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Power Technologies, Inc.

Testing Methods: An OverviewTesting Methods: An Overview

Machine Measurements

James W. Feltes Power TechnologiesJohnny R. Willis Schenectady, NY

Carlos Grande-Moran

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Machine MeasurementsMachine Measurements

u Introduction

uTest Preparation

uTest Procedures

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IntroductionIntroductionuPurpose: More accurate models

Generator

Excitation System

Turbine Governor

uModel Parameters May Be Inaccurate

Not typically verified by field tests

Parameters may change (aging, tuning)

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Introduction (cont.)Introduction (cont.)

uBenefit: Improved Stability Analysis

Possible increase in power transfercapability

Equally possible decrease in power transfercapability

Increased accuracy in calculation oftransient and dynamic stability limits

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Introduction (cont.)Introduction (cont.)

uAdvantages of PTI Test Procedure:

Plant and generator protection remainsintact

No interruption of CT signals

Unit instantly available if needed

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Test PreparationTest PreparationuGather Information

One-line diagram showing metering,protection, and supply to auxiliaries

Generator and turbine nameplate data

Manufacturers data

Reactances and time constants Saturation curves and Vee curves

Reactive capability curve

Exciter and governor models, equipment info

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Test PreparationTest PreparationuGather Information (cont.)

Plant data

Hydro unit - physical description(measurements) of flow path (penstock, surgetank, tailrace)

Steam unit - heat balance diagram

All units - Allowed operating ranges (localcriteria or practices)

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Test Preparation (cont.)Test Preparation (cont.)u Select Signals

Accessibility & Location

Preconditioned? Transducers? Timedelay?

Determine location of test equipment

Wire signals to common terminal block Signal electrical isolation

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Test Preparation (cont.)Test Preparation (cont.)uVisit control room

Note meter locations and signal ranges

Determine feasibility of getting steady statedata from SCADA printouts on demand

Determine method of communications

between operator and test engineers

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Test Preparation (cont.)Test Preparation (cont.)uDetermine Test Sequence

Open Circuit

Vee Curves

Partial Load Rejections

uDetailed Step-by-Step Test Plan

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Test Preparation (cont.)Test Preparation (cont.)uDiscuss Test Procedure

Plant Operators and Engineers

Plant Informs System Dispatchers

No operator adjustments during datarecording

Tests typically require 1-2 days, includinginstrumentation setup

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Test EquipmentTest Equipment -- Dynamic System MonitorDynamic System Monitoru Recording of AC and DC signals

u Phasor measurement and recording of AC signals

u

Captures low frequency dynamic phenomenau Can compute real & reactive power, phase angle,

frequency, etc. in real time

u Comprehensive data analysis and power system simulation

capability through DADiSP and PSS/Eu Provides digital data allowing later comparison with

derived simulation model performance

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DSM System 200DSM System 200uPortable Version

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Measurement EquipmentMeasurement Equipment

uClamp-on CT

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Measurement Equipment (cont.)Measurement Equipment (cont.)

u Split Core CT

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uPosition Transducer

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uPosition Transducer on a Hydro Unit

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uMagnetic Pick-up

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uOptical Pick-up

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Test ProceduresTest Procedures

u Steady State Tests

Open Circuit Tests Vee Curves (MW/MVAr variations)

uDynamic Tests

Partial Load Rejections

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Open Circuit Test ProcedureOpen Circuit Test Procedure

uGoal: Generator Saturation Curve

u

Procedure: Unit at rated speed Main breaker open (unit off-line but at

rated speed)

Measure Efd and Ifd over range of Vt

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Open Circuit Test Procedure (cont.)Open Circuit Test Procedure (cont.)

uTerminal voltage measurement range:

30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%,90%, 95%, 100%, 104%, 108% of rated.

uTake backup readings (DVM, SCADA)when possible

uMake sure generator is isolated fromauxiliary loads

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Open Circuit Test Coordination RequirementsOpen Circuit Test Coordination Requirements

uPlant Operators:

Need to be able to hold unit at rated speed,open circuit (no power)

Hydro units - vibration, controls

Steam units - turbine heating, controls

Gas turbines - generally no problems

Adjustment of terminal voltage

AVR control range

Switch to manual for lower voltages if needed

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Open Circuit Test Procedure (cont.)Open Circuit Test Procedure (cont.)

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Vee Curve Test ProcedureVee Curve Test Procedure

uGoal: Steady State Reactances

u

Procedure: Main breaker closed (unit on-line)

Take steady-state readings at various loadlevels (MW) and excitation levels (MVAr)

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Vee Curve Test Procedure (cont.)Vee Curve Test Procedure (cont.)uMeasured Values:

Terminal voltages (from PTs)

Armature currents (from CTs)

Generator field voltage (direct) and current (from shunt)

Exciter field voltage (direct)

Turbine speed (automatic from DSM)

Control signal from governor, valve/gate position, etc.

