IEEE Std 979-2012, IEEE Guide for Substation Fire Protection

IEEE Power and Energy Society

Sponsored by the Substations Committee

IEEE 3 Park Avenue New York, NY 10016-5997 USA

(Revision of IEEE Std 979-1994)

27 November 2012

Authorized licensed use limited to: Universidad Del Norte Biblioteca. Biblioteca. Downloaded on December 15,2014 at 16:23:55 UTC from IEEE Xplore. Restrictions apply.


IEEE Std 979TM-2012 (Revision of IEEE Std 979-1994)

IEEE Guide for Substation Fire Protection

Sponsor

Substations Committee of the

IEEE Power and Energy Society Approved 30 August 2012

IEEE-SA Standards Board


Figure B.1 to Figure B.5 are reprinted with permission from CEATI, Report T023700-3022, © 2005.

Abstract: Guidance is provided to substation engineers in determining the design, equipment, and practices deemed necessary for the fire protection of substations. Keywords: fire, fire protection, hazard, IEEE 979 TM, risk, safety, substation design, substations

The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright © 2012 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 27 November 2012. Printed in the United States of America. IEEE is a registered trademark in the U.S. Patent & Trademark Office, owned by the Institute of Electrical and Electronics Engineers, Incorporated. National Electrical Code and NEC are registered trademarks in the U.S. Patent & Trademark Office, owned by The National Fire Protection Association. National Electrical Safety Code and NESC are registered trademarks in the U.S. Patent & Trademark Office, owned by The Institute of Electrical and Electronics Engineers, Incorporated. PDF: Print:

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Participants At the time this guide was completed, the E3 Working Group had the following membership: Don Delcourt, Chair Hanna Abdallah Radoslav Barac Scott Bryant Randall Clelland Gary Engmann

Brian Farmer Ajay Garg Raj Ghai Joseph Gravelle Matt Hulcher Thomas La Rose

Debra Longtin Patrick McShane Bob Panero Steven Shelton Boris Shvartsberg

The following members of the individual balloting committee voted on this guide. Balloters may have voted for approval, disapproval, or abstention. Hanna Abdallah William Ackerman Ali Al Awazi Steven Alexanderson Stan Arnot Peter Balma Thomas Barnes Michael Bayer George Becker W. (Bill) J. Bergman Steven Bezner Thomas Blackburn Daniel Blaydon William Bloethe Chris Brooks Steven Brown Gustavo Brunello Scott Bryant William Byrd Thomas Callsen Robert Carruth Michael Champagne Robert Christman Randall Clelland Kurt Clemente Jerry Corkran Don Delcourt Gary Donner Michael Dood Randall Dotson Fred Elliott Gary Engmann Brian Farmer Jorge Fernandez Daher Patrick Fitzgerald Marcel Fortin

Rostyslaw Fostiak Ajay Garg George Gela David Gilmer Jalal Gohari Edwin Goodwin Joseph Gravelle Randall Groves Charles Haahr David Harris Gary Heuston Scott Hietpas Werner Hoelzl Robert Hoerauf Philip Hopkinson David Horvath R. Jackson Gael Kennedy Yuri Khersonsky James Kinney Hermann Koch Robert Konnik Jim Kulchisky Donald Laird Chung-Yiu Lam Thomas La Rose Debra Longtin Federico Lopez William McBride Patrick McShane Daleep Mohla Anne Morgan Mark Morgan Jerry Murphy Arthur Neubauer Michael S. Newman David Nichols

Gary Nissen Robert Olen Lorraine Padden Bansi Patel Christopher Petrola Alvaro Portillo Jean-Christophe Riboud Michael Roberts Edward Rowe Thomas Rozek Anne-Ma Sahazizian Daniel Sauer Bartien Sayogo Devki Sharma Gil Shultz James Smith Jeremy Smith Jerry Smith John Spare Gary Stoedter Brian Story David Tepen Malcolm Thaden Wayne Timm Eric Udren John Vergis Loren Wagenaar David Wallach Barry Ward Joe Watson Yingli Wen Donald Wengerter Kenneth White Alexander Wong Roland Youngberg Luis Zambrano

vi Copyright © 2012 IEEE. All rights reserved.


When the IEEE-SA Standards Board approved this standard on 30 August 2012, it had the following membership: Richard H. Hulett, Chair John Kulick , Vice Chair Robert Grow, Past Chair Konstantinos Karachalios, Secretary Satish Aggarwal Masayuki Ariyoshi Peter Balma William Bartley Ted Burse Clint Chaplin Wael Diab Jean-Philippe Faure

Alexander Gelman Paul Houzé Jim Hughes Young Kyun Kim Joseph L. Koepfinger* David J. Law Thomas Lee Hung Ling

Oleg Logvinov Ted Olsen Gary Robinson Jon Walter Rosdahl Mike Seavey Yatin Trivedi Phil Winston Yu Yuan

*Member Emeritus

Also included are the following nonvoting IEEE-SA Standards Board liaisons: Richard DeBlasio, DOE Representative Michael Janezic, NIST Representative

Don Messina IEEE Standards Program Manager, Document Development Malia Zaman IEEE Client Services Manager, Professional Services

vii Copyright © 2012 IEEE. All rights reserved.


Introduction This introduction is not part of IEEE Std 979-2012, IEEE Guide for Substation Fire Protection.

Since the original edition of IEEE Std 979 (issued in 1994 and reaffirmed in 2004) was prepared, the body of knowledge on fire protection has increased significantly. This revision captures much of this knowledge and presents it for use by both the substation designer and the fire protection professional.

viii Copyright © 2012 IEEE. All rights reserved.


Contents 1. Overview .................................................................................................................................................... 1 1.1 Scope ................................................................................................................................................... 1 1.2 Purpose ................................................................................................................................................ 1 1.3 General ................................................................................................................................................ 1 2. Normative references.................................................................................................................................. 3 3. Definitions .................................................................................................................................................. 3 3.1 General terms....................................................................................................................................... 4 3.2 Fire-suppression system terms ............................................................................................................. 4 3.3 Fire detection system terms ................................................................................................................. 5 4. Fire hazards ................................................................................................................................................ 6 4.1 General ................................................................................................................................................ 6 4.2 Combustible oil hazards ...................................................................................................................... 6 4.3 Flammable and combustible liquid and gas hazards............................................................................ 7 4.4 Fire exposure hazards .......................................................................................................................... 7 4.5 Indoor substation hazards .................................................................................................................... 8 4.6 Critical loss assets ................................................................................................................................ 8 4.7 Maintenance and construction ............................................................................................................. 9 5. Fire protection considerations for substation sites ...................................................................................... 9 5.1 General ................................................................................................................................................ 9 5.2 External exposures ............................................................................................................................... 9 5.3 Site grading ........................................................................................................................................ 10 5.4 Prevailing winds ................................................................................................................................ 11 5.5 Fire emergency response capability ................................................................................................... 11 5.6 Available firefighting water supplies ................................................................................................. 11 5.7 Emergency access to the substation ................................................................................................... 11 6. Fire protection for substation buildings .................................................................................................... 12 6.1 General .............................................................................................................................................. 12 6.2 Use and occupancy ............................................................................................................................ 12 6.3 Underground substations ................................................................................................................... 13 6.4 High-rise substations ......................................................................................................................... 13 6.5 Indoor substations .............................................................................................................................. 14 6.6 Construction ...................................................................................................................................... 14 6.7 Fire alarm and detection systems ....................................................................................................... 18 6.8 Fire suppression ................................................................................................................................. 18 6.9 Life safety.......................................................................................................................................... 19 6.10 Combustible materials ..................................................................................................................... 20 7. Fire protection for substations .................................................................................................................. 20 7.1 Spatial separation of outdoor mineral-oil-insulated equipment ......................................................... 20 7.2 Prescriptive separation requirements ................................................................................................. 21 7.3 Calculated separation requirements ................................................................................................... 23 7.4 Ground surface material .................................................................................................................... 23 7.5 Cable raceway systems ...................................................................................................................... 23 7.6 Water supply ...................................................................................................................................... 25 7.7 Fire extinguishers .............................................................................................................................. 25

ix Copyright © 2012 IEEE. All rights reserved.


8. Fire protection for equipment ................................................................................................................... 8.1 Oil-spill-containment systems ........................................................................................................... 8.2 Stone flame suppression .................................................................................................................... 8.3 Fire barriers ....................................................................................................................................... 8.4 Fire-suppression systems ................................................................................................................... 8.5 Explosion suppression ....................................................................................................................... 8.6 Equipment design ..............................................................................................................................

25 25 26 27 27 28 29

9. Fire protection measures selection ........................................................................................................... 29 9.1 General .............................................................................................................................................. 29 9.2 Fire protection objectives .................................................................................................................. 29 9.3 Performance factors ........................................................................................................................... 29 9.4 Life cycle factors ............................................................................................................................... 30 9.5 Risk-based economic analysis ........................................................................................................... 30 9.6 Benefit/cost analysis .......................................................................................................................... 30 Annex A (normative) Additional information to main body clauses............................................................ 32 Annex B (informative) Quantitative methods for analysis of hazards.......................................................... 47 Annex C (informative) Selection of fire protection systems and substation design ..................................... 56 Annex D (informative) Fire emergency plan, incident management, and recovery ..................................... 65 Annex E (informative) Examples ................................................................................................................. 69 Annex F (informative) Bibliography ............................................................................................................ 84

x Copyright © 2012 IEEE. All rights reserved.


IEEE Guide for Substation Fire Protection

IMPORTANT NOTICE: IEEE Standards documents are not intended to ensure safety, health, or environmental protection, or ensure against interference with or from other devices or networks. Implementers of IEEE Standards documents are responsible for determining and complying with all appropriate safety, security, environmental, health, and interference protection practices and all applicable laws and regulations. This IEEE document is made available for use subject to important notices and legal disclaimers. These notices and disclaimers appear in all publications containing this document and may be found under the heading “Important Notice” or “Important Notices and Disclaimers Concerning IEEE Documents.” They can also be obtained on request from IEEE or viewed at http://standards.ieee.org/IPR/disclaimers.html .

1. Overview

1.1 Scope The original guide (1994) was developed to identify substation fire protection practices that generally have been accepted by industry. This revision includes changes in industry practices for substation fire protection. New clauses on fire hazard assessment and pre-fire planning have been added.

1.2 Purpose The purpose of the original guide (1994) was to give design guidance, fire hazard assessment, and pre-fire planning in the area of fire protection to substation engineers. Existing fire protection standards, guides, and so on that may aid in the design of specific substations or substation components are listed in Annex F. This revision updates that guidance.

1.3 General The guide outlines substation fire protection practices based on industry standards and good practices. It incorporates lessons learned from substation fires, substation fire protection research and testing, advancements in fire protection engineering practices, and changes in fire protection due to risk and

1 Copyright © 2012 IEEE. All rights reserved.


IEEE Std 979-2012 IEEE Guide for Substation Fire Protection

environmental concerns. The guide provides design guidance in the area of fire protection for substation engineers and others involved in substation fire safety and protection. The predominant dielectric insulating fluid for transformers is mineral oil, and mineral oil constitutes one of the primary fire hazards in the substation. Consequently, much of this guide addresses hazards and protection measures based on mineral oil fires. There are several alternative fluids with improved fire safety properties (higher flash and fire points), known as “less-flammable” dielectric fluids, which have been introduced. Many of these fluids have been recognized as reducing the hazard and the risk of a fire occurring relative to mineral oil. Use of a “less flammable” fluid is one means to reduce the risk of fire at a substation. See 8.4.2 and A.21 for additional information on these fluids. It is the intent of this guide that the analysis and decisions made may require the use of a team approach comprising various specialists. These specialists will be able to provide specific guidance on their areas of expertise; provide interpretation of the related codes, standards, and practices; and help formulate fire protection solutions. The following are some of the specialists that could be involved: 

Substation design engineers (civil, electrical, mechanical, and structural)



Substation operation and maintenance staff



Fire protection engineers and specialists



The local fire department



The authority having jurisdiction over the substation



Architects and code consultants

This guide provides fire protection guidance for the following types of substations that have the principal power delivery functions accomplished with alternating current (ac) or direct current (dc) power and are operated at voltages of 1 kV and above: 

Generating plant switchyards



Customer substations



Switching substations



Transmission substations



Distribution substations



Capacitor substations



Converter station switchyards

The types of substations listed can be designed in a number of different configurations and layouts as follows: 

Outdoor substations



Indoor substations



Multistory above-grade substations



Multistory below-grade substations



Substations in mixed-use buildings including high-rise (>22.9 m) buildings



Substations in conjunction with other related operations (e.g., offices, maintenance facilities, and control centers)




This guide provides electric power engineers and fire protection professionals with fire protection and safety guidelines for application in the planning, design, and operation of substations. Guidelines are outlined in the following critical areas of application: 

The identification of substation fire hazards



The fire protection aspects for substation sites, buildings, and switchyards



Issues to be considered when selecting the various types and levels of fire protection



Recommended typical fire protection applications



Fire planning and incident management

This guide is not intended to be the primary standard for the minimum levels of fire protection required for new and existing substations. The minimum required level of substation fire safety and protection is based on the minimum requirements of governing authorities and on the level of risk the asset owner is willing to accept. This guide provides design options and strategies for the mitigation of substation fire hazards once the minimum required level of substation fire safety and protection is determined. The application of this guide is not meant to take precedence over local building, fire, safety, and electrical codes. It is intended to be used in conjunction with these governing codes and standards for the purpose of providing specialized substation fire protection guidance for asset protection and customer service reliability. This document does not necessarily cover aspects of life safety covered by local building, fire, safety, and electrical codes. Refer to A.1 for additional information.

2. Normative references The following referenced documents are indispensable for the application of this document (i.e., they must be understood and used, so each referenced document is cited in text and its relationship to t his document is explained). For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies. IEEE Std 980TM, IEEE Guide for Containment and Control of Oil Spills in Substations.1, 2 NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations.3 NFPA 851, Recommended Practice for Fire Protection for Hydroelectric Generating Plants. When exploring the additional information in NFPA 850 and NFPA 851, keep in mind that these documents were developed for generating facilities that have different hazards and risks than transmission and distribution substations.

3. Definitions For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary Online should be consulted for terms not defined in this clause.4 1

The IEEE standards or products referred to in this clause are trademarks of The Institute of Electrical and Electronics Engineers, Inc. IEEE publications are available from The Institute of Electrical and Electronics Engineers ( http://standards.ieee.org/). 3 NFPA publications are available from the National Fire Protection Association (http://www.nfpa.org/). 2




3.1 General terms control building: A building or structure in a substation that contains protection, control, system control and data acquisition (SCADA), and telecommunications equipment, electrical panels, battery banks, and other auxiliary equipment. In this guide, this term may be used interchangeably with other commonly used terms such as control house or control enclosure. fire protection: The study and application of measures to prevent, detect, extinguish, control, or deal with fires, and the subsequent impact on people, assets, business activities, or the environment. hazard: Any source of potential damage, harm, or adverse health effects on something or someone under certain conditions at work. risk: The chance or probability that a person will be harmed or experience an adverse health effect if exposed to a hazard. It may also apply to situations with property or equipment loss. switchyard: The outdoor portion of a substation with only a single voltage level. In multivoltage substations, the switchyards are typically connected by one or more power transformers.

3.2 Fire-suppression system terms clean agent gas fire extinguishing systems: A fire protection system that uses clean gaseous agents that are (1) electrically nonconducting, (2) volatile or gaseous, and (3) do not leave a residue on evaporation. The system discharges the agent for the purpose of achieving a specified minimum agent concentration throughout a hazard volume. A clean agent complies with restrictions on the production of certain Halon fire extinguishing agents under the Montreal Protocol signed September 16, 1987. deluge sprinkler system: A sprinkler system employing open sprinklers that are attached to a piping system that is connected to a water supply through a valve that is opened by the operation of a detection system installed in the same areas as the sprinklers. When this valve opens, water flows into the piping system and discharges from all sprinklers attached t hereto. double interlock preaction sprinkler system: A Preaction system that admits water to sprinkler piping on operation of both detection devices and automatic sprinklers and only discharges from opened sprinklers. This type of arrangement provides the most redundancy to reduce the probability of accidental sprinkler discharge by requiring both detection devices and sprinklers to activate independently prior to water being admitted to the piping network. This type of arrangement also allows for pressure monitoring to detect leaks in the piping network or open sprinklers prior to water being admitted to the system. dry pipe sprinkler system: A system employing automatic sprinklers that are attached to a piping system containing air or nitrogen under pressure, the release of which (as from the opening of a sprinkler) permits the water pressure to open a valve known as a dry pipe valve, and the water then flows into the piping system and out the opened sprinklers. foam-water system: A sprinkler system that generates a foam-water solution and discharges it onto the hazard to be protected utilizing air-aspirating foam-water sprinklers or nozzles or non–air-aspirating standard sprinklers. overhead sprinkler system: The installation includes at least one automatic water supply that supplies one or more systems. The portion of the sprinkler system above ground is a network of specially sized or hydraulically designed piping installed in a building, structure, or area, generally overhead, and to which 4

The IEEE Standards Dictionary Online subscription is available at http://www.ieee.org/portal/innovate/products/standard/ standards_dictionary.html.




sprinklers are attached in a systematic pattern. Each system has a control valve located in the system riser or its supply piping. Each sprinkler system includes a device for actuating an alarm when the system is in operation. The installation includes at least one automatic water supply that supplies one or more systems. The system is usually activated by heat from a fire and discharges water over the fire area. single interlock preaction sprinkler system: A single interlock system is a Preaction system that admits water-to-sprinkler piping upon operation of detection devices and discharges out only the opened sprinklers. This type of arrangement reduces the probability of accidental sprinkler discharge by requiring the activation of a detection device prior to admitting water to the sprinkler piping and then requiring a sprinkler head to open prior to water flow. water mist system: A distribution system connected to a water supply or water and atomizing media supplies that is equipped with one or more nozzles capable of delivering water mist intended to control, suppress, or extinguish fires. Water mist systems must only be used for applications that they are listed for or where specific research and testing has validated t he application. water-oscillating monitor: Typically a supplement to an overhead sprinkler or foam system, they provide additional delivery of the liquid suppression agent to areas shadowed from the overhead sprinkler system. wet pipe sprinkler system: A sprinkler system utilizing automatic sprinklers attached to a piping system containing water and connected to a water supply so that water discharges immediately from sprinklers opened by heat from a fire. video image detection: The principle of using automatic analysis of real-time video images to detect the presence of smoke or flame.

3.3 Fire detection system terms beam detector: A type of photoelectric light obscuration smoke detector where the beam spans the protected area. dry-pilot line detector: A system of heat detection employing automatic sprinklers on a pressurized dry pipe network. The activation of a sprinkler causes a loss in system pressure, which is annunciated as an alarm signal. electronic heat detector: A fire detector that detects either an abnormally high temperature or a rate of temperature rise or both. linear heat detector: A heat-sensitive cable that has a fixed alarm temperature rating or a heat-sensitive cable in which the impedance with changes in temperature can be adjusted to specific resistance levels to establish alarm temperature thresholds. optical flame detector (IR3): A flame detection device sensitive to various portions of the infrared spectrum commonly emitted from flaming fires. This type of fire detection is not sensitive to smoldering fires, and detection is limited to each sensor’s field of view. pneumatic rate-of-rise heat detector: A line-type detector comprising small-diameter tubing, usually copper, which is installed throughout the protected area. The tubing is terminated in a detector unit containing diaphragms and associated contacts set to actuate at a predetermined pressure. The system is sealed except for calibrated vents that compensate for normal changes in temperature.




smoke aspirating system: The principle of using an air sample drawn from the protected area into a highhumidity chamber combined with a lowering of chamber pressure to create an environment in which the resultant moisture in the air condenses on any smoke particles present, forming a cloud. The cloud density is measured by a photoelectric principle. The density signal is processed and used to convey an alarm condition when it meets preset criteria. spot-type ionization detector : The principle of using a small amount of radioactive material to ionize the air between two differentially charged electrodes to sense the presence of smoke particles. Smoke particles entering the ionization volume decrease the conductance of the air by reducing ion mobility. The reduced conductance signal is processed and used to convey an alarm condition when it meets preset criteria. This type of smoke detection is best applied to flaming or incipient fires in which small particulate matter is produced. spot-type photoelectric detector: The principle of using a light source and a photosensitive sensor onto which the principal portion of the source emissions is focused. When smoke particles enter the light path, some of the light is scattered and some is absorbed, thereby reducing the light reaching the receiving sensor. The light reduction signal is processed and used to convey an alarm condition when it meets preset criteria. This type of smoke detection is best applied to fires in which larger particulate matter is produced. wet-pilot line detector: A system of heat detection employing automatic sprinklers on a pressurized wet pipe network. The activation of a sprinkler causes a loss in system pressure, which is annunciated as an alarm signal.

4. Fire hazards

4.1 General The impact of fire hazards on health, safety, continuity of operations, and asset preservation is a reason to provide fire prevention, fire protection, and other fire safety measures. Fire hazards are the conditions that create the potential for a fire. Fire hazards have at least the following attributes: 

The magnitude of a possible fire



The consequence of the potential loss



The probability of an occurrence over a period of time (i.e., risk)

Subclauses 4.2 through 4.7 present recognized fire hazards found in substations. Refer to A.2 for additional information.

4.2 Combustible oil hazards Based on mass and potential for energy release, mineral-oil-insulated equipment is normally the largest fuel source present in most substations. Mineral-oil-insulated equipment includes the following: a)

Transformers and reactors 1)

Main tanks

2)

Bushings

3)

Radiators 6 Copyright © 2012 IEEE. All rights reserved.



4)

Conservator tanks

5)

Tap changers

6)

Cooling pumps

b)

Instrument transformers

c)

Voltage regulators

d)

Circuit breakers

e)

Cables 1)

Oil insulated

2)

Pipe type

3)

Potheads

4)

Transition joints

f)

Capacitors

g)

Lubricating oil systems (e.g., for synchronous condensers)

h)

Oil pump houses

i)

Oil processing plants

4.3 Flammable and combustible liquid and gas hazards Other equipment-related fuel sources that may be found at substations include the following: a)

Hydrogen-cooled synchronous condensers

b)

Oxy-acetylene used for maintenance and construction purposes

c)

Battery rooms 1)

Heat from short circuits or thermal runaway

2)

Hydrogen gas generated by battery charging

d)

Diesel- or propane-fueled generators and fuel cells for backup power

e)

Propane heating fuels

f)

Flammable and combustible liquid storage, handling, and dispensing

4.4 Fire exposure hazards Critical substation equipment and other assets can be compromised due to external fire exposures in addition to internal failure modes. Some example of exposure hazards include the following: a)

Auxiliary structures 1)

Office areas

2)

Warehouse areas

3)

Oil storage areas

4)

Shop areas




5)

Stand-by diesel generator buildings

6)

Hazardous materials storage areas

b)

Any building, room, or support structure that is of combustible construction

c)

Miscellaneous combustible storage

d)

Vegetation (nearby forests, hedges, and shrubs).

