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MHEC : LOSS CONTROL WORKSHOP

MHEC : LOSS CONTROL WORKSHOP

Electric Power Quality Electric Power Quality

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Our Roadmap for this PQ SessionOur 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

• To arm you with some useful power quality design recommendations and ideas • Illustrate Power Quality solutions using

case studies• Industry Trends•Questions and Answers

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What is Power Quality?What is Power Quality?

1 IEEE 1100-19922 IEEE 1159-19951 IEEE 1100-19922 IEEE 1159-1995

• “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.

• “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.

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Power Quality ParadigmsPower Quality Paradigms

Key Services/Technologiesin the “Power Quality” Industry

Key Services/Technologiesin the “Power Quality” Industry

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Industry TrendsIndustry TrendsDemand for Clean Power Fueled by 225% Growth in MicroprocessorsDemand 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

• Increased sensitivity to disturbances and poor grounding •Effects of harmonics on distribution systems• Increased problems from natural phenomenon

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Power Quality Solutions/Electronic LoadsPower Quality Solutions/Electronic Loads

Growth in Electronics = Growth in PQ SolutionsGrowth in Electronics = Growth in PQ Solutions

Industry TrendsIndustry Trends

EC&M Reader Survey (1995)EC&M Reader Survey (1995) 0 10 20 30 40 50 60 700 10 20 30 40 50 60 70

Surge SuppressorsPower-Conditioning Equipment

Electronic BallastsVariable Speed Drives

Energy Efficient MotorsSolid-State Motor Controls

Programmable Logic ControlsVoice/Data Cable System

Power-Monitoring System

Surge SuppressorsPower-Conditioning Equipment

Electronic BallastsVariable Speed Drives

Energy Efficient MotorsSolid-State Motor Controls

Programmable Logic ControlsVoice/Data Cable System

Power-Monitoring System

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Power QualitySolution StrategyPower QualitySolution Strategy

GoodGroundingPractices

SurgeSolutions

HarmonicSolutions

VoltageVariation Solutions

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Power Quality Design and Application ConsiderationsPower Quality Design and Application Considerations•Ensure grounding system integrity•Limit creation of power quality problems•Attenuate power quality problems•Withstand poor power quality

•Ensure grounding system integrity•Limit creation of power quality problems•Attenuate power quality problems•Withstand poor power quality

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Equipment GroundingEquipment GroundingGroundingGrounding

• Foundation of a reliable electrical distribution system• Proliferation of

communication and computer network systems

• Foundation of a reliable electrical distribution system• Proliferation of

communication and computer network systems

• Related to Over Half of All Power Quality Problems

• Related to Over Half of All Power Quality Problems

GoodGroundingPractices

GoodGroundingPractices

SurgeSolutions

HarmonicSolutions

VoltageVariation Solutions

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Equipment GroundingEquipment GroundingGroundingGrounding

•Reasons for grounding•Personnel safety•Equipment protection•Power quality

•Reasons for grounding•Personnel safety•Equipment protection•Power quality

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Equipment Groundingand Power QualityEquipment Groundingand Power Quality

GroundingGrounding

• National Electrical Code Article 250 also provides the baseline require-ments to ensure proper operation of sensitive equipment• FIPS 94 provides additional methods

that are typically needed to ensure reliable operation of electronic equipment

• National Electrical Code Article 250 also provides the baseline require-ments to ensure proper operation of sensitive equipment• FIPS 94 provides additional methods

that are typically needed to ensure reliable operation of electronic equipment

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GroundingGroundingEquipment GroundingEquipment GroundingNational Electrical Code Article 250 provides require-ments for personnel safety and equipment protectionNational Electrical Code Article 250 provides require-ments for personnel safety and equipment protection

LN

Improper omission of safety

equipment ground conductor

“Who omitted the safety equipment

ground?”

