Power Quality Indices / Pitfalls / Three Phase Phenomena and Applications / ‘Interharmonics’ and Other Non-Harmonics 2

A PSERC Tutorial on Contemporary Topics in Electric Power Quality Alias G. T. Heydt Arizona State University A ‘Tutrial’ on Power Quality

PROGRAM

1. Power quality indices / pitfalls / three phase phenomena and applications / ‘interharmonics’ and other non-harmonics 2. Power acceptability, when is electric power Power Quality Indices delivered ‘acceptable’, vulnerability of loads 3. Series voltage boost hardware 4. Rectifier loads 5. Power quality standards 6. Why is power quality important? The salability of power quality

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Power Quality Indices Index Definition Main applications EVEN HARMONICS Total harmonic dis-  ∞   II / tortion (THD)  ∑ i  1 General purpose; standards  i =2  PV/| || I | Power factor (PF) tot rms rms Potentially in revenue metering • THEORETICALLY IMPOSSIBLE FOR Telephone influence  ∞   wI2  / I factor  ∑ ii rms Audio circuit interference  i =2  SIGNALS THAT ARE SYMMETRIC ABOUT  ∞   cI2  / I THE TIME AXIS C message index  ∑ ii rms Communications interference  i =2  ∞ • PRESENCE OF EVEN HARMONICS DO NOT IT product 22 Audio circuit interference; shunt capacitor ∑ wIii = stress i 1 IMPLY DC COMPONENTS IN THE GIVEN ∞ VT product 22 ∑ wVii i =1 Voltage distortion index SIGNAL  ∞  ∞ K factor hI2 22/ I ∑∑hh • MOST COMMON OCCURRENCE OF EVEN  h=1  h=1 Transformer derating VV/ Crest factor peak rms Dielectric stress HARMONICS IS IN THE SUPPLY CURRENT Unbalance factor ||/||VV−+ Three phase circuit balance OF TRANSFORMERS WHOSE LOAD SIDE Incandescent lamp operation; bus voltage ∆ Flicker factor VV/| | regulation; sufficiency of short circuit ca- HAVE DC CURRENT COMPONENTS pacity 5 6

1 EVEN HARMONICS

Displacement factor (True) power factor AC AC + DC COMPONENT

φ LOAD DF = cos( 60) PF = V (ΣP)/|Vrms||Irms| ‘Power frequency I power factor’ ‘Total power over V total volt-amperes’

PRESENCE OF DC ON ≤ SUPPLY SIDE INDICATIVE I TPF ≤ DF OF DC ON LOAD SIDE 7 8

ΣP = (1)(1)cos30o + (0.2)(0.2)cos60o + EXAMPLE (0.05)(0.15)cos(30o) = 0.892 RMS 60 Hz 180 Hz 420 Hz (Vrms)2 = 12 + 0.22 + 0.052 V 1∠0o 0.2∠20o 0.5 ∠10o Vrms = 1.021 I 1∠-30o 0.2∠80o 0.15 ∠-20o (Irms)2 = 12 + 0.22 + 0.152 Irms = 1.031

9 S = (Vrms)(Irms) = 1.052 10

POWER FACTOR MULTIPLIERS

• BILLING MULTI[PLIERS TO SEND THE CUSTOMER THE PROPER SIGNAL CONCERNING POWER FACTOR • MULTIPLIER NEAT 1.0 FOR ~86%PF LAG TPF = ΣP / S = 0.848 • MULTIPLIER INCREASES TO ~1.3 FOR DECREASING POWER FACTOR • MULTIPLIER DECREASES TO ~0.95 FOR PF NEAR UNITY o • e.g., 0.06 $/kWh AT 86% PF LAG, 0.08 $/kWh AT LOW DF = DPF = cos(30 ) = 0.866 (lag) POWER FACTOR • WHICH PF? TPF? DISPLACEMENT FACTOR? • CUSTOMERS FAVOR USE OF DF, UTILITIES FAVOR TPF • LOSSES MORE CLOSELY RELATED TO TPF THAN DF • REQUIRED kVA OF SUPPLY EQUIPMENT MORE CLOSELY RELATED TO TPF 11 • INSTRUMENTATION ISSUES 12

