1Georgia Tech

PSERC

PSERC SeminarMarch 5, 2002

SakisMeliopoulos

GeorgiaInstitute ofTechnology

© 2002 Georgia Institute of Technology

Power Quality Assessment via Physically Based Modeling

2Georgia Tech

PSERC

Power Quality

Design OptionsConfigurationGroundingOvervoltage Protection (arresters), Fault ProtectionUse of Steel/Aluminum conduit, Etc.

DisturbancesLightningSwitchingPower FaultsFeeder Energization inrush currents, Motor StartLoading imbalanceHarmonics, ResonanceEMI

Impact on End UserVoltage Distortion, Sags, Swells, Outages, Imbalances, Neutral Voltage, Stray Voltages, Resonance

3Georgia Tech

PSERC

Highly Susceptible SystemEnergy ManagementSystem

Distribution ManagementSystem

VariableSpeedDrives

Sensitive Load

StaticConditioner

CATV&Communications

Optical FiberCommunications

4Georgia Tech

PSERC

AcceptablePower

0.5

Cyc

le

Rated Voltage

8.33

ms

Overvoltage Conditions

Undervoltage Conditions

0.0001 0.001 0.01 0.1 1 10 100 1000Time (seconds)

Perc

ent C

hang

e in

Bus

Vol

tage

-100

-50

0

50

100

150

200

250

Power Quality is Defined in Terms Of Problems at the End Use

(a) deliver electric power service of sufficiently high quality so that the end-use equipment will operate within their design specifications and

(b) of sufficient reliability so that the operation of end-use equipment will be continuous.

Electric Power Quality Definition Ability of the system to

5Georgia Tech

PSERC

Physically Based Models Example:Example: Three Phase Power LineThree Phase Power Line

A1B1 C1

N1

38.4 feet

3.5'

S. POLE DISTRIB. LINE (TRIANGLE)/ 12 KV

Transmission Line Sequence Networks Close

3.495 + j 5.004

0.582 - j 121921.3 0.582 - j 121921.3

Positive Sequence Network

Negative Sequence Network

Zero Sequence Network

3.495 + j 5.004

0.582 - j 121921.3

5.688 + j 11.231

0.948 - j 295626.5

0.582 - j 121921.3

0.948 - j 295626.5

All Values in Ohms

Program WinIGS - Form OHL_REP2

Physically Based ModelPhysically Based Model Sequence Parameter ModelSequence Parameter Model

6Georgia Tech

PSERCComposite Model Object

Initialization

Re-Initialization

Time-Step

SVD/Numerical Stability

Phasor/QSSAnalysis

TransMatrix/SSSAnalysis

Schematic Icon

Visualization Module

Composite Model Object

NetworkSolver

SchematicEditor

VisualizationEngine

AC

FG

UI

Power System Simulator with “Physical” Models

7Georgia Tech

PSERC

=

),,,,(),,,,(

0 2

1

uyvyvfuyvyvfi

&&

&&

i Through Variables - Dependent Variablesv Across Variables - External Statesy Internal State Variablesu Controls - Independentz(t) Observation functions

z(t) = g0(v,y,u,t)

Universal Component Model Form --- ACF

Numerical IntegrationNumerical Integration

−−

+

+

=

)()(

)()(

))(),((

)()(

))(),((

)()(

0)(

2

12

1

2221

1211

htbhtb

tytv

Ftytvdiag

tytv

Ftytvdiag

tytv

aaaati

M

8Georgia Tech

PSERC

−−

+

+

=

)()(

)()(

))(),((

)()(

))(),((

)()(

0)(

2

12

1

2221

1211

htbhtb

tytv

Ftytvdiag

tytv

Ftytvdiag

tytv

aaaati

M

Simultaneous Solution - Time Interval (t-h,t)

ConnectivityConstraints

ConnectivityConstraints

Newton’sMethod

Newton’sMethod

0)()()()(()()()((

)( 2

1

=−+

+ htbtxtBtxdiag

txtBtxdiagtAx

M

x(t)x(t)

Component Model

9Georgia Tech

PSERC

Universal Quadratic Component Model

kkdk VjbguVjbgI ~)(~)(~1 +++=

dkPugugu −+= 2120

220 kVu −=

Frequency Domain Example:Frequency Domain Example:Single Phase Constant Power LoadSingle Phase Constant Power Load

g + j b u1 ( g + j b )

