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JICA Study Team for Enhancing Eff ici ency of Operating Thermal Power Plants in NTPC-India
Issued in Feb 2010
Summary of
Generator Assessment&
GT Assessment
2010
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1. Generator Assessment procedures
2. Generator assessment results of Korba#6,Rihand#2, Singlauli#4
3. GT Assessment procedures
4. GT assessment results of Korba#6, Rihand#2,Singlauli#6
Contents
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Generator Assessment procedures
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3Generator Assessment procedures
Required specification of stator
Insulator : MicaResin: EpoxyResin process: VPI (Vacuum Pressure Impregnation)
Target for the assessment
235.3MVA, 15.75kV, Stator: water cooledSingrauli #4
605MVA, 20kV, Stator: water cooledRihand #2
588MVA, 16.2kV, Stator: water cooledKorba #6Main specification
Target specification is the same as required specification of stator.
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4Assessment procedures
Assessment type
Current condition assessmentJudging from the latest test resultsRemaining l ife assessment (RLA)
Judging from lots of historical test data
Generator part for the assessment
Assessment Is conducted according to Japanese criteria.
Stator coil insulationStator coil insulation is most deteriorated.
Sorts of stator coil insulation diagnosis for assessment1)Insulation resistance test (IR test)2) Polarization index test (PI test)3) Tan test
4) Step voltage test5) Parti al discharge test (Corona test)
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Generator assessment results of Korba#6, Rihand#2, Singlauli#4
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6Korba#6 assessment results
Not available PI test
RLA
= IR (8 min) / IR (1 min) Not available0.994PI test
Not available0.0628930 M IR test
Cur rent condition assessment
Remark EvaluationTest r ecordTest item
Korba#6 does not drain and dry stator coil.So, Korna#6 test data is meaningless for the assessment.
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No more than one test r esult Notavailable
Tan test
Fluctuates PI da ta Notavailable
3-phasePI testRemaining life assessment
Good1.24%BGood1.08%Y
JP: tan < 2.5%Good0.74%R Tan test
( Tan )
JP, NTPC 2.0Good3.753-phasePI test
JP 50 M , NTPC 21 M
Good1000 M 3-phaseIR testCur rent condition assessment
Remark/standardEvaluationTest r ecordPhaseTest item
Rihand#2 assessment results
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y = 0.0093e 0.0574x
0.5%
1.0%
1.5%
2.0%
2.5%
3.0%
0 2 4 6 8 10 12 14
Test voltage (kV)
T a n
( % )
Tan
test (Y phase)
Estimation of Tan 0 & Tan max (Y phase)
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9Rihand#2 RLA
y = -0.1933x + 6.6281
0
1
2
3
4
5
6
7
8
0 5 10 15 20O peration year (year)
P I d a t a
Dange rous crite ria: Le s s than 1.0
Cautio n crite ria: L es s than 2.0
I test historical trend (Whole phases test)
(Jul-1989)
Multiple historical Tan data is not available. ThereforeRLA is conducted by m ult iple historical PI test
Ave.=3.7
PI data has fluctuated recentlyNo deterioration trend
Impossible to conduct RLA
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10Singraulii#4 assessment results
The evaluation items differ from those in J apan.
Not available Partialdischar ge test
Not available0.02%B
Not available-0.03%Y
JP: tan < 2.5%The test voltage is low.
Not available0.01%R Tan test( Tan )
Good2.11B
Good2.86YJP, NTPC 2.0Good2.58R PI test
Good1900 M B
Good3500 M Y
JP 50 M , NTPC 17 M Good3100 M R IR test
Remark/standardEvaluationTestrecord
Phase
Current condition assessment
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Results of Tan
Impossible to conduct Current condition by Tan test
Singrauliu#4 current condit ion assessment
y = 0.8567e -3E-05x
y = 0.8791e 0.0028x
0.840.850.860.87
0.880.89
0.90.910.920.93
0 1 2 3 4 5 6Test voltage (kV)
T a n ( % )
: R phase: Y phase: B phase
Technically, the higher test vol tage is, the higher tan data become.But Y-phase data declines. So, these data are not reliable.
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12Singraulii#4 assessment results
RLA
The test voltage is low. Not available AllTan
The PI data does not show adeteriorating trend.
