ASSET MANAGEMENT AND MAINTENANCE REVIEW OF PAST …

ASSET MANAGEMENT AND MAINTENANCE

REVIEW OF PAST INCIDENTS

VISIONThe UK Electricity Industry will be a world leader in health and safety performance by 2015.

CONTENTS

ASSET MANAGEMENT AND MAINTENANCE

Introduction 02

Incidentsinvolvingpoles 03

Tapchangerfatality 05

Metalcladswitchgear 06

Theimportanceofreporting 08

TestprodsandHVringmainunits 09

Cablesassumedtobedead 10

Movementofplantcanbefatal 12

Batteriesareimportant 13

Cut-outsandserviceterminations 14

Excavationsaroundcables 15

Plantfailuresinvolvinginjury 16

Defectsandmodifications 18

Overalllessons 20

02 Asset Management and Maintenance Powering Improvement

INTRODUCTION

ThisisaspecialeditionoftheSHEReviewtosupportourPoweringImprovementinitiative.ThisyearthePoweringImprovementthemeissafetyrelatedtoassets.Assetsaresimplytheplant,equipment,cables,lines,polesandtowersthatmakeupournetworks.Thefocusofthisreviewisthereforepastincidents,mostoftheminvolvingtheplantandequipmentinourindustry.

Onceagain,theseincidentsgiveusagreatopportunitytolearnfromthepast,andmoreimportantly,topreventthesamethingshappeningagain.

Thesetypesofincidentstendtobelesscommon,unexpectedandmoreseriouswhentheyoccur,butlikeallincidentstheyarepreventable.Someofyouwillremembertheseincidents.Pleasetakesometimetoremindyourselfoftheimportantlearningpointsandensurethatthemessagesinthisreviewarepassedon,especiallytocolleagueswhomaynotrememberthem.

Youwillnoticethattheoutcomesintheseincidentsvaryconsiderably,somearefatalities,somearenearmisses,someareseriousinjuries.Thishighlightsthefactthatonceanincidenthappens,theseverityoftheoutcomeispurechance.

Thephotographsusedinthisreviewaretypicalexamplesofbothfailedandgoodassets.Theyarenotalwaysphotographsoftheincidentsdescribed.

Thankfullythetypeofincidentslistedinthisreviewarerare,andthefailureratesofourindustry’splantareverylow.Ournetworksaregenerallywelloperatedbyskilledcompetentpeople,withfewfailures.

Theaimofthisreviewistohelptoeliminatefailures.

Pleasepassthisontooneofyourcolleagueswhenyouhavereadit.

Powering Improvement Asset Management and Maintenance 03

INCIDENTS INVOlVING POlES

Wehaveapproximately4millionpolesintheUK.TheyareusedtosupportthemajorityofourHVandLVoverheadlines(OHL).

Alargepolecanweighaquarterofatonne,withatransformerorotherequipmentthiswillbeconsiderablymore.

Themainrisksfrompolesasassetsarewheretheyhavebeenerectedpoorly,orwheretheyhavedecayedinservice.Inthisstatetheyrepresentarealrisktoourpeopleandothersworkingonornearthem,sinceanyactivityonornearthemmaycausethemtocollapse.

POlE FAllS INTO CAR PARK

Inoneincidentan11kVterminalpolewithapoletransformermountedonitfellintoacarparkdamagingeightvehiclesandwritingoneofthemoff.

Thedirectcauseofthecollapsewasfoundtobethatthepolehadnotbeeninstalledtothecorrectdepth.

Fallingpoleshavekilledourindustrycolleaguesinthepast.

Underlying and contributory causes included:

> Inadequateassessmentofthesiteandsoilconditions.

> Failuretoinstalltocorrectdepth,anduseabaulk.

> Poorsupervision,qualitycontrolandauditingoftheinstallationprocess.


learning points:

> Itisimportantthatanyoneinvolvedintheerectionofpolesiscompetenttoassesssiteconditionsandunderstandstheimportanceofgoodinstallation.

> Alwaysinstallpolestothecorrectdepth.