Power angle (requires special instrumentation) if possibleuCalculated Values:

Real and Reactive Power (once per electrical cycle)

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Vee Curve Test Procedure (cont.)Vee Curve Test Procedure (cont.)uMeasurement Points

Based on unit reactive capability curve

Five MW levels (0, 25, 50, 75, 100%) Five MVAr levels at each MW level

Max (+,-) VARs that you are comfortable with

50% of maximum (+,-)

Unity power factor

Additional MW levels at any MVAr level

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Vee Curve Test Procedure (cont.)Vee Curve Test Procedure (cont.)uExample of

Measurement

Points (100 MVA,

0.85 PF Unit)

A

50

50

MVARS

ABSORBED

MVARS

SUPPLIED

REACTIVEPOWERINMVAR

10 50 85 MW 100

C

B

DUNDEREXCITATION REGION

SAFE OPERATION

POWER IN MW

OVEREXCITATION REGION

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Vee Curve Test Procedure (cont.)Vee Curve Test Procedure (cont.)uMeasurement

Points in

Tabular Form

T ical V Curve Measurement Points

500 MW Unit

MW MVAR

0 -250 -125 0 125 250

40 080 0

125 -250 -125 0 125 250

170 0

210 0

250 -200, -100, 0, 100, 200

290 0

330 0

375 -150, -75, 0, 75, 150

420 0

460 0

500 -100, 0, 100

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Vee Curve Coordination RequirementsVee Curve Coordination Requirements

uPlant Operators:

Need to go from zero to full load

Hydro and GT - easy Steam - involved process

Reverse-power relaying at zero load

Avoid levels of operating problems

Hydro - cavitation

Steam - control or auxiliary problems

GT - usually no problem areas

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Vee Curve Coordination RequirementsVee Curve Coordination Requirements

u System Operators:

Small Plant - usually easy

Large Plant: Requires coordination of dispatch changes with

output of other units

Adjustment of reactive output may affect

system voltages and require reactive powerredispatch (reactors, capacitors, scheduledvoltages on other units)

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Partial Load Rejection Test ProcedurePartial Load Rejection Test Procedure

uGoals:

Generator transient and subtransientreactances and field time constants

Turbine-generator inertia

Excitation system model parameters

Governor model parameters

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uProcedure:

Five partial load rejections Purpose: provide disturbance to excite unit

and determine dynamic response

Tests are designed to isolate parameters in

order to simplify analysis

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Load Rejection Coordination RequirementsLoad Rejection Coordination Requirements

uPlant Operators:

Need to go to desired loading (real and reactivepower)

Isolate generator from auxiliary loads

Will open main breaker to initiate test

Coordinate opening with measurement team

No operator adjustments until recording of testcompleted

Re-synchronization following test and preparation fornext test

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Load Rejection Coordination RequirementsLoad Rejection Coordination Requirements

u System Operators:

Inform system operator that test is imminent

System will see loss in real and/or reactive power

Change in frequency very small for systems withlarge generating capacity

Change in line flows or bus voltages may be

significant

Preventative dispatch or other operating changes?

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uTest #1 (Direct Axis Parameters)

0 MW

-30% MVAr

Excitation system in manual control

uUnderexcite unit so open circuit voltage

is lower than operating voltageuGenerator saturation minimized

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uTest #1 - typical terminal voltage plot:

1 2

1 4

1 6

1 8

2 0

2 2

2 4

2 6

0 5 1 0 1 5 2 0 2 5 3 0

T im e ( S e c o n d s )

TerminalVoltage(kV)

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Partial Load Rejection Test ProcedurePartial Load Rejection Test ProcedureuTest #2 (Excitation System Parameters)

0 MW -30% MVAR

Limit var absorption so that field voltage doesnot go below 50% of value at rated voltage, noload.

Excitation system in AVR control

uAVR parameters including limits

uAlternative: Step in AVR reference

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uTest #2 - typical terminal voltage plot:

2 4 . 4

2 4 . 6

2 4 . 8

25

2 5 . 2

2 5 . 4

2 5 . 6

0 2 4 6 8 1 0

T i m e ( S e c o n d s )

TerminalVoltage(kV)

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uTest #3 (Excitation system response inopposite direction) 0 MW +25% MVAR

Var load should not allow terminal voltage toexceed 8% overvoltage (use data from sat.)

