Tap Changer Maintenance

On-load tap-changers, type UBBMaintenance guide

1ZSE 5492-127 en, Rev. 5

This document must not be copied without our written permission, and the contents thereof must not be imparted to a third party nor be used for any

unauthorized purpose. Contravention will be prosecuted.

Recommended PracticesABB recommends careful consideration of the following factors for maintenance work on on-load tap-changers:

Before you start any work, make sure that the personnel doing the job have read and fully understood the Maintenance documents provided with the unit.

To avoid damaging the unit, never exceed the operating limits stated in delivery docu-ments and on rating plates.

Do not alter or modify a unit without first consulting ABB.

Follow local and international wiring regulations at all times.

Use only factory authorized replacement parts and procedures.

WARNING, CAUTION and NOTEWARNING

A WARNING provides information which, if disregarded, could cause injury or death.

CAUTIONA CAUTION provides information which, if disregarded, could cause damage to the equipment.

NOTE: A NOTE provides additional information to assist in carrying out the work described.

Safety PrecautionsWARNING

The Maintenance Guide should be read and understood before any work is started, and the procedures in this document should be followed at all times.

WARNINGBefore carrying out work on the on-load tap-changer, put the LOCAL/REMOTE switch in the motor-drive mechanism to position 0. It is also recommended to shut the door of the motor-drive mechanism and pad lock it when work is carried out on the on-load tap-changer. The key should be kept by the operator. This is done to avoid unexpected start of the motor-drive mechanism.

WARNINGBefore starting any work inside the motor-drive mechanism, the auxiliary power must be switched off. N.B. The motor, contactors and heating element may be energized from separate sources.

CAUTIONApproval should be given for inspection as well as for operating the on-load tap-changer.

CAUTIONABB recommends that only maintenance engineers trained by ABB carry out contact replacement.

During ServiceWARNING

Small amounts of explosive gases will always come out from the breathing devices (dehydrating breather or one-way breather). Make sure that no open fire, hot surfaces or sparks occurs in the immediate surroundings of the breathing devices.

WARNINGIf a failure in power supply occurs during operation, the operation will be completed when the power returns.

WARNINGThe hand crank must not be inserted during electrical operation.

WARNINGIf the on-load tap-changer is not in its exact position and the hand crank is pulled out, the motor-drive mechanism will start and go to the exact position if the power supply is on.

CAUTIONAfter a pressure relay trip, follow the instructions in the chapter ”Pressure Relay” in the Repair Guide.

During Oil HandlingWARNING

Unused transformer oil is slightly harmful. Fumes from unused warm oil may irritate the respiratory organs and the eyes. After long and repeated contact with transformer oil skin becomes very dry. Used on-load tap-changer oil from diverter switch housings and selector switch housings contains harmful substances. Fumes are irritating to the respiratory organs and the eyes and are very easily set on fire. Used transformer oil may well be carcinogenic. Avoid contact with the oil as much as possible and use oiltight protective gloves when handling the oil. First aid: Skin contact: Wash the hands. Use skin cream to counteract drying. In the eyes: Rinse the eyes in clean water. Swallowing: Drink water or milk. Avoid vomiting. Call a doctor. Collect used oil in oil drums. Waste and cleaning up: Should be absorbed by an absorber. Treat it as hazardous to the environment. Upon fire: The fire should be extinguished by using powder, foam or carbon acid.

WARNINGWhen oil that has been used in an on-load tap-changer is pumped out, conducting tubes and hoses that are earthed should be used to avoid the risk of explosion due to the gases produced by the arcs during service.

WARNINGThe oil in the on-load tap-changer may be hot. Be cautious!

WARNINGThere is always a cushion of explosive gases in the top of the on-load tap-changer. No open fire, hot surfaces or sparks may be present during opening of the housing or draining from the valve. After the cover is removed let the gas vent away approximately 15 min before any work is started.

WARNINGBe aware of the risk for slipperiness caused by oil spillage for instance when working on the transformer cover.

CAUTIONDo not fill oil into the on-load tap-changer if the transformer tank is under vacuum and the on-load tap-changer is not.

CAUTIONDo not fill oil into the transformer tank if the on-load tap-changer is under vacuum and the transformer tank is not.

CAUTIONLeave a gas cushion on top of the oil in the on-load tap-changer.

After Oil FillingCAUTION

Do not energize the transformer earlier than three hours after oil filling in atmospheric pressure. This waiting period is needed to allow airbubbles to disappear.

Mounting of GasketsCAUTION

Sealing surfaces and gaskets must be clean and undamaged. Diametrically opposed bolts in sealing joints must be tightened alternately several times, beginning with a low tightening torque and finally with the recommended tightening torque as described in section 1.3 Tightening Torque, in this guide.

Contents1 Introduction____________________________________________ 91.1 General________________________________________________ 91.2 MaintenanceSchedule____________________________________ 101.2.1 Inspection______________________________________________ 101.2.2 Overhaul_______________________________________________ 121.2.3 ContactReplacement_____________________________________ 121.3 TighteningTorque_______________________________________ 12

2 Inspection______________________________________________ 132.1 RequiredToolsandMaterial_______________________________ 132.2 Procedure______________________________________________ 132.2.1 CheckingoftheBreather__________________________________ 142.2.2 CheckingoftheOilLevelintheConservator__________________ 142.2.3 CheckingoftheMotorandtheCounter ______________________ 142.2.4 CheckingoftheEmergencyStop ___________________________ 142.2.5 CheckingoftheEarthFaultProtector(Option)_________________ 142.2.6 CheckingoftheHeater ___________________________________ 15

3 Overhaul_______________________________________________ 183.1 RequiredToolsandMaterial_______________________________ 183.2 Procedure______________________________________________ 193.3 Preparations____________________________________________ 203.3.1 On-LoadTap-ChangerPosition_____________________________ 203.3.2 DisconnectionandEarthingoftheTransformer________________ 203.3.3 OilVolumesandLiftingHeights____________________________ 203.3.4 RecommendedSetofStandardSpareParts____________________ 213.4 OilTestingandOilDraining_______________________________ 223.5 LiftingandCleaningtheSelectorSwitchInsert________________ 233.5.1 DismantlingtheTopCoveroftheOn-LoadTap-Changer_________ 233.5.2 RemovaloftheMechanismandFixedContactBlades___________ 243.5.3 AdjustmentoftheHoldingToolforRemovalofFixedContacts___ 263.5.4 PositioningofSelectorSwitchandChange-OverSelector beforeLifting___________________________________________ 273.5.5 Lifting ________________________________________________ 273.5.6 Cleaning_______________________________________________ 283.6 OilFiltration ___________________________________________ 293.7 CheckingoftheBreather _________________________________ 293.8 CheckingContacts_______________________________________ 303.8.1 MovingContacts________________________________________ 303.8.2 FixedContactswithTipsofCopper-Tungsten _________________ 313.8.3 FixedContactsmadeofCopper_____________________________ 323.9 CheckingtheTransitionResistors___________________________ 333.10 LoweringtheSelectorSwitchInsert_________________________ 333.11 MountingtheTopCoverontheOn-LoadTap-Changer__________ 343.12 LubricationoftheOn-LoadTap-Changerandthe DriveShaftSystem ______________________________________ 35

3.13 CheckingthePressureRelay_______________________________ 363.13.1 FunctionalCheckofthePressureRelay ______________________ 363.13.2 ReplacingthePressureRelay ______________________________ 363.14 CheckingofMotor-DriveMechanismstypesBUEandBUL______ 373.14.1 MotorProtection________________________________________ 403.14.2 EarthFaultProtector(option) ______________________________ 403.14.3 Counter________________________________________________ 403.14.4 Heater_________________________________________________ 403.14.5 ToothedBelt____________________________________________ 403.14.6 CableConnections_______________________________________ 413.14.7 DiscBrake,BUE________________________________________ 413.14.8 BrakefortheMaintainingContact,BUE _____________________ 423.14.9 DiscBrake,BUL________________________________________ 423.14.10 PositionTransmitterandotherPositionSwitches,BUE__________ 433.14.11 PositionTransmitterandotherPositionSwitches,BUL__________ 433.14.12 StartingContact,BUE____________________________________ 453.14.13 Lubrication,BUE________________________________________ 453.14.14 Lubrication,BUL________________________________________ 453.15 OperationTest__________________________________________ 473.16 OilFilling______________________________________________ 473.16.1 FillingMethodsandRestrictions____________________________ 473.16.2 BeforeFilling___________________________________________ 483.16.3 FillingatAtmosphericPressure_____________________________ 483.16.4 OilLevel ______________________________________________ 483.16.5 RestoringtheGasCushion ________________________________ 493.16.6 WaitingPeriod__________________________________________ 503.17 PuttingintoOperation____________________________________ 50

4 ContactReplacement_____________________________________ 514.1 MovingContacts________________________________________ 514.2 FixedContacts__________________________________________ 51

5 Tap-changerinthetransformer_____________________________ 525.1 Resistancemeasurement __________________________________ 52

6 SpecificationofMaterials _________________________________ 536.1 General________________________________________________ 536.2 SelectorSwitchHousing__________________________________ 536.3 SelectorSwitchInsert ____________________________________ 536.4 GearingMechanism______________________________________ 536.5 DriveShaftSystems______________________________________ 546.6 Motor-DriveMechanism__________________________________ 54

Appendix,Tools________________________________________________ 55

9

1 Introduction

1 Introduction 1.1 General

TheUBrangeofon-loadtap-changersmanufacturedbyABBhasbeendevelopedtoprovidemaximumreliability.Thesimpleandruggeddesigngivesaservicelifeequaltotheservicelifeofthetransformer.Aminimumofmaintenanceisrequiredfortrouble-freeoperation.Theonlypartsrequiringmaintenancearecontactsthatmightneedreplacementduringtheservicelife,theinsulatingoilandthemotor-drivemecha-nism.

