z Power Quality Studies Using Digital...

1

Power Quality Studies Using Power Quality Studies Using Digital SimulationDigital Simulation

Juan A. Martínez VelascoJuan A. Martínez VelascoUniversitatUniversitat PolitècnicaPolitècnica de de CatalunyaCatalunya

Barcelona, EspañaBarcelona, España

Montevideo, 12 de DiciembreMontevideo, 12 de Diciembre IntroductionIntroduction

TwoTwo mainmain concernsconcerns : : proliferationproliferation ofof contaminatingcontaminating equipmentequipment

proliferationproliferation ofof sensitivesensitive equipmentequipment

DisturbanceDisturbance causes are causes are wellwell identifiedidentified, , butbut therethere isis a a lacklack ofof experienceexperience onontheirtheir effectseffects andand how how toto quantifyquantify themthem

ThereThere isis also also anan increasingincreasing numbernumber ofoftechniquestechniques forfor mitigatingmitigating theirtheir effectseffects

ContentsContents

Power Quality DisturbancesPower Quality DisturbancesCauses, Effects, CharacterizationCauses, Effects, Characterization

EMTPEMTP--type toolstype toolsAlgorithms and CapabilitiesAlgorithms and Capabilities

The ATP packageThe ATP packagePower Quality Studies using the ATPPower Quality Studies using the ATPIllustrative ExamplesIllustrative Examples

DisturbancesDisturbances

Voltage sagsVoltage sags

HarmonicsHarmonics

FlickerFlicker

TransientsTransients

UnbalancesUnbalances

Other disturbances (notches, noise, ...)Other disturbances (notches, noise, ...)

2

VoltageVoltage SagsSagsHueco de tension en la fase A

0 50 100 150 200 250-15000

-10000

-5000

0

5000

10000

15000

Tiempo (mS)

Tension (V)

CausesCausesshortcircuitsshortcircuitslargelarge motor motor startupstartuptransformertransformer energizingenergizingsudden load variationssudden load variations

EffectsEffectsequipmentequipment triptripenergyenergy lostlost

HarmonicsHarmonicsConsumo no lineal

40.0 50.0 60.0 70.0 80.0 90.0 100.0-350.0

-280.0

-210.0

-140.0

-70.0

0.0

70.0

140.0

210.0

280.0

350.0

Tiempo (mS)

I (A)

CausesCausesnonlinearnonlinear loadsloadssaturable saturable reactancesreactancesvariable variable topologytopologyconvertersconverters

EffectsEffectsresonancesresonancesoverheatingoverheatingequipmentequipmentmaloperationmaloperation

FlickerFlickerTension fluctuante

0 100 200 300 400 500 600 700 800-400

-300

-200

-100

0

100

200

300

400

Tiempo (mS)

Tension (V)

CausesCausesarc arc furnacesfurnaceslargelarge motor motor startupstartup

EffectsEffectshuman human eyeeye problemsproblemsmaloperationmaloperation ofofsensitivesensitive equipmentequipment

TransientsTransientsConexion de una bateria de condensadores

20 30 40 50 60 70-800

-600

-400

-200

0

200

400

600

800

Tiempo (mS)

Tension (V)

CausesCausesshortcircuitsshortcircuitsswitchingswitching operationsoperationslightninglightning strokesstrokes

EffectsEffectsovercurrentsovercurrentsequipmentequipment agingagingandand breakdownbreakdown

3

UnbalancesUnbalancesConsumo desequilibrado

0 20 40 60 80-75

-50

-25

0

25

50

75

Tiempo (mS)

I (A)

CausesCausessinglesingle--phasephase loadsloadsfaultyfaulty threethree--phasephaseloadsloads

EffectsEffectsmaloperationmaloperationofof threethree--phasephaseequipmentequipment

Power Quality DisturbancesPower Quality Disturbances

TYPE OF DISTORSION DURATION METHOD OFCHARACTERIZING

Harmonics Steady state Harmonic spectrumHarmonic distortion

Phase-unbalance Steady state Unbalance factor

Interruptions ------------- Duration

Notches Steady state DurationMagnitude

Voltage flicker Steady stateVariation magnitudeFrequency of occurrenceModulation frequency

Sags/Swells TransientMagnitudeDurationRms vs. time

Oscillatory transients TransientWaveformPeak magnitudeFrequency range

Impulsive transients TransientRise timePeak magnitudeDuration

Noise Steady state/ Transient MagnitudeFrequency spectrum

Digital simulation can be usefulDigital simulation can be useful

to understand how disturbances propagateto understand how disturbances propagateto determine waveform distortionto determine waveform distortionto quantify the impact of disturbancesto quantify the impact of disturbancesto test mitigation techniquesto test mitigation techniquesto design power conditioning equipmentto design power conditioning equipmentfor educational applicationsfor educational applications

Benefits from Digital SimulationBenefits from Digital Simulation

Power quality simulations require Power quality simulations require the representation ofthe representation of

power componentspower componentsdisturbances (their stochastic nature, if necessary)disturbances (their stochastic nature, if necessary)protective devices (breakers, relays, protective devices (breakers, relays, reclosersreclosers, fuses), fuses)monitoring devices (characteristics, indices)monitoring devices (characteristics, indices)mitigation devices (including dispersed generation mitigation devices (including dispersed generation and energy storage)and energy storage)

What Should Be Represented?What Should Be Represented?