4.5 Indoor substation hazards Indoor substations present a unique set of hazards requiring a higher level of fire protection for the following reasons: 

Any smoke and other products of combustion contained in the building can create an exposure hazard to building occupants, emergency personnel, and possibly a corrosive exposure to critical substation equipment.



Heat (flame impingement, radiative and convective exposures) and the blast pressures from fires and explosions contained within the structure can expose the structure and/or equipment to damage.



The egress of building occupants and access by emergency personnel for manual firefighting and rescue operations can be complicated by the smoke, heat, structural damage, and travel distances.

4.6 Critical loss assets The following are critical elements of a substation that if destroyed or damaged can impact the substation’s ability to function: a)

Control, computer, protection, switchgear rooms, and equipment 1)

System protection equipment

2)

Communication equipment

3)

SCADA equipment

4)

Computers

b)

Cable spreading areas, cable trenches, cable tunnels, and cable vaults

c)

Batteries and charger systems

d)

Station service transformers (dry or liquid fil led)

e)

Power transformers

f)

Circuit breakers

g)

Bus structures

h)

Auxiliary equipment

The annexes provide more information on fire hazards and their potential impacts.




4.7 Maintenance and construction Maintenance and construction activities can create high-risk conditions within substations. The following equipment and activities could present hazardous conditions: a)

Oil-processing equipment

b)

Mobile transformers

c)

Painting

d)

Hot work (cutting, grinding, and welding)

e)

Maintenance activities

f)

Increased fire exposure and fuel load associated with 1)

Temporary or permanent construction

2)

Combustibles and flammable transient fire loads (e.g., fuel cans, rags, and wood)

3)

Material and equipment storage

4)

Office trailers

5)

Parked vehicles

5. Fire protection considerations for substation sites

5.1 General The following should be considered during new site selection or existing site analysis: 

External exposures



Site grades



Available firefighting water supplies



Emergency access to the substation



Fire emergency response capability



Prevailing winds



Environmental consideration

Refer to A.3 for additional information.

5.2 External exposures External exposures are fire hazards external to the substation. A fire involving these external hazards has the potential to impact substation operations adversely and may spread into the substation with more significant consequences. A review of site fire exposures should consider all of the following: 

Type of exposure and possible spread mechanisms



Level of existing protection present in the external exposure






Risks involved



Additional fire protection features required to create an acceptable level of risk

Subclauses 5.2.1 through 5.2.3 discuss some typical external hazards. ANSI/NFPA 80A-2012 [B30] 5 provides a method for the analysis and mitigation of external radiant heat threats from these types of exposures.

5.2.1 Forested or grassland areas Forest and grass fires can expose the substation to conductive smoke, fire plumes, radiant heat, and soot. Generally, unplanned landscaping, trees, and vegetation should be removed for a minimum of 9.1 m (30 ft) beyond critical buildings, structures, and equipment. In addition, vertical vegetation (i.e., trees) heights should be analyzed to minimize fall potentials that exist within 9.1 m (30 ft) of operational critical buildings and equipment. Refer to A.4 for additional information.

5.2.2 Hazardous industries or operations Chemical plants, petroleum refineries, liquefied natural gas plants, and compressed gas tank farms are examples of neighboring facilities that could pose an external threat to substation operations should an emergency or fire occur at the neighboring site. Spatial separation or other fire protection methods should be used to protect the substation from these types of external threats.

5.2.3 Combustible buildings Nearby combustible buildings and warehouses often represent substantial fuel loads that can expose the substation to conductive smoke, fire plumes, radiant heat, and soot. Spatial separation or other fire protection methods should be used to protect the substation from these types of external threats. Refer to 7.2.4 for additional information and other reference documents such as ANSI/NFPA 80A-2012 [B30]. Temporary enclosures made of combustible materials and temporary heating for construction activities require special considerations for fire prevention. Issues include providing safe heating sources and isolation of combustible materials from hot work. Wherever possible, buildings used to support the operation of a substation (e.g., offices and warehouses) should be located outside the substation fence.

5.3 Site grading Mineral oil spill fires can spread long distances over a wide area, potentially exposing critical elements of the substation to fire. In addition, oil can cause environmental impacts if it reaches nearby environmentally sensitive areas such as streams and rivers or is absorbed into the ground. One of the most critical factors that can impact the fire protection of substation equipment and buildings is the site grading. Special attention should be paid to site grading conditions, spatial separation, and overall substation layout to minimize the degree and direction of oil spread.

5

The numbers in brackets correspond to those of the bibliography in Annex F.




5.4 Prevailing winds The prevailing wind direction should be taken into consideration when determining mineral-oil-insulated equipment locations. The prevailing winds can create an increase in the hazard from fires involving mineral-oil-insulated equipment and combustible structures. In a fire situation, the wind can cause the flame and fire plume to tilt. This can result in higher heat fluxes, smoke concentrations, and soot levels at downwind buildings or equipment. Additional fire protection measures may be considered when the wind is found to increase the fire hazard. Refer to A.5 for additional information.

5.5 Fire emergency response capability The fire response time and resources of either internal fire brigades or local fire departments are important factors in determining the required level of fire protection. The substation designer should consider these factors in the selection of fire protection mitigating measures in the substation design. Refer to A.6 for additional information.

5.6 Available firefighting water supplies In the event of a fire in the substation buildings or mineral-oil-insulated equipment, water is the most commonly used fire-extinguishing agent. As part of the design process, the available firefighting water supplies should be reviewed. Available water supply is an important design attribute for both automatic suppression systems that may be considered as well as for responding fire departments or fire brigades. Refer to A.7 for additional information.

5.7 Emergency access to the substation Access roads should be designed to accommodate emergency response vehicles. Provisions for emergency access at two locations should be considered around the station yard. Where feasible, vehicle entry gates should conform to the following: 

Not be located beneath overhead power lines



Not be adjacent to fire hazards (such as mineral-oil-insulated transformers) that could cause them to be blocked during an incident



Be located as far apart as practical (a minimum of one half the overall station diagonal is recommended)





6. Fire protection for substation buildings

6.1 General Substation buildings should be designed in accordance with applicable local building codes. In the absence of applicable building code requirements, the following recommendations may be followed for the design and construction of substation buildings. Fire protection may be applied to substation buildings that meet one or more of the following criteria or where fire protection is required by lo cal codes: 

The building area is greater than 1000 m2 (10 000 ft2).



The building is multistory.



The building contains mineral-oil-insulated equipment.

As a minimum, all new substation buildings should be of noncombustible construction and should include the life safety recommendations in 6.9.

6.2 Use and occupancy In the absence of explicit local building code classification criteria, electrical equipment buildings and battery buildings should be classified as special-purpose industrial occupancies. Warehouse buildings should be classified as storage occupancies. Maintenance shop areas should be considered as industrial occupancies. Office areas separate from control building spaces should be considered business occupancies. Refer to A.9 for additional information.

6.2.1 Control buildings and rooms Control buildings and rooms should be reserved for control equipment, metering equipment, SCADA equipment, telemetry and communications equipment, low-voltage (<1 kV) station service distribution equipment, metal-enclosed (non–oil-filled) switchgear cubicles and associated relays, and minimal work and office areas necessary to facilitate these operations. U ses for other purposes should be discouraged. Storage of paper products (drawings, test reports, and instruction books), cleaning fluids, and other combustible supplies in a control building are discouraged. If stored in the control building, then they should be stored in separated areas with a 1 h or 2 h fire separation rating based on the hazard or in cabinets to preclude a fire from spreading to the main control and relay areas (see A.11). Flammable liquids should only be stored in approved containers and/or cabinets. Welding and other flammable gases should never be stored in control buildings.

6.2.2 Battery rooms and areas Battery main terminals and connections between the main battery terminals and the battery overcurrent protection should be designed with insulation or separation to minimize short circuits during maintenance and normal activities in the area of the battery. Battery rooms or areas in control buildings need adequate ventilation. The flash arresting vents on battery cells should be maintained to provide adequate diffusion of




hydrogen and oxygen gases that evolve on battery charging. The maintenance should be to clean and/or replace the flash arresters so the dissipation of gases can be accomplished without an appreciable pressure buildup inside the battery cell jar. Battery rooms and areas should be designed based on the requirements of the applicable safety and electrical codes. Further guidance may be obtained from IEEE Std 484TM-2002 [B67].

6.2.3 Support buildings and separated areas Office facilities for functions not directly related to substation control should be housed in buildings separate from the substation control building or in areas separated by fire-rated construction provided in accordance with the separation provisions of A.11. Maintenance buildings may incorporate indoor storage of substation equipment and supplies.

6.3 Underground substations Underground substations create high fire safety and fire protection risks that require a high level of fire protection. Generally, underground substations are special structures and can create the following challenges: 

Egress



Firefighting access



Smoke and heat venting



Automatic control of ventilation equipment



Blast pressure venting



Water containment



Presence of mineral-oil-insulated cable and electrical equipment


6.4 High-rise substations The incorporation of substations in high-rise building (office buildings) may create significant hazards to the building and building occupants. The following substation-related hazards are examples that may create exposures to the other parts of the building: 

Smoke and heat migration



Fire exposure and blast impact to building support structures






Water used for firefighting and fire protection





6.5 Indoor substations Indoor substations create higher fire safety and fire protection hazards than outdoor substations and require a higher level of fire protection. Generally, these substations are special structures and may have some of the following challenges: 

Egress



Firefighting access



Smoke and heat venting



Automatic control of ventilation equipment



Blast pressure venting



Water containment





6.6 Construction Refer to A.10 for additional information.

6.6.1 Building materials Materials used in the construction of substation buildings should be noncombustible or limited combustible (e.g., gypsum wallboard). High-rise building areas containing mineral-oil-insulated equipment or cables should incorporate performance-based fire and blast resistance to protect structural elements.

6.6.2 Fire separation Fire separations should be installed between adjacent occupancies with different uses within the same building. Required minimum fire-resistance ratings for fire separation should be obtained from applicable building codes. Exception:

Self-contained modular substation packages consisting of buildings with switchgear (metal-clad or gas-insulated switchgear), control equipment, and auxiliary equipment may be treated as single use. Fire separation may be eliminated between the different areas provided there is a realization that the entire module may be lost if a fire were to occur. Refer to A.11 for additional information.

6.6.3 Floor and roof Flooring should be noncombustible such as steel or concrete (with or without floor trenches) or raised flooring.




Roof covering should be constructed in accordance with ANSI/NFPA 256-2003 [B38]: “Class A” rated requirements for a high-resistance ignition and burning. The roof supporting structural assembly should be of noncombustible construction. Blast pressure venting devices on the roof should be considered when the power transformer is located in a full enclosure (i.e., four walls and a roof). Roof assemblies using foam plastic roof insulation should be constructed in accordance with Factory Mutual “Class 1” requirements. These requirements are designed to provide roof assemblies that will not contribute materially to flame spread on the underside of a roof when exposed to an interior fire exposure. Refer to A.12 for additional information.

6.6.4 Cable trays Cable trays should be constructed of noncombustible materials. Vertical tray routings not protected by automatic sprinklers and 6.1 m (20 ft) or greater in height, but less than 9.1 m (30 ft) in height, should have fire breaks installed at mid-height and for runs 9.1 m (30 ft) or greater height, at 4.6 m (15 ft) intervals. Fire break designs should prevent the propagation of fire for a minimum of 30 min when tested for the largest number of cable routings and cable density. Penetrations of cable trays through firewalls, floors, and ceilings should be provided with fire breaks, seals, or fire stops conforming to requirements of ANSI/IEEE 634-2004 [B6] and should have an equal or greater fire-resistance rating than the wall or floor being penetrated. The cable trays should be separated by a distance sufficient to minimize the propagation of a fire from one tray to another. If flame-retardant cables are utilized, then the recommended separation distances are given in IEEE Std 384TM-2008 [B65] and ANSI/IEEE 525-1992 [B4]. If cables are not flame retardant or the proper separation cannot be achieved, then a fire-resistive barrier or shield can be used between the trays or a fire-retardant coating may be applied to the cables. Fire hazards can also be minimized by utilizing fire stops. The possible ampacity derating due to the thermal insulating properties of the fire break or fire stop material should be taken into account.

6.6.5 Conduits and cables Conduits should be made of noncombustible materials. Penetrations of conduits and cables through firewalls should be provided with a fire break or seal conforming to requirements of the applicable codes and ANSI/IEEE 634-2004 [B6] at ceiling, wall, and floor penetrations. Fire stopping used should have an equal or greater fire-resistance rating than the wall or floor being penetrated. Conduit and cable penetrations through building dividing walls, fire separations, smoke separations, and firewalls should be sealed to prevent the spread of smoke and fire from a potential fire area to other areas. The use of fire-retardant cable, such as those passing the flame propagation test of ANSI/IEEE 383-1974 [B3], is recommended. Grouped electrical cables should be routed away from exposure hazards (major switchgear and sources of flammable and combustible liquids) or provided with suitable fire protection measures to offset the risk. Where possible, high-voltage cable trays should be located above or remote from low-voltage cable trays to lessen the exposure hazard to the lower vol tage cables. Care should be taken in the selection of fire-retardant coatings, wraps, or tapes as they may derate the cable ampacity, and this needs to be considered in the design.




Use of mineral-oil-insulated cables within buildings should be discouraged or protected with an automatic fire-suppression system.

6.6.6 Building openings Guidance on the installation and maintenance of assemblies and devices used to protect openings in walls, floors, and ceilings against the spread of fire and smoke within, into, or out of buildings can be found in ANSI/NFPA 80-2013 [B29] and local building codes. All doors and windows installed in rated separations should have a minimum fire-resistance rating equal to that of the separation. Protected openings (doors and windows) in 2 h fire separations may have a reduced rating of 1.5 h. All doors should be equipped with self-closing devices. Fire-resistance-rated fire shutters should be installed on operable windows installed in rated walls unless no exposure hazard exists (i.e., does not open to another room, building, or piece of equipment). Shutters should have a minimum fire-resistance rating equal to that of the wall. Refer to A.13 for additional information.

6.6.7 Interior finish Guidance on interior finishes can be found in Section 10.2 of ANSI/NFPA 101-2011 [B34] and local building and fire codes. Interior finish in substation buildings should have a low flame spread and smoke development characteristics as required by local codes and standards. Cellular and foam plastic materials (as defined in Annex A of ANSI/NFPA 101-2011 [B34]) are not recommended as interior finishes. If used, these types of wall coverings should be covered with a minimum 13 mm (0.5 in) fire-resistance-rated gypsum wallboard on the fire-exposed side. Plywood used as a wall backing for securing panels or equipment should be fire retardant or painted with fire retardant paint.

6.6.8 Lightning protection Lightning strikes to substations can ignite flammable materials and damage equipment that can lead to fires. Lightning protection may be provided in accordance with IEEE Std 998 TM-1996 [B69] or ANSI/NFPA 780-2011 [B42] as applicable.

6.6.9 Furnishings The use of combustible materials should be avoided in the selection of desks, chairs, filing cabinets, storage boxes, display boards, and so on. Guidance on contents and furnishings can be found in Section 10.2 of ANSI/NFPA 101-2011 [B34].

6.6.10 Heating, ventilating, and air conditioning (HVAC) systems The design of HVAC systems should be based on the fire hazards of the specific areas serviced by these systems. In general, the HVAC systems should be designed to shut down in the event of a fire to prevent




the spread of smoke throughout the building. Guidance on HVAC shutdown can be found in ANSI/NFPA 90B-2012 [B32]. HVAC systems may incorporate a means for fire department or brigade personnel to control (shutdown, startup, or override the controls) the HVAC systems manually during a fire incident. The fire department or brigade should be contacted for guidance as to whether such controls would b e useful on the HVAC system in question. Where provided, these controls should be located in an area that is expected to be accessible during a fire event. The fresh air supply intakes for HVAC systems should be located to minimize the possibility of drawing smoke into the system. Where this is not possible, the intakes should be installed with automatic smoke dampers. All ductwork should be of noncombustible construction. Where the HVAC system penetrates fire-resistance-rated separations (i.e., rated walls and floors), fire dampers with a minimum fire protection rating equal to the penetrated fire separation should be installed. Where the HVAC system traverses areas where smoke could create fire safety or protection problems, suitable smoke dampers should be installed. Refer to A.14 for additional information

6.6.11 Smoke and heat management A smoke and heat management scheme should be incorporated into the design of underground, high-rise, and indoor substations. Venting heat and smoke creates more tenable conditions for responding fire department personnel and occupants that are trapped or trying to exit the building safely. Smoke and heat vents are one option to achieve more tenable firefighting conditions. Additional guidance on the design of smoke and heat vents can be obtained in ANSI/NFPA 204M-1991 [B36]. Mechanical smoke control pressurization systems are another option in achieving more tenable fire conditions in the protected space. Additional guidance on the design of smoke control can be found in ANSI/NFPA 92A2009 [B33]. In control rooms, relay rooms, and computer rooms where a dedicated HVAC system serves these spaces, it may be appropriate during fire conditions to continue to run the HVAC in the 100% fresh air and relief air mode to reduce the impact of heat and smoke on the critical electrical and electronic components. Refer to A.15 for additional information.

6.6.12 Drainage Provisions around indoor mineral-oil-insulated equipment should be made in each building for removal of liquids directly to safe areas or for containment in the fire area without endangering other areas. These provisions should include piping systems that can withstand the high ignition temperatures of burning insulating oils. Where sprinkler or water spray deluge systems are used, the drainage storage is designed for these combined flow rates and volumes. If the dielectric fluid is a less flammable fluid, then the fluid may be retained in the containment area of the equipment.




If not required by code or standard, then consideration should be given to the containment of electrolyte within battery rooms or areas. Door sills or curbing may be effective techniques in containing battery electrolyte.

6.7 Fire alarm and detection systems The provision of fire alarm and detection systems may be required by the local building and fire codes based on the size, number of stories, and hazard of the new or existing substation buildings. Even when not specifically required by local codes, detection systems should still be considered for critical areas of substation buildings for the purpose of personnel safety, asset preservation, and business continuity. Systems not specifically required by local codes can be performance-based, designed to meet the intent of ANSI/NFPA 72-2010 [B28]. Control rooms, computer rooms, communication rooms, switchgear areas, and mineral-oil-insulated equipment areas represent the kinds of critical areas that should be provided with detection. Specific guidance for detection system selection by area can be found in C.5. Fire alarm systems for employee emergency notification should be provided in underground, multistory, and indoor substations. ANSI/NFPA 72-2010 [B28] should be used as the basis for design, installation, and maintenance of these systems. Consideration should be given to providing remote offsite alarm notification for facilities that are not manned continuously. Refer to A.16 for additional information.

6.8 Fire suppression The provision of automatic fire-suppression systems may be required by the local building and fire codes. Even when not specifically required by local codes, automatic suppression systems should still be considered for critical buildings and areas for the purpose of personnel safety, asset preservation, and business continuity. These systems are of particular importance for substations that do not have a responding fire department to assist in suppressing a fire. Fire-suppression systems should be present throughout all portions of underground, multistory, and indoor substations containing mineral-oil-insulated cables or mineral-oil-insulated electrical equipment above and beyond any applicable building code requirements dictating otherwise. For alternative, less flammable, fluid-filled equipment, refer to NFPA NEC article 450 in ANSI/NFPA 450-2013 [B39]) for options and requirements. Fire-suppression systems should be installed and maintained in accordance with the appropriate NFPA standard. Suppression systems can range from total flooding gaseous agents to more traditional wet pipe sprinkler systems depending on the hazards present. A fire protection engineer should be consulted to select the appropriate type of system for the buil ding, environment, and hazards under consideration. Refer to A.3 and A.17 for additional information.




6.9 Life safety

6.9.1 General In absence of or in addition to applicable local building code requirements, the following recommendations are suggested for life safety.

6.9.2 Arrangement of exits Guidance on exits can be found in NFPA 101-2011 [B34] and ANSI/NFPA 70E-2012 [B27] and applicable building, electrical, and fire codes. Substation buildings having a travel distance of more than 30 m (100 ft) to an exit should have two or more exits located at opposite ends of the building. Doors should open outward with the direction of travel and be equipped with interior panic hardware to allow egress even if locked. Exit doors shall not be padlocked, bolted, or physically impeded in any way to allow egress during a fire. Panel and equipment arrangements should be designed and installed to maintain sufficient clear widths 0.9 m (3 ft) to allow personnel to exit the equipment areas safely from either end in case of a fire. Dead ends in excess of 6.1 m (20 ft) in length should be avoided.

6.9.3 Emergency lighting Guidance on emergency lighting can be found in ANSI/NFPA 101-2011 [B34] and applicable building, electrical and fire codes. Emergency lighting should be provided for all portions of the means of egress at a minimum lighting level of 11 lux at the floor or tread level. In absence of local building code requirements that often require longer durations, the minimum duration recommended is 30 min or based on the exit time from the building, whichever is greater.

6.9.4 Exit signage Each exit door should be identified with an exit signage approved by the local authority having jurisdiction. Additional approved exit signs should be placed in the means of egress such that no portion of the means of egress is further than 30 m (100 ft) from an approved exit sign and so the entire exit path is evident.

6.9.5 Fire extinguishers Portable fire extinguishers are installed in substations based on the types of hazard(s) present in accordance with ANSI/NFPA 10-2012 [B7], where required by codes or standards or company practices (e.g., carried in vehicle versus substation installation). When portable extinguishers are used in a substation, they should always be rated for class C fires due to the presence of energized equipment (in addition to A or B rating). Fire extinguishers for the protection of Class A hazards should be sized and distributed in accordance with ANSI/NFPA 10-2012 [B7] for a hazard classification of ordinary (moderate). Example: rating of 2A:C with 23 m (75 ft) travel distances.




Fire extinguishers for the protection of Class B hazards should be sized and distributed in accordance with ANSI/NFPA 10-2012 [B7] for a hazard classification of extra (high). Example: rating of 80B:C with 15 m (50 ft) travel distances. Refer to A.18 for additional information.

