instrument xmers - testing
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PTHV-IT, INABB
A/D conversion
Computer
Rb
METER
O/P
CVT CT
Instrument
TransformersProduct Training
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P T
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2
CT – Routine Tests
Tests as per IEC: 60044-1 and IS: 2705
Verification of Terminal Markings and Polarity
Power Frequency Withstand Test on Primary andSecondary
Partial Discharge Measurement
Inter-turn Over Voltage Test
Determination of Errors
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Tests as per IEC: 60044-1 and IS: 2705
Short Time Current Test
Temperature Rise Test
Lightning Impulse Test
Switching Impulse Test
Radio Interference Voltage Test
Determination of Errors
Facilities for conducting all Type Tests on CTs except ShortTime current Test (ERDA / CPRI) and Seismic test (IITChennai / University of Roorkee) are available at our works.
CT – Type Tests
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Tests as per IEC: 60044-1/ IS: 2705
Chopped Lightning Impulse Test
Measurement of Capacitance and Dielectric DissipationFactor
Multiple Chopped Impulse Test on Primary
Special tests as prescribed in CIGRE have also beenconducted
CT – Special Tests
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Figure: 1 Simple vector diagram for loss factor test
Test Setup:
V = Applied voltage
IT = Total current
IR = Resistive current
IC = Capacitive current
Dissipation factor = tangent δδδδ= IR/IC
Power factor = cosine θθθθ= IR/IT
H. V. Line
C4
R3
Test Object
R4
b
a
d
c
RX
CX
C1
D
D=Zero balance indicatorC1=Standard CapacitanceC4=Variable CapacitanceR3= Variable Resistance
Figure:2- Simple Schering bridge
Figure: 3- Test Set up for Capacitance & tandelta test
650V/750kV,
0-250V
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In case of cores it may bethe artificial primary
Figure: 1- Ratio and Phase angle measurement setup
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1.6.1 Test Setup
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1 0
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TEST CERTIFICATE FOR CURRENT TRANSFORMER
Test Report No. CT/2008374 Date : 30/06/2008
CLIENT
CLIENT'S ORDER NO/LOA NO : 3191054331 DTD. 12-01-2008
WORK ORDER NO. 4200018667/30
DATE OF TESTING 30/06/2008
SPECIFICATION OF CURRENT TRANSFORMER
Sr. Nos. : 1108163
QTY. 01 No.
TYPE IMB 145
HIGHEST SYSTEM VOLTAGE 145 kV
RATED INSULATION LEVEL 145/275/650 kVRATED SHORT TIME THERMAL CURRENT: 40 kA, 3 Sec.
RATED PRIMARY NORMAL CURRENT: 1200 A
RATED CONTINUOUS THERMAL CURRENT: RATED PRI X 1.2
FREQUENCY 50 HZ
CORE :1 CORE : 2 & 3 CORE : 4
RATIO (AMP) 1200/1 1200/1 1200/1
BURDEN (VA) 50 -- 20
CLASS 0.2 PS 5P
ISF < 10 -- --
ALF -- -- 20
Vk (VOLTS) -- > 500 --
Io (mA) -- < 100 AT VK --RCT(OHMS) -- < 5 --
1.1 VERIFICATION OF TERMINAL MARKING & POLARITY TEST O.K. AS PER REF. STANDARDS
275 kV FOR 1 MINUTE : O.K.
5 kV FOR 1 MINUTE : O.K.
For ABB Ltd.
