cvt o & m manual

8/18/2019 CVT O & M Manual

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BRIEF DESCRIPTIONHigh Voltage Capacitor Unit : (Ref. Fig. 1)The high Voltage Capacitor unit comprises of onecapacitor unit upto 170 KV and two or more Capacitor Unitsfor higher KV classes. The Capacitor Unit comprises of HVCapacitor (C1) and Intermediate Voltage Capacitor (C2).These capacitors consist of oil impregnated seriesconnected capacitor elements housed inside oil filledporcelain insulators. Each capacitor unit is independentlyhermetically sealed. Stainless steel bellow is providedinside each capacitor unit to compensate volumetricchanges in oil due to ambient temperature changes.Aluminium HV Terminal is provided on capacitor unit as

shown in Fig. 1. Bottom cover of the lowest capacitor unitforms the cover of the EM unit tank. Lifting Lugs areprovided on the tank to lift the lowest capacitor unit and theEM unit together.Intermediate Voltage Tap and high frequency CarrierTerminal (NHF) are brought from capacitor unit to EM unitthrough bushings.Electro Magnetic Unit (EMU) (Ref. Fig. 2)The EMU comprises of following electrical components:- Compensating Reactor (L)- Intermediate Transformer (Tr)- Damping Device (Zd)- Varistor (V)- HRC Fuses (F) / MCBs (M).

The Varistor (V) and the damping device (Zd) areconnected across an auxillary secondary winding (f-g). Thevaristor mounted inside secondary terminal boxsuppresses over voltages which may occur due totransients on the High voltage side or Low voltage side;whereas the damping device mounted inside EMU tankdamps the transient oscillations. The secondary windingleads and LV lead of the capacitor (NHF) are taken intosecondary terminal box through a multilead epoxy block(monoblock). Surge Arrester is provided across NHF andearth which is rated at 1kVp.The compensating reactor (L) and intermediatetransformer (Tr) are mounted inside the oil filledhermetically sealed EMU steel tank. A suitablydimensioned air cushion is provided in EMU tank toaccomodate expansion of oil. For all service temperaturesthe oil level must be within min. and max. levels. On thebottom side of the terminal box a removable undrilledgland plate is provided in which suitable holes can bedrilled at site. The HRC fuses (F) / MCBs (M) are fitted inthe secondary terminal box.Optional Accessories1) Terminal Connector2) Cable Glands3) Three Element Carrier protection device comprising ofa) Drain Coil b) Lightning Arrester c) Earth SwitchItems 1, 2 are packed seperately and 3 is mounted insidesecondary terminal box.


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PACKING, TRANSPORT AND UNLOADINGCVTs upto 170 kV are packed in a single wooden packingcrate.For higher kV classes base unit (comprising of lowestcapacitor unit and EMU) and each capacitor unit is packedseperately.WARNING : BASE UNIT AND UPPER CAPACITORUNITS SHOULD ALWAYS BE TRANSPORTED/ STOREDIN VERTICAL POSITION. IT SHOULD NEVER BETRANSPORTED/ STORED IN HORIZONTAL POSITION.

(Except upper capacitor units of 800kV)For unloading, the packing crate should always be liftedfrom bottom.Immediately on receipt, the goods should be checked fortransportation damage (if any). In case of externally visibledamages, inform CGL and the insurance companyimmediately, preferably with photographs. Also mark theposition of damage / oil leakage, if any on the CVT outlinedrawing enclosed with this manual and send it to CGL.Use nail puller while unpacking. While unpacking utmostcare should be taken to prevent any damage to the CVT.Store the CVT only in vertical position on a hard, dry andeven surface.For taking the base unit out of packing use lifting lugsprovided on the EMU cover (Refer Fig. 3)and for taking topcapacitor unit out of packing case, tie the rope in the neckofporcelain of this unit below Al. flangeFor lifting upper unit or middle unit, arrangement as showninFig.4 to be followed.CAUTION : 1) AVOID DAMAGE TO THE HV TERMINALWHILE LIFTING THE UPPER CAPACITOR UNIT.2) WHILE LIFTING THE BASE UNIT SAFETY ROPE HASTO BE TIED AS SHOWN IN FIG. 3

