GAPGAPGAPGAPGAPGAPGAPGAP11111111generator 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****

anilscoob@gmail.com

GAPGAPGAPGAP1111 evaluates the thermal residual

life from experience and theaccumulated data

Optionally diagnosis of faults throughon-line testing - vibration signatureanalysis, current signature analysis andinfrared thermal imaging

MethodologyMethodologyMethodologyMethodology

The methodology employed is estimation ofconsumed life and residual life

Consumed life is estimated by operationalhistory

Residual life is estimated by consumed life,establishment of calculation method forresidual break-down voltage and operationpattern in the future

UnitUnitUnitUnit ConditionConditionConditionCondition

The generator is in operation

InspectionInspectionInspectionInspection &&&& teststeststeststests PerformedPerformedPerformedPerformed

OEM data and specificationOEM data and specification

Operational history

Operational parameters

Thermal profile

Maintenance history

BenefitsBenefitsBenefitsBenefits

Extent of thermal life degradation

Preventive maintenance plan

Schedule for GAP2222, GAP3333 and GAP4444

FinalFinalFinalFinal ReportReportReportReportFinalFinalFinalFinal ReportReportReportReport

Standardized format in electronic form

Photographs of critical areas

Thermal residual life

Analysis and recommendation

ExpectedExpectedExpectedExpected DowntimeDowntimeDowntimeDowntime

Zero days

OptionOptionOptionOption

Vibration severity levelVibration severity level

Vibration signature analysis

Electrical Signature analysis

Infrared thermal imaging

Life AssessmentThermal Life Assessment

Ageing of an Electrical Insulation System

Assessment of Condition and Residual Life Time

Inverse Power Law and Arrhenius Law

Single Stress and Multi Stress Ageing of EIS

Thermal Life AssessmentArrhenius Equation

TTTThermalhermalhermalhermal ElectricalElectricalElectricalElectrical

StressStressStressStress

MechanicalMechanicalMechanicalMechanical AmbientAmbientAmbientAmbient

StressStressStressStress

anilscoob@gmail.com

Thermal Ageing Model

The thermal ageing in insulating materials is complexand the mechanisms vary in different materials andunder different service conditions.To a first approximation, the oxidation process can beexpressed by the Arrhenius rate law.

It is evident that, the higher the temperature, theshorter is the life expectancy of the insulation. TheArrhenius law is the basis of all accelerated ageingtests which are used to estimate the thermal life of awinding and is also used to define the insulationthermal classes

Arrhenius Equation

Dr. Svante August Arrhenius was a Swedish scientist, professor of physics, and the founder of physical chemistry. In 1903, he received the Nobel Prize for

Chemistry for his study of ionic theory

Lr ∝ f (Y, Yo, N, Tmax, Tavg, Tamb)

Lr = Residual thermal life (years)

Y = Operating years

Yo = Equivalent operating years

N = Number of starts/stops

Tmax = Maximum allowable temperature (oC)

Tavg = Average operating temperature (oC)

Tamb = Ambient temperature (oC)

THE R MAL L IF E

C urves plotted at different winding temperature in oC

50

60

70

80

90

100

% L

ife

81859095100

0

10

20

30

40

0 5 10 15 20 25 30 35

x 10000

Hours of Operation

81 85 90 95 100 pres ent

R emaining T hermal L ife vs Winding T emperature

81

8515

20

25

x 1

00

00

Re

am

ain

ing

Lif

e

(No

. o

f h

ou

rs)

90

100

95

0

5

10

80 82 84 86 88 90 92 94 96 98 100

T emperature (deg C )

Re

am

ain

ing

Lif

e

(No

. o

f h

ou

rs)

50

60

70

80

90

100

Residual Thermal Life(%)

Thermal Life Estimation by Arrhenius EquationBHEL 46.25 MVA, 11 KV, 3000 rpm Turbo-generator @ Monnet Ispat, Raipur

presentlife

0

10

20

30

40

0 5

10

15

20

25

30

Residual Thermal Life(%)

Operating Years

residual thermal life present life thermal life

thermal life

40

50

60

70

80

90

100

Residual Thermal Life(%)

GAP Estimation by Arrhenius EquationBHEL 46.25 MVA, 11 KV, 3000 rpm Turbo-generator @ Monnet Ispat, Raipur

0

10

20

30

40

0 5

10

15

20

25

30

Residual Thermal Life(%)

Operating Years

GAP11 GAP21 GAP31 GAP41 GAP12 GAP22 GAP32 GAP42

10987654321

Life Index

10987654321

Thermal Life AssessmentN-Y Map Method

TTTThermalhermalhermalhermal ElectricalElectricalElectricalElectrical

StressStressStressStress

MechanicalMechanicalMechanicalMechanical AmbientAmbientAmbientAmbient

StressStressStressStress

anilscoob@gmail.com

Electrical aging and thermal aging both depend onservice operation in year (Y), and aging due toheating and cooling is proportional to the number ofstarts-stop of a machine (N)

From empirical data based on the insulation systemstudy i.e. the electrical, thermal aging characteristicsand the heating and cooling cycle characteristics, aNY-map is derivedNY-map is derived

From the equation by experimental data, the residualbreakdown strength (%) is as

Vr ∝ f (Y, N, No, Tmax, Tavg, Tamb)

Vr ∝ f (Y, N, No, Tmax, Tavg, Tamb)

Vr= Residual breakdown strength (%)

Y = Operating years

N = Number of starts/stops

No = Equivalent number of starts/stops

Tmax = Maximum allowable temperature (oC)

Tavg = Average operating temperature (oC)

Tamb = Ambient temperature (oC)

65

70

75

80

85

90

Residual Breakdown Strength (%)

Thermal Life Estimation by N-Y MethodBHEL 46.25 MVA, 11 KV, 3000 rpm Turbo-generator @ Monnet Ispat, Raipur

presentlife

thermal life

40

45

50

55

60

0 5 10 15 20 25 30 35 40

Residual Breakdown Strength (%)

Operating Years

Residual Breakdown Strength Minimum Breakdown Strength present life thermal life

thermal life

10987654321

Life Index

10987654321

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