GAPGAPGAPGAPGAPGAPGAPGAP44444444generator assessment processgenerator assessment processgenerator assessment processgenerator assessment process

a solution to life assessment of large generators

omsaiempl@gmail.comanilscoob@gmail.com

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GAPGAPGAPGAP4444 GAPGAPGAPGAP3333

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GAPGAPGAPGAP4444 is the inspective approach to

assess the residual life of thegenerator

.

MethodologyMethodologyMethodologyMethodology

The methodology employed isconducting standard and specialelectrical tests and inspection on statorand rotor windings and accessories

UnitUnitUnitUnit ConditionConditionConditionCondition

The machine is in dismantledcondition with rotor threaded-out

InspectionInspectionInspectionInspection &&&& teststeststeststests PerformedPerformedPerformedPerformed

Physical examination

Tests and inspection

BenefitsBenefitsBenefitsBenefits

Reveals pending faults in winding

Reveals deterioration of coil insulation bycorona or end winding vibration

Establish a base line for evaluating futureinspection

Accurately assess life and futuremaintenance requirements

Record of core tightness

Preventive maintenance plan

Schedule for GAPGAPGAPGAP2222, GAPGAPGAPGAP3333 and GAPGAPGAPGAP4444

FinalFinalFinalFinal ReportReportReportReport

Standard format provided electronically

Photographs of critical areas

Dielectric absorption graph and analysis ofinsulation integrity

Results and summary of all test andmeasurements takenmeasurements taken

Location and levels of corona activity

Plots showing frequency distribution of endwinding basket

Core tightness record

EL CID test record and wedge mapping

Establishes a base-line for evaluating futureinspections and input for instituting plannedmajor maintenance activities

ExpectedExpectedExpectedExpected DowntimeDowntimeDowntimeDowntime

12-15 days

OptionOptionOptionOption

..

Life AssessmentFEM Approach

Overhangs

Turbine End

Geometrical data of the stator coils is collected to make a model by FEM method for stress analysis

Straight side

Exciter End

Overhangs

68

70

72

74

76

78

Stress/Tensile Strength (MPa)

LIFE ESTIMATION BY FEM METHOD

60

62

64

66

68

1090

1120

1150

1180

1210

1240

1270

1300

1330

1360

1390

1420

1450

1480

1510

1540

1570

1600

1630

1660

1690

1720

1750

1780

1810

1840

1870

1900

Stress/Tensile Strength (MPa)

Equivalent Operating Hours

Hundreds

Condition AssessmentRisk Assessment Approach

The following indicators are used separately toevaluate the condition of stator and rotor

• Operation and maintenance history• Physical inspection• Physical inspection• Insulation test• Generator Age

These condition indicators are initially evaluated usinginspections, tests, and measurements, which areconducted by utility staff or contractors over thecourse of time and as a part of routine maintenanceactivities.

Numerical scores are assigned to each stator androtor condition indicator, which are then weighted androtor condition indicator, which are then weighted andsummed to determine the Stator and Rotor ConditionIndices.

The lower of the two indices is selected to representthe overall Generator Condition Index.

An additional stand-alone indicator is used to reflectthe quality of the information available for scoring thegenerator condition indicators.

In some cases, data may be missing, out-of-date, orof questionable integrity.

Any of these situations could affect the accuracy ofAny of these situations could affect the accuracy ofthe associated condition indicator scores as well asthe validity of the overall Condition Index.

Given the potential impact of poor or missing data,the Data Quality Indicator is used as a means ofevaluating and recording confidence in the finalGenerator Condition Index.

Additional information regarding generator condition may benecessary to improve the accuracy and reliability of theGenerator Condition index.

Therefore, in addition to the Tier 1 condition indicators, thisappendix describes a “toolbox” of Tier 2 inspections, tests, andmeasurements that may be applied to the Stator and RotorCondition Indices, depending on the specific issue or problembeing addressed. Tier 2 tests are considered non-routine.

However, if Tier 2 data is readily available, it may be used toHowever, if Tier 2 data is readily available, it may be used tosupplement the Tier 1 assessment. Alternatively, Tier 2 testsmay be deliberately performed to address Tier 1 findings.

Results of the Tier 2 analysis may either increase or decreasethe score of the Generator Condition Index.

The Data Quality Indicator score may also be revised during theTier 2 assessment to reflect the availability of additionalinformation or test data.

Condition AssessmentStator

Operation & Maintenance History

Physical Inspection

Insulation Test

Generator Age

DC Ramped Voltage Test

Partial Discharge Measurement

Dissipation Factor Measurement

Ozone Monitoring

Black Out TestBlack Out Test

High Potential Withstand Test

Stator Core Inspection

Wedge Tightness Evaluation

Core Loop Test

ELCID Test

Corona Probe Test

Coupling Resistance Test

Bump test

Capacitance MeasurementCapacitance Measurement

Core Bolt Insulation Resistance

Winding Conductor Resistance Measurement

Impedance Measurement

Winding Dissection

10987654321

Stator Condition Index

10987654321

10740

Stator Data Quality Index

10740

Condition AssessmentRotor

Operation & Maintenance History

Physical Inspection

Insulation Test

Generator Age

High Potential Withstand Test

Rotor Core Inspection

AC Pole Drop Test

AC Impedance Test

Winding Resistance Measurement

RSO Test

10987654321

Rotor Condition Index

10987654321

10740

Rotor Data Quality Index

10740

Condition AssessmentGenerators

10987654321

Generator Condition Index

10987654321

10740

Generator Data Quality Index

10740

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