Presentation Roizman Davydov Modified

8/9/2019 Presentation Roizman Davydov Modified

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Temperature Rise Tests

Centre for Power Transformer Monitoring, Diagnostics

and Life Management (transformerLIFE)

Monash University, Australia

Oleg RoizmanIntellPower, Australia

Spring 2009 IEEE Transformers Committee Meeting

Miami FL, 21 April 2009

Valery DavydovMonash University


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Special Test Transformer Nameplate Data

Year of Manufacture 2006

Rated Power HV/MV for ONAN,

kVA

468/468

Rated Voltage HV/MV/LV, kV 22/4.5/0.415

Rated Current HV/MV Amp 12.3/60.0

Cooling Types ONAN, ONAF,

OFAF

Number of Phases 3

Vector Symbol YNyn0yn0

Mass Untanking, kg 2420

Mass Each Cooler (excluding oil), kg 115

Mass Total (including oil), kg 6850

Insulating Oil Each Cooler, l 43

Insulating Oil Total, litre 2650

Oil Circulation, l/min 1200


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Temperature Sensors and DAQ System

16 Fiber Optic sensors

24 Thermocouples, including magnetic and thermalribbon types

9 RTDs, including those of moisture/temperature

transmitters

More than 60 channels of information stored at 1 min

interval


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Location of Thermocouples and RTDs

in Test TransformerTop Oil Temperatures

Top Core Yoke Temperatures

Top Rings Temp

Top Radiator

Bottom Radiator


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Location of Fibre Optic Probes and Core

Thermocouples


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Fibre Optic Probe Installation

in MV Winding, Phase B


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Fibre Optic Probe Installation in HV Winding


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Effect of Measuring Instrumentation

In the following 4 slides, comparisons are made for

the two windings of Phase B (OFAF)

MV (layer type) HV (disc type)

The comparisons are made for results obtained during

the Temperature Rise Tests conducted at Monash

using two different instrumentation sets for windingresistance measurement


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Comparison of Tavr and FO for MV OFAFPhase B, 100A

30

35

40

45

50

55

60

65

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

t, min

T

,deg

C

FO12 MV top FO13 MV middle FO14 MV bottom wm(i) as measured w(i) as calculated

Avr wnd. T

Top wnd. temp

Mid wnd. temp

Bot wnd. T

1st set of winding resistance measurement instrumentation was used


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Comparison of Tavr and FO for HV OFAFPhase B, 100A

35

37

39

41

43

45

47

49

51

0 2 4 6 8 10 12 14 16

t, min

T,

deg

C

FO7 HV top FO9 HV middle FO11 HV bottom

Measured average winding temperature Calculated average winding temperature

Tawr

1st set of winding resistance measurement instrumentation was used


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OFAF (100A) HV Phase B

60

65

70

75

80

85

90

0:00:00 0:02:53 0:05:46 0:08:38 0:11:31 0:14:24 0:17:17 0:20:10 0:23:02

Twarm Twarm fitted IEC 20mins Twarm fitted IEC 15mins Twarm fitted IEC 5mins

Twarm fitted exp 5mins FO7 FO1 FO9

2nd set of winding resistance measurement instrumentation was used


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OFAF(100 A) MV Phase B

60

70

80

90

100

110

120

0:00:00 0:02:53 0:05:46 0:08:38 0:11:31 0:14:24 0:17:17 0:20:10 0:23:02Time since shu t down (mins)

T,

degC

Twarm Twarm fitted IEC 20mins Twarm fitted IEC 15mins Twarm fitted IEC 5mins

Twarm fitted exp 5mins FO13 FO12 FO14

It could be seen that depending on duration of test variations in Twnd (R) is ~10 C



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Blocked Coolers: 60A

70

72

74

76

78

80

82

84

86

88

90

7:12 8:24 9:36 10:48 12:00 13:12 14:24 15:36 16:48 18:00 19:12

T,

degC

FO6 FO15 FO16

Blocked Coolers 60 A

Phase A Phase C Phase B

~4 hours!


