TESTING AND MAINTENANCE OF POWER TRANSFORMER

1. Presented by
Othman Al Darraji
Department of Electrical
Engineering
TAA. University
Ankara , Turkey
otomn_kh@yahoo.com
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
Supervision
Prof. Dr. Ibrahim
Mahariq
Department of Electrical
Engineering
TAA. University
Ankara , Turkey
ibmahariq@gmail.com
Turkey – Ankara 10 - 5 - 2016
University of Turkish Aeronautical Association
Faculty of engineering EEE department
1
Presented by
Omar Saadi Alshear
Department of Electrical
Engineering
TAA. University
Ankara , Turkey
omarsaad529@gmail.com

2. 2
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS

3. 3
Transformer is a static device which
transforms A.C electrical power from one
voltage to another
Voltage keeping
The frequency same by
Electromagnetic induction
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R

4. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
4
IRON CORE

5. 5
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS

6. 6
1- NAME PLATE FOR TRANSFORMER
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
S.N: 925 554
1 = 5 0 K V A
2 = 1 0 0 K V A
3 = 2 0 0 K V A
4 = 3 0 0 K V A
5 = 5 0 0 K V A
6 = 8 0 0 K V A
7 = 1 0 0 0 K V A
8 = 1 5 0 0 K V A
TEST REQUIREMENTS

7. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
7
2-TESTING DEVICES
TEST REQUIREMENTS

8. 3- SAFETY EQUIPMENT
4 - MECHANICAL EQUIPMENT
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
8
TEST REQUIREMENTS

9. 9
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS

10. 10
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
TESTING OF TRANSFORMER
Types of testing
1- Routine tests
2- Type tests
3- Special tests

11. 1-ROUTINE TESTS
11
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1.1- Measurement of voltage ratio
1.2-Vector group verification
1.3-Measurement of winding resistance
1.4-Impedance voltage test(z)
1.5-Dielectrics Test
A-Measurement of insulation resistance.
B- Dissipation power factor / insulation power factor (tan∂)
C- OIL TEST
TESTING OF TRANSFORMER

12. THESE TESTS ARE CARRIED OUT ON ONE TRANSFORMER OF
THE LOT.
12
2.1- All routine tests.
2.2- Additionally following tests are included in type
tests.
A- Lightening impulse test.
B- Temperature rise test.
2- TYPE TESTS
TESTING OF TRANSFORMER

13. 13
3.1- Measurement of zero Phase sequence.
3.2- Measurement of acoustic noise level.
3.3- Measurement of harmonics of the no load current.
3.4- Magnetic balance test.
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
3-SPECIAL TESTS
TESTING OF TRANSFORMER

14. 14
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS

15. 15
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
Transformer Breakdowns

16. 16
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
Sources of faults in transformer

17. 17
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R

18. 18
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
Apply Tests Routine on Power Transformer
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYnd11
1-ROUTINE TESTS

19. 19
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
6- Equipment used : Transformer Turns Ratiometer ( T T R)
1- This test measures the voltage ratio as per the customer’s
requirement.
2- V1/V2 = N1/N2
3-The voltage ratio is equal to the turns ratio in a transformer. Using
this principle, the turns ratio is measured with the help of a turns ratio
meter. If it is correct , then the voltage ratio is assumed to be correct.
4- apply the rated ratio for all tab (1-17).
5-apply the rated ratio for (132 kv,33kv 11kv)
1-1-Measurement of voltage ratio

20. 20
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
Rated ratio (Ynd11)H.V-L.V=( 132/ √3 ) / 11.5=6.6227 FOR TAP (9)
Tap pos. TAP Voltage
(kv)
(A-N) / (a-c)
(Measured
value)
(B-N) / (b-a)
(Measured
value)
(C-N) / (c-b)
(Measured
value)
Rated Ratio
(Rated value )
1 145.2 / 11.5
9
10
11
132.0 (132 ⁄ √3) ⁄ 11.5 = 6.627
17 118.8
1-1-Measurement of voltage ratio

