are treated with SPDs. This is the first shielded line ofdefense.

the

Zone 2 is' located at 'entry to the communications room inside a building. Further bondiIig and SPDs are applied to this secondary' shield location for all 'conductors inCluding AC power and signal' circuits.

~~ne 3 is located at the ind.iyi~1.!~1 ,~quipment cabinets and(of the eq:uipment itself. Telephone punch blocks also are to be included. Here, additional bonding and SPDs provid'ea third shielded layer. '

NatIonal Lightning safety InStitute ,

891 N. Hoover Ave LouisviHe,C080027

. lightning strike

FORTRESS OR ZONE PROTECTION CONCEPT

, Antenna

·..

~~~~~~~~_ • • _ _ • • 4

••• • '1•

•,

Heat and air condilioning

: .: t

.! Down co_n_du_ct_or-l

..•..•••..•

i••

~

......

..••••• •

computer . appliance screen metol

•

·•• •

Coax

BUilding screen steel reinforcement

·1

••••••••• ~ •••••••• ~

Steel reinforcement room screen

·,,•• ··,,• •

At interfaces between zones, the lightning currents encounter equipotential bonding, SPDs, and screening to reduce transients to manageable levels. (adapted from P. Hasse, 1992)

,,• , ,••

• Field cobles

•• AC power

==_.=.=..

.~:'::':=.•,:,: •.:=_

-

Foundation earth electrode

Telecommunication cables

Intermediate Roar

=_.:= ••:'••:-:: :': ••:7.••:':'••:':'.:-: ••':": ••~._~ ••~ ••~ ••~ ••:':'_.:':' .......~ • •~ • •-__~ ••-••- ••- ••- .........- • •-• •-••-••-••-••- .••-•• - --l ..••i

Steel reinforcement

I

Lightning protection equipotential bonding

• locol equipotential bond· ing overvoltoge arrester

National Ughtning

Field device

. casing

safety Institute 891 N. Hoover Ave louisville CO 80027

PREFERENCE FOR MAST AND OVERHEAD SHIELD WIRE AIR TERMINAL DESIGNS, AS CITED BY CODES

1. Per NFPA-780 (2000), Standard for the Installation of Lightning Protection Systems, Appendix K Protection ofStructures Housing Explosive Materials, K.2, p. 38 Design Consideration: "Where the effects of electromagnetic coupling are of concern, a mast of overhead wire (catenary) systems might be preferred over integral systems unless a Faraday Cage or shield is required. The removal (isolation) of the down conductors will reduce the magnetic field strength in the structure and reduce the probability of a sideflash from a down conductor."

2. Per NASA E-0012E (2001), Standard for Facility Grounding and Lightning Protection, section 5.2.17, p. 31 Ordinance Facility Grounding and Bonding: "It is recommended that ordinance facilities with a perimeter of

over 300 feet that require lightning protection have either a mast or overhead wire system as specified in KSC-STD-E0013 and AFR91-43."

3. Per US Air Force AFI 32-1065 (1998), Grounding Systems, " section 14.5, p. 11 ExPlosives Facilities with Large Perimeters: "New explosives facilities (including igloos) with a perimeter over 91.4 meters (3~0 feet) that require lightning protection and do not use the structural steel as the air terminals must use either a mast system or an overhead wire system~" See Attachment 4" for requirements. Since these systems provide better protectbm, and maintenance is easier, consider using this type of protection for other" kinds of facilities."

157

refinery faulty Installation of double ,'Vall seals and

volatile hydroc.arbon walls is c.ritic.aL

Photo: 1 and other emergency COlnrrrUlllcatl0JrlS antenna/tower sites as ~'en as at communications can centers. NEe 250, R56~ FAA-091e and lEe 62305 needed develop robust lightning defenses.

~

-~

-

-

-

-

- -- --

-

-

-

-

----

158

ERRORS AT CRITICAl.! FACILTIES, PARTS 3 & 4

shown atop the RHS pole cannot and will radius" far exceeds USA and stdJ3.dards. Reslu]t';r TIus 1250 MW gas-fired power plant

i

159

GOING BEYOND THE CODES An Expanding List of Things You Learn On-The-Job By Richard Kithil Jr. National Lightning Safety Institute (NLSI)

www.lightningsafetv.com

General Safety. - Don't work on any lightning protection issues where thunderstorms are forecast. -When working around RF, wear a personal Electromagnetic Energy (EME) monitoring device. - Always have some form of two way communications while working alone. Safe Shelters. - Large substantial buildings are safe places. However, do not contact with anything that could become energized by lightning. This ineludes water from copper water pipes, metal doors/windows, appliances and other electrical equipment, telephones, etc. etc. Sit on a chair and read a book. Get the idea? - Small wooden or fibreglas shelters are fine for sun or rain shelter: for lightning they wont work. Flashover, step voltage and touch voltage issues make them dangerous places. Avoid them - Faraday-like metal shielded refuges work well. They include fully-enclosed metal vehicles such as cars, vans, trucks, buses, heavy equipment (with enclosed ROPS canopies). Plastic cars wont work. Neither will riding mowers, ATVs, golf cars, etc. - The best safe shelter for commercial/industrial applications sis a metal shipping container. Cheap. Portable. Double-duty as a storage area. Watch the details: OSHA requires two doors. Think about ventilation (cut some windows/doors and cover them with expanded metal shielding). Think about benches or chairs (people may be inside for -some time). Think about, keeping out critters like ' snakes, bugs, wasps, birds. Think about a water Supply. InStall battery-powered' lights and fans,'but' do 'not 'install anything working off AC line power.;...-do thjs ': and you have compromised the C~e.' , Electromagnetic Energy Safety - In environments where explosion hazards may exist, non-incendive intrinsically- safe electrical components must be used where acceptable. Note that some areas may be entirely unacceptable for housing electronic equipment. Communications Sites. - Aluminum ladders designed for climbing should not be used as cable trays or ' ,runways."" ' " - Cable separation should consider 'AC power, DC power, RF, groun~ and data "ground cables to avoid induced interference. ~ "Leave all battery issues to a battery "expert.

160

- Fixed or portable fire suppression systems must not be used in communications sites. - If a building has a sprinkler system, make sure the cable runways do not block the sprinklers. - Generators installed outside buildings, within 1.8 m (6 ft.) of the buildings, must be bonded to the nearest practical earth electrode system. Longer distances should have an additional ground rod. - Generators inside buildings should have fresh air intake sized at 1.5 times the radiator dimensions to assure adequate ventilation. Vibration isolation between the generator and frame is recommended. - For tower-top pre-amps which require DC voltage for operation, use a lightning arrestor that can pass DC current. - To pass a safety inspection, must-have items include: ABC and C02 fire extinguishers; fITst aid kit; interior and exterior lighting. - Incoming coaxials must be run through weather ports (boots) which also are rodent/insect proof. - Tower lighting cables carrying AC power should not be bundled along with transmission lines or other conductors anywhere within cable ladders or the building interior. External Grounding. - Before excavating or digging, do the "locates." Call before you dig ! - Exothemic welding should not be done unless another person (experienced in fITst aid) is present. A suitable fire extinguisher should be present during the process. - Wear safety glasses, hard hat, steel-toed boots when working with highcompression fittings. - Braided bonding straps shall not be used because they corrode too quickly and can be a point for RF interference. - Avoid differences in potential. Do not install· separate . grounding .electrode systems. Follow'NEC 250lIEEE 142/FAA 019d requirements here. ' - Before disconnecting a grounding electrode conductor, check for 'current. Never disconnect the gro~d of a live' circuit. ~,.-death or severe injury could result. - For non..critical sites, an electrode system resistance of 25 ohms is OK. For critical sites, where disruption of service could cause system-wide outages, an electrode system resistance of 5 ohms is suggested. "Outside the box" solutions to improving grounds include: chemical ground rods; prefabricated/buried wire grid; Ufer ground; magnesium sulphate; other backfills. (The best costlbenefit artificial .ground, enhancement "electrode is Coke ~ree:z;e.. Avoid Bentonite due .to ·shrink/expand properties.) , -..Check soils for pH (hydrogen ion concentration) for acidic soils· where pH is b~low --In highly.acidic soilsJarger diameter..conductors should be considered~ - Optimum spacing apart for ground rods is 2 X length. - A bare copper buried ring electr04e proyides mor~ conductor surface area than many rods. Consider a ring electrode 'Where practical. .' . . .

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Power Sources. - Aluminum conductors should not be used. Never mix aluminum and copper wires, connectors, panels, or receptacles. The two metals have different coefficients of expansion, so loose connections or joints can result. - Consumer grade power receptacle strips should not be used for permanent installations. Do not mount receptacle power strips on the floor. Damage can result from foot traffic, water, water seepage or fire sprinkler activation with electrocution of personnel a major hazard. Surge Protection Devices (SPD or TVSS). - Gas discharge tubes (GDT) should not be used as AC power line SPDs. OK to use them on signal and data lines. When the GDT "crowbars" the transient it effectively short circuits the line causing a momentary power outage for at least ~ cycle. This normally will trip the breaker. - MOVs are suitable only for secondary protection in a redundant scheme. They act as high impedance open circuits until breakdown voltage is impressed. Then they begin to clamp. Specified breakdown voltage is maintained at low current, but at (lightning's) high currents the clamping voltage might rise higher than specified. MOVs degrade with use and their life is a function of numbers and sizes of surges. - SADs' voltage clamping is constant with use, however individual SADs are unable to absorb very much current. For this reason they are staged in a series/parallel configuration to increase total power handling capabilities. SADs provide the tightest clamping characteristics. SPDs using silicon avalanche diode (SAD) technology may develop an artificial diode bias when subjected to strong RF fields that may be present at AM, FM, or TV broadcast sites. This bias may cause data circuit errors. - Common Mode AC power SPDs should not be used. These devices may fail in a . short· 'circuit' conditlon~' Should ..this occur,. the.' AC power neutral conductor .:.. becomes bonded to.. ~e. ground or equipment grounding conductor:' causing undesired currents in the gro~d or grounding. condu~tor(s).This is a personal safety hazard and a violation of NEC. Note: Common mode circUits may be used on signal/data lines. .. SPDs come in packaged assemblies, typically the above devices are staged inside. - Redundant SPD philosophy is: Protect the Main Panel; Protect Relevant Branch Panels; Protect the .Relevant Plug-ins; Protect SignalJData. - All AC 'power SPDs should have the Inte111atiorial CE ·certification. This' is 'a more rigorous test standard than the IEEE certification. UL certification brings even lesser testing requirements. . . - Maintenance of SPDs enclosed within a panel requires panelboard' cover removal. This work should be performed only by licensed electrician. .- SPD.· cabinets. containing MOVs shall. not be encapsulaUXl. Omy removable ·module MOVs are acceptable.

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- Never look into a fibre optic cable. Invisible laser light is dangerous and can cause damage to the eyes. Air Terminals. - A little bitty lightning rod & downconductor cannot carry all that current and voltage. Where they gonna go? They will attach to all pathways, and flow according to impedances. - Alternatives to rods: Overhead grounded shield wires and free-standing nearby conductive masts/poles. These indirect designs often are better than rods...so says NASA E-0013 and USAF AFI 32-1065. In some cases (ex. steel radio tower) - no rods may be the answer. A rod design is very high maintenance. - Air terminals are one of several lightning protection defenses or sub-systems. Others include: Bonding; Grounding; Shielding; Surge Protection. Select a facility or structure of concern and rank 1-2-3 etc. the above defenses in order of importance. Bonding. - If you don't bond everything, your lightning protection system won't work.

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21 st CENTURY LIGHTNING SAFETY FOR ENVIRONMENTS CONTAINING SENSITIVE ELECTRONICS, EXPLOSIVES AND VOLATILE SUBSTANCES. by Richard Kithi~ Founder & CEO National Lightning Safety Institute (NLSI) www.1ightningsafety.com

1. ABSTRACT.

In the USA civilian sector lightning causes $4-5 billion losses per year (NLSI, 1999). In the government sector, the military (DDESB - Department of Defense Explosive Safety Board) has reported 88 identifiable lightning induced munitions explosions with costs and deaths not calculated. DDESB was formed as a result of the July 1926 Picatinny Arsenal incident which killed 14 people and cost $70 million. The US Department of Energy (DOE) has reported 346 known -lightning events to its facilities during the 1990-2000 period. Recent Russian lightning incidents to arsenals include: June 1998 near Losiniy (Yekaterinburg); and June 2001 near Nerchinsk (Siberia). In Beira Mozambique (October 2002) lightning exploded a military ammunition storage depot with considerable loss of lives and collatem.l damage. The most recent examples of lightning-caused munitions explosions are: 13 Feb 2005, Hezbollah's Lebanese twostory ammunition storage complex near Majadel; and 29 Nov 2005 a government arms depot near Walikale, Democratic Republic of Congo. With such examples, it is difficult to support a position that catastrophic lightning incidents are rare. How to mitigate the lightning hazard at sensitive facilities? This paper suggests adoption of a homologuous lightning safety planning process which can be applied to most contemporary environments. 2. LIGHlNING BEHAVIOR & CHARACTERISTICS. 2.1. Physics of Lightning. Lightning's characteristics include current levels approaching 400 leA with the 50% average being about25kA, temperatures to 15,000 C, and voltages in the hundreds of millions. There are some ten cloud-to-cloud lightnings for each cloud-to-ground lightning flash. Globally, some 2000 on-going thunderstorms generate about 50-100 lightning strikes to earth per second. Lightning is the agency which maintains the earth's electrical balance. The phenomenology of lightning flashes to earth, as presently understood, follows an approximate behavior: the downward Leader (gas plasma channel) from a thundercloud pulses toward earth. Ground-based air terminators such as fences, trees, blades of grass, comers ofbuildings, people, lightning rods, power poles etc., etc. emit varying degrees of induced electric activity. They may respond at breakdown voltage by forming upward Streamers. In this intensified local field some Leader(s) likely will connect with some Streamer(s). Then, the "switch" is closed and the current flows. Lightning flashes to ground are the result A series ofreturn strokes follow. 2.2 Lightning Effects . Thermal stress of materials around the attachment point is determined by: a) heat conduction from arc root; b) heat radiation from arc channel; an~ c) Joule heating. The radial acoustic shock wave can cause mechanical damage. Magnetic pressures - up to 6000 atmospheres for ,a 200 kA flash - are proportional to the square of the current and inversely proportional to the square of the diameter of struck objects. Voltage sparking is a result of dielectric breakdown. Thermal sparking is caused is caused when melted materials are thrown out from hot spots. Exploding high current arcs, due to the rapid heating of air in enclosed spaces, have been observed to fracture massive objects (i.e. concrete and rocks). Voltage transfers from an intended lightning conductor into electrical circuits can occur due to capacitive coupling, inductive coupling, and/or resistance (i.e. insulation breakdown) coupling. Transfer 1

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impedance, due to loss of skin effect attenuation or shielding, can radiate interference and noise into power and signal lines. Transfer inductance (mutual coupling) can induce voltages into a loop which can cause current flows in other coupled circuits. 2.3 Behavior of Lightning. Absolute protection from lightning may exist in a thick-walled and fully enclosed Faraday Cage, however this is impractical in most cases. Lightning "prevention" exists only as a vendor-inspired marketing tool. Important new information about lightning may affect sensitive facilities. First, the average distance between successive cloud-to-ground flashes is greater than previously thought. The old recommended safe distance from the previous flash was 1..3 miles. New information suggests that a safe distance should be 6-8 miles (Lopez & Holle, National Severe Storm Center, 1998). Second, some 40% of cloud-to-ground lightnings are forked, with two or more attachment points to the earth. This means there is more lightning to earth than previously measured (Krider, IntI. Com. Atmospheric Electricity,1998). Third, radial horizontal arcing in excess of 20 m from the base of the lightning flash extends the hazardous environment (Sandia Labs, 1997). Lightning is a capricious, random, stochastic and unpredictable event. At the macro-level, much about lightning is understood. At the micro-level, much has yet to be learned. When lightning strikes an asset, facility or structure (AFS) return-stroke current will divide up among all parallel conductive paths between attachment point and earth. Division of current will be inversely proportional to the AFS path impedance, Z (Z = R + XL, resistance plus inductive reactance). The resistance term_ will be low assuming effectively bonded metallic conductors. The inductance, and related inductive reactance, presented to the total return stroke current will be determined by the combination of all the individual inductive paths in parallel. Essentially lightning is a current source. A given stroke will contain a given amount of charge (coulombs = amp/seconds) that must be neutralized during the discharge process. If the return stroke current is 50kA - that is the magnitude of the current that will flow, whether it flows through one ohm or 1000 ohms. Therefore, achieving the lowest possible impedance serves to minimize the transient voltage developed across the AFS path through which the current is flowing [e(t) = I (t)R + L di/dt)].. 3. LIGHlNING PROTECTION DESIGNS. . . Mitigation 9f lightning consequences can be achieved by the use of a de~ed systems approach, de'scribed below' in general teims. ' . , .. '" . 3.1 Air Terminals. Since Franklin's day lightning rods have been installed upon ordinary structures as sacrificial attachment points, intending to conduct direct flashes to earth. This integral air terminal design does not provide protection for electronics, explosives, or people inside modem structures. Inductive and capacitive coupling (transfer impedance) from lightningenergized conductors can result in significant voltages and currents on interior power, signal anp other conductors. Overhead shield wUesand mast systems located above or next to the structure are suggested alternatives in many circumstances. These are termed indirect air terminal designs. Such methods presume to collect lightning above or away from the sensitive structure, thus avoiding or reducing flashover attachment of unwanted currents and voltages to the facility and equipments. These designs have been in use by the electric power industry for over 100 years. Investigation into applicability of dielectric shielding may provide additional protection

2

where upward leader suppression may influence breakdown voltages (Sandia Laboratories, 1997). Faraday-like interior shielding, either via rebar or inner-wall screening, is under investigation for critical applications (US Army Tacom-Ardec). Unconventional air terminal designs which claim the elimination or redirecting of lightning (DAS/CTS - charge dissipators) or lightning preferential capture (early streamer emitters - ESE) deserve a very skeptical reception. Their uselessness has been well-described in publications such as: NASAlNavy Tall Tower Study; 1975, R.H. Golde "Lightning" 1977; FAA Airport Study 1989; T. Horvath "Computation of Lightning Protection" 1991; D. MacKerras et ai, IEE Proc-Sci Meas. Technol, V. 144, No.1 1997; National Lightning Safety Institute "Royal Thai Air Force Study" 1997; A. Mousa "IEEE Trans. Power Delivery, V. 13, No. 4 1998; International Conference on Lightning Protection - Technical Committee personal correspondence 2000; Uman & Rakov "Critical Review of Nonconventional Approaches to Lightning Protection", AMS Dec. 2002; etc. Merits of radioactive air terminals have been investigated and dismissed by reputable scientists (RH. Golde op cit and C.B. Moore personal correspondence, 2000). 3.2 Downconductors. Downconductor pathways should be installed outside of the structure. Rigid strap is preferred to flexible cable due to inductance advantages. Conductors should not be painted, since this will increase impedance. Gradual bends always should be employed to avoid flashover problems. Building structural steel also may be used in place of downconductors where practical as a beneficial subsystem emulating the Faraday Cage concept. 3.3 Bonding assures that unrelated conductive objects are at the same electrical potential. Without proper bonding, lightning protection systems will not work. All metallic conductors entering structures (ex. AC power lines, gas and water pipes, data and signal lines, HVAC ducting, conduits and piping, railroad tracks, overhead bridge cranes, roll up doors, personnel metal door frames, hand railings, etc.) should be electrically referenced to the same ground potential. Connector bonding should be exothermal and not mechanical wherever possible, especially in below-grade locations. Mechanical bonds are subject to corrosion and physical damage. HVAC vents that penetrate one structure from another should not be ignored as they may become troublesome electrical pathways. Frequent inspection and resistance measuring (maximum 10 milliohms) of connectors to assure continuity is recommended. 3.4 Grounding. The grounding system must address low earth impedance as well as low resistance. A spectral study of lightning's typical impulse reveals both a high and a low frequency content. The grounding system appears to .the lightning impulse as a transmission line where wave propagation theory applies. A considerable part of lightning's current responds horizontally when striking the ground: it is estimated that less than 15% ofit penetrates the earth. As a result, low resistance values (25 ohms per NEC) are less important that volumetric efficiencies. Equipotential grounding is achieved when all equipments within the structure(s) are referenced to a master bus bar which in tum is bonded to the external grounding system. Earth loops and consequential differential rise times must be avoided. The grounding system should be designed to reduce AC impedance and DC resistance. The use of buried linear or radial techniques can lower impedance as they allow lightning energy to diverge as each buried conductor shares voltage gradients. Ground rings connected around structures are useful. Proper use of concrete

