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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 : LINE BAY COMMISSIONING

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. 400 kv line

ii. 400 kv switchyard feeder equipments

a) Lightning arrestor

b) Capacitor Voltage Transformer

c) Current transformers

d) Isolators

e) Earthswitches

f) Circuit breaker

iii. Control & Relay panels

MAKE : BHEL BHOPAL

RELAYS MOUNTED : LBB (ALSTOM Make,MCTI-40 Type)

(R,Y, B PHASES) Instantaneous Diff. Relay(ALSTOM Make,CAG-

34 Type)

Biased Differential Relay (ALSTOM Make,MBCH-13 Type)

Over Voltage Relay (ALSTOM Make, VTU 21 Type)

Distance relays for line protection(ALSTOM Make, EPAC

Type, MICROMHO-SHNB Type)

Line bay can be charged/commissioned in two ways

1 By charging the 400 KV main buses through Generator supply via

Generator transformer.Closing the breaker isolators,line isolators

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and Circuit breaker,Generator supply will be sent to Grid through

the main line after synchronization with the Generator supply.

2 By backcharging the bay through the line,for which, line isolator is

closed at first and the breaker isolator and circuit breaker are

closed subsequently after getting all required permissives.

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2. TESTING OBJECTIVE:

2.1To test and charge/commission the line bay and

2.2 extend the power upto the line

2.3To charge the main bus 1&2 after getting supply from the line

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3. TESTING PROPOSAL:

3.1 To test the protection relays for line bay in the Relay panel through

secondary injection

3.2 Scheme checking by green marking

3.3 To check the interlocking scheme

3.4 To check the voltage selection and synchronizing circuit

3.5 Secondary injection of CVT

3.6 To check the alarm/annunciation circuits

3.7 To check the event logger circuits

3.8 To check the disturbance recorder signals

3.9 To check the remote operation of yard equipments and their status in the

control panel

3.10 To check trip logics of Circuit breaker

3.11 Primary injection of current transformer

3.12 To check the stability of Tee differential protection

3.13 To check the stability of busbar protection

3.14 Final meggering of 400 KV bus before charging the line bay

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4. SERVICES REQUIRED:

4.1 Calibrated Test Kit

a. 5 KV DC Hand/Motorised Megger

b. 500 V DC Megger

c. Digital Multimeter

d. Clamp-on meter for current measurement

e. Phase sequence meter

4.2 ZFB Kit

4.3 Current Injection Kit (Primary & Secondary)

4.4 3 Phase 415 V AC 50 Hz Supply

4.5 Walkie talkie set for communication

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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 shall

be 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 line bay equipments as listed in plant details are 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 Testing of protection relays in Relay panel

The relays mounted in Relay panel are tested as per the checklist

8.2 Scheme checking by green marking :

The schematic drawings are fully checked for all trip logics, alarm/

annunciation logic and control logics by simulating the actual conditions. In

this manner, all the internal wiring/bus wiring of the control /Relay panel is

checked with the help of a digital multimeter and a continuity tester. Each

and every circuit is then green marked with the help of a highlighter.

8.3 Interlocking scheme checking:

The interlocking scheme is checked as per the schematic drawings(viz

schematic diagram No. 3 562 006 0296) for the sequential and correct

operation of isolators, circuit breaker and earthswitches.

8.4 Checking of Voltage selection and synchronizing circuit:

To check the voltage selection circuit and synchronisation circuit,selectedvoltage of Bus-1 and Bus-2 are extended to metering circuit andsynchronisation circuit through relays 75A and 75 B. Relays 75A & 75Boperate depending upon the selection of Main bus-1/2.

8.5 SECONDARY INJECTION OF CVT:

This involves passing current/voltage through protection relays i.e.

simulating CVT output voltages, and confirming correct operation at twosettings. The relay then has its recommended settings applied and theoperation is rechecked to confirm the set values of voltage. If applicable, thetimer of the relay is also tested. Modern relays, particularly those mounted inmodular cases, can be tested in panel by injection of a special plugconnected to the secondary injection test set.

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8.6Alarm/Annunciator circuit checking:The Alarm/Annunciator circuit is checked as per the schematic drawings(vizschematic diagram No. 3 562 006 0296)

8.7Checking of Event logger circuits:The checking for Event logger circuits are carried out as per their StandardCheck list.

8.8 Checking of Disturbance recorder signals:The checking for Disturbance recorder signals are carried out as per theirStandard Check list.

8.9 Remote operation of Yard equipments from the control panel:

Remote operation of Isolators and circuit breaker are done by givingmanual command from the control panel through a rotary switch and itsclose/open status is verified from glowing of signal lamps mounted oncontrol panel.

8.10 TRIP LOGICS OF CIRCUIT BREAKER:

Various protections / schemes are provided in a feeder / Transformer bay for

the safety of the equipment / system viz. LBB, Busbar, Over-current,

Restricted earth fault etc. The operation of the relays designated for the

above-mentioned protections can be tested by secondary injection. These

relays give command to a master trip relay, which in turn gives command to

the Breaker to trip, thus isolating the rest of the equipments from the faulty

zone.

In system-level testing, all trip tests of the Breaker are performed before

charging the system. The format for the above tests is to be filled in the

following way:

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TABULATION OF TRIP LOGICS

SL.

NO.

DESCRIPTION

TEST

SOURCE OF

INITIATION

WINDOW

DESCRIPTION

RESULT

OK/NOTOK

REMARKS

CLOSE THE BREAKERAND TRIP THROUGHPROTECTION WHICH

ARE APPLICABLE

PROTECTIONRELAY ASPER SCHEME.