2 THD THD RMS 60 Hz 180 Hz 420 Hz THE THD OF A SQUARE WAVE OF AMPLITUDE ±1 IS EASILY FOUND NOTING THAT THE RMS VALUE OF SUCH A WAVE IS 1.000 AND THE V 1∠0o 0.2∠20o 0.5 ∠10o FUNDAMENTAL COMPONENT IS 4/Π (ZERO TO PEAK). THE FUNDAMENTAL COMPONENT IS I 1∠-30o 0.2∠80o 0.15 ∠-20o (0.707)(4/Π) = (0.9002). THEREFORE THE SUM OF THE SQUARES OF THE HARMONIC 2 2 2 VTHD = 0.2 + 0.05 / 1 COMPONENTS IS 12-0.90022 = (0.1896). ITHD2 = 0.22 + 0.152 / 1 THEN,

VTHD = 20.62% ITHD = 25% THD2 = 0.1896/0.9002 THD = 45.89% 13 14

THD - ANOTHER EXAMPLE f |V| | I | Three Phase Considerations 60 1.00 1.00 180 0.01 0.31 Balanced THD 300 0.04 0.15 Based on positive and negative sequence THDs only 420 0.03 0.07 540 0.02 0.03 Residual THD 660 0.01 0.02 Based on zero sequence only VTHD2 = 0.012 + 0.042 + 0.032 + 0.022 + 0.012 VTHD = 5.57%

ITHD = 35.33% 15 16

THD THD ADVANTAGE: EVERYONE USES IT, THE RESIDUAL THD IS GENERALLY EASY TO CALCULATE, WIDELY FAR MORE HARMFUL THAN USED IN STANDARDS AND GUIDES BALANCED THD BECAUSE THERE IS NO ‘CANCELLATION EFFECT’ OF DISADVANTAGES: DOES NOT THE THREE PHASES OUT OF PHASE ACCELERATE WITH FREQUENCY, BY 120o BALANCED AND RESIDUAL THD NOT AS WELL KNOWN, DOES NOT TRULY SHOW THE INTERFERENCE IMPACT OF THE SIGNAL 17 18

3 TOTAL DEMAND DISTORTION DISTORTION INDEX (DIN) (TDD) TOTAL DEMAND DISTORTION IS A ∞ MEASURE OF THE THD TAKING INTO 2 ACCOUNT THE CIRCUIT RATING. AS I CIRCUIT RATING VERSUS LOAD CURRENT ∑ i RISES, TDD DROPS DIN = 2 TDD = THD * (Fundamental load current / Circuit rating) I rms

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TELEPHONE INFLUENCE I∗T PRODUCT FACTOR ∞ 2 2 ∑ wi Ii IT = TIF * Irms TIF = 1 Irms

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PEAK VALUES V*T PRODUCT PEAK VALUES CAN BE CHARACTERIZED BY A CREST FACTOR: • DEFINED LIKE I*T PRODUCT USING CF = PEAK VALUE / RMS VALUE VOLTAGE = 1.414 FOR A PERFECT SINE WAVE • kVT = 1000 VT • BALANCED AND RESIDUAL V*T PRODUCT ABSOLUTE LARGEST VALUE CAN BE OVERESTIMATED FOR ASYNCHRONOUS • USED IN SHUNT CAPACITOR SIGNALS AS THE SIMPLE ALGEBRAIC SUM STANDARDS - TO LIMIT HARMONIC OF THE AMPLITUDES OF THE CURRENTS ASYNCHRONOUS FREQUENCIES 23 24

4 RMS VALUES RMS VALUES

If the function is not periodic, take limit as T --> infinity T 1 2 = Parseval’s theorem -- for signals of FRMS f (t)dt T ∫0 different frequencies,