> Robustsupervisionandqualitycontroloftheprocessisneeded.

POlE FAllS PARTIAlly AS CONDUCTORS AND PlANT ARE TAKEN DOWNInanotherincidentateamwasdismantlinganOHLonslopinggroundandremovedtheconductorsontheuphillsideofapolemountedtransformer.Asthetransformerwasbeingremovedfromthepole,thepolestartedtofalldowntheslopeuntilitwasrestrainedbythestaywirewhichcaughtinatree.Twolinesmenwereattachedtothepoleandonewasslightlyinjured.

Oninvestigationitwasfoundthattherewasavoidinthegroundaroundthebaseofthepole,whichwasnotvisiblepriortothework.

Direct and contributory causes:

> Thepolewasnotfirmlysecuredintheground,eitherduetopoorinstallationorsubsequenterosion.

> Theon-siteriskassessmentandsubsequentmethodadopteddidnotidentifythispossiblerisk.

learning points:

> Ifpossible,completeotherworkonapolebeforeremovingconductors.

> Inspectpolescarefullybeforeclimbingthem.

> Ifnecessary,providetemporarysupportforthepole.

> Alwaysensurepolesareinstalledcorrectly,andthatbackfillisproperlyconsolidatedandrammed.

DECAyED POlESTherehavebeenanumberofincidentswherelinesmenhaveclimbeddecayedpoleswhichhavethenfallenwhilethelinesmenwereonthepole.Someofthesehaveresultedinseriousinjuriesorfatalities,bothtolinesmenonthepolesandtootherswhohavebeenhitbythefallingpoles.


Direct and contributory causes have included:

> Failuretotestpolesproperlybeforeclimbingthem.

> Climbingpolesmarkedasdefective.

> Notchangingdefectivepoles.

learning points:

> AssetManagementproceduresneedtoensurethatdecayedpolesareeffectivelyidentified,recordedandremovedinatimelymanner.

> Alwayscheckpolesfirstforanynoticesorsignsindicatingtheyhavebeenmarkedasdefective.Makesureyouunderstandthesystemyourcompanyusesforthis.

> Testeverypolefirstusingthemethodapprovedbyyourcompany.Makesureyouunderstandhowtodothis.

> Donotclimborworkuponasuspectpoleunlessitissupportedinanapprovedmanner.

> Alwaysusethehierarchyofaccessmethodsforworkingatheight.

TAP ChANGER FATAlITy

Afatalincidentoccurredwhenanengineertriedtomanuallyoperateahighvoltagetapchangerandtheunitexploded,killingtheengineer.

Thedirectcauseoftheincidentwasthefailureofthemechanisminthetapchangerleadingtoanelectricalfaultwhichcausedtheoilintheunittoigniteandexplode.


> Afailuretocarryoutamodificationtothetapchangerwhichhadbeenrecommendedsomeyearsbefore.

> Thefailuretounderstandthesignificanceofrepeatedtapchangeralarmsandmalfunctions.


learning points:

> Alarmsanddefectsonplantshouldbedealtwithbystaffwhoaretrainedandexperiencedinthemaintenanceofthattypeofplant.

> Arobustassetmanagementsystemisneededtoensurethatrecommendedmodificationsarerecorded,scheduledandcarriedout.

> Repeatedalarmsshouldbeinterpretedasanindicationthattheremaybeamoreseriousunderlyingproblemwhichneedstobeinvestigated.

> Manualliveoperationoftapchangersshouldbereviewedandriskassessed,withappropriatecontrolsapplied.

> Whereevidenceexiststhattheinternalmechanismsofeitherthedivertororselectoraredamaged,theunitshouldnotbeoperatedlive.

> Ensurethatstaffdealingwithalarmsanddefectsonequipmenthavetheknowledge,skillsandcompetencytodealwiththatequipment.

METAl ClAD SWITChGEAR

Anumberoffatalandseriousincidentshaveinvolvedworkonmetalcladswitchgear.

