precommissioning test for 220kv substation dajay

7/29/2019 Precommissioning Test for 220kv Substation Dajay

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Tests carried out during the pre-commissioning test.

Test date: 28/01/2013 - 03/02/2013

Followings are present during the test:

1. Voltech, office based in Tamil Nadu, India.

2. CGL, office based in Kolkata.

3. BPCL, office based in Tsirang.

4. KECL, Site office based in Tsirang.

Knee point voltage test: It is a minimum voltage test performed using the injection of voltage (for eg.

HVN core) for PS- class, 1s1-1s2. While conducting the test, the tap position 1s1 & 1s2 is connected

from the step up transformer applying the minimum of 1000V injection so as to get the output current

of 150mA maximum. The test is further carried out with the application of 10% on the 1000Vapplication so as to get maximum current flowing across the secondary core terminals. However, the

secondary CT current at the minimum knee point voltage is comparably less than that of the

designated current of 150mA. If voltage exceeds minimum knee point voltage, the core goes into

saturation no matter what the excitation current is being implied. At the point when the CT core

reaches saturation point, Ixe increase by 50% of the normal current where it leads to detoriation in CT

core and severe damages.

Instruments used during the test: Variac (auto transformer), 5KV step-up transformer, multimeter (

measures knee point voltage) & leakage current tester (tongue)- measures current corresponding to

knee point voltage.

Ratio test: Ratio test is conducted for both protection and metering class which covers every core

terminals of U, V & W phases. The test is so conducted, where the two tap position of HVN (eg.

1N1S1 & 1N1S2, 1N2S1 & 1N2S2) will be shorted. The current will be noted at the short guard wire

with the gradual application of primary injection current from a loading transformer, where the

conductor from the loading transformer will be passed through the core. Both the primary injection

current in the primary cable and shorted core terminal wire measures current using leakage tester. The

gradual increase in primary current up to300A should gives out 1A across the shorted secondary

terminals.

Instrument used: Variac (auto transformer), Loading transformer, Leakage current tester- 2nos.

Winding resistance test: Winding resistance test is conducted for only PS class core, using resistance

tester. The minimum of 1.5ohms should be obtained at the end of test. Tap to Tap (in a single core)- o

ohm, Tap to tap (in a different core)- G ohm range, single core to earth- G ohm value should be

shown in a galvanometer for a insulation resistance measurement check.

Tan Delta test: Tan Delta test is so performed by the injection of voltage from the control transformer

with the variation of voltage in three different ranges (i.e 2kV to 10kV), three readings are performed.

The high voltage input is connected at the top of a bushing and another wire is tapped from the R-

phase control unit to the tan delta point. With the application of voltage up to 10kV, the input current

should be at the range of 100 of mA, which decreases with the rise in voltage and the capacitance is

read in pico farad range (usually 350 to 500 PF range in case of 220kV transformer bushing). The tan


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delta, dissipation should be maintained within a range of 0.005 range to assure specified value which

indicates that the insulation of a bushing is perfect. Value above 0.005 is unacceptable. The test so

carried out is only UST (un-ground specimen test). GST (grounded specimen test) & GSTG(grounded

specimen test with guard) will be performed after creation of transformer vacuum, oil infiltration and

filling of oil. This latter two test shall be carried out after performing the above action before final

commissioning.

UST test is carried out only for bushings whereas GST & GSTG tests are carried out for windings of

transformer.

Polarization Index (PI): PI is the special test carried out to note resistance of transformer bushing on

HV side after filling up insulating oil in main transformer tank and following an immersion of

bushing into insulating transformer oil. The test is thus performed setting a range of time interval from

1min to 10 min, automatically noting the value of bushing resistance in mega ohm. PI value is a ratio

of resistance measured in 1min to 10 min where the value should be proportional to or more than 1.5.

Higher the PI value, indicated high insulating oil and bushing dielectric strength.

The test is so performed after shorting all three HV terminal bushing with HVN bushing using meger

testing instrument. Positive terminal of megger is connected to the shorted bushing at HVN terminal

and negative terminal is earthed.

The above mentioned test details are all conducted for the transformer- T10024/1.

