Electric power distribution Feeder

7/29/2019 Electric power distribution Feeder

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STATION: NTPC SIMHADRI BHEL REF NO : PS-DC-186-500-NTPC REF NO : SIM/1/TS/1/

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PLANT AREA : 400 KV SWITCHYARD

TESTING SCHEDULE : 400 KV SWITCHYARD FEEDER

LIST OF CONTENTS

1. PLANT DETAILS

2. TESTING OBJECTIVES

3. TESTING PROPOSALS

4. SERVICES REQUIRED

5. SAFETY PRECAUTIONS

6. EMERGENCY PROCEDURES

7. STATE OF THE PLANT

8. COMMISSIONING PROCEDURE

9. COMPLETION CRITERIA

10.APPENDICES


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1. PLANT DETAILS:

The system consists of

i. SF6 Circuit breaker

ii. Isolators

iii. Earth switches

iv. Current transformer

v. Capacitor voltage transformer

vi. Lightning arrestor

NAME PLATE DETAILS:

1. SF6 CIRCUIT BREAKER

MAKE : BHEL HYDERABAD TYPE : 3AT2

LOCATION : 400 KV SWITCHYARD

RATED VOLTAGE : 420 KV RATED CURRENT : 3150 AMPS

CONTROL VOLTAGE : 220V DC

2. ISOLATORS (MAKE : S &S SWITCHGEAR, CHENNAI )

TYPE : HORIZONTAL CENTRE BREAK

RATED VOLTAGE : 400 KV RATED CURRENT : 2000 A

AUX. SUPPLY : 220 V DC CONTROL

415 V AC MOTOR3. EARTH SWITCHES

MAKE : S & S SWITCHGEAR TYPE : V L E


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4. CURRENT TRANSFORMER:

MAKE : BHEL BHOPAL TYPE : OUTDOOR

SYSTEM VOLTAGE : 400 KV RATIO : 500-1000-2000/1 A

SHORT TIME THERMAL RATING : 40 KA/ 1 SEC. NO. OF CORES: 5

CLASS : PS (4 CORES) & 0.2 ( 1 CORE) MET CT BURDEN: 40 VA

KNEE POINT VOLTAGE : 2000 volts EXCITATION CURRENT : 30 mA (s1-s3)

60 mA(s1-s2)

5. CAPACITOR VOLTAGE TRANSFORMER:

MAKE : BHEL BHOPAL TYPE : OUTDOOR

RATED VOLTAGE (PH N) : 400 KV/3 / 110 V/3

VOLTAGE FACTOR : 1.5/3 SEC TOTAL CAPACITANCE : 4400 pf

NOMINAL INTERMEDIATE VOLTAGE : 22 KV/3

6. LIGHTNING ARRESTORS:

MAKE : WS INDUSTRIES(INDIA) LTD,BANGALORE

TYPE : METAL OXIDE , GAPLESS

RATED VOLTAGE : 390 KV (rms) RATED CURRENT : 10 KA

MAXIMUM DISCHARGE CAPABILITY: 8KJ/KV

MAXIMUM FRONT OF WARE SPARK OVER VOLTAGE : 1050 KVP


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2. TESTING OBJECTIVE:

TO TEST THE 400 KV SWITCHYARD FEEDER /LINE AND MAKE

IT READY FOR COMMISSIONING.


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3. TESTING PROPOSAL:

The 400 KV Switchyard feeder will be checked and tested as per the standard

checklist and field test reports of its under mentioned equipments.

i. SF6 Circuit breaker

ii. Isolators

iii. Earth switches

iv. Current transformer

v. Capacitor voltage transformer

vi. Lightning arrestor

vii. Control & Relay panel


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4. SERVICES REQUIRED:

4.1 Calibrated Test Kit

a. 5 KV Hand/Motorised Megger

b. 500 V Megger

c. Earth Megger

d. Pressure and Temperature gauges

e. Milli second timer

f. Digital Multimeter

g. Micro Ohm meter / Kelvins Double bridge

h. Clamp-on meter for current measurement

i. Operational analyzer(Optional)

j. Motwane analogue multimeter

k. Tan delta equipment

4.2 Current Injection Kit

4.3 3 Phase 415 V AC 50 Hz Supply

4.4 1 Phase 230 V AC 50 Hz Supply

4.5 1.5 V Battery cell for checking the polarity of CTs


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5. SAFETY PRECAUTIONS:

5.1 The engineer-in-charge of the testing team will inform each member of

the test as to exact nature and extent of his contribution and

responsibilities towards tests carried out.