6.10 Combustible materials The use of combustible materials with flame-spread, fuel-contributed, and smoke-developed ratings greater than 25 should be avoided in the selection of desks, chairs, filing cabinets, storage boxes, display boards, building insulation, interior wall panels, mounting boards, and so on. The flame spread is calculated utilizing ANSI/NFPA 255-2006 [B37]. Guidance on interior finishes can be found in Section 10.2 of ANSI/NFPA 101-2011 [B34] and applicable local building and fire codes. Care should be taken to control the accumulation of combustible materials and refuse in substation buildings. Combustible materials and refuse should be temporarily stored in metal safety refuse cans with self-closing lids or metal garbage cans with metal lids. Any accumulated combustible materials and refuse should be removed from the substation at least weekly.

7. Fire protection for substations

7.1 Spatial separation of outdoor mineral-oil-insulated equipment Electrical equipment installed outdoors and containing mineral oil should be separated from other equipment, buildings, and the adjacent property line to minimize the impact of a major fire. Spatial separation is an effective method for reducing fire spread or damage from mineral-oil-filled equipment fires. This clause provides two methods for determining acceptable minimum separation distances. Prescriptive guidelines are presented in 7.2 followed by a performance-based alternative discussed in 7.3. The prescriptive method is most commonly used, but this method may not provide adequate protection for all site conditions. The performance-based method indicates a level of protection that more accurately models the specific site conditions. When it is not practical to apply the recommended spatial separations to new or existing substations, mitigating measures such as firewalls, thermal barriers, flame-suppressing stone ground cover, automatic suppression systems, and the use of less flammable dielectric fluids can be used to reduce spatial separation values while maintaining an adequate level of protection. Refer to Clause 8 for specific guidance on these alternative protection methods.




7.2 Prescriptive separation requirements

7.2.1 Method for measuring spatial distances Spatial separation distance is measured as a straight line from the anticipated flame front to the exposure of concern. Mineral-oil-filled equipment fires are essentially pool spill fires with a three-dimensional object inside the flame. The anticipated flame front can be approximated at the containment perimeter or the anticipated spill area perimeter (where no containment or inadequate containment is provided). The anticipated spill area perimeter is determined by reviewing the possible spill scenarios and selecting a probable outcome. The example given in E.1 illustrates this. When determining the spatial separation between two nonidentical pieces of equipment (for example, different size transformers) or spill areas, two measurements are required (A B and BA) because the anticipated flame front exposure distances may differ depending on which piece of equipment is on fire and which piece of equipment is the fire target. Figure 1 illustrates the separation distance measurements. Note that transformer B does not have containment and the anticipated spill area is based on the site characteristics. There is no requirement to provide containment for small pieces of mineral-oil-insulated equipment. A criteria of 1890 L (500 gal) or less of mineral oil is often used to classify small equipment. Distances for these small pieces of mineral-oil-insulated equipment without oil containment may be measured from the nearest edge of the equipment to the nearest portion of the adjacent exposure (equipment, building, or property line) provided the site grade is sloped away from the adjacent exposure.

Figure 1 —Separation distances between substation equipment 21 Copyright © 2012 IEEE. All rights reserved.



7.2.2 Equipment to equipment Individual pieces of mineral-oil-insulated equipment should be separated from the anticipated flame fronts of one another by the distances given in Table 1. Separation distances to adjacent equipment should be measured from the edge of the postulated flame front to the nearest mineral-oil-filled component of the adjacent equipment.

Table 1 —Separation distances Mineral oil volume, L (gal) <1890 (500)

Separation distance, m (ft) Footnote a

1890 to 18 930 (500 to 5000)

7.6 (25)

>18 930 (5000)

15.2 (50)

a

Determining the type of physical separation to be used for mineral oil volumes less than 1890 L (500 gal) should be based on consideration of the following: — Type and quantity of oil in the equipment — Size of a postulated oil spill (surface area and depth) — Construction of adjacent structures — Rating and bushing type — Fire-suppression systems provided — Protection clearing time

7.2.3 Equipment to buildings Noncombustible or limited combustible buildings should be separated from adjacent mineral-oil-insulated equipment containment area(s) by a 2 h rated firewall or the separation values in Table 1. Refer to A.9 for additional information.

7.2.4 Equipment to property lines Use of the most conservative separation criteria listed in 7.2.2 is good engineering practice when determining separation criteria to the property line. This is done because the owner may not have input or control regarding what is built on the adjacent property and how far that exposure will be set back from the property line. Refer to A.19 for additional information.

7.2.5 Exceptions Multiple pieces of mineral-oil-insulated equipment used as a group on the same electrical circuit may be permitted to be any distance apart with increased risk to all units. Risk and reliability issues should be considered when taking this exception. This exception would typically be made for medium voltage (≤35 kV) equipment (e.g., single-phase oil circuit breakers or voltage regulators) with per-phase mineral oil volumes less than 1890 L (500 gal) or when the insulating fluid is listed as less flammable. Mineral-oil-insulated equipment with small oil volumes (e.g., auxiliary transformers) associated with larger, mineral-oil-insulated piece of equipment (or three-phase group) may use the smaller spacing criteria with the acknowledgment of increased risk of damage to the smaller piece of equipment.




7.2.6 Other types of adjacent equipment Where containment is provided in accordance with 8.1, other types of substation equipment should be no closer than 10.7 m (35 ft) to an adjacent piece of mineral-oil-insulated equipment’s anticipated flame front (or containment boundary). This distance is considered the minimum spatial separation distance. Where crushed stone is provided in accordance with 8.2, the minimum separation distance may be reduced to 4.6 m (15 ft). Where containment is not provided in accordance with 8.1, the minimum separation distance should be calculated in accordance with 7.3.

7.3 Calculated separation requirements As an alternative to the prescriptive values listed in 7.2, minimum separation distances may be derived from deterministic heat flux calculations. Annex B outlines the theory and various methodologies. These methods may be used when the prescriptive values are difficult to apply (e.g., the use of polymer bushings) or to gain a better understanding of the fire hazards for a design. Industry accepted methodologies are presented in various engineering guides, including the SFPE Engineering Guide for Assessing Flame Radiation to External Targets from Pool Fires [B77].

7.4 Ground surface material Special consideration should be given to ground surface material. The substation ground surface material selected can impact the fire hazard created by existing site grading. The use of hard ground surface materials or asphalt surfaces (impermeable surfaces) can allow spill fires to spread over greater distances. Crushed stone ground surfaces can help to suppress or mini mize a flaming spill fire.

7.5 Cable raceway systems

7.5.1 Cable trenches Cable trenches within 3 m (10 ft) of mineral-oil-insulated equipment containing less than 1890 L (500 gal) should have noncombustible, liquid-tight covers and be arranged to prevent liquids from entering the trench. Cable trenches within 7.6 m (25 ft) of mineral-oil-insulated equipment containing 1890 L (500 gal) or more should have noncombustible, liquid-tight covers and be arranged to prevent liquids from entering the trench. Cable trenches within 6.1 m (20 ft) of buildings should have noncombustible covers. The walls of cable trenches should be designed to prevent the entry of burning liquid through the sides of the trench walls. Typically, this is achieved by having trench walls project above and below grade and by having all joints and seams sealed liquid tight.




Cable trenches within oil-containment areas should be constructed entirely from noncombustible materials with a 3 h fire-resistance rating and all penetrations fire stopped to maintain the 3 h fire-resistance rating. Only liquid-tight covers should be used on the trench. Fire stops should be installed within the trenches to prevent the spread of a cable fire or oil fire. These fire stops can be constructed of concrete, fire stopping material, sandbags, or by filling the cable trench with sand. Fire stops should be installed adjacent to cable trench intersections, adjacent to any major pieces of oil-insulated equipment and before the entry into any substation building. The following conditions must be met: a)

Fire stops should be installed in cable trenches in order to prevent fire from spreading to other parts of the cable system.

b)

Fire stops should be installed at each junction where cables run in two or more directions.

c)

Fire stops should be installed prior to cable trench connections to any substation building.

Exception:

The requirements for liquid-tight wall construction and internal trench fire stops (intermediate fire stops within the trench) may be excluded where all of the following conditions exist: 

Cables present are limited to control cables that meet the requirements of ANSI/IEEE 383-1974 [B3].



Cable trenches are not located within the anticipated oil spill area of any mineral-oil-insulated equipment present.



Cable trenches are not entering any substation buildings.



The requirements for noncombustible, liquid-tight covers as described above are met.

Notwithstanding that this exception allows for the exclusion of internal trench fire stops, it is recommended that a fire stop be installed at each building–trench interface so that fires do not spread beyond these interfaces. This recommendation is made regardless of other safeguards that may be in place, which could lead a designer to believe this building–trench interface fire stop may not be necessary.

7.5.2 Conduits Electrical cables serving major pieces of mineral-oil-insulated electrical equipment (>1890 L or 500 gal) should be installed in conduit wherever possible. In switchyards, conduits are commonly used to enclose cables going to equipment. Polyvinyl chloride (PVC) conduit is commonly used. For mineral-oil-filled equipment, the conduit may become a path for burning oil to flow away from the equipment and out of any oil containment. The use of noncombustible materials and fire stops will minimize this problem. Conduits should be sealed with a fire-resistive seal to keep moisture, dirt, and debris out of the conduit. Refer to 6.6.4 for considerations when conduits are used in buildings.

7.5.3 Tunnels Walk-through cable tunnels (galleries) are used where there are a large number of cables. The cable trays in these areas should be separated by a distance sufficient so that a fire in one tray will not propagate to an adjacent tray. If flame-retardant cables are used, the recommended separation distances are given in IEEE Std 384-2008 [B65] and ANSI/IEEE 525-1992 [B4]. If cables are not flame retardant or the proper




separation cannot be achieved, then a fire-resistive barrier or shield can be used between the trays or a fireretardant coating may be applied to the cables. Fire hazards can also be minimized by utilizing fire stops. Consideration should also be given to the installation of 2 h fire-rated separation, a fire-detection system, a fixed extinguishing system, locating firefighting equipment at the tunnel entrances, and keeping air flows through the tunnels to a minimum. Restricting air flow in a cable tunnel will result in a reduction in the ampacity of the cables in it. This must be considered in planning the use of fire barriers.

7.6 Water supply Where a local municipal water supply is available, fire hydrants should be considered for installation such that mineral-oil-insulated equipment with capacities of 1890 L (500 gal) or more and buildings are no more than 150 m (500 ft) from a fire hydrant. In this case, the need to isolate electrically any metallic water pipes where they enter the substation should be reviewed to determine whether the transfer of the substation’s ground potential rise will be hazardous.

7.7 Fire extinguishers Unless more restrictive local requirements apply, it is recommended that fire extinguishers be made available where personnel are present performing maintenance activities. This requirement can be achieved by permanent installation of fire extinguishers throughout the yard or by requiring service personnel to bring suitable fire extinguishers with them during maintenance activities. Refer to A.18 for additional information.

8. Fire protection for equipment

8.1 Oil-spill-containment systems Substation oil-spill-containment systems have typically been installed for environmental reasons, but they also provide fire protection benefits. By minimizing the surface area of a mineral-oil spill fire, the following benefits arise: 

Reduced overall size of the spill fire



Contained fire from spreading within the substation



Reduced flame height



Reduced radiant heat flux to noninvolved exposures



Reduced clean up and restoration area following the event

If oil-spill containment is not required for environmental reasons, then the substation designer should consider the oil-spill containment for fire protection. An oil-spill-containment system should be designed in accordance with IEEE Std 980. 6 In addition to containing the oil volume, the containment volume should allow for precipitation (typically 24 h of the

6

Information on references can be found in Clause 2.




25-year storm density), automatic fire-suppression systems (refer to ANSI/NFPA 15-2012 [B16] for guidance), and manual firefighting activities, as applicable. Oil-containment systems should be designed to survive exposure to a minimum 3 h fire occurring within the bounds of the containment system. This minimum fire-resistance time may be reduced to a 2 h exposure with the installation of automatic suppression systems. The perimeter of the spill containment should generally be located between 2 m and 3 m (6.6 ft and 9.8 ft) beyond the portions of the electrical equipment containing oil, based on the height of typical bushings and conservators. Stone is frequently used in oil-containment pits. Refer to 8.2 for recommendations.

8.2 Stone flame suppression It is common practice for substation designers to use stone for ground surface material in switchyards and to provide stone in the containment pits of oil-insulated equipment. Testing has shown that a 150 mm (6 in) depth of 18 mm (0.75 in) diameter stone can suppress the flaming combustion of mineral oil by lowering the flame temperature and controlling the combustion air. When the level of the mineral oil rises to within 40 mm (1.5 in) of the top of the stone surface, flaming combustion will occur. See Zalosh and Lin [B81] for further details. It is recommended that the stone used for ground surface material or in containment pits should be between 18 mm and 38 mm (0.75 in and 1.5 in) in diameter. Containment pits should be designed with a minimum stone depth of 450 mm (18 in) so the liquid volume will not rise to within 50 mm (2 in) of the top surface of the stone. Stone used for station surfacing will typically have a depth of 150 mm (6 in). The void space for a layer of 18 mm (0.75 in) diameter stone is approximately 30% to 40% (the actual void space for the stone being used in containment pits should be determined for design purposes). Therefore, the overall volume of the oil containment will have to be significantly larger when flame-suppressing stone is used to fill the entire volume of a containment pit. An alternative is to put a layer of stone on a grating system in the containment pit. Refer to IEC 61936-1-2011 [B60] for further details. The following considerations should be made when using stone: 

Stone used as ground surfacing material with depths of more than 150 mm (6 in) may be difficult to drive over.



The stone should be durable so it does not fracture under the expected loads.



The void ratio for stone used in containment pits should be considered in determining the liquid (includes oil, rain water, melting snow, etc.) containment volume.



Crushing the stone so it has at least two faces will allow the stone to interlock and provide a better surface for walking and driving. This reduces the void ratio and is taken into account when determining the storage volume.



Washing stone before it is installed will reduce fines and organic material normally present in new material from being deposited at the bottom of the layer and thus improve its effectiveness and increase the period until the first maintenance.



Areas with snow accumulation may encounter spring melting conditions where snow melts in daytime and freezes when it cools off at night. This may cause ice to form around the rock, which would make the stone ineffective for fire-suppression or fire protection purposes.






Stone should be maintained on a regular basis to remove foreign debris such as sand, dirt, and weeds that accumulate between the stones and reduce its effectiveness.

8.3 Fire barriers Guidance on the design and installation of fire barriers for mineral-oil-insulated equipment can be found in NFPA 850 and NFPA 851. Fire barriers should be of suitable construction to maintain effectiveness throughout the duration of the expected exposure fire. Fire barriers should be designed to withstand wind loads, seismic loads, and blast pressures, as applicable. Fire barriers may be installed as a means of passive separation protection when the minimum spatial separation distances defined in 7.2 are not achieved. Refer to A.20 for additional information.

8.3.1 Height The minimum barrier height should be based on site-specific calculations. In lieu of these calculations, consider a barrier height between 0.3 m (1 ft) and 1 m (3.3 ft) above the highest mineral-oil-insulated portion(s) of the adjacent equipment. Where separating mineral-oil-insulated equipment from non–mineral-oil-insulated equipment or buildings, the height of the barrier should not be less than that required to break all sight lines between the highest mineral-oil-insulated component(s) and all portions of the non–mineral-oil-insulated equipment or buildings within the minimum spatial separation distance(s) defined in 7.2.

8.3.2 Width The barrier should extend to the outermost boundary of the oil-containment area(s) serving the mineral-oilinsulated equipment or the boundary of the postulated pool fire. Where separating mineral-oil-insulated equipment from non–mineral-oil-insulated equipment or buildings, the width of the barrier should not be less than that required to break all sight lines between the outermost edge of the oil-containment area serving the adjacent mineral-oil-insulated equipment and all portions of the non–mineral-oil-insulated equipment or buildings within the minimum spatial separation distance(s) defined in 7.2.

8.4 Fire-suppression systems Active, automatic fire-suppression systems should be considered in lieu of fire barriers when the minimum spatial separation distances defined in 7.2 are not achieved. These types of systems may also be installed in addition to fire barriers or indoor equipment vaults for additional fire control. In areas with gaseous fire extinguishing systems, smoke ventilation systems should be properly interlocked for the effective operation of the extinguishing system.




8.4.1 Indoor equipment vaults A minimum 3 h fire-resistance-rated vault should encompass all individual energized pieces of indoor mineral-oil-insulated equipment containing 1890 L (500 gal) or more of mineral oil. The minimum fire-resistance rating may be reduced to 2 h where automatic suppression is installed in accordance with 8.4.

8.4.2 Alternative dielectric insulating medium Alternative types of dielectric insulating liquids have been developed with higher flash and fire points to minimize the likelihood and impact of fires. These are generally referred to as “less flammable” fluids as defined by the National Electrical Code® (NEC®) (NFPA 70) [B75]. Such alternative dielectric insulating fluids should always be considered where feasible, but they are particularly useful for minimizing fire impact on indoor equipment applications and equipment arrangements where the minimum spatial separation distances in 7.2 cannot be achieved. Refer to A.21 for additional information.

8.5 Explosion suppression Explosion suppression systems for power transformers are not widely deployed. Some methodologies may minimize transformer explosion impacts as indicated in 8.5.1 through 8.5.3.

8.5.1 Distribution class transformers For distribution class auxiliary transformers inside substations, tank rupture prevention/protection systems may be used as per UL and FM listings requirements per Article 450-23 of NFPA 70 [B75]. An example is FM Global’s FM Approved Transformers Standard 3990, which incorporates current limiting fusing and equivalent means to limit the potential fault energy to an acceptable level.

8.5.2 Power class transformers Explosion suppression systems have been developed, tested, and installed in high-risk transformer applications. At this time, the industry has not accumulated enough experience to validate the effectiveness of any of the designs. System manufacturers can provide both test data and user testimony. Substation designers considering such an application should work closely with the transformer manufacturer and the explosion suppression system manufacturer to determine the most appropriate design. New designs using multiple containment structures and more pressure-resistant tank construction are being developed by some manufacturers.

8.5.3 Alternative dielectric insulation medium The use of high-fire-point fluids or nonflammable gases, such as SF6, as a dielectric medium in distribution and power class transformers can significantly reduce the impact of a catastrophic failure inside a transformer tank. Substation designers considering such an application should work closely with the transformer manufacturer to determine the most appropriate design.




8.6 Equipment design Below are a few suggestions to minimize the spread of fire from oil-filled equipment: 

Avoid the use of low melting temperature valves and other fittings, especially at the lower surfaces of transformer walls (an external fire will melt these valves and feed the t he fire)



Implement a scheme on transformers to stop the fans and pumps when there is a transformer trip (prevent pumping oil or blowing air onto a fire or ruptured transformer that is on fire or spilling oil [even if contained])

9. Fire protection measures selection

9.1 General A fire risk evaluation should be initiated as early in the design process as practical so that the fire prevention and fire protection recommendations as described in this document have been evaluated in view of the substation-specific considerations regarding design, layout, and anticipated operating requirements. The evaluation should result in a list of recommended fire prevention features to be provided based on acceptable means for separation or control of common and special hazards, decrease the probability of ignition, and the suppression of fires. The fire risk evaluation should be approved by the owner prior to final drawings and installation. Many factors are used in the selection of the most appropriate type of fire protection for substation hazards. There is no one best solution for each of the individual hazards that substations have, but there are a number of alternatives that can be used based on the needs of the owner, insurance company, and regulator. The following are a number of commonly used methods for selecting fire protection measures.

9.2 Fire protection objectives Individual fire protection solutions can provide different damage levels for specific applications. The owner needs to determine the acceptable level of fire loss to help determine the level of fire protection to use. A typical example of this method involves the fire protection for substation control buildings; some owners have an objective of suppressing a fire at a cabinet components stage and thereby install gaseous fire protection systems to extinguish those fires very rapidly. Other owners may be willing to accept damage from a fire that would be limited to the loss of one or two cabinets and will therefore install a preaction sprinkler system in the substation control facility.

9.3 Performance factors Important criteria in the selection of the most appropriate fire protection for a substation are called performance factors. The three typical criteria are as follows: 

Reliability: The system will operate correctly when it is required to do so.



Availability: The system will have a low down time for maintenance or as a result of failures.



Effectiveness: The system will suppress the fire before critical conditions can occur.




The various fire protection systems available provide differing levels for these criteria.

9.4 Life cycle factors Fire protection systems have varying life expectancies. Sprinkler systems can continue to provide successful performance for several decades, but software-based addressable detection systems become obsolete much sooner (typically 1 to 15 years).

9.5 Risk-based economic analysis The economic risk-based analysis is the evaluation of the investment measures in relation to the probability of fire, the potential losses due to fire, and the cost of the fire protection measures. This analysis requires a reasonable database of the probability of fires for the different hazard areas or types, an assessment of the performance success of the proposed fire protection measures, an estimate of the fire loss costs, and engineering judgment. The potential losses usually include the equipment loss as well as an assessment of the lost revenue due to the outage resulting from the loss of equipment. Refer to A.22 for additional information.

9.6 Benefit/cost analysis One of the most common risk-based economic analysis is a benefit/cost analysis. This analysis is calculated using Equation (1):

B / C =

benefit cost

=

p ( F ) × e( RM ) × [ RC + LR + SB + OC ] RM

(1)

where benefit cost e(RM) LR OC

p( F ) RC RM SB

is the value associated with lost revenue, operation, and building replacements that are avoided if a major fire is prevented (benefit of avoided loss) is the cost to protect against damage due to major fire is the effectiveness of remedial measure is the lost revenue (in $) due to fire (lost load × mill rate) is the operating cost associated with manning the station due to fire damage of supervisory equipment or additional testing and switching costs associated with restoring service is the probability of major fire (probability of an outage due to a fire) is the replacement cost of facility and equipment lost due to fire is the cost of remedial measure is the societal benefit (in $) lost due to customer outages created by fire

Once the potential financial loss due to a fire has been calculated, the designer should input costs and effectiveness of any proposed fire protection measure into the benefit/cost equation and determine the B/C ratio. If the B/C ratio is less than 1, then the provision of the fire protection measure is not an acceptable investment. Normally, the B/C ratio should be greater than 1 and preferably greater than 2. A B/C ratio of 2 means that the avoided fire loss cost or benefit is twice that of the cost of the fire protection measure. Therefore it is a good investment. 30 Copyright © 2012 IEEE. All rights reserved.