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GroundingGroundingEquipment Groundingand Power QualityEquipment Groundingand Power QualitySeparate the inherent noise from communication signalsSeparate 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

• 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

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Electronic Equipment Grounding TipElectronic Equipment Grounding Tip

GroundingGrounding

• A ground loop creates noise because unwanted current flows in the conductors of a communi-cations cable

• A ground loop creates noise because unwanted current flows in the conductors of a communi-cations cable

Desktop Computer

Server

Communications Cable

GNDN120

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Electronic Equipment Grounding TipElectronic Equipment Grounding Tip

GroundingGrounding

•A balun is a coiled extension cord that creates an impedance in the ground loop, reducing loop current

•• A balun is A balun is a coiled a coiled extension cord extension cord that creates an that creates an impedance in impedance in the ground the ground loop, reducing loop, reducing loop currentloop current

Server

BalunDesktop Computer

Desktop Computer

Server

Communications Cable

GNDN120

Balun

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Harmonic DistortionHarmonic Distortion• Harmonic problems

are becoming more apparent because more equipment that produce harmonics are being applied to power systems

• Harmonic problems are becoming more apparent because more equipment that produce harmonics are being applied to power systems

GoodGroundingPractices

SurgeSolutions

HarmonicSolutionsHarmonicSolutions

VoltageVariation Solutions

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Harmonic DistortionHarmonic DistortionHarmonicsHarmonics

Harmonics are multiples of the fundamental frequencyHarmonics are multiples of the fundamental frequencyHarmonics are multiples of the fundamental frequency

When added together result in a distorted waveform

When added When added together result together result in a distorted in a distorted waveform waveform

f(x) = sin(x) +f(x) = sin(x) + sin(5x)sin(5x)55

f(x) =f(x) = sin(5x)sin(5x)55

++ ==

f(x) = sin(x)f(x) = sin(x)

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Harmonic FrequenciesHarmonic FrequenciesHarmonicsHarmonics

Source: Dranetz Handbook for Power Quality AnalysisSource: Dranetz Handbook for Power Quality AnalysisSource: Dranetz Handbook for Power Quality Analysis

Surges andNoise

Disturbance

Surges andSurges andNoise Noise

DisturbanceDisturbanceTransmitted Radio

FrequencyTransmitted RadioTransmitted Radio

FrequencyFrequencyHarmonicHarmonicHarmonic

50/60Hz50/60HzFrequencyFrequency

1 kHz1 kHz 1 MHz1 MHz 100 MHz100 MHz

• 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

• 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

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Sources of HarmonicsSources of HarmonicsHarmonicsHarmonics

•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

•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

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480V480V

120V120V

120V - Neutral120V - Neutral

THD = 15%THD = 15%

NeutralCurrentNeutralCurrent

277V - 1-Phase277V - 1-Phase Switch Mode - PCsSwitch Mode - PCs

Fluorescent LightingFluorescent Lighting

120V - 1-Phase120V - 1-Phase

THD = 30%THD = 30%

THD = 9%THD = 9%

480V Primary480V PrimaryTHD = 7%THD = 7%

480V Secondary480V Secondary

480V Circuit #1480V Circuit #1

480V - 3-Phase480V - 3-Phase

THD = 104%THD = 104%

Variable Frequency DriveVariable Frequency DriveAmpsAmps

AmpsAmps

AmpsAmpsAmpsAmps

AmpsAmps

AmpsAmps

AmpsAmps

Source: IEEE 1100Source: IEEE 1100--19921992

Sources of HarmonicsSources of HarmonicsHarmonicsHarmonics

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Common Symptoms of HarmonicsCommon Symptoms of HarmonicsHarmonicsHarmonics

•Heating caused by higher frequency current components• Insulation stress caused by higher frequency voltage components•Circuit malfunction caused by voltage distortion

•Heating caused by higher frequency current components• Insulation stress caused by higher frequency voltage components•Circuit malfunction caused by voltage distortion

Harmonic voltage and current distortion cause:Harmonic voltage and current distortion cause:

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Common Symptoms of HarmonicsCommon Symptoms of HarmonicsHarmonicsHarmonics

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

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

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HarmonicsHarmonicsHarmonic Distortion StandardsHarmonic Distortion StandardsHarmonic Voltage Distortion LimitsIEEE Standard 519 – 1992Harmonic Voltage Distortion LimitsIEEE Standard 519 – 1992

Maximum Voltage Distortion in % at PCC*Below 69kV 69-138kV >138kV

Maximum for Individual Harmonic 3.0 1.5 1.0Total Harmonic Distortion (THD) 5.0 1.5 1.5

