overview of the guide for applying harmonic limits on

Overview of the Guide forApplying Harmonic Limits onPower Systems - IEEE P519A

Mark McGranaghan

Electrotek Concepts, Inc.1998 PATH WorkshopKnoxville, TennesseeOctober, 1998

P519A - 2

Scope of IEEE 519-1992

u Provide methodology for preventing harmonicvoltage and current distortion problems on thepower system through utility and customercooperation.

P519A - 3

Basic Philosophy of IEEE 519

u The customer isresponsible for limitingharmonic currentsinjected onto the powersystem.

u The utility is responsiblefor maintainingquality of voltagewaveform.

P519A - 4

Harmonic Voltage Limits

Harmonic Voltage Limits - Utility Responsibility

Maximum IndividualHarmonic Component (%)

MaximumTHD (%)

Bus Voltage

69 kV and below 3.0% 5.0%115 kV to 161 kV 1.5% 2.5%Above 161 kV 1.0% 1.5%

P519A - 5

Meeting Voltage Distortion Limitsu Limit the harmonic currents from nonlinear

devices on the system (customer harmonic currentlimits).

u Make sure that system resonances do not result inexcessive magnification of the customer harmoniccurrents (utility control of system response).

P519A - 6

Harmonic Current Limits

Harmonic Current Limits - Customer Responsibility

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

SCR = short circuit ratio (utility short circuit current at point of commoncoupling divided by customer average maximum demand load current)

TDD = Total Demand Distortion (uses maximum demand load current as thebase, rather than the fundamental current)

SCR =Isc/IL <11 11<h<17 17<h<23 23<h<35 35<h TDD

4.0 2.0 1.5 0.6 0.3 5.0

7.0 3.5 2.5 1.0 0.5 8.0

10.0 4.5 4.0 1.5 0.7 12.0

12.0 5.5 5.0 2.0 1.0 15.0

<20

20 - 50

50 - 100

100 - 1000

>1000 15.0 7.0 6.0 2.5 1.4 20.0

P519A - 7

Important Concepts

u Point of Common Coupling

u Average Maximum Demand Load Current

u SCR - Short Circuit Ratio

Utility System

Customer Under Study

Other UtilityCustomers

PCC

IL

Utility System

Customer Under Study

Other UtilityCustomers

PCC

IL

P519A - 8

Important Sections of P519A

u General Procedure

u Applying Limits for Large Nonlinear Loads

u Applying Limits for Industrial Facilities

u Applying Limits for Commercial Facilities

u Applying Limits for Residential Loads

u Utility Considerations

P519A - 9

General ProcedureUTILITY

Choose PCC,and Calculate Ssc

CUSTOMER

Estimate Sdw or % disturbing loads

Is PF correction existing

or planned?

Characterize harmonic levels

(measurement, calculation)

Design harmoniccontrol equipment

Verification bymeasurement and calculation

(if necessary)

Yes

No

YesNo

No

Yes

Stage 1: Automatic

acceptance?

Stage 2: Meet harmonic

limits?

P519A - 10

Automatic AcceptanceType of Load Typical Waveform

CurrentDistortion

WeightingFactor (Wi)

Single PhasePower Supply

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

80%(high 3rd)

2.5

Semiconverter

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

high 2nd,3rd,4th at partial

loads2.5

6 Pulse Converter,capacitive smoothing,no series inductance

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

80% 2.0

6 Pulse Converter,capacitive smoothing

with series inductance > 3%,or dc drive

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

40% 1.0

6 Pulse Converterwith large inductor

for current smoothing

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

28% 0.8

12 Pulse Converter

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Current

15% 0.5

ac VoltageRegulator

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Current

varies withfiring angle 0.7

Automatic Acceptance if:

SDw / SSC < 0.1 %

Note: detailedevaluation shouldalways be performedif power factorcorrection capacitorsexist or are planned

P519A - 11

Important Concept -Time Varying Nature of Harmonics

0

2

4

6

8

10

0 10 20 30 40 50 60Tim e (minutes)

Cu

rren

t T

HD

(%

)

Current THD measured at Port of Vancouver, B.C.(harmonic bursts are caused by cranes lifting containers)

P519A - 12

Use statistics to describe theharmonic levels

0 5 10 15 20 0

250

500

750

1000

1250

1500

0

20

40

60

80

100

Current (A)

Count

Cumulative Probability (%)

Statistical Summary of Total Harmonic RMS Current (Amps)

Compare with519 Limits

P519A - 13

Short bursts vs. continuousharmonic distortion

Both cases have THDs exceeding 5% for 40% of themeasurement period. But case A is more severe since theharmonic bursts are concentrated in a single period.

