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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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