detecting circuit breaker status errors in substations · pdf file1 detecting circuit breaker...

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Detecting Circuit Breaker Detecting Circuit Breaker Status Errors in Substations Status Errors in Substations

Ali AburAli AburNortheastern UniversityNortheastern University

(Project was completed at TAMU)(Project was completed at TAMU)

TeleTele--seminarseminarMay 2, 2006, 2:00May 2, 2006, 2:00--3:00 p.m. Eastern Time3:00 p.m. Eastern Time

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OutlineOutlineIntroductionIntroductionMotivation and ObjectivesMotivation and ObjectivesMethod 1: Two Stage State Method 1: Two Stage State EstimationEstimationMethod 2: Single Stage SE with Method 2: Single Stage SE with Reduced Size ModelReduced Size ModelRemarks and ConclusionsRemarks and Conclusions

33

IntroductionIntroductionSubstations are rapidly acquiring advanced Substations are rapidly acquiring advanced computational and communication capabilities.computational and communication capabilities.EMS functions do not model substations in detail EMS functions do not model substations in detail due to the complexity of the model. due to the complexity of the model. Certain measurements that are available at the Certain measurements that are available at the substation can not be used by the central EMS substation can not be used by the central EMS functions.functions.Such measurements can be readily processed at Such measurements can be readily processed at the substation to aid topology error detection. the substation to aid topology error detection.

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MotivationMotivationThere are no well established and commonly There are no well established and commonly implemented methods to detect, identify and implemented methods to detect, identify and eliminate topology errors. eliminate topology errors. Computational and communication capabilities Computational and communication capabilities at the substation can be exploited for this at the substation can be exploited for this purpose.purpose.Measurements which would otherwise be Measurements which would otherwise be discarded, could be used if processing were discarded, could be used if processing were done at the substation.done at the substation.

55

Project ObjectivesProject ObjectivesMake use of all available measurements at Make use of all available measurements at the substation.the substation.Take advantage of CPU at the substation to Take advantage of CPU at the substation to improve EMS functions at the control center.improve EMS functions at the control center.Specifically, develop ways of detecting and Specifically, develop ways of detecting and identifying substation breaker status errors, identifying substation breaker status errors, so that State Estimation results will be more so that State Estimation results will be more reliable and accurate.reliable and accurate.

66

Effect of Breaker Status ErrorsEffect of Breaker Status Errorson State Estimation on State Estimation

Analog MeasurementsPi , Qi, Pf , Qf , V, I, θkm

Circuit Breaker Status

State Estimator

Bad DataProcessor

NetworkObservabilityCheck

Topology Processor

V, θ

Assumed or Monitored

Link to be developed

77

Types of Topology ErrorsTypes of Topology ErrorsBus ReconfigurationBus Reconfiguration

1

2

3

4

3

4

1

2

4

31

2431

2

88

Types of Topology ErrorsBus Split / Merger

Types of Topology ErrorsTypes of Topology ErrorsBus Split / MergerBus Split / Merger

1

2

3

4

1

2

3

4

Load

Load

Load

Load 3

41

2

3

4

12

99

Types of Topology ErrorsBranch In/(Out of) Service

Types of Topology ErrorsTypes of Topology ErrorsBranch In/(Out of) ServiceBranch In/(Out of) Service

1 2 Out of Service

Out of ServiceLine charging C

Out of ServiceLine charging C

1

1

2

2

1010

Proposed TwoProposed Two--Stage ApproachStage Approach

Stage1: Identify the suspected buses by Stage1: Identify the suspected buses by normalized residuals of measurementsnormalized residuals of measurements

Stage2: Introduce detailed models of Stage2: Introduce detailed models of suspected substations. Repeat the SE suspected substations. Repeat the SE process using the expanded system process using the expanded system model.model.

1111

TwoTwo--stage State Estimatorstage State Estimator

MeasurementProcessor

CB/SwitchCB/SwitchStatus InfoStatus Info

1.Stage State1.Stage StateEstimatorEstimator

SuspectSuspectTopology Topology

Error ?Error ?