BREAKERAUTO TRIP

I) MAIN - I BREAKERAUTO TRIP

II) MAIN - II BREAKERAUTO TRIP

III) OVER VOLTAGE BREAKERAUTO TRIP

IV) LBB BREAKERAUTO TRIP

V) BUS BAR BREAKERAUTO TRIP

VI) TEE DIFFERENTIAL I &II

BREAKERAUTO TRIP

8.11 PRIMARY INJECTION OF CURRENT TRANSFORMER:

This type of test involves each protection circuit, including all interconnectingwiring. It is usually carried out as a final proving test to ensure that allterminations are correct and that all CTs are mounted correctly. Typically, aprimary injection test set of up to 100A output should be adequate for themajority of circuits encountered in a switchyard.It is customary to see the operation of the relay during Primary injection. TheBreaker should trip as the relay operates. If required, the relay setting belowered to facilitate the operation of relay.

The observations can be recorded in the enclosed test format:

8.12 Checking the stability of TEE Differential Protection:

a) Through faultFollowing is the format for this testCTs involved :Stability : Through faultPhase :

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Procedure : Select any two CTs out of 3 CTs of TEE formation ofbusbar.Close the concerned isolator & circuit breaker connecting these twoselected CTs. Primary current is injected from P1 terminal of One of the

CTs(Say first CT) through a primary injection kit whose another end isconnected to earth. Close the Earthswitch after the P2 terminal of theSecond CT for return path so that primary current flows through both CTsand gets earthed after Second CT. In through fault stability or out zonefault,current in neutral circuit should be negligible. I.e. current in First CTssecondary circuit should balance with the current in second CTs secondarycircuit provided their polarity is correctly matched.

PRIMARYCURRENT

PANELREFERENCE

TERMINALBLOCKNO.

RATIOUSED

ABSOLUTEVALUE OFSEC.CURRENT

RELAYCIRCUIT

Remarks:

b) Zone faultFollowing is the format for this testCTs involved :Stability : In Zone or Zone faultPhase :

Procedure : Select any one CT out of 3 CTs of TEE formation ofbusbar. Primary current is injected from P1 terminal of the CT through aprimary injection kit whose another end is connected to earth. Close theEarthswitch after the P2 terminal of the CT for return path so that primarycurrent flows through CT and gets earthed after the CT. In Zone faultstability or zone fault, current in secondary will not be balanced and relaywill sense differential current.87TT1 & 87TT2 relays are set at a particularvalue . Increase the primary current from Zero to a value for which relay inthe secondary circuit operates. Note those values as follows

PRIMARYCURRENT

PANELREFERENCE

TERMINALBLOCK

NO.

RATIOUSED

ABSOLUTEVALUE OF

SEC.CURRENT

RELAYCIRCUIT

Observation :Remarks :

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8.13 Checking the stability of Bus bar Differential Protection:

a) Through fault

Following is the format for this testCTs involved :Stability : Through faultPhase :Procedure : Select two CTs of same phase of the busbar. Close theconcerned isolator & circuit breaker connecting these two CTs. Primarycurrent is injected from P1 terminal of One of the CTs(Say first CT) througha primary injection kit whose another end is connected to earth. Close theEarthswitch after the P2 terminal of the Second CT for return path so thatprimary current flows through both CTs and gets earthed after Second CT.In through fault stability or out zone fault, current in neutral circuit should be

negligible. I.e. current in First CTs secondary circuit should balance withthe current in second CTs secondary circuit provided their polarity iscorrectly matched.

PRIMARYCURRENT

PANELREFERENCE

TERMINALBLOCKNO.

RATIOUSED

ABSOLUTEVALUE OFSEC.CURRENT

RELAYCIRCUIT

Remarks:b) Zone faultFollowing is the format for this testCTs involved :Stability : In Zone or Zone faultPhase :Procedure : Select any one CT out of above selected 2 CTs. Primarycurrent is injected from P1 terminal of the CT through a primary injection kitwhose another end is connected to earth. Close the Earthswitch after theP2 terminal of the CT for return path so that primary current flows throughCT and gets earthed after the CT. In Zone fault stability or zone fault,

current in secondary will not be balanced and relay will sense differentialcurrent. Bus bar differential relays, MBCZ(Main-1) & PBDCB(Main-2), areset at a particular value . Increase the primary current from Zero to a valuefor which relay in the secondary circuit operates. Note those values asfollows.

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PRIMARYCURRENT

PANELREFERENCE

TERMINALBLOCKNO.

RATIOUSED

ABSOLUTEVALUE OFSEC.

CURRENT

RELAYCIRCUIT

Observation :

Remarks :

8.14 Final meggering of 400 KV Line:Final Insulation Resistance is measured using a 5 KV Motorised Megger forchecking the healthiness of insulators. It is measured between pole-to-poleand between each pole and earth.

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9. COMPLETION CRITERIA:

ALL MEASUREMENTS TAKEN DURING TESTS HAVE BEEN

RECORDED AND FOUND IN ACCEPTANCE LIMITS. LINE BAY IS

CLEARED FOR COMMISSIONING/CHARGING.

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10. APPENDICES:

DRAWING :

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. SCHEMATIC DRAWINGS FOR ISOLATORS AND EARTHSWITCHES

(No: 3 562 510 0277)

4. SCHEMATIC DRAWINGS FOR CONTROL & RELAY PANELS for

LINE-1 & 2(NO: 3 562 006 0296/Rev 03) and LINE-3 & 4(NO: 3 562

006 0298,Rev 02)

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