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footing and foundations (Ufer grounds) increases volume. Where high resistance soils or poor moisture content or absence of salts or freezing temperatures are present, treatment of soils with carbon, Coke Breeze, concrete, natural salts or other low resistance additives may be useful. These should be deployed on a case-by-case basis where lowering grounding impedances are difficult an/or expensive by traditional means. 3.5 Corrosion and cathodic reactance issues should be considered during the site analysis phase. Where incompatible materials are joined, suitable bi-metallic connectors should be adopted. Joining of aluminum down conductors together with copper ground wires is a typical situation promising future troubles. 3.6 Transients and Surges. Electronic and electrical protection approaches are well-described in IEEEI100. Ordinary fuses and circuit breakers are not capable of dealing with lightning-induced transients.. Surge protection devices (SPD aka transient limiters) may shunt current, block energy from traveling down the wire, filter certain frequencies, clamp voltage levels, or perform a combination of these tasks. Voltage clamping devices capable of handling extremely high amperages of the surge, as well as reducing the extremely fast rising edge (dv/dt and di/dt) of the transient are recommended. Protecting the AC power main panel; protecting all relevant secondary distribution panels; and protecting all valuable plug-in devices. such as process control instrumentation, computers, printers, fire alarms, data recording & SCADA equipment, etc. are suggested. Protecting incoming and outgoing data and signal lines (modem, LAN, etc.) is essential. All electrical devices which serve the primary asset such as well heads, remote security alarms, CCTV cameras, high mast lighting, etc. should be included. Transient limiters should be installed with short lead lengths to their respective panels. Under fast rise time conditions, cable inductance becomes important and high transient voltages can be develoPed across long leads. SPDs with replacable internal modules are suggested. In all instances the use high quality, high speed, self-diagnosing SPD components is suggested. Transient limiting devices may use spark gap, diverters, metal oxide varistors, gas tube arrestors, silicon avalanche diodes, or other technologies. Hybrid devices, using a combination of these techniques, are preferred. SPDs conforming to the European CE mark are tested to a 10 X 350 us waveform, while those tested to IEEE and UL standards only meet a 8 X 20 us waveform. It is suggested that user SPD requirements and specifications conform to the CE mark, as well as ISO 9000-9001 series quality control standards. Uninterupted Power Supplies (UPSs) provide battery backup in cases of power quality anomalies...brownouts, capacitor bank switching, outages, lightning, etc. UPSs are employed as back-up or temporary power supplies. They sholl1d not be used in place of dedicated SPD devices. Correct Category A installation configuration is: AC wall outlet to SPD to UPS to equipment. 3.7 Detection. Lightning detectors, available at differing costs and technologies, are useful to provide early warning. Their sensors acquire lightning signals such as RF, EF, or light from Cloud-to-Cloud or Cloud-to-Ground or atmospheric gradients. Users should beware of overconfidence in detection equipment. It is not perfect and it does not always acquire all lightning all the tiem. Detectors cannot ''predicf' lightning. Detectors cannot help with "Bolt From The Blue" events. An interesting application is their use to disconnect from AC line power and to

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engage standby power before the arrival of lightning. A notification system of radios, sirens, loudspeakers or other communication means should be coupled with the detector. See the NLSI WWW site for a more detailed treatment of detectors. 3.8 Testing & Maintenance. Modem diagnostic testing is available to "verify" the performance of lightning conducting devices as well as to indicate the general route of lightning through structures. With such techniques, lightning pathways can be inferred reliably. Sensors which register lightning current attachments can be fastened to downconductors. Regular physical inspections and testing should be a part of an established preventive maintenance program. Failure to maintain any lightning protection system may render it ineffective. 4. PERSONNEL SAFETY ISSUES. Lightning safety should be practiced by all people during thunderstorms. Measuring lightning's distance is useful. Using the "FlashIBang" (FIB) technique, for every five seconds - from the time of seeing the lightning flash to hearing the associated thunder - lightning is one mile away. A FIB of 10 = 2 miles; a FIB of 20 = 4 miles, etc. The distance from Strike A to Strike B to Strike C can be as much as 5-8 miles. The National Lightning Safety Institute recommends the 30/30 Rule: suspend activities at a FIB of 30 (6 miles), or when first hearing thunder. Outdoor activities should not be resumed until 30 minutes has expired from the last observed thunder or lightning. This is a conservative approach: perhaps it is not practical in all circumstances. If one is suddenly exposed to nearby lightning, adopting the so-called Lightning Safety Position (LSP) is suggested. LSP means staying away from other people, removing metal objects, crouching with feet together, head bowed, and placing hands on ears to reduce acoustic shock from nearby thunder. When lightning threatens, standard safety measures should include: avoid water and all metal objects; get off the higher elevations including rooftops; avoid solitary trees; stay offthe telephone. A fully enclosed metal vehicle - van, car or truck - is a safe place because of the (partial) Faraday Cage effect. Used metal shipping containers, properly ventilated and shielded, are high recommended for outdoor workers. A large permanent building can be considered a safe place. In all situations, people should avoid becoming a part of the electrical circuit. [Benjamin Franklin's advice was to lie in a silk hammock, supported by two wooden posts, located inside a house.] Every organization should consider adopting and promulgating a Lightning Safety Plan specific to its operations. An all-encompassing General Rule should be: "If you can hear it (thunder), clear it (evacuate); if you can see it (lightning), flee it." 5. CODES AND STANDARDS. In the USA there is no single lightning safety code or standard providing comprehensive assistance. US Government lightning protection documents should be consulted. The Federal Aviation Administration FAA-SID-019d is valuable. The IEEE 142 and IEEE 1100 are suggested. Other recommended federal codes include military documents MIL HDBK 419A, Army PAM 385-64, NAVSEA OP 5, AFI 32-1065, NASA SID E0012E, MIL SID 188-124B, MIL SID 1542B, MIL SID 5087B, and UFC 3-570-01. The DOE M440.1-1 and the British Code BS 6551 are helpful. The German lightning protection standard for nuclear power plants KTA 2206 places special emphasis on the coupling of overvoltages at instrument and control

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cables. The International Electrotechnical Commission IEC 62305 series for lightning protection is the single best reference document for the lightning protection engineer. Adopted by many countries, IEC 62305 is a science-based document applicable to many design situations. Too often ignored in most Codes is the very essential electromagnetic compatibility (EMC) subject, especially important for explosives safety and facilities containing electronics, VSDs, PLCs, and monitoring equipment. 6. CONCLUSION. Lightning has its own agenda and may cause damage despite application of best efforts. Any comprehensive approach for protection should be site-specific to attain maximum efficiencies. In order to mitigate the hazard, systematic attention to details of grounding, bonding, shielding, air tenninals, surge protection devices, detection & notification, personnel education, maintenance, and employment ofrisk management principles is recommended. 7. REFERENCES. 7.1 International Conference on Lightning Protection (lCLP) Proceedings, Avignon (2004), Cracow (2002), Athens (2000), Birmingham (1998), Florence (1996). 7.2 IEEE SID 142-1991 Grounding of Industrial and Commercial Power Systems. 7.3 IEEE SID 1100-1999 Powering and Grounding Electronic Equipment 7.3 IEEE Transactions on Electromagnetic Compatibility, Nov. 1998 7.4 National Research Council, Transportation Research Board, NCHRP Report 317, June 1989 7.5 International Electrotechnical Commission (lEC), International Standard for Lightning Protection. See: http://www.iec.ch 7.6 Gardner RL, Lightning Electromagnetics, Hemisphere Publishing, NY NY 1991 7.7 EMC for Systems and Installations, T. Williams and K. Armstrong, Newnes, Oxford UK, 2000. 7.8 NATO STANAG 4236, Lightning Environmental Conditions, 1995. Note: Rev. 2005. Permission to copy and to re-print this paper is freely given. Please credit NLSI as the original author. The National Lightning Safety Institute is a non-profit, non-product independent organization providing objective infonnation about lightning safety issues. See the NLSI Website at: www.lightningsafety.com

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ATTENTION TO DETAIL For aviation, communications, explosives, military, nuclear, process control and other critical facilities, attention to very detailed lightning protection cannot be overstated. Conformity to EMC - electromagnetic compatibility - issues is very important. A very good source of EMC information, available at no cost via the Internet, is available to readers at:

www.compliance-club.com/archivel/OOl018.html This is Chapter 5 - Lightning and Surge Protection from the book "EMC for Systems and Installations" by Eur Ing Keith Armstrong C.Eng MIEE MIEEE.

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INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter Nine

INTERNATIONAL VIEW OF UNCONVENTIONAL AIR TERMINALS SUCH AS "ESE" AND "CTSIDAS"

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Shortly after Franklin's 1752 lightning rod inventio~.competing vendors promoted different designs. Some had three points. Some had. five points. Salespeople were known to have told lightning rod users that an annual return visit, at additional cost, was needed to file down the points to maintain sharpness Or the rods would not work.

Today there are vendors .calling their unconventional designs "Early Streamer" (ESE) air tenninals and "Dissipation Array Systems" (DAS) and "Charge Transfer 8yste1T1$" (CTS). Literature describing the merits of such ptoductsmake claims of perfection. Comparisons to accepted and conventional designs --- Franklin Rods and free-standing masts and overhead shield wires --- make the ESEIDAS/CTS products attractiveatfrrst glance. But behind the P$ueo.o-scientific language lies simple advertising exaggeration. We. provide some background information for reader education.

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PEER-REVIEWED TECHNICAL PAPERS ON CTSIDAS/ESE DESIGNS Experimental study on lightning protection performance of air terminals Lee, J.B, Myung, S.H. Cho, Y.G. Chang. S.H. Kim. J.S. KiI, G.5. Korea Eleclrotechnol. Res. lnst.. Changwon, South Korea This paper appears In: Power System TtcbOQlogyl_~,Q,PZ,.PI9.Ce.• dlo.g••. P,QW,tJ:CO(l 2,002 .. lntematlooal Confere.flCQ 0.0 Publication Date: 13·17 Ocl. 2002 Volume: 4 On pagels): 2222 • 2226 volA Number of Pages: 4 vol. 2691 ISSN: Digilal Object Identifier: 10.1109/1CPST.2002.1047177 Posted online: 2002·12·1017:23:34.0 Abstract There are claims that ESE (early streamer emission) air terminals offer a vastly increased zone of protection over that of tradilionallightning rods by causing the early emission of an upward streamer/leader and In contrasl 10 ESE, multipOint OAS (dissipation array systems) eliminate Ilghlning stroke to utilities by generating the same polarity charges to cloud charges. This paper deals with the results of • comparative tesl of a particular type of ESE al( terminals and DAS wilh a simple rod conducted in til, KERI HV laboralory, which include lightning Impulse voltage tesls, flashover direction testa and corona emission current mealur,menta. Results from Ihese tesls show a complelely random acattering of characteristics to the conventional and special air terminals under Identical electrical and geometrical condllions. Allo the characteristics of special air terminals are not ,upenor to a SImple rod for lightning and switching Impulse vollagea.

Experimental validation of conventional and nonconventionallightning protection systems Rison. W. Electr. Eng. Dept, New Mexico lnst of Min. &Techno!., Socorro, NM. USA This paper appears in: Pow9.rEngln.terlng So(;I9.N~:l~n_er.l Meeting, 2003, I.EEE Publication Date: 13·17 july 2003 Volume: 4 On pagels): 2200 Vol. 4 Number of Pages: 4 vol. 2666 ISSN: Digital Ob/eclldenlifier: 10.1109/PES.2003.1270959 Posted online: 2004-03-08 14:01:20.0 Abstract Three types of lightning protectlonsystems are in common use today: conventional syslems, charge transfer systems, and systems based on early .Irumer emission air terminals. There is a wealth of empIrical dala validating the effectiveness of conventional lightning prottctlon systems installed in accordance with recognized standards. Field .tudles of charge tran.fer system. show that they do not prevent lightning slrikes as has been claimed. Studies of earty streamer emlllion air terminals show that their performance in the field IS similar to that of conventional sharp-poinled air terminals, and they do not have 8 greatly enhanced zone of protection as has been claimed.

The basis of conventional lightning protection systems Tobias, J.M, U.S. Army Commun.-Electron. Command, Fort Monmouth, NJ. USA This paper appears in: 1nQ.u.$tJYApp,lI.cl!tIQns.IE~e.Trl!n$ac:;tlons Publication Date: July·Aug, 2004 Volume: 40 , luue: " On page(s): 958 • 962 ISSN: 0093-9994 Digital Object Identifier: 10.110errlA.2004,831277 Posted online: 2004-07·1911:11:01.0

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Abstract The study of lightning protection system design encompasses nearly 300 years, Yel, many of the onglOal sources for common design practices used today remain obscure, ThIS paper traces the significani developmenl$ in lightning protection from the late 1700s to the modern day. EmphaSIS Is placed on significani events in the history that have had direct consequences in the establishment of deSIgn practices for lightning protection. It Is also demonstrated that many of the design practicas used today were subject 10 SIgnificant scrutiny and empirical qualification. Our lnlent IS to familiarize Ihe student ot lightning protection deSign with Ihe originallilerature, testing. and other noteworthy contributions to the deSIgn of effective lightning protection systems.

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From: To: Sent: Attach: Subject:

"Hartono" "LP/PQ" Tuesday, February 10 20045:11 AM KL strike 2.JPG; KL strike 3.JPG; KL strike 4.JPG;.KL strike 5.JPG; KL strike 1.JPG [LP/PQ] Safety around buildings during thunderstorms 1

In message 693 (June 8, 2001), I posted a picture ofa building with its

corner of the roof struck by lightning. A similar incident occurred last Friday evening in a suburb ofKuala Lumpur. The apartment building was installed with two French made ESE air terminals. The triangular gradient wall at the end of one ofthe roof ridges was struck by lightning and badly damaged, sending the concrete debris falling onto a sub-compaet car and a motorcycle on the ground below. Fortunately, no one was hurt since there was a thunderstorm with plenty of lightning and heavy rainfall at that time and no one was outside. The damaged wall was made of light-weight concrete which probably explains the extensive damage done by the lightning strike. The concrete can be easily broken with a small hammer. The air tenninal is about 30m away from the damaged wall. Based on the INERIS report (pg 18/46) by P. Gruet, the ESE model is called SateHt.

175

From: To: Cc: Sent: Subject:

"BUlent Ozince" Monday, February 16, 2004 4:42 AM [LP/PQj lightning protection of radar sites

Dear Friends, Last week in IstanbuilTurkey, there was a severe winter storm. At night we heard in the news that ligh~ng . struck one ofthe radar sites related to weather forecasting. This radar site was constructed 1 month ago and was protected with ESE terminals. According to the official report, lightning struck 7 times that night and caused big holes in the radome and damage to the electronic devices. Once again, ESE terminals didn't work. The damage is too much and the people are getting angry. I hope you could help me to find a document regarding correct protection of radar sites by Franklin rods. Best Regards BUlent Ozince Electrical Engineer

176 AAGE E. PEDERSEN Phone: +45 39 65 1710 Fax: +45 39 68 33 38 Mobil: +45 22 127032

Asc. Professor, Docent Staenget1A

OK 2820 Gentofte Denmark

E~mail:

aa-e-p@get2neldk

2004.01.21 Information for whom it may concern.

THE RESULT OF: A COURT CASE CONCERNING ESE DEVICES. (THE SHORT VERSION)

In connection with the N.FPA's rejection of ESE draft standard 781, three ESE companies (Heary Bros. Lightning Protection Co., Inc., lightning Preventor of America, Inc., and the National lightning Protection Corp.,i of which the two first mentioned have merged) sued a lightning protection trade association and two lightning protection companies (Lightning Protection Institute, Thompson Lightning Protection Inc., and East Coast lightning Equipment, Inc.). The lawsuit, which was initiated in 1996, contained allegations of conspiracy, false advertising and product defamation regarding the advertised improved efficiency of ESE terminals compared to conventional Franklin rods. In October, 2003, the Federal District Court of Arizona summarily dismissed the lawsuit. The dismissal was largely based on the fact that the ESE vendors presented no admissible evidence at all to support their claims. Additionally, the Court granted a favorable ruling to a counterclaim against the ESE vendors. The ESE vendors were convicted of falsely advertising the claimed increase in efficiency of ESE rods in comparison to conventional Franldin rods. Significantly, the verdict rejected the ESE vendor's claims that their ESE terminals' compliance with various ESE standards justified the advertised expanded zones of protection for ESE devices. The Court found that the conformance with foreign ESE standards failed to prove claimed increased zones of protection for ESE rods. The Court found that the ESE vendor's claims are not supported by tests sufficiently reliable to support those claims and are therefore in violation of American "truth-in-advertising" laws.

THE FULL VERSION, cf. the homepage of the district court:

http://www.azd.uscourts.gov/azdlcourtoDinions.nsflOpinlons%20bv%20date?OpenView Date 2003.10.23 - CV 96-2796 PHX ROB, Heary Bros. Lightning Protection Co., Inc., et al. vs. Lightning Protection Institute, et al.

I The National Lightning Protection Corp. sells the well-known ESE device named Prevectron tram the French manufacturer Indelee, whereas Heary Bros. produce and sell their own ESE model.

176 AAGE E. PEDERSEN Phone: +45 39 6517 10 Fax: +45 39 68 33 38 Mobil: +4522127032 E-mail: aa-e-p@get2netdk

Asc. Professor, Docent Staenget1A OK 2820 Gentofte Denmark

2004.01.21 Information for whom it may concern.

THE RESULT OF: A COURT CASE CONCERNING ESE DEVICES. (THE SHORT VERSION)

In connection with the NFPA's rejection of ESE draft standard 781, three ESE companies (Heary Bros. Lightning Protection Co., Inc., Lightning Preventor of America, Inc., and the National lightning Protection Corp.,1 of which the two first mentioned have merged) sued a lightning protection trade association and two lightning protection companies (Lightning Protection Institute, Thompson lightning Protection Inc., and East Coast Lightning Equipment, Inc.). The lawsuit, which was initiated in 1996, contained allegations of conspiracy, false advertising and product defamation regarding the advertised improved efficiency of ESE terminals compared to conventional Franklin rods. In October, 2003, the Federal District Court of Arizona summarily dismissed the lawsuit. The dismissal was largely based on the fact that the ESE vendors presented no admissible evidence at all to support their claims. Additionally, the Court granted a favorable ruling to a counterclaim against the ESE vendors. The ESE vendors were convicted of falsely advertising the claimed increase in efficiency of ESE rods in comparison to conventional Franklin rods. Significantly, the verdict rejected the ESE vendor's claims that their ESE terminals' compliance with various ESE standards justified the advertised expanded zones of protection for ESE devices. The Court found that the conformance with foreign ESE standards failed to prove claimed increased zones of protection for ESE rods. The Court found that the ESE vendor's claims are not supported by tests SUfficiently reliable to support those claiins·and are therefore in violation of American "truth-in-advertising" laws.

THE FULL VERSION, ct. the homepage of the district court: http://mMt.azd.uscourts.gov/azdlcourtopinions.nsflOpfnlons%20by%20date?OpenView Date 2003.10.23 - CV 96-2796 PHX ROS, Heary Bros. Lightning Protection Co., Inc., et al. vs. Lightning Protection Institute, et al.

1The National Lightning Protection Corp. sells the well-known ESE device named Prevectron from the French manufacturer Indelee, whereas Heary Bros. produce and sell their own ESE model.

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A CRITICAL REVIEW OF NONCONVENTIONAL APPROACHES TO LIGHTNING PROTECTION BY

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ONVENTIONAL SYSTEMS. Properly designed conventionallightning protection systems ( for ground-based structures serve to provide lightning attachment points and paths for the lightning current to follow from the attachment points into the ground without harm to the protected structure. Such systems are basically composed of three elements: 1) "air terminals» at appropriate points on the stmctu.re to intercept the ligh~2) "down conductors" to carry the lightning current from the air terminals toward the ground, and 3) "grounding electrodes" to pass the lightning current into the earth. The three system components must be electrically well connected Many national and international standards descn'be conventional lightning protection sys-

terns (e.g.,NFPA 1997, hereafter NFPA 780), and the efficacy of the conventional approach has been well demonstrated in practice (e.g.) Harris 1843, 140-156; Symons 1882; Lodge 1892; Peters 1915; Covert 1930; Keller 1939; Szpor 1959). The classic text on the conventionallightning protection of structures is Golde (1973). The theoretical justification of the conventional approach is fairly crude, in part due to our incomplete understanding oflightnings attachment to ground-based objects. Hence, the fact that conventional systems have a history ofsuccess in preventing or minimizing damage to structures is the primary justification for their use. It is nevertheless instructive to review the current understanding ofthe lightning processes, this understanding being consistent with the experience gained from the use of conventional structural lightning protection systems. The lightning stepped leader, the process that initiates a cloud-to-ground flash, begins in the eloud charge region (near 5-km height in temperate summer for the typical flash that lowers negative charge) and propagates toward Earth at a typical average speed of 105 m S-I. The charge on the leader channel (effectively drained from the cloud charge source) produces an electric field near the earth·s surface that is enhanced by objects projecting above the surface such as trees and grounded air terminals on struc-

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the leader i'S lims tQ hnndre~j!, ih is electric fidd l)c,sQtne:, iatgt: pr'(}lhlCe dectriml breakdown f;i?'tW"et?l1

,mdthe ground or between the and one of the elevated Such electrical hreakdown, which Qccurs in laboratory gap electric field of a few 11llI1d!'ul Chowdhurl 20(0), involves nne or more up,w;lf(l>C![mljectingle~:lXj­ crs ent;;trmtmg from tht, ground or One of these leaders meets one of the branches of the downward,propa. gating JearJt'f and establishes II path between cloud and gmlWtt Figure I shows a slrnpiilied picture nflightniog attachment to tlstnlct'urt: that is protected bjf cwrWf'ntiloua! lightning pf()teclion sy·s. tern cmpJnying air terminals in the limn (lfljghtning rmk "Vve om,' the models iJrvo,!w::{j

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fiG. I. The lightning attadtrneflt pr~c~$;!1~(~)i:he stepped leader descends to witbin about I no m qf iIi housl'! with (onventimml lightning protel:t1on (not t6 scale), (b) upward leaders laundled from II.gh'tnlngrlXls and neat'by tree, and (c) rormectiol1l11adc between t>l'l.e branch of the downward.moving stepped IlClader .litH.! one upward-moving leader thepa-til for current flow of the. retUrf1 stroke.