2 2 2 2 (Vrms) = (V1rms) +(V2rms) +(V3rms) +... 25 26

RMS VALUES RMS VALUES

If signals are of the same Examples frequency, need to combine the 10cos(t) + 2cos(2t)+ sin(3t) same frequency terms using 10 2 cos(t) +10 2 sin(t) phasor arithmetic, and then apply 10cos(t) +10sin( 2t) Parseval’s theorem without regard for phase angles 440 2 cos(314t) + 50 2 sin(314t) + 80 2 sin(492t) +10cos(1570t)

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RMS VALUES RMS VALUES Second example First example 1. Gather like frequency terms

10 2 1 f (t) = 10 2( 2 cos(t + 45o )) F 2 = ( )2 + ( )2 + ( )2 rms 2 2 2 2. Find RMS value of result =5.123 2 = 20 = Frms 14.14 29 2 30

5 RMS VALUES RMS VALUES

Third example Fourth example This example is aperiodic -- but no change in First combine fundamental term application of Parseval’s theorem: = 2 + 2 = F1,rms 440 50 442.83 2 = 1 2 + 1 2 Frms ( ) ( ) 2 2 Then apply Parseval’s theorem = Frms 1.00 = 2 + 2 + 2 = Frms 442.83 80 10 450.11 31 32

CONSEQUENCES OF TRANSFORMER DERATING HARMONICS DEFINE PLL-R AND PEC-R AS THE FULL LOAD LOSSES AND CORE LOSSES PER- • I2R HEATING DUE TO EXCESS UNITIZED BY THE I2R LOSSES. THEN THE CURRENT DERATED TRANSFORMER MAXIMUM • TRANSFORMER MAGNETIC LOSSES CURRENT IN PER UNIT IS • INCREASED MOTOR LOSSES P • INCREASED CREST CURRENT I = LL−R • CIRCUIT BOARD HEATING derated + 1 KPEC−R

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APPLICATION OF IEEE C57.110 TRANSFORMER DERATING DERATING BASIC METHOD • CALCULATE TOTAL CORE LOSSES P THIS DERATING IS CONSERVATIVE EC • CALCULATE I2R LOSSES, P IN THAT ALL CORE LOSSES ARE I2R • CALCULATE TOTAL FULL LOAD LOSSES P INCREASED BY A FACTOR OF K -- LL • PERUNITIZE P AND P BY P THIS IS AN OVERESTIMATE OF THE LL EC I2R B-H LOSSES. THE METHOD IS IN • CALCULATE THE K-FACTOR OF THE LOAD CURRENT COMMON USE AS PRESCRIBED BY • CALCULATE DERATED RATING OF LOAD IEEE STANDARD C57.110, UL 1561 CURRENT P AND UL1562. I = LL−R derated + 1 KPEC−R 35 36

6 EXAMPLE A 67.5 kVA 1Ø DISTRIBUTION IT MAY BE NECESSARY TO TRANSFORMER IS RATED 7200 / 240 V. CALCULATE I2R LOSSES USING FULL THE CORE LOSSES ARE 75 W AT RATED VOLTAGE, AND THE FULL LOAD LOSSES LOAD CURRENT AND NAMEPLATE ARE 190 W. THE WINDING RESISTANCES RATING OF RESISTANCE --OR AN ARE 0.5% TOTAL. FIND THE DERATED ESTIMATE OF THE RESISTANCE. TRANSFORMER CAPACITY TO CARRY A LOAD CURRENT OF 150% THD WHICH IS COMPOSED OF FUNDAMENTAL AND THIRD HARMONIC. 37 38

SOLUTION SOLUTION P I = LL−R derated + 1 KPEC−R Irated = (67.5 k) / 240 = 281.25 A