Test date- 20/02/2013 - 22/02/2013

Polarity test (CT): Polarity test is so performed to know the polarity of current transformer. The CT

terminal P1 & P2 is connected with a probe. At the other spectrum, a galvanometer is connected

across each and every tap position of individual core to see a correct deflection of galvanometertowards right. ( i.e 1S1-1S2, 1S1-1S3.....5S1-5S4). A 9V Pb battery is energized to the CT primary

terminal P1 & P2 to read a deflection of galvanometer who's terminal is connected to respective tap

position as stated above. If a galvanometer pointer deflects towards the right, the equipment polarity is

correct and if deflected towards left equipment polarity is incorrect.

IR test (CT): Insulation resistance (IR) test is so conducted to know the dielectric withstanding

capacity of insulation of CT winding. The test is performed in different stages viz. Primary terminal

(P1 or P2) to earth with 5kV DC meger input, Primary terminal (P1 or P2) to individual core

(1S1....1S5) with 500V DC meger input, Core (1S1.....) to core (2S1.....) injecting 500V DC meger

input. The IR value should be in the range of Giga Ohm, where primary to earth meger value is higher

as compared to remaining connection as mentioned above.

CT winding resistance test, Knee point voltage test and Ratio test is similar to the test as conducted in

transformer CT for primary, secondary and Neutral CT inside respective turrets.

The above test are conducted for ICT-1 CT.

Test Date- 23/02/2013

1. Megger test- Meger test is carried out for the transformer HV-Earth, LV-Earth & HV-LV. The test

is conducted with the help of 5kV rated meger. The above test result is obtained in the range of 37G

and above.


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2. Vector Group test- Vector group test is so conducted for the transformer having a vector group of

Yyn0. Vector group test is conducted with the help of3 4 wire AC supply which is connected to a 4

pole MCB, which is then connected to a HV bushings U, V, W. The U point terminals of the MCB is

then connected to another U point terminal bushing of LV along with V & W. The voltages are

measured so with respect to the terminals between each phases where the summation of two terminal

result shall correspond to the terminal of the earlier measured. The test is conducted with the help of

multimeter.

3 Phase supply connected

on HV side bushings

U1-N2= U1-N1 + U1-N2

W1-W2= V1+ V2

4P MCB(for HV)

R

Y

B

N

Transformer-10MVA

U1 V1 W1 HVN

U2 V2 W2 LVN

4P MCB(for LV)

R

Y

B

N

U1

N1

W1 V1

N2

W2V2

U2


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SF6 Circuit Breaker-

1. Difference between touch contact and fully closed contact- Wipe (in mm) (83-51)

2. Difference between fully opened contact and fully closed contact- Pole stroke (in mm) (280-51)

The test is performed along with the personnel specified from the CGL, Nashik, India. During the

period, carried out slow closing and opening operation of breaker for all the breakers and thus

conclusively obtained the above results. The above results correspond to the stipulated test

requirement for the breakers generally. Hence the above test satisfied.

24/02/2012

Current Transformer

Conducted tests for the fulfilment of CT application regarding Dagachhu incomer line bay. The test

are conducted similar to the earlier test conducted for ICT-1 bay CT. All the tests are passed and

concluded satisfactory.

Transformer-10MVA

Followed by the voltage ratio test for the 10MVA transformer. Test is so conducted starting from the

OLTC tap no. 1 gradually increasing to tap no.17

3-phase supply connected on HV side.

The above test should witnessed as follows. While testing on tap no. 1, the voltage readings are

conducted on each and every phase terminals across for both HV and LV side i.e R-B, B-Y, Y-R, R-

N, Y-N & B-N by giving supply only in HV side regardless of LV side to satisfy the test. The voltage

should show gradual increasing trend while increasing the tap position practically but the test result

4P MCB(for HV)

R

YB

N

Transformer-10MVA

U1 V1 W1 HVN

Transformer Bushings

positioned on HV & LV

U2 V2 W2 LVN

4P MCB(for LV)

R

Y

B

N


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was found unsatisfactory. It was agreed to carry out the test the next day to attain correct result. The

test is further corrected whether the values obtained are correct or not by calculating from the standard

value, for the rest of the tap position readings.