SubstationSimulator

YYNN

Next ScanNext Scan


AnalogAnalogMeasurementsMeasurements

Estimated Status Estimated Status of CB/Switchesof CB/Switches

1212

Estimation of Breaker StatusEstimation of Breaker StatusEstimation procedure:Estimation procedure:

Identification of error location (substation).Identification of error location (substation).Use of measurement residualsUse of measurement residuals

Insert detailed substation model into SE.Insert detailed substation model into SE.Model the substation using breaker / tie switch Model the substation using breaker / tie switch

models and all internal measurementsmodels and all internal measurements

Estimate the status for all breakers.Estimate the status for all breakers.Concur the most likely substation configuration Concur the most likely substation configuration

based on the estimated status of breakers and based on the estimated status of breakers and report it to the control center.report it to the control center.

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Measurement EquationsMeasurement Equations

Where:Where:

zz is the measurement vectoris the measurement vector;;h(.) is the measurement function;h(.) is the measurement function;x is the state vector;x is the state vector;f is the vector of breaker flows;f is the vector of breaker flows;e is the measurement noise vector.e is the measurement noise vector.

efxhz += ),(

1414

1

2

4

Load

33

Load4

12

: breaker flow

f1 f2

f3

f5 f6

f4

f7 f8

f1=0f3=0f6=0

f = [f1 , .., f3 ,.., f8 ]

Model Used in Stage II:

Model Used in Stage I:

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Integrating Breakers into the Integrating Breakers into the Measurement EquationsMeasurement Equations

efMxHz +⋅+Δ⋅=Δif the measurement i is an injection:

⎪⎩

⎪⎨

⎧−=

otherwise 0 jbreaker theof end-from at the isinjection theif 1

jbreaker theof end- toat the isinjection theif 1

ijM

⎪⎩

⎪⎨

⎧−=

otherwise 0 jbreaker theof end-from at the is flow theif 1

jbreaker theof end- toat the is flow theif 1

ijM

if the measurement i is a power flow:

1616

State EstimatorState Estimator



SuspectSuspectTopology Topology

Error ?Error ?

NN

Next ScanNext Scan


LAV EstimatorLAV Estimator(Automatic rejection of BD)(Automatic rejection of BD)

Error ProcessingError Processing

Normalized residuals of Normalized residuals of rejected measurementsrejected measurements

Selection of suspect Selection of suspect

substationssubstations

1717

CB Status EstimatorCB Status Estimator

MeasurementMeasurementProcessorProcessor




Estimated Status Estimated Status of CB/Switchesof CB/Switches

Modified LAV EstimatorModified LAV Estimator•• Substation Model with CBsSubstation Model with CBs•• Flows through CBsFlows through CBs

•• Zero injections at inter. nodesZero injections at inter. nodes

vv11

vv22

vvnn

ff11

ffkk

X =X =

AugmentedAugmentedStateState

SubstationSubstationSimulatorSimulator

XX

1818

Example: IEEE 30 Bus SystemExample: IEEE 30 Bus System

1919

Substation Configuration of Bus Substation Configuration of Bus 1515

15

31

14 18

32 33 34 35

Closed Open

12 23

2020

Estimated State of Circuit Estimated State of Circuit Breaker Breaker

Circuit Breaker Normalized P Flow Normalized Q Flow Estimated Status

15-32 -85.51 -23.39 Closed

15-33 7.63 -0.36 Closed

15-34 0.00 0.00 Open

15-35 0.00 0.00 Open

31-32 0.00 0.00 Open

31-33 0.00 0.02 Open

31-34 4.36 -7.38 Closed

31-35 -4.36 7.39 Closed

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Weakness of the method:Weakness of the method:How to identify the suspect How to identify the suspect

substations?substations?Use of Normalized residuals:Use of Normalized residuals:

Suspect substation measurements may not Suspect substation measurements may not have the largest normalized residuals.have the largest normalized residuals.Including too many substations in the suspect Including too many substations in the suspect list may degrade the second stage state list may degrade the second stage state estimator performance due to increased estimator performance due to increased complexity of the system model.complexity of the system model.