0

2

4

6

8

10

0 20 40 60 80 100

Time (minutes)

TH

D (

%)

0

2

4

6

8

10

0 20 40 60 80 100

Time (minutes)

TH

D (

%)

case A case B

P519A - 14

BC Hydro limits

Acceptableharmonic distortion level

Maximum duration ofa single harmonic burst

(Tmaximum)

Total duration ofall harmonic bursts

(Ttotal)

3.0 x (design limits) 1 sec < Tmaximum < 5 sec 15 sec < Ttotal < 60 sec

2.0 x (design limits) 5 sec < Tmaximum < 10 min 60 sec < Ttotal < 40 min

1.5 x (design limits) 10 min < Tmaximum < 30 min 40 min < Ttotal < 120 min

1.0 x (design limits) 30 min < Tmaximum 120 min < Ttotal

The limits apply to a 24 hour measurement period

P519A - 15

Measurement Considerations

u Where to measure– effect of transformer when measuring on the

low side and PCC is on the high side

u Voltage measurements

u Current measurements– what is the base current?

u Monitoring Durations

u Sampling Requirements

P519A - 16

System Conditions to Consider(for analysis of potential problems)

• power factor correction capacitors in the customer facility

• harmonic filter out of service

• power factor correction capacitors on the utility supplysystem

• alternative sources from the utility (e.g. alternate feeders)

• different load combinations than can be evaluated in thefield tests

• nearby customers with significant harmonic production

P519A - 17

1. A two staged procedure to evaluate a facility

2. Apply steady-state limits to time varying data

3. Conditions to evaluate limit compliance

• Stage 1: Automatic acceptance for facilities with little disturbing loads• Stage 2: Should demonstrate compliance to harmonic limits

• Methods to characterize time varying harmonic measurements• Methods to apply the limits to measured data• Consideration of plant operating cycles at the design stage

• Measurement: instrumentation, monitoring duration, ... • Calculation: modeling assumptions, plant operating conditions, ...

Summary

IEEE P519AConcerns for IndustrialFacilities

October, 1998

P519A Industrial Evaluations - 2

Industrial Concerns

u Nonlinear Loads– ASDs, dc drives, rectifiers for dc processes,

induction furnaces, arc furnaces

u Power Factor Correction– capacitors result in resonance concerns

u Motor Loads– do not provide much damping for harmonics


Industrial Evaluations:The Six-Step Process

u Step 1: Select the PCC– normally the high-side of the supply transformer(s)

u Step 2: Characterize the nonlinear loads– “typical” spectra may be used

– measurements are needed for load groups

u Step 3: Determine power factor correction needs– parallel resonance may magnify harmonics

– series resonance may “sink” harmonics from the utility


The Six-Step Process, cont.

u Step 4: Evaluate harmonic performance at PCC– frequency response of power circuits

– harmonic characteristics of loads

u Step 5: Design harmonic mitigation equipment– passive filters coordinated with power factor correction

capacitors

– active filters may be better for smaller needs

u Step 6: Verify performance with measurements– monitor long enough to capture temporal variations


Example case to illustrateindustrial evaluation issues

u multiple sources, harmonic cancellationeffects

u power factor correction/resonance concerns

u choosing the PCC

u design of harmonic filters to controlharmonic levels

u evaluating the time varying nature of theharmonic levels


Example System


Harmonic Source Characteristics

Wye-DeltaTransformer

Serves 16Rectifiers

SaturableReactors forDC Control

Full Wave Rectifier

DC CurrentTo Batteries

+

-

0

5

10

15

20

25

30

35

40

45

5 7 11 Total

Harmonic Order

Cu

rren

t D

isto

rtio

n, %

5A

10A

15A

20A

Rectifie rDC

Output


Resonance Concern

0.00

0.30

0.60

0.90

1.20

1.50

0 300 600 900 1200 1500

No Capaci tors

Impe

danc

e,

ΩΩ

Frequency (Hz)