4

Power flowPower flowShortShort--circuit calculationscircuit calculationsFrequencyFrequency--domain domain (Harmonic Power Flow) (Harmonic Power Flow) TimeTime--domaindomain((ElectroMagneticElectroMagnetic Transients Programs)Transients Programs)

Types of Digital ToolsTypes of Digital Tools

Accurate modelingAccurate modelingMultiMulti--level modelinglevel modelingDevelopment of customDevelopment of custom--made modelsmade modelsNumerical stability to avoid runNumerical stability to avoid run--off problemsoff problemsMultiple run optionMultiple run option(parametric studies, statistical analysis)(parametric studies, statistical analysis)PostPost--processing capabilitiesprocessing capabilitiesInterface to external tools Interface to external tools -- Open systemsOpen systems

Capabilities of a Digital ToolCapabilities of a Digital Tool

EMTPEMTP--Type ToolsType Tools

CircuitCircuit--oriented tools based on a timeoriented tools based on a time--domain domain techniquetechniqueThe The Dommel’sDommel’s scheme: A combination of the scheme: A combination of the Trapezoidal rule and the Bergeron’s methodTrapezoidal rule and the Bergeron’s methodAdvantages: simplicity, numerical stabilityAdvantages: simplicity, numerical stabilityImportant aspectsImportant aspects

Basic solution methodsBasic solution methodsBuiltBuilt--in modelsin modelsModeling guidelinesModeling guidelinesApplicationsApplications

EMTP BuiltEMTP Built--in Modelsin ModelsBasic componentsBasic components

SingleSingle-- and multiand multi--phase lumped parameter phase lumped parameter componentscomponentsSingleSingle--phase distributed parameter componentsphase distributed parameter componentsIdeal and Ideal and saturablesaturable transformerstransformersIdeal switchesIdeal switchesIdeal sourcesIdeal sources

Overhead lines and insulated cablesOverhead lines and insulated cables(frequency(frequency--dependent models)dependent models)Power transformersPower transformersRotating machinesRotating machinesControl systemsControl systems

5

Modeling GuidelinesModeling Guidelines

Important aspectsNetwork equivalentsAggregated modelsFrequency dependent models

CIGRE Working Group 33-02 Brochure (1990)Four frequency rangesGuidelines for representing components for each frequency range

IEEE Working Group on Modeling and Analysis of System Transients using Digital Programs

Low Frequency Transients, Switching Transients, Fast Front Transients, Very Fast Front Transients, Power Electronics, Protection and ControlSpecial Publication in 1999

ClassificationClassification ofof FrequencyFrequency RangesRanges

GROUP

I

II

III

IV

FREQUENCY RANGE

0.1 Hz - 3 kHz

50 Hz - 20 kHz

10 kHz - 3 MHz

100 kHz - 50 MHz

SHAPE DESIGNATION

Low frequencyoscillationsSlow front

surgesFast front

surgesVery fast front

surges

REPRESENTATION MAINLY FOR

Temporaryovervoltages

Switchingovervoltages

Lightningovervoltages

Restrikeovervoltages

DiscussionDiscussion

InputInput datadataVeryVery oftenoften onlyonly approximatedapproximated valuesvaluesSpeciallySpecially forfor transientstransients ofof GroupGroup III III andand IVIV

TypeType ofof studystudyMaximumMaximum peakpeak systemsystem transientstransientsRepresentationRepresentation ofof losseslosses, , inductancesinductances andand capacapa--citancescitances

SystemSystem complexitycomplexityVeryVery detaileddetailed representationrepresentation, long , long simulationsimulationTheThe more more componentscomponents, , thethe higherhigher thethe probabilityprobabilityofof wrongwrong modelingmodeling

TheThe ATP ATP PackagePackage

ATPDrawATPDraw -- Interactive graphical preprocessor

Built-in editor for creating and correcting data filesSupport of Windows clipboard for metafile/ bitmapOutput of Windows metafile/bitmap file format or PS filesCopy/paste, rotate, import/export, group/ ungroup, undo,Print facilitiesHelp on lineIcon editor for user specified objectsMultiple windows

6

ATPDrawATPDrawTheThe ATP ATP PackagePackage

TPBIG : Tool for digital simulation of electromagnetic transients

Time- and frequency-domain techniquesSensitivity and statistical studiesTwo types of built-in capabilities

Simulation modulesSupporting routines

The ATP PackageThe ATP Package TheThe ATP ATP PackagePackage

TOP : Interactive graphical postprocessor

Handle data from various sourcesVisualize the data of interest in the form of tables and graphsView several plots simultaneously in multiple windowsDisplay selected data using windows and framesPerform mathematical operations on the various data objectsFormat the data display based on user preferencesExport the data being visualized

7

TOPTOP EMTP Applications in EMTP Applications in Power Quality StudiesPower Quality Studies

Modeling of power system components Modeling of power system components and sources of power quality problemsand sources of power quality problemsSimulation of the effects of power quality Simulation of the effects of power quality disturbancesdisturbancesAnalysis of mitigation techniquesAnalysis of mitigation techniquesPostPost--processing of resultsprocessing of resultsDevelopment of customDevelopment of custom--made simulation made simulation toolstools

