SFRA,Tan Delta.HV,LV Testing

1. TRANSFORMER TESTS

2. TRANSFORMER TESTS

3. SFRA TESTS- PURPOSE
• Transformer complex of resistance,Inductance and
Capacitance Network (R,L,C)
• Resistance of copper winding (R)
• Inductance of winding Coil (L)
• Capacitance of Insulation Layer between coil (C)
• R,L,C Circuit form frequnce dependant and response
• Any Physical damage- R,L,C value changed and
frequency response changed
• Test conduct during commissioning
• 10VAC and 20KHZ to 2MHZ Source of supply

4. SFRA(FRQ RESPONSE ANAL) TEST

5. SFRA TEST

6. HV phase to Neutral and LV Short

7. LV Ph to Neutral and HV Open

8. Between HV & LV Winding

9. 2.TAN DELTA TEST
• TAN DELTA= Resitance component of Ins. Matl
Capacitive current flowing Ins.Matl
. Capacitance Value,Tan Delta(Dissipation factor)
. Change of Capacitance indicate Moisture,Short
and open circuit in winding
. Insulating Loss α Squre of the applied voltage

10. TAN DELTA CONNECTION

14. Transformer Bushing Insulation Test

15. MEASUREMENT OF TAN DELTA &
CAPACITANCE (winding)
• Ambient temp: 35 C
Top oil temp: 48 C
WINDING Test mode Applied
Voltage
Current
(mA)
Capacitance (pF)
Dissipation factor (Tan Delta (%)
Correction factor K= 1.75
@ 46 Dec @ 20 Dec
LV to Earth
UST-R 3.0 kv 4.467 4756.41 0.5123 0.2927
UST-R 6.0 kv 8.955 4756.75 0.5103 0.2916
HV to Earth
GST-GND 5.0 kv 17.96 11421.9 0.5006 0.2860
GST-GND 10.0kv 35.81 11425.4 0.5043 0.2881
HV to LV
UST-R 5.0kv 7.450 4757.18 0.5127 0.2929
UST-R 10.0kv 14.876 4741.3 0.5 169 0.2953

16. BUSHING Make: CGL Rated Amps
1250A Rated Volts 145kv
BUSHING Test mode Applied
Voltage
Current
(mA)
Capacitance (pF)
Dissipation factor (Tan Delta (%)
Correction factor K= 1.75
@ 46 Dec @ 20 Dec
‘U’-145101008
UST-R 5.0kv 0.408 260.36 0.2515
UST-R 10.0kv 0.817 260.34 0.2517
‘V’-145100923
UST-R 5.0kv 0.407 259.07 0.2477
UST-R 10.0kv 0.812 259.04. 0.2466
‘W’-145101009
UST-R 5.0kv 0.403 257.21 0.1778
UST-R 10.0kv 0.807 257.15 0.1836

18. Procerdure for Voltage & Turns Ratio
Test

19. Voltage & Turns Ratio Test

20. RATIO TESTS: (110000/11000)
(RATIO BY VOLTAGE METHOD)
Tap
HV
Voltage
Applied voltage on HV Measured Voltage Calculated
Ratio1U1V 1V1W 1W1U 2U-2N 2V-2N 2W-2N
1 121000 404 407 404 36.6 36.6 36.7 36.9
2 119625 404 407 404 36.9 37.0 37.1 37.1
3 118250 404 407 404 37.3 37.5 37.4 37.6
4 116875 404 407 404 37.8 38.0 38.0 38.1
5 115500 404 407 404 38.3 38.4 38.5 38.6
6 114125 404 407 404 38.9 39.0 39.0 39.1
7 112750 404 407 404 39.2 39.4 39.4 39.6
8 111375 404 407 404 39.7 39.9 40.0 40.0
9N 110000 404 407 404 40.4 40.4 40.4 40.5
10 108625 404 407 404 40.7 40.9 40.9 41.1
11 107250 404 407 404 41.3 41.5 41.5 41.6
12 105875 404 407 404 41.8 41.9 42.0 41.8
13b 104500 404 407 404 42.5 42.7 42.7 42.7
14 103125 404 407 404 43.0 43.3 43.3 43.2
15 101750 404 407 404 43.7 43.9 43.9 43.9
16 100375 404 407 404 44.3 44.4 44.5 44.4
17 99000 404 407 404 44.9 45.2 45.2 45.1
18 97625 404 407 404 45.6 45.8 45.8 45.7
19 96250 404 407 404 46.4 46.5 46.6 46.4
20 94875 404 407 404 47.0 47.2 47.2 47.1
21 93500 404 407 404 47.5 47.6 47.6 47.7
22 92125 404 407 404 48.3 48.5 48.6 48.4
23 90750 404 407 404 49.1 49.3 49.3 49.5
24 89375 404 407 404 49.9 50.0 49.9 50.0
25 88000 404 407 404 50.6 50.8 50.8 50.8

21. MAGNETESING CURRENT TEST
• Mesure
• Defect of Magnetic core structure
• Shiting of winding
• Failure of Turn to Turn insulation
• Problems in tap changer

22. MAGNETESING CURRENT TEST

23. MAGNETESING CURRENT TEST
• Apply 3-ph 415 V or 1-phase 230 V 0n HV or
LV keeping other side OPEN
HV side
LV side
Applied voltage Current measured Applied voltage Current measured
UN / UV = 389 4.82 mA un / uv = 206 170 mA
VN / VW = 392 3.10 mA vn / vw = 206 85 mA
WN / WU = 389 6.40 mA wn / wu = 206 96 mA

24. Magnetic Balance Test
• Rph Voltage = Y Ph Voltage + B Ph voltage

25. Magnetic Balance Test
• Apply 1-phase 230 V on HV and LV side
(whichever is have neutral) between phase
and neutral and
1U1N
1U1V
1U1N
1V1W
1W1N
1W1U
2U2N
2U2V
2V2N
2V2W
2W2N
2W2U
389 348 45
212 392 179
47 347 389

26. Polarity Test

28. IR value between Applied Voltage
IR value for
15 secs
IR value for
60 secs
Ir Value for
600 secas
PI 600/60
LV to Earth 5000 2.71 G Ω 4.64 G Ω 8.77 G Ω 1.89
HV to Earth 5000 3.19 G Ω 4.39 G Ω 7.20 G Ω 1.64
HV to Lv 5000 8.09 G Ω 9.30 G Ω 17.20 G Ω 1.84

32. BDV TEST (OIL TEST)

33. BDV TEST FINAL
Sample Taken Date Weather condition BDV
Main tank Bottom oil 23 09 2017 Good 60 KV
OLTC tank 23 09 2017 Good 54 KV