Capaci tors

ResonancePoint


Avoiding Resonance Problems

0.00

0.30

0.60

0.90

1.20

1.50

0 300 600 900 1200 1500

2400 kvarCap Bank

2032 kvar4.7 th F ilter

Impe

danc

e,

ΩΩ

Frequency (Hz)

1200 kvarCap Bank


Measurement results -time varying characteristics

% Current TDD for a Daily Load Cycle

0

1

2

3

4

5

6

7

8

0 2 4 6 8 10 12 14 16 18 20 22

Hour

% C

urr

ent

TD

D

PCC 44 kV

PCC 480 V


Measurement results -statistical characteristics

0

1

2

3

4

5

6

7

8

9

0.00

00.

083

0.16

70.

250

0.33

30.

417

0.50

00.

583

0.66

70.

750

0.83

30.

917

1.00

0

Probability

% C

urr

ent

TD

D

2-Filters All-Filters

PCC 44 kV

The X-axis value represents the probability that the % Current

TDD will be greater than the Y-axis value

P(%TDD>8.0%) = 0.04

Probability that % TDD is Greater than the Limit for 2- Filters and for All-Filters


Evaluating ASD Loads -Example System for Analysis

480 Volt Bus

1500 kVAZ=6%

PCCShort Circuit Strength = 40 MVASCR = 40/1.2 = 33.33

ASD Load

Linear Load

Utility Distribution System

Power Factor Correction/Filters


ASD Harmonic Levels

30%

50%

70%

90%

110%

130%

0% 5% 10% 15% 20% 25% 30%

No Choke Choke

ASD kVA

Transformer kVA

I(t) at 33% kVA ratio

♦

◊◊

◊◊

◊◊

♦

♦ ♦◊◊

I(t) at 5% kVA ratio

Transformer5% Z

(on xfmr kVA)Choke3% Z

(on ASD kVA)ASD

I THD


ASD Harmonic Currents

0.05 0.06 0.07 0.08 0.09 0.10-400

-200

0

200

400

100 HP PWM ASD - No Choke/Filter

Time (Seconds)

Current (A

mps)

TYPE 1 Waveform100 HP PWM ASD - No Choke

Amps

TYPE 2 Waveform100 HP PWM ASD - 3% Choke

0.05 0.06 0.07 0.08 0.09 0.10-400

-200

0

200

400

Time (Seconds)

Current (A

mps)

Amps

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic Number

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Harm

on

ic Mag

nitu

de (%

of F

un

dam

ental)

ITHD = 80.6%

IRMS = 148.2 Amps

IFund = 115.4 Amps

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic Number

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Harm

on

ic Mag

nitu

de (%

of F

un

dam

ental)

ITHD = 37.7%

IRMS = 117.6 Amps

IFund = 110.1 Amps


Rules of Thumbu How much of the plant load can be ASDs without

exceeding IEEE 519 guidelines?

ASD Loading as % of Max Plant Load

To

tal P

lan

t 5t

h H

arm

on

ic C

urr

ent

(%o

f M

ax P

lan

t L

oad

Cu

rren

t)

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

0.0% 20.0% 40.0% 60.0% 80.0% 100.0%

Type 1 Current Waveform

Type 2 Current Waveform

IEEE 519 Limit (7%)


Designing for Cancellation

u Transformer connections can be used to getcancellation of harmonics from differentdrives.

ASD ASD

480 Volt Bus


Effect of Power Factor Correction

u Rules of thumb only apply if there are no powerfactor correction capacitors.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

1 3 5 7 9 11 13 15 17 19 21 23 25

HARMONIC NUMBER

MA

GN

IFIC

AT

ION

OF

HA

RM

ON

IC

CU

RR

EN

T F

RO

M A

SD

S 300 kVAr

500 kVAr700 kVAr

No Capacitor Bank


Power Factor Correction as Filters

u Power factor correction can be applied asharmonic filters to solve both the powerfactor problem and the harmonic problem.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

1 3 5 7 9 11 13 15 17 19 21 23 25

HARMONIC NUMBER

MA

GN

IFIC

AT

ION

OF

HA

RM

ON

IC

CU

RR

EN

T F

RO

M A

SD

S

500 kVAr Tuned Cap Bank

No Capacitor Bank


How many filter branches are needed?

