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GAPGAPGAPGAPGAPGAPGAPGAP44444444

a solution to life assessment of large generators

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GAPGAPGAPGAP

1111

GAPGAPGAPGAP

2222

****

GAPGAPGAPGAP4444

GAPGAPGAPGAP3333

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GAPGAPGAPGAP4444 is the inspective approach to

assess the residual life of thegenerator

.

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MethodologyMethodologyMethodologyMethodology

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

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UnitUnitUnitUnit ConditionConditionConditionCondition

The machine is in dismantled

condition with rotor threaded-out

InspectionInspectionInspectionInspection &&&& teststeststeststests PerformedPerformedPerformedPerformed

Physical examinationTests and inspection

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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 planSchedule for GAPGAPGAPGAP2222, GAPGAPGAPGAP3333 and GAPGAPGAPGAP4444

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FinalFinalFinalFinal ReportReportReportReport

Standard format provided electronically

Photographs of critical areas

Dielectric absorption graph and analysis ofinsulation integrity

Results and summary of all test andmeasurements taken

Location and levels of corona activityPlots 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

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ExpectedExpectedExpectedExpected DowntimeDowntimeDowntimeDowntime

12-15 days

OptionOptionOptionOption

.

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Life AssessmentFEM Approach

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Overhangs

Turbine End

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

Straight side

Exciter End

Overhangs

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70

72

74

76

78

ileStrength(M

Pa)

LIFE ESTIMATION BY FEM METHOD

60

62

64

66

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/Te

n

Equivalent Operating Hours

Hundreds

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Condition AssessmentRisk Assessment Approach

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The following indicators are used separately to

evaluate the condition of stator and rotor

Operation and maintenance history Ph sical ins ection

Insulation test Generator Age

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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 and

rotor 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.

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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 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.

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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, and

measurements 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 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 decrease

the score of the Generator Condition Index.

The Data Quality Indicator score may also be revised during theTier 2 assessment to reflect the availability of additional

information or test data.

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Condition AssessmentStator

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Operation & Maintenance History

Physical Inspection

Insulation Test

Generator Age

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DC Ramped Voltage Test

Partial Discharge Measurement

Dissipation Factor Measurement

Ozone Monitoring

High Potential Withstand Test

Stator Core Inspection

Wedge Tightness Evaluation

Core Loop Test

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ELCID Test

Corona Probe Test

Coupling Resistance Test

Bump test

Core Bolt Insulation Resistance

Winding Conductor Resistance Measurement

Impedance Measurement

Winding Dissection

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Stator Condition Index

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Stator Data Quality Index

10740

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Condition AssessmentRotor

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Operation & Maintenance History

Physical Inspection

Insulation Test

Generator Age

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High Potential Withstand Test

Rotor Core Inspection

AC Pole Drop Test

AC Impedance Test

Winding Resistance Measurement

RSO Test

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Rotor Condition Index

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Rotor Data Quality Index

10740

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Condition AssessmentGenerators

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Generator Condition Index

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Generator Data Quality Index

10740

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