Power Transformer Test

Commissioning Service Department Commissioning Standard Test Formats Description: TEST

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INDEX Item Description Remarks 1 General name plate details 2 Mechanical check and visual inspection 3 Transformer turns ratio test 4 Capacitance & tan delta of winding 5 Magnetizing current test 6 Magnetic balance test 7 Vector group test 8 Single phase impedance 9 Short circuit test (impedance measurement) 10 Winding resistance test 11 Zero sequence impedance test 12 Insulation resistance test of transformer winding & polarizing index test 13 Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

ENG.

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Core insulation test 14 Testing of fans 15 Oil & winding temperature gauge calibration 16 Winding temperature calibration by secondary current injection 17 Mcb & thermal overload testing 18 Supervision equipment functional checks 19 Oil breakdown test

20 OLTC function test 21 Function of fan accessories 1. NAME PLATE DETAILS: Si No. : Make : Power capacity : Voltage rating : Vector group % Impedance at nominal tap : Normal tap Frequency : No. Of winding Primary current : Tested by: Signature & Date:

ENG.

/ /

/ /

MVA V

: % : HZ :

Witnessed by: Signature & Date:

ENG.

Commissioning Service Department Commissioning Standard Test Formats Description: TEST

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Secondary current Type of cooling No. of H.V taps

Ite m 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Record No.: Sheet: 3 of 27 Substation No :

: : :

/

/

2. MECHANICAL CHECK AND VISUAL INSPECTION: (As per TCS – P -105.Rev – 01, Item no 3.1.1) Description Inspect for physical damage/defects Check nameplates information as per contract specification Check quality for paint work, condition of lifting lugs, quality of weld areas rust spots and wheel stoppers Check tightness of all bolted connections Check impact recorder for any abnormal impact during transportation Check integrity of diagram/airbag in the conservator Check piping to buchholz relay has proper slope Check that all grounding are securely connected Check vertical/horizontal clearance of live parts to adjacent grounded point to conform standard Check the valves between the tank and radiator Check the H.V – L.V and Tertiary bushing for any damage and completeness Check phase marking in cable box and it should match with GIS and cables Perform all the manufacturer specific checks Check all pipes - hoses and fan protection(not rubber or plastic) Check the color and quantity of silica gel in breather and oil pot level Check labeling of all auxiliary devices as per approved drawings Check proper operation of all auxiliary devices Check oil leakage by applying 0.35 bar (35KPa) over pressure for 24 Hrs Check the oil sampling devices are reachable from ground level Check oil level in main tank, conservator, tap changer tank and bushing etc Check all external wiring for correctness and tightness Bleed trapped air at the bushing turrets and tank top Check flow of oil in flow meter in correct direction and proper rate Check that the temperature sensor oil well is two third filled with

Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

ENG.

Checked

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oil Check the each optical feed through unit is properly connected to the ports of Hot Spot Temp Measuring device For new transformer, Internal inspection of the H.V. bushing before installation is required due to upper yoke any bents in the core and if any paint particles found

Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

ENG.

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3. ELECTRICAL TEST: (As per TCS – P -105.Rev – 01, Item no 3.1.2,) Instrument : Megger 520 Average oil temperature : c 3.1

Core insulation Resistance Tested with 1000 VDC Insulation resistance between Core to ground Main core frame to earth

Insulation resistance with 1000 V tester (G ohms) (1 mins)

3.2Winding Insulation Resistance Test & Polarizing Index Tested with : 5000 VDC Insulation resistance between

1 Mins ( GΩ )

10 Mins

Polarizing index

( GΩ )

HV – ground LV – ground TW – ground HV – LV HV – TW LV – TW Criteria: Polarization Index (I.R at 10 min / I.R at 1 Min) Value > 1.3 4. WINDING RESISTANCE (DC) TEST AT ALL TAPS Instrument Oil temperature Injecting Current

Tested by: Signature & Date:

ENG.

: C

: :

A

Witnessed by: Signature & Date:

ENG.

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4.1 HV Winding Ambient Temperature: Tap no.

Winding resistance () @ amb temp. R-N Y-N B-N

Avg Res /ph @ amb temp ()

* res /ph @ 75  c ()

Factory Avg res @ 75˚c

(235 + 75) Res / Ph @ 75  C. = Avg. Res / Ph @ Amb. Temp. X -------------------------*

(235 + Avg Oil Temp.) 4.2 Tap no.