Any fire insurance coverage can also be included in this type of calculation. The insurance premiums can be included as a fire protection cost, and an insurance payout will reduce the fire costs. It should be noted that insurers will generally reduce the insurance costs for specific types of fire protection installed. Companies should review the possible premium savings with their insurers and factor any savings into the calculation. Refer to C.6 for additional information and an example calculation.




Annex A (normative) Additional information to main body clauses

A.1 Purpose This clause provides additional information to 1.2. Fire protection measures reduce the fire risks to the public in the vicinity of the substation and to emergency response personnel. These measures can also decrease the risk to operating personnel. Fire protection should be integral to the planning, design, and operation of substations. In many instances, fire protection is not considered. Too often, fire protection decisions are made after the planning and design of the substation, which can lead to costly changes late in the project. Although common cause events are considered, substation fires generally have not been considered in assessing the reliability of the electric system. However, substation fire events have occurred, with significant challenges to system reliability. Careful consideration of the consequences of a substation fire, and alleviating those consequences throughout the planning and design process, will help to mitigate the consequences of a fire in a substation. Properly designed substation fire protection can minimize the effect of component failure during a fire on overall reliability of the system supply. Having fire protection systems and processes will minimize the asset and revenue losses from any fire.

A.2 Fire hazards This clause provides additional information to Clause 4. Identifying fire hazards can be a complex process. The fire hazard analysis process should be used for planned, new, or existing substations to determine the appropriate level of fire protection necessary to mitigate the consequence of fire. The fire hazard analysis process should be done by a team consisting of substation designers, fire protection specialists, and substation operating staff so that all perspectives are included in the process. The probability of fire and potential magnitude of its consequences should be quantified to help justify the need for fire protection. For further information regarding the process for evaluating industrial fire hazards, refer to Chapter 2, “Industrial Fire Hazard Assessment,” of the ANSI/NFPA Industrial Fire Hazards Handbook , 3rd ed. [B46]. Historical information on substation fires can help with fire hazard analysis. There have been a wide range of types and causes of fires experienced in substations. The types of fires are based on the equipment and systems used in the substations. Fires involving dc valves, outdoor or indoor mineral-oil-insulated equipment, mineral-oil-insulated cable, hydrogen-cooled synchronous condensers, or equipment with fluids containing polychlorinated biphenyls (PCBs) are usually well documented. Therefore, these types of equipment are easily recognized as a fire hazard. There are a number of other substation fire types that are not as well documented. Factory Mutual Data Sheets 5-4 [B57], 5-19 [B58], and 5-31 [B59]; NFPA 851; and CIGRE TF 14.01.04-1999 [B54] provide guidance on these types of fires. Clause D.6 covers a study done by a major utility of reported substation fires listed by types. 32 Copyright © 2012 IEEE. All rights reserved.



A.3 Fire protection considerations for substation sites This clause provides additional information to Clause 5 and 6.8. A fire risk evaluation should be initiated as early in the design process as practical so that, in addition to other applicable codes and/or regulations, the fire prevention and fire protection recommendations of this document may be evaluated in view of the specific considerations regarding design, layout, and anticipated operating requirements. The evaluation should result in a list of recommended fire prevention features to be provided based on acceptable means for separation or control of common and special hazards, the control or elimination of ignition sources, and the suppression of fires. Fire Safety Decision Trees is a methodology commonly used to determine the most appropriate strategy for fire protection. It can also be applied to the various hazards that are found in electrical substations. Refer to NFPA 550-2012 [B40] for details on how to use this methodology.

A.4 Forested or grassland areas This clause provides additional information to 5.2.1. A fall hazard should be carried out on trees and other vertical vegetation around a substation. Fallen trees should be a minimum of 9 m (30 ft) away from all critical substation assets. NFPA 1144-2013 [B44] provides a method for evaluating this type of hazard under specific site conditions.

A.5 Prevailing winds This clause provides additional information to 5.4. Prevailing wind direction data are available from many national weather organizations, local weather stations, national forest organizations, and airports. The Society of Fire Protection Engineers publishes several documents that present methodologies for calculating the impact of wind-tilted fire plumes. Both the SFPE Handbook [B79] and the SFPE Engineering Guide for Assessing Flame Radiation to External Targets from Pool Fires [B77] provide examples of methodologies.

A.6 Fire emergency response capability This clause provides additional information to 5.5. When designing a new substation or changing an existing substation, the substation designer should review the capabilities of the fire service in the area of the station. If no public fire service or fire brigade is available to fight a fire in the station, then the substation designer should not rely on any manual means of fire protection but incorporate other specific safeguards. The designer could look at incorporating specific design measures into the substation design. If the local fire brigade or fire department can provide manual fire protection services to the substation, then the designer should work with these groups to determine their specific capabilities. The ranges of fire department or fire brigade capabilities can vary considerably. Large, well-organized fire departments in major cities can provide significant resources in terms of equipment and work force in a short time to deal with a major fire. Rural volunteer fire departments on the




other hand may not have the same level of equipment and personnel to deal with large-scale fires. Discussions with the fire departments should be held to determine the following: 

The maximum number of personnel the fire department has available



The type of equipment available such as pumper trucks, tanker trucks, aerial ladder trucks, foam supplies, and other special equipment



The number and type of equipment and personnel that would be dispatched to a fire at the substation



The expected response time

The designer could then review probable types of fires (design fires) that would be expected at the substation and work with the emergency services to determine whether they have sufficient resources to deal with a specific incident. If the local fire department does not have sufficient resources to deal with the design fires at the station, then the designer should work with the local fire department and determine whether there are adjacent fire departments or fire resources that could be used during an incident. Several high-profile substation fires have been successfully suppressed using crash rescue firefighting vehicles from adjacent airports. If such resources are not available, then consideration should be given to including increased substation fire protection features or the possible purchase of required resources for the local fire department. If the substation designer finds that the local fire emergency resources and water supply are inadequate for manual firefighting, then passive or active automatic fire protection measures should be considered as part of the overall substation fire protection scheme. Some examples of passive measures that could be used in the substation design are providing adequate spacing between oil-filled equipment, provision of firewalls between closely spaced equipment, the use of noncombustible construction for the control building, and the provision of stone-filled pits or other oi l containment means around all oil-filled equipment. Possible active automatic fire protection measures include water spray, sprinkler, and inert gas systems. Fire department personnel responding to substation fires can be exposed to significant fire and electrical safety hazards that they may not be trained to deal with. The types of fire hazards found in indoor and outdoor substations are significantly different from the typical hazards to which public firefighters are normally exposed. As such, they may be putting their own safety at risk. The most significant hazards that fire department personnel are exposed to are the electrical safety hazards of the substation. Fire department personnel are trained to take an active role and aggressively suppress fires. In the case of a fire in an electrical substation, there may be long delays until substation operating personnel can arrive onsite and make the station electrically safe. In some cases, it may take up to an hour for operating personnel to arrive onsite to make the station electrically safe. Therefore, the fire department personnel want to enter the facility and suppress the fire, before it is safe to do so. Delays of this type create additional pressures on the responding fire departments because they are concerned that while they are waiting to gain access to the substation fire, they cannot respond to other alarms received. These tensions can create situations where responding personnel take serious risks of electrical contacts and exposures. The type of equipment and facilities found in the substation are foreign to most of the operating environments to which the fire department personnel are exposed. Therefore, the installation of fire protection in a substation will help control or suppress fires and allow the fire department to access the facility safely.

A.7 Available firefighting water supplies This clause provides additional information to 5.6. 34 Copyright © 2012 IEEE. All rights reserved.



In the event of a fire in the station buildings or mineral-oil-insulated equipment, water is the most commonly used fire extinguishing agent both directly and as part of fire extinguishing agent mixtures such as foam. As part of the design process, the available firefighting water supplies should be reviewed for any station that has a responding fire department or fire brigade. If there is no responding fire department or fire brigade, then the designer may incorporate passive measures (i.e., greater spacing of mineral-oil-insulated electrical equipment) into the station’s design. The designer should also determine the requirement for firefighting water supplies, based on governing codes, regulations, and bylaws. The following are some of the common standards for firefighting water supplies: a)

b)

Piped municipal supplies 1)

Fire Underwriter Survey Water Supply requirements guide

2)

Insurance Advisory Organization

3)

American Water Works Association

Rural water supplies 1)

ANSI/NFPA 1142-2012 [B43]

2)

Various NFPA fire protection application standards such as ANSI/NFPA 13-2011 [B14], ANSI/NFPA 14-2010 [B15], ANSI/NFPA 15-2012 [B16], and ANSI/NFPA 24-2013 [B21]

During the water supply review, the substation designer should look at all possible sources of water adjacent to the station such as lakes, streams and rivers, swamps, and so on. The designer should also be cognizant of the relatively large quantity of water required for multiple hours of firefighting during major substation fires, such as fully involved mineral-oil-insulated transformer fires. If there is an insufficient water supply available for manual firefighting, then the designer should work with the local fire department to determine whether they have adequate tanker capabilities to bring water to the substation during the fire. Where a local municipal water supply is not available, responding fire department personnel should be consulted on their needs for fighting all probable fire scenarios. Water tanker trucks, onsite water storage tanks, ponds, lakes, and streams are all possible sources of firefighting water. Passive fire protection measures such as containment, spatial separation, and/or fire barriers are of particular importance where sufficient firefighting water may not be available. Hydrant systems intended for use by fire department personnel should have suitable grounding clamps and cables available within the station to ground any firefighting vehicles operating within the station. If the substation designer finds that the local fire emergency resources and water supply are inadequate for manual firefighting, then passive or active automatic fire protection should be considered. Some examples of passive measures that could be used in the substation design are providing adequate spacing between oilfilled equipment, provision of firewalls between closely spaced equipment, the use of noncombustible construction for the control building, and the provision of stone ground cover adjacent to all oil-filled equipment.

A.8 Emergency access to the substation This clause provides additional information to 5.7.




When the substation designer is laying out the station or changing an existing station, he or she may consider emergency vehicle access to all major buildings or major banks of oil-insulated equipment. In most cases, the normal operating access for bucket trucks and crane trucks will be quite similar to that required by the emergency services. Normally, fire department vehicles do not need to get within 150 m (500 ft) of major risk areas. If the distances are greater than 150 m (500 ft), then consideration should be made to ensuring adequate access is available. When laying out the overall site plan, the designer should make provisions for emergency access at a minimum of two locations around the switchyard. Typically, the emergency services vehicles require access roads with a minimum width of 6.1 m (20 ft), centerline minimum turning radius of 12 m (40 ft), overhead clearances of 5 m, and roadbeds that will support the expected load imposed by firefighting vehicles in the various seasonal conditions. The access points to the station should have a minimum width of 6.1 m (20 ft). These access points should not be located should beneath overhead power lines or adjacent to critical fire hazards that could cause them to be blocked during an incident. The access points should also be remotely located such that the minimum distance between them is no less than 1/2 the overall diagonal distance of the switchyard. If the access roads throughout the station yard are dead-ended, then provision should be made for a suitable turnaround facility.

A.9 Substation buildings This clause provides additional information to 6.2 through 6.5 and 7.2.3. The types of fires created by mineral-oil-insulated equipment or cable can create catastrophic risks to indoor substations. The application of these types of equipment should be analyzed using fire performance based methods because guidelines may not recommend suitable levels of fire protection for indoor substations. A performance-based method will be able to model more accurately the fire conditions and the impacts to the building occupants, the structure, and other equipment. The fire conditions can be reviewed based on some of the following types of criteria: 



The blast pressure created by an explosion and the ability of the building to withstand the blast pressures The heat release rate and flame height of the fire



The activation time for fire detection devices and fire protection systems and the ability of fire protection systems (i.e., sprinklers or water spray systems) to suppress the fire



The available safe egress time for building occupants (including detection time, egress time, and smoke exposure time)



Volume of smoke being released during the fire



The temperature exposure conditions of building structural elements and predicted failure time



Time to allow the fire to burn out



Fire conditions that the fire department will be exposed to



Smoke and fire damage to other areas and equipment of the substation




The various performance fire modeling (zone or computational fluid dynamics) techniques provide varying degrees of fire details and simulation results. For an indoor mineral-oil-insulated transformer, target criteria can be as simple as preventing a fire from taking out of service a second transformer, or it can be as complex as radiant heat flux to the building structure or carbon monoxide exposures to building occupants. The following are some of the recognized performance-based fire safety and protection documents that can be used for a performance-based analysis: 

SFPE Engineering Guide to Performance-Based Fire Protection [B78]



SFPE Handbook of Fire Protection Engineering [B79]



British Standards Institute, Fire Safety Engineering in buildings (Part 1 Guide to the application of fire safety engineering principles) [B51]



Australian Building Codes Board, Fire Safety Engineering Guidelines [B49]



The Canadian National Building Code (objective-based) [B73]



AICHE Guidelines for Chemical Process Quantitative Risk Analysis [B2]



EPRI TR-100443-1992 [B56]



U.S. Nuclear Regulatory Commission (NUREG) documents

A.10 Construction This clause provides additional information to 6.6. See NFPA 850 for further discussion on construction requirements. When exploring the additional information available in NFPA 850, keep in mind that the information and requirements presented may be overly conservative for direct application to substations because they are developed for generation facilities, which involve different hazards and threats.

A.11 Fire separation This clause provides additional information to 6.6.2. Fire separations are a form of compartmentalization to limit fire spread by isolating a room or space containing a fire hazard. The fire separation compartment will be formed by fire-rated assemblies of the floor, walls, and ceiling of the room. In the absence of applicable building code requirements, the following are suggested fire-resistance ratings for separating substation areas from one another: 

Control rooms, 2 h



Battery rooms, 2 h



Switchgear rooms, 2 h



Cable spreading rooms or tunnels, 2 h



Telecommunications rooms, 2 h



Shops,2 h



Offices, 2 h



Warehouse areas, 2 h



Emergency diesel generator, 2 h






Flammable and combustible storage, 2 h



Transformer vaults, 3 h 7



Indoor oil circuit breaker vaults, 3 h (see footnote 7)

A.12 Floor and roof This clause provides additional information to 6.6.3. ANSI/NFPA 256-2003 [B38] outlines a method to measure the relative fire characteristics of roof coverings. Class A (ANSI/NFPA 256-2003 [B38]) rated roof coverings are effective against severe test exposure, which give a high degree of fire protection to the roof deck, which do not slip from position, and which do not present a flying brand hazard.

A.13 Building openings This clause provides additional information to 6.6.6. Most building codes permit opening protective systems (rated doors, windows, and shutter assemblies) to have a slightly reduced rating due to the fact that combustible loading is typically substantially less in front of openings when they are used as functional attributes of a compartment (windows for viewing or doors for access to the space). This practice is supported in this guide by allowing the reduction from a 2 h rating down to a 1.5 h rating requirement for doors and similar opening protective systems. Where nonoperable windows are installed as opening protective systems in rated separation walls, many times wired glass, ceramic glazing, or specialized water spray systems can be used in lieu of fire shutters.

A.14 Heating, ventilating, and air conditioning (HVAC) This clause provides additional information to 6.6.10. The following is a list of areas where alternative designs should be considered: 

The HVAC systems for control rooms, computer rooms, and communication rooms would ideally be designed to provide a positive pressure for these rooms and to operate with full exhaust/relief air and no return air, during a fire. These systems should not service other areas. The objective is to help prevent smoke from a fire outside these rooms entering the rooms and exhausting any smoke from a fire within the rooms. If these rooms are protected by a total flooding gaseous system, then the HVAC system should be shut down so the suppression systems can operate correctly.



Any HVAC system for areas having mineral-oil-insulated equipment, SF6, or high concentrations of cable with combustible insulation jackets should be designed to operate in a full exhaust mode in the event of a fire. These systems should not service other areas.

7

An analysis with input from a fire protection engineer, substation designer, and building official(s) should be performed to determine the appropriate level of fire separation on indoor transformer and mineral-oil-insulated circuit breaker vaults. This analysis should take into consideration the type of substation building involved (underground, multistory, or located in a high-rise building), fire-resistance rating of the overall structure, calculated blast pressure of the room boundaries and structure, blast venting, type of transformer or circuit breaker used, electrical failure characteristics (arc tension, short-circuit current, and arc duration time), active fire protection systems present, company response time, and fire department response adequacy.




A.15 Smoke and heat management This clause provides additional information to 6.6.11. Special consideration should be given to control and relay rooms that are located below grade or within a multistory building, indoor transformer vaults, and other indoor areas that house large mineral-oil-insulated equipment. Two important concerns are the protection of personnel and critical station equipment from corrosive and toxic combustion products. Indoor fires can endanger occupants and assets far removed from the actual fire event due to the spread of combustion products throughout the building. Common concerns include the massive quantities of smoke that may be produced, toxic breakdown products from SF6-insulated electrical equipment (SF4 sulfur tetrafluoride gas, S 2F2 sulfur monofluoride gas, HF hydrofluoric acid, H2SO4 sulfuric acid, and metallic fluoride dust), and the corrosive combustion products released from halogen-bearing compounds (e.g., PVC and polyethylene cable jackets). Consideration should be given to smoke venting from any areas that contain items capable of producing toxic or corrosive smoke. Areas that could be impacted by corrosive smoke, such as control, relay, and communication rooms, can be provided with a positive pressure ventilation system to prevent the migration of smoke into those sensitive areas. ANSI/NFPA 92A-2009 [B33] provides detailed design guidance on smoke control systems.

A.16 Fire alarm and detection systems

A.16.1 General This clause provides additional information to 6.7. The following guidance is provided for the selection of industry-recognized detection strategies for specific substation hazard areas. Generally, the following should be applied to substation buildings that meet one of the following criteria: 

A fire alarm and detection system is required by local codes.



The building area is greater than 1000 m2 (10 000 ft2).



The building is multistory.



The building contains oil-insulated equipment.

These recommendations are not intended to preclude the use of other detection methodologies determined to be appropriate for the hazard.

A.16.2 Detection Automatic detection should be designed in accordance with Section 5.7 of ANSI/NFPA 72-2010 [B28], “smoke-sensing fire detectors.” Where building and equipment configurations do not allow for the prescriptive application of requirements, particularly in existing substation buildings, performance-based designs are recommended in accordance with Section 5. 3 of ANSI/NFPA 72-2010 [B28]. The following are suggested applications for detection in specific substation buildings areas: a)

Control, relay, and telecommunication areas 1)

Spot-type photoelectric detection at the ceiling and below the subfloor areas 39 Copyright © 2012 IEEE. All rights reserved.



2)

Very early air sampling detection NOTE—Unless rap id response is available from substat ion and emergency responders, there is little benefit to this option.8

b)

c)

d)

Feeder sections and switchgear areas 1)

Spot-type photoelectric detection

2)

Linear beam smoke detection

Cable spreading rooms and cable tunnels 1)

Spot-type photoelectric detection where environmental conditions permit

2)

Linear heat detection where humidity, temperature conditions, and other environmental conditions are outside the photoelectric smoke detectors listed range

General substation building areas including shops, office, and warehouse areas 1)

e)


Transformer vaults and mineral-oil-insulated equipment areas 1)


2)

Rate-compensated thermal detectors, linear heat detection, or wet/dry pilot detection for deluge system operation

A.16.3 Fire alarm/employee notification systems Audible notification should be installed throughout all potentially occupied areas of underground, high-rise, and indoor substation buildings in accordance with Section 7.4.3 of ANSI/NFPA 72-2010 [B28]. Public mode visible notification should be provided throughout all areas with an average ambient sound level of 105 dB or more. Manual pull stations should be installed at each exit along with a single, visible notification device. The minimum intensity rating should be 15 candela.

A.16.4 Monitoring Fire alarm and detection systems should be monitored for alarm, supervisory, and trouble signals to a constantly attended location.

A.17 Fire suppression This clause provides additional information to 6.8. The following guidance is provided for the selection of industry-recognized suppression strategies for specific substation hazard areas. NOTE—These recommendations are not intended to preclude the utilization of other detection methodologies determined to be appropriate for the hazard.

8

Notes in text, tables, and figures of a standard are given for information only and do not contain requirements needed to implement this standard.




A.17.1 Cable spreading areas Sprinkler systems should be installed throughout all cable-spreading areas. Design and installation of such systems should be in accordance with NFPA 13 [B14]. Selection of design density should be based on the type and density of cables present. See Section C-4 of NFPA 850, “Grouped Cable Fire Tests,” for additional discussion on appropriate design densities. Automatic sprinkler systems should be the wet pipe, closed-head type unless extenuating circumstances prohibit this type (i.e., use dry pipe system in unheated areas subject to freezing). Exception to wet pipe recommendation:

Preaction systems may be considered where extenuating circumstances dictate the need and the water delivery delay time (and associated fire growth and damage level) is deemed acceptable. Circumstances may include situations where equipment is present that does not react well to exposure to water and additional levels of protection against inadvertent water discharge are deemed necessary.

A.17.2 Control, relay, and switchgear rooms/buildings Suppression systems are generally not provided in control and relay rooms where all of the following are met: a)

A fire department with adequate personnel and equipment is available for emergency response in a timely fashion.

b)

An automatic detection system is arranged to dispatch automatically the fire department upon receipt of any alarm signal.

c)

Equipment present is limited to enclosed metal clad switchgear cubicles, relay and communication panels, battery systems, miscellaneous electric panels, and associated conduit and wiring. This type of equipment consists of minimal combustible material and is unlikely to contribute to a deenergized fire scenario.

d)

Mineral-oil-insulated equipment is not present.

e)

Area is separated from other areas of the building by minimum 2 h fire-resistance-rated construction.

Where the provisions of this clause are not all met, a double-interlock preaction sprinkler system should be installed throughout the control and relay room(s). Exception to preaction sprinkler recommendation:

Total flooding gaseous agent systems (e.g., clean agent) should be considered where extenuating circumstances preclude the use of water (i.e., adjacent equipment areas with sensitive equipment in drainage path and draining water poses an unacceptable threat to equipment). Such systems should be designed in accordance with the appropriate NFPA standard and manufacturer design guidance.

A.17.3 Gas-insulated switchgear (GIS) areas Sprinkler systems are not installed throughout all GIS areas except where there is mineral oil cable, mineral oil potheads, or any other high fire hazards. Automatic sprinkler systems should be the wet pipe, closed-head type unless extenuating circumstances prohibit this type (i.e., use dry pipe systems in unheated areas subject to freezing). 41 Copyright © 2012 IEEE. All rights reserved.



Exception to wet pipe sprinkler recommendation:

Preaction sprinkler systems may be considered where extenuating circumstances dictate the need and the water delivery delay time (and associated fire growth and damage level) is deemed acceptable. Circumstances may include situations where equipment is present that does not react well to exposure to water and additional levels of protection against inadvertent water discharge are deemed necessary.