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PSERC

Universal Quadratic Component Model

Time Domain Example:Time Domain Example:SaturableSaturable Inductor ModelInductor Model

7

00 ))(()(

λλ titi =

dttdtv )()( λ

=

11Georgia Tech

PSERC

Universal Quadratic Component Model

7

00 ))(()(

λλ titi =

))()()(()( 10

0 tytitiλλ

= ))()(()(0

21 λλ ttyty =

))()(()(0

32 λλ ttyty =

))()()(()(00

5 λλ

λλ ttty =

))()(()(0

43 λλ ttyty =

))()(()(0

54 λλ ttyty =

dttdtv )()( λ

=

Time Domain Example:Time Domain Example:SaturableSaturable Inductor ModelInductor Model

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PSERC

B U S 10 B U S 20 B U S 30 B U S 40

G

V

V

V

A

A

A

V

V

V

A

A

A

A

A

A

A

L R

Earth Current / GPR / Effects on Power QualityEarth Current / GPR / Effects on Power Quality

P r o g r a m X F M - P a g e 1 o f 1

c : \w m a s te r \ ig s \d a ta u \g p r _ e x 0 1 - M a y 1 4 , 2 0 0 0 , 0 1 :5 1 :4 4 .0 0 0 0 0 0 - 2 0 0 0 0 0 .0 s a m p le s /s e c - 2 4 0 0 0 S a m p le s

4 4 .0 2 0 4 4 .0 4 0 4 4 .0 6 0 4 4 .0 8 0 4 4 .1 0 0

-3 .9 5 2

-3 .1 4 6

-2 .3 3 9

-1 .5 3 2

-7 2 5 .8 m

8 0 .7 6 m

8 8 7 .3 m

1 .6 9 4

2 .5 0 1 P h a s e _ A _ L in e _ C u r r e n t_ _ B U S 1 0 (k A )

-1 .6 2 5

-1 .2 9 1

-9 5 6 .1 m

-6 2 1 .5 m

-2 8 6 .8 m

4 7 .8 1 m

3 8 2 .5 m

7 1 7 .1 m

1 .0 5 2 E a r th _ C u r r e n t_ _ G r o u n d _ a t_ B U S 2 0 (k A )

Important IssuesGround Potential Rise Changes Neutral Voltage

Customer Voltage is ProportionalTo Phase to Neutral Voltage

Grounding and BondingSingle Ground/Multi GroundTransmission Interconnection

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PSERC

Grounding & Power QualityGrounding & Power QualityExample: Voltage Sags & SwellsExample: Voltage Sags & Swells

0 2 3 4 5 6

6

5

4

3

2

1

100/17395/164

90/155

85/147

80/138

75/129

70/121

65/11757/100

X0/X1

R0/X1

1

alnoLG

actualLG

g VVC min=

Coefficient ofGrounding

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PSERC

Voltage Sags & Swells During a Ground Fault

Transmission Line Voltage & Current Profile Close

0.00 0.75 1.50 2.25 3.00 3.75Distance (miles)

-8.00

-6.00

-4.00

-2.00

0.00

2.00

Volta

ge (k

V)

_A_B_C_N

Absolute Deviation

Remote Earth Neutral Ground

Voltage Reference

6.92 Volt age Current

Displayed Quantity Nominal Voltage

kV (L-L)

Plot ModeDistribution Line, 12 kV

1.250

-5.810

Distance

_A

0.3334

0.9744

_B

_C

0.00_N

BUS40 BUS50Program IGS - Form CODE_102A

B U S 10 BU S20 BU S30 BU S40

G

V

V

V

A

A

A

V

V

V

A

A

A

A

A

A

A

L R

CommentsThe Graph Illustrates Voltage Sags and Swells During a Phase A to Ground Fault at Mile Post 1.6 of the Line.Data of the Figure can be used to generate nomograms and statistical distributions of voltage sags and swells for a specific location (IEEE P1346)

Voltage Sags and Swells Are Dependent on Design Parameters (Neutral Size, Grounds, etc.)