ASD Loading as % of Max Plant Load

To

tal P

lan

t 11

th H

arm

on

ic C

urr

ent

(%o

f M

ax P

lan

t L

oad

Cu

rren

t)

0.0%

1.0%

2.0%

3.0%

4.0%

5.0%

6.0%

0.0% 20.0% 40.0% 60.0% 80.0% 100.0%

Type 1 or Type 2Current Waveform

IEEE Limit (3.5%)

u With a fifth harmonic filter, the evaluation will typicallybe dominated by the 11th harmonic component.


Filter design procedureu Make sure the filter is designed for harmonic loading from

other loads and the supplying power system, as well as thenonlinear loads being evaluated.

Characterize harmonicproducing loads

Characterize power systembackground voltage

distortion

Design minimum size filters tuned to individual harmonic frequencies,starting with the fifth harmonic

Calculate (simulate) harmonic currents

at PCC

Check against IEEE-519current limits

Another steprequired

Done


Another Alternative is the APLC

Controlsand

Gating SignalGenerators

IGBTPWM

Inverter

Is

If

IL

Main CustomerBus

NONLINEARLOAD

M

Interface Filter


Characteristics of other importantharmonic sources

u Dc drives

u Induction furnaces (heating processes)

u Arc furnaces


DC Drives

u Usually displacement power factor characteristicsare important (power factor correction oftenneeded)


Induction furnace loads

u Rectifier/inverter configurations often exhibitimportant interharmonic components (coupling ofoutput frequency to the input)


Arc furnace characteristics

u Unbalanced arc characteristics results in non-characteristic harmonic components (e.g. 3rd).

u Dynamic nature of the arc results in interharmoniccomponents and 2nd harmonic.


Semiconvertersu Concerns for even harmonics - makes filtering

very difficult

60 80 100 120-600

-400

-200

0

200

400

600

Firing Angle (Degree)

Current (A)

50 300 550 800 1050 0

50

100

150

200

250

300

350

Time (mS)

Firing Angle (Deg.) and Currents I1, I2, I4 (A)

I1

I2

I4

Alpha

50 300 550 800 1050 0

50

100

150

200

250

300

350

Time (mS)

Firing Angle (Deg.) and Currents I1, I5, and I7 (A)

I1

I5I7

Alpha


Cycloconverters

u Concern for interharmonics - interaction ofoutput frequency with the input frequency

u Traction power applications

u Mining, steel industry applications


Measurements to verify performance

Step 1 Step 2 Step 14

50 kVAr 50 kVAr 50 kVAr

Plant Load200 kVA0.85 dPF

1000 HPDC Drive

4160 V 480 V

1000 kVA5.5%Imp.

30 MVAX/R=12.0

PowerAnalyzer

Curr

ent P

robe A

Curr

ent P

robe B

Volta

ge P

robe B

Volta

ge P

robe C

Curr

ent P

robe C

Volta

ge P

robe A


Notching Concerns -example case

144 kV

25 kV Bus

other

loads

2 km 266 MCM

4.16 kV

10 MVA

7.87%

7.5 MVA

5.75%

10 km

1/0

other

loads

480 Volt bus4.16 kV

6000 hp

ASD

harmonic

filters

5,7,11

Motor Load

(650 hp)

PF Correction

Capacitors(160 kvar)

800 hp

0.5 uF

surge capacitors

Short Circuit Level =74 MVA

1500 kVA

4.7%

1500 kVA

4.7%

Voltage Waveform on 25 kV System During Drive Operation

0 5 10 15 20-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Time (mS)

Voltage (pu)

PASS Waveform


Summary - Industrial Concerns

u Variety of Nonlinear Loads

u Power factor correction results in resonanceconcerns

u Time varying nature of the harmonicsources

u Other special concerns (non-characteristicharmonics, interharmonics, notching)

u Filter design issues


Exercises forIndustrial facility evaluations

u Simple circuit to evaluate 519 complianceand filter design issues

u Develop rules of thumb

u Nonlinear load models

u Evaluate alternative solutions

u Filter design - effectiveness evaluation

IEEE P519AConcerns for CommercialFacilities

October, 1998

P519A Commercial Evaluations - 2

Commercial Facility Concerns

u Proliferation of electronic loads

u Distortion levels within facility vs. serviceentrance– transformer derating

– neutral currents

– harmonic cancellation from multiple sources

u Impact of ASDs for HVAC systems

u Standby generators - harmonic concerns


Commercial Facility HarmonicSources

u Electronic Loads (switch mode powersupplies)

u Fluorescent Lighting

u Adjustable Speed Drives (HVACApplications)


Switch Mode Power Supplies

Waveform and spectrumfor a circuit supplyingelectronic loads.