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Blocked Coolers: 60 A

Blocked Cooling

68

70

72

74

76

78

80

82

84

0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36

T,

degC

Twarm A Twarm fitted IEC (A) Twarm C Twarm fitted IEC Twarm B Twarm fitted IEC (B)

Ph A

Ph C

Ph B

76.59+time*0.1618-4.331)exp(-time/*5.521=Tw



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Blocked Coolers HV Phase B 60A

45

50

55

60

65

70

75

80

85

90

0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36

Time since shutdown (mins)

T,

degC

Twarm FO7 FO9 FO11 (TV4+TV5)/2

hottest measured temp mid measured temp

bottom measured tempWinding temp by

resistance


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ONAN(60A) HV phase B

45

50

55

60

65

70

0:00:00 0:02:53 0:05:46 0:08:38 0:11:31 0:14:24 0:17:17


T,

degC

Twarm Twarm fitted IEC 15mins Twarm fitted IEC 5mins Twarm fitted exp 5mins FO9 FO3 FO11



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ONAN(60A) MV phase B

40

45

50

55

60

65

70

75

0:00:00 0:02:53 0:05:46 0:08:38 0:11:31 0:14:24 0:17:17


T,degC

Twarm Twarm fitted IEC 15mins Twarm fitted IEC 5mins Twarm fitted exp 5mins FO12 FO13 FO14



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Comparison of FO Data for Phases A, B & C

In the following slide a comparison is made for Phases A, B

and C for the HV (disc type) winding for the OFAF cooling

mode

The comparison is made for the measurements obtained

during the Temperature Rise Tests conducted at Monash for

the FO probes installed in the 2nd top disc of Phases A, B & C

The differences in the FO measurement results wereobserved due to the following reasons:

Phase A is the most remote phase from the oil inlet pipe; the velocity

of oil flow through the winding ducts of Phase A is the lowest

Phase C is the closest phase to the oil inlet pipe; the velocity of oil flowthrough the winding ducts of Phase C is the highest

Phase B is in the middle between the inlet pipe and Phase A


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FO Sensors Data for Phases A, B and C

OFAF (100A)

55

60

65

70

75

80

85

90

95

8:24 9:36 10:48 12:00 13:12 14:24 15:36 16:48 18:00

Time, h:mm

Temperatu

re,

degC

FO6 FO15 FO16

Phase A

Phase B

Phase C

Cooling curves


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Cooling Curves for A, B and C Phases,

OFAF (100A), HV

60

65

70

75

80

85

90

0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36

Time since shutdown, min

Windingtempe

rautrebyR,

degC

Phase B Phase C Phase A



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Effect of first valid time point for MV in OFAF

60

65

70

75

80

85

90

0:00:00 0:02:53 0:05:46 0:08:38 0:11:31 0:14:24 0:17:17 0:20:10 0:23:02


T,

deg

C

Twarm Twarm fitted IEC 20mins (from 1m45s) Twarm fitted IEC 20mins (from 4m)

1:45 min

4:00 min


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Factors Affecting Winding Temperature Rise

Winding resistance measuring equipment

Ambient temperature determination Inadequate calculation of the average oil

temperature (leads to wrong g factor)

Accuracy of Load Loss measurement Assumed total loss as sum of NL + LL

Effect of the Core temperature dynamics

Cold resistance measurement errors Not reaching steady state before shutdown


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Factors Affecting Winding Temperature Rise

(contd)

Connection circuit (two windings at a time) Time interval first and last data point resistance

measurement

Fitting curve method

Ambient oil temperature consideration


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Conclusions

Depending on winding time constant taking first

resistance measurement at 4 min may be too long wait

and could lead to significant error in determination of

winding temperature at shutdown

10 min cooling curve period could be well justified for

small and medium distribution transformers, but does not

seem to be adequate for large power transformers,where 20 min should be considered as more appropriate

15 sec acquisition rate was found to be easily

achievable with the modern acquisition systems and is

recommended, especially for a winding with a short time

constant


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Conclusions (Contd)

Considerations should be given to the followingrecommendations when FO sensors are used:

a. Number and locations of FO temperature probes should be determined

on the basis of analysis of heat and mass transfer with assistance ofnumerical methods such as FEM and CFD;

b. Hot-spot temperature should be continuously measured by FO sensorsinstalled in each winding of each phase and verified by calculations inaccordance with the latest relevant standards and/or more detailed in-house thermo-hydraulic models;

c. Average winding temperature rise by resistance should be measuredonly in the winding of the phase with the highest hot-spot temperaturefound in b) unless the difference between that temperature and theaverage of all phases exceeds agreed value (e.g. 3 C).

Presentation Roizman Davydov Modified

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