VIMAL PANDYA/S.R.SHAH
PTHV- IT-TESTING
STANDARD FOLLOWED : IS 2705/IEC 60044-1
THIS IS TO CERTIFY THAT THE ABOVE CURRENT TRANSFORMERS HAVE PASSED THE ROUTINE TESTS AS
PER IEC: 60044-1 & IS : 2705
1.3 PARTIAL DISCHARGE MEASUREMENT
1.4 POWER-FREQUENCY VOLTAGE WITHSTAND TEST ONSECONDARY WINDINGS ( All windings were tested individually )
1.5 INTER-TURN OVER VOLTAGE TEST O.K. AS PER REF. STANDARDS
1.2 POWER-FREQUENCY VOLTAGE WITHSTAND TEST ON
PRIMARY WINDING
5 pC AT 1.2 UM/ √3 & 10 pC AT UM
1.7 SEALING TEST (VISUAL) NO LEAKAGE OBSERVED
1.6 TURNS RATIO ERROR ( As per formula given in standard ) O.K. AS PER REF. STANDARDS
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Test Report No. CT/2008374 Limits
CT Sr.No. 1108163
2.0 Current error and phase angle error & TRE measurement PS cores
Ratio = 1200/1
Core Ratio Ph.Angle Ratio Ph.Angle TRE Rct (Ohm) Rct at 75°C
No. Error ( % ) Error(min.) Error ( % ) Error(min.) (%) at 32°C (Ohm) Ratio
AT 0 VA AT 10 VA (UPF) 32
2 0.00 0.20 -0.02 1.10 -0.015 6.30 7.317 1200/1 12
3 0.00 0.20 -0.02 0.80 -0.015 6.40 7.433 1200/1 12
2.0 Current error and phase angle error measurement for Protection core.
Core Primary Ratio Ph.Angle Ratio Ph.Angle Rct (Ohm) Rct at 75°C
No. current Error ( % ) Error(min.) Error ( % ) Error(min.) at 32°C (Ohm) Ratio
AT 50 VA 0.8 lag AT 12.5 VA 0.8 lag
1 60 -0.20 2.30 -0.06 1.00 4.40 5.807 800/1
1 240 -0.12 -0.10 -0.04 0.00
1 1200 -0.05 -1.40 -0.02 -0.50
1 1440 -0.06 -1.00 -0.02 -0.50
AT 50 VA 0.8 lag -- --
4 1200 -0.05 0.50 -- -- 9.00 10.452 1200/1
3.0 Knee point voltage ,Exciting current,composite error Test
Core Sec.Wdg. c t at 75°C Voltage Exc.current Remarks limit exc .
No. Terminals (ohm) ( Volts) mA Curr.(mA)
2 2S1-2S2 500 8.0 Vk> 500 <100 100
577 9.0
635 10.0
3 3S1-3S2 500 8.0 Vk> 500 <100 100
577 9.0
635 10.0
ISF Burden Sec.current Spec.ISF
1 1S1-1S2 5.807 113.0 > 1.0 2.025 50 1 < 10
Amp. C.E.% Burden Sec.current Spec.A.L.F.
4 4S1-4S2 1182 0.0110 0.055 50 1 20
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The values of knee pointvoltage and excitingcurrent shall be asguaranteed.
With the pri. open, the CT sec. will be excited ata voltage meant for measuring the excitingcurrent and the exciting current shall be lessthan the specified limit.
Then the sec. will be excited at rated Vk andcurrent is to be measured. This voltage will beincreased by 10% and again the current is to bemeasured. Increment in current should not be50% of the earlier value.
IS:2705 (PartIV) Cl. 6.1
11.0Measurementof Knee pointVoltage andexciting current
The Turns ratio error shallbe within ± 0.25 % or withinlimits specified in IS : 2705.
The error will be measured at 0VA and at 10 VAburden, having a power factor of 0.8 or unity.Turns ratio error will be calculated by thefollowing formula :
TRE=y[(A+R)/(B-A)]-x[1+(A+R)/(B-A)]
y = current error at 10 VA
A =0
R = Resistance of secondary winding
B = 10
x = current error at 0 burden
IS:2705 (Part-IV) Cl. 6.3
10.Turns Ratiotests forProtectionCore Cl. PS
++)+(+*,1+1
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1 9
Rate
d
Volta
ge
(kV
rms)
Highest
System
Voltage
(kV rms)
One min. PF
withstand
Test Voltage
(kV rms)
PD Prestress
Voltage for
one min.