FAIlURE TO REMOVE TESTING CONNECTIONS

Severalincidentsindifferentcompanieshaveinvolvedtestorearthingconnectionsandtestprods(sometimesknownastestplugs)beingleftinspoutsbymistake,resultinginflashoverswhenthegearwasre-energised,orworsestill,whenstafftriedtoremovethem.

11KV INCIDENTInoneincident11kVbusbarswerebeingextendedtoprovideanadditionaltransformerwayonanindoorswitchboard.

Thesectionofbusbarhadbeenisolatedandearthedviathebussectionoilcircuitbreaker.Itwasalsoearthedbyteststickswithflexibleearthsinanadjacentfeederway.PermitstoWorkhadbeenissuedforthebusbarsection.Oncefittingworkwascomplete,therestorationprogrammewasstarted.PermitstoWorkwerecancelledandaSanctionforTestissuedtopressuretestthebusbarsviateststicksintheadjacentfeederway.

Onsuccessfulcompletionofthepressuretest,theSanctionforTestwascancelled.Theearthappliedusingteststickswasnotreplacedandwasnotedasanexception


ontheSanctionforTest.Therestorationprogrammecontinuedandthebusbarwasenergisedremotelybythecontrolcentre.

Afterthebusbarswereenergised,permissionwasgivenbyControltorestorethe11kVoutgoingfeedersconnectedtothissectionofbusbar.

Shortlyaftertheinstructionwasissuedtherewasaflashoverinoneoftheoutgoingfeedercubicles.

Theon-siteProjectEngineerwascriticallyinjuredduringtheflashoverandsubsequentlydiedfromhisinjuriesthenextday.Investigationsconcludedthattheengineerhadmadedirectcontactwithliveteststicksleftinsertedinthebusbarspoutsatthepanelofoneoftheoutgoing11kVfeeders.Itisnotknownwhathisintentionswereatthatmoment.

33KV INCIDENTInasimilarincidentinvolving33kVswitchgear,atestleadwasleftoncableterminationsandsubsequentlythecoverswerereplacedwiththetestleadstillconnected,resultinginanexplosionandextensivedamagewhenthecircuitwasre-energised.Noonewasinjuredinthiscase.

Direct causes of these incidents:

> Theengineermadecontactwithlivetestplugswhichwereleftinsertedinthebusbarspoutsatthetimetheywerere-energised.

> Thetestleadwasleftinsidethegear.


> Failuretoremovethetestprodsandtestleads.

> FailuretocheckandconfirmthatthetestplugsandtestleadshadbeenremovedbeforetheSanctionsforTestwerecancelled.

learning points:

> Whereverpossible,re-energisefromthepointatwhichtestingwasdone,anddon’tremovepanelstoenabletestingunlessthereisnootheroption.


> Alwayscheckthattestplugs,toolsandanyotheritemshavebeenremovedfrombusbarandcircuitspoutsthatwereundertestandthatthespoutshavebeenlockedshutbeforetheSanctionforTestiscancelled.

> ItisimportanttoremainfocussedthroughoutallswitchingandHVtestingactivities.Avoiddistractions,excludethosenotinvolved,anduseachecklistifnecessarytohelpcorrectrestoration.

> Nevertouchortrytoremovetestplugsorconnectionsfrombusbarorcircuitspoutsifthecircuitconcernedisnotsubjecttoasafetydocumentwhichallowsyoutodoso.

ThE IMPORTANCE OF REPORTING

SIGNS OF DAMAGE, VANDAlISM AND TRESPASSTwosmallboystrespassedintoasubstationandwerekilledwhen11kVswitchgearfaultedwhiletheywereplayinginthesubstation.

Thefaultoccurredonabusbarjointchamberwhichjoinedthebusbarsoftwoitemsofswitchgearinthesubstation.

Theinvestigationconcludedthattheequipmenthadprobablybeendamagedbyapreviouseventwhichhadleftthecoverfractured,allowingtheingressofmoisture.

learning points:

> Reportingdamagetoequipmentbeforeitfaultscansavelives.

> Oncedefectsordamagearereported,theymustbeappropriatelyprioritisedandrectifiedinareasonabletimescale.

> Alwayscheckforandreportanysignsofdamage,trespassandvandalism.

