University of Turkish Aeronautical Association
Faculty of engineering EEE department
Supervision Presented by Presented by
Prof. Dr. Ibrahim Othman Al Darraji Omar Saadi Alshear
Mahariq Department of Electrical Department of Electrical
Department of Electrical Engineering Engineering
Engineering TAA. University TAA. University
TAA. University Ankara , Turkey Ankara , Turkey
Ankara , Turkey otomn_kh@yahoo.com omarsaad529@gmail.com
ibmahariq@gmail.com
Turkey – Ankara 10 - 5 - 2016
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
Transformer is a static device which
transforms A.C electrical power from one
voltage to another
Voltage keeping
The frequency same by
Electromagnetic induction
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
IRON CORE
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
TEST REQUIREMENTS
1- NAME PLATE FOR TRANSFORMER
S.N: 925 554
1=50KVA
2=100KVA
3=200KVA
4=300KVA
5=500KVA
6=800KVA
7=1000KVA
8=1500KVA
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
TEST REQUIREMENTS
2-TESTING DEVICES
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
TEST REQUIREMENTS
3- SAFETY EQUIPMENT
4 - MECHANICAL EQUIPMENT
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
TESTING OF TRANSFORMER
Types of testing
1- Routine tests
2- Type tests
3- Special tests
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
TESTING OF TRANSFORMER
1-ROUTINE TESTS
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
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
TESTING OF TRANSFORMER
2- TYPE TESTS
THESE TESTS ARE CARRIED OUT ON ONE TRANSFORMER OF
THE LOT.
2.1- All routine tests.
2.2- Additionally following tests are included in type
tests.
A- Lightening impulse test.
B- Temperature rise test.
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TESTING OF TRANSFORMER
3-SPECIAL TESTS
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.
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
Transformer Breakdowns
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
Sources of faults in transformer
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-ROUTINE TESTS
Apply Tests Routine on Power Transformer
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYnd11
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-1-Measurement of voltage ratio
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)
6- Equipment used : Transformer Turns Ratiometer ( T T R)
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-1-Measurement of voltage ratio
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 (A-N) / (a-c) (B-N) / (b-a) (C-N) / (c-b) Rated Ratio
(kv) (Measured (Measured (Measured (Rated value )
value) value) value)
1 145.2 / 11.5
9 132.0 (132 ⁄ √3) ⁄ 11.5 = 6.627
10
11
17 118.8
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-1-Measurement of voltage ratio
TEST:
VECT. GROUP: Ynd11 FOR H.V – L.V
H.V
N A B C a
cN
b M.V
L.V TR.
b TR.
c
a n
Ratio meter
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-1-Measurement of voltage ratio
APPLLY THIS LAW
The no-load deviation of the turn ratios
should be ≤ % 0,5
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-1-Measurement of voltage ratio
The use of modern equipment
TTR (Transformer Turns Ratio) 23
TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-2-Vector Group Verification
This test is very important for an engineer to figure out
directional connectivity for transformers.
(( Dy11 ,Yd11, Dy1,Yd1))
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
Dy11
Yd11
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
Dy1
Yd1
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-2-Vector Group Verification
Steps to implement the test
STEP 1
Connect H.V
STEP 2
S.C
STEP 3
Take V
B-b , B-c ,C-b , C-c
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
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
Dy11 Dy1 Dd0
Yd11 Yd1
Yy0
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-3-Measurement of winding resistance
D.C RESISTANCE
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.
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-3-Measurement of winding resistance
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
Tap pos. A-N B-N C-N Resistance Oil Temp Rest. At
ohm ohm ohm 3-ph 75C˚
9 0.4108 0.4104 0.4192 1.2305 19C˚ 1.5023
17
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-3-Measurement of winding resistance
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
WHEATSTON BRIDGE
WIND. REST. FOR H.V
H.V
N A B C c
c
b M.V
L.V b TR.
a
a n
WHEATSTON BRIDGE
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
RESISTANCE WINDINGS AT 75 C˚
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
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-3-Measurement of winding resistance
A V
A
Type: 132/33 / 11.5KV ,63 MVA H.V
B N
VECT. GROUP: YnYn0d11 C
VOLTMETER – AMMETER
A
Apply ohm law D.C
12V
V
B N
M.V
C
A
V L.V
C B
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-3-Measurement of winding resistance
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
WINDING REST. H.V
The use of modern equipment
H.V
2
1
N A B C c
c
TR. b
L.V b
a
a n M.V
The use of modern equipment
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-3-Measurement of winding resistance
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
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-4-IMPEDANCE VOLTAGE TEST(Z)
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
VOLTMETER - AMMETER
A
A A
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
IMPEDANCE VOLTAGE TEST(Z)
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.
Tap pos. A-B B-C C-A A B C
1 420V 422V 429V 3.5AMP 3.3AMP 3.4AMP
17
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
IMPEDANCE VOLTAGE TEST(Z)
Why do we apply the equation below?
FOR EXAMPLE:
Rated voltage =145.2kv , Rated current =250.5
Applied voltage Measured current Z=+ -7.5% FOR TWO
AB=420 A=3.5 WINDINGS
BC=422 B=3.3
CA=429 C=3.4 Z=+ - 10%FOR THREE
Apply the law : WINDINGS
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
IMPEDANCE VOLTAGE TEST(Z)
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
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-Dielectrics Test
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
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-Dielectrics Test
Types of dielectric tests
1- Measurement of insulation resistance
2- Dissipation power factor / insulation power factor (tan∂)
3- Test oil
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-1- Measurement of insulation resistance.
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.
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-1- Measurement of insulation resistance.
Type: 132/33 / 11.5KV ,63 MVA
VECT. GROUP: YnYn0d11
insulation resistance :( H.V—L.V)
H.V 132kv
N A B C c
c
L.V 11.5kv b
b TR.
a
a n
M.V33kv
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-1- Measurement of insulation resistance.
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-2-Dissipation power factor
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.
132 kv
33 kv
11.5 kv
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-2-Dissipation power factor
1- In capacitor ideal has no losses. The electric current
precedes voltage an angle of (90˚).
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-2-Dissipation power factor
2- In practical, all capacitors find where the loss in
insulation
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-2-Dissipation power factor
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-2-Dissipation power factor
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-2-Dissipation power factor
TESTING H.V 132kv
N A B C c
c
L.V 11.5kv b
b TR.
a
a n
M.V33kv
e
REPEAT THIS TEST: Tan
M-HLE :MEDIUM – HIGH , LOW , EARTH
L-HME : LOW – HIGH , MEDIUM , EARTH
H-M / H-L / M-L / 50
TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-2-Dissipation power factor
To find good values
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
1-5-3- OIL TEST
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.
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
DISCUSSION
DEFINITION OF THE TRANSFORMER
TEST REQUIRMENTS
TESTING OF TRANSFORMER
ROUTINE TESTS
REGULAR MAINTENANCE FOR POWER TRANSFORMERS
53
TESTING AND MAINTENANCE OF POWER TRANSFORMER
Regular maintenance for power transformers
1- Periodic checking of
any loose connections of
the terminations of HV &
LV side.
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
Regular maintenance for power transformers
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.
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
Regular maintenance for power transformers
5- Regular inspection of OIL &
WINDING TEMPERATURE METER
readings.
6- Cleanliness in the Substation yard
with all nets, vines, shrubs removed.
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
University of Turkish Aeronautical
Association
Faculty of engineering EEE department
TESTING AND MAINTENANCE OF POWER
TRANSFORMER
Thank you for your
attention!
Questions?
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TESTING AND MAINTENANCE OF POWER TRANSFORMER
