GAPGAPGAPGAPGAPGAPGAPGAP22222222generator assessment processgenerator assessment processgenerator assessment processgenerator assessment process

a solution to life assessment of large generators

omsaiempl@gmail.comanilscoob@gmail.com

GAPGAPGAPGAP1111 GAPGAPGAPGAP2222

GAPGAPGAPGAP****

GAPGAPGAPGAP4444 GAPGAPGAPGAP3333

GAPGAPGAPGAP****

GAPGAPGAPGAP2222 is the diagnostic approach to

assess the residual life of the generator

MethodologyMethodologyMethodologyMethodology

The methodology employed isconducting standard and specialelectrical tests on stator and rotorwindings and accessories

UnitUnitUnitUnit ConditionConditionConditionCondition

The generator is in assembled conditionwith power cables disconnected

InspectionInspectionInspectionInspection &&&& teststeststeststests PerformedPerformedPerformedPerformed

Diagnostic test

Insulation test

Polarization index

Capacitance and tan delta test

AC current test

Partial discharge test

BenefitsBenefitsBenefitsBenefits

Reveals pending faults in winding

Reveals deterioration of coil insulation by corona or endwinding vibration

Access life and future maintenance requirements

Preventive maintenance plan

Schedule for GAP1111, GAP3333 and GAP4444Schedule for GAP1111, GAP3333 and GAP4444

FinalFinalFinalFinal ReportReportReportReport

Standardized format in electronic form

Photographs of critical areas

Residual breakdown strength

Remaining life

Analysis and recommendation

ExpectedExpectedExpectedExpected DowntimeDowntimeDowntimeDowntime

1-2 days

OptionOptionOptionOption

Life AssessmentDiagnostic Tests

Consumed LifeInsulation Deterioration

Thermal StressElectrical Stress

Thermal Cycle Stress

Operational History

Establishment of Residual

BDV

Life Estimation with Operational

History

Life Estimation with Diagnostic

Tests

Residual LifeInsulation deterioration

Residual Years to 2E+1 KV

Deduced Assessment

Preventive Maintenance Program

BDV

Future Operation

Pattern

Visual Inspection

Overhaul or Rewind

Diagnostic Tests

Life AssessmentD-map Method

Based on the results of Diagnostic Test, the residuallife of stator winding insulation system is derived.

The international standard IEC 60216-2 defines theend point to be 50% voltage value of the initialbreakdown voltage. The reason why “50%” is definedas the end point Is that the insulation deteriorationaccelerates at the final stage of life as shown in theclassic Bathtub Curve.classic Bathtub Curve.

Based on experiments and experiences, the endpoint is defined to be 40% of the breakdown voltage.However, it is recommended to plan for statorwinding when the estimated breakdown voltage is40∼50 % of initial breakdown voltage.

Diagnostic Tests

Vr ∝ f (∆tanδ, ∆I, Qmax)

Vr = Residual breakdown strength (%)

∆∆∆∆tanδδδδ = Deviation of tanδδδδ from lower to higher voltage

∆∆∆∆I = Rate of increase of ac current

Qmax = Maximum partial discharge

50

60

70

80

90

100

Resid

ual B

reakd

ow

n s

tren

gth

(%

)Life Estimation by D-Map Method

Residual Breakdown Strength

IEC Breakdown Strength

Breakdown Strength

Present Life

Life Estimation

0

10

20

30

40

50

0 5 10 15 20 25 30 35 40 45

Resid

ual B

reakd

ow

n s

tren

gth

(%

)

Operating Years

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Life Index

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Life AssessmentB-map Method

Life Assessment by B-method is derived from the breakdownvoltage of the insulation system.

The insulation voltage level that is required for safe operationof the generator in the case that a surge arrester is equippedfor suppressing lightening surges is [2E+1] KV

The insulation voltage level that is required when the groundfault is happened around the generator terminals is [1.5E] KVfault is happened around the generator terminals is [1.5E] KV

30

40

50

60

70B

reakd

ow

n V

olt

ag

e (

KV

)

Life Estimation by B-Method

Voltage Level (2E+1 KV)

required for safety

operation in considering

the incoming lightening

surges

Voltage Level (1.5E KV)

required for safety

operation in considering the ground fault on line

0

10

20

30

0 5 10 15 20 25 30 35 40

Breakd

ow

n V

olt

ag

e (

KV

)

Operational years

Residual Breakdown Voltage 2E+1 KV

Residual Breakdowb Voltage 1.5E KV

present breakdown voltage

Breakdown Voltage Level 2E+1 KV

Breakdown Voltage Level 1.5E KV

10

12

14

16

18

20

Dis

ch

arg

e P

aram

ete

rs

Breakdown Voltage by D-Map Method

90%

80%

70%

60%

50%

40%

30%

Series8

0

2

4

6

8

10

1000 10000 100000 1000000

Dis

ch

arg

e P

aram

ete

rs

Maximum Discharge Magnitude

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Life Index

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Condition AssessmentDiagnostic Tests

Diagnostic Tests

Diagnostic Tests Assessment

IR > 2E+1 MΩ

PI > 1.5

∆∆∆∆tanδδδδ < 5.0%, 8.5%, 12.5%∆∆∆∆tanδδδδ < 5.0%, 8.5%, 12.5%

∆∆∆∆I < 5.0%, 8.5%, 12.5%

Qmax < 10,000 pC

Diagnostic Tests Assessment

IR ≥≥≥≥ 100 MΩ

PI ≥≥≥≥ 1.5

∆∆∆∆tanδδδδ ≤≤≤≤ 2.0%∆∆∆∆tanδδδδ ≤≤≤≤ 2.0%

∆∆∆∆I ≤≤≤≤ 2.0%

Qmax < 10,000 pC

Diagnostic Tests Assessment

IR ≥≥≥≥ 100 MΩ

PI ≥≥≥≥ 1.5

∆∆∆∆tanδδδδ ≤≤≤≤ 0.7%, 6.5%∆∆∆∆tanδδδδ ≤≤≤≤ 0.7%, 6.5%

∆∆∆∆I ≤≤≤≤ 4.0%, 8.5%, 12.5%

Qmax < 10,000 pC

Diagnostic Tests Assessment

IR ≥≥≥≥ 100 MΩ @ 40oC

PI ≥≥≥≥ 2.00

∆∆∆∆tanδδδδ ≤≤≤≤ 1.0∆∆∆∆tanδδδδ ≤≤≤≤ 1.0

∆∆∆∆I ≤≤≤≤ 1.0%

Qmax < 10,000 pC

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Health Index

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