5.2 Only nominated persons will take part in the tests. All others will remain

clear of the area.

5.3 All persons must acquaint themselves with use and location of fire

extinguishers and First-Aid Box.

5.4 Each test will be carried out under the control of test team leader

5.5 A strict and safe method of applying test leads shall be practiced. Bare

wires should not be used in stead proper lugs must be used. All test

connections shall be tightened and rechecked.

5.6 A record of any alterations made during the tests such as shorts or

disconnections shall be made and annexed to the relevant test

procedures.

5.7 Each test will be carefully planned so that there is no mechanical or

electrical damage to the equipment under test.

5.8 Test area will be kept clean ,clearly defined and cardoned off.

5.9 When high voltage test are being made Danger/Warning notices shallbe fixed at relevant points to ensure safety and a sanction for test taken.

All isolating points to be manned.


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6. EMERGENCY PROCEDURE:

6.1 Shock treatment chart and first-aid box will be made available.

6.2 Emergency telephone numbers for hospital and fire services shall be

prominently displayed.

6.3 A telephone will be available nearby


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7. STATE OF THE PLANT:

7.1 Erection of 400 KV Bus and its associated equipments completed.

7.2 Earthing of the equipments completed

7.3 Oil level in CT,CVT & Circuit Breaker is OK.

7.4 400 KV Bus Bar is dead

7.5 Clearance from erection department for carrying out various tests obtained.

7.6 Area of test is completely isolated from illegal entry of trespassers


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8. COMMISSIONING PROCEDURE:

8.1.0 CURRENT TRANSFORMER

An outdoor CT is of a single-phase design. It is used in a switchyard for

metering as well as protection purposes.

CT TESTS

8.1.1 Insulation Resistance test

Insulation resistance test has to be carried out for checking the

healthiness of the Insulation. A 5 / 2.5 kV Megger is used for testing the

insulation between Primary terminal and earth. Same test is repeated

between primary and secondary windings.

However, a 500 V Megger is used for testing Insulation between secondary

and earth. If CT has more than one secondary windings, then insulation is

measured between secondary windings also.

8.1.2 Polarity Test

Each current transformer must be subjected to polarity test to prove that

the primary (P1 and P2) and secondary (S1 and S2) terminals are correctly

identified. For this test a moving-coil analogue multimeter is connected

across the secondary winding, with the meter positive terminal coupled to

S1. A low voltage battery, with series-connected switch, is then connected to

the primary terminals, such that the battery positive terminal is coupled to

P1. When the battery is switched on, the meter should flick in the positive

direction .The meter will flick negatively when the switch is opened.


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8.1.3 Magnetizing curve

Energizing the secondary winding from a variable voltage AC mains source,whilst the primary remains open-circuited checks the magnetizing curve of

each CT. It is customary to measure the applied voltage and the

magnetizing current at five points in increasing steps. The test results, when

plotted, resemble a B-H curve, but represent the properties of the CT as

whole rather than just the properties of the core material. The CT is said to

be approaching the knee or saturation point when a 10% increase of

applied voltage results in a 50% increase in magnetizing current. For a

protection class CT, the knee point may not occur until approximately 10

times rated secondary current is attained. In order to obtain the voltage

required to carry out a magnetizing test for a 1A secondary CT, a stepup

transformer has to be used.

8.1.4 Current - Ratio

Finally a ratio check has to be carried out. It is customary to conduct this in

conjunction with the primary injection tests mentioned later. Current is

passed through the primary circuit with the help of a primary injection kit. A

suitable ammeter is connected to the secondary circuit, which is connected

to its normal circuit load. The ratio of the primary to the secondary currents

should approximate closely to that stamped on the CT identification plate.

For ratio check primary current injected shall be approx. 50% of the rated

current.

