generator assessment process - level 2
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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
10987654321
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