ExamplesExamples

Harmonic resonance. Passive filtersHarmonic resonance. Passive filtersVoltage sag effects on threeVoltage sag effects on three--phase phase induction motors induction motors Voltage sag calculations. Parametric Voltage sag calculations. Parametric studiesstudiesStochastic prediction of voltage sagsStochastic prediction of voltage sagsActive filter simulationActive filter simulationDVR SimulationDVR Simulation

Harmonic ResonanceHarmonic Resonance

Diagram of the test caseDiagram of the test case

8


Initial configurationInitial configuration


PCC voltage and currentPCC voltage and current

-25

-15

-5

5

15

25

40 80 120Time (ms)

Current (*10) Voltage

Rectifier and linear load currentsRectifier and linear load currents


-500

-250

0

250

500

40 80 120

Cur

rent

(A)

Time (ms)

Rectifier Linear load


FREQUENCY SCAN after installing the capacitor bankFREQUENCY SCAN after installing the capacitor bank

9


LL CC II

IICCIILL cc

2

SV Lω

=

2c

VQ Cω

=

c

ccO Q

SLC1 ω==ω


IInn

IICnCnIILnLn

ExampleExample

HighHigh voltagevoltage : V = 110 : V = 110 kVkV ; ; Scc=2500Scc=2500 MVAMVA

TransformerTransformer : 110/11 : 110/11 kVkV, 20MVA, 8%, 20MVA, 8%

CapacitorCapacitor bankbank : 11 : 11 kVkV, 12 MVA, 12 MVA

HV+ HV+ TransformerTransformer = 20/2500 + 0.08 = 0.088= 20/2500 + 0.08 = 0.088

CapacitorCapacitor bankbank = 20/12 = 1.667= 20/12 = 1.667

n = =16670 088

4 35..

.


Frequency response after installing the capacitor bankFrequency response after installing the capacitor bank

OhmsOhms

HzHz


Transient simulation after installing the capacitor bankTransient simulation after installing the capacitor bank

10



-25

-15

-5

5

15

25

40 80 120Time (ms)


Capacitor bank currentCapacitor bank current


-4

-2

0

2

4

40 80 120

Capacitor bank

Cur

rent

(kA

)

Time (ms)


FREQUENCY SCAN after installing the passive filterFREQUENCY SCAN after installing the passive filter


IInn

IIfnfnIILnLn

f2n

f C1 L

ω=

( )CL2

fnfn XXn

C1 L =

ω=ω

1nnQ

XXV Q 2

2

CLC

2

f −=

−=

∞→nZ

LLff

CCff

11


Frequency response after installing the filterFrequency response after installing the filter

OhmsOhms

HzHz

With Capacitor BankWith Capacitor Bank

With FilterWith Filter


Transient simulation after installing the passive filterTransient simulation after installing the passive filter



-25

-15

-5

5

15

25

40 80 120Time (ms)


Filter currentFilter current


-500

-250

0

250

500

40 80 120

Filter

Cur

rent

(A)

Time (ms)

12

Rectifier and linear load currentsRectifier and linear load currents


-500

-250

0

250

500

40 80 120

Cur

rent

(A)

Time (ms)

Rectifier Linear load

VoltageVoltage SagSag StudiesStudies

-15

-10

-5

0

5

0 50 100 150 200 250

Phas

e A

ngle

Jum

p (D

eg)

Time (ms)

Phas

eju

mp

0

5

10

15

Volta

ge (k

V)

Ret

aine

dVo

ltage

Thre

shol

d

Duration-24

-12

0

12

24

Volta

ge (k

V)

Voltage sag characterizationVoltage sag characterization

Voltage sag characterizationVoltage sag characterizationRetained voltageRetained voltageDurationDurationPhase angle jumpPhase angle jumpPoints on wave (initiation and ending of sag)Points on wave (initiation and ending of sag)

Range of frequencies: low and midRange of frequencies: low and midLoad modeling issuesLoad modeling issuesModeling guidelines based on the type of Modeling guidelines based on the type of studies: deterministic, statisticalstudies: deterministic, statistical

Modeling GuidelinesModeling Guidelines

Although a constant impedance (i.e. a parallel R-L) model can be good enough in many cases, an accurate load model could also show voltage dependence, dynamic behavior and voltage sag sensitivity. In addition, for stochastic studies, the load model could incorporate a daily variation and a random nature.

Loads

Circuit breakers, reclosers and any type of disconnectorscan be represented as ideal switches. A more sophisticated model (non-linear resistance) is generally needed to represent fuses. Protective relay models should only incorporate delays and reclosing times.

Protection devices

Saturable models are needed when transformer energizationis the voltage sag cause; however, when the event has a different cause, e.g. a short-circuit, linear models can produce accurate enough results.

Transformers

Lumped-parameter models are usually acceptable; however, distributed-parameter models should be used to obtain very accurate simulation results with any voltage sag transient.

Lines and Cables

The most accurate representation should be deduced from the frequency response of the transmission system that is feeding the distribution network; however, a three-phase Thevenin equivalent model deduced from the short-circuit capacity will be good enough in most cases.