LV Winding

Winding resistance () @ ambient temp.

Tested by: Signature & Date:

1r-n ENG.

1y-n

1b-n

Average Res /Ph @ Amb. Temp () Witnessed by: Signature & Date:

* Res/ph @ 75 C () ENG.

Factory resistanc e @ 75˚c

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-----

(235 + 75) * Res / Ph @ 75  C. = Avg. Res / Ph @ Amb. Temp. X -------------------------(235 + Avg Oil Temp.)

4.3 TV winding Tap no.

Winding resistance ( m) @ ambient Average Res /ph @ temp. amb. Temp 2r-n 2y-n 2b-n (m)

* Res/ph Factory resistanc @ 75  C e (m) @ 75˚C

----(235 + 75) * Res / Ph @ 75  C. = Avg. Res / Ph @ Amb. Temp. X -------------------------(235 + Avg Oil Temp.) 5. MAGNETIZING CURRENT TEST (NO LOAD CURRENT TEST) Instrument: Condition: (1) Three phase voltage applied on HV side by keeping LV side open. (2) Current measurement carried at HV terminals. Tap No.

Measured voltage at HV side R-Y

Y-B

B-R

Average volt

Measured current at HV side (mA) Averag IR IY IB e Current

N Average current rated tap voltage I0 % = --------------------- × ----------------------- × Average voltage rated tap current Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

ENG.

100

I0 %

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I0 Criteria: < 0.5 %

Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

ENG.

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6. MAGNETIC BALANCE TEST Tap : ----L Measured Voltage ( V ) REF R–N Y–N B–N

R–N

HV Y- N

B–N

1r – n

LV 1y - n

1b – n

LV 1y - n

1b – n

LV 1y - n

1b – n

Tap : N Measured Voltage ( V ) REF R–N Y–N B–N

R–N

HV Y- N

R–N

HV Y- N

B–N

1r – n

Tap : ---- R Measured Voltage ( V ) REF R–N Y–N B–N

B–N

1r – n

Note: 1. When applying voltage between R-N => Y-N + B-N 2. When applying voltage between Y-N => R-N +B-N 3. When applying voltage between B-N => R-N +Y-N

Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

ENG.

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7. VECTOR GROUP TEST HV termination designation – R, Y, B, N LV termination designation – 1r, 1y, 1b, 1n Condition:  Three phase Voltage applied on HV side.  Connect R and 1r.  Tap changer kept at Tap position (Normal Tap)  Voltage measurement Measured voltages following R ×

R Y B N r y b n

Proof:

Y × ×

B × × ×

N × × × ×

r × × × × ×

y × × × × × ×

b × × × × × × ×

Vector Group is

Result: Equations to be satisfied for YNyn0 vector group as an example are 1. 2. 3. 4. 5. 6.

R-1b = Y-1y Y-1b > B-1b B-1y = Y-1b Y-1y > R-1y Y-1b > Y-1y R-1y = R-1b

=> => => => => =>

R,1r 1b

N

B

Tested by: Signature & Date:

ENG.

1n 1y

Witnessed by: Signature & Date:

ENG.

Y

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8. SINGLE PHASE IMPEDANCE MEASUREMENT 8.1

Condition:

1. Apply voltage between R and Y. 2. Short all low voltage side of transformer. Tap

Tested by: Signature & Date:

Measured voltage

ENG.

Measured current

Factory resistance

Witnessed by: Signature & Date:

Measured resistance

ENG.

% Error

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8.2

Condition:

1. Apply voltage between Y and B. 2. Short all phases of low voltage side of transformer. Tap

Measured voltage

Measured current

Factory resistance

Measured resistance

8.3 Tested by: Signature & Date:

ENG.

% Error

Condition: Witnessed by: Signature & Date:

ENG.

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1. Apply voltage between B and R. 2. Short all phases of low voltage side of transformer. TAP

Measured voltage

Measured current

Factory resistance

Measured Resistance

% Error

9. SHORT CIRCUIT TEST (Percentage Impedance Measurement) Ambient Temperature

:

C

9.1 Tap ---- L 

Connect 3-phase supply to HV side and short LV side winding. Voltage (V)

R-Y

Current (A)

IR

* Average voltage * Average current Tested by: Signature & Date:

ENG.