> Ifapredominantlyundergroundcircuittripsbutnofaultisfound,giveconsiderationtofurtherinspectionofsitesonthecircuit.

> UsetheENAbookletonsubstationsecurityoryourcompany’sownguidanceonsubstationsecurity.


TEST PRODS AND hV RING MAIN UNITS

SomeoftheworstincidentstheindustryhasexperiencedhaveinvolvedproblemswiththetestprodsusedtotestcablesconnectedtoHVRingMainUnits(sometimesknownastestplugs).

Background:

Theseincidentscanbeveryseverebecausetheinsulatingoilcanbeignitedbyanyflashover,leadingtoafireball.Theseprodsaredesignedtobeusedsafelyintankswhichmayhaveliveconductorsinthem.Theyrelyonacorrectfittoguidethem,socorrectuseoftherightprods,ingoodcondition,iscritical.

FATAlITIES DUE TO GUIDE ROD FAllING FROM TEST PRODSTwoengineerswerekilledandafitterwasseriouslyinjuredwhenametalguiderodbecamedetachedfromasetoftestprodsonaReyrolleROKSSringmainunitandfellontotheliveHVmetalworkatthebottomofthetank,causingaflashoverandexplosionwhichignitedtheoil.

SERIOUS INjURy DUE TO USE OF WRONG PRODSInaseparateincident,anengineerusedthewrongsetoftestprodstomaketestconnections.Becausetheywerethewrongtestprodstheywerenotguidedwhentheyenteredthetankandtheymadecontactwiththelivebusbarbushingontheothersideofthetank.Thisresultedinseriousburnstotheengineer.


learning points:

> Alltestprodsmustbesubjecttoarobustsystemofinspection,identification,andlabelling.

> Theymustbekeptindryandsecurestorage.

> Theymustbeprotectedfromdamagewhentransported,ideallyinabox.

> Testprodsmusthavenoremoveableparts.

> Staffmusthavetrainingintheuseandcareoftestprods,includingawarenessofthehazardsinvolved.

> Testprodsmustbeclearlyidentifiedandmarkedwiththetypeofswitchgearonwhichtheyaretobeused,ifthereisanydoubt,donotusethem.

> Neverattempttomodifyordismantletestprodsduringuse.

> Considertestingfromalocationthatdoesnotinvolvetestprods.

> Inspecttestplugseverytimebeforeuse,neverusetestplugsthatareinapoorconditionorwithanypartsthatareloose.

CABlES ASSUMED TO BE DEAD

Arepeatedcauseofinjurieshasbeentheassumptionbystaffthatcablesaredead.

ENGINEER KIllED AFTER TOUChING hV CABlE WITh SEVERE DAMAGE InoneincidentanHVcablewasseverelydamagedbyamechanicalexcavator,leavingthecablewithaseveredendpointingupwardswiththecoressplayedapart.Twoengineersattendedthesiteandbecausethedamagetothecablewassosevere,theyassumedthecablemustbedead.Itwasnot.Oneoftheengineerswasfatallyinjuredwhenheapproachedthedamagedend.


jOINTER BADly BURNT AFTER ASSUMING A CAPPED lV CABlE WAS DEAD

AjointerwascarryingoutsomeLVmainsjointinginanewhousingdevelopment.Itwasnotclearfromhisworkinstructionwhetherthecablesinvolvedwerelive,butbecauseoneofthemhadacappedend,heassumeditmustbedead.Hedidnottestthecableanddidnotworkusinglivetechniques.Aflashoveroccurred,andthejointersufferedseriousburnstohishandsandlegs.

ENGINEER BURNT AFTER CUTTING lV CABlE ASSUMED TO BE DEADAnengineersufferedburnsafterhecutanLVcableheassumedtobedead.ThecablewasoneoftwoLVcableswhichappearedtoberunningparalleltogetherthroughtwoexcavationswithashortlengthofbothcablesbeingburiedbetweenthetwoexcavations.Onecablewasproveddeadandtheengineerassumedthetwocablesmaintainedthesamepositionsinbothexcavations,buttheycrossedinthegroundthathadbeenleftunexcavated.