Thedesignallowsexcellentaccesstoallparts,makinginspectionandmaintenancequickandsimple.

Theon-loadtap-changer,typeUBB,ishousedinthetransformertank.Themotor-drivemechanismisattachedtothetransformertankandconnectedtotheon-loadtap-changerbymeansofdriveshaftsandabevelgear,seeFig.1.

TC_00255

Bevel gear

Fig. 1. On-load tap-changer and motor-drive mechanism, type BUL

Horizontal shaft with protection cover

Vertical shaftwith protection cover

Rating plate

Bevel gear

On-load tap-changer Motor-drive mechanism

10

Fig.2showsthegeneralarrangementofaUB-typeon-loadtap-changer.Themaincomponentsaretheselectorswitch(combinedtapselectoranddiverterswitch),thechange-overselector,theselectorswitchhousingandthegearingmechanism.Formaintenancethetopcoverandthegearbaseplate(Fig.4a)areremovedbeforeliftingtheselectorswitchinsert.Thecontactsarethenimmediatelyaccessibleandcanbeinspectedforwear.

Theselectorswitchhousinghasitsownoilseparatedfromthetransformeroil.Thisistopreventcontaminationofthetransformeroilsincetheoiloftheon-loadtap-changerdeterioratesduetotheswitchingoperations.Theoilneedstobechangedatregularintervalstomaintainadequatedielectricstrengthaswellastopreventmechanicalwear.

Theselectorswitchcomprisesthreephases,eachconsistingof:

■ Selectorswitch(withreplaceablefixedandmovingcontacts)

■ Transitionresistors.

Itisnecessarytoinspectandcleanthecontactsandinsulationpartsoftheselectorswitch,aswellastocleanthehousinginsideatregularintervals.

Besidesthemaintenanceoftheselectorswitchandchangingoftheoil,themotor-drivemechanismshouldbecheckedandlubricated.

Thepressure-relay,thedevicethatprotectsthetransformerfromexcessivepressureintheselectorswitchhousing,shouldalsobechecked.

1.2 Maintenance ScheduleMaintenanceoftheon-loadtap-changerconsistsofthreemajorsteps:

■ Inspection

■ Overhaul

■ Contactreplacement

1.2.1 InspectionOntheratingplate,”inspectiononceayear”isrecommended.Thisprincipallyconcernsthemotor-drivemechanismandreferstoavisualinspectioninsidethemotor-drivecabinet,theheaterisfunctioning,etc.

Inthemotor-drivemechanismacounterregisterseverytap-changeoperation.Duringinspectionthecounterisread.Ifpossible,motorandcounteraretestedbyoperatingonestepandthenback.

Iftheon-loadtap-changerhasitsownoilconservator,thebreatherandtheoillevelindicatorarecheckedaccordingtotheinstructionsfromthetransformermanufacturer.

Theinspectioniscarriedoutwhilethetransformerisinservice.

1 Introduction

11

fm_00235

1 Introduction

Bottom

Bottom valvedrain screw

Moving contacts

Fixed contacts

Fixed contacts

Moving contacts

Change-over selector:

Selector switch:

Cylinder

Flange

Bevel gear

Oil valve

Selector switch shaft

Fig. 2. General arrangement of on-load tap-changer, type UB

Transition resistor

Current collectorterminal

Shielding rings

Indicator window

Air release valve to on-load tap-changer

Connection to oilconservator

Pressure relay

Air release valveto transformer tank

Top cover

12

1.2.2 OverhaulThecontactlifeandthefrequencyofoperationsorthetimeinservicedeterminetheintervalbetweenoverhauls.

Thenumberofoperationsrunbytheon-loadtap-changerisrecordedbyacounter,housedinthemotor-drivemechanismcabinet.Theregisterednumberofoperationsshouldbenotedateveryinspectionandoverhaul.

Theon-loadtap-changershouldnormallybeoverhauledregularlyatintervalsof1/5oftheestimatedcontactlife.Therelevantinformationisstatedontheratingplate.Hereby,thecontactwearcanbefollowedandnecessarypreparationscanbemadeforreplacingthecontacts.

Ifthetap-changeoperationsoccurinfrequentlyandaverylongtimeelapsesuntilthenumberofoperationsamountsto1/5ofthecontactlife,theintervalbetweenoverhaulsshouldbelimitedtothetimestatedontheratingplate(normally5years).

Theoverhaulwillnormallytakeatleast8hours,includingthe3hourswaitingperiodafteroilfilling,evenifitismadebytrainedpersonnel.Werecommendthattheover-hauliscarriedoutundersupervisionofaserviceengineertrainedbyABB.

1.2.3 Contact ReplacementOntheratingplateoftheon-loadtap-changertheestimatedcontactlifeofthebrea-kingcontactsintheselectorswitchatratedloadisstated.

Thecontactswillwithstandaverylargenumberofswitchingoperations.Fornormalpowertransformersthenumberofoperationsoftheselectorswitchisapproximately20perday,whichmeansthatreplacementofthecontactsisnotnormallynecessaryduringthelifeofthetransformer.(Incaseofon-loadtap-changersonfurnacetransfor-mers,thefrequencyofoperationsmaybeconsiderablyhigher).

CAUTIONThe number of operations must in no case exceed 500 000, due to weakening spring tension of the contacts.

1.3 Tightening TorqueThefollowingtighteningtorquesarerecommended:

M6, 10Nm ±10% (7.4lbfxft)

M8, 24.5Nm ±10% (18lbfxft)

M10, 49Nm ±10% (36lbfxft)

M12, 84Nm ±10% (62lbfxft)

unlessotherwisestatedinthisguide.

1 Introduction

13

2 Inspection

2 lnspectionTheinspectionconsistsofavisualcheckofthemotor-drivemechanismandtheconservatoronceayearwhilethetransformerisinservice.

Inthemotor-drivemechanismthefollowingpointsaretobechecked:

■ Motorandcounter

■ Heater

■ Thecounter’svalue

Ontheconservatorthefollowingaretobechecked:

■ Oillevel

■ Breather

Iftheon-loadtap-changerisequippedwithanoilfilterunitfromABBitshouldbeinspectedonceayearaccordingtothe”Oil Filter Unit for On-Load Tap-Changer manual”.

2.1 Required ToolsThefollowingequipmentisrequiredfortheinspection:

■ Setofscrewdrivers

■ Penandnotepad

2.2 ProcedureCAUTION

Approval should be given for inspection as well as for operating the on-load tap-changer.

WARNINGThis work must be carried out from ground level since the transformer is ener-gized.

14

2 Inspection

2.2.1 Checking of the BreatherCheckthebreatheraccordingtotheinstructionsforthetransformer.

WARNINGThe breathers and the tube from the conservator contains explosive gases. No open fire, hot surfaces or sparks may be present when removing the breather.

Ifmorethanhalfofthedryingagenthaschangedcolour,itmustbedriedorreplaced.

Thedryingagentnormallystartstochangecolourfromthebottomofthebreather.Ifitchangescolouratthetopofthebreather,thereisaleakageintheconnectionstotheconservator.Locatetheleakageandsealit.

2.2.2 Checking of the Oil Level in the ConservatorTheoillevelintheconservatorshouldbeaccordingtotheinstructionsinthetrans-formerdocumentation.

2.2.3 Checking of the Motor and the CounterOpenthemotor-drivecabinetdoorandturntheselector-switchtotheLOCALposition.ThenturnthecontrolswitchtotheRAISE(LOWER)position.

Checkthatthemotorworksproperly,thepositionindicatorincreases(decreases)onestep,andthecounteradvancesonestepforeachoperation.Recordthecounter’svalue.Thecountershowsthenumberofoperationsrunbytheon-loadtap-changer(theover-haul-schedulecanbedeterminedwiththehelpofthisinformation).