21. 21
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
TEST:
TR.
1-1-Measurement of voltage ratio
a
N
VECT. GROUP: Ynd11 FOR H.V – L.V
b
c
CBA
L.V
H.V
M.V
Ratio meter
a
c
b
n
a
TR.
N

22. The no-load deviation of the turn ratios
should be ≤ % 0,5
22
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
APPLLY THIS LAW
1-1-Measurement of voltage ratio

23. .
23
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
The use of modern equipment
1-1-Measurement of voltage ratio
TTR (Transformer Turns Ratio)

24. This test is very important for an engineer to figure out
directional connectivity for transformers.
(( Dy11 ,Yd11, Dy1,Yd1))
24
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1-2-Vector Group Verification

25. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
25
Dy11
Yd11

26. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
26
Yd1
Dy1

27. 27
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
Steps to implement the test
1-2-Vector Group Verification
STEP 2
S.C
STEP 3
Take V
B-b , B-c ,C-b , C-c
STEP 1
Connect H.V

28. 28
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
Dy11
Yd11
Dy1
Yd1
Dd0
1-2-Vector Group Verification
C-b > C-c ≈ B-b ≈ B-c B-c > B-b ≈ C-c ≈ C-b B-c ≈ C-b>B-b ≈ C-c
Yy0

29. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
29
This test measures the resistance of the H.V , M.V& L.V
winding. The values of resistance should be balance for all
three phases and should match the designed values.
Equipment used : Digital resistance meter.
1-3-Measurement of winding resistance
D.C RESISTANCE

30. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
30
Tap pos. A-N
ohm
B-N
ohm
C-N
ohm
Resistance
3-ph
Oil Temp Rest. At
75C˚
1
9 0.4108 0.4104 0.4192 1.2305 19C˚ 1.5023
17
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
FOR H.V, USES TAP POS. 1-9-17
FOR M.V , USES TAP POS. 1-3 -5
FOR L.V , USES TAP POS. 1
1-3-Measurement of winding resistance

31. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
31
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
WHEATSTON BRIDGE
a
N
WIND. REST. FOR H.V
b
c
CBA
L.V
H.V
M.V
WHEATSTON BRIDGE
a
c
b
n
a
TR.
N
1-3-Measurement of winding resistance

32. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
32
Where :
T: CONSTANT ==234.5. for copper
T1: 75C˚
T2: The temperature at which the
measurement (19C ˚).
Rt1: Resistance value at the temperature
(75C ˚).
Rt2: Resistance value at measured
temperature
Rt1=1.502326 ohm
RESISTANCE WINDINGS AT 75 C˚

33. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
33
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
VOLTMETER – AMMETER
Apply ohm law D.C
12V
A
A
A
C
B
C
B
BC
N
N
A
H.V
M.V
L.V
1-3-Measurement of winding resistance
V
V
V

34. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
34
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
WINDING REST. H.V
The use of modern equipment
a
N
b
c CBA
L.V
H.V
M.Va
c
b
n
a
TR.
N
2
1
1-3-Measurement of winding resistance
The use of modern equipment

35. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
35
What is the benefit of?
1- It is to compare the design calculations in terms of volumes
conductors used
2- Resistance winding test used in calculating copper losses
1-3-Measurement of winding resistance

36. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
36
A A
A
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
VOLTMETER - AMMETER
1-4-IMPEDANCE VOLTAGE TEST(Z)

37. 37
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
Tap pos. A-B B-C C-A A B C
1 420V 422V 429V 3.5AMP 3.3AMP 3.4AMP
9
17
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
IMPEDANCE VOLTAGE (Z) :( H.V—L.V) (1,9,17) TAP POS.
IMPEDANCE VOLTAGE (Z) :( H.V—M.V) (1,9,17) TAP POS.
IMPEDANCE VOLTAGE TEST(Z)

38. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
38
Why do we apply the equation below?
Z=+ -7.5% FOR TWO
WINDINGS
Z=+ - 10%FOR THREE
WINDINGS
FOR EXAMPLE:
Rated voltage =145.2kv , Rated current =250.5
Applied voltage Measured current
AB=420 A=3.5
BC=422 B=3.3
CA=429 C=3.4
Apply the law :
IMPEDANCE VOLTAGE TEST(Z)