8.1.5 Secondary Winding Resistance should be taken with a Digital

multimeter.


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8.1.6 Spark gap setting

Check spark gap setting on p1 terminal by placing a 6 mm thick packerinside the gap, adjust the cam and tightened its screw (applicable for CTs of

220 kV class and above).

Lastly, it must be ensured that the power factor testing terminal earthing link

is in its proper position and CT must be energized only if earthing link is

firmly connected.

8.2.0 CAPACITOR VOLTAGE TRANSFORMER

An outdoor CVT is of a single-phase design. It is used in a switchyard for

Metering as well as protection purposes.

CVT TESTS

Insulation Resistance test


healthiness of the Insulation. A 5 kV / 2.5kV Megger is used for testing the

insulation between Primary terminal and earth. Same Test is repeated

between primary and secondary windings.

However a 500 V Megger is used for testing Insulation between secondary

and earth. If VT/ CVT has more than one secondary windings then insulation

is measured between secondary windings also.


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8.2.2 Polarity test

Voltage transformer polarity is checked in the same manner as for a CT,taking care to ensure that the battery is connected to the primary winding.

8.2.3 Voltage Ratio test

Ratio test is conducted using a low voltage, i.e. mains source. A single-

phase 230V supply is applied to the primary winding with the secondary

winding open-circuited, then a high impedance voltmeter is used to measure

the secondary voltage to determine the voltage ratio.

8.2.4 Secondary Winding Resistance should be taken with Digital multimeter.

8.3.0 LIGHTNING ARRESTOR:

A station lightning arrestor is of single-phase design, suitable for outdoor

service. It is designed to limit surge voltages to a safe value by

discharging the surge current to ground.

LIGHTNING ARRESTOR TESTS:

8.3.1 Insulation Resistance Test


healthiness of the Insulation. A 5 kV Megger is used for testing theinsulation between each stack and earth.


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8.3.2 Test for healthiness of milliammeter

Continuity of ammeter can be checked by giving a single-phase voltage, insteps of 5 volts, starting from 5 volts. The ammeter will show deflection

corresponding

to the voltage applied. For each step of increase in voltage, the

corresponding deflection will be more.

8.3.3 Test for healthiness of surge counter

Applying a single-phase ac source can check operation of counter. A 220

volts pulse is given to the two ends of counter momentarily, with the help

of a 1-phase variac and then disconnected. The value of counter will

change, which indicates the healthiness of counter.

8.4 CIRCUIT BREAKER :

8.4.1 INSULATION RESISTANCE MEASUREMENT:

Insulation Resistance is measured using a 5 KV Motorised Megger for

checking the healthiness of insulators. It is measured across poles when CB is

open and between each pole and earth when CB is closed.

A 500 V Megger is used to check the insulation level of control wiring and

incoming 3 phase AC supply cable

8.4.2 MEASUREMENT OF COIL RESISTANCE TRIP & CLOSING:These are measured with the help of a digital multimeter for site record.

8.4.3 CONTACT RESISTANCE MEASUREMENT:

Contact resistance can be measured by passing 100A DC current through

the contacts and measuring millivolt drop across the contacts using thin


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leads having negligible voltage drop. Then contact resistance is calculated

as a ratio of measured millivolt to the applied current. These values are

compared with factory tests and should match with them.

8.4.4 C & TAN DELTA VALUE MEASUREMENT OF GRADING CAPACITORS:

Using a Semi-automatic/automatic 10 KV test kit consisting of a schering

bridge ,this measurement is carried out at site. The values are directly

recorded from the test kit in UST mode when the bridge is balanced.

8.4.5 CONTACTS CLOSING AND OPENING TIME MEASUREMENT:

It is measured with the help of time interval meter/breaker operational

analyzer. The readings are directly recorded from the test kit. These

values should match with the factory test results and should be within

acceptance limit.

8.5 ISOLATORS:

8.5.1. INSULATION RESISTANCE MEASURMENT:

Insulation Resistance is measured using a 5 KV Motorised Megger for

checking the healthiness of insulators.

Healthiness of insulation of control wiring and motor circuit is checked with

the help of a 500 v Megger.