0.563 = Iderated = (281.25)(0.479) 1+ (6.54)(0.222) = 138 A = 0.479 pu 39 40

Power Acceptability Curves APPROXIMATION 250

200

OVERVOLTAGE CONDITIONS

C 150

B 100 0.5 CYCLE PLL-R = PEC-R + 1 E 50

RATED M 0 ACCEPTABLE POWER VOLTAGE

-50 A PERCENT CHANGE IN BUS VOLTAGE

8.33 ms 8.33 UNDERVOLTAGE CONDITIONS

-100 0.0001 0.001 0.01 0.1 1 10 100 1000 41 TIME IN SECONDS 42

7 Power Acceptability Curves Power Acceptability Curves

250

200 BUS B

OVERVOLTAGE CONDITIONS FAULT 150 I BUS A z+, z-, z0

100 T z+, z-, z0 CIRCUIT BREAKER 0.5 CYCLE 0.5 50 I

+-- 10% SOURCE RATED z+, z-, z0 0 ACCEPTABLE C POWER VOLTAGE BUS C -50 PERCENT CHANGE IN BUS VOLTAGE LOAD 8.33 ms UNDERVOLTAGE CONDITIONS

-100 0.0001 0.001 0.01 0.1 1 10 100 1000 43 44 TIME IN SECONDS

Power Acceptability Curves Power Acceptability Curves

Disturbances to loads, whether they be overvoltages or undervoltages, have an impact depending on how much excess energy is Main challenges delivered to the load (in the overvoltage case) or how much energy was not delivered to the load (in How to sell power quality as a service the undervoltage case). If the cited energy level is too great, the operation of the load will be How to sell PQ measurement services disrupted. This basic assumption is termed the How to compensate customers for ‘constant energy model’ because it implies that ‘unacceptable power’ the power acceptability curves are loci of constant energy. When the disturbance energy exceeds the locus plotted, the power supply is ‘unacceptable’. 45 46

IEEE P1346 - Displaying Sag Data Voltage Sags for Equipment Compatibility

Interruption and Sag Rate Probabilties as a Function of Event Voltage Magnitude and Duration 90 Variations in voltage that last 80

less than 1 minute. 15-20 70

10-15 events 60

50 5-10 events per Characterized by site per year 40 (%) Magnitude rms voltage vs. time 0-5 events per plot. site per year 30

10 1 2 4 6 8 10 20 30 40 50 60 180 300 >3000 Duration (Cycles) 47 48

8 System Average RMS (Variation) Experimental Results Taken by Frequency Index Voltage EPRI / Electrotek Threshold -- SARFI%V for SARFI70% Rate of Voltage Drops below 70% at Each Monitoring Site • Number of specified 30% 100% Ni short-duration rms = ∑ 90% SARFI %V 25% variation per system 80% NT Mean: 17.72 70% customer 20% Standard Deviation: 1.63 • Voltage threshold 95% Confidence Interval: 60% %V rms voltage threshold 15% 14.52 to 20.92 50% 140, 120, 110, 90, 80, 70, 50, 10 allows assessment of 40%

N # customers experiencing Frequency compatibility for i 10% rms < %V for variation i 30%

voltage-sensitive 20% Frequency Cumulative (rms > %V for %V >100) 5% devices 10% NT total # system customers 0% 0%

• 60 second aggregation 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 Sags and Interruptions below 70% per 365 Days 49 50

Inject series voltage for phase control / exchange energy between phases

Series Voltage Boost Shunt positioning in Hardware system to inject current

Back -to -back rectifier / DC link / inverter 51 52

The UPFC is intended for AC - AC Converter The UPFC and use at transmission levels DVR and the DVR is intended Technologies for use at distribution levels RECTIFIER DC link

POWER FLOW SERIES XFORMER

PWM INVERTER SUPPLY THE UNIFIED POWER FLOW LOAD CONTROLLER AND DYNAMIC AC/AC PWM VOLTAGE RESTORER UTILIZE IGBT CONVERTER TECHNOLOGY TO GENERATE PWM SIGNALS OF CONTROLLABLE MAGNITUDE / PHASE. THIS EFFECTIVELY CONTROLS THE ACTIVE POWER FLOW WHEN INJECTED AS A SERIES VOLTAGE 53 54

