INTRODUCTION:INTRODUCTION:CB CB CTCTCVTCVTLALAWAVE TRAPWAVE TRAPISOLATORSISOLATORS

400kV CURRENT 400kV CURRENT TRANSFORMERTRANSFORMER

CURRENT TRANSFORMERCURRENT TRANSFORMER

I2

I1

PrimaryI1

Secondary I2

Current Transformer :

Kn

n

I

I

I.nI.n

1

2

2

1

2211

Ampere-TurnsConservation

Law

1n

2n

K : Transformation

ratio

TYPES OF CTTYPES OF CT LIVE TANK CT LIVE TANK CT

In 400kV : CGL makeIn 400kV : CGL make

DEAD TANK CT DEAD TANK CT

In 400kV : ABB,BHEL,AREVA makeIn 400kV : ABB,BHEL,AREVA make

TYPE OF DEAD TANK CT:TYPE OF DEAD TANK CT:

Hair pin design.Hair pin design.

Eye bolt design.Eye bolt design.

DEAD TANK & LIVE TANK CTDEAD TANK & LIVE TANK CT

LIVE TANK CTLIVE TANK CT

1. Diaphragm bellows2. CT cores3. HT primary terminal4. Primary conductor assembly5. Head housing6. Core housing7. Porcelain shell8. Bushing tube9. Capacitive grading layer10. Secondary terminal blocks12. Ground pad13. Secondary terminal box14. Base assembly15. Sealing plate

1. Oil filling plug

2. Dome

3. Nitrogen filling valve

4. Collar

5. Primary terminal

6. Porcelain insulator

7. Insulated primary

8. Cover plate for tank

9. Tank

10. Secondary cores

Eye bolt design

EYE BOLT DESIGN : Up to 245kVEYE BOLT DESIGN : Up to 245kV

1. Dome

2. Nitrogen filling valve

3. Primary terminal

4. Collar

5. Porcelain insulator

6. Primary conductor with insulation

7. Adaptor cylinder

8. Secondary cores

9. Base

10. Oil drain plug

HAIR PIN DESIGNHAIR PIN DESIGN

Hair-Pin design

IT 400 Cross section

HERMETIC SEALING:HERMETIC SEALING: Metallic bellows : Metallic bellows : **CT is hermetically sealed by the **CT is hermetically sealed by the

bellows. Oil filled metallic bellows bellows. Oil filled metallic bellows compensates for the oil volume compensates for the oil volume variation due to ambient temperature variation due to ambient temperature changeschanges

Nitrogen gas filled dome.Nitrogen gas filled dome.**The space above the oil is filled with **The space above the oil is filled with

nitrogen which acts as a cushion for nitrogen which acts as a cushion for changes in oil volume due to changes in oil volume due to temperature and load current temperature and load current variations.variations.

**The positive pressure of nitrogen **The positive pressure of nitrogen inside prevents contamination from inside prevents contamination from outside atmosphere, thereby provide outside atmosphere, thereby provide effective hermetical sealing. effective hermetical sealing.

FUNCTION OF CT :FUNCTION OF CT : Converts primary current in to Converts primary current in to

low magnitude secondary low magnitude secondary current for application of current for application of metering & protection metering & protection purposes.purposes.

Five Cores are present in CT Five Cores are present in CT

i) Core 1 & 2 for bus bar i) Core 1 & 2 for bus bar protection.protection.

ii) Core 3 for metering purpose.ii) Core 3 for metering purpose.

iii) Core 4 & 5 for distance iii) Core 4 & 5 for distance protection.protection.

CURRENT TRANSFORMERSCURRENT TRANSFORMERSRATINGSRATINGS

RATED CURRENT WITH EXTENDED RATED CURRENT WITH EXTENDED CURRENT LIMITSCURRENT LIMITS

RATED SHORT TIME CURRENTRATED SHORT TIME CURRENT INSULATION LEVEL.INSULATION LEVEL.NO. OF SECONDARIES.NO. OF SECONDARIES.BURDEN & ACCURACY CLASSBURDEN & ACCURACY CLASS

CT ACCURACIES

As per IEC-60044(1)

Metering Core – ±0.2 or 0.5%at rated Currents

Protection Cores – ± 1% at rated current

METERING COREMETERING CORE

ClassClass 5% of 5% of rated Irated I

20% of 20% of rated Irated I

100% 100% of of

rated Irated I

120% 120% of of

rated Irated I

0.20.2 0.750.75 0.350.35 0.20.2 0.20.2

0.50.5 1.51.5 0.750.75 0.50.5 0.50.5

PROTECTION CORES

ClassClass Current Error Current Error at rated at rated Primary Primary CurrentCurrent

Composite Error Composite Error at rated accuracy at rated accuracy

limit Primary limit Primary CurrentCurrent

5P5P ±1%±1% ±5%±5%

10P10P ±3%±3% ±10%±10%

RATIO & PHASE ERRORRatio Error = (KnIs- Ip)*100/ Ip

Kn = Rated transformation ratioIp = Actual primary currentIs = Actual secondary current

The difference in Phase between the Primary and Secondary current vectors is phase angle error.