A.17.4 Oil pump houses Sprinkler systems should be installed throughout oil pump houses. Design and installation of such systems shall be in accordance with ANSI/NFPA 13-2011 [B14]. Automatic sprinkler systems should be the wet pipe, closed-head type unless extenuating circumstances prohibit this type (i.e., use dry pipe systems in unheated areas subject to freezing). Exceptions to wet pipe sprinkler system recommendation:

Preaction sprinkler systems may be considered where extenuating circumstances dictate the need and the water delivery delay time (and associated fire growth and damage level) is deemed acceptable. Circumstances may include situations where equipment is present that does not react well to exposure to water and additional levels of protection against inadvertent water discharge are deemed necessary. Total flooding gaseous agent systems (i.e., CO2 or clean agent) may be considered where extenuating circumstances preclude the use of water (i.e., adjacent equipment areas with sensitive equipment in drainage path and draining water poses an unacceptable threat to equipment). Such systems should be designed in accordance with the appropriate NFPA standard and manufacturer design guidance.

A.17.5 Indoor mineral-oil-insulated equipment vaults The required suppression system applications for various mineral oil volumes within rated enclosure vaults are listed in Table A.1. Where multiple system choices are listed, any single choice is acceptable.

Table A.1—Suppression systems for vaults Total oil quantity 0 L to 375 L (0 gal to 99 gal)

a

376 L to 1889 L (100 gal to 499 gal)

1890 L (500+ gal)

Required type of suppression system Overhead sprinkler (wet pipe, closed head)

Design standard

ANSI/NFPA 13-2011 [B14]

Overhead sprinkler (wet pipe, closed head)

ANSI/NFPA 13-2011 [B14]

Total flooding Gaseous system

ANSI/NFPA 12-2011 [B11] or ANSI/NFPA 2001-2012 [B45]

Fixed water spray

ANSI/NFPA 15-2012 [B16]

Total flooding Gaseous system

ANSI/NFPA 12-2011 [B11] or ANSI/NFPA 2001-2012 [B45]

a

Less than 1890 L (500 gal) of mineral oil is present; the designer may have a qualified fire protection engineer conduct a benefit/cost analysis to determine the added benefit of installing suppression in the vault. This analysis may demonstrate that sufficient benefit is not gained to warrant the cost of the suppression system. See C.6 for additional discussion on benefit/cost analysis.




A.17.6 Miscellaneous indoor substation areas Suppression systems should not be installed throughout miscellaneous indoor substation areas where all of the following are met: 

A fire department with adequate personnel and equipment is available for emergency response in a timely fashion.



An automatic detection system is arranged to dispatch the fire department automatically on receipt of any alarm signal.



Equipment present is limited to enclosed metal clad switchgear cubicles, relay and communication panels, battery systems, miscellaneous electric panels, and associated conduit and wiring. This type of equipment consists of minimal combustible material and is unlikely to contribute to a deenergized fire scenario.



Mineral-oil-insulated equipment is not present.



Area is separated from other areas of the building by minimum 2 h fire-resistance-rated construction.

Where the provisions of this clause are not all met, a sprinkler system or total flooding gaseous agent suppression system should be installed. Design and installation of sprinkler systems should be in accordance with ANSI/NFPA 13-2011 [B14]. Design density and classification should increase where conditions warrant a more severe classification. Design and installation of total flooding gaseous agent systems should be in accordance with the appropriate NFPA standard (i.e., ANSI/NFPA 12-2011 [B11] and ANSI/NFPA 2001-2012 [B45]).

A.18 Fire extinguishers This clause provides additional information to 6.9.5. Unless rigorous fire extinguisher training is provided on an ongoing basis, it is recommended that Class B hazards be considered of nonappreciable depth when determining size and distribution requirements in ANSI/NFPA 10-2012 [B7] because the extinguishers will be intended only for use on small, incipient fires as opposed to larger oil spill fires, which may be of an appreciable depth. Ongoing minimal training should be established for all personnel expected to use fire extinguishers to assist them in identifying characteristics of fires that cannot be suppressed with the fire extinguishers available and to provide education on proper technique. Special consideration should be given to installing separate fire extinguishers (A:C and B:C) in areas where both Class A and B hazards are present. Although triple-rated (A:B:C) extinguishers are available and would seem an appropriate choice for these situations, the only suitable triple-rated extinguisher (based on required minimum A and B rating) is the multipurpose dry chemical extinguisher. This type of extinguisher is prone to leaving a residue on all surfaces with which it comes in contact, and in the case of metal surfaces, this results in a corrosive chemical reaction that in some instances can cause more damage than the fire. A residue of dry chemical is conductive and, therefore, will cause shorts and grounds in electrical and electronic equipment. Electrical substation employees are exposed to significant risks while trying to suppress fires manually in substation buildings and apparatus. It is recommended that automatic fire protection systems be used wherever practical instead of using employee for manual firefighting. Should employees be expected to engage in manual suppression techniques they need to meet the following requirements:






Receive thorough ongoing training



Be supplied with adequate turnout gear and self-contained breathing apparatus that needs to be inspected and tested on an ongoing basis



Be tested and restricted based on adequate fitness levels



Be clean shaven (otherwise, they cannot use self-contained breathing apparatus in smoke environments without the risk of being exposed to smoke)

A.19 Equipment to property lines This clause provides additional information to 7.2.4. There are a significant number of ways that substation fires can impact the public in adjacent environs. Fire protection measures can be put in place to mitigate these impacts to the public. The following is a list of some of the types of fire-related mechanisms that can occur and can impact the public directly: 

Shrapnel—bushing failures can result in shards or fragments of bushing ceramic being propelled for distances up to 75 m (250 ft) or more. This shrapnel can be projected beyond the perimeter of the station and expose adjacent buildings.



Blast pressure—explosion in transformers can create blast pressures or pressure waves that could impact adjacent properties and structures.



Explosions and fires can result in oil spills that can migrate outside the perimeter of the substations and impact on surrounding public properties.



Oil pool fires as a result of the failure of mineral-oil-insulated equipment can cause thermal radiation beyond the perimeter of the station and possibly ignite combustible vegetation and structures.



Oil pool fires can create very large fire plumes with significant flame heights and smoke being spread from the fire pool. During periods of high winds, the fire flames and smoke plumes can be tilted significantly and expose adjacent buildings and structures. As a result, heat damage can occur to adjacent structures along with significant soot deposits in the downwind plumes area.



In substations without oil containment, burning oil spill fires have been known to spread beyond the station perimeter and impact adjacent buildings.

A fire in a substation can result in an electricity outage that may impact the general public. The following are a list of some of the indirect impacts of an electricity outage: 

Loss of heating or cooling systems during inclement weather, which can cause significant health and safety concerns



Loss of lighting and elevators in large high-rise buildings



Loss of computer communications facilities in stores and businesses



Loss of business revenue during outages



Loss of wages during outage shutdown periods

A.20 Fire barriers This clause provides additional information to 8.3. The optimum height of the fire barriers can also be calculated using the radiant heat flux calculations. Firewalls and thermal heat shields are the two common types of barriers. Firewalls are structures 44 Copyright © 2012 IEEE. All rights reserved.



constructed of fire-resistive materials such as reinforced concrete, composite materials, or masonry. Thermal heat shields use steel elements covered by heavy corrugated steel sheets on both sides. Thermal heat shields can effectively reduce the radiant heat transfer from a fire to an adjacent piece of equipment, but after a major incident, often they need to be replaced. Outdoor fire barriers do not generally fall under the constraints of a building code. Several companies have found that less expensive, nonrated, corrugated metal fire barriers have performed very effectively under fire exposures although they generally need to be replaced after the fire exposure incident.

A.21 Alternative dielectric insulating medium This clause provides additional information to 8.4.2. The elevated flashpoint property of many alternative dielectric fluids equates to the liquid being more resistant to ignition sources and therefore not catching fire until it reaches the higher liquid temperature. The temperature at which the liquid can catch fire in the presence of an ignition source, such as an energized spark, is called the flashpoint. ASTM D5222-2008 [B47] specifies the fire point should be at least 300 ºC (572 °F) to qualify as a less flammable fluid. Examples of alternative dielectric insulating mediums are listed as follows. For comparison, mineral oil has a flash point of 145 ºC (293 °F) and a fire point of 160 ºC (320 °F). 

High-molecular-weight hydrocarbons, flash point = 285 ºC (545 °F), fire point = 308 ºC (586 °F) Successfully introduced in 1977 and used for distribution transformers and fully miscible with conventional mineral oil. To ensure a fire point > 300ºC, contamination with conventional mineral oil must be <3%.



Natural ester fluids, flash point = 343 ºC (649 °F), fire point = 360 ºC (680 °F) Successfully introduced in 1997 for distribution and power transformers and fully miscible with conventional mineral oil. To ensure a fire point > 300ºC, contamination with conventional mineral oil must be <7%.



Synthetic ester fluids, flash point = 275 ºC (527 °F), fire point = 322 ºC (612 °F) Successfully introduced in 1984 for distribution and power transformers and fully miscible with conventional mineral oil. To ensure a fire point > 300ºC, contamination with conventional mineral oil must be <7%.



Silicones, flash point = 300 ºC (572 °F), fire point = 330 ºC (626 °F) Successfully introduced in 1977 for distribution transformers (typically 35 kV or less). They are not fully miscible with conventional mineral oil.



SF6 gas Considered a noncombustible insulating agent. Available for a wide variety of electrical equipment (e.g., circuit breakers and instrument transformers). It is seldom used in power transformers because of the high cost. SF6 is a greenhouse gas and produces dangerous by products under arcing conditions.

A.22 Risk-based economic analysis This clause provides additional information to 9.5.




One of the greatest difficulties is to estimate the frequency of fire for the specific hazards. Some companies have extensive fire loss histories and loss databases. These databases can be used to estimate specific fire frequencies, but the results may be poor because of the small statistical sample size based on the companies’ records. There are a number of other databases and reports that are in the public domain that provide useful data (i.e., NFPA data shop, EPRI Fire Induced Vulnerability Evaluation Methodology, and IEEE 979 Transformer Fire Survey). The IEEE Std 979 Working Group, 1994 Transformer Fire Survey estimated probability of fire is given in Table A.2.

Table A.2—IEEE 979–Working Group 1994 transformer survey Transformer voltage (kV) 69 115 to 180 230 to 350 500

Annual fire frequency per year 0.00034 0.00025 0.0006 0.0009

Additional examples of a simplified economic risk analysis can be found in CEATI Report No. T0237003022 [B52], and the book by Berry [B50] provides further examples of economic risk analyses of processes.




Annex B (informative) Quantitative methods for analysis of hazards

B.1 Calculation methods In order to calculate spatial separation based on the specifics of the substation equipment and the site characteristics, a detailed evaluation needs to be made. The following are some of the specific characteristics that are needed for the calculation: 

Type and quantity of the oil used in the equipment



The height, width, and length of the equipment tank



The size of the concrete pad that the equipment rests on



Method of pressurization (gas or conservator) for the equipment



The adequacy of the spill containment and flame-suppressing stone



The type of construction used for the target equipment or building



Size and location of the postulated oil spill fire

The calculations should consider the following factors: 

The heat release rate of the insulating fluids



Lack of spill containment



Lack of flame-suppressing stone



Prevailing winds direction and force at the site



Combustibility and type of the exposure

The design critical heat flux can be calculated using standard pool fire heat flux calculations. The SFPE Handbook of Fire Protection Engineering [B79] or the SFPE Engineering Guide for Assessing Flame Radiation to External Targets from Pool Fires [B77] outlines some of the procedures for these calculations and the annexes cover other procedures for these calculations. The key factor in determining the required spacing of mineral-oil-insulated equipment is the distance between the leading edge of the exposing flame and the adjacent target bushing or exposed transformer surface. The common criterion for the spatial separation of mineral-oil-insulated equipment has been either the equipment energy output or the volume of insulating oil used in the equipment. These important factors are somewhat interrelated, but they do not define the fire exposure potential that could exist between mineral-oil-insulated equipment. Table B.1 and Table B.2 provide typical oil volumes for oil-insulated transformers and circuit breakers. These may be used when actual values are not available.




Table B.1—Typical oil quantities in oil-insulated three-phase transformers Electrical rating, MVA ≥100

Oil volume, L (gal) ≥45 400 (≥12 000)

50 to 99

37 850 to 45 400 (10 000 to 11 999)

30 to 49

30 300 to 37 849 (8000 to 9999)

5 to 29

7570 to 30 299 (2000 to 7999)

<5

<7570 (<2000)

Table B.2—Typical oil quantities in three-phase oil-insulated circuit breakers Voltage rating, kV 230

Oil volume, L (gal) >3780 (>1000) 1890 to 3780 (500 to 1000) <1890 (<500)

138 69

If the estimated critical heat flux from the calculation will indicate that damage or a failure will occur, then mitigating measures should be considered if the equipment spacing cannot be changed. Two of the most common methods of protecting electrical equipment that has been spaced too closely are firewalls/heat shields, and the installation of water spray deluge systems. Water spray deluge systems are discussed in the fire-suppression system terms in 3.2 of this gui de. Where there is a fire exposure risk to structures outside the substation, the mineral-oil-insulated electrical equipment containing greater than 1890 L (500 gal) of oil should be separated from the adjacent property line and the edge of the transformer tank by a minimum distance of 16 m (50 ft), and there should be spill containment with flame-suppressing stone. The control building should be located away from high fire hazard equipment such as mineral-oil-insulated transformers or reactors. This should reduce the probability of fire from transferring to the control building. If physical separation between the control building and the electric equipment is not possible, then other means of protecting the control building should be employed, such as firewalls or heat shields, as well as the installation of water spray deluge systems at the transformer. Damage to adjacent equipment and structure because of the heat transfer from the exposing flame is a function of the materials they are made from. As an example, the critical element of most transformers is the ceramic bushing. Studies indicate that a heat flux as low as 5 kW/m2 will cause a ceramic bushing to fail. Table B.3 lists critical heat flux values for substation equipment and structures. The design critical heat flux at the property line should not exceed 20 kW/m2.




Table B.3—Radiant heat flux level and damage Impact of radiant heat flux Sufficient to cause damage to process equipment Equipment failure

Heat flux (kW/m2) 37.5 35

Damage to unprotected metal

30

Spontaneous ignition of wood

25

Cable insulation degrades

20

Pilot ignition of wood

12.5

Plastic melts

12.5

Pain threshold reached after 8 s Second-degree burns after 20 s Possible failure of ceramic bushings

9.5 5

Skin burns

5

The heat flux nomographs in B.2 provide a graphic method of estimating the radiated heat flux at the adjacent equipment. The U.S. Nuclear Regulatory Commission (NUREG) Fire Dynamics Tools spreadsheet can also be used to estimate the radiated heat flux. Two spreadsheets are available, one ignores wind9 and one considers wind.10 Documentation11 for the spreadsheets is also available.

B.2 Heat flux nomographs The following radiant heat flux nomographs are reprinted with permission from CEATI in Report T023700-3022 [B52].12 The incident heat flux on a vertical target facing a cylindrical exposure source varies with elevation. The maximum incident heat flux at a fixed horizontal distance occurs at an elevation midway between the base and top of the exposure source. The nomographs can be used to determine the performance-based spacing criteria for mineral-oil-insulated equipment and ceramic bushings. Two types of nomographs are presented, and the steps to use them are given as follows: a)

Figure B.1 to Figure B.4 depict the heat flux isograms for the 50 m² through 300 m² (540 ft² through 3200 ft²) transformer oil pool fire exposure sources. The 5 kW/m² (0.44 Btu/s-ft²) isoflux line, the heat flux that may damage bushings, is bolded for ease of identification. Note the symmetry about the horizontal axis passing through the mid-height of the source fire. Using these nomographs: 1)

Determine the height of the bushing and draw a line horizontally from the height scale on the left.

2)

Where it intersects the 5 kW/m2 vertical curve, draw a vertical line down to where it intersects the target distance from the pool fire edge scale.

3)

This result can then be used to determine the spacing from the edge of the postulated pool fire to the nearest adjacent bushing.

9

This document is available at http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1805/05.1_Heat_Fluxx_Calculations_ Wind_Free.xxls. 10 This document is available at http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1805/05.2_heat_flux_calculations_ wind_rev1.xls. 11 This document is available at http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1805/final-report/. 12 Figure B.1 to Figure B.5 are reprinted with permission from CEATI, Report T023700-3022, © 2005.




b)

The nomograph in Figure B.5 is provided to allow a rough estimate of either the maximum transformer curbed area or the minimum distance between the curbed transformer edge and the nearest ceramic bushing when the transformer is insulated with mineral oil. 1)

To determine the maximum transformer curbed area, draw a horizontal line from the known distance on the vertical, maximum 5 kW/m2 isogram distance scale, from the intersection with the vertical or horizontal target curve; then, draw a vertical line to intersect the horizontal, area enclosed by curbs scale. This intersection will provide an estimate of the maximum transformer curbed area.

2)

To determine minimum distance to the nearest ceramic bushing, draw a vertical line from the known area on the horizontal, area enclosed by curbs scale, from the intersection with the vertical or horizontal target curve; then, draw a horizontal line to intersect the vertical, maximum 5 kW/m2 isogram distance scale. This intersection will provide an estimate of the distance to the nearest ceramic bushing.




32.8

Exposure Source Flame Height

9.8

2

25 kW/m 2 20 kW/m 2 15 kW/m 2 10 kW/m 2 4 kW/m

29.5

9

26.2

8

) t f ( n 19.7 o i t a v 16.4 e l E t e 13.1 g r a T

23.0

) 7 m ( n 6 o i t a v 5 e l E t e 4 g r a T

6.6

2

3.3

1

0.0

0 0.4

9.8

2

m / W k 0 9

2

m / W k 0 8

2

m / W k 0 7

2

2

2

2

m / m / m / m / W W W W k k k k 0 0 0 0 6 5 4 3

2

m / W k 5

2 2

m / m / W W k k 3 2

2

m / W k 1

3

1

10

100

Target Distance from Pool Edge (m) 1.31

10

100

328

Target Distance from Pool Edge (ft)

2

2

Figure B.1—Incident heat flux on a vertical target versus distance for a 50 m (540 ft ) pool fire area exposure source [B52]




42.6

13

39.4

12.2

36.1

11

32.8

10

Exposure Source Flame Height

2

25 kW/m 2 20 kW/m 2 15 kW/m 2 10 kW/m 2 4 kW/m 2

29.5 ) t

f ( n 26.2 o i t a 23.0 v e l E 19.7 t e g r 16.4 a T 13.1

) m ( n o i t a v e l E t e g r a T

3 kW/m

9 8 2

7 6

2

2

m / m / W W k k 5 0 8 8

m / W k 0 7

2

m / W k 0 6

2

2

2

2

m / m / m / W W W k k k 0 0 0 5 4 3

m / W k 5

2

m / W k 2

2

m / W k 1

5 4

9.8

3

6.6

2

3.3

1

0.0

0 0.5

1

10

100


10

100

328

Target Distance from Pool Edge (ft) 2

2





2

2





Exposure So urce Flame Height

2

25 kW/m 2 20 kW/m

16.8 52.5

16

15 kW/m

2

10 kW/m

2 2

45.9

14

39.4

12

32.8

10

26.2

19.7

T a r g 13.1 e t E l e v 6.6 a t i o n ( 0.0 m )

4 kW/m 2 3 kW/m

2

7 8 5

6

k W / m

2

2

2

2

2

7 0 k W / m

6 0 k W / m

5 0 k W / m

4 0 k W / m

3 0 k W / m

2

2

2

5 k W / m

2 k W / m

1 k W / m

4

2

0 0.5

1

10

100


10

100

328

Distance from Pool Edge (ft) 2

2





2

Figure B.5—Maximum distance allowable for 5 kW/m allowable heat flux for various fire pool areas [B52]




Annex C (informative) Selection of fire protection systems and substation design

C.1 Compliance Some substation owners operate in jurisdictions with mandated fire protection requirements for electrical substations. In these cases, the mandatory compliance with the appropriate codes and standards is a critical fire protection performance objective. JEAG 4607-1999 [B72] adopted in Japan is one such mandatory compliance code. There are a number of other quasi-compliance objectives that the substation owner may have to use for the design of a new substation or changes to an existing one. Specifically, recommended practices or guidelines in the industry set out “good engineering practice.” Therefore, a substation owner can be exposed to some pressure to meet these practice standards or guidelines. If an incident occurred and it was found that the substation owner did not comply with the general guidelines or recommended practices within the industry, then such information may be used in any litigation based on the incident. Also, the failure to be duly diligent may also create political or customer satisfaction related issues. The information in this guide, along with the NFPA and CIGRE substation fire protection documents, should be considered in the design of a new substation or changes to an existing one to show diligence with regard to fire protection objectives.

C.2 Electrical supply reliability Electrical supply customers are demanding higher levels of reliability for electrical services. This causes electrical power utilities to review their operational reliability. Also, a number of utilities had been required by their regulatory bodies to examine and justify their levels of operational reliability. Many utilities are setting goals of having operational reliability of 99.96% or greater. As a result of these high levels of operational reliability, the normal frequency of fires in circuit breakers and transformers could have a significant impact on the utility’s operational reliability. Secondarily, the provision of suitable fire protection could significantly lessen the station or equipment outage time, thereby helping the owner to meet its operational reliability objective. In the past, it has been difficult to quantify the impacts of fire-related outages on the customers. Several research programs have quantified the societal impacts of substation outages. The societal impacts can be quantified in terms of the dollar value per megawatt lost for different mixes of customers (industrial, commercial, residential, and mixed). With the quantification of the societal loss, it becomes easier to estimate the benefits (shortened outage each time) from the provision of fire protection. For example, the fire protection will reduce the expected outage time from 24 h down to 2 h; then the benefit derived is the societal impact for the station output for the 22 h period.