9 THE UPFC and DVR THE UPFC / DVR • 1/4 cycle response time • Cost is very high • Very low DC link power • Local solution (?) • Can be protected by crowbaring supply • Controls are tricky LOAD • Individual phase control / exchange • Solution of diversity of VOLTAGE energy between phases ownership problems • Controls slow variations in supply voltage • Relatively low power • The distribution version (DVR) can injected SERIES improve supply power factor and • Limited experience in power quality SUPPLY VOLTAGE applications • For the distribution version, VOLTAGE potential elimination of vulnerable load problems LOAD • For UPFC, can reduce transmission CURRENT congestion as well as improve dynamic response 55 56

Vser DVR FOR VOLTAGE REGULATION AT THE DISTRIBUTION LEVEL SUPPLY BUS

OPTIONAL 420 ENERGY LOAD PULSE VOLTAGE STORAGE 280 WIDTH LOAD ELEMENT INJECTION MODULATOR BUS RECTIFIER OF REACTIVE 140 u MAXIMUM Vser POWER SUPPLY 0 VOLTAGE DC |V | cos PWM -140 0.00 9.77 L 19.53 29.30 39.06 48.83 58.59 68.36 78.13 87.89 97.66

-280 C (V) PHASE B VOLTAGE -420 Tshift LOAD CURRENT CONTROLS Ma TIME (ms)

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DVR FOR VOLTAGE REGULATION AT THE DISTRIBUTION LEVEL

APPARENT (REACTIVE) POWER MINIMUM SUPPLY VOLTAGE INJECTED BY SERIES CORRECTABLE TRANSFORMER (PU) TO 1.0 PER UNIT V L Rectifier Loads and INCREASING |VL ||IL | |V 1 | |V1 | = 0.25 |VL| their Harmonic 22 |VL | - |Vser, max| |V | = 0.5 |VL| 0.5|VL ||IL | 1

|V L| - |Vser, max| Impact |V1 | = 0.71 |VL| 0 |V | = 0.9|V | 0 ARCSIN( |Vser| / |VL| ) 1.0 1 L 0 LAGGING LOAD POWER FACTOR 0 0.5 LAGGING POWER FACTOR 1.0

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10 1Ø RECTIFIER LOADS 1Ø RECTIFIER LOADS

LINE COMMUTATED 22 VV= INFINITE DC INDUCTANCE dcπ ac LINE COMMUTATED ω FIXED DC CURRENT = − 2 I dc L s 22 INFINITE DC INDUCTANCE cos( u ) 1 ZERO SUPPLY INDUCTANCE II= 2V acfundamentalπ dc FIXED DC CURRENT s NONZERO SUPPLY INDUCTANCE ω = 2 2 2 L s I dc IIsupply , h acfundamental / h V = V − dc π s π THD = 48. 43% u DPF = 1 DPF ≈ cos( ) 2 22 = = TPF = P V s I ac , fundamenta l DPF V dc I dc π 22 PP== VI dc acπ s, rm s dc

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A NOTE ON SINGLE PHASE RECTIFIER LOADS SUPPLIED BY A THREE PHASE 1Ø RECTIFIER LOADS SYSTEM

FORCED COMMUTATED 2 ω L I cos( α + u ) = cos( α ) − s dc INFINITE DC INDUCTANCE V 2 FIXED DC CURRENT s u CURRENT NONZERO SUPPLY INDUCTANCE DPF = cos( α + ) Ia Ib Ic 2 1 ph 1 ph 1 ph 2 2 2ωL bridge bridge bridge A V I cos( α ) − s I 2 rect rect rect π s dc π dc I = sup ply fundamenta l u V cos(α + ) B s 2 2 2 2 V = V cos( α ) − ωL I dc π s π s dc C