Cause:

Thecauseineverycaseherewasthefailuretoidentifyandprovethecablewasdead.

learning points:

> NeverassumeanyHVorLVcableisdeadunlessyouhaveproveditdeadbyanapprovedmethod.

> Asimplecappedendcansometimesbeenergisedwithoutfaulting.

> Itisimpossibletoassesswhetheracableisdeadbylookingatit.

> AlwaysuseliveworkingtechniqueswhenworkingatLVifaliveworkingtechniqueexistsforthattask.

> Neverenergiseacappedend.

> Ensuretaskinstructionsclearlyexplainthestatusofcablesonaproject.


> Neveruserelativepositionofcables,ducts,etcasameansofpositivelyidentifyingacable.

> Theonlysafewayofphysicallytracingacablefromapointofworktoanearth(orotherpointatwhichithasalreadybeenproveddead)isifyoucouldpullarunningnoosealongthecablecontinuouslyoverthewholeroute,withoutanyinterruption.

> Ensurechangesarerecordedoncablerecordsandnetworkdiagramsinatimelymanner.

MOVEMENT OF PlANT CAN BE FATAl

Therehavebeenmanyincidentsinvolvingthemovementofheavyplant,someofthesehaveresultedinfatalitiesorseriousinjuries.

TRANSFORMER TOPPlES TRAPPING MEMBER OF STAFF AGAINST WAllAgroundmountedtransformertoppledwhilstbeingmoved.Onecornerofthetransformerwasleftunsupportedwhileanothercornerwasjackedup.


Luckilythepersoninquestionreceivedonlyminorinjuries.Similarincidentsinthepasthaveresultedinthedeathofthoseinvolved.

Direct cause:

> Failuretosupporttheplantfullyduringthemove.

learning points:

> Trytoavoidsubstationlocationsthatmaketheinstallationofplantdifficult.Ifpossibleeliminateordesignouttheriskatthepurchaseandworkplanningstages.

> Movingheavyplantmustbeplanned.Ifitinvolveslifting,thisisalegalrequirement.

> Appointonepersontoleadthemove.

> Usemechanicalplantandaidsforliftingwherepossible.

> Ensurethatadequatenumbersoftheteaminvolvedhavetrainingandexperienceinthemovementofheavyplant.

> Whereverpossibleavoidplacingpeopleunderplantbeingliftedandinlocationswhereplantmightfallover.

> Keepplantlevelandwellsupportedwhilstbeingmoved.

BATTERIES ARE IMPORTANT

Werelyonbatteriestooperatemanyofourprotectiverelaysandalsototripmanyofourcircuitbreakers.Anumberofincidentshavehighlightedtheimportanceofmaintainingandcheckingbatteriescorrectly.

Failuretodisconnectfaultsquicklycanleadtoincreaseddamageandrisktopeopleandplant,aswellasmoreextensivelossesofsupply.

COMPlETE BATTERy STOlEN

Allthecellsfromanumberofprimarysubstationbatterieswerestolen,butthiswasnotnoticedimmediatelybecausethebatterychargerwasconnectedacrossthebatteryterminals.


FAUlTy BATTERy CEllS lEAD TO FAIlURE OF BATTERyWhenan11kVfeedercircuitbreakerfailedtotripforacablefault,twomembersofthepublicwereslightlyinjured.Thelongclearancetimeinvolvedforthebackupprotectiontooperateledtomoreenergybeingreleasedatthepointoffault.

Itwassubsequentlydiscoveredthatanumberofcellsinthebatterywerefaulty,andthebatterywasunabletoprovideadequatecurrenttotripthecircuitbreaker.

Thedefectwasnotpickedupbyaroutinebatterycheckcarriedoutusingapushbuttontest.

Direct and indirect causes:

> Theftofbatteries.

> Inadequatecheckingandmonitoringproceduresandtechniques.

learning points:

> Weallneedtobevigilantforsignsofintrusionandtheft.

> Effectivecontrolofaccesstosubstationsandkeysmustbeensured.