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the ground. the so-called rolling sphere method (e.g.,

Lee 1978; NFPA 780). The locus ofall points traversed by the center of the rolling sphere forms the imaginary capture surface referred to above. Those points that the rolling sphere touches can be struck. according to this approach; and pointswhere the sphere does not touch cannot be. Figure 2 illustrates the rolling sphere approach. In this approach, any objects beneath the surface shown by the dashed lines in Fig. 2 cannot be struck (are protected), and any groundbased objects projecting through that surface can be struck (are unprotected). In the commonly used rolling sphere approach, the striking distance is assumed to be the same for any object projecting above the earth's surface or for the earth itself. There are varia- FIG. 2.. Zone of protection for a single mast ofheight H, tions of this technique in which the assumption of as detennined by the roBing sphere method. Adapted equal striking distances for different objects and for from NFPA 780. the earth is replaced by the assumption of different striking distances for objects of different geometry (e.g., Eriksson 1987a,b). One can use the rolling conservative approach to protection; that is, more air sphere method with constant assumed sphere radius terminals are required, as can be inferred from Fig. to position air terminals on a structure so that one of 2, and lightning discharges with lower peak currents the terminals, rather than a roofedge or otherpart of are intercepted by the air terminals. According to the structure, initiates the upward leaderthat connects some standards, a wire mesh covering the top ofthe to the downward leader; that is, the striking distance structure may playthe role ofthe airterminals. (Note to an air terminal is reached by a downward-propa- that the rolling sphere method would predict that gating leader before the striking distance to a portion lightning can attach to the structure between the ofthe protected stnlcture is reached. metal mesh conductors unless the mesh is elevated Assuming a distribution ofcharge along the leader above the top of the structure.) For example. lEe channel and a value ofbreakdown field, one can re- (1993) states thatameshsize of15m xIS mis equivalate the striking distance to the charge on the stepped lent to protection with lightning rod air terminals leader channel and then using the observed correla- designed for an assumed 45-m striking distance. tion between the charge and peak current of the re- Apparently, the specified relationship between mesh sultant return stroke (Berger et al. 1975) one can find size and striking distance is a matter of experience the relationship between the striking distance and the rather than theory. return stroke peak current. Given allthe assumptions involved, this.relationship is necessarily crude. Ac- NONCONVENTIONAL SYSTEMS. With this cording to Illtemational Standard lEe 61024-1 (lEC brief background in COI\ventionallightning.protec.1993) 99% of s~g distances exceed 20 m. 20 m. tion. Wl: now. and in th,e follOwing sections, consider being associated with a first stroke peak current of nonconventional approaches to lightning protection. about3·kA; 91% eXceed 45 m. asSociated with about Noncon'Ventionallightning protection sch~mes for 10 kA; and 84% exceed 60 m, associated with about ground-based structures generally fall into one oftwo 16 kA. Clearly, these are very rough estimates. The classes: 1) "lightning elimination" or 2) "early typical first stroke peak current is near 30 kA (Berger streamer emission." Nonconventional systems using et al. 1975) fur which various calculated striking dis- these two techniques are commercially available untances, using different assumptions on breakdown der a variety of trade names and are claimed to be parameters, are generally between 50 and 150 m superior to the conventional lightning protection (Golde 1977). consistent with the typical observed described above. The primary intent of this paper is striking distances reviewed byUman (1987, 99-109, to review the literature on the two nonconventional 205-230). For the placement ofair terminals in a con- approaches in conjunction with the pertinent lightventionallightning protection system, NFPA 780 rec- ning literature so that we can examine the hypothesis ommends adopting a striking distance of 46 m. that systems employing these techniques function as Smaller assumed striking distances result in a more advertised. that is, are superior to the conventional AMERICAN METEOROLOGICAL SOCIETY

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lechnique described in the sedion "Cmwentionjj Systems." We will show that the suggested advan tages of the nonconventjonal methods over the woventional technique are not $'Upported by the available experimental data or by theory. This conclusion is consistetlt with that ofGolde (1977) who reviewed the nonconventlonal approaches to lightning protection based on the information availahle at the time of his

writing. LIGHTNING ELIMINATION. General information and theory. The primary claim of the proponents of lightning elimination systems (which more recently have been called "charge transft~r systems") is that those syi>1emS produce<::onditions underwhich lightning either does not occur or cannot strike the pro· tected structure, as opposed to the conventional approach ofintercepting the imminent lightning strike and rendering it hltrmless by providing a nondestruc· tive path for the lightning Cllrrent to flow to ground. Lightning elimination systems include one or more devated arrays ofsharp points, often simiiarto barbed .....' ire, that are installed on or near the structure to be pr rays are connected to grounding ell' conductors as in the case ofcon·· ventionallightningprotection systems. The principle ation systems., accord-

dous effect;; of lightning (Cohen 19(0). Hughes (1977) states that a patt>nl for a multiple. point s~'stem was issued in 1930 to J. ~t Cage of L.os Angeles, Cali· fornia. The patent describes the use of point·bearing wires suspcnded from a sleel tower to protect petroleum storage tanks (rom Hghtning< A similar system, commonly referred to as a dissipation array systt'm (D,'\8) or a charge transfer system (C1'5), has been cmnmerciaHy avaihlble since 1971 although the pwt!· Het name and the name ofthe companytha! markctt'u it have changed over time (Carpenter 1977; Carpenter and Auer 1995). Most lightning elimination systems were originally designed for t.a11 cnmmunicatinn tuwers, hut recently they have been applied to a wide ra nge ofsystems and facilities including electrical substations, power lines, and airports. Carpenter and Auer (I995) give their view oithe operation of the (lissipatiol1 array marketed hy the leading manufacturcL This array, schelll
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hased on his sinall-scale lahor
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and the storm." According to Carpenter and Auer ted from a dissipation array, there will be a reduc(1995), "many consider the space charge the primary tion of the local electric field near the array and an protective mode, saying its function is much like a enhancement of the field at a distance from the arFaraday shield providing a second mode of protec- ray of the order of the size of the array, the magnition." Carpenter and Auer (1995) do not support their tude of this effect depending on the magnitudes of description of the principle of operation of dissipa- the corona current and the wind. The corona current tion arrays with quantitative arguments. In a com- is self-limitingin the sense that the corona-produced ment accompanying the paper ofCarpenter and Auer charge shields the array and therefore reduces the (1995), Zipse (see also Zipse 1994) points out that electric field that drives the corona discharge. The trees and blades of grass generate corona discharge, negative cloud charge that is the source of most often exceeding that of dissipation arrays, without cloud-to-ground lightning is located at 5 km or so apparently inhibiting lightning. This same point has in temperate regions and has a value ofsome tens of been previouslymade by Zeleny (1934) and by Golde coulombs. During the 10 s ofcloud-charge regenera(1977). Zeleny (1934) observed that "during a stonn tion, charges emitted by the array may move a vernin Switzerland the top of a whole forest was seen to cal distance of up to 150 m and, if there is, for extake on a vivid glow, repeatedly, which increased in ample, as m 5""1 horizontal wind, horizontally about brilliance until a lightning bolt struck." Ette and Utah 50 m. A vertical wind would also have an effect (I 973) reported that the average corona currents from (Chahners 1967,239-262). As the ions move away a metal point and from palm trees of comparable from the array) their shielding effect is reduced, and height were similar (see below). Interestingly, Zipse the electric field near the array may increase. The (2001) has referred to the conclusions ofZipse (1994) effect of corona on upward-lightning leader initiaas "erroneous," stating that corona on trees is inca- tion in a slowly varying thundercloud electric field pable of producing as much charge as the charge has been theoretically studied by Aleksandrov et al. transfer system. Zipse (2001) also states that the light- (2001). However, they did not consider the practiDing elimination system may fail to eliminate light- caDy important (from the lightning protection point of ning, and, in this case, it acts as a conventional light- view) case of the initiation of an upward-connecting ning protection system. leader in response to the approaching downward We now estimate the value of corona-produced leader. If the rapidly varying electric field associated charge and the distance over which such charge can with the approaching stepped leader aets to overcome move during the typical cloud-charge regeneration the shielding effect of corona space charge near the time, of the order of 10 s (e.g., Chauzyand Souia grounded object, the resultant upward-connecting 1987), between lightning discharges. In the absence leader will escape the space charge cloud and interofa downward-propagating leader:» both the charged cept the descending leader:» as discussed in the seclight ions and the heavier aerosol ions formed byion- tion "Conventional systems." According to the'Draft Standard regarding charge particle attachment in the humid air near the points ofa dissipation array move in response to 1) the e1ec- transfer systems submitted to the IEEE (IEEE P1576/ tric field ofthe cloud charge, other space charg~ and D2.012001) by their proponents, a 12-poin~ array will the charge on the ground arid on grounded objects; and ' , produce a corona cuttent of 700 pA :under a thunder,2) the' Wind. Typical electric fields near the ground storm.: Zipse (2001) ~rted on a corona current of " under thunde~stormsse1domexceed 10 kV m-1, 500 pA from four sets of three points ,installed on'a, while 100 or so above the groUnd the fields can be 2o-m pole, apparently measured in the absence of near 50 kV m-1 (Chauzy et al. 1991; Soula and Chauzy lightning in the immediate vicinity of the pole. It is 1991). The mobilities of atmospheric light ions in not clear who performed these measurements or how. electric fields oII0 to 50 kV m-1 are in the range of1 More important) it is not clear if the reported value to 3 X 10-4 m 2 V-I 5-1 (Chauzy and Renneia 1985; is average or peak current. The actual corona current Chauzy and Soula 1999). Heavier ions move two or- from a large number of points depends on the spacden ofmagnitude more slowly. Thus, above the field ing between the, pq~ts since the corona from each eiUiancement region of the dissipation array, up- point reduces the electric field at adjacent points and ward-directed drift velocities of light ions mayap- hence their individual current output (e.g., Chahners proach 15 mS-I. Horizontal wind speeds of several 1967,239-262). Thus, manycl~selyspacedpoints do meters per second are common under thunderclouds not necessarily emit more corona current than sevso that the light ions funned by corona discharge will eral wen-separated points. Ette and Utah (1973), in also move horizontally. If sufficient charge is emit- perhaps the best study to date ofcorona current from

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~ grounded objects under thunderstorms, found the average corona current from a 10-m metal point to be about 0.5 pA, while palm trees of 13- and 18-m height produced between 1 and 2 pA. IEEE P15761 D2.01 (2001) states that the appropriate array design should consist ofa sufficient number ofcorona points so that the array will emit a charge equal to that on a stepped leader:. apparently taken as 5 C, in a time of 10 S, the cloud-charge regeneration time noted in the previous paragraph. If, for example, a current of roughly 1rnA were emitted from a 10-point array, as stated in IEEE P15761D2.0 (2001) without adequate experimental evidence, then a charge of10-2 C would flow into the air in the 10-s charge regeneration time. To emit 5 C to the air in 10 S, the arraywould require 5000 well-separated points. According to Zipse (2001), a typical array contains 4000 points, although usuallylocated in close proximityto each other. There are no well-documented data in the literature on corona current that could be extrapolated to a large array and certainly no evidence that several coulombs of corona charge can be released in 10 s or so from an array of any practical dimensions. Golde (1977) has suggested that dissipation arrays installed on tall structures, typically towers, will inhibit upward lightning flashes (initiated by leaders that propagate upward from the tall structure into the cloud) bymodifying the needlelike shape ofthe structure tops to a shape that has a less pronounced fieldenhancing effect. While this suggestion is not unreasonable, there are no measurements to support it Upward lightning discharges occur from objects greater than 100 m or so in height (above flat terrain) and most lightning associated with objects of height above 300 m or so is upward (Eriksson 1978; Rakov and Lutz 1988). In this view, dissipation arrays would inadvertentlyreduce the probability ofoccurrence of these upwardflashes; which repreSent the majority of flashes to very tall towers.- The upward flashes contain initial conttDuoUs Current and often contain'subsequent strokes similar to those in nonnal cloud-toground lightning (e.g., Uman 1987; Rakov2001), thus having the potential for damage to electronics. It is important to note that damage to electronics can be prevented or minimized by the use ofso-called surge protection, as opposed to the structural protection that1s the subject ofibis p~per. The -reduction ofthe electric field at the tower top due to the increase of its effective radius ofcurvature, disOlssedabove; does not require either the release of space charge to provide shielding or the dissipation of cloud charge. The view ofGolde (1977) has been expanded on byMousa (1998), who- argues that the suppression of upward 18141 BAnS- DECEMBER 2002'

flashes will be particularly effective for towers of 300-m height or more and that dissipation arrays will have no effect whatsoever on the frequency ofstrikes to smaller structures such as power substations and transmission line towers. Mousa (1998) has reviewed lightning elimination devices that are claimed to employ corona discharge from multiple points. Monsa (1998) shows drawings of six so-called dissipaters produced by five different manufacturers. One of these, the umbrella dissipater, has been described by Bent and Llewellyn (1977) as about 300 m ofbarbed wire wrapped spirally around the frame of a 6-m-diameter umbrella. The barbed wire has 2-cm barbs with four barbs separated by 90° placed every 7 em along the wire. The umbrella dissipater described by Bent and Llewellyn (1977) was mounted on a 30.5-m tower in Merritt Island, Florida. Mousa (1998) also describes a ball dissipater, a barbed power line shield wire, a conical barbed wire array, a cylindrical dissipater, a panel dissipater (fakir's bed of nails), and a doughnut dissipater. Mousa (1998) also discusses the extensive grounding procedures used by the manufacturers and installers oflightning elimination devices (see also Zipse 2001). The leading manufacturer (see Carpenter and Auer 1995) typical1yuses a buried ground ring (the ground current collector in Fig. 3) that encircles the structure with I-m-long ground rods located at 100m intervals around the ring. In poorlyconduetingsoil, the same manufacturer uses chemical ground rods ofits own design, hollow copper tubes filled with a chemical that leaches into the soil in order to reduce the soil conductivitysurrounding the grounding system. In addition to the structural lightning protection, this same manufacturer highly recommends the installation of surge protective devices on sensitive electronics at the same time that the dissipation array syste.mis iilstalled.-Carpenter (1971)lists many customers who report a cessation ofJight,ning..caused damage after installation of the system he manufactures (presumably including'both stroc- tura1 and surge protection components). However, as Monsa (1998) points out, most lightning elimination systems can, in principle, provide conventional lightningprotection (see also Zipse 2001); thatis, they can intercept a lightning strike and direct its current into the ground without damage to themselves or to the protected structure if there is sufficient coverage'of the stiueture by arrays (air terminals). Further, damage to electronics within the structure can be eliminated orminimized bywayofthe installation ofsurge protective devices and good groundin~ this protective effect having nothing to do with the structural protection (lightning elimination) component

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Observations; We summarize now the records of ob- they were common before. Apparently, the presence seIVed lightning strikes to dissipation arrays. In 1988 of the dissipation arrays neither prevented the lightand 1989 the Federal Aviation Administration (FAA) ning strikes nor changed the characteristics of the conducted studies of the performance of dissipation lightning stroke current, while the equipment damarrays relative to conventional lightning protection age was eliminated by means ofimproved surge prosystems at three Florida airports (FAA 1990). An tection and grounding. umbrella dissipation array installed on the central tower ofthe Tampa International Airport was struck EARLY STREAMER EMISSION. General informaby lightning on 27 August 1989, as shown by video tion and theory. The attractive effect of an air teoniand current records (FAA 1990, see appendix E). nal would be enhanced by a longer upward-connectCarpenter and Auer (1995) have disputed the find- ing leader (e.g., Rakov and Lutz 1990); the longer the ings of FAA (1990), and Mousa (1998) has reviewed leader, the greater the enhancement. Early streamer the attempts ofthe dissipation array manufacturer to emission (ESE) systems are similar to conventional suppress FAA (1990). Additional lightning strikes to structural lightning protection systems except that dissipation arrays are described by Durrett (1977), they employ air terminals that, according to their Bent and Llewellyn (1977)~ and Rourke (1994). The proponents, launch an upward-connecting leader to former two references describe strikes to towers pro- meet the descending-stepped leader at an earlier time tected by dissipation arrays at the Kennedy Space than would a conventional air terminal having simiCenter, Florida, and at Eglin Air Force Base, Florida, lar geometry and installed at the same height. This respectively. Rourke (1994) considers lightning earlierinitiated upward-connecting leader is claimed strikes to a nuclear power plant The plant was struck to be capable ofextending to significantly longer disby lightning three times in two years, 1988 and 1989, tances and, as aresult, to provide a significantly larger before having dissipation arrays installed. After dis- zone ofprotection than theupward-connecting leader sipation array installation, the plant was also struck from a conventional air terminal ofthe same height If three times in two years, 1991 and 1992. Rourke (1994) this be true, it would follow that a single earlystreamer notes that "there has been no evidence that lightning emission air terminal could replace many convendissipation arrays can protect a structure bydissipat- tional air terminals, which is the primary claim ofESE ing electric charge priorto the creation ofthe lightning." proponents. Without this claim, ESE systems would Kuwabara et al (1998) reported on a study of dis- be indistinguishable from conventional systems. There are several types ofearly streamer emission sipation array systems that were installed in summer 1994 atop two communication towers on the roof of systems. All employ specially designed air terminals a building in Japan. Kuwabara et al (1998) state that that are claimed to create enhanced ionization near the dissipation array "was not installed per the the air terminal, either by employing radioactive manufacturer's recommendations as a result of the sources, by a special arrangement ofpassive electronbuilding construction conditions in Japan.» ics and electrodes that facilitate the electrical breakMeasurements of lightning current waveforms dur- down ofsmall spark gaps in a high electric field ofthe ing strikes to the towers were made prior to the in- approaching stepped leader, or by the applicatio~ of . stallatiO,D of dissipation arrayS, from winter '1991 ~ an externa1,voltage,~ the ~r.tenn,inalfr:om~ m~­ winter 1994, and after the installation, from winter made source. The first earlystreamer emission devices 1995 to winter 1996. Additionally, six direct Strikes were sO-caned mmoactive rods, rods with radioactive' to the towers with the arrays "installed Were photo- .' material placed on them, although when these were graphed between December 1997 and January 1998. initially marketed the term early streamer emission Twenty-six lightning current waveforms were re- had not been coined. According to Baatz (1972), in corded in the three years before installation of the 1914 the Hungarian physicist L Szillard first raised dissipation arrays and 16 in the year or so after instal- the question ofwhether the attractive effect ofa lightlation. The statistical distribution ofpeak currents was ning rod could be increased by the addition of a raessentially the same before and after installation. Es- dioactive source. , Various tests in·the field and, the laboratory have timated pe~ currents vaded from 1 to·lOO kA. Kuwahara et al. (1998) state that after installing the shown that~ under thunderstorm conditions, there is dissipation ar!ays, improving the grounding,. and little or no difference between the action of a radioimproving the surge protection in summer 1994 "mal- active rod and that of a similarly installed convenfunctions of the telecommunications system caused tional rod ofthe same height (e.g., Miiller-Hillebrand bylightning direct strike have not occurred," whereas 1962b; Baatz 1972). Heary et al. (1989) published ,