SUM time 63 64

3Ø RECTIFIER LOADS 3Ø RECTIFIER LOADS six pulse six pulse

LINE COMMUTATED 32 VV= SIX PULSE dcπ LL INFINITE DC INDUCTANCE LINE COMMUTATED 3 2 3ωL FIXED DC CURRENT = SIX PULSE V = V − S I IIsrms, 23/ dc dc π LL π dc ZERO SUPPLY INDUCTANCE INFINITE DC INDUCTANCE 6 FIXED DC CURRENT 2ωL I II= cos(u) = 1− s dc suply , fundamentalπ dc NONZERO SUPPLY INDUCTANCE 2VLL = DPF 1 u DPF ≈ cos( ) 3 TPF = 2 π u P = 3V I cos( ) = V I THD = 31. 08% (5 , 7 , 11 ,...) LL sup ply, fundamental 2 dc dc

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11 3Ø RECTIFIER LOADS CALCULATION OF HARMONIC LOADS CURRENTS FROM SINGLE PHASE AND six pulse THREE PHASE RECTIFIERS

THE HARMONIC LOAD CURRENT FORCED COMMUTATED ω DEMANDS OF RECTIFIERS MAY BE = 3 2 α − 3 L S SIX PULSE V dc V LL cos( ) I dc INFINITE DC INDUCTANCE π π CALCULATED FROM THE FIXED DC CURRENT 2 ω L I NONZERO SUPPLY INDUCTANCE cos( α + u ) = cos( α ) − s dc RECTIFIER FORMULAS TO FIND I1 - 2 V LL u THEN FIND THE ODD HARMONICS DPF ≈ cos( α + ) 2 (SINGLE PHASE) OR 5, 7, 11, 13TH HARMONICS (SIX PULSE) USING THE 1/h RULE

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SOLUTION EXAMPLE

A 1000 kVA three phase six-pulse rectifier Find transformer reactance serves a 2000 V DC load using the delay x = 2 = [(6900/ )2 / (1.1M/3)] angle to hold the DC voltage constant over base v / s 3 all loads in the range 100 to 250 kW. The = 43.28 ohms supply transformer is rated 1100 kVA, 13.8 kV / 6900 V, x=20%, 50 Hz. Estimate the fifth ω L = x = 8.656 ohms and seventh harmonic currents on the high s s voltage side of the transformer in the 100 - 250 kW operating range. 69 70

SOLUTION SOLUTION FORCED COMMUTATED 3 2 3 ω L = α − S SIX PULSE V dc V LL cos( ) I dc INFINITE DC INDUCTANCE π π FIXED DC CURRENT 2 ω L I cos(α + u) = cos α -(2 ω LsIdc/ 2 VLL) NONZERO SUPPLY INDUCTANCE cos( α + u ) = cos( α ) − s dc 2 V LL u DPF ≈ cos( α + ) cos(71.003+u)=cos (71.003)-(2)(8.656)(250k)/(6900)( )(2k) 2 2

u = 13.042o At 250 kW 2000 = (3 /π )(6900)(cos α ) - ((3)(8.656)/π)(250k/2k) 2 DPF = cos(α + u/2) = 0.216

= 71.003o α 71 72

12 SOLUTION SOLUTION

DPF = cos(α + u/2) = 0.2149 I1 = S/V = (1.157M/3)/(13.8k/1.732) = 48.405 A S = P/DPF = 100k/0.2149 = 465.4 kVA I1 = S/V = (465.4k/3)/(13.8k/1.732)