Knee Point VoltageKnee Point Voltage10% increase in Voltage will lead to 50% 10% increase in Voltage will lead to 50% or more increase in Current.or more increase in Current.

Current TransformersCurrent TransformersSaturation curveSaturation curve

10 20 30 40

InductionB [T]

Primary currentIp/In

Protection CT

18500 gauss

Metering CT

8000 gauss

INSULATION LEVEL

For Windings having Um greater than 300kV, the rated insulation level is determined by rated switching and lightning impulse withstand voltage

For voltages < 300kV, insulation levels are decided by lightning impulse and power-frequency withstand voltages

System System VoltageVoltage

1 min 1 min Power Power Freq. Freq.

VoltageVoltage

Switching Switching Impulse Impulse

withstand withstand VoltageVoltage

Lightning Lightning Impulse Impulse

withstand withstand VoltageVoltage

220kV220kV 395kV395kV

460kV460kV-- 950kV950kV

1050kV1050kV

400kV400kV 630kV630kV 1050kV1050kV 1425kV1425kV

INSULATION LEVEL

Checks on CTChecks on CT Check for any transit damageCheck for any transit damage Check the nitrogen pressure on the top Check the nitrogen pressure on the top

chamber before commissioning.chamber before commissioning. Check oil level in CT.Check oil level in CT. Attend leakages on bushings immediately.Attend leakages on bushings immediately. Examine the porcelain for dirt deposits & clean Examine the porcelain for dirt deposits & clean

periodically.periodically. Prior to erection confirm the position of P1 & P2 Prior to erection confirm the position of P1 & P2

terminal of primary.terminal of primary.

Checks on CT ….(Contd)Checks on CT ….(Contd) Ensure that the terminals of unloaded Ensure that the terminals of unloaded

secondary are shortedsecondary are shorted Check that tank is earthed positively and Check that tank is earthed positively and

permanently. permanently. Use the lifting lugs provided on the bottom Use the lifting lugs provided on the bottom

tank for lifting the CT by slingstank for lifting the CT by slings Check the level of bellow.Check the level of bellow. Check earthing of star point of secondary at Check earthing of star point of secondary at

relay panel before commissioning of CT.relay panel before commissioning of CT. Check earthing of Tan delta point.Check earthing of Tan delta point. Secondary box cover is closed tightly.Secondary box cover is closed tightly.

Checks on CT Contd..Checks on CT Contd.. Testing of oil after one month of Charging.Testing of oil after one month of Charging. All the CT’s secondary TB’s must be properly All the CT’s secondary TB’s must be properly

tighten at CT’s JB,MB & at relay panel.tighten at CT’s JB,MB & at relay panel. Do not allow dirt and deposits on bushings. Clean Do not allow dirt and deposits on bushings. Clean

periodicallyperiodically Do not leave terminals of unloaded secondary openDo not leave terminals of unloaded secondary open Do not lift the CT by primary terminals or by Do not lift the CT by primary terminals or by

porcelain housing.porcelain housing. Carry out thermovision scanning after Carry out thermovision scanning after

commissioning of CT.commissioning of CT.

CURRENT TRANSFORMERSCURRENT TRANSFORMERSPRECOMMISSIONING TESTSPRECOMMISSIONING TESTS

INSULATION RESISTANCE MEASUREMENTINSULATION RESISTANCE MEASUREMENT CONTINUITY TESTCONTINUITY TEST SECONDARY WINDING RESISTANCESECONDARY WINDING RESISTANCE POLARITY TESTPOLARITY TEST TAN DELTA AND CAPACITANCE MEASUREMENTTAN DELTA AND CAPACITANCE MEASUREMENT CURRENT RATIO TESTSCURRENT RATIO TESTS MAGENTISING CURVES PERFORMANCEMAGENTISING CURVES PERFORMANCE CONTACT RESISTANCE MEASUREMENTCONTACT RESISTANCE MEASUREMENT