(IEC:60044-
1)
(kV rms)
PD
Measuring
Voltage for
30 sec ( for
two voltage
levels)
(kV rms)
PD Levels
in pC
CT Primary
Contact
Resistance
Capacitance Value in pF
66 72.5 140 11250
72.5
< 5
< 10
950 ± 15 %, (N-100),Alu
1500 ± 15% N, Cu,Dia
68/42
110 123 230 18485
123
< 5
< 10
132 145 275 220
100.5
145< 5
< 10
850 ± 15% N, Alu Sp.
1025 ± 15% N,Alu
1100 ± 15%N+200,Cu
1165 ± 15%N+200,Alu
1510 ± 15% N,Alu,Dia68/42
1465 ± 15% N,Cu,Dia 68/42
220 245 460 368
170
245
< 5
< 10
1110 ± 15% N ,Cu
1135 ± 15% N ,Alu
1225 ± 15% N+200 ,Cu
1250 ± 15% N+200 Alu
Pl refer Table
1 or
Annexure - 1
of instruction
1HYT600070
1175 ± 15 % for IMB 420
1250 ± 15 % for IMB 420Oval Conductor CT400 420 630 504
291
420291
420
< 5
< 10< 5
< 10125
maximum
700 ± 10% for TMBR l 420
CT
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2 0
CVT – Construction – EMU
HV Choke
PT
Bottom Tank
F R C i
r c u i t Resistor
Capacitor
FR Choke
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2 1
Step Down PT
HV Choke
C1
C2
V2
V1
Vs
FR CktResistor
Spark Gap
Sealed UnitProtects the EMU
from overvoltages
CVT - Schematic
I
mp
FR CktCharacteristic
Freq50
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WITNESS TEST REPORT FOR CVT
INSPECTION CALL NO:-
CLIENT : POWERGRID CORPORATION OF INDIA LTD.
WORKS ORDER NO. : 4200035285/10CLIENT ORDER NO. : ----
SUBSTATION : MAHARANIBAUG GIS
DATE OF TESTING : 29/06/2008
SPECIFICATIONS
Type : WS420N2
Rated Primary Voltage : 400/ √3 kVHighest System Voltage : 420 kVNominal Capacitance : 4400 pF + 10 % & - 5 %
Rated Insulation Level : 420/630/1425 kV Frequency : 50 HzSerial no. : 4208075Qty : 01 Nos.
No. of Secondaries : 3
Standards Applicable : IEC 60186, IS 3156
Rated Sec. Voltage
(volts)
Terminal marking Rated Burden (VA) Accuracy
Class
110 / √ 3 1a-1n 50 3P
110 / √ 3 2a-2n 50 3P110 / √ 3 3a-3n 50 0.2
100 0.2SIMULTANEOUS
BURDENS 150 3P
1.0 All the Capacitor Voltage Transformers have passed the following Routine tests.
1.1 Induced over voltage test on P.T. at 46 kV,150 Hz for 1 min : O.K.
1.2 Induced voltage test on choke at 10 kV, 150 Hz for 1 min : O.K.1.3 Voltage withstand test on secondary winding at 3 kV, 50 Hz for 1 min : O.K.
1.4 Verification of terminal marking & Polarity test : O.K.1.5 Sealing test : No leakage found at various sealing joints.
1.6 HV Test on earth terminal of CVD / HF Bushing at 10 kV for 1 min. : O.K.
For ABB Ltd. Witnessed by
VIMAL PANDYA/S.R.SHAH AJAY DINKAR
PTHV- IT-TESTING PGCIL , VADODARA
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2. Capacitance and Tan delta Measurement Test :
Sr. No. Capacitance(pF)
Tan delta(%)
H.V. withstandtest at 220.5 kV
for 1min.