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laboratory tests purporting to show the superiority of stepped leader that initiates the usual cloud-ta-ground radioactive rods over conventional rods, but, in dis- lightning flash) at an earlier time, by a time interval cussions accompanying that paper, five researchers ~t, than do conventional air terminals. They claim (G. Carraca, I. S. Grant, A. C. Liew, C. Menemenlis, that this earlier initiated leader occurs in a smaller and A. M. Monsa) use the paper's results to argue oth- electric field than is required for the initiation of a erwise. Mackerras et alA (1987) have given examples leader by a conventional rod. Further, they translate of the failure of radioactive lightning protective sys- the claimed time advantage iit into a length arlvanterns in Singapore where, at the time of their study, tage, l1L, for the earlier initiated leader via tiL = vAt, over 100 such systems were installed. Golde (1977) where v is the speed ofthe upward-connecting leader. cites the failure of a radioactive lightning rod to pre- ESE proponents assume that the speed ofthe upwardvent lightning from knocking the papal crest off connecting leader is of the order of 106 m S-1 (e.g., Bernini Colonnade at the Vatican on 6 March 1976. French Standard 1995). This value ofleader speed is The crestwas located about 150 m from a 22-m-high arbitrary, since it is not supported by experimental radioactive rod that was supposed to protect it. data, as discussed next. The only existing measureSurveys of the ESE literature by van Brunt et al. ments of upward positive leader speeds in natural (1995; see also van Brunt et alA 2000) and Bryan et aI. lightning are due to McEachron (1939), Berger and (1999), commissioned by the U.S. National Fire Pro- Vogelsanger (1966,1969), and YokOYama et al. tection Association, were part ofan independent in- (1990). McEachron (1939) reported that upward posivestigation to determine if there should be a U.S. tive leaders initiated from the Empire State Building national standard for early streamer emission systems propagated at speeds ranging from 5.2 x 10· to 6.4 x such as the NFPA 780 for conventional systems. lOS m S-I, with the lengths of individual leader steps Based on these surveys, NFPA concluded that there ranging from 6.2 to 23 m. Berger and Vogelsanger was "no basis for the claims ofenhanced protection" (1966, 1969) measured speeds between 4 X 1()4 and ofESE systems relative to conventional systems and, about 106 m S-1 for seven upward positive leaders, with hence, no basis for issuing a standard for ESE systems. the individual leader step lengths ranging from 4 to Nevertheless, there are presently both a French Stan- 40 m. Further, for four ofthe seven leaders Berger and dard (1995) and a Spanish Standard (1996) for the Vogelsanger (1966) measured speeds ranging from 4 laboratory qualification of early streamer emission to 7.5 x 104 m S-1 and step lengths from 4 to 8 m at systems for lightning protection ofstructures. Strong altitudes rangingfrom 40 to 110 m from the tower top, arguments can be made that no laboratory spark test where a connection between a downward leader and can be extrapolated to describe the case of natural an upward-connecting leader would be expected. lightning. For example, the length ofmdividualsteps Yokoyama et alA (1990) measured, for three cases, in the lightning stepped leader is ofthe order oftens upward leader speeds between 0.8 to 2.7 x lOS m S-I. of meters, a distance considerably larger than the They show figures in which the stepping ofboth the length of labor~t~ry spark ga.ps, of ~e, order, of a , upward and d~wnwardleader: if) ,apparent. Yokoyama meter. specified, to test and certify ESa systems [e.g., ,et at (i990) report that the lengths' of.the u~d­ Fr~nch Standard (1995) that requires a gap no connectingleaders whose speeds theymeasuredwete smaller than 2 m with the air t~rminalbeing between from some tens of meters to over 100 m at the time 0.25 and 6.5 times the gap size]. It is not likely that that a connection was madewith the downward-movone can adequately simulate the natural-lightning ing stepped leader. Their measurements are apparattachment process in a 2-m laboratory gap. As an- entlythe only ones ofthe speeds ofupward-connectother example, in natural lightning the downward ing leaders that actually connect to downward leaders negative leader from the cloud has a length ofmany below the cloud base, as opposed to upward positive kilometers while the positive upward-connecting leaders in upward flashes that enter the cloud. Interdischarge from the ground or from elevated objects estingly, positive upward-connecting leaders in labois generally much shorter~ some tens to hundreds of ratory spark experiments typically have speeds of ' meters long. On the other hand, in laboratory spark' 1()4 m S-I, an order of magmtude lower than typical studies intended to simulate lightning strikes to values in natpra}lightning and two orders ofmagnigrounded objects, positive leaders are always much tude lower than the 1()6 m S-1 assumedby ESE propOlonger than negative leaders.' nents (e.g., Berger 1992). Yokoyama et al. (1990) also ESE proponents argue that ESE air terminals emit reported on the speed of individual optical step for, ·a positive upward-moving ,connecting leader (in- mation,thisirrelevantm~mentbeingsometimes· tended to meet the downward-moving negative, referenced by ESE proponents in support of the

ar-

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bitrarily assumed value v = 106 m S-I for average upward-connecting leader speed, cited above. Mackerras et al (1997) and Chalmers et al. (1999) critically review the proposed ESE techniques. Both papers raise the important question of whether an upward-connecting leader, ifindeed launched by an ESE rod earlier than for a conventional rod, andhence launched in a lower electric field, is able to propagate in the required manner in this lower field. According to Mackerras et al (1997), once the upward-connecting leader propagates into the space remote from the air terminal, its further progression depends upon the supply ofenergyfrom the electric field in the space nearthe tip ofthe leader and upon the dielectric properties of the air undergoing breakdown, neither of these factors being influenced by the air terminal Using this and geometrical arguments, Mackerras et al. (1997) conclude that "it is not possible to gain a significant improvement in lightning interception performance by causing the early emission of a streamer from an air terminal." It is necessary for proponents of ESE devices to assume the arbitrary value of l' =1()6 m S-I for a value of At of about 100 JlS in order to claim a significant length advantage AL of 100 m for the upward-connecting leader from an ESE rod over that from a conventional rod. If the value of v = 105 m S-I, which is consistent with the available experimental data were used instead, even allowing a 100-JlS time advantage and even assuming that the leader could propagate in the lower field in which its initiation is claimed to occur, the length advantage would be only AL = 10 m, which is not likely to be significant in most practical situations. Observations. Two triggered-lightning tests ofa com-

mercial ESE system described by Eybert-Berardet al. (1998) are sometinies cited in support ofthe efficacy ofthe ESE i:echDique.. That particular ESE system had seven! spark gaps at the tip·of the air teimhial that were intended to be activated in a sufficiently high electric field. The first triggered-lightning test, conducted in Florida, showed a current pulse of about 0.8-A peak and 2-ps duration from an ESE rod 85 ps prior to a triggered-lightningreturn stroke to ground at a distance not given by Eybert-Berard et al. (1998). The ESE rod was not struck. No appreciable current followed the initial pul.$e in the. ESE rod. which .suggests that the observed current pulse was not associated with the initiation ofan upward leader. Thus,this. experiment proves nothing relative to ESE system validation. The second triggered-lightning experiment, conducted in France and described in the same AMERICAN METEOROLOGICAL SOOETY

paper, involved lightning that was triggered near an ESE rod with a conventional rod located farther away. The ESE rod was the attachment point of a leaderl return stroke sequence, possiblybecause it was placed closer to the rocket launcher than the conventional rod. Unfortunately, the positions ofthe ESE and conventional rods were not interchanged to see if only the rod (whether ESE or conventional) that is closer to the rocket launcher is always struck or if a more distant ESE rod could compete with a conventional rod placed closer to the launcher. Thus, there is, in fact, no support for the proposed ESE technique in the results of any experimental study involving eithertriggered ornatural lightning. On the contrary, natural-lightning studies have shown that ESE systems do not work as their proponents claim. Moore et al (2000a,b) report no advantage of ESE rods over conventional rods from their studies on a mountain top in New Mexico. In fact, theyfuund that in 7 yr of observations neither ESE rods nor sharp conventional rods were struck, while U conventional rods with blunt tips (diameters ranging from 12.7 to 25.4 rom) were struck. Case studies in Malaysia by Hartono and Robiah (1995, 1999, manuscript submitted to the NFPA, hereafter HR99; Hartono and Robiah 2000) show that there was lightning damage to buildings within the advertised protection zone of the ESE systems. These papers include before and after photographs fur over two dozen cases, providing direct evidence of the failure of such systems. Interestingly, the studies by Hartono and Robiah (1995) on buildings protected using conventional systems show similarlightning damage. Hartono and Robiah (1995, 2000; HR99) conclude that there is no advantage in using an ESE system relative to conventional systems. We do not discuss here the results of laboratory studies ofthe ESE te.chnique since we do DQt believe that laboratory sparks c;m adequatelysimul.ate the natural-lightningattachment process. as discussed in the section '"General information and theory." SUMMARY. The conventional lightning protection technique has proven its effectiveness as evidenced by the compara~ve statistics of lightning damage to protected and unprotected structures. The rolling sphere method commonlyused in the design ofsuch systems is relatively crude, in part, because of our . -insufficient understanding of the lightning attachment process,but it does represent a useful engineerPlg tool fur determining the number and positions of air terminals. Lightning elimination systems cannot prevent the initiation of lightning in the thundercloud and are DECEMBER 2002

2

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Monte San Salvatore. BulL Schweiz. Elektrotechnol., 57t 559-620. - . and - . 1969: New results of lightning observations. Planetary Electrodynamics, S. C. Coroniti and J. Hughe~ Eds., Gordon and Breach. 489-510. - , R. B. Anderson, and H. Kroninger, 1975: Parameters of lightning flashes. Electra, 80t 23-37. Bryan. J. L., R. G. Biermann, and G. A. Erikson, 1999: Reportofthe third-partyindependentevaluation panel on the early streamer emission lightning protection technology. Submitted to the National Fire Protection Association Standards Council on 1 September 1999 in response to a legal agreement of settlement and release between the National Fire Protection Association, HearyBros.. Lightning Protection Company, In~ andLightning Prevention ofAmerica, Inc., 51 pp. Carpenter, R. B.. 1977: 170 system years of guaranteed lightning prevention. Review ofLightning Protection Technology for Tall Structures. J. Hughes, Ed., PubL AD-A075449, Office of Naval Research, 1-23. - , and R LAuer, 1995: Lightning and surge protection ofsubstations.lEEB Trans. Ind. AppL, 31) 162-174Chalmer~ I. D., J. c. Evans. and W. H. Siew, 1999: Emission Lightning Protection. IEEE. Proc. Sci. Meas. TechnoL, l~ 57-63. ACKNOWLEDGMENTS. This research was supported Chalmers, J. A., 1967: Atmospheric Electricity. 2d ed. in part by NSF Grant ATM-0003994. The authors wish to Pergamon Press. 239-262. thank E. P. Krider and an anonymous reviewer for many Chauzy. S., and C. Rennela. 1985: Computed response valuable comments that helped improve the manuscript. ofthe space charge layer created by corona at ground level to external electric field variations beneath a thundercloud.]. Geophys. Res., 90,6051-6057. - , and S. Soula. 1987: General interpretation of surAleksandrov, N. 1.., E. M. Bazelyan. R. B. Carpenter. M. face electric field variation between lightning flashes. M. Drabkin, and Yu. P. Raizer. 2001: The effects of ]. Geophys. Res.. 92, 5676-5684. coronae on leader initiation and development under - . and -.1999: Contribution ofthe ground corona th~dentoIDlconditions andinlong air gaps.]. Phys. . ions to the convective changing mechanism. AtmO$. P~: AppL Ph,s., 3:4,3256-3266~ . Res., 51, 279-300. BClilU,. H., 1972: Radioactive Isotope vemesem nich den - , J. Medale, C. Prieur, and S. Soula.1991: Multilevel BlitzSchutz. Elektrotech. Z.,93t 101-104. . measurement oftbe eIecmc field un4emeath a thunBazelyan, E. M., and P. Ralzer, 2000: LightningPhysdercloud.: 1. A neW system and the associated data ics andLightningProtection. Institute ofPhysics Pubprocessing. ].Geophys. Res.• 96, 22 319-22 326. lishing, 325 pp. Chowdhuri, P., 1996: Electromagnetic Transients in Bent. R B.. and S. K. llewellyn, 1977: An investigation of Power Systems. John Wiley and Sons. 400 pp. the lightning elimination and strike reduction prop- Cohen, I. B., 1990: Benjamin Franklin's Sdence. Harvard erties ofdissipation arrays. Review ofLightningProtecUniversity Press. 273 pp. tion Technologyfor TaIl Structures, J. Hughes, Ed., PubL Covert, R N., 1930: Protection of buildin~ ~d farm AD-A07S 449, Office ofNaval R~ 1-49-241. property from lightning~ u.S. Dept.' or Agriculture Berger, G., 1992: The early emission lightning rod conFarmers Bull. No. 1512, Issued Nov. 1926. revised ductor. Proc. 15th. Int.. Conf. ofLightning and Static Aug. 1930. 31 pp. Electridty, Atlantic City, NJ, U.s. Dept ofTranspor- Durretlt W. R.. 1977: Dissipation arrays at Kennedy tation, 38-1-38-9. Space Center. Review ofLightning Protection TechBerger, K.. and E. Vogelsanger, 1%6: Photographische nologyfor TaIl Structures, J. Hughe~ Ed., PubL ADBlitzun.tet'Suchungen dec Jahre 1955._1965 auf dem 075 449, Office ofNaval Research, 24-52.

unlikely to be able to avert an imminent lightning strike. Further, these systems are indeed struck by lightnin~in which case they act as conventional lightning protection systems. The overall lightning elimination system often includes both structural and surge protection componen~the latter being likelyresponsible for the reported improved lightning performance of the protected object. There is no experimental evidence that an ESE air terminal can protect a larger volume ofspace (ie., can attract a lightning to itselffrom farther away) than can a similarly placed and grounded conventional rod of the same height. An upward-connectingleader speed of 106 m 8-1 is required to produce the "length advantage" of100 m claimed by the proponents ofESE systems in order to demonstrate the superiority of the ESE technique over the conventional method oflightning protection. The typical measured upward positive leader speed is an order of magnitude lower, lOS m S-I, inconsistent with this claim. Given the lack ofevidence ofthe superiority ofESE systems over conventional systems, adequate lightning protection would require that each ofthem have a similar number of air terminals.

': "~;':·REFEREfli'EI·f~,:~~:~~.~ . {<:::}~'~?tltf::~;5~~~{'/z~;,;.,:,~~'/::;"~~~?f~~;c;~,:~

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Eriksson, A. J., 1978: Lightning and Tall Structures. Trans. SouthAfr. lEE. 69, 2-16. - . 1987a: The incidence oflightning strikes to power lines. IEEE Trans. Power Delivery, 2, 859-870. - , 1987b: An improved electrogeometric model for transmission line shielding analysis. IEEE Trans. Power Delivery, 2, 871-886. Ette, A. I. I., and E. U. Utah, 1973: Studies of pointcharge characteristics in the atmosphere. J. Amaos. Terr. Phys., 35,1799-1809. Eybert-Berard. A., A. Lefort, andB. Thirion, 1998: Onsite tests. Proc. 24th Int. Conference onLightningProtection, Birmingham.England. StaffordshireUniversity, 425-435. FAA, 1990: 1989 Lightning protection multipoint discharge systems tests: Orlando, Sarasota, and Tampa, Florida. Federal Aviation Administration. FAATC T16 Power Systems Program, Final Rep. ACN-21O, 48pp. French Standard. 1995: Protection of structures and open areas against lightning using ESE air tenninals. French Standard NF C 17 102. Golde, R. H.. 1973:LightningProtection. Edward Arnold. 220 pp. (reprinted by Chemical Rubber Company, 1975.) - , 1977: The lightning conductor. Lightning Protection, R. H. Golde. Ed., Lightning. Vol. 2, Academic Press, 545-576. Harris. W. S., 1843: On the Nature ofThunderstorms and on the Means ofProtecting Buildings and Shipping against the Destructive Effects ofLightning. John W. Parker. 226 pp. Hartono, Z. A., and I. Robiah, 1995: A method of identifying a lightning strikelocation on a stnlcture. Proc. . Into Conf. on Blectromagnetic Compatibility. Kuala Lumpur, Malaysia, 112-117. - , and - , 2000: A study of non-conventional air terminals and stricken points in ahigh thunderstorm region. Proc. 25th Int. Conf. on Lightning Protection, Rhodes, Greece, University ofPatras, 356-361. Heary, K. P•• A. Z. Cbaberski, S. Gumley, J. R. Gumley. F. Riehens, and J. H. Moran. 1989: An experimental study of ionizing air terminal performance. IEEE Trans. Power Delivery, 4, 1175-1184Hughes. J.. 1977: Introduction. Review ofLightningProtection Technowgyfor TaHStructures, J. Hughes. Ed. Publ. AD-A075 449, Office ofNaval Research, i-iv. me, 1993: Section 1: Guide A: Selection of protec:tion levels for lightning protection systems. Protection of structures against lightning. Part 1: General principles. Intemational Standard IEC 61024-1-1, 57 pp. IEEE P15761D2.01, 2001: Draft standard for lightning protection system using the charge transfer system AMERICAN METEOROLOGICAL SOGETY

for commercial and industrial installations. [Available from IEEE, 3 Park Avenue, New York, NY 10016-5997.) Keller, H. C.• 1939: Results ofmodern lightning protection in the Province of Ontario. Farm Paper of the AIR WGY. Schenectady, NY. Kuwabara, N., T. Tominaga. M. Kanazawa, and S. Kuramoto. 1998: Probabilityoccurrence ofestimated lightning surge current at lightning rod before and after installing dissipation array system (DAS). IEEE Blectromagn. Compat. Int. Symp. Record, Denver, CO. 1072-1077. Lee. R. R, 1978: Protection zone for buildings against lightning strokes using transmission line protection practice.1BEB Trans. IntI App!, 14, 465-470. Lodge, O. J•• 1892: Lightning Conductors and Lightning Guards. Whittaker and Co.• S44 pp. Mackerras, D., M. Darveniza, and A. C. Liew, 1987: Standard and non-standard lightning protection methods.]. Elect. Election Eng. Aust•• 7,133-140. - . - , and -.1997: Review of claimed enhanced lightning protection of buildings by early streamer emission air terminals. lEEEProc. Sci. Meas. Techno!, 144, 1-10. McEacbron, K. B.. 1939: Lightning to the Empire State Building.]. Franklin Inst., 227, 149-217. Moore, C. B., G. D. Aulicb. and W. Rison, 2000a: Mea~ surement oflightning rod response to nearbystrikes. Geophys. Res. Lett., 27, 1487-1490. - , W. Rison, 1. Mathis, and G. Aulich, 2000b: Lightning rod improvement studies.'. AppL Meteor•• 39, 593-{i09. Mousa, A. M.,1998: The applicability oflightning elimination devices to substations and power lines. IEEE Trans. Power Delivery. 13, 1120-1127. Miiller-Hillebrand. D.,1962a: The protection of houses by lightning conductors-A historical review. 1. Franklin Insf., 274, 34-54. - , 1962b: Beeinfussing der Blitzbahn durch radioaktie Strahlen und durch Raumladungen. Blektrotech. Z. Aust•• 83, 152-157. . NFPA, 1997: NFPA 780,46 pp. [Available from NFPA, 470 Atlantic Avenue, Boston, MA 02210.) Peters, O. s., 1915: Protection oflife and property against lightning. Technologic Papers ofthe Bureau of Standards, No. 56, Washington Government Printing Office,27pp. Rakov, V. A., 2001: Transient response of a tall object to lightning. IEEE Trans. Electromagn. Compat., 43, 654-661. - , and A. O. Lutz, 1988: On estimating the attractive radius for lightning striking a structure. Blectrichestvo, 9, 64-67. DECEMBER 2002

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- , and - , 1990: A new technique for estimating equivalent attractive radius for downward lightning flashes. Proc. 20th I ntL Coof. on LightningProtection, Interlaken, Switzerland, Swiss Electrotechnical Assoc., 2.2/1-2.2/5. Rourk~ C., 1994: A review of lightning-related operating events at nuclear power plants. lEEE Trans. Energy Conversion, 9, 636-641. Soula, S., and S. Chauzy, 1991: Multilevel measurement of the electric field underneath a thundercloud: 2. Dynamical evolution ofa ground space charge layer. ]. Geophys. Res., 96, 22327-22336. Spanish Standard, 1996: Protection of structure and of open areas against lightning using early streamer emission air terminals. UNE 21186. Symons, G. J., Ed., 1882: Lightning Rod Conference. E and F. N. Spon, 245 pp. Szpor, S., 1959: Paratonnerres ruraux de type leger. Rev. Gen. de Z'elect., 68, 262-270. Uman. M. A.. 1987: The Lightning Discharge. Academic Press, 377 pp. (Reprinted by Dover, 2001.) van Brunt R. J.• T. L. Nelson, and S. L. Firebaugh, 1995: Early streamer emission air terminals lightning protection systems. National Institute of Standards and Technology, Report 5621 for National Fire Protection Research Foundation, Gaithersburg, MD, Batterymarch Park, QUincy, MA, 190 pp. - , - , and K. L. Stricklett) 2000: Early streamer emission lightning protection systems: An overview. IEEE Electrical Insulation Magazine) 16, 5-24. Yokoyama. S.• K. Miyake. and T. Suzuki, 1990: Winter lightning on Japan Sea coast-Development of measuring systems on progressing feature of lightning discharge. IEEE Trans. Power Delivery, 5, 1418-1425. Zeleny. 1.) 1934: Do lightning rods prevent lightning? Science, 79) 269-271. . ·Zipse) D., 1~4: Lightning protection systems: Advantages and disadvantages. IEEE Trans~ !nd..AppL:. 30, 1351-1361• . - . 2001: Lightning protection. methods: An.update and a discredited system vindicated. IEEE Trans. Ind. AppL) 37) 407-414.

1820 I BAnS-· DECEMBER2002

News Title:

WARNING! of the ICLP Scientific Committee

Date:

14-09-2005

Text:

The Cautionary Message hasn't stopped the sale and promotion of the different types of .Early .Streamer Emission (ESE) systems. Thus the problem of non-conventional air termination still exists. Not only Early Streamer Emission (ESE) systems and Ion Plasma Generators (IPG) systems, claimed drastically to enhance lightning reception, but also Charge Transfer System (CTS) and Dissipation Array System (DAS), claimed to prevent lightning to proteCted structures, are still produced and installed. These systems are installed in conflict with the requirements of IEC's lightning protection standards and as they are not efficient according to the claims, such systems should be abandoned because they will be dangerous to use.

In this situation the invited paper presented by Prof. Aa. E. Pedersen during the iCL,P'2004 is of central importance and therefore presented below. ESE AND OTHER NON-CONVENTIONAL LP SYSTEMS

by AAGE E PEDERSEN Honorary Member of the Scientific Committee of ICLP Home office: Staenget 1 A, OK 2820 Gentofte, Denmark Phone: +45 39 65 17 10 E-mail: [email protected][email protected]

THE TECHNICAL ASPECTS: . Great efforts have been devoted to improve the efficiency of lightning protection and ~any possibilities have been suggested over the years. Radioactive rods have been used for many years but have shown no advantage relative to 'ordinary lightning rods, and the use of radioactive material for this purpose has now been abandoned in most countries.