ERECTIONUpper Capacitor units belonging to the same CVT are markedat our works by the same serial number suffixed by U.For example: Serial number on the main rating plate fixed on the baseunit - 1000: Serial Number on the number plate fixed on uppercapacitor unit - 1000/U: Similarly middle capacitor unit is marked by same serialno.suffixed by M. For example -1000/M.CAUTION : ENSURE CAPACITOR UNITS WITH SAMESERIAL NUMBERS ARE COUPLED DURINGERECTION OF CVT WITH TWO OR MORE CAPACITORUNITS.The hardwares necessary for assembly of upper capacitorunit on the base unit are packed seperately. (Refer Fig. 4)

for this assembly.Initially the base unit has to be mounted and fixed on thesupport structure. For fixing the base unit, four holes areprovided on the bottom plate of EM Unit. (for mountingdetails refer to general arrangement drawing suppliedagainst order)The threaded studs used for coupling have to be first heldinto the through holes of the flanges, before the units areplaced one above another. This assembly has to be donewith utmost care, to prevent damage to the porcelainsheds. For handling of the base unit and upper capacitorunit during this erection process, use of crane is necessary.The studs used for coupling the capacitor units have to betightened with a torque of 6 kg-m.

A - HV TerminalC1 - Pri. CapacitorC2 - Sec. CapacitorNHF - HF TerminalL - Compensating ReactorTr - Intermediate Voltage TransformerF - HRC FuseZd - Damping DeviceV - VaristorS - Surge Arrestor

Fig. No. 2


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CAUTION : 1) UPPER AS WELL AS THE LOWERCAPACITOR UNIT HAS TO BE SHORT CIRCUITED ANDCONNECTED TO EARTH UNTIL THE ERECTION ANDCOMMISSIONING WORK IS BEING DONE ON THE CVT.(The capacitors get charged by the electrical fields in thevicinity and they keep these charges for a long time, whichwill be dangerous to human life. Hence the shorting andearthing of capacitor units is necessary.)2) DO NOT UNSCREW ANY OTHER SCREWED JOINTSOF THE CAPACITOR UNITS AND THE BASE UNIT.

ESSENTIAL CHECK BEFORE COMMISSIONING :Low Voltage Ratio Check :For low voltage ratio check apply a voltage of 100 to 2000volts between HV terminal and NHF, measure the voltageacross the secondary terminals. The ratio should notsignificantly deviate from the rated value. In case ofsubstantial deviation in this ratio, there is a possibility of aninternal damage / loose connection during transport andapparatus must not be put into operation.Report the abnormalities to CGL immediately givingfollowing details1) Customer Site2) Type designation3) S. O. No. (On rating plate)4) Sr. No. (On rating plate)5) Date of receipt at site6) Testing details7) Contact person and Telephone number.

ELECTRICALS CONNECTIONSEarthing :The CVT has to be firmly connected to earth by fixingsubstation earthing flat to the earthing pads provided ontheEMU tank.The end (N) of high voltage winding of the intermediatevoltage transformer which when brought inside thesecondary terminal box has to be connected to the earthingscrew provided in the terminal box has to be connected tothe earthing screw provided in the terminal box. As

despatched, the LV terminal of the capacitor unit (NHF) isconnected to earthing screw by a cable link.CAUTION : ENSURE FIRM EARTHING OF (N) & (NHF).IFNOT EARTHED FIRMLY THESE LEADS AND OTHERLEADS IN THE TERMINAL BOX WILL ATTAINEXCESSIVE VOLTAGES WHICH WILL LEAD TOPRODUCT FAILURE.One end of the secondary windings can also be earthedinside the terminal box by using the earthing screw.

HV Connection :After confirming the low voltage ratio, connect the HVterminal to the line by terminal connector . While clampingthe terminal connector proper torques should be applied toensure firm connection.