C.3 Revenue and asset preservation One major objective of all companies that own substations is to generate revenue, or at least generate sufficient cash flow to cover their operating costs. There are some substation fire-related losses that can significantly affect a company’s ability to generate revenue and profit. A careful analysis of the substation equipment and operation can identify critical equipment that creates a significant fire hazard. Based on the




possible revenue loss from a fire in a critical structure or piece of equipment, automatic fire protection systems may be justifiable. Fires in electrical substations can have a very large impact on the station operating assets. A fire in a substation control building can have a significant long-term impact on the ability of the station to operate. Therefore, assets such as substation control buildings are very critical and should be reviewed to determine the adequacy of the planned fire protection. Another example of significant substation assets would be grouped transformers. There are very few fire-protection-related systems that can prevent a failure or fire in a transformer, but systems such as water spray deluge systems can suppress a fire in the transformer that has failed and likely can prevent it from spreading to adjacent transformers. All utilities operate in regulated political environments. A major substation fire and accompanying outage may create a number of political issues that can affect a utility’s revenue. The utility regulators can review the utility’s operation and impose fines or directed actions to improve deficiencies. In government-owned utilities, pressure can be imposed on the operating personnel to change their practices and philosophies to address the risk of major outages. The utility or owner shareholders can also apply pressure to the management of its substations to improve reliability. Customers can cause changes to be made in the level of overall operational reliability through political, regulatory, or organizational channels. And in special cases, the customers can show their dissatisfaction with the utility’s operational reliability by using another utility supplier.

C.4 Oil-insulated energized equipment There are a wide range of types and causes of fires experienced in electric power substations. The types of fires are based on the equipment and systems used in the substations. Fire hazards include outdoor or indoor oil-insulated equipment, oil-insulated cable, and fuel storage facilities for engine generator sets used for standby station auxiliary power. To understand fully the nature of the hazard, the failure mechanisms of energized oil-filled equipment need to be fully understood. Most transformer oil is essentially a mineral oil. The flash point will generally be around 150 °C (300 °F), with an autoignition temperature of approximately 350 °C (655 °F). Whereas these conditions are generally not achieved during normal operation, an internal electrical fault may generate temperatures well in excess of 540 °C (1000 °F) and are therefore capable of igniting the oil. Internal faults can result from the infiltration of water, failure of core insulation, exterior fault currents, and tap changer failures. Research has found that major internal arcs within transformers can create hydrogen and acetylene gas bubbles in the transformer tank. As the oil heats during this fault process, it also expands both as a liquid and as a vapor. Both of these actions cause the internal pressure to rise and may result in failure of the transformer tank. When the tank ruptures, the gas and oil mist is then rapidly released to the atmosphere up to 15 m (50 ft) away, where they auto ignite upon contact with oxygen. In the atmosphere, a deflagration can occur. The resulting deflagration can create significant pressure waves, thereby severely damaging adjacent exposures. The burning oil mist can also ignite adjacent combustible structures or surfaces. As larger substation equipment may contain oil quantities in the range of thousands of liters, the magnitude of these events can be catastrophic in nature. Equipment provided with fixed fire protection may see piping blown away as a result of the failure. Other attached appurtenances such as bushings, cooling fans, or even oil expansion tanks may be shattered or sheared off. Large power transformers have been known to lose an entire side during these failures. Bushing internal arcs can also create hydrogen and acetylene gas bubbles that can cause the bushing ceramic to fail due to the resulting internal pressure. There are a number of documented incidences where the bushing ceramic shrapnel has been projected over 75 m (250 ft). The bushing ceramic shrapnel can




cause the failure of ceramic bushings on adjacent electrical equipment, damage adjacent buildings, and even injure substation staff or the public. The flames and fire plume from a transformer oil fire can cause the failure of overhead bus structures, transmission lines, and feeder lines. The flaming portion of the fire can rise to a height approximately 2.5 times the diameter of the spill fire. This region can have sufficiently high temperatures to cause the failure of steel structures and buswork. The resulting oil-fueled fire plume can result in soot contamination downwind of the fire. The high concentration of carbon particles that gives the smoke its characteristic color will also conduct electricity and initiate flashovers. Furthermore, any firefighting operations will add to the conductivity by providing a steam component in the plume. Even dry chemical particles have been known to become conductive in high humidity environments by absorbing moisture and therefore acting like “airborne mud.” Typically, this effect is seen between high-energy points such as exposed conductors or bushings on transformers. When soot contamination impacts public structures, it becomes a major concern for the operator. The specific exposure of the downwind contamination is based on the wind speed and direction during the actual fire event. See the discussion on incident management in D.3 for further information on dealing with soot contamination. Mineral oil spills can be expected to pool and/or run with the effect of exposing adjacent equipment or structures to fire. Oil may form a large pool fire depending on the volume of oil, spill containment, slope of the surrounding area, and type of the surrounding ground cover (i.e., stone or soil). Any mineral-oil spill fire can create significant radiant heat exposures to adjacent structures, buildings, or equipment. The footprint of the spill fire and the distance between the edge of the spill fire and the exposure are the key factors in determining whether a fire will damage or ignite the adjacent exposure. Equipment such as adjacent phases of transformers, spares, or banks can also be heated to a point of case failure and provide additional fuel to the incident. One major concern with spill fires is that these fires can spread to other areas of the station and possibly outside of the station. A thorough analysis of the station grades and containment provisions around mineral-oil-insulated equipment needs to be completed to determine where a possible spill fire can spread. Containment provisions can then be designed to minimize oil spread in the event of a spill. Oil has been known to enter grade-level cable trenches and flow into control buildings, creating significant damage to the buildings and equipment, as well as compromising the operational control of the station. In addition to mineral oil, other insulating mediums are used for certain types of electrical equipment in place of oil that are noncombustible or of limited combustibility such as synthetic oils or sulfur hexafluoride gas. The high heat environment of a fire may result in potentially toxic by-products such as dioxin and other chemicals. Smoke and soot from such fires cause widespread contamination and require extensive decontamination operations. This is of most significance when the equipment of origin is located in a building or an underground vault.

C.5 Fire detection and signaling systems

C.5.1 General The provision of fire alarm and detection systems may be required by the building and fire codes based on the size, height, and hazard of the new or existing substation building. The substation designer should work with the local authority on determining the code-required level of detection and alarm. The local codes will




also reference specific design, installation, and testing standards for fire alarm systems. Some codes only require fire alarm and detection systems when the building occupancy exceeds certain levels. Smaller substation facilities should be analyzed by the substation designer to determine whether the early detection of a fire in a substation building will provide benefits in the protection of the assets and station operation. For example, if the substation building is unmanned but the company personnel and fire department (or fire brigade) personnel have sufficient time to respond to an event before the building has major damage, then a fire alarm and detection system should be considered. For stations where the company’s response is greater than an hour, or where there are no responding fire personnel, the value of the provision of a fire alarm and detection system may not warrant the expenditure. Some companies have a policy of providing fire alarm and detection systems for all major unmanned remote stations so that they have some remote indication of the incident and do not simply rely on the station operational telemetry trip signals. Some companies have a policy of providing spot type smoke or heat detectors tied to the substation building security system in order to give them rudimentary remote indication of a fire occurrence. The substation designer has to evaluate and select the three major components (fire detection, fire alarm control panel, and signaling system) of any fire alarm system and determine the type of equipment most suitable to the specific application. This analysis should be done in conjunction with the fire protection engineer and/or a fire alarm manufacturer or specialist.

C.5.2 Fire detection equipment selection criteria The following key criteria should be considered when selecting the appropriate type of fire detection equipment: 

Emergency personnel response time: If the station is unattended, personnel are present infrequently, and company personnel or fire emergency personnel cannot respond for hours, then it may not be cost-effective to install an air-sampling detection system that can detect a fire in the smoldering stage.



Expected fire growth: Some fires will grow very quickly (transformer explosion or cable highenergy arc fault), and others will grow more slowly (control panel relay failure and fire). The analysis should look at the specific type of detector to detect this fire. Specifically, it may not be appropriate to use a very sensitive detector like an air-sampling system to detect a high-energy, arc fault fire. Slower detectors such as thermal detectors will be able to pick this up within seconds of the initiation of the fire.



Type of fire signature: Each fire has a specific fire signature that will have different characteristics of heat release, smoke production, smoke density, and smoke particulate size. One common example is the type of fire detection for a control room facility with exposed control and power cable. The cable jacketing combustion products produce a fire signature with large-size smoke particles. Ionization detectors have greater difficulty detecting these larger size particles than photoelectric detectors.



Operational success: Care should be taken in specifying the type of detection that will not cause false alarms due to the existing substation processes. A simple example would be the use of sensitive smoke detectors in lunch rooms where a toaster or microwave oven would be used.



Ceiling and building configuration: The height of the ceiling and whether the ceiling has deep beam pockets can significantly influence the type of detector used and the spacing of the particular detector to provide the required response time.




The following are some alternatives for detection in substation buildings: Control, relay, and telecommunication rooms: 

Air sampling detection for critical facilities with a rapid response time for company and emergency personnel



Spot-type photoelectric detection at the ceiling and below the subfloor areas for these facilities

Feeder sections and switchgear areas: 




Spot type photoelectric detection

Cable spreading rooms and cable tunnels: 


General substation building areas: 

Spot-type photoelectric detection at the top of stairs

Shops, office, and warehouse areas: 

Spot type rate-compensated thermal detectors

Transformer vaults/oil-insulated equipment areas: 




Rate-compensated thermal detectors for deluge system operation or wet/dry pilot detection

C.5.3 Fire alarm panel The most commonly used types of panels and systems are the relay-based systems and the computer-based addressable systems. Relay-based systems and panels are older technology that is still widely used because of its reliability and immunity to electromagnetic interference. This type of technology is based on fire detection or supervision devices connected on an individual zone. The fire alarm indication given is one of a particular zone. The zone could be wired to an individual device or group of devices, and commonly they are zoned by floor. A fire alarm only indicates whether a particular zone has gone into alarm. Computer-based addressable systems are becoming more commonly used because of their lower cost of installation, real-time information, and computer-based user interface. With the addressable system, each individual detection device communicates with the main computer. In the event of a specific device going into the alarm, the system can provide real-time information on the specific detector in alarm. The system also can provide information on detectors that are getting dirty and require cleaning. One of the major advantages of the computer-based system is the graphical user interface of the system. This user interface can provide a graphic screen showing the individual devices on a floor plan or schematic drawing. In the event of the device going into an alarm, the interface will flash the symbol for the device on the floor plan, give real-time information of when the device went into alarm and can allow further screens to be accessed to give one-line diagrams or photos of the specific device that is in alarm. The graphics interface will allow the operator easily to change the sensitivity of the detection devices, program them out for maintenance work, and check the sensitivity of all the devices. The shortcomings of the addressable systems are the high cost of site-specific software interfaces, degrade mode, and susceptibility to electromagnetic interference.




Some addressable systems have a degrade mode that when a signal or indication occurs on the system that is not known to the microprocessor, the fire alarm panel will operate all signaling devices and initiating circuits. If the panel is operating initiating systems for gaseous-preaction systems or deluge systems, then the degrade mode will cause them to operate. Many companies avoid these problems by only initiating circuits for gaseous, preaction, and deluge systems wi th relay-based fire alarm panels. In order to minimize problems with electrical interference of computer-based addressable systems, many companies have specific test criteria that require systems be designed and constructed with an acceptable level of electrical interference immunity. The following is a list of specific electrical interference tests used: 

Conducted transient voltage tests: The equipment is tested for surge withstand capability in accordance with IEEE Std C37.90.1TM-2002 [B61].



Radiated transient voltage (JAWS) test: This test simulates a “worst-case” industrial noise environment consisting of high-voltage relays operating in close proximity to solid state equipment. It is similar to subclause 5.3.1 of ANSI/IEEE 518-1982 [B4]. This standard is withdrawn, but the test is still valuable.



100 kHz Ring wave and combination wave surge tests for low-voltage ac power circuits: These tests are based on IEEE Std C62.41 TM-1991 [B63].



Radiated high-frequency continuous wave tests: These tests look at the equipment’s susceptibility to radiated waves from radios and cellular phones. Although there are no standard tests, the following may be used as a guide in establishing tests. The equipment shall be tested to determine the sensitivity of the equipment to radiated highfrequency wave interference coupled from nearby radio transmitters. The equipment shall be subjected to transmission from each of the following output frequencies: 1)

15 W in the 47 MHz through 48 MHz band

2)


3)


4)

0.6 W, 832 MHz (cellular phone region)

For the tests, the equipment enclosure (chassis) that acts to shield the solid-state portions of the equipment shall be in the normal in service (closed) condition and in the open condition. When the cabinet door is open, the radio antenna shall be brought to within 300 mm of the exposed operating circuits. The radio transmitter shall be operated both continuously and interrupted once per second. Each test shall be performed with the radio antenna oriented in each of the X, Y, and Z planes with respect to the exposed operating circuits.

C.5.4 Signaling systems The two key objectives of signaling systems are to warn the building occupants of a fire and to provide a remote signal to initiate an emergency response to the facility. There are various codes that require that signaling devices be installed within the building or station so that occupants in any area of the building are informed of a fire situation. The initial layout of the signaling appliances can be done based on audibility calculations contained in the SFPE Handbook of Fire Protection Engineering [B79]. Once the installation is complete, it should be tested using sound meters to determine the audibility in all areas of the station. In some areas of the station, the ambient noise levels may be too high to allow the installation of audible signaling devices without exceeding the allowable noise limits. The codes normally require that the signaling devices have a sound 61 Copyright © 2012 IEEE. All rights reserved.



level 15 dB above the normal ambient levels. If the normal ambient levels are above 85 dB, then the required resultant sound level would have to be 100 dB, which is in excess of normal safe limits for personnel. The alternative solution in areas with high ambient noise levels is to install signaling devices with visual strobe lights. The fire alarm signaling system may also be designed to send a signal to the local fire department. Fire detection signals should be sent to a central location (e.g., a utility’s control center). The newer addressable systems provide a new level of information in the event of an alarm condition. These systems can send out digital e-mail indications of alarm or trouble conditions to wireless phones or other communication devices, they can send e-mail to specific e-mail accounts, and the systems can be accessed and controlled remotely over a local area network or Internet system.

C.6 Benefit/cost analysis One of the most common economic risk analysis measures is a benefit/cost analysis. Other methods can also be used as preferred by the user. The benefit/cost analysis is calculated using Equation (1). Businesses often require a benefit/cost ratio greater than 2, and at minimum, it should be greater than 1. A benefit/cost ratio of 2 means that the avoided fire loss cost or benefit is twice the cost of the fire protection. Therefore, it is a good investment. Refer to Table D.1 for relative fire frequency information. Once the potential financial loss due to a fire has been calculated, the designer should input costs and effectiveness of any proposed fire protection measure into the benefit/cost equation and determine the B/C ratio. If the B/C ratio is less than 1, then the provision of the fire protection measure is not an acceptable investment. Simple benefit/cost example

A substation has four 138 kV single-phase oil-insulated transformers. One of these transformers is a spare and is located remotely from the others. The load supplied by these transformers is 25 MW. A water spray deluge system is being considered to suppress or control a fire in the transformers. The deluge system is expected to protect the adjacent transformers. The estimated cost of a deluge system for all three transformers is $60 000. The individual transformers have a replacement value of $300 000. The company’s Chief Financial Officer asks whether this is a good investment. 

The company uses a discount rate of 10% and requires that all investments have a benefit/cost ratio of greater than 2. The assigned value of energy is $25/MW. The standard amortization period is 25 years.



The annual frequency of fire for a single 138 kV transformer is estimated to be 0.00025/year; see Table A.2. Therefore, the combined frequency for the three transformers is as follows: p( F ) = 0.00075 fires/year.



Although the probability of a fire occurring in any of the three transformers is the same, the highest risk to adjacent transformers would be for a fire starting in the center phase because there are units on either side at risk. The fire is assumed to originate in the center transformer in the bank of three single-phase transformers. In this example, it is assumed that in the absence of the suppression, the fire will spread to destroy the two adjacent transformers. The spare transformer is not affected because it is remote from the other transformers.



In many cases, a deluge system cannot prevent the loss of the transformer in which the fire originates. For this study, the transformer is assumed to be a total loss. However, the deluge system is expected to be effective in reducing the probability of the fire from affecting the 62 Copyright © 2012 IEEE. All rights reserved.



adjacent transformers. In this case, the probability of the adjacent transformers being saved is assumed to be 90%. The effectiveness of the deluge system protecting the adjacent transformers is then as follows: e( RM ) = 0.9. 

The estimated station outage period for this scenario is the difference between the outage time to replace all three transformers (a fire in the center transformer could destroy all three transformers) and the outage time to replace the center transformer (assuming the deluge system will protect the adjacent transformers). The outage time to replace a single unit is 5 days and to replace three units is 40 days. Therefore, the expected net outage loss period i s 35 days.



The expected lost revenue is 35 days × 24 h per day × 25 MW/h × $25/MW = $525 000.



Because this is a simplified analysis, the societal benefits and operating costs will not be considered. These costs could be significant. Examples include societal costs, loss of reputation, or possible litigation costs.



It is not known when a transformer fire may occur over the 25 year period. To help analyze the problem, the net present value (NPV) of the annual revenue and equipment losses will be used based on the costs being equally divided over the 25 year period. This simplified approach ignores inflation, depreciation, and other factors. The NPV of a series of equal payments is calculated using the following formula13:

 1− (1+1i ) NPV = R  i 

n

  

(C.1)

where NPV R n i

is the net present value is the periodic payment is the number of periods (years in this case) is the discount rate



The yearly amount for the annual revenue loss is $21 000 ($525 000/25). The NPV over 25 years with a discount rate of 10% is $190 618.



The yearly amount for the equipment loss is $24 000 (2 × $300 000/25). The NPV over 25 years with a discount rate of 10% is $217 849.



The benefit/cost ratio is calculated using Equation (1) of 9.6 given as follows: B / C =

benefit cost

=

p ( F ) × e( RM ) × [ RC + LR + SB + OC ] RM

where benefit

cost p(F) e(RM) RC LR SB

is the value associated with lost revenue, operation, and building replacements that are avoided if a major fire is prevented (benefit of avoided loss) is the cost to protect against damage due to major fire is the probability of major fire (probability of an outage due to a fire) is the effectiveness of remedial measure is the replacement cost of facility and equipment lost due to fire is the lost revenue (in $) due to fire (lost load × mill rate) is the societal benefit (in $) lost due to customer outages created by fire

13

Formula taken from http://en.wikipedia.org/wiki/Annuity_(finance_theory).




RM OC

B / C =

is the cost of remedial measure is the operating cost associated with manning the station due to fire damage of supervisory equipment p ( F ) × e( RM ) × [ RC + LR + SB + OC ] RM Parameter p(F) e(RM) RC LR SB OC RM

B / C =

Value 0.00075 0.9 $190 618 $217 849 $0 $0 $60 000

0.00075 × 0.9 × [$190 618 + $217 849 + $0 + $0 ] $60000

=

$276 / $60 000 = 0.005

Conclusion The calculated benefit/cost ratio of 0.005 is considerably less than the minimum required ratio of 2. The proposal to install deluge protection should be rejected because it does not provide a large benefit given the small risk involved. Other fire-protection measures could be considered or the risk could be transferred by purchasing insurance to cover the possible loss of the assets (transformers) and the revenue. These other measures can also be analyzed using this economic risk analysis methodology.




Annex D (informative) Fire emergency plan, incident management, and recovery

D.1 Purpose The purpose of this annex is to provide substation asset owners information to manage substation fire incidents effectively with private or public emergency responders. This annex is not intended to be inclusive of all the issues and considerations of a complete emergency response plan but to be an overview of the basic elements that need to be addressed. To complete an actual plan, the asset owner should obtain the services of a qualified emergency planning professional.

D.2 Preplanning for the fire emergency The fires that result from oil-filled equipment failures tend to be large combustible liquid pool fires, with hot metal inside and around them. The heat from the fire will be intense, unless mitigated in some fashion by built-in features such as walls, containment, stone bases, and fixed fire protection systems. Furthermore, the smoke from these events is typically thick and black. Coupled with the potential hazard of energized electrical equipment, this makes emergency response and firefighting in substation environments difficult and hazardous. The following three essential elements of a fire emergency plan need to be established prior to the incident to avoid confusion and allow for effective management of the incident: a)

A written and accessible fire preplan consisting of the following elements is required to assist emergency responders in their incident management activities and to assure their safety. This cannot be done during the emergency and should include drawings that include the following: 1)

Site drawings

2)

Access routes

3)

Building locations

4)

Floor plans

5)

Ventilation capabilities

6)

Identification of major hazards

7)

Locations of energized oil-filled equipment

8)

Description of the nature and locati on of electrical hazards

9)

Location of detection/fixed protection (if any)

10) Location of water supplies (if any) 11) Electrical single line drawings b)

The fire preplan should include the organization and responsibilities of the incident management team including: 1)

Preestablish lines of communication.




2)

Identify who is going to be the emergency response organization (private or public) and who will be the incident commander. They will have overall authority for the management of the incident.

3)

Identify site owner person in charge.

4)

Preestablish protocols so that authority is with the most senior, knowledgeable individual at all times. This person acts as liaison with the incident commander in charge of the emergency response.

5)

Develop written organization charts that identify positions and reporting relationships.

6)

Conduct periodic site walk downs/drills to familiarize emergency responders and owner representatives.

7)

Predetermine role of site owner.

8)

Determine participant role in the isolation of affected equipment/electrical circuits (local or remote).

9)

Assign team member responsibilities in assisting emergency responders in size up of incident.

10) Identify those qualified to use a self-contained breathing apparatus. Environmental consideration during preplanning needs to be given to the retention of oil and firewater runoff during and prior to firefighting operations. Amounts of absorbents and diking materials will need to be determined as well as where such material can be expeditiously procured in a short period of time. Consideration may be given to the installation of a secure cabinet at the entrance to the substation. This could be accessed by first responders and would contain vital information such as owner’s personnel contact information, fire preplan drawings, and a list of special hazards (e.g., PCB equipment) on site.

D.3 Incident management The following personnel safety hazards must be identified: 

Establish that responders do not enter any area where electric equipment is located until the equipment is deenergized by a qualified individual.



Anticipate overhead structures that could be rendered unstable by fire exposure.



Establish access and egress routes for firefighting operations.



Anticipate potential changing wind direction.

Anticipate the fire scenario.