TurnthecontrolswitchtotheLOWER(RAISE)position.Checkthatthemotoralsoworksproperlyinthatdirection,thepositionindicatordecreases(increases)onestepandthecounteradvancesonestepmore.

Resetthedraghands.

2.2.4 Checking of the Emergency StopGiveaRAISEorLOWERimpulseandafteraboutonesecondpresstheemergencystop.Theoperationshouldbeinterrupted.ResettheemergencystopbyturningtheknobclockwiseandsettheprotectivemotorswitchtoON.Thestartedoperationshouldnowbecompleted.Operatebacktoserviceposition.

2.2.5 Checking of the Earth Fault Protector (Option)Ifthemotor-drivemechanismisequippedwithanoutlet,theearthfaultprotectorshouldbetestedbypressingthetestknobontheoutletonBUEorontheseparateearthfaultprotectoronBUL.

15

2.2.6 Checking of the HeaterDisconnecttheincomingauxiliarypower.

WARNINGBefore starting any work inside the motor-drive mechanism the auxiliary power must be switched off. N. B. The motor, contactors and heating element may be energized from separate sources.

Openthecontrolpanel.(BUEonly).

Checkbyfeelingwithafingerontheprotectionplatethattheheaterhasbeenfunctio-ning.

Closethecontrolpanel.(BUEonly).Reconnecttheincomingauxiliarypower.

Completetheinspectionbyturningtheselector-switchtotheREMOTEpositionandclosingthecabinetdoor.

2 Inspection

16

1 2 3 4 5 6 7 8 9 10

21 20 19 18 17

11

12

13

14

15

16

2 Inspection

1. Locking device prepared for padlock2. Emergency stop3. (Option) Switch for extra heater4. Air vent5. LOCAL/REMOTE switch 6. RAISE/LOWER switch7. Outgoing shaft8. Lamp (40 W socket E27)9. Lifting eye10. Counter11. Tap-change in progress indicator12. Position indicator with draghands for max. and

min. position

13. Shaft for handcrank14. Heater 50 W + optional 100 W (behind the

panel)15. (Option) Outlet with earth fault protector16. Terminal blocks (behind the panel)17. Protective motor switch18. (Option) Thermostat or hygrostat for extra

heater 100 W19. Door-operated switch for lamp20. Handcrank21. Descriptions and circuit diagram

Layout of motor-drive mechanism, type BUE

17

17 18 19 20 21 22 23 24

1 2 3 4 5 6

7

8

9

10

11

12

13

14

15

16

2 Inspection

1. Position indicator with draghands for max. and min. position

2. Tap-change in progress indicator (Red = in progress, White = in position)

3. Counter4. Outgoing shaft with multihole coupling half5. Shaft for handcrank6. Lifting eye7. Locking device prepared for padlock8. (Option) Multi position switches9. (Option) Measuring amplifier10. (Option) Switch for extra heater11. (Option) Outlet12. (Option) Earth fault protector (when outlet is

installed)

13. Emergency stop14. RAISE/LOWER switch15. LOCAL/REMOTE switch 16. Protective motor switch17. Air vent18. Door operated switch for lamp19. Terminal blocks20. Hand lamp21. Heater 50 W + optional 100 W22. (Option) Thermostat or hygrostat for extra

heater 100 W23. Descriptions and circuit diagram 24. Handcrank

Layout of motor-drive mechanism, type BUL

18

3 OverhaulTheoverhaulmainlyconsistsofliftingandcleaningoftheselectorswitchinsert,checkingoftheselectorswitchandchange-overselector(ifany),checkingofthetransitionresistors,checkingofcontactsandthemotor-drivemechanism.

WARNINGBefore any work is carried out on the on-load tap-changer:Make sure that the transformer is disconnected and that earthing is properly carried out. Obtain a signed certificate from the engineer in charge.

3.1 Required Tools and MaterialsNecessaryfortheoverhaul,besidescommonhandtools,isthefollowingequipment:

■ Normalsetofopenendwrenches(metric,upto18mm)

■ Normalsetofsockets(metric,upto18mm)

■ Allensocket,5and6mm

■ Ratchetwrenchhandlewithextension

■ Normalsetofscrewdrivers

■ Oiltestequipment(fordielectricstrengthtestingaccordingtoIEC156),

■ Newtransformeroil,volumeaccordingtosection3.3.3.TheoilqualityshouldbeIEC60296-LCSET-30°(formerClassII).Theoilshouldhaveanelectricalwithstandofatleast40kV,measuredina2.5mmgap,accordingtoIEC60156.

■ Cleanandemptydrums(forapproximately200l)

■ Bucket(10l)

■ Rags(non-fuzzying)

■ Brushwithextensibleshaft(forcleaningofcylinderandselectorswitchshaft),seeAppendix,Fig.A1

■ Springbalance(10N)forcheckingofbelttension

■ Megger(500V)

■ Setofsparecontacts

■ Guideforrollers,seeAppendix,Fig.A6

■ Holdingtool(forremountingoffixedcontactbladeandguidingwhenloweringtheinsert),seeAppendix,Fig.A2

■ Screwingtool(forremountingoffixedcontactblade),seeAppendix,Fig.A3

■ Liftingandoperatingtool,seeAppendix,Fig.A4

■ Liftingrig,seeAppendix,Fig.A5

3 Overhaul

19

■ Liftingjack(about40kg,1.6mliftingheight)

■ Protectivegloves,oil-proof

■ Handlamp

■ Ohmmeter(0.5-50Ohm)

■ Slidecalliper

■ Airpumpwithpressuregauge(0-200kPa),connectiontothreadR1/8”male

■ Oilforbearings

■ Grease:GULF-718EPSyntheticgrease,Mobilgrease28,SHELL-AeroShellGrease22orsimilar

■ Watch,withhandforseconds

■ Penandpaperandrevisionprotocol

3.2 ProcedureTheoverhaulprocedureincludesthefollowingpoints:

■ Oildrainingandfiltering

■ Liftingandcleaningtheselectorswitchhousingandinsert

■ Checkingfixedandmovingcontactsoftheselectorswitchandchange-overselector(ifany)

■ Checkingthetransitionresistors

■ Loweringtheselectorswitchinsert

■ Checkingthepressure-relay

■ Lubricationofthedriveshaftsystem

■ Checkingthemotor-drivemechanism

■ Oilfilling

■ Puttingintooperation

3 Overhaul

20

3 Overhaul

3.3 PreparationsNOTE: If the on-load tap-changer is oil filled under atmospheric pressure, a waiting period of three hours is needed before energizing. To save outage time of the trans-former, carry out all work on the on-load tap-changer and the oil filling before the maintenance of the motor-drive mechanism is started.

3.3.1 On-Load Tap-Changer PositionNotethepositionoftheon-loadtap-changertoenablerestartofthetransformerintherighttapposition.

3.3.2 Disconnection and Earthing of the Transformer

WARNINGBefore starting any work in the on-load tap-changer the protective motor switch and the LOCAL/REMOTE switch must be set at 0.


Operatetheon-loadtap-changerbythehandcrankuntiltheMaintenancepositionisreached.

NOTE: The Maintenance position is marked on the rating plate.

3.3.3 Oil Volumes and Lifting HeightsThenecessarynumberofemptydrumsforcollectingandfilteringoftheoilinthediverterswitchhousingshouldbekeptready.Thedrumsmustbecarefullycleanedandfreefromwater.NewoilneededshouldbeIEC60296-LCSET-30°(formerClassII).Theoilshouldhaveanelectricalwithstandofatleast40kV,measuredina2.5mmgap,accordingtoIEC60156.Theoilshouldhaveawatercontentbelow15ppmandhavebeenhandledandstoredaccordingtoIEC60422point10.

Quantity of oil in the on-load tap-changer and lifting height for insert

UBB.N 200/...UBB.N 350/...

Approx. 100 kg (lifting height 1.3 m)

UBB.T 200/...UBB.T 350/...

Approx. 125 kg (lifting height 1.6 m)

NOTE: The volume of the oil conservator is not included.

21

fm_00227

3 Overhaul

Alternatively,theoilmaybereplacedbynewoilandtheusedoilfilteredatsomelateroccasion.Acertainquantityofnewoil,approximately40kg,shouldbekeptreadytoreplacewasteoilandforcleaning.

CAUTIONDo not energize the transformer until oil has been filled as per section 3.18 ”Oil Filling” in this guide.

3.3.4 Recommended Set of Standard Spare PartsItisrecommendedtohaveasetofcontactsfortheselectorswitchavailableattheoverhaul.SeeFig.3.

Socket screw

Locking washer

Fig. 3.