Not available BUp to the dangerous level *1201936 years
Up to the caut ion level *1201229 yearsY
Up to the dangerous level *1202239 years
Up to the caut ion level *1201532 yearsR PI t est
Year Operationyears
PhaseTest
*1: PI data is easily changeable due to stator dryness level
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13Singrauli #4 RLA
RLA by PI test (R phase)
y = -0.1371x + 6 .3445
0
1
2
3
4
5
6
7
0 10 20 30 40
O peration year (year)
P I
PI historical trend (R-phase)
Dangerous crite ria: Less than 1.0
Caution criteria: Less than 2.0
(1983)
Although PI data fluc tuate due to stator coil d ryness,the deterioration trend is shown.
Approximation formula byExcel function
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1. Conduct ing insulation diagnosis without cool ing water (Korba)
It is recommended that Korba#6 conduct the insulationdiagnosis without cool ing water so that Korba#6 can grasp thecurrent condi tion, the deterioration trend.
2. Conduct test by appropriate test vol tage (Singrauli)When Tan test is conducted, it is required to conduct i t byappropriate test voltage. Because it mainly focuses on partial
discharge in voids of the insulation. The partial discharge doesnot occur at low test voltage.
1. Continue to conduct the insulation diagnosis
NTPC should conduct the insulation diagnosis periodically inthe future so that NTPC can grasp the deterioration t rend.
2. Get reliable and accurate test dataSome test data is not consistent with technical theory. Check
the test data and get reliable and accurate test data .
Recommendations
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Rihand#2
*3
PD Remarks
( )*4Japan
*2Singrauli#4
*1 *1Korba#6
Tan S-VPIIRPlant
S-V: Step-voltage test PD:Partial discharge test*1: Test with cooling water is meaningless.*2: Max test voltage is low.*3: Measurement data is different f rom Japanese one
*4: Some OEMs do, the others do not in Japan.
Status of conducting insulation diagnosis test
Insulation diagnosis is totally evaluated by all the tests inJapan.
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GT Assessment procedures
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17Required specification & Target GT
Required specification of GT
Oil immersed transformer Insulation paper : craft paper Sealed typeNo absorbent in oil
Target for the assessment
Target specification is the same as required specif ication.
Single phase 200 MVA 1 unit, OFWF, Sealed typeSingrauli#6Single phase 201.7 MVA 3 units, OFWF, Sealed typeRihand#2Single phase 200 MVA 3 unit s, OFAF , Sealed typeKorba#6
Main specificationUnit
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18Assessment method
Assessment type
Current condition assessmentJudging from the latest test dataRemaining l ife assessment (RLA)
Judging from lots of historical test data
GT part for the RLA
Assessment Is conducted according to Japanese criteria.
Coil insulation paper Because Coil insulation paper is most deteriorated.
Sorts of GT assessment1)Insulation resistance test (IR test)2) Dissolved gas analysis (DGA)3) Furfural analysis
4) CO+CO2 analysis
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Judgment criteria in Japanese criteria (ppm)
300CO
5 0.5 0.5C2H2
100 & TCG 700 or 100 & the increasing r atioof TCG 70 per mont h
10 & TCG 500 10C2H4
150C2H6
100CH4
400H2
500TCG
Abnormal levelCaution level 2Caution level 1CriteriaItem
*1: Caution level-1The level that transformer is out of normal condi tion although it i s not judged to be abnormal
and dangerous condition*2: Caution level-2The level that transformer becomes abnormal condition gradually*3: Abnormal levelThe level that transformer i s clearly abnormal cond ition. (aggravating fu rther from Cautionlevel-2) TCG means the gap of TCG between the test and the previous test
DGA Judgment criteria in Japan
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20CO+CO2 Analysis Judgment Criteria7. Japanese assessment criteria
Ave. DP of insulation paper
( C O + C O 2 v o
l u m e )
/ ( I n s u
l a t i o n p a p e r w e i g
h t )
( m L / g )
Ave. DP=450 level(*2)
2.0mL/g
Dangerouslevel
Ave. DP=450 level(*1)
0.2mL/g
Cautionlevel
RemarksCriteriaLevel
*1 Transformer wi th DP of 450, withthe lowest CO+CO2 volume per insulation paper weight
*2 Transformer wi th DP of 450, withthe highest CO+CO2 volume per insulation paper weight
Assessment is conductedaccording to the criteria.
(CO+CO2 volume) (Insulation paper weight)
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21Furfural Analysis Judgment Criteria7. Japanese assessment criteria
Ave. DP=450 level(*2)
0.015mg/g
Dangerouslevel
Ave. DP=450 level(*1)
0.0015mg/g
Cautionlevel
RemarksCriteriaLevel
*1 Transformer wi th DP of 450, withthe lowest furfural weight per insulation paper weight
*2 Transformer wi th DP of 450, withthe highest furfural weight per insulation paper weight
( F u r f u r a
l w e i g
h t ) / ( I n s u l a
t i o n p a p e r w e i g
h t )
( m g / g
)
Ave. DP of insulation a er
Assessment is conductedaccording to the criteria.