15Georgia Tech

PSERC Close

Distribution Line, 12 kV

Update 0.00 0.040 0.080 0.12 0.16 0.20Distance from BUS40 (miles)

60.0

80.0

100

120

140

160

Coe

ffici

ent o

f Gro

undi

ng (%

)

0.00

600

1200

1800

2400

3000

GPR

(Vol

ts)

Phase BPhase C

G.P.R.Symmetric

Circuit Fault Type

0.1000

87.98

1844

Distance

Coefficent of

GPR

BUS50BUS40

L-N L-GCircuit # 1

Coefficient of Grounding

Faulted Phase A B C Nominal L-L Voltage (kV) 12.0

Definition of Unfaulted Phase Voltage L-N L-G Absolute

GroundingPhase B

125.3Phase C

Coefficent ofGrounding

83.47

Symmetric Coeff.of Grounding

Program W inIGS - Form COEF_GR

CommentsThe Graph Illustrates the Coefficient of Grounding Using Physically Based Modeling

Note Each Phase is Experiencing a Different Overvoltage(Symmetrical Components Predict Identical Overvoltages)

Coefficient of Grounding for Ground Faults Coefficient of Grounding for Ground Faults Along the LineAlong the Line

16Georgia Tech

PSERC

Stray Voltages and CurrentsSky Wire

HA

HB

HC

I sky

neutralI

Neutral

Counterpoise Ground Rod Ground Rod

I earth~

LA

LB

LC

Ground Mat

~

~

counterpoiseI~

CATV

CommentsSingle Phase Loads Generate Current Flow in the Parallel Path of Neutral and Soil/Grounds

Typical Distribution 50-70% in Neutral, 50-30% in Soil/Grounds

Neutral Voltage Typically 2 to 12 Volts

Properly Designed Systems can Practically Eliminate Stray VoltagProperly Designed Systems can Practically Eliminate Stray Voltages and Currentses and Currents

17Georgia Tech

PSERC

1.0 V1.0 V1.0 V0.9 V0.8 V0.9 V25,F,Y,Y

1.6 V1.7 V1.6 V1.5 V1.4 V1.5 V25,F,Y,N

1.8 V2.0 V1.9 V1.5 V1.3 V1.6 V25,F,N,Y

2.8 V3.0 V2.9 V2.6 V2.3 V2.6 V25,F,N,N

2.8 V1.2 V1.2 V0.9 V0.7 V1.0 V25,1/2,Y,Y

1.6 V1.8 V1.7 V1.5 V1.3 V1.5 V25,1/2,N,Y

2.3 V2.7 V2.5 V1.7 V1.2 V1.9 V25,1/2,Y,N

3.2 V3.6 V3.5 V2.7 V2.2 V2.9 V25,1/2,N,N

1.1 V1.3 V1.2 V0.9 V0.7 V1.0 V25,1/3,Y,Y

1.7 V1.8 V1.8 V1.5 V1.3 V1.5 V25,1/3,Y,N

2.7 V3.4 V3.1 V1.9 V1.1 V2.2 V25,1/3,N,Y

3.7 V4.3 V4.0 V2.8 V2.1 V3.1 V25,1/3,N,N

XFMR3_NXFMR5_NXFMR9_NXFMRA_NPOLE2_NXFMR2_NCase/NeutralPoint

Example Parameters Affecting Stray Voltages

18Georgia Tech

PSERC

Harmonic ResonanceHarmonic Resonance CommentsHarmonic Resonance Has Multiple Modes and Resonance Frequencies

System May Be Vulnerable When Resonance Coincides with a Harmonic Frequency

When Problem is Known, Solution is Very Simple - Detuning

Close

0.00 400 800 1200 1600 2000Frequency (Hz)

0.100

1.00

10.0

100

1000

Mag

nitu

de (O

hms)

Impedance Magnitude

Positive Sequence Frequency Scan at Bus BUS70/ P

0.00 400 800 1200 1600 2000Frequency (Hz)

-225

-150

-75.0

0.00

75.0

150

Phas

e (D

eg)

Impedance Phase

Table

872.1

Magnitude(Ohms)

Phase(Degrees)

Frequency(Hz)

334.5

Frequency(Hz)

Program WinIGS - Fo rm FSCAN_RES

Close

0.00 400 800 1200 1600 2000Frequency (Hz)

1.00

10.0

100

1000

Mag

nitu

de (O

hms)