Laser-triggered lightning involves an electrically powered, sophisticated and sensitive setup that might prevent its practical use as lightning protection except at very special situations. In addition the method has until now shown difficulties with certainty to ensure subsequent flashes. Early Streamer Emission System (ESE), attempts to utilize an emission of early discharges (streamers) on special lightning rods, to provoke and trigger an early lightning flash and thus protect the surrounding over a greater area than in the case of ordinary lightning rods. Even though the name Early Streamer Emission indicates, that it is the early onset of streamers on ESE rods relative to the ones on ordinary lightning rods, that is a measure for the advantage, it appears that the advantage actually is determined by the time difference between the instances of the first appearance of any type of discharges on the two types of lightning rods, an interpretation that will favour the rod with the smallest curvature radius on the tip. Even though the hypothesis seems logical, actual experience in the field has shown that the triggering of a flash is extremely complex and much more complicated than anticipated in the hypothesis. An indication of this complexity is apparent in the experience with rocket-triggered lightning. In spite of great effort to trigger the lightning stroke at a suitable instance, a flash often fails to follow regardless of the extreme influence caused in the electric field by the trailing wire from the rocket, and the resulting generation of very long streamers and leaders. .Another experience with formation of long streamers is found under EHV (Extra High Voltages) and UHV (Ultra High Voltages) switching impulse tests where extremely long streamers are experienced often with termination in the blue sky and sometimes terminating on the ground far away from the test object often without causing SUbsequent flashover. Therefore, the concept of early streamers is not sufficient and inadequate as a parameter for the determination of any advantage of ESE rods versus ordinary lightning rods. Moreover, several investigations (for inst. by Z.A. Hartono and by Charles B. More et al) have shown numbers of missinterceptions, and lightning stokes terminating in the close vicinity of ESE rods, and that competition race between ordinary Franklin rods and ESE rods arranged in parallel setups and exposed to natural lightning did not favour the ESE rods as it should be expected according to the claimed properties. Creditability of the claimed properties for non-conventional LP devices: In' the opera "The Elixir of Love" (L'Elisir d'amore) by Gaetano Donizetti, the quack Dulcamara sells medicine at a high prize against all sorts of sufferings including love problems. To make the story short, the medicine appears to work in a peculiar way, mainly because people believe in it. To avoid that sort of business in real life, laws have been issued against dishonest or

fraudulent advertisements requiring that the manufacturers or vendors must be able to prove the advertised properties. Thus the arguments "I am convinced it works H or HI believe it work" just isn't enough. In most countries laws concerning Product Responsibility and laws concerning Product Reliability have been issued, but the laws are not always followed. An advertisement for a known beauty cream promises the user to get 10 years younger skin. If this was true, a warning should be given not to be used by children less than 10! Because this advertisement is not dangerous, nobody seems to object even though the advertisement violates the laws. . On the other hand, if safety problems are involved there exist tough requirements for the acceptance of products. As an example, this is the case for the acceptance of new drugs where strict requirements have to be fulfilled and numerous tests conducted before such drugs can be marketed. As another example, the knowledge of the actual tensile strength for straps and slings are necessary in order to evaluate the load such straps and slings can be used for with a sufficient high safety margin. I think that everyone will agree that it is indispensable to perform actual tensile strength tests, and that it will not be sufficient indirectly to evaluate the. tensile strength by means of measurements of other parameters, for inst. the elasticity coefficient. Therefore, relevant standards are important for components, apparatuses or systems Where safety is the issue, or where safety is involved, and moreover, that the standards , contain tests' specifications relevant to the circumstances under which the items are going to be used. , Consequently standards, norms and code of practice should comply with at least one of the following requirements: - Founded on recognized and verified physical theory and models. - Founded on recognized and verified empirical models and experiences. - Founded on recognized tradition and practice and experiments from the field collected over sufficient number of years.

,Question 1: Do the non-conventional lightning protection systems, as safety . providing systems, obey the abovementioned requirements for safety? 'Answer 1: No, none direct measurement of the protection offered has been successfully conducted or sufficient empirical data collected from field tests to convince the international technical and scientific community within this field, nor

are the systems founded on any recognized or verified physical theory. Question 2: Does the French ESE standard NF C 17-102 (1995) rest on any of the stated preconditions for safety standards? Answer 2: No, the French ESE standard does not require or specify any direct method to evaluate the efficiency of the protection offered by the non-conventional lightning protection system, leaving the evaluation of the performance alone on the basis of an indirect method, a method that is partly inadequate partly incorrect. The same seems to apply for the other national ESE standards. The French ESE standard and its major deficiencies: - The hypothesis for the function of the ESE rod is insufficient and inadequate, and the hypothesis seems to be limited alone to discharges over smaller distances. - The French standard does neither require nor specify verification tests under natural lightning conditions. - Only laboratory tests for the verification of the function is specified and required. However, laboratory tests are insufficient and inadequate because it is impossible in any laboratory to simulate natural lightning conditions not least due to the limited space and the vast nonlinear characteristics of the lightning processes. - Only negative lightning is considered. - The standard misinterprets the use of the rolling sphere concept. - The standard seems to cover a wide range of lightning rods with auxiliary stimulation of predischarges on the tip of the rods. However, the standard does not distinguish between the different types, for which reason the standard is lacking necessary specifications versus the different form and principles for the individual device. - Tests of the electronic components and auxiliary systems for the ESE rods, including the power supply for the ones which need it, to withstand lightning influences and aging are missing. Similarly are tests for evaluating the effect of the external environment missing, for example the effect of contamination for floating electrode systems. - Requirements and specifications for the recurrent inspections and possibilities for testing of the individual ESE rods, including any necessary auxiliary systems, to verify their original and unchanged properties, are neither required nor specified in the French ESE standard or in its copies in other countries.

To conclude: Even though the hypothesis behind the ESE concept at a first glance might seem rational and likely, it has shown to be partly wrong and in any case insufficient. Moreover, the

., CD N

working group has selected a laboratory test in the standard for the determination of the advantage over ordinary lightning rods, a non-representative test in a non-representative environment, and thus a test that cannot take into account the nonlinearity of the discharge phenomena between laboratory conditions with stroke lengths quoted in meters while lightning discharges are quoted in kilometres. As done by the working group behind the standard, it is fully legitimate to extrapolate the theories and models for discharges over moderate distances to lightning conditions in spite of the vast nonlinearities of the discharge phenomena. However it is indispensable subsequently to demonstrate and verify that the extrapolation with sufficient accuracy does work in practice. Unfortunately this has not been done, and it seems to reveal that the working group has suffered the lack of support by scientists with sufficient knowledge concerning physics of lightning. In addition to the missing requirement in the standard for verification tests under natural lightning condition, the manufacturers have never succeeded in verifying the claimed efficiencies for any of the different I;:SE types (in a way that satisfies the international technical and scientific community within this field) in spite of the repeated promises over more than 15 years. Similarly, it has neither been possible for independent scientists nor organizations to confirm the claimed advantages. On the other hand several investigations have indicated that the ESE devices offer no advantages relative to ordinary lightning rods. To avoid similar problems and unfortunate errors and mistakes in the future, any standard ought to be exposed to international criticisms, especially when the standard concerns safety matters and devices used for safety purposes. THE MORAL ASPECTS:

In spite of the lack of verification of the claimed properties, and in spite of the repeated criticisms from the scientific community, the ESE manufacturers have continued for more than 15 years to sell and promote ESE systems with promises of the non-proven efficiencies compared to ord,inary lightning rods. Instead of providing the repeatedly promised proofs for their claims, they have intimidated persons, organizations, companies and standard-organizations with threats of legal aQtions when they have pointed out, that the claimed advantages are un-proven and when they have warned against the use according to the claims until proven. Some manufacturers and vendors have even got so far as actually suing some of them. . Even the French Engineering Society (SEE) has been threatened with legal action by the ' French manufacturer. THE LEGAL ASPECT:

- In the light of the current laws, what sort of responsibility does the manufacturers of ESE devices carry for their products?

- Is it possible for the manufacturers and the vendors to liberate themselves for any responsibility by referring to the French ESE standard or its copies in other countries, and leave the responsibility to the national standard organizations? - Do the working groups behind the standards (and its single members) carry any legal responsibility? - Who is in the last end responsible for the standard in France (and in other nations for the copies of the French ESE standard)? - What sort of responsibility does scientists and scientific organizations like ICLP carry to enlighten similar problems like the ones in the ESE standards with protection systems that might be dangerous to use?

WHAT TO DO ABOUT THE SITUATION? - How can the relevant authorities in France (and other nations) be approached to inform them about the problem with the ESE devices, and what can we do to help them solve the problems with the ESE standards? - Do we need some sort of Codex for standardization, production, verification and commerce of safety devices like lightning protection devices, or should we merely leave it up to the market?

Last update: 28-06-04

195

INTENSIVE WORKSHOP, LIGHTNING PROTECTION FOR ENGINEERS

Chapter Ten

LIGHTNING SAFETY FOR OUTDOOR ACTIVITIES

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The circumstances for a side flash.

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t Chapter Ten Overview People safety. Here's one short summary sentence. When you hear thunder, go to safety immediately. Thunder is the acoustic companion of the electrical event. Our hearing range is about 5-8 miles (8-12 km) and if you hear thunder that is how close the lightning is to you. See lightning but don't hear thunder? The lightning is more distant than your hearing range. Learn and teach others The 30130 Rule in this Chapter. It is a lightning safety recommendation ofNLSI, the Boy Scouts, the NCAA, the National Weather Service, and many other outdoor organizations. See also IEEE 80, Guide for Safety in AC Substation Grounding as a useful technical document. In this Chapter you will find many safety documents which you can copy and employ for your own needs. Help advocate lightning safety awareness!

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197

DECISION TREE FOR PEOPLE LIGHTNING SAFETY by National Lightning Safety Institute, www.ligbtningsafety.com

1. Is lightning safety appropriate? Ifthere is any likelihood of lightning occurrence, go to #2, below. 2. For individuals and for groups, develop a Lightning Safety Plan. Emphasize Safety ahead of continuation of activities. 3. A general Plan for all circumstances "Ifyou see lightning or hear thunder, go to a safe location immediately." See safe locations defined in 4.3 below. 4. More specific Plans should be tailored to specific locations and situations. Some examples: 4.1 For people outdoors where lightning detection technology is available: Suspend activities and seek shelter when lightning enters a 6 mile radius or when radar indicates 40 dBZ echos within a 6 mile radius; resume activities 30 minutes after the "6 . miles rule" changes. Same applies indoors. 4.2 For people outdoors where there is no lightning detection technology: Apply the 30/30 Rule, ~'At a flash-to-bang count of 30 (6 miles) suspend activities and seek shelter; resume activities only after lightning or thunder has not been observed for 30 minutes." Same applies indoors. 4.3 In all cases, safe shelter is defined as inside a large permanent structure while avoiding contact with inte;rior metal/electrical and other conductors. 4.3.1 Less safe, but "probably safe" locations include fullyenclosed all-metal vehicles with windows closed. 4.3.2 Unsafe outside locations include the high ground, near water, near trees, near metal objects, open ground, near conductors.

National Lightning Safety Institute 891 N. Hoover Ave Louisville CO 80027

198

LIGHTNING AS IT ORIGINATES FROM CLOUDS, NUMBERED IN ORDER OF MOST..TO-LEAST TYPES

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This means no apparent thunderclouds or storms, but lightning emitted from a cloud source beyond visible range. They have been measured striking people from as far as 50 miles (80 kIn) away.

199

FOUR MECHANISMS OF LIGHTNING ATTACHMENT TO PEOPLE

STEP VOLTAGE

DIRECT

TOUCH VOLTAGE SIDE FLASH

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TOUCH AND STEP POTENTIALS

Indirect Side Flash and Shared Ground Step Current Hazards

Shared Indirect Current And Induced Streamer Hazards

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Currents Inversely Proportional to Distance

201

INSTANTANEOUS POTENTIAL DIFFERENCES DURING A LIGHTNING FLASH TO A GROUNDED CONI)UCT()R

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;':otes: t. Person Xis in contact with the ground at a and b; person Yis in contact with the ground at c and the conductor at d; person Z is in contact with the conductor at ('and a metallic hand railfshown grounded atg. 2. Person X is subject to step potential.

6. Step potential increases with the size of the step a-b in the radial direction from the conductor and decreases with the increase in the distance between person Xand the conductor.

4. Person Z is subject to transferred potential.

7. The transferred potential increases with increase in the radial distance between the down conductor and the groundg.

5. The potential depends on the current magnitude and the impedence of the path of the lightning discharge.

Extracts/rom the Australian Standard on Lightning Protection A.S.1768-1983.

3. Person Yis subject to touch potential.

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202

4 4 4

NUMBER OF LIGHTNING DEATHS BY STATE FROM 1995 TO 2004

State

Deaths 1996·2004

Rank of Deaths

State

Deaths 1995·2004

29

7 7 17

24

5

New Jersey New Mexico New York North Carolina North Dakota

Colorado Connecticut Delaware D.C. Florida

31 2 0 0 85

3 40 48 49 1

Ohio Oklahoma Oregon Pennsylvania Puerto Rico

22

Georgia Hawaii Idaho Illinois Indiana

19 0 6 12 12

50 26 11 12

Rhode Island South Carolina South Dakota Tennessee Texas

32 33 34 7 43

Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming

18 0 7 8

Iowa Kansas Kentucky Louisiana Maine

5 5 5 17

1

5

Maryland Massachusetts Michigan Minnesota Mississippi

7 2 11 6 9

22

Missouri Montana Nebraska Nevada New Hampshire

7 6

23 28

3

36

0 0

51 52

41 15 27 18

The lightning fatality data were collected by NOAA (National Oceanic and Atmospheric Administration). They come from monthly and annual summaries compiled by the National Weather Service and published in monthly issues of Storm Data. Data for reoent years are available at: http://www.nws.noaa.gov/omlhazstats.shtml. This table for the period from 1959 to 1994 is included in the following artlole: Curran, E.B., RL. Holle, and R.E. L6pez, 2000: Ughtning casualties and damages in

United States

Rank of Deaths

6

6 47 21 20 31

Alabama Alaska Arizona Arkansas California

4

1

25 8 44 4 16

10 1 12

45

3

37

1 14

46

13

10

9 38 17

34

2

13

10

3

39

12 2 5

42

3

9 6

14

35

19 30

489

One death each occurred in Guam and the U. S. Virgin Islands in 2003.

the United States from 1959 to 1994. Journal of Climate, 13, 3448-3453. The 1959-1994 Information is also available at the National Severe Storms Laboratory web site: http://www.nsst.noaa.gov/papersltechmemos INWS-SR-193/techmemo-sr193.html

Ronald L. Holle Holle Meteorology & Photography Oro Valley, AZ 65737 18 June 2005

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LIGHTNING DEATHS BY STATE, 1995 TO 2004 Source R Hol/e, 2005

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1 2

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8 0,9

N 5 N Roc:kies Rockies plains

United States

West coast

13.7% Under trees Water related, fishing, 8.1 boating, swimming. etc. 3.9 Golfing Golfing and under trees 1.0 Driving tractors, farm 3.0 equipment, heavy road equipment, etc. Open field, ballparks, 26.8 playgrounds, etc:. 2.4 Telephone-related 0.7 Radios, transmitters. antennas, etc:. 40.4 Not reported, at various other and unknown locations

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13.4

9.7

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6.1

12.5

5.5

4.0

1.2 0.6 1.2

4.3

0 7.1

4.6 0.3 2.1

4.2 1.8

9.0

19.0

36.5

40.5

1.8

1.6

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Location of casualty

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13.5

13.6

9.6

5.3

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6.2

3.6

0.4

4.1

2.1 2.6

3.1 1.1 2.0

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20.6

30.4

27.1

20.6

26.2

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1.5 0.3

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27.5

31.7

46.7

35.2

38.6

50.2

39.2

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204

AFTER-EFFECTS TO LIGHTNING SURVIVORS, EXPERIENCED BY 25 PERCENT OR GREATER OF VICTIMS.

* Denotes Psychological Symptoms ** Denotes Physical Symptoms Absense of Symbol Denotes Organic Damage

••

MEMORY DEFICITS/LOSS

52°k

ATTENTION DEFICITS

•

•

DEPRESSION

32 %

41°/0

INABILITY TO SIT LONG

32%

SLEEP DISTUR.BANCE

44%

eXTERNAL BURNS

'32:l,'c

••

NUMBNESS/PARATHESIAS

36°k

••

SEVERE HEADACHES

30%

••

DIZZINESS

38°k

•

AGORAPHOBIA/FEAR tN CROWDS

29 %

EASY FATIGUEA81L1TY

37%,

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STORM PHOBIA

29 Ck

STIFFNESS IN JOINTS

35%

INABILITY TO COPE/OVERWHELMED

2ge~

lRRITA81LlTY/TEMPER LOSS

34°k

••

GENERALIZED WEAKNESS

29°t'o

PHOTOPHOBIA

34°k

••

UNABLE TO WORK

29°k

LOSS OF STRENGTHIWEAKNESS

34%

•

REDUCED LIBtDO

26 %

MUSCLE SPASMS

34°fc,

*.

CONFUSION

25°.10

CHRONIC FATIGUE

32°k

••

COORDINATION PROBLEMS

28°,'0

HEARING LOSS

25°k

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from "Psychological & Neurologic Sequelae to Lightning Strike & Electric Shock Injuries. II

G H EngJestatter. PhD., Carolina Psychological Health Services, Dec.• 1994

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205

POLICY STATEMENT FOR LIGHTNING SAFETY 1.0 Purpose. Lightning Safety is an organizational priority. It is placed ahead of continuity of operations although cessation of activities must be conducted in a safe manner. 2.0 Authority. Lightning safety is a shared responsibility. Management, supervisors and workers all must participate. If you believe you are threatened by lightning immediately take protective precautions. Our safety practice is described below. 3.0 Procedures. The following decision hierarchy, while not perfect, is designed to provide maximum safety for people from lightning's effects: 3.1 Obtain advanced warning ofthe lightning hazard from sources such as: 3.1.1 Hearing thunder and/or seeing lightning 3.1.2 Indications from reliable detectors where available. 3.1.3 TV Weather ChanneL Weather Radio, weather subscription service or other sources ofinformation where available. 3.2 Make decisions to suspend activities and to notify people. 3.2.1 Flash-To-Bang (Lightning to Thunder Ratio) of five seconds = one mile. At a count of thirty = six miles suspend activities. (Note: change this +/- to suit local condition.) 3.2.2 Notify people via radio, siren or other means. 3.3 Move to safe shelter. (Note: No shelter is 100% immune from lightning.) 3.3.1 Large permanent buildings. In or on all-metal vehicles such as cars, vans, trucks, or construction machinery. These are "best" locations. 3.3.2 "Semi-safe" locations are: a dense forest; bushes; low ground; inside any type ofstructure. 3.3.3 UNSAFE PLACES. Stay away from: any metal objects including electrical equipment and machinery; water; trees; hilltops; open spaces; caves; exposed areas. 3.4 Re-assess the hazard. Wait a (recommended) thirty minutes after the last observed thunder or lightning. Lighting may strike from the back side ofa passing thundercloud. Be conservative. 3.5 Inform people to resume activities via radio, siren or other means. 4.0 Effective Date. This Policy is effective immediately. 5.0 Endorsement. This Policy is endorsed by the National Lightning Safety Institute (wwwJightningsafety.com). It is consistent with recommendations from the National Weather Service, the American Meteorological Association, the National Collegiate AtWetic Association and others.

206

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LIGHTNING SAFETY FOR OUTDOOR WORKERS

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t Safety and productivity are not mutually compatible, so one must be chosen over the other. Easy Choice: SafetY First! Lightning has visited most all outdoor work environments. Anticipate a high risk situation and move to a low risk location. Lightning safety awareness is a priority at every one of our facilities. Education is the single most important means to achieving lightning safety. The following steps are suggested: 1. Monitor weather conditions in the early moming houlS. Local weather forecasts - from The Weather Channel, or NOAA Weather Radio - should be noted 24 hours prior to scheduled activities. An inexpensive portable weather radio is recommended for obtaining timely stonn data. 2. Suspension and resumption of work activities should be planned in advance. Understanding of SAFE shelters is essential. SAFE evacuation sites include: a. Fully enclosed metal vehicles with windows up. b. Substantial bUildings. c. The low ground. Seek cover in clumps of bushes. d. Trees of unifonn height, such as a forest. 3. UNSAFE SHELTER AREAS include all outdoor metal objects like power poles, fences and gates, high mast light poles, metal bleachelS, electrical equipment, mowing and road machinery, etc. AVOID solitary trees. AVOID water. AVOID open fields. AVOID the high ground and caves. 4. Lightning's distance from you is easy to calculate: if you hear thunder, it and the associated lightning are within audible range•••about 6..e miles away. The distance from Strike A to StrIke B also can be 6-8 miles. Ask yourself why you should NOT go to shelter immediately. Of course, different distances to shelter will detennlne different times to suspend activities. A good lightning safety motto is:

[(you can see it flightningJ Dee it,· iryou can hear it (thunder), clear it. 5. If you feel your hair standing on end, andlor hear "crackling noises" - you are in lightning's electric field. If caught outside dUring close-In lightning, immediately remove metal objects (including baseball cap), place your feet together, duck your head, and crouch down low In baseball catcher's stance with hands on knees. 6. Walt a minimum of 20-30 minutes from the last observed lightning or thunder before resuming activities. 7. People who have been struck by lightning do not carry an electrical charge and are safe to handle. Apply first aid immediately if you are qualified to do so. Get emergency help promptly. Prepared by the National Lightning Safety Institute, 303-666-8817 (www.lightningsafety.com)

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208

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LIGHTNING SAFETY AT SWIMMING POOLS, EMERGENCY ACTION PLAN FOR THUNDERSTORMS.

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1. General Information. Lightning's behavior is random and unpredictable. Preparedness and quick response are the best defenses towards the lightning hazard. Our pools are connected to a much larger surface area via underground water pipes, gas lines, electric and telephone wiring, fences, etc. A 'lightning strike at one place on this metallic network may induce dangerous shocks elsewhere. Indoor and outdoor pools are to be treated the same for lightning and lightning safety issues. .

2. Lightning Safety Program for SWimming Pools. At the first signs of lightning or thunder, the pools will be evacuated. ("If you can hear it (thunder), Clear It (suspend activities)." They will remain cleared for 30 minutes after thE) last observed lightning or thunder. Patrons should leave the pool and the shower area. Seek shelter inside the main building, or in a fully enclosed metal vehicle with the windows up. AVOID waiting under tall trees, umbrellas, or near electric power lines. AVOID use of showers or other contact with water. AVOID use of the telephone. AVOID contact with metal objects. Prepared by tile National Lightning safety Institute, 3030688-8817.