I5 = (1/5) I1 = 9.68 A = 19.472 A I5 = (1/5) I1 = 3.89 A I = (1/7) I = 6.92 A I = (1/7) I = 2.78 A 7 1 73 7 1 74

ANALYSIS OF HIGHER PULSE SUMMARY ORDER CONVERTERS

100 kVA operation 250 kVA operation • BREAK CIRCUIT INTO SEVERAL 9.68 A IDENTICAL SIX PULSE CONVERTERS 6.92 A • EACH SIX PULSE CONVERTER 3.98 A 5 OPERATES AT IDENTICAL P, I, V ± 2.78 A 7 • HARMONICS AT pn 1 5 7 75 76

ADJUSTABLE SPEED DRIVES PWM DRIVES Analysis as for DC machine drives rectifiers – Controlled rectifier types THE PWM DRIVE TECHNOLOGY RELIES ON Synchronous machine drives THE USE OF A PULSE WIDTH MODULATOR – PWM PWM analysis – Rectifier-inverter THAT MODULATES A HIGH FREQUENCY – Cycloconverter WAVE (e.g., 10 kHz, THE CARRIER) WITH A Induction machine drives SINUSOIDAL WAVE OF ARBITRARY Chopper – PWM FREQUENCY AND PHASE analysis – Rectifier - inverter – Cycloconverter 77 78

13 V(f) switching frequency much higher than carrier

fo fc Power Quality

carrier Standards P W M

control adjustable amplitude

adjustable phase 79 80

Who Develops PQ Structure of Basic and Generic Standards? EMC Standards • International Standards Groups Part 1: General (IEC Pub 1000-1) – IEC (mostly TC 77) fundamental principles, definitions, terminology – CIGRE (SC 36) Part 2: Environment (IEC Pub 1000-2) – The European Norm (EN) description, classification and compatibility levels Part 3: Limits (IEC Limits 1000-3) – National standards worldwide (e.g., BNS) emission and immunity limits, generic standards • Standards Groups in North America Part 4: Testing and measurement (IEC Pub 1000-4) – IEEE (really international, mostly PES and IAS) techniques for conducting Part 5: Installation and mitigation (IEC Guide 1000-5) – ANSI installation guidelines, mitigation methods and devices – UL, NEMA, NFPA, NIST 81 82

IEC Approach IEC Equipment Limits (IEC 1000-3-3, IEC 1000-3-5) • Limit harmonic currents for individual equipment (type testing) • Limits for unbalance • IEC 1000-3-2 for equipment up to 16 amps – LV-MV: 2% • IEC 1000-3-4 for equipment up to 75 amps – HV: 1% (under development) • Limits for flicker • This should limit overall harmonic Voltage Level Pst (pu) Plt (pu) distortion levels to acceptable values • Procedure for evaluating customers LV 1 0.74 supplied at medium voltage and high MV 10.74 voltage (1000-3-6) HV 0.85 0.62

83 EHV 0.7 0.5 84

14 IEC Standards for Harmonic IEC 1000-2-2 Compatibility Levels Distortion Levels Harmonic Voltage COMPATIBILITY LEVELS (IEC 1000-2-2) ODD HARMONICS EVEN HARMONICS not multiple of 3 multiples of 3 • Customer/System Limits Harmonic Voltage (%) Harmonic Voltage (%) Harmonic Voltage (%) – IEEE 519-1992 Order h LV-MV HV Order h LV-MV HV Order h LV-MV HV – IEC 1000-2-2 (Compatibility Levels) – IEC 1000-3-6 56 2352222 7 5 2 91.5141 1 – G5/3 (United Kingdom) 11 3.5 1.5 15 0.3 0.3 6 0.5 0.5 13 3 1.5 21 0.2 0.2 8 0.5 0.5 • Equipment Limits 17 2 1 10 0.2 0.5 – IEC 1000-3-2 (Formerly IEC 555-2) up to 16 amps 19 1.5 1 >21 0.2 0.2 12 0.2 0.2 – IEC 1000-3-4 16-75 amps 23 1.5 0.7 – New Task Force in IEEE (Harmonic Limits for Single Phase 25 1.5 0.7 >12 0.2 0.2 Loads) >25 0.2+1.3(25/h) 0.2+0.5(25/h) • How to Measure Harmonics – IEC 1000-4-7 THD Limit = 8% for LV-MV Systems 85 86