8.5.2 HEALTHINESS OF AUXILIARY CONTACTS:

It can be checked with the help of a continuity tester. All the NO and NC

contacts are checked in both the positions of isolators i,e open and close.


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8.5.3 OPERATING CURRENT OF THREE PHASE AC MOTOR:

It is measured with the help of a clamp-on meter. The current in all threephases should be balanced.

8.5.4 OPERATION OF OVERLOAD RELAY:

This relay is checked using the phenomenon of single phasing. For

this,the output is connected to motor and set the overload relay for a

particular value. Then current is applied by means of a secondary

injection kit through any two phases at the input of the relay;leaving the

third phase open. Check the relay is operated around set value of

bimetallic relay.

8.5.5 CONTACT RESISTANCE MEASURMENT:

Contact resistance can be measured by passing 100A DC current through

the contacts and measuring millivolt drop across the contacts using thin

leads having negligible voltage drop. Then contact resistance is calculated

as a ratio of measured millivolt to the applied current. These values are

compared with factory tests and should match with them.

8.5.6 LOCAL & REMOTE OPERATION (ELECTRICAL):

For the local operation of isolator, its earthswitch and associated circuit

breaker should be open and all other interlocks with the bus earth switch

are satisfied. The castle key is inserted and DC&AC supplies are switchedON. Now the local command is given through a rotary switch mounted on

the MOM Box in the field.

For the remote operation,the local./remote switch is put in remote mode

and the command is given from the control panel in the control room

through a rotary switch.


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8.6 EARTHSWITCHES:

8.6.1 INSULATION RESISTANCE MEASURMENT:

8.6.2 HEALTHINESS OF AUXILIARY CONTACTS:

8.6.3 OPERATING CURRENT OF THREE PHASE AC MOTOR:

8.6.4 OPERATION OF OVERLOAD RELAY:

The above tests are carried out as same as that of isolators as mentioned

above.

8.6.5 CHECKING OF CONTINUITY OF EARTH BLADE WITH EARTHING

SYSTEM :

It is checked with the help of a 500 V Insulation Tester and the value

should be zero which confirms the continuity of the earth blade with the

earthing system.

8.6.6 LOCAL OPERATION (ELECTRICAL & MECHANICAL):

For the local electrical operation of Earthswitch, its isolator should be open.

The castle key is inserted and DC&AC supplies are switched ON. Now the

local command is given through a rotary switch mounted on the MOM Box

in the field.

For the local mechanical operation, Castle key is taken out from the frontdoor and put into the side door fitting of MOM Box. Now the earthswitch is

free to be operated manually with the help of the lever.


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9. COMPLETION CRITERIA:

ALL MEASUREMENTS TAKEN DURING TESTS HAVE BEEN

RECORDED AND FOUND IN ACCEPTANCE LIMITS. FEEDER IS

READY FOR SYSTEM COMMISSIONING.


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10. APPENDICES:

DRAWINGS :

1. SINGLE LINE DIAGRAM OF 400 KV SWITCHYARD (No: TB DG 186

510 0101 ,REV 02)

2. OGA DRAWINGS OF CT,CVT & LIGHTNING ARRESTORS (No: TB

DG 186 316 0241/01,251/01 & 351/01)

3. OGA DRAWINGS OF CB, BPI (No: TB DG 186 316 0201/00,301/00)

4. WIRING DRAWINGS OF CT,CVT & SF6 CIRCUIT BREAKERS (No:

TB DG 186 316 0242/01,252/01 & 205/00)

5. SCHEMATIC DRAWINGS FOR ISOLATORS AND EARTHSWITCHES.

(No: 3 562 510 0277)

6. GENERAL ARRANGEMENT DRAWINGS FOR ISOLATORS AND

EARTH SWITCHES. (No: 3 562 316 0271,272, 274)

7. SCHEMATIC DRAWING OF 400 KV FEEDER(No: 3 562 316

0296/R03)

8. SCHEMATIC, WIRING & GA DRAWINGS FOR CIRCUIT BREAKER

(No: 3 562 316 0204/01,205/00 & 201/00)

9. O&M MANUAL OF CT, CVT, ISO, LA (No: TB OM 186 316 0250, 260,

297, 362)

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Electric power distribution Feeder