4

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209

LIGHTNING SAFETY FOR ATHLETIC FIELDS, EMERGENCY ACTION PLAN FOR THUNDERSTORMS. - City of [.•.your name here...] 1. General Information. Lightning's behavior is random and unpredictable. Preparedness and quick response are the best defenses for the lightning hazard.

Il'f you can see it, flee it; if you can hear it, clear it. " 2. Lightning Safety for Athletic Fields. Hear thunder? You may be threatened by lightning. Leave the athletic fields. No permanent bUilding nearby? Your car, truck or van is the next safest place to be when lightning threatens. AVOID the rain and sun shelters and the dugout areas. These places are not safe from lightning. AVOID going underneath trees...they can become lightning rods. AVOID metal fences, metal gates, tall metal light poles and power poles. Wait 30 minutes after the last observed lightning and thunder before you leave safety. (Lightning often comes out of the back end of the T'storm.) Game officials will signal a resumption of activities. Prepared by the National Lightning safety Institute, www.lightningsafety.com

. . .2 2 : _ . m

210

TWO PROPOSED LIGHTNING SAFETY MESSAGES YOU CAN USE

LIGHTNING SAFETY

~

WHERE TO GO & WHAT TO DO.

--------------------- - - LIGHTNING SAFETY MOTTO:

"If you can see it (lightning), flee it; If you can hear it (thunder), clear it!'

AVOID - Trees. Hilltops. Open fields. Fences. Power lines. SEEK·

Electrical equipment. Wet areas. All metal objects. Safety in a vehicle. Safety in a large building.

If lightning is striking nearby, as a last resort you should: 1. Get away from metal objects and trees. 2. Squat down with feet together. 3. Place hands over ears to protect against thunder. 4. Get to safer place as soon as possible.

---------- ---------------------

BE ALERT FOR LIGHTNING. BE READY TO SEEK SAFETY. Prepared in the public interest by NlSI. See us at: www.lIghtnlngsafety.com

THIS IS NOT A LIGHTNING-SAFE STRUCTURE. AVOID THIS LOCATIONDURING THUNDERSTORMS.

211

SAFESHEL STEELS

S USING NTAINERS

High frequency current flowing through a conductor generates an electromagnetic field, one effect of which is to confine the current towards the outside of the conductor. This is known as "skin effect" while the thickness of the layer to which most of the current is restricted is known as "skin depth." The higher the frequency, the smaller the depth of current penetration.

212

OVERVIEW OF LIGHTNING DETECTION EQUIPMENT Lightning hazards can be mitigated by advanced planning. One part of this safety program should include an eariy detection and warning alarm package. Lightning detectors can give notice to shut down dangerous operations before the arrival of lightning. They also may signal "all clear" conditions after the lightning threat has passed. Some tyPe of detection package may help you with Duty-To-Warn issues. Lightning detectors vary in complexity and cost from large dedicated equipment packages costing in excess of $150,000 to inexpensive $20-$30 Radio Shack portable weather radios. The Flash-ta-Bang (F-B) Method requires no dedicated detector: only counting the time in seconds from seeing lightning's flash, to hearing the associated thunder or bang. For each five seconds, lightning is one mile away. Thus, a F-B of 10 2 miles; 15 = 3 miles; 20 = 4 miles; etc.

=

The distances from lightning Strike A to Strike B to Strike C easily can exceed more than 5 miles. How much time is needed to get to shelter? Three to four minutes is suggested. SusPension of activities is very site-specific. For general situations, we recommend activating your lightning defense at a F-B of 30 (lightning is six miles away). We also recommend waiting to resume activities 30 minutes after the last observed lightning or thunder. This protocol may seem excessively conservative in many situations... (''we'li never get anything done under such strict guidelines... "). It is a caseby-case risk management decision. And yes, safety and productivity sometimes are incompatible. Safety, however, always should be the prevailing directive. Available technologies of the present day lightning detectors include: a. Radio Frequency (RFl Detectors. These measure energy discharges from lightning. They can determine the approximate distance and direction of the threat. See www.boltek.com b. Inferometers. These are multi-station devices, much more costly than RF detectors. They measure lightning strike data more precisely. Usually they require a skilled operator. See www.vaisala.com c. Network Systems. The National Lightning Detection Network and the USPLN systems cover all the USA and reports lightning strikes to a central station. - Local storm data is available by subscription. Past strike information is archived and accessible upon request. See www.lightningstorin.com and wwW.uspln.com d. Electric Field Mills. These pre-lightning equipments measure the potential gradient (voltage) changes of the earth's electric field and report changes as thresholds build to lightning breakdown values. For more on EFMs, see www.missioninstruments.com and www.campbellscLcom e. Optical Monitors. These can provide earlier warning as they detect cloud-tocloud lightning that typically precedes cloud-to-ground lightning. f. Hybrid Designs. These monitors use a combination of the other singletechnology designs. -Two or more sources of information (example: e-C, C-G, optical recognition, EFMs) may be better than just one. See www.wxline.com g. Subscription Services. NLSI Recommendation - Rent a Meteorologist. Here hired professionals make the critical decisions and advise you. This method may blunt claims of Negligence if something goes wrong. And some of these companies can provide windspeed, rain, hail, tornados and other data sets. Offsite lightning detection by subscription is available from several vendors, including: Accuweather.com; Meteorlogix.com ("Weather Sentry") and Weatherdata.com ("Sky Guard").

213 Lightning Detection Options - Accuracy vs Cost vs Complexity Source of Info. Hearing Thunder TV Weather Channel Weather Radios Handheld Detectors Boltek System WXLine System Subscription Service

Accuracy Danger is Near General Info. General Info. 50-60ok Accurate 70-80% Accurate 90-95% Accurate 95%+ Accurate

Cost No Cost No Cost Up to $40 Up to $500 Up to $1500 Up to $7000 Monthly Fee

Complexity Simple Simple Simple Somewhat Somewhat Somewhat Simple

Beware of a false sense of confidence from detectors: none of them will detect all of the lightning all of the time. None of them will provide "first strike/Bolt Out of the Blue" information or forecast in advance the positions of lightning strikes on earth. Various detector detection receiver algorythms operate at different frequencies and wavelengths: Boltek Stormtracker in the Low Frequency Range 100-700 KHZ?; Vaisala GAl NLDN at 1Q0-400 KHZ; NMT Lightning Array at VHF 60-78 MHZ; NASA LIS and OTD optical at 777.4 m; Vaisala SAFIR VHF 109-119 MHZ; Vaisala GAl LDAR·II at 50120 MHZ; GAl VLF at 20-50 KHZ; the UK Meteorological Office RDI at 9.8 KHZ; etc. An excellent summary of families of lightning detectors and future research is at: http://thunder.msfc.nasa.gov/validation/instruments.html Detectors can display early warning of lightning conditions to hazardous operations. Some detectors can start/stop standby power generators. A signaling or alarm notification method is essential to alert field personnel of developing dangerous circumstances. Two-way radios, remote-activation siren packages, strobe lights and other methods are available. Essential companions to any type lightning detector include: 1) A written Lightning Safety Policy; 2) Designation of Primary Safety Person; 3) Determination of When to Suspend Activities; 4) Determination of Safe/Not Safe Shelters; 5) Notification to Persons at Risk; 6) Education: at a minimum consider posting information about lightning and your organization's safety program; 7) Determination of When to Resume Activities. For many situations, if you hear thunder, your (brain) detector is working fine. Since ·lightning and thunder always· occur paired, the lightning associated with the thunder you just heard is within your hearing distance - some 7-9 miles. Immediately go to safe shelter. No place outside is safe! Select the detector and/or signaling device that is site-specific to your requirements, easiest to use, and which offers the most favorable costlbenefrt to your operation's budget. No detector is 100% perfect. Summary: Detectors give advanced notice of the lightning hazard. Now consider other defenses to mitigate the hazard. Where is safe refuge? How long to get there? How long to stay there? What about computers and servers and telecommunications? Is facility bonding and grounding and surge protection OK? Lightning rods required? Contact NLSI for assistance.

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INTENSIVE WORKSHOP, LIGHTNING PROTECTION" FOR ENGINEERS Chapter Eleven

REFERENCES, RESOURCES AND CODES

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Chapter Eleven Overview There is much available information about lightning safety: Google has 1,230,000 hits and Yahoo delivers 2,180,000 hits. Whew! New information about lightning behavior necessitates regular revision of Codes and Standards. Note to the lightning protection engineer - those documents typically contain minimum requirements not always sufficient for achieving high levels of protection.

International conferences provide opportunities for introduction of new concepts and debates about long-held assumptions. The International Conference on Lightning Protection (ICLP) is a world class resource. It is conducted every two years. See the high quality of submitted papers at www.iclp2006.net

Thank you for your interest in lightning safety. R. Kitbil, Editor

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GLOSSARY OF LIGHTNING TERMS -NATIONAL LIGHTNING SAFETY INSTITUTE·

ABSORPTION LOSS: The attenuation of an electromagnetic wave as it passes through a shield. This loss is due primarily to induced currents and the associated 12'R loss. ACCESS WELL: A small covered opening in the earth using concrete, day pipe or other wall material to provide access to an earth electrode system connection. ACTION INTEGRAL: Defines the energy in any portion of the current path per ohm resistance. measured in A2s or joules per ohm.

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AIR TERMINAL: The lightning rod or intended attachment conductor placed on or above a building. structure, tower. for the purpose of intercepting lightning. AIR- TERMINATION SYSTEM: Part of the external LPS which is intended to intercept lightning flashes.

AMBIENT FIELD: The electric field strength of the atmosphere at rest, In clear air and under static-free conditions. Generally thought to be some 150·300v/rn at standard temperature and pressure. ARRESTER: Components. devices or circuits used to attenuate, suppress or divert excess electrical (surge and transient) energy to ground. The terms arrester, suppressor and protector are used interchangeably except that the term arrester is used herein for components, devices and circuits at the service disconnecting means. BOND: The electrical connection between two metallic surfaces established to provide a low resistance path between them. See also CORROSION. BOND1NG: The joining of metallic parts to form an electrically conductive path to assure electrical continuity and the capacity to conduct current imposed between the metallic parts. BONDING JUMPER: A conductor to assure electrical conductivity between metal parts required to be electrically connected.

CADWELD®: Process of molecular bonding patented by ERiCa. Also welded connection. CAPACITANCE: The capacity of oppos"e surfaces are maintained stated. . . .

an electric nonconductor that .permits the storage of energy when at a difference of potential.. Measured at 1.0 Hz. unless other wise

CATERNARY SYSTEM: Suspended overhead wires as a part of the LPS: Sometimes called shield wires. CIRCUIT: An electronic closed-loop path between two or more points used for signal transfer. CIRCULAR MIL: A unit of area equal to the area of a circle whose diameter is one mil (1 mil = 0.001 inch). CLAMPING VOLTAGE: The voltage that appears across surge suppressor tenninals when the suppressor is conducting transient current.

CLOUD-TO-CLOUD (Ce) LIGHTNING: A lightning stroke between thunderclouds. Typically, CC lightning precedes CG lightning.

218 (

• COLUMB: Current Umes Time. A measurement of charge in amp-seconds.

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4 CONDUCTOR SHJELDING: An envelope that encloses the conductor of a cable and provides an

equipotentional surface in contact with the cable insulation. CONE OF PROTECTION: A conic space around a vertical lightning rod used to define a region of protection. The cone whose height equals the height of the rod and whose base radius is equal to the

rod height. Regarded as an obsolete term. See ZONE OF PROTECTION. COPPER CLAD STEEL: Steel with a coating of copper bonded on it. CORONA DISCHARGE: A localized cold discharge in air which forms around grounded objects producing an enhancement in electric field strength to allow ionization growth. Calted St. Elmos's Fire by ancient mariners. Precedes an arc or spark.

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DOWN-CONDUCTOR SYSTEM: Part of the external LPS which is intended to conduct the lightning current from the air-termination system to the earth-tennination system.

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DOWNWARD FLASH: Lightning flash initiated by a downward leader from cloud to earth. A downward flash consists of a first short stroke, which can be followed by SUbsequent short strokes and may .. include· a long stroke. . '

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COULOMB. A unit of energy. One coulomb

=one amp second.

COUPLING: Energy transfer between circuits, equipments, or systems. CORROSION: The degradation of metals overtime, usually due to OXidation. CROWBAR: Crowbar is a method of shorting a surge current to ground in surge protection devices. This method provides protection against more massive surges than other types, but lowers the clamping voltage below the operational voltage of the electronic equipment causing noise and operational problems. It also permits a follow current which can cause damage.

COUNTERPOISE: See RING ELECTRODE. DATA LtNE: A cable canying information as distinct from power. Examples of data lines are telephone

EARTH: That portion of the earth's crust sufficiently below' the surface to act as an infinite sink or source.for electric charge. Earth Is considered the universal ground or.reference zero potential level.· , EARTH ELECTRODE SYSTEM (GROUNDING ELECTRODE SYSTEM): A network of electrically interconnected rods. plates, mats, piping, incidental electrodes (metallic tanks. etc.) or grids installed below grade to establish a low resistance contact with earth. EARTH-TERMINATION SYSTEM: Part of an external LPS which is intended to conduct and disperse the lightning current to the earth. ELECTROMAGNETIC C'ONI'PATIBILIlY (EMC): The capability of equipments or systems to be operated in' their intended environment, within designated levels of efficiency. without causing or receiving degradation due to unintentional· etectromagnetic interference. EMC Is the result of an engineering planning process applied during the life cycle of the equipment. The process involves careful considerations of frequency allocation, design, procurement, production, site selection, installation, operation. and maintenance.

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ELECTROMAGNETIC INTERFERENCE (EMI): Any electrical or electromagnetic phenomenon, manmade or natural, either radiated or conducted. that results in unintentional and undesirable responses from, or perfonnance degradation or malfunction of electronic equipment. ELECTRON AVALANCHE: An electron multiplication process due to electron-impact ionization of gas molecules. This is the initial stage in the development of an electrical discharge in air, e.g. a corona or streamer. ELECTRONIC MULTIPOINT GROUND SYSTEM: An electrically continuous network consisting of interconnected ground plates, equipment racks, cabinets, conduit, junction boxes, raceways, duct work, pipes and other normally non-current-carrying metal elements for electronic signals. It includes conductors, jumpers and straps that connect individual electronic equipment components to the electronic multipoint ground system. ELECTRONIC SINGLE POINT GROUND SYSTEM: A single point ground system provides a single point reference in the facility for electronic signals. The single point ground system shall be installed in a trunk and branch arrangement to prevent conductive loops in the system. It shall be isolated from all other ground systems except for an interconnection. where applicable, to the mUltipoint ground system at the main ground plate. The single point ground system consists of Insulated conductors, copper ground plates mounted on insulated stands, and insulated ground plates, buses, and/or signal ground terminals In the electronic equipment which are isolated from the frame of the equipment. See IEEE 1100 and FAA 019d. EQUIPMENT GROUND: A connection between a unit of electlical equipment and the facility ground network. EQUIPMENT GROUNDING CONDUCTOR: The conductor used to connect non-current-carrying metal parts of equipment, raceways, or other enclosures to the system grounded conductor and/or grounding electrode conductor at the service entrance or at the source of a separately derived system. EQUIPOTENTIAL SIGNAL REFERENCE PLANE: An equipotential conducting plane designed to maintain a number of electrical/electronic units having a common signal reference at the same potential. EXTERNAL LIGHTNING PROTECTION SYSTEM: It consists of an alr-tennlnatlon system, a down conduction system and an earth termination system. FACILITY: A building or other structure, either fixed or transportable in nature, with its utilities, ground· networks, and electrical supporting structures. All wlring,cabling ·as well as· electrical· and electronic eq\ilpments are also part of the facility. FACILITY GROUND NETWORK: The electrically conductive network, .Including·' all structures and grounding cables bonded to the earth grounding counterpoise but excluding the instrumentation ground network and electrical enclosures, conduit, and raceway systems. In steel frame structures, the structural members may be bonded together and connected to the earth grounding counterpoise to fonn the basic network. In buildings using nonconductive structural methods and materials such as masonry and In outside facility areas such as gas, propellant, or oxidizer service facililies, the facility ground network consists of condUctors, sized according to criteria inclUded in this standard, bonded to an earth grounding counterpoise and extending to all areas containing equipment to be grounded. .

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FACILITY GROUND SYSTEM: The electrically interconnected system of conductors and conductive elements that provides multiple current paths to earth. The facility ground system includes the earth electrode SUbsystem, lightning protection SUbsystem. signal reference subsystem, fault protection SUbsystem, electronic mUltipoint ground system, electronic single point ground system, as well as the building structure. equipment racks, cabinets, conduit, junction boxes, raceways, duct work, pipes, and other normally noncurrent-carrying metal elements.

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FARADAY CAGE OR SHIELD: An electrostatic (E field) shield made up of a conductive or partially conductive material or grid. Faraday cage or screen room is effective for protecting inside equipment from outside radiated RF energies. Lightning flows around the exterior. not inside, the structure.

FIRST RETURN STROKE: That current flow along the previously ionized path occurring when that path is complete from cloud to ground. FLASH: The total lightning discharge. FLASHOVER: Arcing or sparking between two or more (isolated) conductors. See thermal sparking. FOUNDATION EARTH ELECTRODE: Reinforcement steel of foundation or additional conductor embedded in the concrete foundation of a structure and used as an earth electrode. Also called "UFERll ground. GROUND: tf not otherwise qualified. ground means any electricat connection to earth. either directly through a facility ground network or through some intennediary grounding system such as an instrumentation ground network. GROUND FLASH DENSITY (Ng): The average annual ground flash density is the number of lightning ftashes per square kitometer per year. Replaces tess accurate ISOCERAUNIC DAYS. GROUND IMPEDANCE: The ground resistance and the inductance/capacitance value of the grounding system. Also called dynamic surge ground impedance. GROUND LOOP: An undesired potential EMI condition formed when two or more pieces of equipment are interconnected and earthed for shock safety hazard prevention purposes. GROUND RESISTANCE: The resistance value of a given ground rod or grounding system as measured, usually by a fall of potential (3 stake) method. using a 100Hz signal source. GROUNDED, EFFECTIVELY: Pennanently connected to earth through a ground connection of sufficiently low impedance and having sufficient current carrying capacity that ground fautt current which may occur cannot cause a voltage build up dangerous to personnel. GROUNDING: ,Grounding is the act ,of effecting optimum, electrical continuity between conducting objects and earth. '

HIGH FREQUENCY: All electrical signals

at frequencies greater than 100 kiiohertz (kHz). Pulse and'

digitalsigrials with ,rise and fall times of less than 10 microseconds are classified as high frequency signals. IMPEDANCE: The overall resistance to an electrical current. consisting of both inductance and resistance. IMPROVED GROUNDING: Inadequate, not-connected, or toose grounding is a major cause of power quality problems as well a$ personnel safety issues. Well-known techniques, verified by many Codes 'and Standards, offer remediation and upgrade' 'apPrQaches. Minimum standards are in NEe (NFPA70), section 250. INDUCTANCE: 1. Property of aconduetor which 'makes it resist and oppose any current change through it. 2. A process where one charged object can transfer similar properties to a nearby object without direct contact.

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INTERNAL LIGHTNING PROTECTION SYSTEM: All measures additional to those mentioned under extemal lightning protection system including the equipotential bonding. the compliance of the safety distance and the reduction of the electromagnetic effects of lightning current Within the structure to be protected, including. shielding and surge protection devices. ISOKERAUNIC (OR ISOCERAUNIC): Value (number) of thunderstonns measured daily expressed as Td/yr. Examples: Cerromatoso, Colombia with 325 Td/yr.; Florida with 110 Td/yr; Alaska with 3 Td/yr.. JOULES: A unit of energy. One joule

=one watt second.

LANOLINE: Any conductor, line or cable installed externally above or below grade to interconnect electronic equipment in different facility structures or to connect externally. mounted electronic equipment. LEADER: A preliminary breakdown that fonns an ionized path. See STREAMER. LIGHTNING ELECTROMAGNETIC PULSE (LEMP): Voltages or currents induced into cables and other conductors by the radiated field from a lightning flash some distance away. LIGHTNING FLASH TO EARTH: Electric discharge of atmospheric origin between cloud and earth consisting of one or more strokes. LIGHTNING GROUND: A connection between a lightning protection system and a facility ground network or counterpoise. LIGHTNING PROTECTION SUBSYSTEM: A complete subsystem of LIGHTNING PROTECTION SYSTEM (LPS): The complete system used to protect a structure and its contents against the effects of lightning. Commonly it consists of both external and internal lightning protection systems. Includes air tenninals, interconnecting conductors. ground terminals, surge protection for data and power lines, shielding and bonding. and other equipment and techniques to assure that the lightning discharge will be directed safely to earth. LIGHTNING STROKE: Single discharge in a lightning flash to earth. LOW FREQUENCY: Indudes all voltages and currents, whether signals. contrOl, or power, from DC through 100 kHz. Pulse and digital signals with rise times of 10 s or greater are considered low frequency signals.

MAGNETIC FIELD: A vector field produced by a continuous flow of charge. MULTIPLE STROKES: Lightning flash ·consisting In .average of 3--4 strokes. with typical time interval between them of about 50 ms. MUTUAL INDUCTANCE: The property of a circuit Whereby a voltage is induced in a loop by a changing current in a separate conductor. NATIONAL ELECTRICAL CODE (NEe): A standard governing the use of electrical wire. cable. and fixtures installed in buildings. The National Fire Protection Association (NFPA-70) .sponsors it under. the auspices of the American National Standards InStitute (ANsi-CI). . . . NEUTRAL: The ac power system conductor which is intentionally grounded on the supply side of the first service disconnect (ing) means. It is the low potential (white) side of a single-phase ac circuit or the low potential fourth wire of a three-phase wye distribution system. The neutral (grounded conductor) provides a current return path for ac power currents whereas the grounding (or green) conductor does not, except during fault conditions.