(Furfural weight) (Insulation paper weight)
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GT assessment results of Korba#6, Rihand#2, Singlauli#6R
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23Korba#6R DGA ResultH2 CH4 C2H4 C2H6 C2H2 C3S CO CO2 TCG TCG increase
ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm/month 400 100 10 150 0.5 300 500
10 0.5 500 C2H4
10+TCG
500 orC2H2 0.5
100 700 70C2H4 100+TCG 700 or TCG 70ppm/month
Apr-1990 387 3 0 2 51 0 34 47 477 Abnormal level *1Nov-1990 11 8 0 0 0 0 82 819 101 -53.7Feb-1995 80 17 0 30 0 10 15 1723 152 1.0Sep-1995 75 16 0 22 0 23 10 1855 146 -0.9Jun-2000 85 56 50 58 0 28 381 2853 658 8.8 Caution level-2Oct-2000 84 54 52 84 0 12 398 3606 684 6.0 Caution level-2
Jul-2005 20 60 22 66 0 28 450 3810 646 -0.7 Caution level-2Oct-2005 16 70 20 70 0 30 440 3890 646 0.0 Caution level-2Jan-2006 42 60 16 67 0 25 420 3710 630 -5.5 Caution level-2Apr-2006 32 62 2 118 0 60 262 4135 536 -26.9 Caution level-1Jul-2006 23 15 1 50 0 10 130 1906 229 -99.0Oct-2006 29 24 1 26 0 8 128 1903 216 -4.9Apr-2007 16 30 2 38 0 5 91 1597 182 -5.2Jul-2007 12 42 0 45 0 10 75 2062 184 0.9Oct-2007 102 24 0 31 0 9 34 1394 200 4.9Dec-2007 91 35 0 51 0 12 43 2111 232 17.8
Mar-2008 70 30 0 29 0 8 40 1922 177 -17.6Jun-2008 71 2 2 8 0 0 127 1865 210 10.8Aug-2008 60 20 0 25 0 7 25 1229 137 -32.7Jul-2009 21 81 1 76 0 31 111 1869 321 16.8Dec-2009 18 61 2 58 0 21 109 1916 269 -9.8Mar-2010 25 32 0 33 0 2 92 1790 184 -26.8Jun-2010 21 49 3 91 0 4 112 1896 280 30.0
Date Remarks
Abnormal level
Caution level-2
Caution level-1
Recently within criteriaSo, Good condition
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y = 0.0283x
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 5 10 15 20O peration year (Years)
C
O + C O 2 ( m L / g )
Caution level =0.2
Dangerous level =2.0
(1989 Jan.)
Average RLA level = 1.1
The generation speed of CO+CO2 per insulation paper weight is estimated by approximation formula funct ion of Excel soft and the current condit ion & the RLA areestimated.
Estimation of CO+CO2 generation speed (R phase)(Korba#6)
Approximation formula of CO+CO2generation speed (ml/g-year)
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25DP estimation by CO+CO2 analysis(Korba#6)
R phase: 0.4400Y phase: 0.5194B phase: 0.6074
R phase: 335Y phase: 318B phase: 295
R phase: 652Y phase: 622B phase: 595
( C O + C O 2 v o
l u m e )
/ ( I n s u
l a t i o n p a p e r w e i g
h t ) ( m L / g )
Ave. DP of insulation paper
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26Furfural generating trend (Korba#6)
0.000
0.001
0.002
0.0030.004
0.005
0.006
0.007
0.008
0.009
0.010
0 5 10 15 20 25O peration years (years)
F u r f u r a l ( m g / g )
(Jan.1989)
R phase
Y phase
B phase
Caution Level=0.0015
Dangerous level=0.015
Average RLA leve l=0.00825
Because 2010 data is lit tle bit larger than 2009 data, furfuralgenerating speed increases.
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27DP estimation by furfural analysis (Korba#6)
DP estimation by2010 June data.