CURRENT TRANSFORMERSCURRENT TRANSFORMERSMAINTENANCE MONTHLYMAINTENANCE MONTHLY

CHECK OIL LEAKAGE FROM CTCHECK OIL LEAKAGE FROM CT

CHECKING BELLOW FOR EXPANSIONCHECKING BELLOW FOR EXPANSION

CHECK OIL LEAKAGE FROM SECONDARY CHECK OIL LEAKAGE FROM SECONDARY TERMINALSTERMINALS

CHECKING HEALTHINESS OF GASKETSCHECKING HEALTHINESS OF GASKETS

CURRENT TRANSFORMERSCURRENT TRANSFORMERSMAINTENANCE YEARLYMAINTENANCE YEARLY

CLEANING CLEANING

TIGHTENING OF TERMINAL TIGHTENING OF TERMINAL CONNECTORS AND SECONDARY CONNECTORS AND SECONDARY TERMINALSTERMINALS

THERMOVISION SCANNINGTHERMOVISION SCANNING

CURRENT TRANSFORMERSCURRENT TRANSFORMERSMAINTENANCE 1 YEARLYMAINTENANCE 1 YEARLY

1. TAN DELTA & CAPACITANCE MEASUREMENT1. TAN DELTA & CAPACITANCE MEASUREMENT

ACCEPTABLE LIMIT FOR TAN DELTA 0.007ACCEPTABLE LIMIT FOR TAN DELTA 0.007 INCREASE IN PRE-COMM VALUE AT 0.001 INCREASE IN PRE-COMM VALUE AT 0.001

PER YEAR UPTO 0.007PER YEAR UPTO 0.007 IF VALUE IS BETWEEN 0.007 TO 0.01 THEN IF VALUE IS BETWEEN 0.007 TO 0.01 THEN

HALF YEARLY MONITORINGHALF YEARLY MONITORINGABOVE 0.01 REPLACE THE CTABOVE 0.01 REPLACE THE CT

NITROGEN PRESSURE CHECKING (3 Yearly )NITROGEN PRESSURE CHECKING (3 Yearly )

CAPACITIVE VOLTAGE CAPACITIVE VOLTAGE TRANSFORMERTRANSFORMER

CVTCVT(Measurement of HV)(Measurement of HV)

Capacitor Voltage TransformersCapacitor Voltage TransformersLine protectionLine protectionHF transmissionHF transmission CVT are used to convert higher primary voltage CVT are used to convert higher primary voltage

to lower secondary voltage for the protection & to lower secondary voltage for the protection & metering purpose.metering purpose.

CVT provide least resistance path to higher CVT provide least resistance path to higher frequency signals for PLCC functions.frequency signals for PLCC functions.

CAPACITOR VOLTAGE CAPACITOR VOLTAGE TRANSFORMERTRANSFORMER

Capacitance potential divider connected between phase and ground of power circuit.

CAPACITOR VOLATGE CAPACITOR VOLATGE TRANSFORMERTRANSFORMER

Capacitor STACK(or stack)

Capacitor STACK(or stack)

Assembly of elements to reach higher voltage levels : ± 800 kV

HV Power line

Ground

In general, the termCAPACITOR

stands for a capacitor elementas well as a capacitor stack.

Capacitor Voltage Divider( or CVT )

Capacitor Voltage Divider( or CVT )

Connecting an MV inductive voltage transformer to a tap.

HV Power line

Ground

IntermediateVoltage :

10 to 20 kV/3

S1

S2

P1

P2

C1

C2

CVT CIRCUIT

Capacitor elements

Capacitor column

Insulating oil

Insulator flange

Secondary terminal box

Inductance

MV Transformer

Oil expansion device

Damping circuit

CVT SECONDARY VOLATGECVT Secondary Voltage v = k * V * C1/ (C1+C2)

V – Primary Voltage

k – Secondary Transformation ratioThere are 280 – 300 elements in C1 & C2 C1 will be about 260 to 280 elementsC2 will be 15 to 20 elements

NOTE:Puncturing of C1 – Secondary Voltage will increase

Puncturing of C2 – Secondary Voltage will decrease

SECONDARY VOLATGE

Periodic measurement to be carried out. In case of doubt, simultaneous measurement to be carried out with another feeder/ Bus CVT.