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ONSET FIELD: The electric field strength above which ionization occurs. generally thought to be 2.6kV/m in dry air at standard temperature and pressure. OVERSHOOT VOLTAGE: The fast rising voltage that appears across surge suppressor tenninals before the suppressor turns on (conducts current) and clamps the input voltage to a specified level. PENETRATION: The passage through a structure by a cable. wire. or other conductive object. POWER: Power is (voltage x current) or a (COUlomb/second). POWER GROUND: A designed connection between a power circuit conductor and a grounding counterpoise. POWER LINE: A cable canying AC or DC power. PRESSURE CONNECTOR: A high-pressure method which uses hydraulic crimpers to create connectivity. PRIMARY CLOUD· TO-GROUND (CG) LIGHTNING STROKE: The initial discharge between the thundercloud and ground which generally is associated with a stepped leader propagation. Sometimes referred to as the initial stroke or simply the lightning flash. RADIO FREQUENCY INTERFERENCE (RFl): RFI is manmade or natural. Intentional or unintentional electromagnetic propagation which results in unintentional and undesirable responses from or performance degradation or malfunction of. electronic equipment. RESISTANCE: The property of a conductor to oppose the flow of an electric current and change electric energy into heat. For lightning safety purposes, low resistances are desired. They are expressed in ohms. REVERSE STANDOFF VOLTAGE: The maximum voltage that can be applied across surge suppressor terminals with the surge suppressor remaining in a non-conducting state. RF: Radio frequencies - any and all frequencies that can be radiated .as an· electroffi.agnetic wave (plane wave). . . . .

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RING EARTH ELECTRODE: An earth electrode forming a closed loop around the structure below or on the surface ofthe earth·. Also called COUNTERPOISE. . SAFETY DISTANCE: Minimum distance between two conductive parts within the structure to be protected between which no dangerous sparking can occur. See "flashover".

SAFETY GROUND: The local earth ground. The earth ground which grounds the neutral return. The wire may be green or bare and can be through a metal conduit. It may be earth grounded as many times as needed. (Neutral must only be grounded once at the entry location). .SELF..INDUCTANCE: ·The property Of a Wire ·or circuit which causes a back e.mJ. to be generated when a changing current flows through it. SEPARATELY DERIVED SYSTEM: A premises wiring system whose power is derived from a battery. a solar photovoltaic system or from a generator. transfonner, or converter windings. and that has no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system. .

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SHIELD: A housing, screen. or cover which substantially reduces the coupling of electric and magnetic fields into or out of circuits or prevents accidental contact of objects or persons with parts or components operating at hazardous vottage levels. Also Faraday Cage. SHIELDING: The process of applying a conducting barrier between a potentially disturbing noise source and electronic circuitry. Shielding may be accomplished by the use of metal barriers. enclosures, or wrappings around source circuits and receiving circuits. SIGNAL GROUND: A connection between a signal circuit and its zero signal reference plane. SIDEFLASH: Ughtning arcing from one conductor to another across a dielectric.

SKIN EFFECT: The gradient conduction and propagation of RF or RF components of a surge on the outer surfaces of conductors. STATIC GROUND: A functional tenn describing a connection between conductive objects and a facility ground network or counterpoise for the purpose of dissipating static electncity. STRIKE TERMINATION DEVICE: A broad classification of devices intended to intecept lightning. STREAMER: See LEADER. An ionized channel launched from ground-based objects. LEADERS come from the cloud. STREAMERS come from the ground STRIKING DISTANCE: The distance covered by the final leader step of a downward propagating primar)' lightning stroke in making contact with a grounded object. This distance vanes with the type and intensity of the lightning stroke. STROKE: A component discharge of a lightning flash, which follows a leader. SUBSEQUENT RETURN STROKES-RESTRIKES: Those strokes occuning after the first return stroke in a mutti-stroke flash. SURGE: A type of electrical overstress. In the absence of protedive devices, the magnitUde of the peak voltage of a surge is usually understood as at least twice the normal system voltage, and the duration of the overvoltage is less than a few milliseconds. (The word ·surge" is also used by some engineers and technicians to indicate what should properly be caned a swell.) SURGE PROTECTION DEVICE (SPD): A d.evice designed to protect electrical apparatus from high transient voltage and to timit the duration and the amplitude' of follow-cunent. Device that is· intended' to limit transient overvoltages and divert or absorb surge currents. Replaces TVSS tenninology .

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SURGE REFERENCE EQUAUZER: A surge protective device used for connecting .equipment to external systems whereby aU conductors connected to the protected load are routed, physically and electrically. through a single enclosure with a shared reference point between the input and output ports of each system. SURGE SUPPRESSOR: Component (s). device (s) or circuit (s) designed to attenuate. suppress or divert conducted transient(s) and surge energy to ground to protect electronic equipment. SURGES AND SURGE SUPPRESSION: Surges are direct and induced excess energies in a surging wavefonn. The toad is SUbject to .damage by voltages. which exceed specifications. Surge protectors canctip off or dispe~ excess energy using a variety of techniques. . . THERMAL SPARKING: Occurs when a very high current is forced to cross a joint between two conducting materials which have an impertecl bonding or mating between their surfaces.

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THUNDERCLOUD: A cloud containing a charge density sufficient to allow formation of a lightning stroke. THUNDERSTORM DAY: A local calendar day on which thunder is heard. THUNDERSTORM DAYS (Td): The number of thunderstorm days per year obtained from ISOCERAUNIC maps. TOTAL SURGE ENERGY: Total sum of surge energy for all lines of a protector unit. Measured in joules. The minimum total energy which results in the failure of the unit. TRANSFER IMPEDANCE: Referring to coax, is the impedance to transfer into or outside the coax at various frequencies usually below 1MHz. Due to loss of skin effect. attenuation or shielding at these low frequencies, coax can be susceptible to interference and noise as well as the radiation of such signals. TRANSFER INDUCTANCE: The property of a circuit whereby a voltage is induced in a loop by a changing current in another circuit, some part of which is included in the loop. TRANSIENT: 1. A brief event, usually lasting less than a few milliseconds. In many situations transmission line theory, rather than circuit analysis, must be used to describe the propagation of a transient voltage or current. 2. In mathematical analysis the transient is the part of the system's behavior before the steady state Is reached. 3. The work "transient" is often used to indicate a "transient overvoltage-. 4. TRANSIENT Voltage Surge Suppressor (TVSS) is being replaced with the more definitive tenn SURGE PROTECTION DEVICE (SPD). TURNON VOLTAGE: The voltage required across a transient suppressor terminal to cause the suppressor to conduct current. UFER GROUND. Grounding electrodes encased in concrete. To mitigate concrete cracking, explosions and/or spalling under lightning threat, UFER grounds should also adopt additional buried electrodes, such as a ring electrode. UPWARD FLASH: Lightning flash initiated by an upward leader from an earthed structure to a cloud. An upward flash consists of a first long stroke with or without multiple superimposed short strokes, which can be followed by subsequent short strokes possibly induding further long strokes.

UNINTERRUPTIBLE POWER 'SUPPLY (UPS): An apparatus that supplies continuous power to a load, despite. disturbances and outages in the .mains. A UPS contains a bank of rechargeable batteries

that suppty power in the abse~ce of acceptable supply.voltage. . WAVE IMPEDANCE: The ratio of the electric field strength to the magnetic field strength at the point of observation. ZONE OF PROTECTION: The presumed volume of space adjacent to a lightning protection system that is substantially immune to lightning strikes. (fhis is stili subject to debate. The random nature of lightning and its behavior is such that Zone of Protection remains a general and theoretical model. . Protectio~ from its effects therefor~, i~ an Absolute Sense, .is impl?5Sib.I~.~

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ANNUAL USA LIGHTNING COSTS AND LOSSES, ComplIed by the NatIonal UghtnJng Saf&ty InstItUte (wwwJlghtnlngsafety.com)

Accurate information about Ughtnlng-caused damage is elusive, however intensive remlrch suggests realistic lightning costs and losses may reach S4-5 biIJwn per year. Available and verifiable reporting includes:

1.

FIRES. 1.1 Forest Fires. 1.1.1 Half the wildfires in the western USA are llghtning-caused. In total there are about 10,000 such fires costing BLM about 5100 million annually. -Dale VllnCe, BLM, US Dept. Interior 1.2 Fires To structures. 1. L2 From 1994-1999 aDDual average Ilgbtning-caused fires to structureJ and vehicles totaled 18,890 incidents at a cost of 5209,000,000. - NFPA Research Report 5/112005. 1.2.2 18-/_ of all lumberyard ftret and JO·At of aU church fires are lightning-related. -01do IMlU'tlllCe InstitIde, Columbus OB

2. INSURANCE INDUSTRY REPORTS. 2.1 During the 5 year period 1992..1996, we paid out 51.7 billion In lightning-related claims. This was 8.7°/. of total claims and J.B·At of dollar losses. - St. Ptlllllll& Co. 2.2 Each year we have about 307,000 claims from lightning, amounting to 1051 relmbunements of some 5332 miIIwn.- Stttte FtII7tIIIISIU'tIIICe Co. 2.3 Five percent of aU Insurance deims are lightning-related, amounting to over $1 billion per year. 11U",1IIICe InfontUltion Institute, NY, PNu Rele4fe 19'9. 2.4 On 8nnual average, we payout about 3-4./. of our claims as a result of lightning. FtICtDry Mutuill

Cmnpa1rJa. 3.STORAGE AND PROCESSING ACTIVITIES. 3.1 ~ specifically at .torage and prousling actiVities lightning accounts for 61-/_ of the acddents initiated by natural events•••in North American 16 out of20 accidents involving petroleum produm storage tanks were due to lightntng strikes. -J0IU'IUIl of HIIZIIt'tkHIs MtIINiaLt 40 (199S) 43·$4 3.2 The most expensive civilian lightning loss on record in the USA wu a Denver warehouse hit on July 23, 1997. Damage to building and contents exceeded 550 million. - NISI, 1998 3.3 A lightning-eaused explosion at tbe Naval Air Rocket Test Station (Lake Denmark NJ, 1926) cost 570 million with 13 people killed. - Po VJemeister, "TIle Lightning Book" 4. AIRCRAFT MISHAPS & UPSETS. 4.1 More than SO-/_ of military aircraft weather-related in-flight mishap' are caused by UghtDiDg. • Major P.B. Qlm, Air Force Flight Dyntunics Lob. 4.2 During 1988-1996, the US Air Force had direct repair costs of $1,577,%0 due to lightning damage to aircraft. - US Air Force SII/ety Center, AlbIUJl'el''lue NM. 4.3 LIghtning costs about $2 bOOon aDBually ill airline operating costs and passenger delays. -NOAA Report No. 16, MIT, 13 Feb. 1996.

5. ELECTRICAL INFRASTRUCTURE. 5.1 Some thirty percent of all power outages are'lightning-related on annualaver&ge, With total eost8 approaehing one bil6ondoDan. -Ralph Bernstein, EPRJ : Diels, et al (1997j. . 5.2 Our City of Virginia Beach VA has 321 fully automatic tramc signals. From May. 1999 to )by . 2000 we experienced 359 lightning CaUsed· maifundfoDJ at '. direct equipment eost of 536,425. Adding up aU USA cities, the total costs must be very high. -6. Von Eiken, Traffic SupenU01, City of VJ1'gini4 Betu:h VA 5.3 Utility company nuclear power plant digital and I&C equipment safety feature activations were initiated by lightning In 19-/0 of the cases... US NIIde.,. Regll/Btoty CoItUlliDion, NUREGlCR-6579. 5.4 Our database shows 145 lightning events to privately-owned nuclear power plants in the period 1985--2000. - U.S. Nuclear Regulatory Commilsion, ReportMorch 2001.

6. ELECTRONIC COMPO.NENT& 6.1 Lightning 8c~ted tor 101,000 laptop .ad de.ktop computer losses amounting to 5125,417,000 in damage in 1m. -Co11IpIIIet' Security News (www.secure-it.co~Iettm.Sttltistics96.1Itm)

7. DEPARTMENT OF ENERGY. 7.1 From 1990 to 2000 our records show 346 lightning Incidents to USA 81 nuclear sites. - DOE

OccIIrtmee Reporting mul Processing System Dtlt4btzse.

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HELPFUL LIGHTNING URLS by NiItiolUll Lightning Safety Institute

Dept Defense Standards Library - Joint Spectrum Center www.jsc.mil go to '1>ocmnents - EMC Standards Library" for Handbooks. Instructions and Militmy Standards. Look esp. for: MIL 419A; MIL 188; MIL 5087B; MIL 1542; MILI757A Atmospheric Electricity Newsletter - Global News X 2/Yr. www.ae.atmos.uah.edu New Mexico Tech Lightning Research www.ee.nmtedul.....l angmuir IEEE Power Engineering Society - Lightning

www.ieee.orglpes-ligbtning USA Weather Site with detailed USA Lightning Strike Data www.weathennatrix.comlligJrtning Off Site (Remote) Weather Subscription Services

www.Lightningstorm.com www.Accuweather.com wwwJntellicastcom Air Force Lightning Protection API 32-1065 and other Pubs 32-1065 andAFMAN 91-201 bttp://afpubs.hg.afmil

NCAA Lightning Safety Recommendation for Recreation www.ncaaorgllibrarylmNrts science/§POrts moo handbook/2002-Q3/1d.pdf

National" Severe Stor.tit Lab. Ligb1Ding" www.nSsl.noaagov goto"Jigh1niug"

~e Lightnitig Detector with softWare www.boltekcom

NASA on Lightning Detection http://tbunder.msfc.nasa.gov High speed lightning flash sequence photos http://wsx.lanl.goylligbtni n g .bolt.html "

227

P.2URLs

35 mm camera lightning trigger www.ligh1ningtrigger.com

EMC Tutorial inclligbtning www.compliance-<:lnb.comlarchivell001018.htm Navy Lightning Code NAVSEA OPS and other Pubs www.navy.mil/noJJcathtml USA Five Year Lightning Map www.crh.noaagov!pnblltglnsa

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Lightning Maps of Selected Countries See www.lightningsafety.com section 6.17

Walt Lyons Sprites & Jets Upper Atmosphere Info www.:fma-research.com also from Alaska: http://elf.gi.alaskaedn Ligbtning Protection Tutorial (vendor) www.polyphaser.com Surge Protection Devices Tutorial (vendor) www.telematic.com Lightning Photos www.weatherimages.com Federal Aviation Admin FAA 6950.19A http://anslfaa-gov!ans600!orders-specificationsl695019 1of4 .pdf also see•..2of4.pdf and 30f4.pdfand 4of4.pdf

Web BnUetin Board.on Global Lfgldning Protection Issues www.groups.yahoo.comlgrouplLightingProtection

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REVIEW OF COUNTRY LIGHTNING CODES AND THE INTERNATIONAL me 62305

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4 1.0 Background and Present-Day Situation. 1. 1 More than 100 published lightning protection (LP) Codes and Standards are in use by various countries and by agencies within countries. The USA NFP A-78Q-Z004 has undergone significant upgrading with new infonnation about surge protection. The US Department of Energy recently released M440.1-1, Electrical Storms and Lightning Protection for application to explosives facilities. The US Air Force modified AFI 321065 to provide better guidance for critical operations. Yet many USA codes and standards represent only generalized and minimum levels of safety application: NFPA780 and UL 96a by example are not required and have no force of law behind them. On the other hand, some USA documents provide exacting information for specific problems confronting the LP engineer: IEEE 1100, IEEE 142 and FAA SID 019d/e are examples. Motorola R56 contains specific guidance for radio engineers. 1.2 Looking outside of the USA t s -isolated boxes of information, a review of other nations' LP documents is educational and interesting. There is considerable helpful guidance in (by example) Singapore's CP 33, AustralialNew Zealand's AS/ANZ-1786 (2003), South Africa's SABS-03, the German VDE 0185 and the British BS-6651. There is agreement and harmony among most national codes as the readers of the Chinese GB 50057, the Russian RD 34.21.122-87, the Indian IS 2309, and the Polish PN;.86!E05003/01 will discover. Only with "renegade" ESE standards promoted by powerful commercial lobbying groups such as the French NF C 17-102 and the Spanish UNE21186 are government endorsements extant for unapproved, non-scientific LP systems. 2.0 The Future. 2.1 Change is coming. The European TC ·81 Technical Committee of the International Eleetrotechnical Commission (!BC, see www.iec.ch) is finalizing the fivepart authoritative and comprehensive LP standard IEC 62305. 2.2 mc 62035 will address in d~~i1 th.e below. subject matters: . ' . 2.2.1 Part 1 Prot"OOtiop of StrucroresAgainst Lightning: General Principles. .2.2~2 Part 2 Risk Managet:nent. . 2.2.3 Part 3 Physical Damage and Life Hazard. 2.2A Part 4 Electrical arid Electronic Systems within Structures. 2.2.5 Part 5 Services (telecom, powerlines, etc.) 2.3 All LP Codes and Standards are living documents subject to change. As new and veDfiable information about lightning defenses becomes understood, guidance documents will provide additional assistance and direction for safety.

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81/262/FDIS FINAL DRAFT INTERNATIONAL STANDARD PROJET FINAL DE NORME INTERNATIONAlE Project number IEC 62305·1 Ed. 1.0 Numero de projet IECITC or SC CEI/CE ou

Submitted for parallel voting In CENELEC Soumis au vote parallele au CENELEC

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Secretariat I Secretariat

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Italy

Distributed on I Diffuse Ie

Voting terminates on I Vote clos Ie

2005-08-19

2005-10-21

Also of Interest to the following committees Interesse egalement les comites suivants

Supersedes document Remplace Ie document

37A, 64, 77

81/216/GDV - 81/237A1RVG

Functions concerned Fonclions concernees

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Safety Securite

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EMC CEM

INTERNATIONAL ELECTROTECHNICAL COMMISSION

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Environment Environnement

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Quality assurance Assurance de la qualite

COMMISSION ELECTROTECHNIQUE INTERNATIONALE

THIS DOCUMENT IS A DRAFT DISTRIBUTED FOR APPROVAL. IT MAY NOT BE REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH. IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, FINAL DRAFT INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.

CE DOCUMENT EST UN PROJET DIFFUSE POUR APPROBATION. IL HE PEUT ETRE CITE COMME NORME INTERNATIONALE AVANT SA PUBLICATION EN TANT aUE TElLE. OUTRE lE FAIT D'ORE EXAMINES POUR ETABLIR S'llS SONT ACCEPTABlES A DES FINS INDUSTRIEllES, TECHNOlOGlaUES ET COMMERCIALES, AINSI aUE DU POINT DE VUE DES UTiLISATEURS, LES PROJETS FINAUX DE NORMES INTERNATIONALES DOIVENT PARFOIS ETRE EXAMINES EN VUE DE LEUR POSSIBILITE DE DEVENIR DES NORMES POUVANT SERVIR DE REFERENCE DANS lES REGlEMENTATIONS NATIONAlES.

Title

lEG 62305-1 Ed. 1.0: Protection against lightning - Part 1: General principles

Titre

GEl 62305·1 Ed. 1.0: Protection contre la foudre - Partie 1: Principes generaux

ATTENTION VOTE PARALLELE CEI - CENELEC L'attentian des Comites nationaux de la CEI, membres du CENELEC, est attiree sur Ie fait que ce projet final de Norme internationale est soumis au vote parallele, Un bulletin de vote separe pour Ie vote CENELEC leur sera envoye par Ie Secretariat Central du CENELEC.

ATTENTION IEC - CENELEC PARALLEL VOTING The attention of IEC National Committees. members of CENELEC, is drawn to the fact that this final Draft International Standard (DIS) is submitted for parallel voting. A separate form for CENELEC voting will be sent to them by the CENELEC Central Secretariat.

Copyright© 2005 International Electrotechnical Commission, IEC. All rights reserved. It is permitted to download this electronic file, to make a, copy and to print out the content for the sale purpose of preparing National Committee positions. You may not copy or "mirror" the file or printed version of the docum.ent, or any part of it, for any other purpose without permission in writing from lEG,

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This English language copy ofthe code is provided for educational purposes only and is not to be used for commercial.purposes. No assurances are made to the accuracy or completeness ofthe information contained herein.

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RUSSIAN LIGHTNING PROTECTION DESIGN CODE FOR BUILDINGS AND STRUCTURES RD 34.21.122-87 ThiS Code is mandatory for all government ministries and agencies. The Code defines a mandatory set ofprocedures and devices to provide safety ofhuman beings (farm ammals), buildings, structures, equipment, and materials against potential lightning-induced explosions, fires, and other types ofdamage. This Code serves as a mandatory reference source for designing buildings and structures. The Code does not cover design and construction 0/ lightning protection lor power lines, electrical modules ofelectric power plants and substations, contact lines, radio and TV antennas, cable, telephone, and radio transmission lines, or buildings and structures the operation o/which involves production, use, or storage ofordnance and explosives. This Code regulates lightning protection procedures performed during construction, and also includes the use ofadditional lightning protection measures inside a building or structure during reconstruction or insra/lation ofadditional process or electrical equipment. In addition to the Code requirements, building and structural design should also meet the lightning protection requirements ofother existing standards, regulations, instructions, and state standards.

