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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
Harmonic ResonanceHarmonic Resonance
Initial configurationInitial configuration
Harmonic ResonanceHarmonic Resonance
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
Harmonic ResonanceHarmonic Resonance
-500
-250
0
250
500
40 80 120
Cur
rent
(A)
Time (ms)
Rectifier Linear load
Harmonic ResonanceHarmonic Resonance
FREQUENCY SCAN after installing the capacitor bankFREQUENCY SCAN after installing the capacitor bank
9
Harmonic ResonanceHarmonic Resonance
LL CC II
IICCIILL cc
2
SV Lω
=
2c
VQ Cω
=
c
ccO Q
SLC1 ω==ω
Harmonic ResonanceHarmonic Resonance
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..
.
Harmonic ResonanceHarmonic Resonance
Frequency response after installing the capacitor bankFrequency response after installing the capacitor bank
OhmsOhms
HzHz
Harmonic ResonanceHarmonic Resonance
Transient simulation after installing the capacitor bankTransient simulation after installing the capacitor bank
10
PCC voltage and currentPCC voltage and current
Harmonic ResonanceHarmonic Resonance
-25
-15
-5
5
15
25
40 80 120Time (ms)
Current (*10) Voltage
Capacitor bank currentCapacitor bank current
Harmonic ResonanceHarmonic Resonance
-4
-2
0
2
4
40 80 120
Capacitor bank
Cur
rent
(kA
)
Time (ms)
Harmonic ResonanceHarmonic Resonance
FREQUENCY SCAN after installing the passive filterFREQUENCY SCAN after installing the passive filter
Harmonic ResonanceHarmonic Resonance
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
Harmonic ResonanceHarmonic Resonance
Frequency response after installing the filterFrequency response after installing the filter
OhmsOhms
HzHz
With Capacitor BankWith Capacitor Bank
With FilterWith Filter
Harmonic ResonanceHarmonic Resonance
Transient simulation after installing the passive filterTransient simulation after installing the passive filter
PCC voltage and currentPCC voltage and current
Harmonic ResonanceHarmonic Resonance
-25
-15
-5
5
15
25
40 80 120Time (ms)
Current (*10) Voltage
Filter currentFilter current
Harmonic ResonanceHarmonic Resonance
-500
-250
0
250
500
40 80 120
Filter
Cur
rent
(A)
Time (ms)
12
Rectifier and linear load currentsRectifier and linear load currents
Harmonic ResonanceHarmonic Resonance
-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
ThreeThree--PhasePhase InductionInduction MotorMotor
Terminal voltagesTerminal voltages
ThreeThree--PhasePhase InductionInduction MotorMotor
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
ThreeThree--PhasePhase InductionInduction MotorMotor
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)
Single-phase fault Three-phase fault
14
Stator currentsStator currents
ThreeThree--PhasePhase InductionInduction MotorMotor
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)
Single-phase fault Three-phase fault
Electromagnetic torquesElectromagnetic torques
ThreeThree--PhasePhase InductionInduction MotorMotor
-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)
Single-phase fault Three-phase fault
Rotor speedsRotor speeds
ThreeThree--PhasePhase InductionInduction MotorMotor
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)
Single-phase fault Three-phase fault
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)
Phase 'a' Phase 'b' Phase 'c'
SingleSingle--phase fault phase fault -- Node SNode S
LineLine--toto--ground voltages ground voltages -- Node 2Node 2
0,0
0,5
1,0
1,5
0 40 80 120 160 200
Volta
ge (p
u)
Time (ms)
Phase 'a' Phase 'b' Phase 'c'
16
SingleSingle--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
2,4
0 40 80 120 160 200
Rea
l Pow
er (p
u)
Time (ms)
Phase 'a' Phase 'b' Phase 'c'
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
LineLine--toto--ground voltages ground voltages -- Node 2Node 2
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