Radiant heat from a fire involving oil-filled transformers and other equipment will pose a severe threat to neighboring equipment/structures and operations. If the distance or separation between the fire and exposures is inadequate and fixed protection is not provided, then the damage may range from blistered paint to additional failures, oil involvement, and propagation to adj acent structures. Convective heat transfer from the fire and smoke plume will threaten overhead equipment. This may include steelwork supporting the conductors or the conductors themselves. As is the case with most hydrocarbon fires, smoke from a mineral oil fire will be voluminous, black, and obvious to the public. As such, it will be seen as a source of air pollution. Although this will prompt demands on the fire service to take steps to control the event, premature or inappropriate action may cause




soil or water pollution whose effects far outweigh the damage to the atmosphere. As previously mentioned, the smoke itself may be conductive because of the presence of carbon particles and steam. If a fixed fire-suppression system is present, then the responders should identify the type and supplement the water supply through fire department connections. Fixed water systems are installed for exposure protection from adjacent fires, as well as to suppress the fire on the equipment of origin. However, unless properly designed and installed, the fire-suppression system on the equipment of origin may be destroyed or damaged in the initial event. Exposure consideration will be critical with oil-insulated electrical equipment. Fire exposure to surrounding structures and buildings maybe of longer duration where oil-insulated electrical equipment is involved because of the time required to deenergize the electrical equipment for firefighter safety. Additional time may have to be considered where it is necessary to have a qualified electrical equipment operator respond to the scene to deenergize the equipment involved. Establish what is needed to extinguish a fire involving oil-filled electrical equipment.

Mineral-oil-insulated electrical equipment typically uses a mineral oil with a high flash point in the range of 150 °C (300 °F). High-flash-point oils can be extinguished using water hose streams alone. However, unless there is total spray impingement over the spill surface and any metals objects are cooled, the fire may not be extinguished. Successful extinguishment of oil-filled electrical equipment fires has been achieved by the use of water based extinguishing agents, such as firefighting foams and surfactants. These agents have achieved excellent results when employed in sufficient quantity with water and at the proper application rate. The enhancements are faster fire knock down, prevention of reflash, and use of less water, which reduces the amount of runoff, in turn, lessening the environmental impact. Each of these agents brings a set of advantages and disadvantages with it, and it is up to the fire service to decide which will provide it with the best combination for its operation. For example, most public fire service agencies use aqueous film forming foams (AFFFs) due to their superior knockdown capabilities and good record on aircraft rescue applications. However, with large oil-filled equipment, there may be a fire in depth, associated with highly preheated metal components of significant mass. Industry experience has shown that more conventional protein or fluoroprotein foams may be more appropriate in these cases. There are other extinguishing options available including dry chemical and gaseous agents such as carbon dioxide. These agents can achieve extinguishment when the equipment is deenergized, and the fire is small and/or confined by location indoors. However, they may not be successful on large outdoor fires due to their limited cooling abilities and susceptibility to wind and thermal drafts. Plan for what is needed to control and capture oil and water runoff.

Environmental exposure will involve the containment of oil runoff from the equipment involved. The runoff can involve burning oil from the fire as well as oil floating on top of the water that is used to suppress the fire. This will need to be contained and prevented from running into nearby streams, rivers, lakes, and so on. The following should be considered in developing spill mitigation plans: 

Slope of site



Drainage



Cable trenches and control building



Oil containment



Value of station stone




D.4 Recovery The primary purpose of a post-fire recovery plan is to put in place procedures to promote the continued safety of emergency responders as well as owner personnel responsible for damage assessment and equipment restoration. The secondary purpose is to expedite the restoration of service to customers and to manage the potential ongoing environmental exposure of oily/contaminated water and fire-suppression agents. Issues for consideration include the following: 

Air quality must be investigated, particularly in buildings that may be contaminated with PCBs and asbestos.



Qualified personnel need to conduct air quality assessments; public fire departments do not normally provide this service.



If air quality is not acceptable and restoration has to be expedited, then owner personnel will be required to wear self-contained breathing apparatus or respirators depending on what contaminate is present.



Fire protection systems that have operated should be restored to service. Discharged fire extinguishers should be recharged.



A detailed damage assessment needs to be conducted to establish what needs to isolated prior to restoration of service.



A root-cause analysis should be performed to minimize the potential for reoccurrence.

D.5 Energized equipment All alternatives to deenergize all equipment in the location of a fire must be explored prior to initiating an attempt to extinguish the fire. There are techniques, beyond the scope of this guide, in fire protection handbooks and other documents that may be used when equipment cannot be deenergized and the fire must be extinguished.

D.6 Loss history A study was carried out on the reported substation fires by a major utility for the period from 1971 to 1994. The data in Table D.1 give information on the types and relative percentage of fires experienced. These values should be used only as “order of magnitudes” because the data are limited to one utility. It is expected that the type and percentage of fires that occur will vary significantly from utility to utility.

Table D.1—Substation fires Types of fires Oil-insulated circuit breakers Current transformers Power transformers Hot work (welding, cutting, and grinding) Voltage potential transformers Engine-driven generators Arson Smoking Lightning Flammable liquid storage or handling Terrorism Miscellaneous fires

Percentage of total 14% 14% 9.3% 9.3% 7.8% 7.0% 6.3% 6.0% 4.7% 3.1% 1.6% 15.8%

The miscellaneous fires category above covers a wide range of fires from grass fires to a plastic wall clock failing and catching fire. It is impossible to predict all of the different types of fires that can occur. 68 Copyright © 2012 IEEE. All rights reserved.



Annex E (informative) Examples The following examples show the various methods for analyzing and applying the fire protection concepts and principles presented in this guide. The information used is from a typical substation that a substation engineer may encounter. The example follows the steps that would be commonly used to carry out the fire protection analysis.

E.1 Determining the flame front

E.1.1 Transformer without containment When a station lacks oil containment or spill containment, the designer should carry out an analysis of the station to determine the fire exposure that a spill fire from a transformer will create. The critical conditions that should be analyzed are as follows: 

The station grades: The grades can cause the spill fires to spread and flow in specific directions where the grade slopes or more randomly where the station grades are flat. These grades can cause the spill to spread toward critical station equipment or facilities.



Ground cover: Ground cover material such as a 15 cm (6 in) deep layer of stone will lessen the flame height of a spill fire, whereas hard-packed ground cover increases the spread of the spill fire.



Transformer oil volume: The larger the volume of oil, the larger the spill fire will be and the greater distance that the spill fire can spread.



Transformer failure mode: A transformer tank failure can spread a large amount of oil more quickly than a bushing failure.

The design of oil-containment systems can provide some insight into the oil flow and pooling during a fire. Subclause 7.1 of IEEE Std 980-1994 states that typical containment systems are designed to extend 1.5 m to 3.0 m (approximately 5 ft to 10 ft) beyond the edge of the tank in order to capture a majority of the leaking oil. Although a clean hole near the bottom of a tank will likely project much further than this, it is a practical range. The smaller distance might be used for smaller transformers and the larger distances for larger transformers. The initial spill fire may extend 1.5 m for a small transformer to 3.0 m for a large transformer. These values, with consideration for spread because of the site grades, can be used to estimate the flame front for the majority of fires. The designer needs to recognize that there is a risk that the flame front will be larger than this estimate.

E.1.2 Transformer with containment and without flame-suppressing stone A transformer and oil containment are shown in Figure E.1. The containment wall is not the same distance from the transformer foundation on all sides. This often occurs due to physical constraints of the installation or to provide additional storage volume. In this case, the oil-containment walls are 2.6 m (8 ft,




8 in) on the short sides of the transformer and 3.8 m (12 ft, 4 in). The distances are consistent with the distances discussed in E.1.1. Without stone in the containment, the flame front may extend to the edge of the walls. The perimeter size of the flame front will be 11.5 m (37 ft, 8 in) × 13.5 m (44 ft, 4 in) when the wall thickness of 15 cm (6 in) is taken into account. When evaluating fire separations, distances should be measured from the perimeter of the flame front or spill containment.

Figure E.1—Foundation and oil-containment plan E.1.3 Transformer with containment and flame-suppressing stone The same transformer and containment is used as in the previous clause. The containment pit is designed so the stone thickness extends 0.15 m (6 in) above the maximum oil level. This will suppress combustion of oil in the containment. See 8.2. The anticipated flame front and spill fire size is reduced to the larger of the tank perimeter or the tank foundation perimeter. The perimeter of the flame front will be 4.3 m (14 ft) × 8.5 m (28 ft). The use of flame-suppressing stone can reduce the fire separation by 2.5 m (8 ft, 2 in) to 3.6 m (11 ft, 10 in). The flame-suppressing stone typically has a void volume of 30%, which decreases the effective liquid storage capacity by approximately 2/3. This will result in an increased spill containment size. If the containment size is too large, then consider the following: 

The use of an IEC system (pit with grating and a 15 cm [6 in] layer of stone).



Use a separate storage tank.



Use a “burn off” pit. A “burn off” pit would be located in an area where the oil can burn without jeopardizing adjacent equipment or structures.




E.2 Substation example

E.2.1 General This example illustrates some of the concepts presented in this guide and the methodology that the substation designers and other concerned individuals would follow in order to ensure that the substation is adequately protected from fire hazards.

E.2.2 Given information Figure B.2 shows a conceptual 230 kV ring bus connected to two 230 kV to 69 kV transformers and two 230 kV lines. The 69 kV switchyard is located 30 m (100 ft) from the 230 kV switchyard, and because this separation will provide adequate protection to its equipment, it will not be shown for simplicity. Its equipment will not be considered in the evaluation. The location of the substation was selected based on proximity to the 230 kV lines. No considerations are given to other factors such as the wind magnitude, surrounding area, and substation slopes. There are no water sources near the substation. The 230 kV ties into the main bulk power system for the area and the substation is important to the utility’s operation. The 69 kV from the substation ties into a regional power system that is highly reliable and redundant. The loss of the 69 kV supply would not impact the system reliability.

Figure E.2—Substation (partial) layout




Equipment information: 

69 kV Circuit breaker: The 69 kV circuit breakers are SF 6 type with polymer bushings and rated 2000 A, 650 kV BIL. No oil is used in these circuit breakers.



230 kV Circuit breaker: The 230 kV circuit breakers are SF6 type with polymer bushings and rated 2000 A, 900 kV BIL. No oil is used in these circuit breakers.



Control building: 15.2 m (50 ft) long × 9.1 m (30 ft) wide × 4.6 m (15 ft) high, metal with 2 h fire rating walls and ceiling; door locations are as shown.



Power transformer: Two 180 MVA, 230 kV through 69 kV transformers are used in the substation. Mineral oil is used in the tank, high-voltage bushings, and low-voltage bushings. The following information is given for the transformers.



Transformer data

Metric units

High-voltage bushing, height above base Low-voltage bushing, height above base Conservator tank, height above base Main tank oil volume Radiators oil volume Conservator oil volume Total oil volume

7.6 m 6.1 m 7.0 m 49 210 L 4540 L 1890 L 55 650 L

American system units 25 ft 20 ft 23 ft 13 000 gal 1200 gal 500 gal 14 700 gal

Transformer foundation and spill containment: The proposed layout is shown in Figure E.1. The containment wall is not the same distance from the transformer foundation on all sides. This often occurs due to physical constraints of the installation or to provide additional storage volume (extending the size may not be possible on all sides). In this case, the spill containment walls are 2.6 m (8 ft, 8 in) from the foundation on the short sides of the transformer and 3.8 m (12 ft, 4 in) from the long sides. Without stone in the containment, the flame front will extend to the edge of the walls. The perimeter size of the flame front will be 11.5 m (37 ft, 8 in) × 13.5 m (44 ft, 4 in) when the wall thickness of 15 cm (6 in) is taken into account. When evaluating fire separations, distances will be measured from the perimeter of the flame front or spill containment.



Station service transformer: Two station service power transformers are used. Both are pad mount, dry type, rated 12.47 kV to 480 V, 150 kVA.



Voltage transformer: Each of the volt age transformers contains 57 L (15 gal) of oil .



The substation area is graded with a 2% slope.

E.2.3 Fire sources in the substation The following is a list of the significant fire sources in the station: a)

The two power transformers (T1 and T2)

b)

Voltage transformers

c)

Station service transformers

d)

Switchyard maintenance activities

e)

1)

Hot work

2)

Oil treatment

Control building 1)

Control panels 72 Copyright © 2012 IEEE. All rights reserved.



2)

Heating system

3)

Smoking

4)

Refuse

5)

Hot work

The fire sources in the substation are summarized in Table E.1.

Table E.1—Fire sources Source Power transformer Voltage transformers (VTs) Station service transformers

Control building

Number of items 2 6 2 1 Multiple

Material Mineral oil Mineral oil Dry insulation Walls and roof Wire and cable

The power transformers are the most hazardous fire sources in the substation. The spacing of the transformers to each other and to the control building is critical and will be examined as follows.

E.2.4 Fire protection assessments

E.2.4.1 Switchyard fire protection assessment Items Comments Risk assessment — Electric equipment layout and equipment types. See Figure E.2. — Criticality of the various pieces of equipment. See E.2.2. — Insulating fluids used and their flammability. Mineral oil. — Historical frequency of fire for the various types — T1 and T2: f = 0.0006/year/unit. of equipment. — Station service transformer: f < 0.0001/year/unit. — Voltage transformer: f < 0.0001/year/unit. — Availability of a fire department response to the No response is available. site. — Availability of a firefighting water supply at or The closest water source is 500 m away. adjacent to the site. Radiant exposure assessment — Spacing between individual single-phase NA transformers and breakers. — Spacing between oil-insulated equipment such as See E.2.5 for a detailed analysis. three-phase transformers, banks of single-phase transformers, or groups of breakers. — Spacing of oil-insulated equipment with respect to See E.2.6 for details. buildings.

NOTE 1—The presence of combustib le surfaces and unprotected windows on exposed surfaces of the buildings may require detailed thermal radiation calculations or the application of safety factors to the table distances. The Society of Fire Protection Engineers Engineering Guide for Assessing Flame Radiation to External Targets from Pool Fires [B77] can be used as a reference for detailed thermal radiation calculations. — Distances between oil-insulated equipment and the property line.

The distance to the property line is not known, and the drawing does not give any indication of other properties.




Items

Comments

NOTE 2—Combustible vegetation and building structures beyond the property line of the substation may be exposed to high enough heat fluxes to ignite combustible surfaces. Detailed thermal radiation calculations should be considered. — Use of the various methods of fire protection discussed in this guide that will address the hazard determined in the radiant exposure assessment, such as changing the type of equipment and insulating fluid used, increased spacing, provision of gravel ground cover, oil-containment, fire barriers, and automatic water deluge fire protection. Fire spread assessment — Is the surface around oil-filled equipment pervious (gravel) or impervious? The use of 30 cm (12 in) thick crushed stone ground covers will suppress the flames from a burning oil spill fire. Impervious surfaces can allow the burning oil to form a large pool fire, which will i ncrease the heat flux t o adjacent equipment and structures. — Is there any oil-spill containment in place around the oil-filled equipment? — Does the grade surrounding the oil-filled equipment slope toward the equipment or away from the oilfilled equipment toward adjacent oil-filled equipment, cable trenches, drainage facilities, or buildings? The burning oil released from ruptured oil-filled equipment can spread for significant distances if the ground surrounding the equipment has a slope greater than 1%. — Review the use of the various methods of fire protection discussed in IEEE Std 979 that will address the hazard determined in the fire spread assessment. These methods include the following: 1) Changing the type of equipment and insulating fluid used 2) Increasing the spacing, use of gravel ground cover 3) Provision of oil containment 4) Changing the grade surrounding the equipment 5) Use of liquid-tight noncombustible cable trench cover adjacent to oil-filled equipment 6) Fire stopping of cable trenches entries into control buildings 7) The use of automatic water deluge fire protection

— Mineral-oil-insulating fluid used. — Equipment spacing as shown. — Ground cover assumed to be impervious with no stone. — Oil containment provided. — No fire barriers installed. — No water spray deluge installe d. Oil-spill containment is impervious and will support a spill fire.

Oil-spill containment is in place. Site slope is 2%, but oil-spill containment is used so this is not significant for fire protection.

— Mineral-oil-insulating fluid used. — Equipment spacing as shown. — Ground cover assumed to be impervious and no stone. — Oil-spill containment provided. — No fire barriers installed. — No water spray deluge installe d.




E.2.4.2 Control building fire protection assessment Item Life safety assessment — Review the control room layout to ensure that the room has a minimum of one outward swinging exit doors.

— Ensure that the travel distance from any area within the control building to an exit does not exceed 30 m (100 ft). — Ensure that exit signs are installed at each exit door. — Review that emergency lighting is provided that will provide a minimum lighting level of 10 lux at the floor, along the exit paths. — Review the size and number of stories of the building to ensure proper exits are provided to ensure that maximum travel distances to the exits do not exceed 30 m (100 ft). — Building or fire code requirements for the installation of a fire detection system. Fire protection assessment — Review the availability of a fire department response to the site. — Review the availability of firefighting water supply at or adjacent to the site. — Review the adequacy of any existing control building fire protection. — Review criticality of control building equipment, hazards involved, response time of station personnel, and the fire department.

Comments

The layout shows an outward swinging door and a large double equipment door. However, both doors are at one end of the control building. The large equipment doors are usually closed and secured with pins. Confirm the locations of the doors are at opposite ends of the building to provide shorter travel distances. Also ensure that all doors will not be secured such that they can still be used as an exit at all times. Travel distance is less than 30 m (100 ft).

No information on compliance. Yes.

One story.

None.

No fire department response. No water supply available. None is provided other than portabl e fire extinguishers. The control building is critical to the substation’s reliability. Early detection of fires is critical to prevent extensive damage. Fire detection is required, but fire suppression is considered too costly. Photoelectric smoke detectors will provide early detection of fires that typically occur in control buildings. The alarm will be sent to the utility’s control center to allow quick dispatching of staff and fire personnel.

— Determine the type of detection that will provide an acceptable, very early detection (air sampling detection) to detect a fire at a very early stage (small electronic component failure—arcing) or at an early stage with smoke detection (photoelectric detection) to detect a fire at a smoldering or small flame stage. — Determine the type of fire-suppression system that None provided. will provide acceptable equipment losses and outages (i.e., gaseous suppression systems to suppress a fire at an early stage [component loss] or sprinkler protection to suppress a fire at the stage where the loss would be restricted to a single control cabinet). — Review the occupied hours of the building and The control building is only occupied during station ability of site personnel to extinguish a fire safely checks and maintenance (typically 4 h per week). with portable fire equipment. Install two 10 lb fire extinguishers, rated ABC, one at — Determine the levels of portable fire equipment each exit door. A clean agent fire extinguishant with required by the local fire code and that is suitable for lower toxicity and zero ozone depletion may be safe staff operation. considered. Hazard assessment — Other uses (shops, offices, storage, etc.) within the No other uses are within the control bui lding. control building and their exposure to the critical substation equipment. — Combustible construction in the control building The control building is of noncombustible, 2 h rated (i.e., exterior surfaces and roofs). construction.




Item — Interior surface finishes in the control building.

Comments All interior surfaces have low flame spread. The interior walls are surfaced with 0.5 in drywall. Specific areas have 0.75 in plywood to allow mounting of equipment panels. All walls surfaces are painted with two coats of latex paint. — Combustibility of any exposed cable used in the Cables are routed in ventilated cable tray. Cables have a control building (ensure that it meets the FT1 rating in accordance with IEEE Std 1202-2006 requirements of IEEE Std 1202TM-2006 [B70]). [B70]. — Control building separation walls to other No other occupancies. occupancies to ensure that the walls have a fireresistance rating of a minimum of 1 h.

E.2.5 Transformer-to-transformer spacing

E.2.5.1 Based on prescriptive values From 7.2.2, the required separation between the anticipated transformer flame front and adjacent transformer is 15.2 m (50 ft). Because stone is not used in the spill containment, the anticipated flame front is the edge of the spill containment to the closest bushing of the adjacent transformer. The distance to the closest bushing is chosen because the bushing will typically be damaged first. 

T1 fire: The minimum distance between the edge of the T1 spill containment to the closest part of the T2 is 16.95 m as detailed below: Distance

Metric units

T1 spill containment wall thickness Distance between outside edges of the T1 and T2 spill containments Distance between the T2 oil containment and its tank Distance between the T2 tank and the nearest bushing Total separation between anticipated T1 flame front and T2 

0.15 m

American system units 6 in

13.8 m

45 ft, 3 5/8 in

2.6 m

8 ft, 8 in

0.35 m

1 ft, 2 in

16.95 m

55 ft, 7 5/8 in

T2 fire: In this case, the transformers are symmetrical so the distances are the same as for T1>T2 or 16.95 m.

The distance between transformers is 16.95 m, whereas the prescriptive distance is 15.2 m. The proposed layout meets the prescriptive spacing requirements for T1 and T2.

E.2.5.2 Heat flux calculations These calculations are based on two fire scenarios of a bushing failure and core failure. The assumptions used for the calculations are as follo ws: 

Mineral oil insulating fluid is used.



Transformers are conservator pressurized, not gas pressurized.



Transformer bushings are porcelain.



Transformer tank is 4.9 m (16 ft) high and the top is flat. 76 Copyright © 2012 IEEE. All rights reserved.





Flame-suppressing stone is not used in the spill containment.



Transformer pad size is the same as the transformer tank.



Transformer pad height is higher than the top of the containment walls.

Calculations follow. Refer to Chapter 5 of the NUREG documentation for details of the calculations. See B.1 for references to this document. a)

Fire spill size 1)

Bushing failure area ( AB) i)

A common scenario is to take the fire area to be the area of the top of the transformer tank plus the area of the spill containment. — Tank and containment area:

13.5 m × 11.5 m = 155.3 m2 (44 ft, 4 in × 37 ft, 8 in = 1670 ft2)

ii) Alternatively, using the scenario proposed in CEATI Report No. 1023700-3022 [B52], the area of the fire is based on the area of the top of the transformer tank, half the area of the sides, and the area of the spill containment. This scenario gives a worst-case result. NOTE—The dimensions of the spill containment are reduced to account for a wall thickness of 15 cm (6 in).

— Tank and containment area:

13.5 m × 11.5 m = 155.3 m2 (44 ft 4 in × 37 ft 8 in = 1670 ft2)

— Area of half the tank height: 4.9 m / 2 × (2 × 8.5 m + 2 × 4.3 m) 2 = 62.7 m (16 ft ÷ 2 × (2 × 28 ft + 2 × 14 ft) = 672 ft2) — Total fire area: 2)

155.3 m2 + 62.7 m2 = 218.0 m2 (1670 ft2 + 672 ft2 = 2342 ft2)

Tank failure fire area ( AT) A tank failure will cause the area between the transformer foundation and the containment walls to become the possible spill area because stone is not used in the containment. — Tank and containment area:

13.5 m × 11.5 m = 155.3 m2 (44 ft 4 in × 37 ft 8 in = 1670 ft2)

— Tank area:

8.5 m × 4.3 m = 36.6 m2 (28 ft × 14 ft = 392 ft2)

— Fire area:

155.3 m2 – 36.6 m2 = 118.7 m2 (1670 ft2 – 392 ft2 = 1278 ft2)

Summary of fire areas: 2

Scenario Bushing failure (i) Bushing failure (ii) Tank failure

b)

Fire area (m ) 155.3 218.0 118.7

Pool fire radius: In this case, the pool will be noncircular. Assume a circle with the same area as the pool fire. 