Network equivalentsMODELING GUIDELINESCOMPONENT

13

IMIM

LV LV networknetwork

Equivalent Equivalent ImpedanceImpedance

ThreeThree--PhasePhase InductionInduction MotorMotor

Voltage sag effectsVoltage sag effects

SS

Type of faultsType of faultssinglesingle--phasephase--toto--groundgroundthreethree--phasephase--toto--groundground

Calculation ofCalculation ofsource and motor stator currentssource and motor stator currentsvoltages at motor terminalsvoltages at motor terminalsrotor speedrotor speedelectromagnetic torqueelectromagnetic torque

Fault location : Node SFault location : Node S


Terminal voltagesTerminal voltages


0

80

160

240

0

80

160

240

0 400 800 1200 1600 2000

TAC

S -V

RM

_1A

(A

)TA

CS

-VR

M_1

A (

A)

Time (ms)

Single-phase fault Three-phase fault

Source currentsSource currents


0

200

400

600

0

200

400

600

0 400 800 1200 1600 2000

TAC

S -C

RM

_0A

(A

)TA

CS

-CR

M_0

A (

A)

Time (ms)


14

Stator currentsStator currents


0

100

200

300

0

100

200

300

0 400 800 1200 1600 2000

TAC

S -C

RM

_1A

(A

)TA

CS

-CR

M_1

A (

A)

Time (ms)


Electromagnetic torquesElectromagnetic torques


-600

-300

0

300

-600

-300

0

300

0 400 800 1200 1600 2000

UM

-1 -

TQG

EN

(A)

UM

-1 -

TQG

EN

(A)

Time (ms)


Rotor speedsRotor speeds


80100

120

140

160

80

100

120

140160

0 400 800 1200 1600 2000

UM

-1 -

OM

EGM

(A

)U

M-1

-O

MEG

M

(A)

Time (ms)


HV Equivalent : 110 kV, 1500 MVA, X/R = 10Substation Transformer: 110/25 kV, 10 MVA, 8%, Yd11Lines : Z1/2 = 0.61 + j0.39, Z0 = 0.76 + j1.56 Ω/km

110/25 kV 10 km

10 km

1

2

S

Voltage Sag CalculationsVoltage Sag Calculations

15

Calculation of voltage and power demand at Calculation of voltage and power demand at Node 2Node 2Type of faultsType of faults

threethree--phasephase--toto--groundgroundsinglesingle--phasephase--toto--groundground

Fault location : 4 km from the substationFault location : 4 km from the substationParametric studies consideringParametric studies considering

the fault locationthe fault locationsystem parameters (SCC, Transformer SC ratio) system parameters (SCC, Transformer SC ratio)

Voltage Sag CalculationsVoltage Sag CalculationsThreeThree--phase fault phase fault -- Node SNode S

LineLine--toto--ground voltages ground voltages -- Node 2Node 2

0,0

0,4

0,8

1,2

0 40 80 120 160 200

Volta

ge (p

u)

Time (ms)

Phase 'a' Phase 'b' Phase 'c'

ThreeThree--phase fault phase fault -- Node SNode S

Power demand per phase Power demand per phase -- Node 2Node 2

-0,1

0,4

0,9

1,4

1,9

0 40 80 120 160 200

Rea

l Pow

er (p

u)

Time (ms)


SingleSingle--phase fault phase fault -- Node SNode S


0,0

0,5

1,0

1,5

0 40 80 120 160 200

Volta

ge (p

u)

Time (ms)


16

SingleSingle--phase fault phase fault -- Node SNode S


-0,1

0,4

0,9

1,4

1,9

2,4

0 40 80 120 160 200

Rea

l Pow

er (p

u)

Time (ms)


Parametric analysisParametric analysis

Voltage and power demand per phase Voltage and power demand per phase -- Node 2Node 2

ThreeThree--phasephase--toto--ground fault at 4 km from the substationground fault at 4 km from the substation

0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10

Transformer SC ratio (% )

VoltageVoltage

PowerPower

Parametric analysisParametric analysisSingleSingle--phasephase--toto--ground fault at 4 km from the substationground fault at 4 km from the substation


0.00.20.40.60.81.01.21.41.6

0 2 4 6 8 10

Transformer SC ratio (%)

P hase AP hase BP hase C


Parametric analysisParametric analysisSingleSingle--phasephase--toto--ground fault at 4 km from the substationground fault at 4 km from the substation

0.0

0.5

1.0

1.5

2.0

2.5

0 2 4 6 8 1 0

Transformer SC ratio (%)

Phase APhase BPhase C

17

Parametric analysisParametric analysisThreeThree--phasephase--toto--ground faultground fault

Voltage and power demand per phase Voltage and power demand per phase -- Node 2Node 2

0.0

0.2

0.4

0.6

0.8

0 2 4 6 8 10

D istance (km)

VoltageVoltage

PowerPower

Parametric analysisParametric analysisSingleSingle--phasephase--toto--ground faultground fault


0.0

0.5

1.0

1.5

2.0

0 2 4 6 8 10

Distance (km)


Parametric analysisParametric analysisSingleSingle--phasephase--toto--ground faultground fault


0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 2 4 6 8 10

D istance (km)


Stochastic Prediction Stochastic Prediction of Voltage Sagsof Voltage Sags

The Monte Carlo methodThe Monte Carlo methodDiagram of the test systemDiagram of the test systemAssumptionsAssumptionsVoltage sag calculationsVoltage sag calculations

voltage sag probability densityvoltage sag probability densitynumber of voltage sagsnumber of voltage sagsvoltage sag indicesvoltage sag indices

Effect of protective devicesEffect of protective devices

18

Monte Carlo method: Every time the system is run, Monte Carlo method: Every time the system is run, fault characteristics are randomly generated using fault characteristics are randomly generated using the following distributions:the following distributions:

The fault location is selected by generating a uniformly The fault location is selected by generating a uniformly disdis--tributedtributed random number, since it is assumed that the prorandom number, since it is assumed that the pro--babilitybability is the same for any point of the distribution systemis the same for any point of the distribution systemThe fault resistance has a normal distributionThe fault resistance has a normal distributionThe initial time of the fault is uniformly distributed within a The initial time of the fault is uniformly distributed within a power frequency periodpower frequency periodThe duration of the fault has also a normal distributionThe duration of the fault has also a normal distributionDifferent probabilities are assumed for each type of faultDifferent probabilities are assumed for each type of faultA constant resistance model is used for representing the A constant resistance model is used for representing the fault impedancefault impedance

Loads are represented as constant impedancesLoads are represented as constant impedances

Prediction of Voltage SagsPrediction of Voltage Sags Fuse modelingFuse modeling

Extreme timeExtreme time--current characteristics of a fusecurrent characteristics of a fuse

0.001

0.01

0.1

1

10

100 1000 10000Current [A]

Tim

e [s

]

Minimum Melting TimeTotal Clearing Time

Fuse modelingFuse modeling

Current limiting fuse operation during a Current limiting fuse operation during a singlesingle--phasephase--toto--ground faultground fault

-0.5

0.0

0.5

1.0

1.5

0 10 20 30 40 50 60

Cur

rent

(kA

)

Time (ms)

-60-40

-20

0

20

40

Vol

tage

(kV

)

Circuit breaker modelingCircuit breaker modeling

OvercurrentOvercurrent relay timerelay time--current characteristicscurrent characteristics

0.01

0.1

1

10

100 1000 10000Current [A]

Tim

e [s

]

B1 (Ia=120A, K=16, n=2)B2 (Ia=120A, K=48, n=2)

19

Circuit breaker modelingCircuit breaker modeling

Circuit breaker currentsCircuit breaker currents

-1.5

-1.0

-0.5

0.0

0.5

1.01.5

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Cur

rent

(kA

)

Time (ms)

Breaker B2

-1.5-1.0

-0.5

0.0

0.5

1.01.5

Cur

rent

(kA

) Breaker B1

RecloserRecloser modelingmodeling

RecloserRecloser tripping characteristicstripping characteristics

0.01

0.1

1

10

100 1000 10000Current [A]

Tim

e [s

]

Fast characteristicSlow characteristic

RecloserRecloser modelingmodeling

RecloserRecloser tripping characteristicstripping characteristics

Time (ms)

T1 T2 Permanentlyopen

Cur

rent

(A)

Test systemTest system

HV equivalent: 110 kV, 1500 MVA, X/R = 10HV equivalent: 110 kV, 1500 MVA, X/R = 10Substation transformer: 110/25 kV, 8 MVA, 8%, YdSubstation transformer: 110/25 kV, 8 MVA, 8%, YdDistribution transformers: 25/0.4 kV, 1 MVA, 6%, Distribution transformers: 25/0.4 kV, 1 MVA, 6%, DyDyLines: ZLines: Z1/21/2 = 0.61 + j0.39, Z= 0.61 + j0.39, Z00 = 0.76 + j1.56 = 0.76 + j1.56 ΩΩ/km/km

21

R1 0.5 km

F3

0.25

km

0.25

km

60.25 km

8

7

30.5 km

0.5 km

F1

F24

0.25 km5

F4

B1

F5

20

TimeTime--current characteristics of current characteristics of protective devicesprotective devices

Tim

e [s

]

0.01

0.1

1

10

100 1000 10000

Current [A]

Fuse F3Fuse F4

Iscmax

OvercurrentRelay

(Breaker B1)

Recloser R1 - Fast

Recloser R1 - Slow

Some examplesSome examples

-3-2

-1

0

1

23

Rec

lose

r cur

rent

(kA

)

-3-2

-1

0

1

23

Bre

aker

cur

rent

(kA

)

0

6

12

18

100 300 500 700 900 1100 1300 1500 1700 1900 2100

BU

S3 v

olta

ge (k

V)

Time (ms)

ThreeThree--phase fault at Node 4 phase fault at Node 4 (Duration = 1.5 s, (Duration = 1.5 s, RRFF = 5 = 5 ΩΩ))

SingleSingle--phasephase--toto--ground fault at Node 6ground fault at Node 6(Duration = 1.5 s, (Duration = 1.5 s, RRFF = 5 = 5 ΩΩ))

-3-2

-1

0

1

23

Bre

aker

cur

rent

(kA

)

-3-2

-1

0

1

23

Rec

lose

r cur

rent

(kA

)

-3-2

-1

0

1

23

Fuse

3 cu

rren

t (kA

)

0

6

12

18

100 300 500 700 900 1100 1300 1500 1700 1900 2100

BU

S3 v

olta

ge (k

V)

Time (ms)

Some examplesSome examples Test system for Test system for voltage sag voltage sag assessmentassessment

5

4

7

2

13

9

10

1

3

6

11

14

8

Feeder A0.7265 1.3625

1.8625

0.7907 1.8743

Feeder B 0.5350

0.77

97

1.49

27

1.11

16

0.6896

0.7217

1.5291

0.5665

1.7393

0.8478

1.9485

0.60

84

0.99

14

0.59

80

1.56

50

B

B

F1 F3

F1F2

F3F1

F2

F3

F2

F2

F1

F1

F1F2

P

3.228112

2.60

43

2.73

35

2.8922

2.7508

2.40

39

21

Test systemTest system

TimeTime--current characteristics of protective devicescurrent characteristics of protective devices