For 400kV CVTs puncturing of one Capacitor element in C1 side is likely to increase Secondary Voltage by about 0.35 – 0.45% (0.22 – 0.28V)

Failure of one Capacitor element in C2 side is likely to decrease Secondary Voltage by 5 – 6% (3.2 – 3.8V)

CVT RATINGCVT RATING

RATED PRIMARY VOLTAGERATED PRIMARY VOLTAGE

RATED SECONDARY VOLTAGERATED SECONDARY VOLTAGE

RATED BURDEN OF CORESRATED BURDEN OF CORES

CAPACITANCE IN pF (FOR CVT ONLY)CAPACITANCE IN pF (FOR CVT ONLY)

CLASS OF ACCURACYCLASS OF ACCURACY

CVTCVTREQUIRMENTSREQUIRMENTS

3 SECONDARIES (2 FOR PROTECTION 3 SECONDARIES (2 FOR PROTECTION AND ONE FOR METERING)AND ONE FOR METERING)

OUTPUT BURDEN 50 VA MINIMUM FOR OUTPUT BURDEN 50 VA MINIMUM FOR EACH SECONDARYEACH SECONDARY

3P ACCURACY CLASS FOR PROTECTION 3P ACCURACY CLASS FOR PROTECTION CORESCORES

0.2 ACCURACY CLASS FOR METERING 0.2 ACCURACY CLASS FOR METERING CORECORE

CVT CVT PRECOMMISSIONING TESTSPRECOMMISSIONING TESTS

INSULATION RESISTANCE MEASUREMENTINSULATION RESISTANCE MEASUREMENT

CONTINUITY OF WINDINGCONTINUITY OF WINDING

SECONDARY WINDING RESISTANCESECONDARY WINDING RESISTANCE

VOLTAGE RATIO TESTVOLTAGE RATIO TEST

TAN DELTA AND CAPACITANCE TAN DELTA AND CAPACITANCE MEASUREMENTMEASUREMENT

CVTCVTMAINTENANCEMAINTENANCE

MONTHLY:MONTHLY: LEAKAGE OF OIL.LEAKAGE OF OIL.QUARTERLY:QUARTERLY: SECONDARY VOLTAGESECONDARY VOLTAGEYEARLY:YEARLY: CHECKING OF EARTHING OF HF POINTCHECKING OF EARTHING OF HF POINT

DAMAGE TO BUSHING OF HF POINTDAMAGE TO BUSHING OF HF POINT

CLEANING OF PORCELAIN INSULATOR STACKS AND CLEANING OF PORCELAIN INSULATOR STACKS AND TIGHTNESS OF TERMINAL CONNECTORTIGHTNESS OF TERMINAL CONNECTOR

THERMOVISION SCANNINGTHERMOVISION SCANNING

CHECKING OF NEUTRAL EARTHINGCHECKING OF NEUTRAL EARTHING3 YEARLY3 YEARLYTAN DELTA MEASUREMENTTAN DELTA MEASUREMENT

CHECKS FOR CVT CHECKS FOR CVT

Check for any transit damage.Check for any transit damage.Check oil level in EMU Unit.Check oil level in EMU Unit.Check leakages on CVT .Check leakages on CVT .Examine the capacitor porcelain for Examine the capacitor porcelain for

dirt deposits and clean periodically on dirt deposits and clean periodically on de-energized and safely earthed CVT.de-energized and safely earthed CVT.

Check that the primary and secondary Check that the primary and secondary terminal box covers are in position terminal box covers are in position and sealed properly.and sealed properly.

II

CHECKS FOR CVT CHECKS FOR CVT Check NHF point is earth when not used for Check NHF point is earth when not used for

PLCC.PLCC.Check all the secondary wiring connections Check all the secondary wiring connections

are tightly secured at the terminal box.are tightly secured at the terminal box.Units must be short circuited with a bare Units must be short circuited with a bare

wire between head & bottom flange until wire between head & bottom flange until erection and connections are completed.erection and connections are completed.

The Tank of CVT should be earthed properly.The Tank of CVT should be earthed properly.Regularly monitor secondary voltage of Regularly monitor secondary voltage of

CVT’s w.r.t each other to identify any CVT’s w.r.t each other to identify any discrepancy in CVT secondary voltage.discrepancy in CVT secondary voltage.

II

CAUTIONS FOR CVT CAUTIONS FOR CVT Never keep the units horizontally.Never keep the units horizontally.Do not energized CVT from the Do not energized CVT from the

secondary side.secondary side.Discharge CVT prior to climbing.Discharge CVT prior to climbing.While removing connector from the While removing connector from the

CVT ensure local earthing on CVT ensure local earthing on conductor as well as on CVT.conductor as well as on CVT.