HV-220000/ LV-66000= 3.33 (constant)

Polarization index test- The test is conducted for the transformer ICT-1 after complete oil filtration

and full filling of insulating oil in to transformer with the acquired BDV of 71kV.

1minute- 31.7ohm

10min- 115ohm

PI value is calculated as 2.9

Date- 25/02/2013

SF6 CB- 1. Checked continuity test for inter-pole CB. The continuity is done for the control panellinking in between R, Y & B phase CB pole and Marshalling box. The test is carried out using digital

multimeter.

2. Carried out filling of SF6 gas for CB up to the ceiling requirement of normally 7.2 Kgf/mm.

During the filling of gas, it is checked for gas locked out and gas alarm pressure as noted below.

SF6 gas pressure Low Nominal SF6 gas pressure

Gas locked out (GL) Gas alarm (GA)

Gas alarm (GA) Gas locked out (GL)

For R-phase- During the zero SF6 gas, the GL contact will be NO and GA contact will be NC. At the

fully filled SF6 gas level, GL contact will be NC and GA contact shall be NO. Continuity is sound

during NC contact which shall be checked in R-phase TB- XR1.

Date- 26/02/2012

Magnetization balance test and magnetizing current test. (f or ICT-1)

The magnetizing balance and current test procedure are different for star and delta connected

transformer. The test is conducted for star connected transformer, injecting supply on HV side and test

read, then inject supply on LV side then test read where tapping out single phase supply (for e.g. R-

phase) keeping other two phases open. Hence the voltage is measured across R-N, Y-N & B-N,

whereas Vrn= Vyn + Vbn. Magnetizing current is measured using clamp meter on R-phase,

approximately 1mA.

The test is conducted for delta connected transformer, injecting supply on HV side and test read, then

injecting supply on LV side and test read. The R-phase is connected to R-phase MCB and Y-phase is

connected to MCB neutral, remaining B-phase is kept open. The voltage is measured across R-Y, Y-B& R-B whereas the Vry= Vyb + Vrb. Magnetizing current is measured in R-phase.


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Y(open)

B(open)

Vrn= Vyn + Vbn (hence the same test is conducted serially for other two opened phases and

then the same test is adopted for LV side also)

B-phase opened

Vry= Vrb + Vyb (The same test is serially conducted for the remaining two opened phases

and is adopted for LV side.

SF6 Circuit Breaker

1. Conducted CB closing and opening timing using CB operational analyzer kit giving DC

supply. The closing time should be not more than 5ms and opening time should be not more than 3.3

ms.

2. DCRM(Dynamic contact resistance measurement) test.

Conducted using DC battery kit and CB operational analyzer kit to check for contact

resistance check. It is just tested to see the condition of breaker analyzing through graph denoting

various parameters viz. closing coil current, tripping coil current, resistance and status of sharp shoot

of tripping coil and closing coil current. If it is found sharp shoot, the test is not passed till the graph is

normalized.

3. CRM(Contact resistance measurement) test.

The test measures the contact resistance during the time of arching operation. The contact

resistance should be normally 90 micro ohms and below, shall indicate the contact is proper.

04/03/2013

Relay test- Carried out various test for distance relay, Restricted earth fault relay, differential

over current relay. Simens relay uses Digsi manager software and PCM software for ABB relay.

Omicron software is used during the testing of relay and generation of fault for relay, where this

software is used along with omnicron kit which injects actuating quantities current and voltage tolearn about the correct operation and detecting of fault, time delay performed by relay.

4P MCB(for HV)

R

Y

B

N

Transformer-10MVA

U1 V1 W1 HVN

U1 V1 W1

4P MCB(for HV)

R

Y

B

N


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REF relay- Uses metro cells which is connected in parallel and rheostat in series, where metro

cells control and blocks the voltage and rheostat control and blocks the current. Thereby huge rush of

short circuit current and high voltage is limited for the safety of relay.

Distance relay- The relay operates based upon the ratio measurement (V/I) where the fault is

detected in protected section of line length based on measuring impedance. The protection zone isalso divided into four namely Zone-1, 2, 3 and reversed zone.