CVT HV TERMINAL BEING OF ALUMINIUM,BIMETALLICSTRIP IS NOT REQUIRED IF AL. TERMINALCONNECTOR IS USED.

Secondary Connection :While connecting the measuring instruments & protectiverelays to the secondary terminals, ensure the burden onrespective secondary winding does not exceed.CAUTION : CVT SECONDARY WINDING SHOULDNEVER BE SHORT CIRCUITED. COMMISSION AND MAINTENANCEThe short circuit connection provided across the capacitorunits has to be removed prior to commissioning. The CVTsdo not require maintenance for a long period of time, owing

to the foolproof hermetic sealing. Checks specified in thechecklist given on page no. 4 are to be strictly followed.OUR CVTS DO NOT REQUIRE ANY ADJUSTMENTS ATSITE FOR MAINTAINING ACCURACY FOR THESPECIFIED BURDENS. CVTS ARE CONSTRUCTED INSUCH A WAY THAT THE REQUIRED ACCURACYCLASSIS MAINTAINED OVER THE ENTIRE BURDEN RANGE.CAUTION :1) NEVER OPEN THE CAPACITOR UNIT AS WELL ASTHE CLAMPING BETWEEN THE EMU AND THECAPACITOR UNIT.2) THE NHF TERMINAL WHEN NOT USED FORCARRIER COMMUNICATION SHOULD BE FIRMLY

CONNECTED TO EARTH.3) THE TERMINAL BOX COVER SHOULD BE CLOSEDUSING NUT & BOLT SO AS TO COMPRESS THE DOORGASKET ADEQUATELY THIS WILL ENSUREWEATHERPROOF SEALING.

Important Checks from Checklista) Secondary Voltage : (item 5) Significant deviation in thesecondary voltage from the rated value indicates that thereis a fault. The product should be taken out of serviceimmediately. Inform CGL for corrective action.b) Varistor : (item 6) Visual inspection of varistor (viz.check for bulging, burning) will indicate healthiness of thevaristor. In case of any abnormality inform CGLimmediately.

c) Oil level Indicator : (item 7) : Since oil inside theindicator is directly exposed to the sunlight, a uniform orspotty brownish sediment can appear on the sight glassafter few years of operation. However the oil should remainclear and become insignificantly darker. Otherwise checktemperature rise of EMU as in d) and check oilcharacteristics as in e) below.d) Temperature Rise of EMU : (item 12) : if any faultdevelops in the EMU, the EMU tank temperature will rise.Insuch cases the temperature shall be measured below thewithin five minutes of taking the shut down. The recordedtemperatures should be informed to CGL.e) Checking of oil in EMU : (item 13) : Owing to the

foolproof hermetic sealing, the ageing of the oil isconsiderably reduced. An oil sample should be taken afterfirst 10 years of service and subsequently every 5 years.Nevertheless the test on oil should be carried out when theoil becomes brownish in colour. The oil in the EMU shouldhave a maximum dissipation factor of 10% at 40 deg. cent.and BDV of 40 kv (min.) For oil sampling procedure for thistest and analysis of the test results contact CGL.


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f) Inspecting the CVT for oil leakages : (item 8) :The CVT should be checked at following places for likely oilleaks.- Below each porcelain flange.- On EMU tank below and above.- On EMU tank at all welded joints.- Around monoblock in the terminal box.g) Check for capacitance : (item 14) : This should beconducted after 10 years of service at a temperaturebetween + 150 0and 30 deg. centigrade The capacitancevalue should not differ significantly from the routine testresults, taking into account the accuracy of the capacitancemeter.IN CASE OF DAMAGES AND FAULTS THE FOLLOWINGSHOULD BE COMMUNICATED TO CGL :a) Customer Siteb) Type designation of the CVTc) S. O. No. and serial number of the CVTd) Date of receipt and the date on which it is noticede) Details of damage and the date on which it is noticed.f) Details of the Low voltage ratio check beforecommissioning and results of other tests recommendedby us

Check listChecks, which should definitely be carried out at specified times..Additional checks, if further information is required, or if considered necessary.