Bushing (i):

r Bi= ( A/π)0.5 = (155.3/π)0.5 = 7.0 m




c)



Bushing (ii):

r Bii= ( A/π)0.5 = (218/π)0.5 = 8.3 m



Tank:

r T= ( A/π)0.5 = (118.7/π)0.5 = 6.1 m

Heat release rate (MW) using Equation 5-2 of NUREG: Q = m″∆ H c A(1 – e –k β D) Variable

Description

Value

m″

Mass loss rate for mineral oil per Table 3-1.2 in SFPE or NUREG spreadsheet

0.039 kg/m2s

∆ H c

Net heat of combustion per Table 3-1.2 in SFPE or NUREG spreadsheet

46.4 MJ/kg

A

Area of pool fire (m2)

Bushing (i): 155.3 m2 Bushing (ii): 218.0 m2 Tank: 118.7 m2

k β

Empirical constant (m –1)

0.7 m –1

Diameter of burning area (m)

Bushing (i): 14.0 m Bushing (ii): 16.6 m Tank (i): 12.2 m

D

— Bushing (i):

Q = 46.4 × 0.039 × 155.3 × (1 – e –(0.7)(14)) = 280.9 MW Q = 280 900 kW

— Bushing (ii):

Q = 46.4 × 0.039 × 218 × (1 – e –(0.7)(16.6)) = 393.4 MW Q = 393 400 kW

— Tank:

Q = 46.4 × 0.039 × 118.7 × (1 – e –(0.7)(16.6)) = 214.8 MW Q = 214 800 kW

NOTE—The c alculations can be been simplified in most cases by setting the factor (1 – e – k β D) to 1.

d)

Distance between pool fire and target — Bushing of adjacent transformer: This distance was calculated in E.2.5.1, LB = 16.95 m — Tank of adjacent transformer: This distance will be the same as the previous value less the distance between the tank and bushing (0.35 m), LT = 16.95 – 0.35 = 16.6 m

e)

Heat flux (kW/m2) at bushing target using Equation 5-1 of NUREG: q”= X r Q/(4π R2)

Variable X r Q

Description Fraction of total energy radiated Heat release rate (kW)

R

Distance from the center of the fire to the edge of the target (r + LB)(m)

— Bushing (i): — Bushing (ii): — Tank:

Value 0.3 Bushing (i): 280 900 kW Bushing (ii): 393 400 kW Tank: 214 800 kW Bushing (i): 7.0 + 16.95 m Bushing (ii): 8.3 + 16.95 m Tank: 6.1 + 16.95 m

= (0.3 × 280 900)/(4π (7.0 + 16.95)2) = 11.7 kW/m2 = (0.3 × 393 400)/(4π (8.3 + 16.95)2) = 14.7 kW/m2 = (0.3 × 214 800)/(4π (6.1 + 16.95)2) = 9.6 kW/m2

The SFPE Handbook of Fire Protection Engineering [B79] recommends multiplying the calculated heat flux by a factor of two to account for variations between calculated and actual values. The heat flux can then be taken to be within these ranges.




— Bushing (i): — Bushing (ii): — Tank:

= 11.7 kW/m2 to 23.4 kW/m2 = 14.7 kW/m2 to 29.4 kW/m2 = 9.6 kW/m2 to 19.2 kW/m2

Heat flux (kW/m2) at tank target using Equation 5-1 from NUREG.

f)

The calculations will be identical to those in the previous subclause except LT is used instead of LB. — Bushing (i): = (0.3 × 280 900)/(4π(7.0 + 16.6)2) = 12.0 kW/m2 — Bushing (ii): = (0.3 × 393 400)/(4π(8.3 + 16.6)2) = 15.2 kW/m2 — Tank: = (0.3 × 214 800)/(4π(6.1 + 16.6)2) = 9.9 kW/m2 Doubling the values to include the recommended safety factor gives the following range: — Bushing (i): — Bushing (ii): — Tank: g)

= 12.0 kW/m2 to 24.0 kW/m2 = 15.2 kW/m2 to 30.4 kW/m2 = 9.9 kW/m2 to 19.8 kW/m2

Critical heat flux per Table B.3 for bushing damage — Bushing damage = 5 kW/m2 The separation is acceptable if the estimated heat flux at the target is below the critical heat flux of the target. The minimum heat flux (9.6 kW/m2) for either a bushing or tank fire is about 90% higher than the critical heat flux for bushings (5 kW/m 2). Being that the heat fluxes are so much higher than the critical heat flux, there is a significant risk of bushing damage to an adjacent transformer. Therefore, the separation does not provide adequate protection to the bushings of an adjacent transformer.

h)

Critical heat flux per Table B.3 for tank damage — Tank damage = 35 kW/m2

The maximum heat flux (30.4 kW/m2) of either a bushing or tank fire is about 13% lower than the critical heat flux for a tank (35 kW/m2). This means that the separation provides adequate protection to the tank of an adjacent transformer even with the safety factor. The spacing as designed does not meet the requirements based on the heat flux calculations. The designer might consider changing the type of insulating fluid, increasing the spacing between transformers, adding stone to the oil containment (effectively increasing the spacing), or providing a fire barrier.

E.2.6 Transformer to control building spacing

E.2.6.1 Prescriptive spacing The control building location was chosen with the following considered: 

Central within site to minimize cable lengths



Accessibility to control building for vehicles



Accessibility to equipment for maintenance

The edge of the anticipated transformer flame front for either a bushing fire or tank fire is the edge of the spill containment. The minimum distance to the control building for a T1 fire follows.




Distance

Metric units

T1 spill containment wall thickness Distance between outside edges of the T1 spill containment and the control building (see Figure E.2) Total separation between anticipated T1 flame front and the control building

0.15 m

American system units 0 ft, 6 in

12.68 m

41 ft, 7 11/32 in

12.8 m

42 ft, 1 11/32 in

From 7.2.3, the transformers need to be separated from the control building by a 2 h fire-rated wall. Because the control building has 2 h fire-rated walls, the spacing as proposed is suitable.

E.2.6.2 Heat flux calculations These calculations are based on two scenarios of a bushing failure or a tank failure with both resulting in a fire. The following assumptions are used for the calculations: 

Mineral-oil-insulating fluid is used.



The transformers are conservator pressurized, not gas pressurized.



The transformer bushings are porcelain.



The transformer tank top is flat.



No flame-suppressing stone has been installed in the oil-spill containment.

The calculations follow the same process as those in E.2.5.2 and use many of the same values. For this example, the NUREG spreadsheet without wind (see B.1) will be used to complete the calculations. The values used and results are summarized in Table E.2.

Table E.2—Summary of heat flux calculations Type of fire

Bushing (i) Bushing (ii) Tank

Spill area per part a) of E.2.5.2 2 2 [m (ft )] 155.3 (1670) 218.0 (2342) 118.7 (1278)

Distance from fire to target; see E.2.6.1 [m (ft)]

Radiant heat flux at the target 2 (kW/m )

12.8 (42.11) 12.8 (42.11) 12.8 (42.22)

16.8 20.8 14.1

Radiant heat flux at the target with safety factor 2 (kW/m ) 33.8 41.6 28.2

The critical heat flux for the control building is 30 kW/m2 per Table B.3 (unprotected metal). Without the safety factor, the heat flux at the control building for either a bushing or a tank fire is below the critical heat flux for unprotected metal. When the safety factor is considered, the heat flux at the control building for either a bushing or a tank fire is near or above the critical heat flux for unprotected metal. Because the exterior wall of the control building has a 2 h rating, the control building wall will be able to withstand the fire exposure for approximately 2 h. Although acceptable as is, adding flame suppression stone in the spill containment will reduce the heat flux at the control building.

E.2.7 Transformer to property line spacing The distance of the right transformer to the right property line is approximately 20 m (66 ft). For this example, the NUREG spreadsheet without wind (see B.1) will be used to complete the calculations. The values used and results are summarized in Table E.3.




Table E.3—Summary of heat flux calculations Type of fire

Bushing (i) Bushing (ii) Tank

Spill area per part a) of E.2.5.2 [m2 (ft2)] 155.3 (1670) 218.0 (2342) 118.7 (1278)

Distance from fire to target [m (ft)]

Radiant heat flux at the target 2 (kW/m )

20 (66) 20 (66) 20 (66)

9.0 11.5 7.4

Bushing (ii) fire is considered an extreme case and will not be considered. Assuming a fire were to occur in the right-hand side transformer, the radiant heat flux at the right property line would be 7.4 kW/m2 to 9.0 kW/m2. Table 5.3.3.2 of NFPA 59A [B73] recommends maximum heat flux levels at the property line. Assuming there is a building at or near the property line at the time the substation is built, the maximum heat flux exposure recommendation is 9 kW/m2. The heat flux at the property line for Bushing (i) and Tank fires does not exceed the recommendation and the spacing could be considered acceptable. The heat flux could be reduced by increasing the distance, installing a fire barrier, reducing the spill fire size, changing the insulating fluid, or installing fire protection.

E.2.8 Power transformers to adjacent equipment The cost, importance, and difficulty to replace should be considered when evaluating the location of adjacent equipment. The closest equipment to the transformers is the 230 kV circuit breakers. The minimum separation distance between the flame front and the circuit breaker is 10.9 m (35.8 ft). In accordance with 7.2.6, the minimum recommended separation distance for a transformer with oil containment is 10.7 m (35 ft). The spacing is acceptable. Bus support structures, surge arresters, and disconnect switches are relatively easy to replace and “low cost” compared to “major” equipment like transformers and circuit breakers. Also, to achieve the required separation distances for this type of equipment would typically increase the size and therefore the cost of a substation. For these reasons, the separation distances in 7.2.6 are typically considered optional for this type of equipment.

E.2.9 Station service transformers location There is no spacing requirement for equipment with less than 1890 L (500 gal) of oil. Footnote a of Table 1 provides some items for consideration by the designer. The transformers are located adjacent to each other and the control building. A minimum spacing of 1 m (3.3 ft) is considered adequate given the transformers do not have oil, there is a low fire risk, and the control building has 2 h fire-rated walls. The spacing as planned is acceptable.




E.2.10 Oil containment volume Each transformer has spill containment. The required spill containment volume is 110% of the oil from one transformer. a)

Spill containment volume NOTE—The dimensions of the spill containment are reduced to account for a wall thickness of 15 cm (6 in).

b)

— Containment perimeter area:

13.5 m × 11.5 m = 155.3 m2 (44 ft, 4 in × 37 ft, 8 in = 1670 ft2)

— Tank area:

8.5 m × 4.3 m = 36.6 m2 (28 ft × 14 ft = 392 ft2)

— Effective containment area:

155.3 m2 – 36.6 m2 = 118.7 m2 (1670 ft2 – 392 ft2 = 1278 ft2)

— Containment volume:

118.7 m2 × 0.6m = 71.2 m3 (1278 ft2 × 2.0 ft = 2556 ft3)

Required storage volume 

Total oil volume of one transformer:

55 650 L (14 700 gal) = 55.7 m3



Required spill containment volume:

55.7 × 1.1 = 61.3 m3

The spill containment has 116% of the required storage volume and meets the requirements for this design.

E.2.11 Other considerations

E.2.11.1 Gate location Entrance gates should be located at opposite ends of the site and away from high-fire-risk equipment and transmission and distribution lines. The most realistic locations would be in the lower left and right corners of the site against the road and as shown in Figure E.2.

E.2.11.2 Surface grade The slope for this substation is not critical because the two large power transformers have suitable oil-spill containment. The volume of oil in the VTs is small and is not a significant fire hazard.

E.2.11.3 Fire stops Fire stops should be installed in the trench at the highway-rated trench cover and at the penetrations into the control building. This will stop fires from spreading in the trench between the 69 kV and 230 kV switchyards and a trench fire from spreading into the control building.

E.2.11.4 Water supply There is no nearby water supply and there is no fire department that serves the area. Both of these create a major risk. The following are some options that could be considered to reduce this risk:




a)

Arrange mutual aid with a local airport to have a crash rescue truck respond.

b)

Have a least two 125 L (33 gal) AFFF wheeled units and three 160 kg (350 lb) dry chemical wheeled units, and have the responding crews trained in their use.

c)

Arrange mutual aid with a local fire department to respond with tankers and provide firefighting foam.

d)

Arrange mutual aid with forest firefighting organizations to provide tanker and firefighting crews under the direction of the station crews.

e)

Install flame-suppressing stone in the spill containment or use an IEC style grate and gravel system.




Annex F (informative) Bibliography Bibliographical references are resources that provide additional or helpful material but do not need to be understood or used to implement this standard. Reference to these resources is made for informational use only. [B1] Accredited Standards Committee C-2, National Electrical Safety Code® (NESC®). [B2] AICHE Guidelines for Chemical Process Quantitative Risk Analysis.14 [B3] ANSI/IEEE Std 383-1974, IEEE Standard for Type Test of Class 1E Electric Cables, Field Splices, and Connections for Nuclear Power Generating Stations. [B4] ANSI/IEEE 518-1982, IEEE Guide for the Installation of Electrical Equipment to Minimize Electrical Noise Inputs to Controllers from External Sources. [B5] ANSI/IEEE 525-1992, IEEE Guide for the Design and Installation of Cable Systems in Substations. [B6] ANSI/IEEE 634-2004, IEEE Standard Cable Penetration Fire Stop Qualification Test. [B7] ANSI/NFPA 10-2012, Standard for Portable Fire Extinguishers.15,16 [B8] ANSI/NFPA 11-2010, Standard for Low-, Medium-, and High-Expansion Foam. [B9] ANSI/NFPA 11A-1999, Standard for Medium- and H igh-Expansion Foam Systems. [B10] ANSI/NFPA 11C-1995, Standard for Mobile Foam A pparatus. [B11] ANSI/NFPA 12-2011, Standard on Carbon Dioxide Extinguishing Systems. [B12] ANSI/NFPA 12A-2009, Standard on Halon 1301 Fire Extinguishing Systems. [B13] ANSI/NFPA 12B-1990, Standard on Halon 1211 Fire Extinguishing Systems. [B14] ANSI/NFPA 13-2011, Standard for the Installation of Sprinkler Systems. [B15] ANSI/NFPA 14-2010, Standard for the Installation of Standpipe and Hose Systems. [B16] ANSI/NFPA 15-2012, Standard for Water Spray Fixed Systems for Fire Protection. [B17] ANSI/NFPA 16-2011, Standard for the Installation of Foam-Water Sprinkler and Foam-Water Spray Systems. [B18] ANSI/NFPA 17-2009, Standard for Dry Chemical Extinguishing Systems. [B19] ANSI/NFPA 20-2011, Standard for the Installation of Stationary Pumps for Fire Protection. [B20] ANSI/NFPA 22-2012, Standard for Water Tanks for Private Fire Protection. [B21] ANSI/NFPA 24-2013, Standard for the Installation of Private Fire Service Mains and Their Appurtenances. [B22] ANSI/NFPA 25-2011, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems. [B23] ANSI/NFPA 30-2011, Flammable and Combustible Liquids Code.

14

AIChE publications are available from the American Institute of Chemical Engineers (http://www.aiche.org/). ANSI publications are available from the American National Standards Institute (http://www.ansi.org/). 16 NFPA publications are available from the National Fire Protection Association (http://www.nfpa.org/). 15




[B24] ANSI/NFPA 37-2009, Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines. [B25] ANSI/NFPA 58-2012, Liquefied Petroleum Gas Code. [B26] ANSI/NFPA 68-1998, Guide for Venting of Deflagrations. [B27] ANSI/NFPA 70E-2012, Standard for Electrical Safety in the Workplace. [B28] ANSI/NFPA 72-2010, National Fire Alarm and Signaling Code. [B29] ANSI/NFPA 80-2013, Standard for Fire Doors and Other Opening Protectives. [B30] ANSI/NFPA 80A-2012, Recommended Practice for Protection of Buildings from Exterior Fire Exposures. [B31] ANSI/NFPA 90A-2012, Standard for the Installation of Air Conditioning and Ventilating Systems. [B32] ANSI/NFPA 90B-2012, Standard for the Installation of Warm Air Heating and Air-Conditioning Systems. [B33] ANSI/NFPA 92A-2009, Standard For Smoke-Control Systems Utilizing Barriers and Pressure Differences. [B34] ANSI/NFPA 101-2011, Life Safety Code. [B35] ANSI/NFPA 101A-2010, Guide on Alternative Approaches to Life Safety. [B36] ANSI/NFPA 204M-1991, Guide for Smoke and Heat Venting. [B37] ANSI/NFPA 255-2006, Standard Method of Test of Surface Burning Characteristics of Building Materials. [B38] ANSI/NFPA 256-2003, Standard Methods of Fire Tests of Roof Coverings. [B39] ANSI/NFPA 450-2013, Guide for Emergency Medical Services and Systems. [B40] ANSI/NFPA 550-2012, Guide to the Fire Safety Concepts Tree. [B41] ANSI/NFPA 750-2010, Standard on Water Mist Fire Protection Systems. [B42] ANSI/NFPA 780-2011, Standard for the Installation of Lightning Protection Systems. [B43] ANSI/NFPA 1142-2012, Standard on Water Supplies for Suburban and Rural Fire Fighting. [B44] ANSI/NFPA 1144-2013, Standard for Reducing Structure Igniti on Hazards from Wildland Fire. [B45] ANSI/NFPA 2001-2012, Standard on Clean Agent Fire Extinguishing Systems. [B46] ANSI/NFPA Industrial Fire Hazards Handbook , 3rd ed. [B47] ASTM D5222-2008, Standard Specification for High Fire-Point Mineral Electrical Insulating Oils. 17 [B48] ASTM E-84-81a-2000, Standard Test Method for Surface Burning Characteristics of Building Materials. [B49] Australian Building Codes Board, Fire Safety Engineering Guidelines. Canberra, Australia: Australian Building Codes Board, 2001. [B50] Berry, T. F., Risk-Informed, Performance-Based Industrial Fire Protection: An Alternative to Prescriptive Codes, 1st ed. Tennessee Valley Publishers, 2002. [B51] British Standards Institute, DD 240-1:1997, Fire safety engineering in buildings—Guide to the application of fire safety engineering principles. [B52] CEATI International Inc., Report No.T023700-3022, Transmission Stations and Transformers—Fire Protection and Prevention, August 2005.18 17

ASTM publications are available from the American Society for Testing and Materials (http://www.astm.org/).




[B53] CFR (Code of Federal Regulations), Title 40 (Environmental Protection Agency), Part 300 (1988 Revision).19 [B54] CIGRE TF 14.01.04-1999, Report on Fire Aspects of HVDC Valves and Valve Halls. [B55] Cote, A. E., J. L. Linville, and NFPA, Fire Protection Handbook, MY-FPH 1791, 17th ed. Norwood, MA: National Fire Protection Association (NFPA), 1991. [B56] EPRI TR-100443-1992, Methods of Quantitative Fire Hazard A nalysis. [B57] FM Data Sheet 5-4, Recommended Good Practice for Transformer and Switchgear Installations, July 2012. [B58] FM Data Sheet 5-19, Loss Prevention, Switchgear and Circuit Breakers, Jan. 2006. [B59] FM Data Sheet 5-31, Loss Prevention, Cable and Bus Bar, Apr. 2012. [B60] IEC 61936-1-2011, Power Installations Exceeding 1 kV a.c.—Part 1: Common Rules.20 [B61] IEEE Std C37.90.1TM-2002, IEEE Standard for Surge Withstand Capability (SWC) Tests for Relays and Relay Systems Associated with Electric Power Apparatus.21, 22 [B62] IEEE Std C37.122.1TM-1993, IEEE Guide for Gas-Insulated Substations. [B63] IEEE Std C62.41TM-1991, IEEE Recommended Practice on Surge Voltages in Low-Voltage AC Power Circuits. [B64] IEEE Std 80TM-2000, IEEE Guide for Safety in AC Substation Grounding. [B65] IEEE Std 384TM-2008, IEEE Standard Criteria for Independence of Class 1E Equipment and Circuits. [B66] IEEE Std 420TM-2001, IEEE Standard for the Design and Qualification of Class 1E Control Boards, Panels, and Racks Used in Nuclear Power Generating Stations. [B67] IEEE Std 484TM-2002, IEEE Recommended Practice for Installation Design and Installation of Vented Lead-Acid Batteries for Stationary Applications. [B68] IEEE Std 817TM-1993, IEEE Standard Test Procedure for Flame-Retardant Coatings Applied to Insulated Cables in Cable Trays. [B69] IEEE Std 998TM-1996, Guide for Direct Lightning Stroke Shielding of Substations. [B70] IEEE Std 1202TM-2006, IEEE Standard for Flame-Propagation Testing of Wire and Cable. [B71] ISO 23932-2009, Fire Safety Engineering—General Principles. 23 [B72] JEAG 4607-1999, Guidelines for Fire Protection of Nuclear Power Plants.24 [B73] NBC 2010, National Building Code of Canada (objective-based).25 [B74] NFPA 59A-2012, Standard For The Production, Storage, and Handling of Liquefied Natural Gas (LNG). [B75] NFPA 70, National Electrical Code® (NEC®).

18

Material is reprinted in this guide with the permission of CEATI and the support of Hydro One Networks Inc. CEATI publications are available from CEATI International (http://www.ceati.com/). 19 CFR publications are available from the U.S. Government Printing Office (http://www.gpo.gov/). 20 IEC publications are available from the International Electrotechnical Commission (http://www.iec.ch/). IEC publications are also available in the United States from the American National Standards Institute (http://www.ansi.org/). 21 The IEEE standards or products referred to in this clause are trademarks of The Institute of Electrical and Electronics Engineers, Inc. 22 IEEE publications are available from The Institute of Electrical and Electronics Engineers ( http://standards.ieee.org/). 23 ISO publications are available from the ISO Central Secretariat (http://www.iso.org/). ISO publications are also available in the United States from the American National Standards Institute (http://www.ansi.org/). 24 JEAG publications are available from the Japan Electric Association (http://www.denki.or.jp/pub/jeacjeag.html/). 25 NBC documents are available from the Government of Canada (http://www.nationalcodes.nrc.gc.ca).



IEEE Std 979-2012, IEEE Guide for Substation Fire Protection

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