Zone-1: Operating time - 0sec. Zone-2: Operating time- 4 sec.

Zone-3: Operating time- 8 sec. Reverse zone: Operating time- 1 sec.

During the relay test, the fault is created by omicron kit through injection of current and voltage to see

the correct sensing and operating of relay on time for the specified protected distance. Fault and

operation of relay is displayed on the Resistance- reactance diagram for all four zones.

PUTT- permissible under reach transfer trip relay shall energise and actuate the relay coil for the

zone-1 operating time though the faults occur in zone-2.

Time setting for Directional over current relay. (for normal inverse 67/67N )

Time setting=[

Where; =0.02 (Constant)

I= Injected fault current

Ip= Setted current (0.2Amps)

0.15= Time multiplier setting(TMS)

Rated full load current(Ifl)=

For 300Amps-------CT sec. current= 1Amps

For 26.243Amps= 0.087 Amps (CT sec. current, considering cos=1)

0.087Amps for HV side of the transformer

4370mA for LV side of the transformer considering the same calculation for the above HV side.

Actual matching factor= 1.5

(0.087x0.2x1.5)= 1 coil pick up current

(0.087x0.2)= 3 coil pick up current

Transformer 87T relay operates both the function for HVRef + SEF protection along with

differential protection.

14/03/2013

Line Distance Protection 21.1(main 1) & 21.2 (main 2)


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SOTF(Switch on to fault) trip

The SOFT trip occurs only during the time of breaker switching, whereas its considered to be a

temporary fault and if the fault persist further the SOTF relay trips and SOTF LED glows.

Settings.... Voltage----------60%

Current---------20%

.:. 0.6x 63.51= 38.106V

0.2x 1= 0.2A

As the voltage drops and the current rises in respect to the above values, the relay gives trip command

to the breaker and breaker gets tripped.

Directional Earth fault---for normal inverse status

TMS (Tp) setted at 0.73sec

Ip setting= 0.2 A

Injecting current= 2x 0.2= 0.4A

The above two operational settings are for the distance relay. If the above fault occurs then

respectively the above LED blinks.

87T Relay

The LED glows w.r.t to the below operational settings.

V/F setting

V/F= 63.51/50= 1.27

Setting= 1.4

1.27x 1.4= 1.778

1.778= V/F

V=Fx 1.778= 50x 1.778= 88.9V

F= 63.51/1.778= 35.71Hz

The LED glows and relay trips if the above values varies so from the respective normal data. i.e

V=63.51V & F=50Hz

Harmonic inrush

15% for 2nd harmonic and 30% for 5th harmonics.

Where I2= Secondary current (LV)

I1= Secondary current (HV)


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I2/I1= 15% or less and 30% or less for the respective harmonics settings. Relay gets tripped if the

percentage gets exceed the above prescribed percentage and relay won't operate if the above

percentage is below the above the setted percentage.

Distance Protection relay

PUTT- Following the eventual line fault detected in zone-2, the substation-1 does trip in the zone-1

timing after receiving carrier signal from substation-2. Thereby in receiving the carrier from

substation-2, LED in relay 21 does not glow unless the carrier is transmitted from substation-1. Due to

the fact that the 20% of the line seen from S/s-1, the zone-1 protection falls for S/s-2, hence S/s-2

transmit carrier signal for instantaneous tripping. Hence the tripping time shall be reduced for the

cause of reliability of transmission line.

Power Swing- It is so-called temporary power surges due to over loading of power transformer and

rotor slip of generator due to fast reversing of rotor during the time of shutting down of a generator.

The relay sense that the power swing cause due to ramping of voltage (dV/dt) and ramping of current

(dI/dt)... which the summation of two ramping parameters gives rise to the ramping of impedance in

the transmission line. There by relay sense it to be a temporary fault in the power system and it will

just block the various setted zone, letting the power continuity through. Whereby the relay does not

get tripped operated.