Key PQ Publications / Commonly used standards IEEEIEEE Guide IEEE P519A - Harmonics IEEE 1250 Recommended IEEE P1346 - Voltage sags Practice Gold book - Reliability IEC 1000-5-# Standard

87 88

Power Quality Related Standards of the IEEE Philosophy of IEEE 519 Recommended Practices The utility is IEEE 446 - Emergency and Standby Power responsible for IEEE 519 - Harmonic Control maintaining quality of voltage IEEE 1001 - Interface with Dispersed Generation waveform. IEEE 1100 - Power and Grounding Electronics IEEE 1159 - Monitoring Power Quality The customer is IEEE 1250 - Service to Critical Loads responsible for IEEE 1346 - System Compatibility in Industrial limiting harmonic Environments currents injected IEEE 1366 - Electric Utility Reliability Indices onto the power 89 system. 90

15 IEEE 519 Harmonic Voltage Meeting Voltage Distortion Limits Limits

Maximum Individual Maximum • Limit the harmonic currents from Bus Voltage Harmonic Component (%) THD (%) nonlinear devices on the system (customer harmonic current limits) 69 kV and below 3.0% 5.0% 115 kV to 161 kV 1.5% 2.5% • Make sure that system resonances do not Above 161 kV 1.0% 1.5% result in excessive magnification of the customer harmonic currents (utility control of system response) Harmonic Voltage Limits - Utility Responsibility

91 92

IEEE 519 Harmonic Current Transients: ANSI C62.41 Limits

2.0 Harmonic Current Limits - Customer Responsibility 34.5 kV Bus Voltage Capacitor Switching Transien SCR =I /I sc L <11 11

50 - 100 10.0 4.5 4.0 1.5 0.7 12.0 0.5 100 - 1000 12.0 5.5 5.0 2.0 1.0 15.0 0.0

>1000 15.0 7.0 6.0 2.5 1.4 20.0 Voltage (V pu)

-0.5 Values shown are in percent of “average maximum demand load current”

SCR = short circuit ratio (utility short circuit current at point of common -1.0 coupling divided by customer average maximum demand load current)

TDD = Total Demand Distortion (uses maximum demand load current as -1.5 the base, rather than the fundamental current) 0 20 40 60 80 100 Time (mS) PCC = measurements taken at point of common coupling 93 94

Environment - (IEEE/ANSI C62.41)

103 Clearance Sparkover Graph for a 1 kV 102 circuit Why is Power Quality

101 Rate of surge Important? High Surges/Year Exposure occurrences 1 versus Medium voltage level at Exposure unprotected -1 10 locations Low Exposure 10-2 0.3 0.5 1 2 5 10 20 Surge Crest (kV) 95

16 • Cost The Cost of Power Quality • Competitiveness Calculated by the sum of the costs of • Down time the measures taken to improve PQ; • Losses or the cost of customer losses in • Loss of life industrial production; or the payment to customers for PQ • Metering error problems; or the total active power • EMC energy loss plus metering error plus • Proper service to the load loss of life plus cost to serve peak including harmonic loss? 97 98

The Cost of Power Quality Losses and Loss of Life

• Losses depend on |I|2R Alternatively estimated at 6B$ (BMI / • Excess heating in iron components Electrotek), 3B$ annually (EPRI) or may be problematic 1B$ (Heydt at IEEE-T&D Meeting) • Losses = costs, especially at peak periods Whatever the figure is, it is avoidable • Loss of life depends on Dakin’s rule, to some degree, and when costs rate of reaction doubles every 20O C occur, they can create real problems rise

99 100

Downtime / Proper service Questions? to Load

• Telephone interference (TIF) Comments? • Computer interference (C-message weight index) • Momentary outage hardening (CBEMA, Complaints? ITIC) • UPS and power conditioner applications

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