Moving contacts

Fixed contact

22

3.4 Oil Testing and Oil DrainingTheselectorswitchhousingisequippedwithanoilvalveplacedonthetopsection.Forconnectiondimensions,seethedimensiondrawingfortheon-loadtap-changer.

WARNINGThe oil in the on-load tap-changer may be hot. Be cautious!

Takeanoil-samplefromtheoilvalveandcarryoutthedielectricstrengthtestaccor-dingtoIEC60156(betweensphericalcalottes,distance2.5mm).Thistestiscarriedoutfordecidingwhethertheoilcanbefilteredormustbeexchanged.

Thedielectricstrengthoftheoilshouldnotbeallowedtobelessthan30kVinthetestaboveforanon-loadtap-changerinservice.Fornewoilorafterfilteringoftheoldoil,thedielectricstrengthmustbeatleast40kVtobeallowedforfillingthetap-changer.

NOTE: When taking the oil-sample, first drain some oil into a bucket to clean the valve.

NOTE: If the on-load tap-changer is equipped with an oil filter unit for continuous oil filtration from ABB and it is maintained and operated according to our instructions, oil draining and filtering is not needed, provided that the dielectric strength is at least 40 kV measured in a gap according to IEC 60156.

Usethefilteringequipmentorthepumptodrainoilfromtheon-loadtap-changerintocarefullycleanedoildrum.Connectthepumptotheoilvalveanddraintheoilfromtheselectorswitchhousingandtheconservator.(Iftheoilconservatoroftheon-loadtap-changeriscommonwiththeoilconservatorofthetransformertank,closethevalveinthepipeconnectiontotheoilconservatorandopentheoilvalve.Afterawhile,opentheairreleasevalvetotheon-loadtap-changer,seeFig.2.)Pumpuntiltheoilflowstops.Theoillevelwillthenbeabout300mmbelowthecover.Drainingcanbeeffectedquicklyiffilteringequipmentisusedandatthesametimethewholeoilquantitywillbefilteredonce.

WARNINGThere is always a cushion of explosive gases in the top of the on-load tap-changer. No open fire, hot surfaces or sparks may be present during opening of the housing or draining from the valve. After the cover is removed let the gas vent away approximately 15 min before any work is started.

WARNINGWhen oil that has been used in a on-load tap-changer is pumped out, conducting tubes and hoses that are earthed should be used to avoid the risk of explosion due to the gases produced by the arcs during service.

Removethetopcoveroftheselectorswitchhousing.Seesection3.5.1.Putthehosefromthepumpdowntothebottomoftheselectorswitchhousingandpumpouttheremainingoil.

3 Overhaul

23

fm_00012

3.5 Lifting and Cleaning the Selector Switch Insert

3.5.1 Dismantling the Top Cover of the On-Load Tap- ChangerSeeFig.4.

1. Removetheconnectiontotheoilconservatorandpressurerelayandotherconnectionsmade.

2. Loosenthehoseclipsfortheprotectivetubesonthebevelgearsandpushthetubefromthebevelgearsothatthecouplinghalvesforthesquareshaftcanbeseen.

3. Loosentheboltsforthetopcover.

4. Liftthecovercarefullymin100mmstraightupwardsbeforemovingitinhori-zontaldirection.Holdtheshaftsoitnotwillfallwhenthecoverislifted.Takeawaytheshaftandstoreittemporary.Checkthatthedrivingdisconthelowersideofthecoverandthetighteningsurfacenotbecomedamagedwhenstoringthecovertemporary.

3 Overhaul

Driving pin

A

Guiding pin

Top cover

Bevel gear

Indicator window

Fig. 4.

Driving disc

Screw M6

Protective tube Hose clip

Coupling half

Cover

Key in the bevel gear

Earthing symbol

A A

24

fm_00228

3.5.2 Removal of the Mechanism and Fixed Contact BladesLoosenthefourM8-screwsinthecornersofthebaseplateandremovethemecha-nism,seeFig.5.

IfthebaseplateishardfitteditcanbeloosenedbymeansoftwoM10x50(orlonger)screws.Mountthescrewsthroughthetwoclearanceholesintheupperpartoftheselectorswitch,seeFig.5.Tightenthescrewsandthebaseplatewillbepressedupwards.Removethescrewsimmediatelywhenthebaseplatewithselectormecha-nismisremoved.

3 Overhaul

Base plate for selector mechanism

Position selector for the change-over selector

Holes for M10x50 (or longer) screws

The oblong hole of the position selector

Fig. 5

Four M8 Allen screws

25

fm_00242

Fig. 6. UBB in position before removal of the switch insert.

At10-pitch,(thenumberoffixedcontactsinonephaseoftheselectorswitch),removethecontactbladenexttothecurrentcollectorineachphase,seeFig.6,if12-or14-pitchremovingoftwocontactbladesineachphaseisrecommended.

Proceedasfollows:

1. Adjustthecontactholderoftheholdingtool,fortheactualcontact(differentcontactsfor10-,12-,14-pitches).See3.5.3andFig.A2.

2. Attachtheholdingtoolonthecontactbladeintheupperphase.

3. LoosenthetwoM6-screwscompletelyinthecontactbladebyusingthescrewingtool,seeFig.A3.

4. LiftbothtoolsandthecontactbladeandtheM6-screws.Storethebladeandscrewstemporarily.

5. Forthebladesinthelowerphases,repeatthesteps2-4above.

3 Overhaul

Removed fixed contact blade

Current collector knob

Moving contact arm in maintenance position

Change-over contact in position

26

fm_00021(B)

B

3 Overhaul

Fig. 7.

3.5.3 Adjustment of the Holding Tool for Removal of Fixed ContactsSeeFig7.

TheplatespringmustbeadjustedtodimensionBforthefixedcontactsrespectively(seethetablebelow).TurntheadjustingscrewclockwisetoreduceandanticlockwisetoincreasethedimensionB.Iftheadjustingaccordingtoabovenotisenough,bendcarefullytheplatespringtotherightdimension.Useasparecontactbladetochecktheadjustment.

Fixed contact for Dimension B

10-pitches 41 +1/-0

12-pitches 36 +1/-0

14-pitches 31 +1/-0

Screw

Washer

Plate spring

Contact

Adjusting screw

27

3 Overhaul

3.5.4 Positioning of Selector Switch and Change-Over Selector before LiftingSeeFig.6.

1. Attachtheliftingandoperatingtool,seeFig.A4,tothetwoM8-holesontheupperendoftheselectorswitch.

2. Twistthetoolclockwiseuntilthemovingcontactsoftheselectorswitchshafthavereachedthepositionfortheremovedfixedcontactbladesandclosetothecurrentcollectors.SeeFig.6.

3. Placetheslotintheouterarmofthetoolovertherolleronthechangeoverselector.

4. Twistthemovingcontactsofthechange-overselectorbymeansofthearmuntiltheyarebetweentwofixedlongcontacts.

3.5.5 LiftingTheselectorswitchinsert(massapproximately30kg)canbeliftedoutofthecylinderbymeansofaliftingjack.Asaholderfortheliftingjackitisrecommendedtousea”rig”similartotheoneshowninAppendix,Fig.A5.

1. Couplethehookoftheliftingjacktotheliftingandoperatingtoolandlifttheinsertcarefullyuntilthecurrentcollectorsjustleavedtheirknobs.

2. Twisttheshaftsoboththemovingcontactsandthecurrentcollectorsareinthepositionfortheremovedfixedcontactblades,seeFig.8.

3. Liftcarefullyuntiltheselectorswitchinsertiscompletelyremovedfromtheselectorswitchcylinder.

4. Theinsertcanbeputdownontwonon-metallic(wood)supports.

CAUTIONMake sure that there always is clearance between the insert and the fixed contact blades, so no parts will be deformed or damaged.

28

fm_00243

3 Overhaul

Current collector knob

Removed fixed contact blade

Current collector during lifting

Moving contact armduring lifting

Change over contact during lifting

3.5.6 CleaningCleantheselectorswitchinsertasfollows:

1. Removeallcarbondepositsontheoutsidebybrushing.Flushwithcleanoil.

2. Cleantheinsideoftheselectorswitchshaftbyputtinginthebrushfromthebottomandmovingitupanddownduringturning.Flushtheinsidewithcleanoil.

Cleantheselectorswitchcylinder:

1. Removeallcarbondepositswiththebrushmovedupanddownduringturning.Flushwithcleanoil.

2. Removetheremainingoilonthecylinderbottombyusinganon-fuzzyingrag.Pickupragsfromthebottom.

NOTE: If the on-load tap-changer is equipped with an oil filter unit for continuous oil filtration from ABB and it is maintained and operated according to our instructions, the cleaning of the selector switch housing is very easy.

Fig. 8. UBB in position for lifting of the switch insert.