Fuse Failure relay- The fuse failure relay gives annunciation and gets operated if the fuse inside CVT

fails in one of the secondary phase till control panel, though the CT secondary phases are correctly

operated the FFR gets operated. This is due to the drop in voltage or zero in voltage in one of the CVT

secondary phase. The FFR gets operated if the actuating quantity particularly in voltage is so droped

due to any wire/ fuse malfunction, though the line till bus is charged and in healthy status. The

jurisdiction of FFR is from CVT secondary till the control panel.

Directional Earth fault- The Directional earth fault relay do sense if any one or more of the phases in

transmission gets earth fault. During the course of earth fault, say R- phase its voltage will be zero or

too low which thereby it forms a path for neutral current. Hence the current will arise in R phase of aline and the remaining two Y & B phase will be having zero current. Thus due neutral current

flowing, the current in the relay gets imbalance and relay gets trip operated.

R-phase- 0V, Y-phase- 63.51V, B-phase- 63.51V

IL(1)- 2A IL(2)- 0A IL(3)- 0A

CVT Ratio test.

Voltage at the secondary core (1a-1n)=

80% 20%

S/s-2S/s-1


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=

(Let Primary injected voltage= 1100v)

CT Ratio test.

Current at the secondary core (1s1-1s2)=

Transformer Differential stability test.

DCRM Test for the SF6 Circuit Breaker.

During the DCRM test, following important factors are to be noted:

Contact travel timing. Contact travel distance. Dynamic and Static contact resistance. Pole mis-match.

Contact travel distance for 220kV CB is specified at 130mm with the tolerance of +2mm and -5mm is

accountable. Contact resistance should be below 100 is the acceptable limit as per the required

standard. Dynamic contact resistance is more important to trace the contact resistance as compared to

the static contact resistance, since dynamic resistance is measured at the first stable position of the

contact for close-open operation, whereas static resistance is measured always at the time of stableposition of the contact after the contact is fully closed. Therefore dynamic resistance will be always

more as compared to the static resistance.

Pole mis-match should be considered important for maintaining equal voltage induced and current

flowing through respective pole. Pole mis-match is considered 5ms or less for closing operation and

3.3ms or less for opening operation. While conducting DCRM, first the contact travel signature

should be conducted via single normal closing operation using transducer. The rated resistance of

transducer is 6k but while testing should be setted at 3k between L-E terminals. In practical three

terminals are connected L,N & E. The resistance between rest of the terminal shouldbe half of 3k.

Note that the, DCRM test shall be operated only for C-O operation whereas timing test shall be

operated for only O-C operation considering the importance of auto-reclose.

Direction of power flow

HVLV

Relay


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The picture below shows the connection in the DCRM kit for testing the CB contact operation.

Terminals to be connected on DCRM kit to the CB MB:

1. Source 1- (CLS & TRP 1)--- X1-118 (in the same TB link)2. Source 2- (CLS & TRP 2)--- X1-119 (in the same TB link)3. Closing coil (C-)--- X1-24 (shorting not required for three phases, is shorted internally)4. Tripping coil 1 (C-)--- X1-40 (short at X1-40-41-42 externally)5. Tripping coil 2 (C-)--- X1-52 (short at X1-52-53-54 externally)6. C+ & CH1 C+, T1+ & CH2 C+ are shorted for Trip 1.7. C+ & CH1 C+, T2+ & CH3 C+ are shorted for Trip 2.

Surge Monitor test on Lightning Arrester.

Surge monitor test is so conducted using auto transformer and 5kV step-up transformer. The output

voltage link of the step up transformer is connected to the surge monitor gauge meter giving input

voltage of 40V to the surge gauge. while giving the voltage, the monitor meter should deflect towards

the right of the scale and the counter should read in an increasing order. If the counter reads in an

decreasing order the surge meter is found to be not working and ultimately the meter should be

changed.

Isolator Interlock operation for all bays.

Page no: RB6

For 89B close interlock coil (It pick only I/C, if u wish u can close 89B or u can keep it open)

*** All bays 89C should be in open condition and TTX should not be operated.

Page no: RB5

For 89C Interlock


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***All bays 89B should open and bay in normal mode and operate the TTX circuit. (NE1 for line).

Then Interlock gets satisfied.

precommissioning test for 220kv substation dajay

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