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Alternative Method:Alternative Method:Use of Reduced ModelUse of Reduced Model

exxhz CBI += ),(( ) 0, =CBI xxc

0=CBx

tI px ],[ 21θ=

tCB ppx ],,,,[ 2412142313 θθθ=

2323

Steps of Topology Error Steps of Topology Error Identification ProcedureIdentification Procedure

Step 1. Topology ProcessingStep 1. Topology ProcessingFirst a proper tree is selected for each substation. Based oFirst a proper tree is selected for each substation. Based on the tree, n the tree, the state variables are categorized into two groups:the state variables are categorized into two groups:

XXII and Xand XCBCB

Step 2. State EstimationStep 2. State EstimationEssentially identical to traditional state estimation carrieEssentially identical to traditional state estimation carried out by d out by existing methods. existing methods. Obtain both:Obtain both:

-- the measurement residual vector r the measurement residual vector r -- and the Lagrange multiplier vector of zero injectionsand the Lagrange multiplier vector of zero injections

Ix

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Steps of Topology Error Steps of Topology Error Identification ProcedureIdentification Procedure

Step 3. Compute the normalized residuals for Step 3. Compute the normalized residuals for the measurements and the normalized Lagrange the measurements and the normalized Lagrange multipliers for the circuit breaker variables.multipliers for the circuit breaker variables.

Step 4. Bad Data and Topology Error Step 4. Bad Data and Topology Error IdentificationIdentification

Check the largest normalized residual or Check the largest normalized residual or Lagrange multiplier.Lagrange multiplier.If it is larger than the threshold, suspect the If it is larger than the threshold, suspect the corresponding measurement or the breaker to corresponding measurement or the breaker to be the source of error in estimation.be the source of error in estimation.

2525

Reduced Model FormulationReduced Model Formulation

( ) CBt

CBItt xxxcWrrL λμ −−= ,

21

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡=

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

00000

I

ItI

tI

I

I

cz

x

r

CWHCHI

μ

CBx

λ ⎥⎦

⎤⎢⎣

⎡=

μλ

rT

t

CB

CB

CWH

T ⎥⎦

⎤⎢⎣

⎡−=

ModelModel State State VariablesVariables

FullFull

ImplicitImplicit

1224

231413

4321

,,,,,,,,

pppppθθθθ

21, pθ

Form the Lagrangian:

State Variables UsedOptimality conditions:

Note that is zero !

Then, can be solved as:

where:

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Simulated Topology and Simulated Topology and Measurement Errors Measurement Errors

3234−CB 3234−p

6874−CB6874−p

7880−CB 7880−pLine 4-657-bus

Line 10-2230-bus

Line 5-614-bus

Test BTest AWrong status CB & Outaged Line/ Meas.

Test System

2727

Example: IEEE 30 Bus SystemExample: IEEE 30 Bus System

2828

Results of Error IdentificationResults of Error Identification3030--Bus SystemBus System

6874−CB 6874−p

6870−CB 6874−CB

7110−CB 7473−CB

104105−CB 3436−CB

104106−CB 3133−CB 22.59157.04

28.00157.04

38.12160.95

38.37199.09

97.18212.30

Normalized residual / λN

Measurement/Topology



Test BTest A

2929

Results of Error IdentificationResults of Error Identification5757--Bus SystemBus System

7880−CB 7880−p

7882−CB 1241228−p

8281−CB 7880−CB

7576−CB 7882−CB

7577−CB8079−CB 36.93212.03

37.87212.03

37.87282.65

39.08371.63

96.40371.63





Test BTest A

3030

Critical Breaker PairsCritical Breaker Pairs

Either one of breakers2-3 and 2-4 can disconnectthe line incident to bus 4.

Hence, status errors in theseBreakers can be DETECTEDbut can NOT be IDENTIFIED.

3131

CONCLUSIONSCONCLUSIONSMeasurements can be processed at the Measurements can be processed at the substation in order to assist breaker error substation in order to assist breaker error detection and identification.detection and identification.State estimation results can be improved by State estimation results can be improved by proper identification of topology errors.proper identification of topology errors.TwoTwo--stage approach works well as long as the stage approach works well as long as the suspect substation is properly identified.suspect substation is properly identified.Reduced order SE allows topology error Reduced order SE allows topology error identification without the need to identify identification without the need to identify suspect substations. Implementation may be suspect substations. Implementation may be more involved.more involved.

detecting circuit breaker status errors in substations · pdf file1 detecting circuit breaker...

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