Fluorescent Lighting

Typical waveform and spectrum for lighting circuit withmagnetic ballasts


ASDs (HVAC Systems)

PWM Type ASDwith 3% input choke


How do the harmonic currents combine?


Commercial Facility Concerns

u Neutral currents

u Transformer derating requirements

u Standby generator rating requirements


Example of High Neutral CurrentPhase A (50 Amps)

Phase B (50 Amps)

Phase C (57 Amps)

Neutral (82 Amps)


Estimating neutral currents

u Neutral currents can be estimated based on the percentageof the load on the three phase circuit that consists of singlephase electronic equipment

rms Neutral Current in pu of rms Phase Current

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Electronic Load (% of Total Load)

Neu

tral

Cu

rren

t

Ineutralp

pIphaserms

nl

nlrms=

+3

0 5

1 0 5

2

2

.

.


Solutions to Overloaded Neutrals

u Increase the neutral conductor size

u Neutral for each phase

u Double neutral

u Third harmonic filter at each load

u Zig Zag transformer close to loads

u Active filter(s)


Transformer Derating Considerations

u Transformer derating requirements for harmonicsspecified in ANSI/IEEE C57.110-1991.

u Function of Transformer Eddy Current Losses

u Derating needs to be applied whenever the fullload current distortion exceeds 5%

u K-Factor transformers designed to supplynonlinear loads without derating


Transformer Derating - ANSI C57.110

Required Transformer Derating for Electronic Load as a Function of the Per Unit Eddy Current Losses

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

0% 5% 10% 15% 20%

Eddy Current Loss Factor (%)

Req

uir

ed D

erat

ing

(%

)

IP

K Prms

EC R

EC R

=+

+−

−

1

1 *

KI h

Ih

h

=∗∑

∑

2 2

2


Derating vs. Nonlinear Load

Required Derating for Conventional Transformer vs. Percent Electronic Load

84.0%

86.0%

88.0%

90.0%

92.0%

94.0%

96.0%

98.0%

100.0%

0% 20% 40% 60% 80% 100%

Percent Electronic Load

Req

uir

ed D

erat

ing

The required derating also depends on the percent of theload made up of electronic equipment (or other nonlinearloads).


K-Factor Transformers

K-Factor Transformers are designed to supplynonlinear loads without derating. The K-Factor definesthe level of current distortion that is acceptable.

Required Transform e r K-Factor vs P e rce n t Electronic Load

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0% 20% 40% 60% 80% 100%

Percent Electronic Load

K-F

acto

r KI h

Ih

h

=∗∑

∑

2 2

2


Standby Generator Requirementsu Harmonics can be more of a problem during backup

generator operation due to generator impedance.

u Calculate voltage distortion with generator operating andlimit to 5%

u Make sure harmonic currents do not exceed generatorcapabilities Automatic

TransferSwitch (ATS)

Line fromFeeder toBuilding

AirConditioningEquipment

AC

DC

DC

AC

Battery Systemwith

DC Disconnect

StaticBypass

Panelboard

UPS

ToLoad

GEN

Typical configurationof UPS system forcritical loads withbackup generator


Overall Facility Harmonic Levels

Example System to evaluate distortion levels at the PCC

Single PhaseElectronic

Load

1500 kVAZ=6%

Distribution System

Other120/208 V

Load

FlourescentLighting Load

HVACLoad

500 kVAZ=3%

Short Circuit Level = 50 MVA

Max. Demand Load = 1200 kVA

(300 kVA)


Voltage and Current Distortionwithout ASDs

Voltage Distortion at 480 volt Bus Caused by Facility Nonlinear Loads

0.00%

1.00%

2.00%

3.00%

4.00%

5.00%

6.00%

0% 5% 10% 15% 20% 25% 30% 35%

Electronic Load as % of Maximum Facility Load

Vo

ltag

e T

HD

Current Distortion (TDD) at PCC Caused by Facility Nonlinear Loads

0.00%

4.00%

8.00%

12.00%

16.00%

0% 5% 10% 15% 20% 25% 30% 35%

Electronic Load as % of Maximum Facility Load

Cu

rren

t D

isto

rtio

n (

TD

D)