> Thedesignandmaintenanceprocessesshouldensurethattheroutineinspectionandtestingofbatteriesreliablyindicatescellandbatterycondition.

> Arobustregimeofbatterytestingandmonitoringshouldbeimplemented.

CUT-OUTS AND SERVICE TERMINATIONS

Thisequipmentisimportantbecauseitisonourcustomers’premises.Overtheyearstherehavebeenanumberofseriousincidents,someoftheissueshavebeen:

> Damageorinterference.

> Crosspolarity.

> Overheatingofconnections.

> Oldordamagedequipmentnolongerfitforpurpose.


learning points:

> Alwayscheckserviceterminationequipmentwhenvisitingcustomers’intakepositions.

> Reportanydamage,interference,defectsorsubstandardequipmentfound.

> Followyourcompanyprocedureforcheckingpolaritywheninstalling,replacingorrepairingterminationequipmentandconnectionstocustomers.

ExCAVATIONS AROUND CABlES

ExCAVATOR SUFFERS BURNS WhEN DIGGING ON lV FAUlTDuringLVfaultlocation,theteamdugaholeattheservicejointofthelastcustomerstillonsupply,theytestedthecableandfounditwasstillliveatthatpoint.

Theythendugaholeattheservicejointofthefirstcustomeroffsupplyandfoundthecabletobedead.

Theythenproceededtoexcavatealongthecabletowardsthefirsthole.

Thecablewasinaductandwhentheyreachedasectionwheretheductwasfoundtobebroken,aflashoveroccurred.


> Diggingtooclosetothefault.

> Themethodadoptedwasunsafe.

learning points:

> Don’tadoptanapproachthatwilldefinitelyexcavateontoalivefault,followyourcompanyLVfaultfindingprocedure.

> Ensurestaffwhoexcavateonfaultsaretrainedforthiswork.

CABlES IN CONCRETEAcontractorwasinjuredwhenbreakingoutconcreteaboveanLVcableusingacompressorpowertool.

Theinitialon-siteriskassessmenthadcorrectlyidentifiedthatthepowertoolshouldnotbeusedtobreaktheconcretedirectlyabovethecable,butthiswasnotconveyedtoanewteamthattookoverthejob.

Asthejobprogressed,theconcretebecamethickerandclosertothecable.


learning points:

> Powertoolsshouldneverbeuseddirectlyaboveacable.

> Ifthecableiscompletelyembeddedinhardconcreteitshouldbemadedead.

PlANT FAIlURES INVOlVING INjURy

FAIlURE OF ISOlATOR lEADS TO FATAlITy

AlinesmanwaselectrocutedwhilstinstallingasetofOHLisolatorsunderaPermittoWork.

Theisolatorswerebeinginstalledonasectionofnetworkwiththreehighvoltagepointsofisolation.TheonlyCircuitMainEarthbeingappliedviaaportableOHLearth.

Agroundmountedearthingswitchwasavailablebutthiswassubjecttoanoperationalrestriction.

OneofthepointsofisolationwasasetofOHLisolatorswhichhadfailedtooperatecorrectly,andonlytwooutofthreephaseshadopened.TheSeniorAuthorisedPersondidnotconfirmthatallthreephaseshadopenedduetotheisolatorpolebeingcoveredwithvegetation.Anautore-closerhadoperatedduringtheopeningoftheseisolatorsbutthiswasdismissedbythecontrolengineerasaspuriousoperation.

FollowingtheissueofthePermittoWork,andsomehourslater,thecontrolengineerclosedtheautore-closer,believinghewasenergisinguptotheopenisolatorsonly.Thisresultedinonephaseofthesectionofnetworkcoveredbythepermittoworkbeingenergised.

TheOHLportableearthwasineffectiveandthelinesmanatworkwaselectrocuted.



> Failureoftheisolator.

> Failuretoconfirmoperationoftheisolator.

> Poorvegetationmanagement.

> Failuretorectifythedefectontheearthswitch.

> Wrongassessmentofreasonforprotectivedeviceoperation.

