generator assessment process - an overview

GAPGAPGAPGAPGAPGAPGAPGAP********generator assessment processgenerator assessment processgenerator assessment processgenerator assessment process

a solution to life assessment of large generators

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First Turbo Generator (1884)

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The deterioration of large generators or forthat matter any electrical equipment isnormal, and this process begins as soon asgenerator is installed.

If deterioration is not checked, it can causeIf deterioration is not checked, it can causeelectrical failures and malfunctions.

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In addition a TEAM of stresses

- Thermal

- Electrical

- Ambient

- Mechanical- Mechanical

further contributes to thedeterioration process.

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TTTThermalhermalhermalhermal EEEElectricallectricallectricallectrical

StressStressStressStress

MMMMechanicalechanicalechanicalechanical AAAAmbientmbientmbientmbient

StressStressStressStress

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TheTheTheThe purposepurposepurposepurpose ofofofof aaaa goodgoodgoodgood maintenancemaintenancemaintenancemaintenanceprogramprogramprogramprogram shallshallshallshall bebebebe• totototo discoverdiscoverdiscoverdiscover thethethethe potentialpotentialpotentialpotential reasonsreasonsreasonsreasons ofofofofdeteriorationdeteriorationdeteriorationdeterioration• taketaketaketake remedialremedialremedialremedial measuresmeasuresmeasuresmeasures forforforfor correctioncorrectioncorrectioncorrectiontotototo avoidavoidavoidavoid catastrophiccatastrophiccatastrophiccatastrophic failuresfailuresfailuresfailures....

TheTheTheThe otherotherotherother importantimportantimportantimportant purposepurposepurposepurpose ofofofofmaintenancemaintenancemaintenancemaintenance programprogramprogramprogram isisisis totototo maximizemaximizemaximizemaximizereliabilityreliabilityreliabilityreliability andandandand availability,availability,availability,availability, improveimproveimproveimproveoperationaloperationaloperationaloperational efficiencyefficiencyefficiencyefficiency andandandand productivityproductivityproductivityproductivity....

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GAPGAPGAPGAP**** is the answeris the answeris the answeris the answerGAPGAPGAPGAP**** is the answeris the answeris the answeris the answer

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GAPGAPGAPGAP**** is a proactive action and the solution to

ensure availability and reliability of generators as well as improve operational efficiency and

productivity to ensure smooth and trouble free running of the plant.

GAPGAPGAPGAP**** is an inspection and maintenance process GAPGAPGAPGAP is an inspection and maintenance process

during the lifetime of a generator and is planned for during either operation or outage.

GAPGAPGAPGAP**** can be linked to the generator planned outage time thereby ensuring minimum downtime of the plant and at the same time assessing the

healthiness of the generator.anilscoob@gmail.com

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GAPGAPGAPGAP1111 GAPGAPGAPGAP2222

GAPGAPGAPGAP****

GAPGAPGAPGAP4444 GAPGAPGAPGAP3333

GAPGAPGAPGAP****

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GAPGAPGAPGAP1111

• During operation of the

generator

• Data collection and on-

line measurement when

the generator is in

operation

• Recommended after GAPGAPGAPGAP1111 • Recommended after

8,000 hours of

operation

• Usually takes 1 day

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GAPGAPGAPGAP1111 deliverables

Thermal Life Assessment by Arrhenius EquationThermal Life Assessment by Arrhenius Equation

Thermal Life Assessment by N-Y method

Schedule for GAPGAPGAPGAP2222,,,, GAPGAPGAPGAP3333 and GAPGAPGAPGAP4444

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GAPGAPGAPGAP2222

• During outage with

power cables removed

from the generator

• Data collection and off-

line electrical

measurements

• Recommended after GAPGAPGAPGAP2222 • Recommended after

16,000 hours of

operation

• Usually takes 2 days

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GAPGAPGAPGAP2 2 2 2 deliverables

Condition Assessment based on Diagnostic TestsCondition Assessment based on Diagnostic Tests

Residual Life Assessment by D-map Method

May include GAPGAPGAPGAP1111 deliverables

Schedule for GAPGAPGAPGAP3333,,,, GAPGAPGAPGAP4444 and GAPGAPGAPGAP1111

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GAPGAPGAPGAP3333

• During outage on

partially disassembled

generator (end-covers

and inspection windows

removed)

• Inspection and tests to

the extent possibleGAPGAPGAPGAP• Recommended after

32,000 hours of

operation

• Usually takes 3-5 days

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GAPGAPGAPGAP3 3 3 3 deliverables

Visual Examination and inspectionVisual Examination and inspection

Residual Life based on Stress Analysis

May include GAPGAPGAPGAP1111 & GAPGAPGAPGAP2222 deliverables

Schedule for GAPGAPGAPGAP4444, , , , GAPGAPGAPGAP1111 and GAPGAPGAPGAP2222

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GAPGAPGAPGAP4444

• During outage on fully

disassembled generator

with rotor threaded-out

• Inspection and

appropriate testing

• Recommended after

64,000 hours of GAPGAPGAPGAP4444 64,000 hours of

operation

• Usually takes 10-12

days

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GAPGAPGAPGAP4 4 4 4 deliverables

Residual Life based on Stress Analysis

Condition Assessment and IndexCondition Assessment and Index

Risk Assessment and Index

may include GAPGAPGAPGAP1111, GAPGAPGAPGAP2222 & GAPGAPGAPGAP3333 deliverables

Schedule for GAPGAPGAPGAP1111, , , , GAPGAPGAPGAP2222 and GAPGAPGAPGAP3333

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GAP ConceptLife Cycle Concept

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Continuous

Upgrading/

Replacement

Overhaul

Maintenance

Aging

Optimized Maintenance Line

Value to Customerthrough Maintenance

}

Life Cycle ConceptLife Cycle Concept

Upgrade and Modernization Period Warranty Period

AgingRepair

Time

Maintenance Period

Replacement & Recycle Period

Customer Project Lifecycle

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GAP ConceptConfidence Level

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Stress calculated

Stress calculated

from GAP2

Strength Calculated

from GAP2

Strength Calculated

from GAP3

Stress calculated

from GAP1

Strength Calculated

from GAP1

Stress calculated

from GAP4

calculated

from GAP3

Strength Calculated

from GAP4

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Str

ength

/str

ess

Strength

uncertainty

Str

ength

/str

ess

Time

Stress

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GAP ConceptStator Winding Failures

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Failure statisticsFailure statistics

37%3%5%

11%Bearing

Winding

Detection during Normal Operation

37%

33%

5%

6%3% Winding

Rotor

Shaft/coupling

Brushes/slipring

External devices

Not specif ied

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Failure statisticsFailure statistics

7%

4%10%

Bearing

Winding

Detection during maintenance or test

8%

2%

8%

61%

Rotor

Shaft/coupling

Brushes/slipring

External devices

Not specified

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Failure Statistics ConclusionFailure Statistics Conclusion

• Bearings fail frequently

• Windings also share a significant failure rate

• Very few winding failures are detected• Very few winding failures are detectedin maintenance (8.3%) as against thetotal failure of 33% in normal operation

• This indicates poor insulation problemsdetection technique

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