omar saady

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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 RPresented by

Othman Al DarrajiDepartment of Electrical

EngineeringTAA. UniversityAnkara , Turkey

[email protected]

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

SupervisionProf. Dr. Ibrahim

MahariqDepartment of Electrical

EngineeringTAA. UniversityAnkara , Turkey

[email protected]

Turkey – Ankara 10 - 5 - 2016

University of Turkish Aeronautical Association Faculty of engineering EEE department

Presented byOmar Saadi Alshear

Department of Electrical Engineering

TAA. UniversityAnkara , Turkey

[email protected]

2T 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

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Transformer is a static device which transforms A.C electrical power from one voltage to anotherVoltage keeping The frequency same by Electromagnetic induction.


WHAT IS TRANSFORMER?


IRON CORE

WHAT IS TRANSFORMER?


DISCUSSION


TEST REQUIRMENTS


ROUTINE TESTS


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1- NAME PLATE FOR TRANSFORMER


S.N: 925 554

1 = 5 0 K V A2 = 1 0 0 K V A3 = 2 0 0 K V A4 = 3 0 0 K V A5 = 5 0 0 K V A6 = 8 0 0 K V A7 = 1 0 0 0 K V A8 = 1 5 0 0 K V A

TEST REQUIREMENTS


2-TESTING DEVICES

TEST REQUIREMENTS

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3- SAFETY EQUIPMENT

4 - MECHANICAL EQUIPMENT


TEST REQUIREMENTS


DISCUSSION


TEST REQUIRMENTS


ROUTINE TESTS




Types of testing

1- Routine tests

2- Type tests

3- Special tests

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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 TestA-Measurement of insulation resistance.

B- Dissipation power factor / insulation power factor (tan∂)

C- OIL TEST


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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.

2- TYPE TESTS


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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.


3-SPECIAL TESTS



DISCUSSION


TEST REQUIRMENTS


ROUTINE TESTS



Transformer Breakdowns


Sources of faults in transformer


Apply Tests Routine on Power Transformer

Type: 132/33 /11.5KV ,63 MVAVECT. GROUP: YnYnd11

1-ROUTINE TESTS

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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


Type: 132/33 /11.5KV ,63 MVAVECT. GROUP: YnYn0d11Rated 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

91011

132.0 (132 ⁄ √3) ⁄ 11.5 = 6.627

17 118.8



TEST:

TR.


a

N

VECT. GROUP: Ynd11 FOR H.V – L.V

b

c CBA

L.V

H.V

M.V

Ratio meter

ac

b

n

a

TR.

N

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The no-load deviation of the turn ratios should be ≤ % 0,5


APPLLY THIS LAW


23

.


The use of modern equipment


TTR (Transformer Turns Ratio)

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This test is very important for an engineer to figure out directional connectivity for transformers.

(( Dy11 ,Yd11, Dy1,Yd1))


1-2-Vector Group Verification


Dy11

Yd11


Yd1

Dy1


Steps to implement the test


STEP 2S.C

STEP 3Take V

B-b , B-c ,C-b , C-c

STEP 1Connect H.V


Dy11

Yd11

Dy1

Yd1

Dd0


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


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


Tap pos. A-Nohm

B-Nohm

C-Nohm

Resistance 3-ph

Oil Temp Rest. At 75C˚

1

9 0.4108 0.4104 0.4192 1.2305 19C˚ 1.5023

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Type: 132/33 /11.5KV ,63 MVAVECT. GROUP: YnYn0d11 FOR H.V, USES TAP POS. 1-9-17FOR M.V , USES TAP POS. 1 - 3 - 5FOR L.V , USES TAP POS. 1



Type: 132/33 /11.5KV ,63 MVAVECT. GROUP: YnYn0d11WHEATSTON BRIDGE

a

N

WIND. REST. FOR H.V

b

c CBA

L.V

H.V

M.V

WHEATSTON BRIDGE

a

cb

na

TR.

N



Where :T: CONSTANT ==234.5. for copperT1: 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˚


Type: 132/33 /11.5KV ,63 MVAVECT. GROUP: YnYn0d11VOLTMETER – AMMETERApply ohm law D.C

12V

A

A

A

C

B

C

B

BC

N

N

AH.V

M.V

L.V


V

V

V


Type: 132/33 /11.5KV ,63 MVAVECT. GROUP: YnYn0d11WINDING REST. H.V


a

N

bc CBA

L.V

H.V

M.Va

cb

na

TR.

N

2

1




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



S.C ON

L.VA A

A

Type: 132/33 /11.5KV ,63 MVAVECT. GROUP: YnYn0d11VOLTMETER - AMMETER

1-4-IMPEDANCE VOLTAGE TEST(Z)


Tap pos. A-B B-C C-A A B C

1 420V 422V 429V 3.5AMP 3.3AMP 3.4AMP

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Type: 132/33 /11.5KV ,63 MVAVECT. GROUP: YnYn0d11IMPEDANCE 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)


Why do we apply the equation below?

Z=+ -7.5% FOR TWO WINDINGSZ=+ - 10%FOR THREE WINDINGS

FOR EXAMPLE:Rated voltage =145.2kv , Rated current =250.5Applied voltage Measured current AB=420 A=3.5 BC=422 B=3.3 CA=429 C=3.4 Apply the law :


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What is the benefit of?

1- In the case of connecting a power transformer in parallel with the otherTest 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 levelFOR EXAMPLE:Rated voltage =145.2kv , Rated current =250.5



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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


1-5-Dielectrics Test


Types of dielectric tests

1- Measurement of insulation resistance

2- Dissipation power factor / insulation power factor (tan∂)

3- Test oil

1-5-Dielectrics Test


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.


Type: 132/33 /11.5KV ,63 MVAVECT. GROUP: YnYn0d11insulation resistance :( H.V—L.V)

a

N

b

c CBAL.V 11.5kv

H.V 132kv

M.V33kv

a

cb

na

TR.

N



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


1- In capacitor ideal has no losses. The electric current precedes voltage an angle of (90˚).



2- In practical, all capacitors find where the loss in insulation



TESTING

REPEAT THIS TEST: M-HLE: MEDIUM – HIGH , LOW , EARTHL-HME : LOW – HIGH , MEDIUM , EARTHH-M / H-L / M-L /

a

N

b

c CBAL.V 11.5kv

H.V 132kv

M.V33kv

a

cb

na

TR.

N

Tan


e



To find good values


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 mm3- Recommended value : 60KV 4- Equipment used : OIL BDV TEST SET.

1-5-3- OIL TEST


DISCUSSION


TEST REQUIRMENTS


ROUTINE TESTS



1- Periodic checking of any loose connections of the terminations of HV & LV side.

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.



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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Thank you for your attention!

Questions?

TESTING AND MAINTENANCE OF POWER TRANSFORMER

University of Turkish Aeronautical Association

Faculty of engineering EEE department