( F u r f u r a
l w e i g
h t ) / ( I n s u
l a t i o n p a p e r w e i g
h t )
( m g
/ g )
Ave. DP of insulation paper
R phase: 0.00463Y phase: 0.00541B phase: 0.00386
R phase: 335Y phase: 318B phase: 352
R phase: 675Y phase: 645B phase: 710
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28Korba#6 assessment results
Caution0.00386 mg/gB
Caution0.00541 mg/gY
Caution 0.0015 mg/gDanger 0.015 mg/g
Caution0.00463 mg/gR Furfuralanalysis
Caution0.5943 mL/gB
Caution0.5082 mL/gY
Caution 0.2 mL/gDanger 2.0 mL/g
Caution0.4305 mL/gR CO+CO 2analysis
GoodDGA dataB
GoodDGA dataY
GoodDGA dataR DGA
Good3250 M B
Good3500 M Y JP 80 M Good3500 M R IR test
Remark/standardEvaluationTest recordPhaseTest
Current condition assessment
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29Korba#6 assessment results
RLA
Nov-203445.9B
Oct-202132.8YUp to the average servicelife*2
Mar-202738.2R Fur fura l analysis
Dec.-202738.9B
Jul.-203445.5Y
Up to the average servicelife*1
Sep.-204253.7R CO+CO 2analysis
Year Operationyears
RLA
*1:The average service life point was set to 1.1 mL/g, which is the averagebetween the caution level (0.2 mL/g) and the danger level (2.0 mL/g).
*2:The average service life point was set to 0.00825 mg/g, which is theaverage between the caution level (0.0015 mg/g) and the danger level(0.015 mg/g).
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30Rihand#2 assessment results
Danger 0.07161 mg/gB
Danger 0.07161 mg/gYCaution
0.0015 mg/gDanger 0.015 mg/g
The measurement da ta isnot r eliable.
Danger 0.16328 mg/gR Furfuralanalysis
Caution0.97 mL/gB
Caution0.90 mL/gY
Caution 0.2 mL/gDanger 2.0 mL/g
Caution0.95 mL/gR CO+CO 2analysis
GoodDGA dataBGoodDGA dataY
GoodDGA dataR DGA
Good835 M B
Good979 M Y
JP 80 M Good707 M R IR test
Remark/standardEvaluationTest recordPhase
Current condition assessment
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31Rihand#2 assessment results
RLA
Not available B Not available Y
Up to the average servicelife*2The measur ement data is notreliable.
Not available R Furfuralanalysis
Nov.-201223.4B
Jul.-201425.1Y
Up to the average servicelife*1
May-201323.9R CO+CO 2analysis
Year Operationyears
PhaseTest
*1:The average service life point was set to 1.1 mL/g, which is the averagebetween the caution level (0.2 mL/g) and the danger level (2.0 mL/g).
*2:The average service life point was set to 0.00825 mg/g, which is theaverage between the caution level (0.0015 mg/g) and the danger level(0.015 mg/g).
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32Singraulii#6R assessment resultsCurrent condition assessment
JP Caution 0.0015 mg/gJP Danger 0.015 mg/gThe measur ed values are
not r eliable.
Danger 0.0283 mg/gFur fural analysis
JP Caution 0.2 mL/gJP Danger 2.0 mL/g
Caution1.38 mL/gCO+CO 2 analysis
GoodDGA dataDGA
Good300 M HV-LV
Good150 M LV-E
JP 80 M Good250 M HV-EIR test
Remark/standardEvaluationTest record
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33Singraulii#6R assessment resultsRLA
Over danger levelThe measured values are not r eliable.
Not available Furfuralanalysis
Up to the danger levelSep-201932.7
Up to the average service life*1Jun-200518.0CO+CO 2analysis
Year Operationyears
*1:The average service life point was set to 1.1 mL/g, which is the averagebetween the caution level (0.2 mL/g) and the danger level (2.0 mL/g).
*2:The average service life point was set to 0.00825 mg/g, which is theaverage between the caution level (0.0015 mg/g) and the danger level(0.015 mg/g).
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34Recommendations for GT assessment
1. Conduct DP measurement (Singrauli)To know actual GT condit ion, DP measurement of insulationpaper is effective. Conduct DP test when Singrauli GT isreplaced in order to confirm the correlation between CO/CO2 andDP.
1. Continue to conduct the tests
NTPC should conduct the tests periodically in the future so that
NTPC can grasp the deterioration trend.2. Get reliable and accurate test data
Some test data is not consistent with technical theory. Check thetest data and get reliable and accurate test data .
3. When NTPC purchases transformer, NTPC should get theinitial DP and the insulation paper weight from the manufacturer
in order to conduct CO+CO2/furfural analysis in the future.4. Accurate oil treatment records are required for CO+CO2 analysis.5. Accurate oil change records are required for Furfural analysis.
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Thank you!