Voltage and Current DistortionLevels with ASDs

Voltage Distortion at 480 volt Bus Caused by Facility Nonlinear Loads

0.00%

1.00%

2.00%

3.00%

4.00%

5.00%

6.00%

7.00%

8.00%

0% 5% 10% 15% 20% 25% 30% 35%

ASD Load as % of Maximum Facility Load

Vo

ltag

e T

HD

Current Distortion (TDD) at PCC Caused by Facility Nonlinear Loads

0.00%

4.00%

8.00%

12.00%

16.00%

20.00%

0% 5% 10% 15% 20% 25% 30% 35%

ASD Load as % of Maximum Facility Load

Cu

rren

t D

isto

rtio

n (

TD

D)


Summary - Concerns for 120/208 circuits

u Neutral conductors in 3-phase, 4-wire circuits servingelectronic loads should be rated for 170% of the maximumline current.

u Neutral conductors in fluorescent lighting circuits shouldbe rated for maximum line current.

u Transformers for step down to 120/208 that supplyelectronic loads should be derated for harmonics or shouldbe k-factor transformers

u Voltage distortion on 120/208 v secondary circuits will bedominated by electronic loads. Distortion should be below5% if total electronic load is below 25% of transformerrating.


Summary - Concerns for overall facility

u Voltage distortion in 480 v circuits will depend on thecumulative effect of office loads, fluorescent lighting, andHVAC equipment.

u Most commercial facilities should not exceed 519 limitsunless there is significant penetration of ASDs for HVACapplications or a large percentageof the load is electronic(some type of filtering could be needed in these cases).

u Retrofitting with electronic ballasts should not havesignificant impacts on building harmonic levels if ballastswith less than 30% current distortion are used.


Exercises forcommercial facility evaluations

u Simple circuit to evaluate effects of different loadcombinations

u Harmonic source representations for differenttypes of loads– electronic loads

– lighting

– asds

u Neutral currents, transformer derating, interactionevaluations

IEEE P519AConcerns for ResidentialSystems

October, 1998

P519A Residential Evaluations - 2

Harmonic concerns for circuitssupplying residential customers

u Characteristics of nonlinear loads– electronic loads

– ASD heat pumps and air conditioners

– compact fluorescents

– electric vehicle battery chargers

u System frequency response characteristics

u How to apply limits


Evaluate response to CFLsas an example

u CFLs are being promoted as part of energyconservation programs at many electricutilities.

u A recent study has concluded that low CFLpenetration levels can cause the feedervoltage distortion to exceed 5%.

u Previous studies have indicated that furtherinvestigation needs to be done.


Introduction - cont.

u Measurements were performed to identifyharmonic characteristics for different CFLs

u Transient models utilized to develop adetailed representation of typical loads.

u Harmonic simulations used to examinecumulative effect of CFLs.


High Distortion Electronic Ballast CFLs

Electronic High Distortion Lamp 3 Waveform

0 10 20 30 40-0.4

-0.2

0.0

0.2

0.4

Time (mS)

Current (A)

Electronic High Distortion Lamp 3 Spectrum

0 600 1200 1800 2400 30000.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Frequency (Hz)

Current (A)

Freq :Fund :THD :TID :TD :RMSh :RMSi :RMSfh:RMS :ASUM :TIF :IT :

60 0.0665344 144.009 0 144.009 0.0958158 0.0665344 0.116651 0.116651 0.313131 939.301 109.571

Harmonic Current Distortion of 140%


Low Distortion Electronic Ballast CFLs

Electronic Ballast, Low THD, Lamp 1 Waveform

0 10 20 30 40-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Time (mS)

Current (A) Electronic Ballast, Low THD, Lamp 1 Spectrum

0 600 1200 1800 24000.00

0.05

0.10

0.15

0.20

0.25

0.30

Frequency (Hz)

Current (A)


60 0.266187 33.8903 0 33.8903 0.0902114 0.266187 0.281058 0.281058 0.517387 628.985 176.781



Magnetic Ballast CFLsMagnetic Ballast, Low THD, Low PF, Lamp 1 Waveform

0 10 20 30 40-0.3

-0.2

-0.1

-0.0

0.1

0.2

0.3

Time (mS)