29

3 Overhaul

3.6 Oil FiltrationThedrainedoilshouldbefiltereduntilitiscleanedandhasregainedthehighdielec-tricstrengthrequired.Thebreak-downvalueforpurifiedoilshouldbeatleast40kVmeasuredina2.5mmgapaccordingtoIEC60156.

Tochecktheresultofthefiltering,taketestsampleduringtheoilfiltrationandaftertheoilhasbeenfilledintotheon-loadtap-changer.

NOTE: If the on-load tap-changer is equipped with an oil filter unit for continuous oil filtration from ABB and it is maintained and operated according to our instructions, no further oil filtration should be necessary. Only take a sample and measure the dielectric strength of the oil, see section ”Oil Testing and Oil Draining” in this guide.

3.7 Checking of the BreatherCheckthebreatheraccordingtotheinstructionsforthetransformer.

WARNINGThe breathers and the tube from the conservator contain explosive gases. No open fire, hot surfaces or sparks may be present when removing the breather.

Ifmorethanhalfofthedryingagenthaschangedcolour,itmustbedriedorreplaced.

Thedryingagentnormallystartstochangecolourfromthebottomofthebreather.Ifitchangescolouratthetopofthebreather,thereisaleakageintheconnectionstotheconservator.Locatetheleakageandsealit.

30

fm_00230

3 Overhaul

3.8 Checking Contacts 3.8.1 Moving Contacts

NOTE: If the moving contacts are replaced, also replace any fixed contacts that are considerably worn, in order to minimize the wear of the new moving contacts.

If the on-load tap-changer has only used a few positions during the period of opera-ting, you may replace any worn contacts in these positions with unworn contacts from positions not used.

Replaceamovingcontactwhenthediameterofitscontactrollersislessthanthediametersgiveninthetable1.Measurethediameterofeachrollerhalfwaybetweentherollerends.

Comparethemeasurementsofthemostwornrollerwiththediametersgivenintable1.SeeFig.9.

Fig. 9. Moving contact arm

NOTE: If a contact is replaced, the comparision at the next revision shall start again with the value for Revision 1.

Table 1. Contact minimum dimensions.

Revision (According to recommendations on the rating plate)

Measure d (mm)

1 ≤ 18.5

2 ≤ 18

3 ≤ 17.5

4 ≤ 17

5 ≤ 17

Thebaseforthedimensionsare,atthesameserviceconditionsinthefuture,thecontactsarenotlikelytobewornoutbeforenextoverhaul.

CAUTIONIf the on-load tap-changer has exceeded 500 000 operations, the contacts must be replaced, due to weakening spring tension of the contacts.

Measure the rollerdiameter (d) here

31

6 mma

b

a

A A

fm_00022

3 Overhaul

3.8.2 Fixed Contacts with Tips of Copper-TungstenCheckthedegreeofcontactburningandestablishwhichsideismostworn.Thencheck,onthemostwornsideofthecontact,whichsurface(upperorlowerpart)is least worn.Measurethewearonthissurface6mmuponthetip,accordingtoFig.10.Thecontacthastobeloosenedtomakethemeasurementpossible.

Fig. 10. Measure the wear of the contacts

Replacethecontactifwornbeyondthelimitsstatedintable2.

NOTE: If a contact is replaced, the comparison at next revision shall start again with the value for Revision 1.



b=30 Measure a (mm)

b=24.5Measure a (mm)


1 ≤ 3.5 (3.0) ≤ 3.5 (3.0) ≤ 4.0 (3.5)

2 ≤ 3.5 (3.0) ≤ 3.5 (3.0) ≤ 4.0 (3.5)

3 ≤ 2.5 (2.5) ≤ 2.5 (2.5) ≤ 3.0 (3.0)

4 ≤ 2.0 (1.5) ≤ 2.0 (1.5) ≤ 2.5 (2.0)

5 ≤ 1.5 (1.5) ≤ 1.5 (1.5) ≤ 2.0 (2.0)


Thevalueswithinbracketsapplytosituationsofequalwearofthecontact’supperandlowersurfaces(within±0.5mm).

Asapplicable,reinstalltheoldcontactsorinstallnewones,accordingtoinstructionsinsection4.2FixedContacts.

View A-A Tip of Copper-Tungsten

Least worn surface

Measure the ”a” value at this point

Most worn side

32

fm_00023

AA

b

a

18

a

3 Overhaul

3.8.3 Fixed Contacts made of CopperCheckthedegreeofcontactburningandestablishwhichsideismostworn.Thencheck,onthemostwornsideofthecontact,whichsurface(upperorlowerpart)isleast worn.Measurethewearonthissurface18mmuponthetip,accordingtoFig.11.Thecontacthastobeloosenedtomakethemeasurementpossible.

Replacethecontactifwornbeyondthelimitsstatedintable3.

NOTE: If a contact is replaced, the comparison at next revision shall start again with the value for Revision 1.




b=25Measure a (mm)

b=22Measure a (mm)

1 ≥ 5.5 (6.0) ≥ 5.5 (6.0) ≥ 4.0 (4.5)

2 ≥ 6.0 (6.5) ≥ 6.0 (6.5) ≥ 4.5 (5.0)

3 ≥ 6.5 (7.0) ≥ 6.5 (7.0) ≥ 5.0 (5.5)

4 ≥ 7.0 (7.5) ≥ 7.0 (7.5) ≥ 5.5 (6.0)

5 ≥ 7.5 (8.0) ≥ 7.5 (8.0) ≥ 6.0 (6.5)


Thevalueswithinbracketsapplytosituationsofequalwearofthecontact’supperandlowersurfaces(within±0.5mm).

Asapplicable,reinstalltheoldcontactsorinstallnewones,accordingtoinstructionsinsection4.2FixedContacts.

Fig. 11. Measure the wear of the contacts

View A–A

Most worn side

Least worn surface

33

3.9 Checking the Transition ResistorsConnectoneofthecablesfromtheohmmetertoonetransitioncontactandtheothercabletothemovingmaincontact,inallphasesasdescribedabove,thenmeasuretheresistance.

Measuretheresistanceofeachresistorandcomparewithvaluesgivenontheratingplate.Checkthattheresistorsareundamaged.Thevaluesmaynotdifferbymorethan10percent.

Checkthatthescrewjointsforcontacts,resistorsetc.havenotworkedloose.

3.10 Lowering the Selector Switch InsertSeeFig.8.

1. Checkthatnoforeignobjects,tools,ragsetc.areleftintheselectorswitchhousing.

2. Puttheguidinground-bar,seeFig.A2,carefullyinthecentreholeinthebottomoftheselectorswitchhousing.

NOTE: The total length should be 1200 mm for UBB.N and 1500 mm for UBB.T. See also Fig. A2.

3. Attachtheliftingandoperatingtool,(ifremoved),tothetwoM8holesontheupperendoftheselectorswitch.

4. Attachtheliftingrig,seeFig.A5,ontheflangeoftheselectorswitchhousing.

5. Coupletheliftingjackhooktotheliftingandoperatingtool.

6. Beforelowering,themovingcontactsandthecurrentcollectorsshallbeposi-tionedoverthegapwherethecontactbladesareremovedandthemovingcontactsofchange-overselectorbetweentwolongfixedcontacts.

7. Lowertheinsertcarefullyuntilthecurrentcollectorsarealittlebitabovethecurrentcollectorknobs.

8. Twisttheinsertcarefullytothepositionwiththecurrentcollectorsexactlyabovethecurrentcollectorknobsrespectively.

9. Lowertheinsertcarefullyandcheckthatallthecurrentcollectorshaveenteredtheknobs.Ifnecessarypushthecurrentcollectorswiththescrewingtoolorsimilar.Checkthatthebottompartoftheinsertentersthebearing,ifnotadjustbyliftingit.

10. Removetheliftingjackandliftingrig.

11. Bymeansoftheliftingandoperatingtoolpositionthemovingcontactsofthechange-overselectortothecontactbladesrespectively.SeeFig.6.

NOTE: The position of the roller.

12. Position,bymeansofthesametool,themovingcontactsoftheselectorswitchtothecontactbladesrepresentingtheMaintenanceposition,seeFig.6.

3 Overhaul

34

13. Removetheliftingandoperatingtool.

14. Removetheguidingroundbar.

15. Remountthecontactbladesineachphaseusingthetwotoolsaccordingtosections3.5.2and3.5.3.Tighteningtorque15Nm.

16. Makesurethatthesealingunderneathandontopofthemechanismareinplace,seeFig.12.RemountthemechanismandtightenthefourM8-screwsinthecornersofthebaseplate,seeFig.5.

NOTE: The driving pins in the top of the selector switch shall enter in the correspon-ding holes in the driving mechanism.

NOTE: If it is an on-load tap-changer with change-over device, make sure that the roller on top of the change-over ring is engaged in the slot of the position selector under the gear base plate.