Checking Times : F When EMU oil is dark.E After change of burden or of connections.Before reconnection to high voltage system.D If secondary voltage is doubtfulC Before commissioning after transport of apparatusB After 10 yearsA Routine checking every year.

Check Items : A B C D E F

1. Check of Earthing EMU tank, NHF (L V terminal of capacitor) O O

N (Neutral end of HV winding of Int. VT)

2. Low voltage ratio Check for correctness O

3. Secondary circuits Check if not short circuited O O

4. Connections Check for firmness of connections O O O

Check for corrosion . O

5. Secondary Voltage Check with regard to rated value O O O O

6. Varistor Visual check (Bulging or burning) O O

7. Oil Level Indicator Check if completely filled with oil O O O

Check oil colour

8. Oil leaks Check for oil traces O O9. Terminal Box Check for cleanliness and O O O O

door gasket sealing

10. Porcelain Insulator Check for dust accumulation O O

11. Metal Parts Check for corrosion O

12. Temperature rise Check for tank temperature O

13. Oil in Tank Checks on the oil O O

14. Capacitor Check capacitance) O

A B C D E F


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Fig. No.3


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SAFETY :7.1 Instructions for Disposal of MaterialMaterial used in Instrument Transformers & CondenserBushings to minimize depletion of natural resources :After unpacking of product at site, packing wood & steelto be recycled. Keep wood & steel at dry place to avoidsoil & water pollution.After the useful life of product is over, disassembled the job. Collect oil & oil soaked paper to avoid soil & watercontamination.

The disposal action for various materials is as follows :

For disposal of Hazardous waste, refer to local regulation.

7.2 Instructions for Mitigation ControlIn case of abnormal & emergency conditions during lifecycle of Instrument Transformers & Condenser Bushings tominimize environmental pollution :Storage of packing wood for long duration in humidcondition will cause land pollution. Incinerate / bury

the Infected wood as per local regulation.Rusting of steel used in packing will causecontamination of water & soil. Take action as perlocal regulation. In case of rusting of steelcomponent used in product, clean the rust withsuitable solvent & apply paint to prevent furtherrusting.Ensure masking of insulating surfaces whilepainting.Contact manufacturer & refer localregulations for use of solvent & procedure forpainting.During transportation / storage / operation, if any oilleakage is detected suspected, following actions are

to be taken :If the product is in operation, de-energized &disconnect the suspected product. Clean the product.Find out source & severity of leakage. If leakage is atbolted joint, ensure tightness of bolt. If the leakage isminor on surface, apply sealant to stop the leakage. If

the leakage is major, raise the level of leaking portion toreduce leakage. Avoid spreading of oil. Arrange for oilcollection. Collect the leaked oil, oil soaked soil, oilsoaked cotton waste / wooden dust, etc. Incinerate asper local regulations.Contact manufacturer for further action & beforerecommissioning.In case of fire / explosion of product, immediatelyde-energize the HV circuit, if not already tripped.Extinguish the fire. Take actions as per localregulations. Contact manufacturer for further action.


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7.3 Material safety data sheet (MSDS)Indentification of the substance / preparation & thecompany :Product :“Electrol” uninhibited transformer oil conforming to IEC60296 - 2003Class I and IS335 - 1993Product Grade :Transformer oil type IEC : 60296 - 2003 Class IRaj Petro Specialities Pvt. Ltd.146/2/3 Karad Village, Madhuban Dam Raod,Silvassa 396 230UT OF D & NHComposition : Refined mineral oilTypical Properties :

Physical State @ 25C: Liquid

Kin Viscocity @ 40OC : 9.34 CSTAppearance : Bright & Clear OilDensity @ 20OC : 0.820 Kg/LSolubility in water : NegligibleStorage, Handling and Protective Measures :Stability / ReactivityStable.Hazardous Nature :