Current (A)

Magnetic Ballast, Low THD, Low PF, Lamp 1 Spectrum

0 240 480 720 960 12000.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

Frequency (Hz)

Current (A)


60 0.133063 14.4984 0 14.4984 0.019292 0.133063 0.134454 0.134454 0.16235 21.272 2.8601



Residential Circuit Example


Assumed Harmonic Spectrum

Harmonic Magnitude Angle

1 100.0% -11.53 82.0% -385 53.4% -62.57 31.6% -85.19 16.6% -103.311 8.2% -11113 1.5% -99.115 1.0% -88.417 0.6% -95.519 0.5% -109.521 0.3% -120.523 0.1% -107.525 0.1% -67.4

High Distortion ElectronicBallast CFLs Including Cancellation Effects


Distribution System StudiedSubstationNorth Bus

Feeder1 Feeder 2 Feeder 3 Feeder 5Feeder 4

44.8 MVA66/12kV

∆∆ ∆∆Y Y

600kVAr

600kVAr

1800kVAr

1800kVAr

1800kVAr

1200kVAr

1200kVAr

1800kVAr

1200kVAr1200kVAr

1200kVAr1200kVAr

6000 kVAr SwitchedSubstation Capacitor

Bank

31% of loads are commercial


System Frequency ResponseFrequency Scan at Feeder End

0 6 12 18 24

0

10

20

30

40

50

Harmonic Level

Impedance (ohms)

Light Load

Heavy Load

This case was selected to represent worst case realisticThis case was selected to represent worst case realisticcircuit conditions due to the system resonance at the fifthcircuit conditions due to the system resonance at the fifthharmonic.harmonic.


System Frequency ResponseComparison

Frequency Scan at Mid-Feeder

0 6 12 18 24

0

10

20

30

40

Harmonic Level

Impedance (ohms)

With non-linear and linear loads

With linear loads only


Effect of CFL Penetration

0%

4%

8%

12%

16%

Sub Mid End Sub Mid End Sub Mid End

% THD

50 W/House 100 W/House 150 W/House


Effect of CFL Type

0%

4%

8%

12%

16%

Sub Mid End Sub Mid End Sub Mid End

% THD

Magnetic Low THD Electronic

High THD Electronic


Summary of potential impactsu High penetration levels of CFLs that use

high distortion electronic ballasts can resultin unacceptable voltage distortion levels.

u CFLs with lower current distortion levels(30% or less) should not cause problems onthe feeder.

u Distortion levels are dependent on systemconditions (capacitance, representation ofelectronic loads, etc.)


Summary of Voltage Distortion

Case with No Resonance

0

2

4

6

8

10

12

14

16

0 50 100 150

CFL Load per Residence (W)

Feed

er V

olta

ge D

isto

rtio

n

Sub

End


Summary - cont.

Resonance Case

0

2

4

6

8

10

12

14

16

0 50 100 150

CFL Load per Residence (W)

Feed

er V

olta

ge D

isto

rtio

n

Sub

End


How to apply limits

u Limit harmonics from individual loads (IEC1000-3-2)

u Limit harmonics per resonance (verydifficult to enforce)

u Prevent resonance conditions on thedistribution system or control harmonics onthe distribution system


IEC Approach

u Limit harmonic currents for individual equipment(type testing).

u IEC 1000-3-2 for equipment up to 16 amps.

u IEC 1000-3-4 for equipment up to 75 amps(under development).

u This should limit overall harmonic distortionlevels to acceptable values.

u Procedure for evaluating customers supplied atmedium voltage and high voltage (1000-3-6).


IEC 1000-3-2 (General Loads)

u Equipment currentlimits for equipment upto 16 amps.

u Designed for 380 voltsystems (L-L).

u Class A equipment isgeneral purpose loads.

Maximum PermissibleHarmonic Harmonic Current

Order (in Amperes)Odd Harmonics

3 2.35 1.147 0.779 0.4

11 0.3313 0.21

15-39 0.15 x (15/n)Even Harmonics

2 1.084 0.436 0.3

8-40 0.23 x (8/n)


IEC 1000-3-2 (Lighting Loads)

u Class C equipment:

Maximum value expressed as a percentage of the fundamental input

Harmonic Order current of luminaires2 2%3 30% x PF5 10%7 7%9 5%

11-39 3%


IEC 1000-3-2 (Power Supply Loads)

u Class D equipment(special waveform).

u Note that relative limitsonly apply up to 300watts. Absolute limitapplies up to the 16 ampmaximum.