Power demand per phase Power demand per phase -- Node 2Node 2
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
LineLine--toto--ground voltages ground voltages -- Node 2Node 2
0.0
0.5
1.0
1.5
2.0
0 2 4 6 8 10
Distance (km)
Phase APhase BPhase C
Parametric analysisParametric analysisSingleSingle--phasephase--toto--ground faultground fault
Power demand per phase Power demand per phase -- Node 2Node 2
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 2 4 6 8 10
D istance (km)
Phase APhase BPhase C
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%
Voltage Sag AssessmentVoltage Sag Assessment
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
Voltage Sag AssessmentVoltage Sag Assessment
22
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
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
Voltage Sag AssessmentVoltage Sag Assessment
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
Voltage Sag AssessmentVoltage Sag Assessment
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
Voltage Sag AssessmentVoltage Sag Assessment
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
Voltage Sag AssessmentVoltage Sag Assessment
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)
Mean fault duration (ms)
0
0.5
1
1.5
2
2.5
200 300 400 500 600 700 800 900 1000
No Protective DevicesOnly BreakersBreakers & Fuses (1Rec)Breakers & Fuses (2Rec)
25
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
200 300 400 500 600 700 800 900 1000
No Protective DevicesOnly BreakersBreakers & Fuses (1Rec)Breakers & Fuses (2Rec)
SARFISARFI--CBEMACBEMA
SARFISARFI--ITICITIC
SAR
FI (e
vent
/yr)
Mean fault duration (ms)
0
0.5
1
1.5
2
2.5
200 300 400 500 600 700 800 900 1000
No Protective DevicesOnly BreakersBreakers & Fuses (1Rec)Breakers & Fuses (2Rec)
Voltage Sag IndicesVoltage Sag Indices
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
Active FiltersActive Filters
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
Active Filters Active Filters -- 11
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)
Active Filters Active Filters -- 11
-400
-200
0
200
400
255 265 275 285 295Time (ms)
PCC voltage Load current
Active Filters Active Filters -- 22
PCC voltage and rectifier currentPCC voltage and rectifier current
-400
-200
0
200
400
255 265 275 285 295Time (ms)
PCC voltage Source current
Active Filters Active Filters -- 22
PCC voltage and source currentPCC voltage and source current
Active FiltersActive Filters
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)
Phase 'a' Phase 'b' Phase 'c'
29
Dynamic Voltage RestorerDynamic Voltage Restorer -- 11
Load voltagesLoad voltages
-400
-200
0
200
400
40 80 120 160 200
Volta
ge (V
)
Time (ms)
Phase 'a' Phase 'b' Phase 'c'
Dynamic Voltage RestorerDynamic Voltage Restorer -- 11
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)
Phase 'a' Phase 'b' Phase 'c'
Dynamic Voltage RestorerDynamic Voltage Restorer -- 22
Input voltagesInput voltages
-400
-200
0
200
400
0 40 80 120 160 200
Volta
ge (V
)
Time (ms)
Phase 'a' Phase 'b' Phase 'c'
Dynamic Voltage RestorerDynamic Voltage Restorer -- 22
Load voltagesLoad voltages
-400
-200
0
200
400
40 80 120 160 200
Volta
ge (V
)
Time (ms)
Phase 'a' Phase 'b' Phase 'c'
30
Dynamic Voltage RestorerDynamic Voltage Restorer -- 22
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 'a' Phase 'b' Phase 'c'
Dynamic Voltage RestorerDynamic Voltage Restorer -- 22
Phase Phase -- ‘a’‘a’
-400
-200
0
200
400
40 80 120 160 200
Volta
ge (V
)
Time (ms)
Load DVR Source
Dynamic Voltage RestorerDynamic Voltage Restorer -- 22
Phase Phase -- ‘b’‘b’
-400
-200
0
200
400
40 80 120 160 200
Volta
ge (V
)
Time (ms)
Load DVR Source
Dynamic Voltage RestorerDynamic Voltage Restorer -- 22
Phase Phase -- ‘c’‘c’
-400
-200
0
200
400
40 80 120 160 200
Volta
ge (V
)
Time (ms)
Load DVR Source