Hazardous Nature not required.Storage Container Materials :New steel drums made out of CRCA sheet confirming to IS1783 specification or in bulk, in EP coated steel drums or inSS tanks.Storage Condition :Store in cool, clean, dry place with adequate ventilation.Avoid heat naked flames and strong oxidizing agents.Individual Protective Measure :Skin : Use oil resistant gloves that overalls tominimize skin contact and contamination ofpersonal clothing.Eye : Wear safety glassesRespiratory : Avoid inhalation of mist.When handling drums of this product safety boots or shoesshould be worn.Ventilation :General or local exhaust ventilation should be provided ifoilmists are generated in any event threshold limit value of5mg/m3 for oil mist should not be exceeded.Toxity :Non Toxic in normal conditions.Irritation :Non irritating.Electrol : A transformer oil is manufactured from MineralOils of types shown to be Non-carcinogenic in lifetimeanimal skin painting studies.Electrol : A transformer oil is expected to be of a low order

of acute schematic toxity. In normal use it is not expectedto be associated with irritation of either skin or eyes and itis not expected to be a skin sensitizer. No long term toxiceffects are to be expected.

First Aid Measures :Skin contact : Remove oil soaking clothing. Washaffected parts of the body thoroughly with soap and water,kerosene, gasoline or organic solvents must not be used.Oil soaked clothing, including footwear, must bethoroughly cleaned before being worn again.Eye contact : Hold eyelids open and flush eye with water.Inhalation In the event of dizziness or nausea, removecasualty to fresh air. If symptoms persist obtain medicalattention. If breathing stops give assisted respiration bymouth to mouth or mouth to nose method.Ingestion : Oil products must not be siphoned by mouth.Ingestion is an unlikely even however if it does occur DONOT INDUCE VOMITING. No emergency measures areneeded but if adverse health effects follow, refer formedicalattention.Fire and Explosion :Flash point, PMCC : 156OCAuto-ignition temperature :Expected to be greater than 320OC (ASTM method)Flammability Limits : Petroleum vapours are flammable(explosive) in proportions between approximately 1percent and 10 percent of vapour in air by volume atambient tempreature and pressures. The vapour pressureof this product is expected to be too low ambienttemperatures for the lower explosive limit to be reached.Extinguishing Media :Recommended : Foam, carbon dioxide (Co2), drychemical and extinguishers. Sand or earth may be used toanother small fires.To be avoided : Water jets should not be used sinceproductwill float and spread out on top of water and may re ignite.Action in case of spillage :Absorb a small spillage with sand or earth. Sweep up andcontain absorbent and then remove it to an appropriatefacility for disposal in compliance with local regulations.

Large spillages should be prevented from spreading by theuse of sand or earth. If possible transfer the spilled oil to asalvage tank, otherwise treat as for a small spillage.Disposal of used product and container (whereapplicable)Used oils may contain harmful impurities, which presentrisks to health that are not present when handling the newoil. It is not possible to be more specific since the presenceand absence of harmful impurities is use dependenttherefore ALL use oil should be allowed to contaminate soilor water and should be disposed of in accordance withprevailing regulations, preferably to a recognized collectoror contractor. The competence of the collector or contractorto satisfactorily deal with waste oil should be established

beforehand.This information is based on our knowledge as of and isintended to describe the product for the purposes of healthand safety requirements only. It should be not therefore beconstrued as guaranteeing any specific property of theproduct.


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S.O. No. of the Product…………………..Sr. No. of the Product………………….

IN CASE OF TRANSIT DAMAGES MARK THE LOCATION OF DAMAGE / OIL LEAKAGE ON THIS DRAWINGAND SEND IT TO CGL (ADDRESS IS GIVEN OVERLEAF)


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Crompton Greaves Ltd.,Switchgear Division (S1)A-3, MIDC, Ambad, Nasik - 422 010. India.Tel. : +91 253 2301271, 73Fax : +91 253 2381247Email : [email protected] OfficeCG House, 6th Floor, Dr. Annie Besant Road, Worli, Mumbai- 400 030.Visit us at : www.cgglobal.com

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