Y-B

B-R

IY

IB

= =

volt Amp Witnessed by: Signature & Date:

ENG.

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* Rated current * Frequency * Rated voltage % Impedance =

= = =

Sheet: 14 of 27 Substation No :

Amp 60 HZ volts

(HV side Rated current / HV side Rated voltage) × (Average voltage / Average current) × 100 =

Note: Factory test = Error = % Tolerance = +10 %

%

9.2 Tap N 

Connect 3-phase supply to HV side and short LV side winding. Voltage (V)

Current (A)

R-Y

% Impedance =

Signature & Date:

IY

IB

Volt = = = =

Amp Amp 60 HZ Volts

(HV side Rated current / HV side Rated voltage) × (Average voltage / Average current) × 100 =

Note: Factory test = Error = Tolerance =

ENG.

B-R

IR

* Average voltage = * Average current * Rated current * Frequency * Rated voltage

Tested by:

Y-B

% % +10%

Witnessed by: Signature & Date:

ENG.

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9.3 Tap --- R 

Connect 3-phase supply to HV side and short LV side winding. Voltage (V)

R-Y

Current (A)

IR

* * * * *

Average voltage Average current Rated current Frequency Rated voltage

% Impedance =

Y-B

B-R

IY

IB

= = = = 60 =

volt Amp Amp HZ volts

(HV side Rated current / HV side Rated voltage) × (Average voltage / Average current) × 100 =

Note: Factory test Error Tolerance

= =

% % +10 %

=

10. ZERO SEQUENCE IMPEDANCE MEASUREMENT 10.1 



 Tap

Rated voltag e

Condition:1 Shorted R , Y ,B On HV Side Single phase Voltage applied on HV side between shorted terminals R-Y-B and neutral N. Keep LV side open and TW side short. Measure the Voltage & Current on HV side Rated Curren t

Measure d V0

Z0

Calculate d Z%

Factory Z%

I0

---L Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

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% error

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N ---R 10.2 

 

Tap

Condition:2 Shorted R , Y ,B On HV Side Single phase Voltage applied on HV side between shorted terminals R-Y-B and neutral N. Keep LV and TW side short. Measure the Voltage & Current on HV side

Rated voltag e

Rated Curren t

Measured V0 I0

Z0

Calculate d Z%

Factor y Z%

% error

---L N ---R Calculation 3 V0 / I0 % Z = ---------------------------- × 100 (VRATED / √3) / I RATED 11. CAPACITANCE & TAN DELTA OF WINDING: Oil temperature : c Correction factor : (To convert % Dissipation Factor to 20 C, Divide the measured % Dissipation Factor value with Correction Factor) Test No. 1 2 3 4 5 6 7 8 Tested by: Signature & Date:

Insulatio n Tested CHG+CH L CHG CHL CLG+CLT CLG CLT CTG+CH T CTG ENG.

Test Mode

Test connection Ga Eng Gnd r L

Test KV

GST

H

T

10

GST UST GST GST UST

H H L L L

L,T

10 10 10 10 10

T

H T,H

GST

T

H

L

5

GST

T

H,L

5

ma Cap (ΡF)

Witnessed by: Signature & Date:

ENG.

P.F %

P.F % Watts At 20 ̊ C

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9

CHT

UST

Sheet: 17 of 27 Substation No :

T

5

H = high voltage 110 kV winding grounded L = low voltage 15 kV winding winding Criteria: P.F% AT 20  C < 0.5

G = body of Transformer T = 6.6KV tertiary

12. TRANSFORMER TURNS RATIO (HV- LV) Transformer name plate data Tap HV no.

LV

Measured ratio R-N/1r-n

Calc. Rati Rati o o

Dev . (%)

I exc. (mA)

Measured ratio Y-N/1y-n I Dev Rati exc. . o (%) (mA )

Criteria Acceptable Tolerance for Ratio Deviation is + 0.5% Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

ENG.

Measured ratio B-N/1b-n I Dev Rati exc. . o (%) (mA )

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Tested by: Signature & Date:

Drawing ref.: Contract no.:

ENG.