3 Overhaul

Fig. 12. Sealings

35

3.11 Mounting the Top Cover on the On-Load Tap-ChangerSeeFig.4.1. ChecktheO-ringinthegrooveintheflange.Greasetheshaftendsofthebevelgears.

Seesection3.12.2. Beforemountingthetopcovercheckthatthepositionofthedrivingdisconthelower

sideofthecoverisaccordingtoFig.4.Removethecoverofthebevelgearontheon-loadtap-changertopcover.

3. Lowerthetopcoverstraightdowntowardstheflange.Theguidingpinintheflangeshallcleartheholeinthecover.Thehorizontalshaftwiththeprotectivetubeshallberemountedduringthelowering.

Openthecoverofthegearboxonthetopcoveroftheon-loadtap-changer.Checkthatthekeyontheverticalshaftinthebevelgearisfacingtheearthingsymbolontheflangeoftheon-loadtap-changer.SeeFig.4.

CAUTIONThe position of the driving disc must be according to Fig. 4 and the guiding pin must fit in the hole.

4. Checkthatthenumber,readablethroughtheindicatorwindowinthetopcover,isthesameasmaintenancepositionandthatthemotor-drivemechanismhasthesameindi-catedposition.

5. Mounttheboltsforthetopcoverandtighten.6. Ifdriveshaftcouplinghasbeendismantled: Mountthecouplinghalvestothesquareshaftandtheshaftofthebevelgear.Tighten

thescrewslightandcheckthattheshaftnotcanbemovedmorethan2mminaxialdirection(axialplay).TightenthetwoscrewsA,(seeFig.4)firstandthentheothers.

7. Reconnectthepipe-hooksonthetopcovertotheflangesofthepipetotheoilconser-vatorandthepressurerelay.

8. Lubricatethebevelgear,seesection3.12andreassemblethecover.9. Reassembletheprotectivetubeswiththehoseclips.

CAUTIONThe motor-drive mechanism and on-load tap-changer shall have the same indicated tap-position. Check in the indicator window and the motor-drive mechanism.

3.12 Lubrication of the On-Load Tap-Changer and the Drive Shaft SystemThebevelgearsaregreasedatdeliveryandthesametypeofgreaseisusedforthecoup-lingsoftheoutershaftsystem.Foraccesstothecouplings,loosenthehose-clipsandpushtheprotectivetubestogether.Foraccesstothebevelgears,dismountthecovers.

WARNINGThe bevel gear contains moving gears. Be cautious!

WARNINGRotating shafts. Be cautious!

Checkandlubricatewithgreaseifnecessary.RecommendedtypesofgreaseareGULF-718EPSyntheticGrease,Mobilgrease28,Shell-AeroShellGrease22orsimilar.Remountcovers(makesurethegasketsareproperlyinplace).

3 Overhaul

36

TC_00264

3 Overhaul

3.13 Checking the Pressure Relay

3.13.1 Functional Check of the Pressure Relay

Valve handle(in service position)

Information plate

Quick coupling

Test tap (R 1/8”)

Fig. 13. Pressure relay

1. Setthevalvehandletothetestpositionasshownontheinformationplate.

2. Connecttheairpumpandthepressuregaugetothetesttaponthepressurerelay.(ThreadR1/8”).

3. Raisethepressureuntilthepressurerelaytripsthecircuitbreakersofthetransformer.

4. Readthepressureonthemanometerandcheckagainstthepressurestatedontheinformationplate.Max.permitteddeviationis±10%.Ifthedeviationisgreater,thepressurerelayshouldbereplaced.

5. Checkthatthesignaldisappearswhenthepressureisreleased.

6. Afterfinishingthecheck,turnbackthevalvehandletoserviceposition.

3.13.2 Replacing the Pressure RelayIfreplacementofthepressurerelayisnecessary,itiscarriedoutaccordingtotheinstructionin1ZSE 5492-130, Repair Guide for On-Load Tap-Changer, type UB.

37

3 Overhaul

3.14 Checking of Motor-Drive Mechanisms types BUE and BULThemotor-drivemechanismshouldbecheckedandlubricatedatthesametimeastheon-loadtap-changer.

Theoverhaulincludesthefollowingpoints:

Before disconnecting the power supply:

■ Motorprotectionfunction

■ Earthfaultprotector(option)

■ Counterfunction

After disconnecting the power supply:

■ Heaterfunction

■ Toothedbelt

■ Cableconnections

■ Discbrakefunction

■ Positiontransmitterandotherpositionswitches

■ Lubrication

Reconnectthepowersupplyandmakeoperationtestsaccordingtosection3.15.

38

fm_00137

Motor

3 Overhaul

Fig. 14. Motor-drive mechanism, type BUE

Position transmitter

Contact plate

Brake

Roll pin

Supporting shaft

Maintaining contact

Brake disc

Brake block

Brake for maintaining contact

Cam disc

Toothed belt

Arm system

Driving roller

One turn shaft

Geneva wheel

39

fm_00231

3 Overhaul

Fig. 15. Motor-drive mechanism, type BUL

Operation counter

Roller

Notch

Cam disc

Brake arm

Brake disc

Multi-position switches

Limit switch

Bracket

Geneva wheel

(Grease)

(Grease)

Toothed belt

(Grease)

Adjusting screw

Maintaining contact

40

3 Overhaul

3.14.1 Motor ProtectionOpenthemotor-drivecabinetdoorandturntheselector-switchtotheLOCALposition.Thefunctionoftheprotectivemotorswitchischecked.Forthree-phaseACmotors,oneofthephasefusesisremovedandthefunctiontimeoftheprotectivemotorswitchischeckedbyaRAISEorLOWERoperation.Theprotectivemotorswitchshallreleasewithin60secondsatacurrentsettingequaltotheratedcurrentofthemotoratactualvoltage.

WARNINGThe motor power voltage is dangerous.

Iftheprotectivemotorswitchdonottripwithin60seconds,switchoffthepowerandadjustthecurrentsetting.Repeatthetestwhenthemotoriscold.

ProtectivemotorswitchesforDCmotorsandforsingle-phaseACmotorsarenottested.

3.14.2 Earth Fault Protector (option)Ifthemotor-drivemechanismisequippedwithanoutlet,theearthfaultprotectorshouldbetestedbypressingthetestknobontheoutlet.(OnBUL,theearthfaultprotectorisseparatedfromtheoutletandtheknobisontheprotector).

3.14.3 CounterCheckthatthecounterisfunctioningatRAISEandLOWERoperations.Checkthatthepositionindicatorincreases(decreases)onestepandthecounteradvancesonestepforeachoperation.Recordthecounter’svalue.Thecountershowsthenumberofoperationsrunbytheon-loadtap-changer.

3.14.4 Heater

WARNINGBefore starting any work inside the motor-drive mechanism, the auxiliary power must be switched off. N.B. The motor, contactors and heating element may be energized from separate sources.

Checkbyfeelingwithafingerthattheheatingelementhasbeenfunctioning.

3.14.5 Toothed BeltCheckthatthetoothedbeltissufficientlytight.Iftighteningisrequired,adjustthemotorsupport.Thetightnessofthebeltcanbecheckedbyaspringbalanceattachedtothebelthalfwaybetweenthepulleys.Ata10Nloadthebeltshouldyieldabout5mmonBUEandata6Nloadthebeltshouldyieldabout2mmonBUL.

41

fm_00232

3 Overhaul

3.14.6 Cable ConnectionsCheckthatallcableconnectionswithinreacharesecure.

3.14.7 Disc Brake, BUEWipethebrakediscfreefromgrease.

Thekineticenergyinthemotorandthetoothedwheelsshouldbeabsorbedbythebrake,andthemotor-drivemechanismshouldstop,asshowninFig.16,withatole-ranceof±25degreesmeasuredonthebrakedisc(±125degreesmeasuredonthehandcrank),seeFig.16.

Thiscanbeadjustedbytighteningbothofthespringboltsonthebrake.Usingthehandcrank,operatethemotor-drivemechanismuntilthebrakeisfullyopen.Atthispointthelengthofthespringsmustnotbelessthan35mm.Ifthebrakestilldoesnotfunctionwiththatspringlength,oilorgreasehasenteredthebrakelinings,whichwillthenneedcleaning.

Cleanasfollows:

Usingapairoftongs,removetherollpinsthatholdthesupportingshaftsonthebrakeblocks,seeFig.14.Thenremovetheshaftandthebrakeblocks.Cleanthebrakeliningsonthetwobrakeblockswithdegreasingagent.

Whenrefittingthebrake,checkthatthebrakedisciscompletelyfreefromgrease.Adjustthespringforceofthebrakeuntilthemotor-drivemechanismstopswithinthetolerancesgivenabove.

CAUTIONIf the motor-drive still not stops when the brake is adjusted to a spring length of 35 mm when the brake is fully open, please contact ABB for advisory.