> Poorapplicationofmanualearth.

learning points:

> Wherepossiblealwayscheckvisuallytoconfirmthatisolatorshaveoperatedfully.

> WhereverpossibleapplyCMEsviaearthswitches.

> Whenusingportableearths,ensurethattheyareappliedeffectivelyinaccordancewithyourcompanyprocedures.

> Alwaysfollowoperationalprocedures.

> Investigateanyoperationofprotectivedevicesthatcoincideswithactivityonthenetwork.

FAIlURES OF TEST CONNECTIONS ON lV BOARDSAnengineerwasusingun-fusedtestleadstomeasurevoltagebypluggingintothe4mmun-fusedtestsocketsonanLVBoard.

Aflashoveroccurredandtheengineerreceivedburnstohishands.ItisbelievedthattheinsulatedbodyofthetestsocketfailedandtheconductingpartofthebrokensocketmadecontactwiththeearthedmetaloftheLVBoard.

Similarfailureshadoccurredpreviouslyandinothercompanies.Amodificationhadbeenrecommendedtopreventtheproblem.

Otherincidentshadalsoinvolvedtestleadswithterminationsthatwerenot4mmplugsbeingforcedintothesockets.



> Poordesign.

> Useofwrongplugs.

> Lackofcarewhenusingsockets.

learning points:

> Alwaysusetestleadswithfuseswhentakingmeasurementsonliveequipment.

> Knowndefectsshouldbeeffectivelyfolloweduppromptlytoavoidsimilarincidentsonthesametypeofequipmentorplant.

> ConsiderreportinganydefectstotheENANEDERsschemethroughyourcompanycontact.

> Considerbanningtheuseofcomponentsthathaveagenericfaultwhichcanleadtodangerousincidents.

DEFECTS AND MODIFICATIONS

VT FAIlUREAvoltagetransformer(VT)failedcatastrophically.Theporcelainbushingexplodedresultinginfireandejectionofdebrisovera30-metreradius.Thisresultedinseveredamagetoanadjacentcircuitbreaker,currenttransformers,busbarsupportsanddisconnectingequipmentwithintheassociatedequipmentbay.

Asaresult,staffwereputatriskofinjuryandsome81,000customershadtheirelectricitysuppliesinterrupted.

Thesubsequentinvestigationdeterminedthatthecatastrophicfailurehadbeencausedbyaflashoverinthecondensercoreofthevoltagetransformer,duetomoistureingress.Thisfailuremodewasaknownfailuremode,andthisparticularvoltagetransformerhadexhibitedhighreadingsduringpreviouslossangletests.Thesetestswerenotfollowedupon.


33 KV CIRCUIT BREAKER FAIlURE

Afaultoccurredona33kVcircuitbutthecircuitbreakerfailedtotrip,andthefaultwasthenclearedbythe33kVStand-ByEarthfaultprotectiononthetransformerincomers.Thisledtothelossofsupplytoall30,000customersfedfromthe33kVsubstation.

Theguiderodrunningthroughthecentreofthetripcoilspringhadbecomedetachedandthuspreventedthecircuitbreakerfromtripping.

Thisfailuremodewasknown,andadecisionwastakenthattheissuecouldbedealtwithduringmaintenance,butthemaintenanceprocedureswerenotupdatedaccordingly.

FAIlURE OF MODIFIED 33KV SWITCh RESUlTS IN lOSS OF SUPPlyAfaultontheyellowphaseofa33kVswitchatanoutdoorsubstationresultedinthelossofthewholesite.Thesitewasfedbytwoinfeedsbutonewasoutformaintenanceatthetime.51,000customerswereleftwithoutsupply.

Thesubsequentinvestigationdeterminedthatthefaultedswitchgearhadbeenmodifiedincorrectly,inanattempttoincreasenominalratingfrom800Ato1200A.Theredandbluephaseswitchunitshadbeenreplacedwithswitchunitsratedat1200A.buttheyellowphaseunitwasmodified;additionalflexibleleadswereadded,andwereconnectedbyboltedlugsontoaconnectionnotdesignedforthisrating.Thisconnectioneventuallyburnedout.