1. General Information 1.1. In accordance with the purpose of buildings and structures) a need in lightning protection and its category, as well as types of coverage areas provided by lightning rods and lightning conductors, are defined in Table I as a function of average annual lightning storm activity at the location of buildings or structures, and of the expected number of lightning strikes per year at that location. Lightning protection must be arranged as per conditions specified in lines 3 and 4 of Table l. The assessment of the average annual lightning storm activity and expected number of lightning strikes for buildings and structures is made per Attachment 2~ various types of coverage areas are mapped per Attaclunent 3.

1.2. Buildings and structures that have lightning protection arrangement as per Categories I and II must be protected against direct lightning strikes) secondary effects) and transfer of high-voltage potential through ground surface, above- and undergroWld metal utility lines. Buildings and structures with Category III lightning protection arrangement must be protected against direct lightning strikes and transfer of high-voltage potential though ground surface (above-ground) metal utility lines. Outdoor facilities· with Category II lightning protection arrangemen~~l:lst be protected against ·direci st~es and secondary lightning effec~. ... . .. Outdoor facilities with.Category III lightning protection arrangement must be protected against direct lightning strikes. .. . . .Indoor arrangements for buildings with a large area (over 100 m ·wide) must include measures for equalizing the potential.

1.3. For buildings and structure~ that require Category I and II or Category I and III lightning protection arrangement) lightning protection of the entire building or structure must be provided per Category 1. ') This Code been developed by the: S~t~ S·cientific Ene~gy R~earch In~titute named after G.M. Krzhizhanovskyt the USSR Ministry ofEnergy~ coordinated with the USSR GosStroy (Letter#ACH-:-3945· 8 of July30,1987) and approved by the Main Technical Directorate of the USSR Ministry of Energy. This Code voids the Instruction for Design and Arrangement ofLightning Protection of Buildings, SN 305\t\\t\C} 77. Q~ \..\gt\ "8 1.1A,.\\O""'" ~\J\ .\~Q,_\'l_\ns If ~"e ~ .\-\00'4 ~'l' 89'\ ~~"e CO ~ \...OU\$"'., .

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INSTALLATION OF UGHTNlNG PROTECTION SYSTEMS 1.3 Listed. Labeled, or Approved Components. Where fit· tings, devices, or other components required by this standard are available as listed or labeled, such components shan be used,

NFPA780

Standard for the

Installation of lightning Protection Systems

1.4 Mechanical Execution of Work. Lightning protection systems shall be installed in a neat and workmanlike"manner.

2004 Edition

1.5* Maintenance. Recommended .,.", . nance of the lightning pr""~ the owner at the ,.~

document made

IMPORTANT NOTE: This NFPA is available for use wbjeet wimportant notices and legal disclai#let'$. These notices and disclaimers appear in all publicationl containing this document 1.6~"''' and ~ be found under the heading "Important Noncu and ~~. . O~ claimers Concerning NFPA Documentl. It They can also h# .' O~ 11.'

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Chapter 2 Referenced Publications

2.1 General. The documents or portions thereof listed ill this chapter are referenced within this standard and shall be con· 'd d f . . Sl ere part 0 the requIrements of thiS document. 2.2 NFPA Publication. National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02169·747l. NFPA 70 National Electrical Cork~ 2002 edition, . ' , 2.3 Other Publications. (Reserved)

Chapter 3 Defmitions 3.1 General. The definitions contained in this chapter shall apply to the terms used in this standard. Where terms are not included, common usage of the terms shall apply.

ls.2 NFPA Official Definitions.

Chapter 1 Administration 1.1 Scope. 1.1.1 This document shall cover traditional lightning protection system installation requirement5 for the following: (1) Ordinary structures

(2) (3) (4) (5)

Miscellaneous structures and special occupancies Heavy-duty SlaCks Watercraft Structures containing flammable vapors, flammable gas~s, or liquids that give off flammable vapors

. . . 1.1.2* This document shall not cover lightning protection system ins~lIation requirements for the following: (1) Explosives manufacturing buildings and magazines (2) Ele~tric generating, transmission, and distribution systems . . . 1.1.3 This document shall not cover lightning protection system installation requirements for early streamer emission systems or charge dissipation systems. 1.2 Pwipose. The purpose of this standard shall be to provide for the;safeguarding of persons and property trom hazards arising from exposure to lightning.

2004

Edl~on

3.2.1* Approved. Acceptable to the authority havingjurisdiction. 3.2.2* Authority Having Jurisdiction (AHJ). An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment. materials, an installation, or a procedure. 3.2.3 Labeled. Equipment or materials to which has been at· tached a label, symbol, or other identifYing mark of an organization that is acceptable to the authority having jurisdiction and concerned with product evaluation, that maintains periodic inspection of production of labeled eqUipment or materials, and by whose labeling the manufacturer indicates compliance with appropriate standards or perfonnance in a specified manner. 3.2.4* Usted. Equipment, materials, or services included in a list published by an organization that is acceptable to the au· thority having jurisdiction and concerned with evaluation of prodUCts or services, that maintains periodic inspection of production oflisted equipment or materials or periodic evaluation of services, and whose listing states that either the equipment, material, or service meets appropriate designated stan· dards or has been tested and found suitable for a specified purpose.

239

NCM®

GUIDELINE 1d Lightning Safety July 1997·

Re~sed

June

The NCM Committee on Competitive Safeguards and Medical Aspects of Sports acknowledges the significant input of Brian L. Bennett, formerly an athletic trainer with the· College of William and Mary Division of Sports Medicine, Ronald L. Holle, a meteorologist, formerly of the National Severe Storms Laboratory (NSSL), and Mary Ann Cooper, MD, Professor of Emergency Medicine of the University of Illinois at Chicago, in . the development of this guideline.

Lightning is the most consistent and significant weather hazard that may affect interc01{egiate athletics. Within the United States, National Oceanographic and Atmospheric Administration (NOAA) estimates that 60-70 fatalities and about 10 times as many injuries occur from lightning strikes every year. While the probability of being struck by lightning is low, the odds are significantly greater when a storm is in the area and proper safety precautions are not followed.

2006~~~~~~~~~~~~~~~~_

1. Designate a person to moni- 4. Know where the closest tor threatening weather and to safer structure or location" is to make the decision to remove a the field or playing area, and know team or individuals from an athlet- how long it takes to get to that ics site or event. Alightning safe- location. Asafer structure or locaty plan should include planned tion is defined as: instructions for participants and a. Any bUilding normally occuspectators, designation of warning pied or frequently used by peoand all clear signals, proper sigple, Le., a building with plumbnage, and designation of safer ing and/or electrical wiring that places for shelter from the lightacts to electrically ground the ning. structure. Avoid using the 2. Monitor local weather reshower or plumbing facilities ports each day before any practice and contact with electrical applior event. Be diligently aware of ances during athunderstorm. potential thunderstorms that may b. Small covered shelters are form during scheduled intercollenot safe from lightning. Duggiate athletics events or practices. outs, rain shelters, golf shelters, Weather information can be found and picnic shelters, even jf they through various means via local are properly grounded for .television news coverage, the structural safety, are usually not Internet, cable and satellite weathproperly grounded from the er programming, or the National effects of lightning and side Weather Service (NWS) homeflashes to people. They are page at http://www.weather.gov. usually very unsafe and may 3. Be informed of National actually increase the risk of Weather Service (NWS) issued lightning injury. Other dangerthunderstorm "watches" or warnous locations include areas ings," as well as the warning signs connected to, or near light of developing thunderstorms in poles, towers and fences that the area, such as high winds or can carry anearby strike to peodarkening skies. A watch" means ple. Also dangerous is any conditions are favorable for severe location that makes the person weather to develop in an area; a the highest point in the area. "warning" means that severe c.ln the absence of a sturdy, weather has been reported in an frequently inhabited building, area and for everyone to take the any vehicle with a hard metal proper precautions. A NOAA roof (neither aconvertible, nor a weather radio is particularly helpgolf cart) with the windows shut ful in providing this information. II

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Education and prevention are the keys to lightning safety. The references associated with this guideline are an excellent educational resource. Prevention should begin long before any intercollegiate athletics event or practice by being proactive and having a lightning safety plan in place. The following steps are recommended by the NCAA and NOAA to mitigate the lightning hazard:

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provides a measure of safety. The hard metal frame and roof, not the rubber tires is what pro~ tects occupants by dissipating lightning current around the vehicle and not through the occupants. It is important not to touch the metal framework of the vehicle. Some athletics events rent school buses as safer shelters to place around open courses or fields.

C. The existence of blue sky and the absence of rain are not guarantees that lightning will not strike. At least 10 percent of lightning occurs when there is no rainfall and when blue sky is often visible somewhere in the sky, especially with summer thunderstorms. Lightning can, and does, strike as far as 10 (or more) miles away from the rain shaft.

5. Lightning awareness should

phones, except in emergency situations. People have been killed while using alandline telephone during a thunderstorm. Cellular or cordless phones are safe alternatives to a landline phone, particularly if the person and the antenna are located within a safer structure or location, and if all other-precautions are followed.

be heightened at the first flash of lightning, clap of thunder, and/or other criteria such as increasing winds or darkening skies, no matter how far away. These types of activities must be treated as a warning or l(wake~up call" to inter~ collegiate athletics personnel. Specific lightning safety guidelines have been developed with the assistance of lightning safety experts: a. As aminimum, lightning safe-

ty experts strongly recommend that by the time the monitor observes 30 seconds between seeing the lightning flash and hearing its associated thunder, all individuals should have left the athletics site and reached a safer structure or location.

b. Please note that thunder may be hard to hear if there is an athletics event going on, particularly in stadia with large crowds. Implement your lightning safety plan accordingly.

d.Avoid using landline tele-

e. To resume athletics activities, lightning safety experts recommend waiting 30 minutes after both the last sound of thunder and last flash of lightning. If lightning is seen without hearing thunder, lightning may be out of range and therefore less likely to be asignificant threat. At night. be aware that lightning can be visible at a much greater distance than dur~ ing the day as clouds are being lit from the inside by lightning. This greater distance may mean that the lightning is no longer a significant threat. At night, use

both the sound of thunder and seeing the lightning channel itself to decide on re-setting the 30~minute "return-to-play" clock before resuming outdoor athletics activities.

f. People who have been struck by lightning do not carry an electrical charge. Therefore, cardiopulmonary resuscitation (CPR) is safe for the responder. If possible, an injured person should be moved to a safer location before starting CPR. Lightning-strike victims who show signs of cardiac or respiratory arrest need prompt emergency help. If you are in a 911 community, call for help. Prompt, aggressive CPR has been highly effective for the survival of victims of lightning strikes. Automatic external defibrillators (AED's) have become a common, safe and effective means of reviving persons in cardiac arrest. An AED should be considered as part of your sideline equipment. However, CPR should never be delayed while searching for an AED. Note: Weather watchers, realtime weather forecasts and commercial weather~warning devices are all tools that can be used to aid in decision-making regarding stoppage of play, evacuation and return to play.

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DESIGN LIGHTNING SAFETY FOR THESE SITUATIONS: 1. Self-supporting 150 ft. cellular radio tower. Equipment building 6X6XI0 is 15 ft. away. Radio equipment in building. Cable tray. Overhead incoming AC power. Gated fence. Perimeter light masts.

2. Guard shack 12X12X12, manned 24 X 7. Peaked roof. Drive through gates. High mast lighting. Radio antennas on building. AC power and telecomm inside. Air conditioning box on roof.

3. Row of six Earth Covered Explosive Storage Magazines each 20X40X15. Roll-up doors. Interior crane. Ventilation Stacks. High mast lighting. Perimeter fence.

4. Wastewater treatment plant. Three adjacent 100 ft. diameter uncovered steel tanks. Incoming AC power and telecom. Pumps, valves, relays, switches. Steel catwalks to all structures. Guyed radio tower 20 ft. high. Fenced.

5. Three story computer center building with flat roof. Many metal boxes on roof for water chilling, HVAC, pumps, fans, motors. 175 employees. Lighted parking lot. Trees. Picnic and recreation area outside. Secondary building 1OXI OXl 0 sharing AC power & telecomm 30 ft. away.

6. Metal shelter used as bus stop 10XIOXlO open on one side. No power. Telephone pole carrying AC power, cable and telephone services adjacent to shelter.

7. Wooden shelter on golf course 1OXl OXI 0 with four posts supporting peaked roof. Interior lights. Pop machine. Water fountain. Picnic table.

8. Industrial cement plant on five acres. Fenced. Some permanent buildings. 125 outdoor and indoor workers, 2 shifts. You are the Safety Manager. Develop a program for lightning safety for people and for electrical/electronic equipment.

Ml'11OtW. UGH1'NNG SAFETY NmIU1'E 8t1 North·fio«w8r 1we.

1OI• • co 80021-2214

242

Anonymous Critique for Workshop 1. The information presented to me was: a. Useful and applies to my work _ b. Not relevant. Needs revision ~~_------c. Too technical_. Incomplete _ _' OK, except for _ d.Other _

2. The best part of the course was: 3. The worst part of the course was: 4. Some information I need which was missing was:

_

5. The top three things I'll remember about the course are:

a.

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6. I rate the instructor as follows on a 1-10 scale: Good Presenter of Information (GPI); Knew Subject (KS); Give any constructive comments,too. a. GPI

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KS= Other=

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7. The meeeting room arrangement, choice of location,' and general logistics were OK _ ; need improvement: _ 8. Cost of the seminar was: a. about right _ b. too high_ c.other

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9. Workbooks, handout materials and visual aids were: a. Good. . Just Fair _ . OK _ _ b. Improvements Suggested _ __ _ . - - - - - - - - - 10. Others in my organization or in my industry williwill not find the Workshop beneficial. 11. There is a one day class on Inspection, Maintenance and Testing of the LPS. Would other people in your organization be Interested? (See instructor here.) 11. Other comments and opinions:

243

technical bookfrom ... NATIONAL LIGHTNING SAFETY INSTITUTE (NLSI) www.lightningsafety.com

It LIGHTNING PROTECTION FOR ENGINEERS An Illustrated Guide in Accord with Recognized Codes & Standards TABLE OF CONTENTS, Revision 3. August 2006 Part J

Lightning Physics, Lightning Behavior and Lightning Safety Overview

Part 2

Risk Assessment

Part 3

The Grounding and Bonding Imperative

Part 4

Exterior Lightning Protection for Structures

PartS

Interior Lightning Protection for the Electrical System Of a Complex Facility

Part 6

Communications Facilities, Exterior Lightning Protection

Part 7

Communications Facilities, Interior Lightning Protection

Part 8

Lightning Protection for High Risk Installations Containing Sensitive Electronics, Explosives, Munitions, or Volatile Fuels

Part 9

International Views of Unconventional Air Terminal Designs Such As ESE and CTSIDAS

Part 10

Lightning Safety for Outdoor Workers

Part JJ

References, Resources and Codes

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• • LIGHTNING PROTECTION FOR ENGINEERS - Page Index 1. Lightning Physics, Behavior and Safety Overview Chapter Overview The Convection Process Typical Waveform "Cold" vs "Hot" Lightning Log Normal Distribution Sequence of Steps in Typical Flash Streamer/Leader Lightning Behavior - Part 1 Lightning Behavior - Part 2 ACR Resistive, Magnetic & Electric Fields The Attachment Process TD/YR Worldwide Map TD/YR USA Map FDNRlSQIKM USA Little-Known Information Per NASA - The Protection Process Per NLSI - How to Get to Lightning Safety Matrix of Protection Sub-Systems Lightning Mitigation Guideline

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

2. Risk Assessment Chapter Overview Determining the Probabilities... Analysis ofNeed for Protection NLSI Version of Risk Assessment

23 24 25-28 29-39 40

3. The Grounding & Bonding Imperative Chapter Overview Definition of Terms Factors Affecting Soil Resistivity

41 42 43-45 46

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245

Types of Earth Electrode Systems Various Grounding Layouts Grounding Buildings with Basements Grounding Buildings without Basements Ground Rod Bonding Grounding Additives and Backfills Bonding Drive & Walk Gates Bonding to Fence Post "Ufer" Ground Detail Separation Distance, Grounds-to-Other Conductors Service Entry Grounding Problem with Poor Bonding Facility Bonding Detail 1 Facility Bonding Detail 2 Bonding Building Steel to Ground Ground Potential Equalization Bonding Separate Ground Rods Bonding Conduits Bonding to Prevent Side Flashing Miscellaneous Bonding Examples (MBE) 1 MBE2 MBE3 MBE4 MBE5 Hierarchy of Bonding Jumpers Bonding Jumper Inductance Bonding Technique Effectiveness Typical Connector Tenninations Bonding Inspection Checklist 4. Exterior Lightning Protection for Structures Chapter Overview Approved Air Tenninal Designs Personal Shelter, Faraday Cage Concept Free-Standing Steel Masts Overhead Wire (OHW) or Catenary Design Franklin Rods 1

47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69

70 71 72 73 74 75 77 78 79 80 81

82 83

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Franklin Rods 2 Franklin Rods 3 Function of Overhead Shield Wire (OHW) Design OHW - View 1 Design OHW - View 2 Design OHW - View 3 OHW Support Poles Details Preference for Mast & OHW per Codes Cone of Protection (CP) Model Rolling Sphere (RS) Model Comparison ofCP and RS

84 85 86 87 88 89 90 91 92 93 94

5. Interior Lightning Protection for the Electrical System Of a Complex Facility Chapter Overview Side Flash and Coupling to Building Wiring SPD Locations per IEEE SPDs Typical for Commercial Building SPDs Typical for Process Control Plant Worst Cases of Transient Insults Voltage and Current Waveforms Overview of SPD Functions Transient Limiting of Generic SPD Components Advantages & Disadvantages of SPD Components Desirable SPD Operating Characteristics Three Stage SPD Example Surge Reference Equalizer Surge Protection Checklist Recommended SPD Specifications SPD Installation Practices SPD Evaluation Form SPD Follow-Up References The Missing Surge Protector

95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114

6. Communications Facilities, Exterior Lightning Protection Chapter Overview Tower Bonding - Self Supporting Tower

115 116 117

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Tower Bonding - Guyed Tower Tower Bonding - Building Mounted Tower Grounding Configurations Optimum Grounding Under Lightning Attack Exterior Ground Plan Exterior Ground Ring Coaxial Cable Routing Bonding Coaxial Cable Shield Coaxial Cables Entering Building Grounding Checklist, Exterior

118 119 120 121 122 123 124 125 126 127

7. Communications Facilities, Interior Lightning Protection Chapter Overview Typical Interior Grounding Plan "Halo" Ground Examples of Interior Grounding & Bonding Bonding Raised Floor Bonding Interior Metallic Components Cabinet & Rack Bonding Cable Tray Bonding Details of Cable & Duct Bonding Grounding Checklist, Interior SPD & UPS Layout Typical SPD Applications SPD Checklist SPDs - Satellite Systems SPDs for Computers & CCTV Systems SPDs for LAN Systems Alternative Methods of Shielding Bonding Cable Shields Noise Reduction 1 Noise Reduction 2

129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149

8. Lightning Protection for High Risk Installations such as Electric Power Facilities, Explosives, Munitions & Volatile Fuels Chapter Overview

151 152

248

Decision Tree for Facility Lightning Safety Principles of Topological Shielding Fortress or Zone Protection Concept Preference for Mast or OSW Air Terminal Designs Errors at Critical Facilities, Parts 1 & 2 Errors at Critical Facilities, Parts 3 & 4 Going Beyond The Codes

153 154 155 156 157

158 159162

21 st Century Lightning Safety for Environments Containing Sensitive Electronics, Explosives, And Volatile Substances

163-

168 Attention to Detail 9. International View of Unconventional Air Terminals Such as "ESE" and "CTS/DAS." Chapter Overview Peer-Reviewed Technical Papers (3 Abstracts) Email from Malaysia Email from Turkey USA Court Case Concerning ESE Profs. Uman & Rakov Paper on "CTS/DASIESE" Warning of the ICLP Scientific Committee

169

171 172

173 174

175 176 177188 189-

194 10. Lightning Safety for Outdoor Activities Chapter Overview . Decision Tree for People Lightning Safety Lightning As It Originates From Clouds Pour Mechanisms of Lightning Attachment Touch and Step Potentials Instantaneous Potential Differences .. Lightning Deaths by State (1) Lightning Deaths by State (2) After Effects to Lightning Survivors Sample Policy Statement for Lightning Safety

195 196

197 198

199 200 201 202 203 204 205

Sample Poster for Outdoor Workers Sample Poster for Outdoor Recreation Sample Poster for Swimming Pools Sample Poster for Athletic Fields Sample Lightning Safety Messages Safe Shelters - Faraday Like Cage Overview of Lightning Detection Equipment

11. References, Resources and Codes Chapter Overview Glossary of Lightning Terms Annual USA Lightning Costs & Losses Helpful Lightning URLs

Review of Country Codes and the IEC 62305 Examples of Selected Codes (Cover Pages Only) IEC 62305 (www.iec.ch) AustralialNew Zealand AS/NZ 1768 British BS6651 China GB 50057-94 India IS 2309 Russia RD 34.21.122-87 Singapore CP 33 South Africa SABS 03 USA NFPA-780 USA NCAA Guideline ld Quiz - Design LPSs for Various Situations NLSI 2 Day Class Critique LP ENG Book Order Form Page Index

206 207 208 209 210 211 212213 215 216 217224 225 226227 228 229 230 231 232 233 234 235 236 237 238 239240 241 242 243 244249

SIX STAGES OF A PROJECT

1. ENTHUSIASM 2. DISENCHANTMENT 3. PANIC 4. SEARCH FOR THE GUILTY 5. PUNISHMENT OF THE INNOCENT 6. PROMOTION FOR THOSE NOT INVOLVED

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