Maximum Voltage Distortion in % at PCC*Below 69kV 69-138kV >138kV

Maximum for Individual Harmonic 3.0 1.5 1.0Total Harmonic Distortion (THD) 5.0 1.5 1.5

* % of Nominal Fundamental Frequency Voltage* % of Nominal Fundamental Frequency Voltage

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HarmonicsHarmonicsHarmonic Distortion StandardsHarmonic Distortion StandardsMaximum Harmonic Current DistortionIEEE Standard 519 – 1992Maximum Harmonic Current DistortionIEEE Standard 519 – 1992

Harmonic Order (Odd Harmonics)Isc/IL <11 11<h<17 17<h<23 23<h<35 35<h %THDHarmonic Order (Odd Harmonics)Isc/IL <11 11<h<17 17<h<23 23<h<35 35<h %THD

In Percent of FundamentalIn Percent of Fundamental

<20* 4.0 2.0 1.5 0.6 0.3 5.0

20-50 7.0 3.5 2.5 1.0 0.5 8.0

50-100 10.0 4.5 4.0 1.5 0.7 12.0

100-1000 12.0 5.5 5.0 2.0 1.0 15.0

>1000 15.0 7.0 6.0 2.5 1.4 20.0

<20* 4.0 2.0 1.5 0.6 0.3 5.0

20-50 7.0 3.5 2.5 1.0 0.5 8.0

50-100 10.0 4.5 4.0 1.5 0.7 12.0

100-1000 12.0 5.5 5.0 2.0 1.0 15.0

>1000 15.0 7.0 6.0 2.5 1.4 20.0

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Corrective ActionsCorrective ActionsHarmonicsHarmonics

• Passive harmonic filters• Active harmonic filters• Zero-sequence traps • Commutation reactors• 200% neutral conductors• K-Factor rated transformers• Harmonic cancellation• Isolation transformers

• Passive harmonic filters• Active harmonic filters• Zero-sequence traps • Commutation reactors• 200% neutral conductors• K-Factor rated transformers• Harmonic cancellation• Isolation transformers

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Design SolutionsDesign SolutionsHarmonicsHarmonics

•Low harmonic producing loads such as– Low harmonic drives–MG sets– 10% distortion lighting ballasts

•Phase shifting transformers

•Low harmonic producing loads such as– Low harmonic drives–MG sets– 10% distortion lighting ballasts

•Phase shifting transformers

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Harmonic Design TipHarmonic Design TipHarmonicsHarmonics

• Harmonic cancellation makes use of transformer connections and phase shifting to cancel harmonics generated from various sources

• Harmonic cancellation makes use of transformer connections and phase shifting to cancel harmonics generated from various sources

YY

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Multi-Cycle Voltage VariationsMulti-Cycle Voltage Variations• Sags are responsible for a majority of

upsets and nuisance trips of sensitive electrical equipment

• Sags are responsible for a majority of upsets and nuisance trips of sensitive electrical equipment

GoodGroundingPractices

SurgeSolutions

HarmonicSolutions

VoltageVariation Solutions

VoltageVariation Solutions

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VoltageVoltageVoltage VariationsVoltage Variations• Sag – a decrease in RMS voltage lasting

from a half-cycle to a few seconds• Sag – a decrease in RMS voltage lasting

from a half-cycle to a few seconds

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VoltageVoltageVoltage VariationsVoltage Variations• Interruption – complete loss of voltage• Interruption – complete loss of voltage

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VoltageVoltageVoltage VariationsVoltage Variations• Overvoltage – an RMS increase in voltage

lasting more than a few seconds• Overvoltage – an RMS increase in voltage

lasting more than a few seconds

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Voltage Variation SymptomsVoltage Variation SymptomsVoltageVoltage

•Sag– Substandard product– Process interruption

• Interruption–Complete loss of power

•Overvoltage– Equipment damage

•Sag– Substandard product– Process interruption

• Interruption–Complete loss of power

•Overvoltage– Equipment damage

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Voltage Variation SourcesVoltage Variation SourcesVoltageVoltage

• Supply side variations• Short circuits• Capacitor switching• Load switching• Regulator malfunction• Load side variations• Motor starting

• Supply side variations• Short circuits• Capacitor switching• Load switching• Regulator malfunction• Load side variations• Motor starting