SURGE ARRESTORSURGE ARRESTOR

SURGE ARRESTORSSURGE ARRESTORS

PROTECTS SUBSTATION EQUIPMENTS PROTECTS SUBSTATION EQUIPMENTS FROM TRANSIENT OVERVOLTAGES FROM TRANSIENT OVERVOLTAGES

CONNECTED BETWEEN PHASE AND EARTH CONNECTED BETWEEN PHASE AND EARTH

PROVIDES LOW RESISTANCE PATH TO PROVIDES LOW RESISTANCE PATH TO EXCESSIVE HIGH VOLTAGE.EXCESSIVE HIGH VOLTAGE.

RATING IN PHASE TO EARTH VOLTAGERATING IN PHASE TO EARTH VOLTAGE

SURGE ARRESTORSSURGE ARRESTORS

GAPPED SILICON CARBIDE SURGE GAPPED SILICON CARBIDE SURGE ARRESTORSARRESTORS

GAPLESS ZINC OXIDE ARRESTORS GAPLESS ZINC OXIDE ARRESTORS

(PREFERRED THESE DAYS DUE TO HIGHER (PREFERRED THESE DAYS DUE TO HIGHER ENERGY ABSORPTION CAPABILITIES) ENERGY ABSORPTION CAPABILITIES)

MADE OF SMALL DISCS OF NON-MADE OF SMALL DISCS OF NON-LINEAR RESISTANCE MATERIAL ZnO LINEAR RESISTANCE MATERIAL ZnO WHICH PROVIDES LEAST RESISTANCE WHICH PROVIDES LEAST RESISTANCE PATH DURING SWITCHING SURGES OR PATH DURING SWITCHING SURGES OR LIGHTENING STROKELIGHTENING STROKE

ARRESTER ARRESTER FUNDAMENTALFUNDAMENTAL

Need for High Resistance to limit Discharge Current

Need Low Resistance during flow of lightning current to limit Surge Voltage A non-linear resistance material required

EQUIVALENT CIRCUIT OF SURGE EQUIVALENT CIRCUIT OF SURGE ARRESTERARRESTER

Concept of Leakage Current

Resistive Current

In phase with voltage

Increase with temperature

Increase with aging

Capacitive Current

In 90 Deg phase with voltage

Insignificant change with temperature and voltage

does not affect due to aging

SURGE ARRESTORSSURGE ARRESTORSPRE-COMMISSIONING TESTSPRE-COMMISSIONING TESTS

INSULATION RESISTANCE INSULATION RESISTANCE MEASUREMENTMEASUREMENT

LEAKAGE CURRENT MEASUREMENTLEAKAGE CURRENT MEASUREMENT

SURGE COUNTER CHECKSURGE COUNTER CHECK

SURGE ARRESTORSSURGE ARRESTORSMAINTENANCE YEARLYMAINTENANCE YEARLY

CLEANING CLEANING

LEAKAGE CURRENT MEASUREMENTLEAKAGE CURRENT MEASUREMENT

SURGE COUNTER CHECKSSURGE COUNTER CHECKS

WAVE TRAPWAVE TRAP

LINE TRAPLINE TRAP

LINE TRAP OFFER HIGH RESISTANCE LINE TRAP OFFER HIGH RESISTANCE TO HIGH FREQUENCY PLCC SIGNAL TO HIGH FREQUENCY PLCC SIGNAL AND LOW RESISTANCE TO POWER AND LOW RESISTANCE TO POWER FREQUENCY SIGNAL.FREQUENCY SIGNAL.

BLOCKING FREQUENCY RANGE WITH BLOCKING FREQUENCY RANGE WITH COMBINATION OF INDUCTANCE AND COMBINATION OF INDUCTANCE AND CAPACITANCE : 50Khz TO 500Khz.CAPACITANCE : 50Khz TO 500Khz.

COMPRISES OF INDUCTOR,TUNNING COMPRISES OF INDUCTOR,TUNNING CIRCUIT,LA.CIRCUIT,LA.

LINE TRAPSLINE TRAPSRATINGSRATINGS

INDUCTANCE IN MhINDUCTANCE IN Mh

RATED CURRENTRATED CURRENT

BLOCKING BANDWIDTHBLOCKING BANDWIDTH

Checks for Wave trap.Checks for Wave trap.

Tuning circuit and arrestor are Tuning circuit and arrestor are properly tightened.properly tightened.