0.01

0.1

1

10

10 100 1000 10000Current [A]

Tim

e[s

]

Iscmax

OvercurrentRelay

Breaker B

Fuse F3A

Fuse F1 Fuse F2

Fuse F3B

Four studiesFour studiesProtective devices do not operate; the fault conProtective devices do not operate; the fault con--ditiondition disappears before any device could opendisappears before any device could openCircuit breakers operate faster than fuses and their Circuit breakers operate faster than fuses and their relays have one relays have one reclosereclose operation, being the operation, being the recloreclo--sing time 200 ms; simulations are performed withsing time 200 ms; simulations are performed with--out including fuse modelsout including fuse modelsThe coordination between The coordination between overcurrentovercurrent relays and relays and fuses allows fuses to operate; curve labeled F3A in fuses allows fuses to operate; curve labeled F3A in Fig. 2b is selected for fuses F3, relays will have one Fig. 2b is selected for fuses F3, relays will have one 200 ms 200 ms reclosereclose operationoperationThe same as for the previous study, but allowing The same as for the previous study, but allowing feeder relays to have two 200 ms feeder relays to have two 200 ms reclosereclose operatioperati--onsons, and selecting fuse curve F3B, and selecting fuse curve F3B

Voltage Sag AssessmentVoltage Sag Assessment

Fault (random) characteristicsFault (random) characteristicsThe location was selected by generating a uniformThe location was selected by generating a uniform--lyly distributed random numberdistributed random numberThe fault resistance had a normal distribution, with The fault resistance had a normal distribution, with a mean value of 5 a mean value of 5 ΩΩ and a standard deviation of 1 and a standard deviation of 1 ΩΩ, for each faulted phase, for each faulted phaseThe initial time of the fault was uniformly The initial time of the fault was uniformly distribudistribu--tedted between 0.05 and 0.07 sbetween 0.05 and 0.07 sThe mean value of the fault duration was varied, The mean value of the fault duration was varied, and by default the standard deviation was 10% of and by default the standard deviation was 10% of the mean valuethe mean valueThe probabilities of each type of fault were The probabilities of each type of fault were

LG = 75%, 2LG = 17%, 3LG = 3%, 2L = 3%, 3L = 2%LG = 75%, 2LG = 17%, 3LG = 3%, 2L = 3%, 3L = 2%


Simulation resultsSimulation results1000 runs (assuming 12 faults per year 1000 runs (assuming 12 faults per year and 100 km of overhead lines, the and 100 km of overhead lines, the performance of the test system is performance of the test system is analyzed during 214 years)analyzed during 214 years)Number of sags per year at each nodeNumber of sags per year at each nodeDifferent results at MV and LV sidesDifferent results at MV and LV sidesSag severity compared to ITIC curveSag severity compared to ITIC curveVoltage sag mergingVoltage sag merging


22


Sags per year Sags per year –– Node 6, MV side, phase ANode 6, MV side, phase AMean fault duration = 600 ms, standard deviation = 60 msMean fault duration = 600 ms, standard deviation = 60 ms

0-50

ms

200-

250m

s40

0-45

0ms

600-

650m

s80

0-85

0ms

0%-10%

40%-50%

80%-90%

120%-130%

160%-170%

0

0.1

0.2

0.3

Acceptability CurvesAcceptability Curves

They are an empirical set of curves that represent the intensity and duration of bus voltage disturbances Standard curves

CBEMA : Computer Business Equipment Manu-facturers AssociationITIC : Information Technology Industry CouncilSEMI : Semiconductor Equipment and Materials International Group

0.0001 0.001 0.01 0.1 1 10 100 1000-100

-50

0

50

100

150

200

250

TIME IN SECONDS

PER

CEN

T C

HAN

GE

IN B

US

VOLT

AGE

8.33

ms

OVERVOLTAGE CONDITIONS

UNDERVOLTAGE CONDITIONS

0.5

CYC

LE

RATEDVOLTAGE

ACCEPTABLEPOWER

CBEMA CurvesCBEMA Curves Voltage Sag AssessmentVoltage Sag Assessment

Sags per year Sags per year –– Node 6, MV side, phase ANode 6, MV side, phase AMean fault duration = 600 ms, standard deviation = 60 msMean fault duration = 600 ms, standard deviation = 60 ms

020406080

100120140160180200

0.0001 0.01 1 100Time (s)

Volta

ge (%

)

23


Sags per year Sags per year –– Node 6, LV side, phase ANode 6, LV side, phase AProtective devices do not operateProtective devices do not operate

02 04 06 08 0

1 0 01 2 01 4 01 6 01 8 02 0 0

0 .0 0 0 1 0 .0 1 1 1 0 0T im e (s )

Volta

ge (%

)

N u m b er o ftrip s : 1 74


Sags per year Sags per year –– Node 6, LV side, phase ANode 6, LV side, phase ABreaker operation (Breaker operation (ReclosingReclosing interval = 200 ms)interval = 200 ms)

02 04 06 08 0

1 0 01 2 01 4 01 6 01 8 02 0 0

0 .0 0 0 1 0 .0 1 1 1 0 0T im e (s )

Volta

ge (%

)

