Power Quality Theory and Application. To explain the power quality in the electrical system.
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Descrição: Electric Power Distribution Reliability
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In a powers system network there are many problems related to power quality. So to improve power quality of a system we use different devices such as active power filters. Active power filters are classified into two types that is Shunt Active Power
MHEC : LOSS CONTROL WORKSHOP Electric Power Quality
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Our Roadmap for this PQ Session • To arm you with some useful power quality design recommendations and ideas • Illustrate Power Quality solutions using case studies • Industry Trends • Questions and Answers 2
What is Power Quality? • “The concept of powering and grounding sensitive equipment in a manner that is suitable to the operation of that equipment.”1 • “Within the industry, alternate definitions or interpretations of power quality have been used, reflecting different points of view.”2 • The definition of Power Quality cannot be limited to the characteristics of the supply power. The definition must also include the requirements of the load. 11
IEEE 1100-1992 22 IEEE 1159-1995
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Power Quality Paradigms
Key Services/Technologies in the “Power Quality” Industry 4
Industry Trends
Demand for Clean Power Fueled by 225% Growth in Microprocessors • Increased sensitivity to disturbances and poor grounding • Effects of harmonics on distribution systems • Increased problems from natural phenomenon 5
Industry Trends
Growth in Electronics = Growth in PQ Solutions
Power Quality Solutions/Electronic Loads
Surge Suppressors Power-Conditioning Equipment Electronic Ballasts Variable Speed Drives Energy Efficient Motors Solid-State Motor Controls Programmable Logic Controls Voice/Data Cable System Power-Monitoring System 00 10 10 20 20 30 30 40 40 50 50 60 60 70 70
EC&M Reader Survey (1995) 6
Power Quality Solution Strategy Good Grounding Practices Harmonic Solutions
Surge Solutions
Voltage Variation Solutions
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Power Quality Design and Application Considerations • Ensure grounding system integrity • Limit creation of power quality problems • Attenuate power quality problems • Withstand poor power quality
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Grounding
Equipment Grounding • Related to Over Half • Foundation of a of All Power Quality reliable electrical Problems distribution system • Proliferation of communication and computer network systems
Good Grounding Practices Harmonic Solutions
Surge Solutions
Voltage Variation Solutions
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Grounding
Equipment Grounding • Reasons for grounding • Personnel safety • Equipment protection • Power quality
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Grounding
Equipment Grounding and Power Quality • National Electrical Code Article 250 also provides the baseline requirements to ensure proper operation of sensitive equipment • FIPS 94 provides additional methods that are typically needed to ensure reliable operation of electronic equipment 11
Grounding
Equipment Grounding National Electrical Code Article 250 provides requirements for personnel safety and equipment protection “Who omitted the safety equipment ground?” L N Improper omission of safety equipment ground conductor
12
Grounding
Equipment Grounding and Power Quality
Separate the inherent noise from communication signals • Avoid creating ground loops in the conductors that connect the frames of functional components • Minimize the influence or radiation of radio frequency noise • Provide a low impedance path to ground for noise 13
Grounding
Electronic Equipment Grounding Tip
Desktop Computer
• A ground loop creates noise because unwanted current flows in the conductors of a communications cable
GND N 120
Communications Cable
Server
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Grounding
Electronic Equipment Grounding Tip
Desktop Computer Desktop Computer
• A balun is a coiled extension cord that creates an impedance in the ground loop, reducing loop current
Balun Balun
GND N 120
Communications Cable
Server Server
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Harmonic Distortion • Harmonic problems are becoming more apparent because more equipment that produce harmonics Good Grounding are being Practices applied Surge Harmonic Solutions Solutions to power Voltage Variation Solutions systems
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Harmonics
Harmonic Distortion Harmonics Harmonics are are multiples multiples of of the the fundamental fundamental frequency frequency
++ f(x) = sin(x)
== f(x) =
sin(5x) 5
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sin(5x) f(x) = sin(x) + 5 When When added added together together result result in in aa distorted distorted waveform waveform
Harmonics
Harmonic Frequencies
• Harmonics are low frequency waveform distortions (< 1kHz) • Transients are higher frequency events (between 1 kHz and 1 MHz) • Above 1MHz, the wires become transmitters and radiate the noise at this frequency Surges Surges and and Noise Noise Harmonic Harmonic Disturbance Disturbance
50/60Hz kHz 50/60Hz 11 kHz
Transmitted Transmitted Radio Radio Frequency Frequency
11 MHz MHz
Frequency Frequency 100 100 MHz MHz
Source: Source: Dranetz Dranetz Handbook Handbook for for Power Power Quality Quality Analysis Analysis 18
Harmonics
Sources of Harmonics • Harmonics are produced by the operation of nonlinear loads • General categories and common types of nonlinear loads are – Power electronic equipment – Arcing devices – Iron saturating devices – Rotating machines 19
Harmonics
Sources of Harmonics Amps
Variable Frequency Drive
Fluorescent Lighting Amps
480V
480V - 3-Phase 480V Circuit #1
277V - 1-Phase
THD = 15% Switch Mode - PCs Amps
Amps 480V Secondary Amps
THD = 7%
THD = 104% THD = 9% Neutral 120V Current Amps
480V Primary Amps
120V - 1-Phase
120V - Neutral Source: IEEE 11001100-1992
THD = 30%
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Harmonics
Common Symptoms of Harmonics
Harmonic voltage and current distortion cause: • Heating caused by higher frequency current components • Insulation stress caused by higher frequency voltage components • Circuit malfunction caused by voltage distortion 21
Harmonics
Common Symptoms of Harmonics
Specific symptoms include: • Transformer heating • Motor and generator heating and vibrations • Neutral heating • Nuisance fuse operations • Insulation deterioration • Electronic control malfunctioning • Inconsistent meter readings • Voltage regulator misoperations 22
Harmonics
Harmonic Distortion Standards
Harmonic Voltage Distortion Limits IEEE Standard 519 – 1992
Maximum Voltage Distortion in % at PCC* Below 69kV
69-138kV
>138kV
Maximum for Individual Harmonic
3.0
1.5
1.0
Total Harmonic Distortion (THD)
5.0
1.5
1.5
* % of Nominal Fundamental Frequency Voltage 23
Harmonics
Harmonic Distortion Standards
Maximum Harmonic Current Distortion IEEE Standard 519 – 1992 Harmonic Order (Odd Harmonics) /I Isc sc LL
Harmonic Design Tip • Harmonic cancellation makes use of transformer connections and phase shifting to cancel harmonics generated from various sources 27
Y Y
Multi-Cycle Voltage Variations • Sags are responsible for a majority of upsets and nuisance trips of sensitive electrical equipment Good Grounding Practices Harmonic Solutions
Surge Solutions
Voltage Voltage Variation Variation Solutions Solutions
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Voltage
Voltage Variations • Sag – a decrease in RMS voltage lasting from a half-cycle to a few seconds
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Voltage
Voltage Variations • Interruption – complete loss of voltage
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Voltage
Voltage Variations • Overvoltage – an RMS increase in voltage lasting more than a few seconds
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Voltage
Voltage Variation Symptoms • Sag – Substandard product – Process interruption • Interruption – Complete loss of power • Overvoltage – Equipment damage 32
Voltage
Voltage Variation Sources • Supply side variations • Short circuits • Capacitor switching • Load switching • Regulator malfunction • Load side variations • Motor starting 33