Connectors are properly tightened.Connectors are properly tightened.Bird Guards are properly fixed.Bird Guards are properly fixed.Check for any physical damage.Check for any physical damage.

LINE TRAPSLINE TRAPSPRE-COMMISSIONING TESTSPRE-COMMISSIONING TESTS

INSULATION RESISTANCE INSULATION RESISTANCE MEASUREMENTMEASUREMENT

CONTACT RESISTANCE CONTACT RESISTANCE MEASUREMENTMEASUREMENT

LINE TRAPS MAINTENANCELINE TRAPS MAINTENANCEYEARLY CHECKSYEARLY CHECKS

TIGHTNESS & CLEANLINESS OF LINE TIGHTNESS & CLEANLINESS OF LINE TRAP INCLUDING TUNING UNITTRAP INCLUDING TUNING UNIT

TIGHTNESS OF TERMINAL TIGHTNESS OF TERMINAL CONNECTORCONNECTOR

ISOLATORSISOLATORS

Operate under no load condition.Operate under no load condition. Isolate the zone which is under Isolate the zone which is under

maintenance.maintenance.Three types of Isolators :Three types of Isolators :

A) Pantograph.A) Pantograph.

B) Horizontal center break.B) Horizontal center break.

C) Double Break.C) Double Break.

TYPE OF ISOLATORS BASED ON TYPE OF ISOLATORS BASED ON LOCATION OF USELOCATION OF USE

Line IsolatorLine IsolatorBus IsolatorBus IsolatorReactor IsolatorReactor IsolatorTransformer IsolatorTransformer Isolator

TYPE OF ISOLATORS BASED TYPE OF ISOLATORS BASED ON E/SON E/S

Without Earthswitch (Used where Without Earthswitch (Used where earthing is not required)earthing is not required)

With one Earthswitch (Commonly With one Earthswitch (Commonly used for earthing the equipment for used for earthing the equipment for which Isolator has been provided)which Isolator has been provided)

With two earth switch (Generally With two earth switch (Generally used for Bus earthing)used for Bus earthing)

Checks on IsolatorsChecks on Isolators

Proper alignment.Proper alignment.Proper fixing of limit switch.Proper fixing of limit switch.Proper closing of Isolators to avoid hot Proper closing of Isolators to avoid hot

spot.spot.Check mechanical/electrical interlock.Check mechanical/electrical interlock.Ensure twin earthing of Isolator MB.Ensure twin earthing of Isolator MB.Proper closing of Isolators MB.Proper closing of Isolators MB.

HCB ISOLATORSHCB ISOLATORS

HCB ISOLATORS—MAIN HCB ISOLATORS—MAIN CONTACTSCONTACTS

DOUBLE BREAK ISOLATORSDOUBLE BREAK ISOLATORS

DB ISOLATOR---CENTRAL ROTATING DB ISOLATOR---CENTRAL ROTATING STACK STACK

DB ISOLATOR--CONTACTSDB ISOLATOR--CONTACTS

PANTOGRAPH ISOLATORPANTOGRAPH ISOLATOR

PANTOGRAPH ISOLATOR--PANTOGRAPH ISOLATOR--CONTACTSCONTACTS

Checks on Isolators…Checks on Isolators…

Ensure proper position of NO/NC contact Ensure proper position of NO/NC contact in closed & open condition of Isolators.in closed & open condition of Isolators.

Apply grease regularly in Gear box.Apply grease regularly in Gear box.Check pole discrepancy function is Check pole discrepancy function is

working properly.working properly.

ISOLATORS AND E/SISOLATORS AND E/SPRECOMMISSIONING TESTSPRECOMMISSIONING TESTS

INSULATION RESISTANCE MEASUREMENTINSULATION RESISTANCE MEASUREMENT

INTERLOCKS CHECKINGINTERLOCKS CHECKING

OPERATING TIMEOPERATING TIME

AUXILIARY CONTACT CHECKINGAUXILIARY CONTACT CHECKING

CONTACT RESISTANCE MEASUREMENTCONTACT RESISTANCE MEASUREMENT

ISOLATORS AND E/SISOLATORS AND E/SMAINTENANCEMAINTENANCE

CLEANING & LUBRICATIONCLEANING & LUBRICATION

TIGHTENINGTIGHTENING

ALIGNMENTALIGNMENT

CONTACT RESISTANCE MESUREMENT CONTACT RESISTANCE MESUREMENT (ONCE IN A 4 YEARS)(ONCE IN A 4 YEARS)

THANK YOUTHANK YOU