1 2 9 e ve n tsN u m b er o ftrip s: 1 38


Sags per year Sags per year –– Node 6, LV side, phase ANode 6, LV side, phase AFuse operation (Fuse operation (ReclosingReclosing interval = 200 ms)interval = 200 ms)

02 04 06 08 0

1 0 01 2 01 4 01 6 01 8 02 0 0

0 .0 0 0 1 0 .0 1 1 1 0 0T im e (s )

Volta

ge (%

)

6 5 even tsN u m b e r o ftrip s: 1 22

O p en p ha sed u e to fu seo p era tion


Sags per year Sags per year –– Node 6, LV side, phase ANode 6, LV side, phase ABreaker and fuse operation (2 Breaker and fuse operation (2 reclosingreclosing intervals)intervals)

02 04 06 08 0

1 0 01 2 01 4 01 6 01 8 02 0 0

0 .0 0 0 1 0 .0 1 1 1 0 0T im e (s )

Volta

ge (%

)

5 0 e ve n tsN u m be r o ftrip s : 1 0 3

24

Average number of equipment trips per Average number of equipment trips per phase and year (Node 6 phase and year (Node 6 -- LV Level)LV Level)

194(0.91)

85(0.40)

82(0.38)

Breaker and fuse operation (change fuse F3)(tR = 200 + 200 ms)

159(0.74)

122(0.57)

121(0.56)

Breaker and fuse operation (tR = 200 ms)

500(2.34)

133(0.62)

111(0.52)

Breaker operation(tR = 200 ms)

176(0.82)

169(0.79)

64(0.30)

No operation1 s600 ms200 ms

Fault durationProtection system

Voltage Sag IndicesVoltage Sag IndicesIndices can provide a count of event frequency and Indices can provide a count of event frequency and duration, the undelivered energy during events, the duration, the undelivered energy during events, the cost and severity of the disturbancescost and severity of the disturbancesThe information deduced from the stochastic The information deduced from the stochastic proceproce--duredure is manipulated to obtain the number of trips per is manipulated to obtain the number of trips per year in combination with an acceptability curveyear in combination with an acceptability curveSARFISARFI (System Average RMS Variation Frequency (System Average RMS Variation Frequency Index) gives the average number of events over the Index) gives the average number of events over the assessment period (one year) per customer servedassessment period (one year) per customer served

nnss is the number of eventsis the number of eventsNNii is the number of customers experiencing an eventis the number of customers experiencing an eventNNTT is the number of customers servedis the number of customers served

T

n

ii

N

NSARFI

s

∑= =1

Voltage Sag IndicesVoltage Sag IndicesSince the index is derived from simulations and only events Since the index is derived from simulations and only events caused at the MV distribution level are analyzed, the number of caused at the MV distribution level are analyzed, the number of costumers that will experience an event at a load node is the costumers that will experience an event at a load node is the number of costumers served from that node; therefore, the number of costumers served from that node; therefore, the index for an entire system can be obtained as followsindex for an entire system can be obtained as follows

Two types of Two types of SARFISARFI indices: indices: SARFISARFI--xx and and SARFISARFI--CurveCurveIt is assumed that there is only LV demand and the number of It is assumed that there is only LV demand and the number of costumers served from every node is the same at every load costumers served from every node is the same at every load nodenode

T

nn

jjj

N

SARFINSARFI

∑ ⋅= =1

)(

n

n

jj

n

SARFISARFI

n

∑= =1

)(

Voltage Sag IndicesVoltage Sag Indices

LV nodesLV nodes

SAR

FI (e

vent

/yr)

Mean fault duration (ms)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

200 300 400 500 600 700 800 900 1000

No Protective DevicesOnly BreakersBreakers & Fuses (1Rec)Breakers & Fuses (2Rec)

SARFISARFI--9090

SARFISARFI--6060

SAR

FI (e

vent

/yr)


0

0.5

1

1.5

2

2.5

200 300 400 500 600 700 800 900 1000


25


LV nodesLV nodes

SAR

FI (e

vent

/yr)


0

0.5

1

1.5

2

2.5

3

200 300 400 500 600 700 800 900 1000


SARFISARFI--CBEMACBEMA

SARFISARFI--ITICITIC

SAR

FI (e

vent

/yr)


0

0.5

1

1.5

2

2.5

200 300 400 500 600 700 800 900 1000



The performance obtained with each protection The performance obtained with each protection scesce--narionario is not the same for every SARFIis not the same for every SARFI--x indexx indexSARFI values corresponding to different thresholds SARFI values corresponding to different thresholds can show different behavior: at load node 6, the best can show different behavior: at load node 6, the best SARFISARFI--90 performance is achieved when all 90 performance is achieved when all protecprotec--tivetive devices can operate, while the best SARFIdevices can operate, while the best SARFI--60 60 performance is achieved when fuses are savedperformance is achieved when fuses are savedSARFI values as a function of the mean fault duration SARFI values as a function of the mean fault duration do not show very significant changes for a given do not show very significant changes for a given protection system, except when the fault duration is protection system, except when the fault duration is about 1 second or longerabout 1 second or longerITIC equipment has a better performance that CBEMA ITIC equipment has a better performance that CBEMA equipment; however, when fuses operate the equipment; however, when fuses operate the perforperfor--mancemance is very similaris very similar