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Witnessed by: Signature & Date:

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13. CALIBRATION OF OIL AND WINDING TEMPERATURE SENSORS Reference Temp. Starting Temp 40 60 80 100 120 140

Oil Temp Indicator

HV winding temp. indicator

LV winding temp. indicator

Criteria: ± 3 14. WINDING TEMPERATURE CALIBRATION BY SECONDARY CURRENT INJECTION: High voltage winding temperature indicator: Ct ratio : Full load current: A Current injection: A Reading Time (min.) Temp. Reading 0 5 10 15 20 25 30 35 40 Oil Temp. At start (A) Oil Temp. At end (B) Winding Temp. Before current injection (C) Winding Temp. After 45 mins (D) Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

˚C ˚C ˚C ˚C ENG.

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Simulated temp. Rise measured: [(D-C)-(B-A)] Low voltage winding temperature indicator: Ct ratio : Full load current : A Current injection : A

˚C

Reading Temp. Reading(˚c Time (min.) ) 0 5 10 15 20 25 30 35 40 45 Oil Temp. at start (A) Oil Temp. at end (B) Winding Temp. Before current injection (C) Winding Temp. After 45 mins (D) Simulated Temp. Rise Measured: [(D-C)-(B-A)]

Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

˚C ˚C ˚C ˚C ˚C

ENG.

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15. OIL DIELECTRIC STRENGTH: Electrode form : Distance : Minimum strength Sample location

IEC 156 1995 2.5 mm : 50 KV

Test #

Break down voltage (KV)

Average Break down Voltage (KV)

Main tank Top

Main tank Bottom

OLTC

Conservator

Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

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16. TESTING OF FANS: Group # 1 Fan no.

IR with 1000 starting current (A) V ( GΩ ) IR IY IB

running current (A) IR

IY

Directio n

IB

Total current consumption by group # 1 cooling fans IR

STARTING IY

IB

RUNNING IY

IR

IB

Group # 1 As per approved drawing 1. Verified group # 1 starts at 2. Verified group # 1 stops at

c c

Group # 2 Fan no.

Ir with 1000 V ( GΩ )

Starting current(A) IR IY IB

Running current (A) IR

IY

IB

Total current consumption by group # 2 cooling fans Tested by: Signature & Date:

ENG.

Witnessed by: Signature & Date:

ENG.

Directio n

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Starting current (A) IR IY IB

Running current (A) IR IY IB

Group # 2 1. Verified group # 2 starts at 2. Verified group # 2 stops at

C C

17. ON LOAD TAP CHANGER: N o 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Tested by: Signature & Date:

Explanation of event

Results

MCB of tap changer motor(Q1) AC socket(X19) & mcb(F25) Heater & thermostat & mcb(F16) Lighting(E1) & door switch(S10) Mechanical operation check Mechanical upper limit lock Mechanical lower limit lock Electrical opertion Upper Electrical limit lock Lower Counter operation check Local operation check Stop and rotation pointer Motor starting / running current Motor handle interlock Local / remote check(local operation switching) Motor drive & OLTC tap # comparison Sound during operation Alarm signals for control room Emergency stop switch Tap position indicator Tap changer in progress Tap changer faulty Raise Tap changer from remote Lower ENG.

Witnessed by: Signature & Date:

ENG.

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24 OLTC local 25 OLTC remote Raise Lower

26 Tap position 27 Tap changer incomplete

18. MCB TEST AT MARSHALLING KIOSK: 18.1 Item 1 2 3 4 5

Mechanical Checks & Physical Inspection:

Description Inspect for physical damage / defects Verify connection as per approved drawings Verify tightness of all connections Check ferrules Check apparatus list

18.2

Checked

Electrical Tests:

Thermal over Load Test: MCB No.

Tested by: Signature & Date:

Make

ENG.

Type

Settin g (A.)

Injected Current (A.)

Measured tripping time (s)

Witnessed by: Signature & Date:

ENG.

criteria (sec.)

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19. FUNCTION CHECK OF FAN PANEL ACCESSORIES: Item 1 2 3

19

Functions Main power supply 3ph AC 380/220V,60hz Backup power supply 3 ph AC 380/220V,60hz Voltage monitors(under voltage relays)27-1,27-2,check 27X1, 27X2 operating with