39. 39
What is the benefit of?
1- In the case of connecting a power transformer in parallel with the other
Test engineer must calculate the value of impedance. A impedance value should
be close.
2- When measuring three windings currents, they are roughly equal. In the case
of a damage in one winding .the current size. it will be bigger than two windings
remaining. This gives an indication of the presence of a defect in winding.
3- Read the short circuit level
FOR EXAMPLE:
Rated voltage =145.2kv , Rated current =250.5
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
IMPEDANCE VOLTAGE TEST(Z)

40. 40
The dielectrics are separation between the parts of the
electrical system, and it may be solid or gaseous or liquid or
free space , and there is no insulating material full electrical
insulation , there is a certain electric current passes through it ,
in spite of the low value of the electric current .You should
know the value of this electric current.
The dielectric value less over a period of time. Because of their
exposure to different pressures
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1-5-Dielectrics Test

41. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
41
Types of dielectric tests
1- Measurement of insulation resistance
2- Dissipation power factor / insulation power factor (tan∂)
3- Test oil
1-5-Dielectrics Test

42. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
42
1- Measures the insulation resistance of HV & LV windings with respect
to earth (body) and between LV & HV winding.
2- Voltage used: 1000 V to 5000 V
3- Recommended Values are ( M)Ohms for HV & 500 Mohms for LV.
4- Equipment used: MEGGER IS USED.
1-5-1- Measurement of insulation resistance.

43. 43
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
insulation resistance :( H.V—L.V)
a
N
b
c
CBA
L.V 11.5kv
H.V 132kv
M.V33kv
a
c
b
n
a
TR.
N
1-5-1- Measurement of insulation resistance.

44. 44
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1-5-1- Measurement of insulation resistance.

45. 45
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
this test done on the electrical transformer to see the quality
of isolators used in the TRANSFORMER WINDINGS . and
isolators operate among themselves capacitors as in the
illustration.
1-5-2-Dissipation power factor
132 kv
33 kv
11.5 kv

46. 46
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1- In capacitor ideal has no losses. The electric current
precedes voltage an angle of (90˚).
1-5-2-Dissipation power factor

47. 47
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
2- In practical, all capacitors find where the loss in
insulation
1-5-2-Dissipation power factor

48. 48
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1-5-2-Dissipation power factor

49. 49
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1-5-2-Dissipation power factor

50. 50
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
TESTING
REPEAT THIS TEST:
M-HLE :MEDIUM – HIGH , LOW , EARTH
L-HME : LOW – HIGH , MEDIUM , EARTH
H-M / H-L / M-L /
a
N
b
c
CBA
L.V 11.5kv
H.V 132kv
M.V33kv
a
c
b
n
a
TR.
N
Tan
1-5-2-Dissipation power factor
e

51. 51
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1-5-2-Dissipation power factor
To find good values

52. 52
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1- Oil breakdown voltage is checked
as per IS-335.
100 mm L X 70 mm B X 80 mm Ht.
glass pot.
500ml Oil sample.
2- Spherical electrodes with gap of 2.5
mm
3- Recommended value : 60KV
4- Equipment used : OIL BDV TEST SET.
1-5-3- OIL TEST

53. 53
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS

54. 54
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
1- Periodic checking of
any loose connections of
the terminations of HV &
LV side.
Regular maintenance for power transformers

55. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
55
2-Breather examination.
Dehydration of Silica gel if
necessary.
3-Explosion vent diaphragm
examination.
4-Conservator to be cleaned
from inside after every three
years.
Regular maintenance for power transformers

56. T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R
56
5- Regular inspection of OIL &
WINDING TEMPERATURE METER
readings.
6- Cleanliness in the Substation yard
with all nets, vines, shrubs removed.
Regular maintenance for power transformers

57. 57
Thank you for your
attention!
Questions?
TESTING AND MAINTENANCE OF POWER
TRANSFORMER
University of Turkish Aeronautical
Association
Faculty of engineering EEE department
T E S T I N G A N D M A I N T E N A N C E O F P O W E R T R A N S F O R M E R