Red mark ±25° from mark on brake pad

Brake disc

Red mark

Brake pads

Fig. 16. Brake adjustment, type BUE

Adjusting nuts

42

fm_00225

3 Overhaul

3.14.8 Brake for the Maintaining Contact, BUECheckthatthebrakeforthemaintainingcontactpreventsthearmsystemonthemaintainingcontactshaftfromswingingbeyonditsnormalpositionwhentherolleronthedrivingarmmovesfreefromthecamdisc,seeFig.14.Attheendoftheoperation,contactsforoperationintheoppositedirectionshallnotmovewhenthearmsystemswingsbacktowardsitsnormalposition.

Unpermittedswingingshouldbepreventedbyraisingthebrakingforce,i.e.tighte-ningthespringbolt.

Anadjustedincreasingspringforceonthediscbrakemakesthemaintainingcontactarmswingbackwithadifferentspeed,andthebrakeforthemaintainingcontactmustbeadjusted.

3.14.9 Disc Brake, BULRunthemotor-drivemechanismandcheckthatthecentreofthenotchinthecamdiscstopswithin±2mmfromthecentreoftherolleronthebrakearm,seeFig.17.Ifitdoesnotstopwithinthetolerances,adjustthebreakingforcewiththeadjustingscrewinthelowerendofthebrakearm.Loosenthecontranut.Tighteningthescrew(clock-wise)makesthestopearlierandlooseningthescrew(anticlockwise)makesthestoplater.Tightenthecontranutaftertheadjustment.

Fig. 17. Brake adjustment, type BUL

CAUTIONIf the motor-drive still not stops when the brake is adjusted to min. 15 mm according to Fig. 17 please contact ABB for advisory.

Contra nut

Brake arm

Roller on the brake armin centre of the notchin the cam disc

Cam disc

Brake disc

Adjusting screw

Min 15

43

0.8 ±0.2 mm

fm_00096

A A

fm_00233

3 Overhaul

3.14.10 Position Transmitter and other Position Switches, BUECleanthecontactplatesandarms(Fig.18)fromdustanddirtwithadrycloth.

Checkandadjusttheresilienceofthemovingcontactsinthemulti-positionswitches.Themovingcontactshall,inallpositions,haveaclearancebetweenthenutandthecontactarmof0.6–1.0mm.Adjustmentismadewiththenutsonthecontact.

Fig. 19. Position transmitter, checking

Fig. 18. Contact arm play

3.14.11 Position Transmitter and other Position Switches, BULCheckthecontactfunctioninallpositionsatbothRAISEandLOWERoperations.Noadjustmentofthecontactsshouldbemade.ForreplacementofaPositionSwitchsee1ZSE 5492-130, Repair Guide, On-Load Tap-Changer, type UB.

Ifthereisalotofdust,itcanberemovedfromthecircuitcardsandthetransparentcoverswithavacuumcleaner,withoutdisassemblingthemulti-positionswitch.

Contact arm

View A – A

Moving contact

Contact plate

Contact arm

Geneva wheel

Fixed contact

Contact arm

Transparent cover

Circuit card

44

9 9 9 9 8 7

LOWER POSITION RAISE

9876

54

10 1112

1314

– +

9

fm_00240

fm_00235

3 Overhaul

Fig. 20. Starting contact, BUE

Indicator window

Adjustment nuts

Red mark

Position indicator

Brake disc

Brake pads

45

3 Overhaul

3.14.12 Starting contact, BUECheckthatthecontacttimingiscorrect.Theremustbea100°(±20°)differencebetweenthemaintainingcontactandthestartingcontact.

Placethemotor-driveinitsexactpositionaccordingtoFig.20.Operatemanually24turns.Intheveryfirstbeginningofturn25,themaintainingcontactisreleasedandafter100°(±20°)moreonthehand-crankthestartingcontactshallswitchonagain.Ifthissequenceisnotcorrect,thedrivediscofthestartingcontactneedsadjustment.

3.14.13 Lubrication, BUESeeFig.21.

Thebearingpointsofthebrakeblocksandthelinksshouldbesparinglylubricatedwithoil.(Useoilforbearings.)

Thespurgears,thegenevawheelwiththelimitstop,thecamdiscsandthecambararesparinglylubricatedwiththesametypeofgreaseasfortheshaftsystemwhennecessary.

Otherbearingpointsdonotneedlubrication.

NOTE: Protect the brake disc and the brake linings against lubricants. Wipe off excess lubricant.

Reconnectthepowersupplies.

3.14.14 Lubrication, BULLubricationisnotneededatnormalworkingconditions.Allballbearingshaverubbersealsandarepermanentlygreased.Allcamdiscsandsomegearsaremadeofselflubri-catingmaterial.

Ifneeded,thebevelgearsforthehandcrank,thegenevawheelsandthebevelgearsforthepositionindicatormightbesparinglylubricatedwiththesamegreaseastheshaftsystem.SeeFig.15.

Reconnectthepowersupplies.

46

3 Overhaul

GreaseGrease

Oil

NOTE: The small bevel gear for the position indicator shaft shall be greased.

Grease

Grease

Oil

Fig. 21. Lubrication points, BUE.

Grease

47

3.15 Operation TestTocheckthattheshaftshavebeencorrectlyassembled,themotor-drivemechanismshouldbeplacedintheexactpositionacc.toFig.16or17.Operatethetap-changerwiththehandcrank,countingthenumberofturnsfromtheexactpositionuntilthetap-changeroperates.ThetestisperformedinbothRAISEandLOWERdirections.WithBUL,thetap-changershouldoperateafter11.5±1turnsofthehandcrank.WithBUE,thetap-changershouldoperateafter19±1.5turnsofthehandcrank.Ifnot,oneoftheshaftcouplingsismountedincorrectly.Operatethemotor-drivemechanism,firstonestepmanuallyusingthehandcrank,andthenelectricallytothepositionnexttotheend-position.Thenoperatemanuallytotheend-position.Checkthemechanicalend-stopbytryingtohandcrankbeyondtheend-position.Afteracoupleofturnsyoushouldreachthemechanicalend-stop.Handcrankbacktotheend-position.Whentryingtooperateelectricallybeyondtheend-position,themotorshouldnotstart.Operatethemotor-drivemechanismelectricallytothepositionnexttotheotherend-positionandcarryoutthesameprocedureasabove.ChecktheemergencystopbygivingaRAISEorLOWERimpulseandafteraboutonesecondpresstheemergencystop.Theoperationshouldbeinterrupted.Resettheemer-gencystopbyturningtheknobclockwiseandswitchontheprotectivemotorswitch.Thestartedoperationshouldnowbecompleted.Checktherunning-throughprotectionwiththestep-by-stepfunctiondisabled.ThisisdonebyfirstremovingtheconnectionbetweenterminalsX4:1andX4:2andthenkeeptheRAISE/LOWERswitchengaged.Themotor-drivemechanismshouldstopbeforethefourthoperationiscompleted.Thischeckingmustbedoneatleastfivestepsfromtheendposition.AfterthetestresetthetimerelaybyputtingtheLOCAL/REMOTEswitchto0andthenback.ResettheprotectivemotorswitchtoON.RemounttheconnectionbetweenX4:1andX4:2.Checkthestep-by-steprelaybykeepingtheRAISE/LOWERswitchengagedinRAISE.Theon-loadtap-changershallmakeonlyonestep.RepeatthecheckinLOWER.Checkthefunctionofthepositiontransmitterandothermultipositionswitchesinallpositions.

3.16 Oil Filling 3.16.1 Filling Methods and Restrictions

Oilfillingcanbecarriedoutatatmosphericpressureorundervacuum.Thewallbetweenthediverterswitchhousingandthetransformertankisdesignedtowithstandvacuumononesideandatmosphericpressureontheotherside.Itisnotallowedtohavevacuumononesideandthepressureofanoilcolumnontheotherside.TheoilqualityshouldbeIEC60296-LCSET-30°(formerClassII).Theoilmusthaveanelectricalwithstandofatleast40kV,measuredina2.5mmgap,accordingtoIEC60156.Newoilshouldhaveawatercontentbelow15ppmandhavebeenhandledandstoredaccordingtoIEC60422point10.Aftermaintenanceoilisnormallyfilledatatmosphericpressure.Thisprocedureisdescribedinsection3.16.3.Iffillingistobecarriedoutundervacuum,see1ZSE 5492-118, Installation and Commissioning Guide for UB.

3 Overhaul

48

3 Overhaul

Afteroilfilling,agascushionshouldremainonthetopoftheoilintheselectorswitchhousing.

Theconnectiontotheoilconservatorisdesignedtoautomaticallygiveagascushionwhenfillingatatmosphericpressure.

