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.
04 Asset Management and Maintenance Powering Improvement
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.
Powering Improvement Asset Management and Maintenance 05
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.
Underlying and contributory causes included:
> Afailuretocarryoutamodificationtothetapchangerwhichhadbeenrecommendedsomeyearsbefore.
> Thefailuretounderstandthesignificanceofrepeatedtapchangeralarmsandmalfunctions.
06 Asset Management and Maintenance Powering Improvement
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
Powering Improvement Asset Management and Maintenance 07
ontheSanctionforTest.Therestorationprogrammecontinuedandthebusbarwasenergisedremotelybythecontrolcentre.
Afterthebusbarswereenergised,permissionwasgivenbyControltorestorethe11kVoutgoingfeedersconnectedtothissectionofbusbar.
Shortlyaftertheinstructionwasissuedtherewasaflashoverinoneoftheoutgoingfeedercubicles.
Theon-siteProjectEngineerwascriticallyinjuredduringtheflashoverandsubsequentlydiedfromhisinjuriesthenextday.Investigationsconcludedthattheengineerhadmadedirectcontactwithliveteststicksleftinsertedinthebusbarspoutsatthepanelofoneoftheoutgoing11kVfeeders.Itisnotknownwhathisintentionswereatthatmoment.
33KV INCIDENTInasimilarincidentinvolving33kVswitchgear,atestleadwasleftoncableterminationsandsubsequentlythecoverswerereplacedwiththetestleadstillconnected,resultinginanexplosionandextensivedamagewhenthecircuitwasre-energised.Noonewasinjuredinthiscase.
Direct causes of these incidents:
> Theengineermadecontactwithlivetestplugswhichwereleftinsertedinthebusbarspoutsatthetimetheywerere-energised.
> Thetestleadwasleftinsidethegear.
Underlying and contributory causes included:
> Failuretoremovethetestprodsandtestleads.
> FailuretocheckandconfirmthatthetestplugsandtestleadshadbeenremovedbeforetheSanctionsforTestwerecancelled.
learning points:
> Whereverpossible,re-energisefromthepointatwhichtestingwasdone,anddon’tremovepanelstoenabletestingunlessthereisnootheroption.
08 Asset Management and Maintenance Powering Improvement
> 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.
Powering Improvement Asset Management and Maintenance 09
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.
10 Asset Management and Maintenance Powering Improvement
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.
Powering Improvement Asset Management and Maintenance 11
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.
12 Asset Management and Maintenance Powering Improvement
> 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.
Powering Improvement Asset Management and Maintenance 13
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.
14 Asset Management and Maintenance Powering Improvement
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.
Powering Improvement Asset Management and Maintenance 15
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.
Direct and contributory causes:
> Diggingtooclosetothefault.
> Themethodadoptedwasunsafe.
learning points:
> Don’tadoptanapproachthatwilldefinitelyexcavateontoalivefault,followyourcompanyLVfaultfindingprocedure.
> Ensurestaffwhoexcavateonfaultsaretrainedforthiswork.
CABlES IN CONCRETEAcontractorwasinjuredwhenbreakingoutconcreteaboveanLVcableusingacompressorpowertool.
Theinitialon-siteriskassessmenthadcorrectlyidentifiedthatthepowertoolshouldnotbeusedtobreaktheconcretedirectlyabovethecable,butthiswasnotconveyedtoanewteamthattookoverthejob.
Asthejobprogressed,theconcretebecamethickerandclosertothecable.
16 Asset Management and Maintenance Powering Improvement
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.
Powering Improvement Asset Management and Maintenance 17
Direct and contributory causes:
> 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.
18 Asset Management and Maintenance Powering Improvement
Direct and contributory causes:
> 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.
Powering Improvement Asset Management and Maintenance 19
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.
Direct and contributory causes:
> Failuretofollowuponpoortestresults.
> Failuretomanagerequiredmodificationseffectively.
> Useofnon-standardunapprovedmodifications.
> Failuretocarryoutfullcommissioningchecks.
learning points:
> Don’tmodifyplantandequipmentunlessyouaresureaboutthetechnicaladequacyofwhatyouareproposing.
> Makesurepoortestresultsthatmightwarnoffailureareactedupon.
> Ensuredefectsandmodificationsarerecordedandeffectivelyclosedout.
> Ensurefullcommissioningchecksarecarriedout.
20 Asset Management and Maintenance Powering Improvement
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.
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PARTNERS
EnergyNetworksAssociation(ENA)istheindustrybodyfortheUKelectricitytransmissionanddistributioncompanies.
EnergyUKisthetradeassociationfortheUKelectricitygenerationcompanies.
TRADE UNIONS:
GMBProspectUnisonUnite
GOVERNANCE
PoweringImprovementismanagedanddirectedbyNationalHealthandSafetyAdvisoryCommittee(HESAC)comprisingrepresentativesfromEnergyUKandENAmembercompanies,theindustrytradeunions(GMB,Prospect,UnisonandUnite)andHSE.
ExecutivedecisionsonbehalfofENAmembercompaniesrestwiththeENASHECommitteeandultimatelytheENABoard.
ExecutivedecisionsonbehalfofEnergyUKcompaniesrestwiththeEnergyUKHealthandSafetyForumandultimatelytheEnergyUKBoard.
Forfurtherinformationseewww.poweringimprovement.org