Capacitance(pF)
Tan delta(%)
CVT SR. NO. 4208075
BEFORE H.V AFTER H.V
Unit 1- 73.0kV80.8 kV88.9 Kv
131561315613156
0.0770.0770.077
OK 131551315513155
0.0760.0760.077
Unit 2-73.0 kV80.8 kV88.9 Kv
131541315413154
0.0780.0780.078
OK 131541315413154
0.0770.0770.077
Unit 3-73.0 kV80.8 kV88.9 kV
131111311113111
0.0790.0790.079
OK 131101311013110
0.0780.0780.078
3.0 Partial Discharge TestPre-stress voltage = 0.8*630*1/3*1.05= 176.4kV for 60 sec.Measuring voltage MV-1 = Um*1/3*1.05=147 kV for 30 sec.
Measuring voltage MV-2 = 1.2*Um/ √ 3*1/3*1.05=102.0 kV for 30 sec.
Sr. No. Voltage
Level
Unit-1 Unit-2 Unit-3 Limit in Pc
M.V. -1 1 pC 1 pC 1 pC ≤ 104208075
M.V. -2 1 pC 1 pC 1 Pc ≤ 5
4.0 Accuracy measurement as a function of voltage and burden:
CVT SR. NO. 4208075
Voltage(%)
WindingUnderTest
Burden VA 0.8 lag VoltageError
(%)
PhaseAngle error(min.)
Frequency(Hz )
Wdg.1 Wdg.2 Wdg.3100 1a – 1n 12.5 0 0 0.56 0.9 50.00
100 1a – 1n 50 0 0 0.50 0.9 50.00100 1a – 1n 50 50 50 0.38 6.9 50.00
100 2a – 2n 0 12.5 0 0.46 6.9 50.00
100 2a – 2n 0 50 0 0.50 6.9 50.00100 2a – 2n 50 50 50 0.36 6.9 50.00
100 3a – 3n 0 0 12.5 0.11 6.9 50.00
100 3a – 3n 0 0 50 -0.02 6.9 50.00
100 3a – 3n 12.5 12.5 50 -0.05 4.9 50.00
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~
Care for CTs and CVTs
Incase of saturation of CT core during fault, they arerequired to be Demagnetized in order to let them performaccurately after the fault is cleared. The following method
may be adopted
Gradually excite the core upto its Output Voltage andreduce it to zero.
Repeat it 3 – 4 times. This will make the core free ofResidual flux and it is now ready to function as desired.
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The change in capacitance value
between before & after HV test shall
not be more than that caused by
failure of 1/3rd element of the
capacitor coil. Pl refer Annexure –II
for detailed values of capacitance.
Simillarly the change in Tan Delta
value shall not be more than 0.001(in
abs. value).+
Same as mentioned in 2 aboveIEC:358
Cl. 7 & 8/ IS:9348
Cl. 8.3
5. Capacitance &Tan Delta after HV
test
No puncture or flash over should occur.4/10 kV will be applied between theearth terminal ( Outdoor HF Bushing )and the tank and will be maintainedfor 1 minute. (4 kV in case ofenclosed CVT Terminal)
IEC:358 Cl. 10/ IS:9348 Cl. 8.54. Voltagewithstand test onearth terminal ofCVD
++)+(+*,1+1
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Sr No Permissible changein values of
Capacitance (
Before And After
HV Test )
400kV (Total 3 capacitorunits) 245kV( Total 2
capacitor
units)
145kV ( onecapacitor unit) 66kV( one capacitor
unit)
1 Rated Capacitanceof CVT
4400pF 8800pF 6600pF 4400pF 5500pF 4400pF
2 Permissible increase
in Capacitance**
124pF 78pF* 165pF 70pF 34pF 37pF
* A failure inside the capacitor element or coil will increase the capacitance of the capacitor unit.Value for complete CVT
** A failure inside the capacitor element or coil will increase the capacitance of the capacitor unit.
Value for individual unit of CVT.
Note: 1
In case of 220 and 400 kV CVTs, if the test is made on one capacitor stack, then the applied voltage per stack will be calculated as
Voltage to be applied on stack = 1.05 x Voltage to be applied per unit x (Rated voltage of stack/Rated voltage of unit)
7/28/2019 Instrument Xmers - TESTING
http://slidepdf.com/reader/full/instrument-xmers-testing 30/30
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