NOTE: If new oil, especially degassed oil, is filled into the selector switch housing and the number of operations is low, the gas cushion may be dissolved in the oil. The gas cushion should be restored according to section 3.16.5 ”Restoring the Gas Cushion” in this guide.

3.16.2 Before Filling

NOTE: Oil filling may be carried out in different ways depending on what is conve-nient as long as the rules above are fulfilled and the on-load tap-changer is filled with oil to the correct level with a gas cushion on the top. The method below is recom-mended and if it is followed in detail no pressure limits are exceeded and oil levels and gas cushion will be correct.

3.16.3 Filling at Atmospheric PressureSeeFig.2.

1. Closetheairreleasevalve

2. Opentheconservatorvalve,ifany.

3. Dismantlethebreathingdeviceontheconservatorfortheon-loadtap-changer.

4. Pumpoilintotheselectorswitchhousingviatheoilvalve(connectiondimen-sions,seethedimensiondrawingfortheon-loadtap-changer).Continueuntiltheconservatorisfilledtothecorrectlevelattheactualtemperature.

5. Shuttheoilvalveanddisconnectthepump.

6. Remountthebreathingdevice.Makesuretheconnectiontothebreathingdeviceisproperlysealed.

3.16.4 Oil LevelForcorrectoillevelintheoilconservator,seethetransformerdocumentation.

49

3.16.5 Restoring the Gas Cushion


Iftheon-loadtap-changerhasbeenfilledwithdegassedoilandhasaverylowfrequencyofoperation,thegascushionmayhavebeenabsorbedbytheoil.Toavoidfaulttripbythepressurerelay,thegascushionshouldberestored.

Proceedasfollows:

1. Shuttheconservatorvalve.

2. Connectapumptotheoilvalveandstarttosuckoutoil.Opentheairventtotheon-loadtap-changerandletairin.Stopthepumpingafterabout2litresofoilhasbeensuckedoutfromtheon-loadtap-changer.

WARNINGThe oil in the selector switch housing may be hot. Be cautious!

3. Shuttheairventandtheoilvalveanddisconnectthepump.

4. Opentheconservatorvalveandanappropriategascushionwillbeformed.

CAUTIONTo operate the on-load tap-changer with a too small or no gas cushion means a risk for a trip of the pressure relay.

Theprocedureaboveisusedforon-loadtap-changerswithoutoilfilterunitforconti-nuousoilfiltration.Incasetheon-loadtap-changerisequippedwithanoilfilterunitforcontinuousoilfiltrationfromABB,anditisinstalledaccordingtoourrecommen-dations,followtheinstructionsin”OilfilterunitforOn-LoadTap-Changers,manual”forrestoringthegascushion.

CAUTIONAvoid to do the restoring in damp weather since moisture will get into the selector switch housing. If the restoring has to be done in such weather, the incoming air has to be dehydrated.

3 Overhaul

50

3.16.6 Waiting Period

CAUTIONDo not energize the transformer earlier than three hours after oil filling in atmospheric pressure. This waiting period is needed to allow airbubbles to disappear.

3.17 Putting into OperationOperatetheon-loadtap-changertothepositionnotedinsection3.3.1.PuttheLOCAL/REMOTEswitchtoREMOTE.Resetthedraghands.Makesurethatnotoolsorforeignobjectsareleftinthemotor-drivemechanismcabinet.Closethedoor.Makesurethatnothingisleftonthetransformercover.

Signtherevisionprotocolandgiveittotheengineerinchargeandinformthattheon-loadtap-changerisreadyforenergizing.

3 Overhaul

51

fm_00227

B

4.1 Moving ContactsThetwotransitioncontactunitsandthemaincontactunitaredeliveredasassembledsets.Whenchangingthemovingcontactsthewholeunitsshallbereplaced.

Atfirstthetransitionresistorsshallbeloosened,butnotremoved,bylooseningtwobolts(B),seeFig.22.

4 Contact ReplacementCAUTION

ABB recommends that only maintenance engineers with appropriate knowledge about the UBB selector switch carry out contact replacement.

Checkthewearingofthecontactsasdescribedinsection3.8.Replacewornoutcontacts.

Replacingofcontactsisdescribedinthefollowingsections.

Main contact, unit 2

Transition contact, unit 3

Transition contact, unit 1

Fig. 22. Moving contact system design

4 Contact Replacement

C (10 Nm)

B (24.5 Nm)

D (10 Nm)

52

fm_00024

5 Tap-changer in the transformer

Removethecompletetransitioncontactunit1and3byunboltingthefourbolts(C).Themovingmaincontactunit2isremovedbyunboltingthetwobolts(D).

Thenewmaincontactunitandtransitioncontactunitsarethenremounted.Beginwiththemaincontact.ThetransitioncontactunitswillbecorrectlypositionedwhentheguidefortherollersaccordingtoFigs.22andA6isused.Allboltsshouldbetigh-tenedaccordingtoFig.22.Itisnotnecessarytouseatorquewrench.Thetorques(inbrackets)areonlyguidevalues.

Fig. 23. Guide for the rollers

4.2 Fixed ContactsToremovethefixedcontactbladesyouhavetoloosenthetwosocketscrews.Usetheholdingtooltoholdthebladeandscrewsandthescrewingtooltoloosenscrews.

Whenmountingthenewcontactblades,thesocketscrewsshouldbetightenedwithatorqueof15Nm.

5 Tap-changer in the transformer 5.1 Resistance measurement

Ifthereareanyproblemswithtoohighresistanceduringmeasurementofthetrans-former,thetap-changershouldbeoperated10cyclesoverallpositionstocleanthecontacts.

Anothercauseforproblemsatresistancemeasurementmaybetoolowmeasuringcurrent.Werecommendameasuringcurrentofatleast50A.

53

6 Specification of Materials

6 Specification of Materials 6.1 General

Thischapterspecifiesthematerialsusedintheon-loadtap-changer.

Ondisposalofthisproduct,itisrecommendedthatlocalenvironmentalregulationsineachcountryaremet.Forenvironmentalreasons,materialsusedarespecified.

6.2 Selector Switch HousingMaterial Amount

Steel 5 kg

Aluminium 45 kg

Copper and alloys 5 kg

Epoxy resin 30 kg

Epoxy resin 100-125 kg

6.3 Selector Switch InsertMaterial Amount

Steel 5 kg

Aluminium 5 kg


Silver 25-50 g

Tungsten 0-1.5 kg

Epoxy resin 12 kg

Polyphenylene sulfide resin 2 kg

Resistor wire (mainly copper and nickel alloys with lesser amounts of aluminium and manganese)

2 kg

6.4 Gearing MechanismMaterial Amount

Steel 8 kg

Aluminium 2.5 kg


54

6 Specification of Materials

6.5 Drive Shaft SystemsMaterial Amount

Steel 8 kg

Aluminium 2 kg

Brass 2 kg

Polyethylene 2 kg

6.6 Motor-Drive MechanismMaterial BUE

Approx. amountBULApprox. amount

Steel 100–120 kg 55 kg

Aluminium and alloys – 10 kg

Copper and alloys 5–10 kg 5 kg

Silver 10 g 10 g

Plastics:

Chlorsulphonated polyethylene x x

polyamide with MoS2 x

phenol resin laminate x

polyester x x

PVC x x

carbonate plastic x x

Rubbers:

nitrile rubber x x

fluorine rubber x x

CAUTIONMaterials listed in the table above without any specification of amount are included because they may cause pollution problems during de-commissioning, even in the small quantities used.

55

fm_00025

1350

Appendix. Tools

Fig. A1. Brush

Appendix

Brush of bottle-cleaner type

Material: plastic

Catalogue no.: LL 117 016-L

56

fm_00026

Appendix

Fig. A2. Holding tool and guiding round-bar

Catalogue no.: LL 117 016-D

Alternative 2Alternative 1

Holding tool

Guiding round-bars

Handle

1200 for UBB.N

1500 for UBB.T1175

for

UB

B.N

1500

for

UB

B.T

For UBB delivered 2001 and earlier

For UBB delivered 2002 and later

57

fm_00027

1400

Fig. A3. Screwing tool

Appendix

Catalogue no.: LL 117 016-E

58

fm_00020

264

220

Appendix

Fig. A4. Lifting and operating tool

Catalogue no.: LL 117 016-B

59

fm_00028

460

2050

Fig. A5. Lifting rig

Appendix

Catalogue no.: LL 117 016-C

60

fm_00029

14

20

8

20

4.5

20

Fig. A6. Guide for the rollers

12-pitches

Catalogue no.: LL 117 016-G

14-pitches

Catalogue no.: LL 117 016-H

10-pitches

Catalogue no.: LL 117 016-F

Appendix

ABB AB ComponentsSE-771 80 Ludvika, Sweden Phone: +46 240 78 20 00 Fax: +46 240 121 57 E-Mail: [email protected] www.abb.com/electricalcomponents

Contact us

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