Impedance Magnitude

Frequency Scan At 2-Node Port: BUS70_A to BUS70_N

0.00 400 800 1200 1600 2000Frequency (Hz)

-80.0

-40.0

0.00

40.0

80.0

120

Phas

e (D

eg)

Impedance Phase

Table

163.4

Magnitude(Ohms)

Phase(Degrees)

Frequency(Hz)

334.5

Frequency(Hz)

5.501

334.5

Program WinIGS - Fo rm FSCAN_RES

BUS30 BUS40

BUS50

BUS60

BUS70

BUS80

BUS90

BUS100

BUS110BUS1201 2

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PSERC

Monte Carlo SimulationEffects Analysis

Select (at Random) a Set of Parameters

Perform Transient Analysis

Characterize “Power Quality” at Customer

Evaluate the Effects

Repeat Process Many-Many Times

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PSERC

NA B C

S

wf

D

S

S

dt

Lightning Caused Voltage Sags, Swells and OutagesLightning Caused Voltage Sags, Swells and Outages

21Georgia Tech

PSERC

Physically Based Model of Distribution LinePhysically Based Model of Distribution Line

22Georgia Tech

PSERC

1

1

2

2

3

3

4

4

5

5

6

6

7

7

8

8

9

9

10

10

11

11

A A

B B

C C

D D

E E

F F

G G

Advanced Grounding Concepts / WinIGS

Scale (feet)0' 20' 40' 60'

Grid Spacing: 100.0 ftModel B X

Z

Lightning Shielding Analysis, 12 kA CrestLightning Shielding Analysis, 12 kA Crest

23Georgia Tech

PSERC

1

1

2

2

3

3

4

4

5

5

6

6

7

7

8

8

9

9

10

10

11

11

A A

B B

C C

D D

E E

F F

G G

Advanced Grounding Concepts / WinIGS

Scale (feet)0' 20' 40' 60'

Grid Spacing: 100.0 ftModel B X

Z

Lightning Shielding Analysis, 45 kA CrestLightning Shielding Analysis, 45 kA Crest

24Georgia Tech

PSERC

Lightning Caused Voltage Sags, Swells and Lightning Caused Voltage Sags, Swells and OutagesOutagesSuccessful Arrester Operation is Counted as Successful Arrester Operation is Counted as SuccessSuccess

Effects of Grounding and Protection

25Georgia Tech

PSERC

$1 per foot$2Copper Conductor(#4 or #6)

-$3Connector

-$2Ground Rod Coupler

$30$10Ground Rod

$150 (per three phases)

$35Arrester

InstallationCost of Material

Item

Cost Benefit AnalysisCost Benefit AnalysisEXAMPLE FEEDERFeeder Length: 40 milesLightning Activity: 5 per sqr kmFeeder Design: 25 kV, Steel Arms, Arresters 1800ftPole Ground: Single Ground RodSoil: 500 ohm.meters, 20% variation

IMPROVEMENTSArresters: at 600 ftPole Ground: Two Ground RodsPERFORMANCEFrom 20 operations to 3COSTArresters: $59,670Grounds: $29,484

26Georgia Tech

PSERC

L1

N

G

L1

N

G

Time or Frequency

Vol

tage

Physically Based Integrated Model Approach

Probabilistic Approach to Power Quality AnalysisProbabilistic Approach to Power Quality AnalysisPQ CharacterizationPQ Characterization

Design Options for PQ EnhancementDesign Options for PQ Enhancement

27Georgia Tech

PSERC

Frequency (Hz)

Volta

ge (k

V)

106 105 103104 10102 0.11 0.01

1.0

2.0

3.0

4.0

Transformer

Arrester Fuse

Ground Rods

L1

L2N

G

Ground Loop

SensitiveElectronicEquipment

Probabilistic Approach to Power Quality Probabilistic Approach to Power Quality AnalysisAnalysis

PQ CharacterizationPQ Characterization

Design Options for PQ EnhancementDesign Options for PQ Enhancement

Statistical Distribution of Voltage Sags/Swells

28Georgia Tech

PSERCConclusions

You Can Do a Lot More with Physically Based Modeling

Disadvantage: More Complex Models

Advantage: Provides the Interrelationship Between Design Parameters and Performance:

Cost-Benefit Analysis