Relative Limit Maximum permissible Harmonic Order (mA/W) harmonic current (A)

3 3.4 2.35 1.9 1.147 1 0.779 0.5 0.411 0.35 0.33

13-39 linear extrapolation: see table for Class A 3.85/n equipment


Limits for electronic loadsClass D Harmonic Limits

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

0 500 1000 1500 2000 2500 3000 3500 4000

Power Rating (Watts)

Har

mo

nic

Lim

it (

% o

f ra

ted

cu

rren

t)

Third

Fifth

Seventh

Ninth

Eleventh


IEC 1000-3-4 (Loads up to 75 Amps)

u Under development.

u Limits dependent onshort circuit ratio.

u Initial draft set of limitsunder discussion.

I1/Ic < 1/35 I1/Ic < 1/170

Harmonic Order In/I1 (% ) In/I1 (% )

3 21.6 50.45 10.7 257 7.2 16.99 3.8 8.8

11 3.1 7.213 2 4.615 0.7 1.617 1.2 2.819 1.1 2.6


Summary-handling residential harmonics

u Where to apply limits?

u What should the limits be?

u Resonance concerns

u Controlling harmonics on the distributionsystem

u Effect of new load types (electric vehiclechargers)


Exercises for residential evaluation

u Example circuit, capacitor configurations

u Representation for residential customers– without nonlinear loads

– with nonlinear loads

u Characteristics of other large harmonicsources– asds

– electric vehicle chargers

IEEE P519AUtility Considerations

October, 1998

P519A Utility Considerations - 2

System Response Characteristics

u Voltage distortion is a result of the voltage drop createdacross the equivalent power system impedance.

u At 60 Hz, power systems are primarily inductive. Theequivalent inductance can be calculated:

Xsc= system short circuit reactance

f = power system fundamental frequency (60 Hz)

LX

feqsc=∗2π


Utility Considerations

u Controlling system voltage distortion levels

u Resonance considerations

u Utility equipment applications (e.g. SVC)

u Economic Considerations

u Telephone Interference

u Using rates to control harmonics?


Distribution System ResponseDistribution Substation Bus

Harmonic currents tend to flowfrom the harmonic source (nonlinear load)into the utility source because it is the lowest impedance.


Effect of Capacitors -Parallel Resonance

Capacitor increases harmonic current flow into the substation.

Distribution Substation Bus

Magnified Harmonic Current


Effect of Capacitors -Series Resonance

Distribution Substation Bus

Equivalent Circuit

Feeder branch and capacitor appear to be a series LC circuit.


Some Modeling Guidelines

u Substation transformer with short circuit equivalent on the high side.

u Overhead distribution lines can be modeled with series impedances.Cables must include shunt capacitance.

u Include all capacitor bank locations in the model.

u Model transformers and low side buses for customers with low voltagepower factor correction or filters.

u Include simple resistive representation for load or resistance with aseries inductance to represent step down transformers.

u Three phase model is needed to evaluate positive and zero sequenceharmonic components together. Otherwise, positive sequencerepresentation usually adequate.


Utility Equipment Applications

u Apply harmonic limits based on studies ofthe impact on the overall system voltagedistortion levels and other impacts (e.g.telephone interference)

u Economic evaluation of harmonic controllalternatives


Economics of controlling harmonicdistortion levels

u System perspective for the economicanalysis

u Alternatives– control at individual loads

– control at customer level

– control on the system

u Minimize total costs


How Can Harmonics be Controlled?

u Control at the equipment level (IEC 1000-3-2).

u Control at the customer level (IEEE 519 -current).

u Control on the utility system (IEEE 519 -voltage).

Some combination of these will probably be necessary.


Future of Harmonic Control

u Harmonics will be controlled at individual nonlinear loadswith better power supplies and active compensation.

u Harmonics will be controlled at the customer level withactive devices that can provide var control, harmoniccontrol, and some power conditioning(e.g. voltage sag ride through support).

u Harmonics will be controlled on the distribution systemalong with vars using active filter technology.

overview of the guide for applying harmonic limits on

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