Active Active FiltersFilters

An active filter is a device for reducing An active filter is a device for reducing harmonic distortion by supplying harmonic distortion by supplying harhar--monicmonic componentscomponentsClassification : Parallel, Series, UnifiedClassification : Parallel, Series, UnifiedHybrid filters : Active + PassiveHybrid filters : Active + PassiveApplicationsApplicationsModelling guidelinesModelling guidelinesExampleExample

Active Active FiltersFilters

-400

-200

0

200

400

195 205 215 225 235Time (ms)

-400

-200

0

200

400

195 205 215 225 235Time (ms)

Harmonic Voltage SourceHarmonic Voltage SourceHarmonic Current SourceHarmonic Current Source

26

Active FiltersActive Filters

Scheme of the test systemScheme of the test system Detailed scheme of the power circuitDetailed scheme of the power circuit


PCC voltage and rectifier currentPCC voltage and rectifier current

-400

-200

0

200

400

255 265 275 285 295Time (ms)

PCC voltage Load current

Active Filters Active Filters -- 11

PCC voltage and source currentPCC voltage and source current

-400

-200

0

200

400

255 265 275 285 295Time (ms)

PCC voltage Source current


27

Rectifier and source currentsRectifier and source currents

015

30

45

60

0

15

30

4560

0 100 200 300 400 500 600

ILO

AD

A-D

RIV

EA (

Mag

)M

AIN

SA-J

OIN

TA (

Mag

)

Frequency (Hz)


-400

-200

0

200

400

255 265 275 285 295Time (ms)

PCC voltage Load current


PCC voltage and rectifier currentPCC voltage and rectifier current

-400

-200

0

200

400

255 265 275 285 295Time (ms)

PCC voltage Source current


PCC voltage and source currentPCC voltage and source current


Harmonic DistortionHarmonic Distortion

CASE Current RMS(A)

H1(A)

THD(%)

H5(%)

H7(%)

H11(%)

H13(%)

1Load 45.26 43.80 26.00 23.99 8.599 3.802 3.001

Source 52.43 52.41 2.739 0.427 0.961 0.306 0.270

2Load 67.43 49.39 92.96 73.70 52.90 16.43 8.357

Source 59.15 59.02 6.374 3.707 4.089 0.903 1.776

3Load 66.70 49.19 91.57 72.78 52.18 15.42 7.786

Source 58.72 58.13 14.10 9.324 9.944 0.968 1.185

28

Power CircuitPower Circuit

Converter+

Control

Vdc

n:1VSYS VLOAD

Passive Filter

Dynamic Voltage RestorerDynamic Voltage Restorer

DVR ConverterDVR Converter

Dynamic Voltage RestorerDynamic Voltage RestorerControl strategyControl strategy

Measure system voltages and currentsMeasure system voltages and currentsApply ‘Apply ‘αβαβ’ transform to voltages and currents, and ’ transform to voltages and currents, and obtain symmetrical componentsobtain symmetrical componentsObtain ‘Obtain ‘dqdq’ components’ componentsDetermine voltage compensation in ‘Determine voltage compensation in ‘dqdq’ values for ’ values for positive and negative sequencespositive and negative sequencesDeduce the values to be obtained at the converter Deduce the values to be obtained at the converter terminals, taking into account the passive filter terminals, taking into account the passive filter effecteffectObtain compensation voltages by applying antiObtain compensation voltages by applying anti--transforms (‘transforms (‘dqdq’ ‘’ ‘αβαβ’ ‘’ ‘abcabc’)’)Determine gate signals by means of a PWM control Determine gate signals by means of a PWM control strategystrategy

Dynamic Voltage RestorerDynamic Voltage RestorerTest systemTest system

Test casesTest casesSame voltage sag at the three phasesSame voltage sag at the three phasesVoltage sag in two phases, voltage swell in the Voltage sag in two phases, voltage swell in the third phase, with phase angle jumpsthird phase, with phase angle jumps

LoadLoad

FilterFilter ConverterConverter

SourceSource

Dynamic Voltage RestorerDynamic Voltage Restorer -- 11

Input voltagesInput voltages

-400

-200

0

200

400

0 40 80 120 160 200

Volta

ge (V

)

Time (ms)


29


Load voltagesLoad voltages

-400

-200

0

200

400

40 80 120 160 200

Volta

ge (V

)

Time (ms)



Voltages injected by the DVRVoltages injected by the DVR

-150

-100

-50

0

50

100

150

40 80 120 160 200

Volta

ge (V

)

Time (ms)



Input voltagesInput voltages

-400

-200

0

200

400

0 40 80 120 160 200

Volta

ge (V

)

Time (ms)



Load voltagesLoad voltages

-400

-200

0

200

400

40 80 120 160 200

Volta

ge (V

)

Time (ms)


30


Voltages injected by the DVRVoltages injected by the DVR

-300

-150

0

150

300

40 80 120 160 200

Volta

ge (V

)

Time (ms)



Phase Phase -- ‘a’‘a’

-400

-200

0

200

400

40 80 120 160 200

Volta

ge (V

)

Time (ms)

Load DVR Source


Phase Phase -- ‘b’‘b’

-400

-200

0

200

400

40 80 120 160 200

Volta

ge (V

)

Time (ms)

Load DVR Source


Phase Phase -- ‘c’‘c’

-400

-200

0

200

400

40 80 120 160 200

Volta

ge (V

)

Time (ms)

Load DVR Source

z Power Quality Studies Using Digital...

Documents

Transcript of z Power Quality Studies Using Digital...