Excitation system in AVR control

uAVR parameters including limits

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uTest #4 (Quadrature axis and governormodel parameters) 5% to 10% MW (typical) -5%to -15% MVAr (typical)

Set VARs so power angle matches powerfactor, resulting in all flux on quadrature axis

Excitation system in manual control

u Small signal governor response

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Partial Load Rejection Test ProcedurePartial Load Rejection Test ProcedureuTest #5 (Quadrature axis and governor

model parameters)

20% MW May use < 20% MW to limit overspeed

Use results of test #4 to estimate overspeed.

-5% to -15% MVAR (typical)

Set Vars so power angle matches power factor Excitation system in AVR control

uGovernor limit determination

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Partial Load Rejection Test ProcedurePartial Load Rejection Test ProcedureuTest #5 - typical speed (frequency) plot

150 MW Hydro , 40 MW rejection

5 9 . 8

6 0

6 0 . 2

6 0 . 4

6 0 . 6

6 0 . 8

6 1

6 1 . 2

6 1 . 4

6 1 . 6

6 1 . 8

0 1 0 2 0 3 0 4 0 5 0

T i m e ( S e c o n d s )

Speed(Hz)

3% Overspeed

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Additional Examples of MeasurementsAdditional Examples of Measurements

uExcitationsystem step

test on anuclear unit

uPlot ofterminal

voltageversus time

Te

rminalVoltage

(kV)

TerminalVoltage

(kV)

Time (cycles)Time (cycles)

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u Sameexcitationsystem step

test on anuclear unit

u Plot of fieldvoltage versus

time

Fiel

d

Fiel

d


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u Governorload rejectiontest.

u 650 MWsteam unit (70MW rejection)

u Plot ofgeneratorfrequencyversus time

Fre que n

c y

(Hz)

Fr e que nc y

(Hz

)


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u Samegovernor loadrejection test.

(650 MWsteam unit)

u Plot of controlvalve position

versus timeCon

t rol

Va l v

e

Pos it i o

n

(%)

Con

t rol

Va l v

e

Pos i t

ion

( %) Time (cycles)Time (cycles)

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u Governor loadrejection test.

u 44 MVA hydrounit (4.8 MWrejection)

u Plot of generatorspeed deviationversus time

(measured andfrom simulationmodel)

Sp

ee

d

Spe

ed

Time (Seconds)Time (Seconds)

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u Same governorload rejectiontest. (44 MVA

hydro unit)u Plot of gate

position versus

time (measuredand from

simulationmodel)

Ga t e

s it ion

Ga t e

s i t

ion


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u 45 MVA gasturbine unit (5.4MW rejection)

u Plot of generatorspeed deviationversus time


Speed

Deviation

(pu)

Speed

Deviation

(pu)


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u Same governorload rejectiontest. (45 MVAgas turbine)

u Plot of FSR (fuelcommandvoltage) versus

time (measured

and fromsimulationmodel)

FS

R

u)

FSR

u)


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u Same governorload rejectiontest. (45 MVAgas turbine)

u Plot of exhausttemperature (oC)

versus time(measured and

from simulationmodel) E

x h

a us t

Te m

pe ra t ure

(

Ex h

a us t

Te mpe ra t ure

(

oC

))


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u Same 45 MVAgas turbine unit

u 12.9 MW loadrejection

u Plot of generatorspeed deviation

versus time(measured andfrom simulationmodel)

Speed

Speed


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u Same governorload rejection test.(45 MVA gasturbine - 12.9 MW

rejection)u Plot of FSR (fuel

commandvoltage) versustime (measured

and fromsimulation model)

FS

R

u)

FSR

u)


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u Same governorload rejectiontest. (45 MVAgas turbine - 12.9MW rejection)


versus time


Ex h

a us t

Te m

pe ra t ure

(

Ex h

a us t

Te mpe ra t ure

(

oC

))


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u Governor loadramp test.

u Same 45 MVAgas turbine unit

u Plot of generatorelectric powerversus time(measured and

from simulationmodel)

Electric

Electric


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u Same governorload ramp test.

u 45 MVA gasturbine unit

u Plot of FSR (fuelcommandvoltage) versustime (measuredand fromsimulation model)

FS

R

u)

FSR

u)


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u Same governorload ramp test.

u 45 MVA gasturbine unit


versus time(measured and

from simulationmodel) E

x h

a us t

Te m

pe ra t ure

(

Ex h

a us t

Te mpe ra t ure

(

oC

))


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Next Step Model DerivationNext Step Model Derivation

uData processing

uModel derivation

- understanding of models and equipment- certain amount of trial and error

- experience helps

uComparison with test results

uTypically requires 1 -2 weeks per unit

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Technology Transfer to UtilitiesTechnology Transfer to Utilities

uTraining of utility staff in testing andmodel derivation

PTIs experience is that testing is moreeasily learned than model derivation

Utility staff generally experienced in plantoperations and instrumentation

May be less experienced in controls andequipment modeling

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