11KV OIl FIllED RING MAIN UNIT FOUND IN SERVICE WITh NO INSUlATING OIl

Duringroutinemaintenancean11kVoilfilledringmainunitwasfoundinservicewithnooilintheringswitches.

Thiswasprobablyduetothepracticeoftransportingringmainunitswithoutoilintheswitches.


> Failuretofollowuponpoortestresults.

> Failuretomanagerequiredmodificationseffectively.

> Useofnon-standardunapprovedmodifications.

> Failuretocarryoutfullcommissioningchecks.

learning points:

> Don’tmodifyplantandequipmentunlessyouaresureaboutthetechnicaladequacyofwhatyouareproposing.

> Makesurepoortestresultsthatmightwarnoffailureareactedupon.

> Ensuredefectsandmodificationsarerecordedandeffectivelyclosedout.

> Ensurefullcommissioningchecksarecarriedout.


OVERAll lESSONS

Theincidentsinthisreviewshowthatfailuretogetitrightatanystageinthelifeofanassetcanleadtoinjuryorworse.Keyissuesinclude:

> Goodassetmanagementstartsattheplanninganddesignstageofaprojectorprogramme.Hugeamountsofriskcanberemovedorreducedatthisstage.

> Selecttherightequipment,whichissuitableforthepurposeintended.

> Installitcorrectly,carryoutallnecessarytesting,commissioningandrecording.

> Operateitcorrectly,useitforwhatitwasintendedfor,useitwithinitsrating.

> Inspectitcarefullyandensurewarningindicatorsareactedupon.

> Followmaintenanceprocedures.

> Don’tmodifyequipmentunlessyouknowwhatyouaredoing.Allmodificationsmustbeapprovedbytechnicallycompetentstaff.

> Ensurerobustproceduresareimplementedforreportingdefects.Programmemodificationsanddefectstoensuretheirtimelycompletion,monitorprogresstoensurerisksarekeptlow.

> Alwaysfollowthesafetyrulesandyourcompanyprocedures.

> WhereappropriatesharedetailswithothercompaniesthroughtheENA.

Ifyouareinvolvedwithanyofthesestages,makesureyouarefamiliarwiththerequirements,ifindoubt,ASK.Ifyourteamisresponsibleforanyofthesetasks,makesuretheyhavetherighttraining,experienceandtechnicalknowledge.

FINAlly... KEEP CAlM AND CARRy ON!Readingthisreviewyoumightthinkournetworksandassetsareverydangerous.

Thisisnotthecase.Theincidentsdescribedhaveoccurredovermanyyears.

Thankfullythetypeofincidentslistedinthisreviewarerare,andthefailureratesofourindustry’splantareverylow.Ournetworksaregenerallywelloperatedbyskilledcompetentpeople,withfewfailures.

Theaimofthisreviewistohelptoeliminatefailures.

ThisdocumentisprintedonChallengerOffset,apapercontaining100%EnvironmentalChlorineFree(ECF)virginfibresourcedfromwell-managed,responsible,FSC®certifiedforests.

PrintedbyParkCommunicationsonFSC®certifiedpaper.

Designedbywww.treble-design.co.uk

PARTNERS

EnergyNetworksAssociation(ENA)istheindustrybodyfortheUKelectricitytransmissionanddistributioncompanies.

EnergyUKisthetradeassociationfortheUKelectricitygenerationcompanies.

TRADE UNIONS:

GMBProspectUnisonUnite

GOVERNANCE

PoweringImprovementismanagedanddirectedbyNationalHealthandSafetyAdvisoryCommittee(HESAC)comprisingrepresentativesfromEnergyUKandENAmembercompanies,theindustrytradeunions(GMB,Prospect,UnisonandUnite)andHSE.

ExecutivedecisionsonbehalfofENAmembercompaniesrestwiththeENASHECommitteeandultimatelytheENABoard.

ExecutivedecisionsonbehalfofEnergyUKcompaniesrestwiththeEnergyUKHealthandSafetyForumandultimatelytheEnergyUKBoard.

Forfurtherinformationseewww.poweringimprovement.org

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