Export Cable Reliability Description of Concerns … Cable Reliability – Description of Concerns 2 DISCLAIMER This report has been written by Transmission Excellence Ltd on behalf

ExportCableReliability

DescriptionofConcerns

May2017

ExportCableReliability–DescriptionofConcerns

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DISCLAIMER

ThisreporthasbeenwrittenbyTransmissionExcellenceLtdonbehalfoftheOffshoreWindProgrammeBoard(OWPB),withtheassistanceofanad-hocgroup(the“ExportCableReliabilityProject”)thatincludesrepresentativeofmostoftheUK’soffshorewindfarmdevelopersandallofthecompaniesthatowntheUK’soffshorewindexportcables(theoffshoretransmissionowners,orOFTOs).Whilsttheinformationcontainedinthisreporthasbeenpreparedandcollatedingoodfaith,theOWPBandtheauthorsmakenorepresentationorwarranty(expressorimplied)astotheaccuracyorcompletenessoftheinformationcontainedinthisreport(includinganyenclosuresandattachments)norshalltheybeliableforanylossordamage,whetherdirectorconsequential,arisingfromrelianceonthisreportbyanyperson.Inparticular,butwithoutlimitation,theOWPBandtheauthorsacceptnoresponsibilityfortheaccuracyandcompletenessofanycommentson,oropinionsregardingthefunctionalandtechnicalcapabilitiesofanyequipment,softwareorotherproductsmentionedinthereport.TheOWPBandtheauthorsarenotresponsibleinanywayinconnectionwitherroneousinformationordatacontainedorreferredtointhisdocument.Itisuptothosewhousetheinformationinthisreporttosatisfythemselvesastoitsaccuracy.Thisreportanditscontentsdonotconstituteprofessionaladvice.Specificadviceshouldbesoughtaboutyourspecificcircumstances.Thereporthasbeenproducedbytheauthorsbasedoninformationprovidedbyindustryparticipantsandhasnotbeensubjecttoindependentverification.TheOWPBandtheauthorsacceptnoresponsibilityfortheaccuracyandcompletenessofanycommentson,oropinionsregardingthefunctionalandtechnicalcapabilitiesof,anyproductsorservicesmentioned.Thereportisnotintendedtobeinstructional,ortorequireanyaffectedpartytobehaveinacertainway,ortoremovetherightofanysuchpartytotakeitsowncommercialdecisionsontheissuesdiscussedherein.Tothefullestextentpossible,theOWPBandtheauthorsdisclaimanyliabilityarisingoutoftheuseofthereport,includinganyactionordecisiontakenasaresultofsuchuse.


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TableofContents

DISCLAIMER..................................................................................................................................2

1 SUMMARY........................................................................................................................4

2 EXPORTCABLEFAILURERATE–UKEXPERIENCE............................................................5

3 CAUSEOFTHISHIGHFAILURERATE–UKEXPERIENCE..................................................6

4 OTHERRELEVANTEXPERIENCE........................................................................................7

5 EXPECTEDEXPORTCABLEFAILURERATE........................................................................8

6 COSTOFCABLEFAILURES................................................................................................9

7 SUGGESTEDACTIONSFORCOMPANIESORDERINGNEWCABLES...............................11

8 NEXTSTEPS.....................................................................................................................12


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1 SUMMARY

ThispreliminaryreportdescribestheUK’sexperienceofoperatinghighvoltage(³132kV)offshorewindfarmsubmarineexportcables.IntheUKallsuchexportlinksuseACcableswiththreepowercoresandatleastonefibreopticcorepackagedtogetherwithinonearmouredcable.TodatetheUKoffshorewindindustryhasexperiencedsevenpost-commissioningfailures(faultsorpre-emptiverepairs)onitsfleetofhighvoltageexportcables.Basedoninitialdetailsprovidedtousbytheownersofthesecables1,weunderstandthatsixofthesefailureswouldnothaveoccurredhadafibreopticcorenotbeenincludedwithinthepowercable.Inmostofthesecasesaninitialfailureinthefibreopticcoreappearstohavedevelopedsoastoaffectapowercore.Thereappeartobeavarietyofpossiblemechanismswhichcancausetheinitialfailureinthefibreopticcore,andavarietyofmechanismswherebythedamagemaypossiblyspreadtopowercores.TheauthorhasnotbeenabletoundertakeacomprehensivesurveyofcablefailuresoutsidetheUKoffshorewindsector,althoughtwofailuresontheGuernsey-Jerseycableandonefailureonanon-UKoffshorewindfarmcablearebelievedtobelinkedtofailuresinafibreopticcore.Uptotheendof2016thetotalexperience-baserepresentedbytheUK’sfleetofhigh-voltageoffshorewindexportcablestotalledover4,400km.years.Thesevenfailuresthatoccurred,therefore,representameantimebetweenfailuresof630km.years.Thiscompareswiththemeantimebetweenfailuresof1,400km.yearssuggestedbyCigreTechnicalBrochure379,whichhaspreviouslybeenthemainsourceofinformationonsubmarinecablereliability2.AnestimatehasbeenmadeofthecostoftheUK’shighvoltageexportcablefailures;thiscomprisesboththecostofrepairsandthecostoflostwindfarmproduction.Theestimatedtotalcostisabout£160m,ornearly£170kforeverykmofhighvoltageexportcablecurrentlyinservice.Thishighcostemphasisestheimportanceofeliminatingcables’vulnerabilitytofibreopticcorefailuresinfutureprojects.ThereportsetsoutthepositionofOFTOsandwindfarmdevelopersinrelationtohowbesttoensurethattherisksfacedbyfutureprojectsaresuitablymitigated.

1 As part of a later stage in the examination of these faults,we hope to arrange for the root cause analysis documentspreparedafterforeachofthesefailuretobereviewedbyanexperttocheckforcommonalitiesandtoverifytheapparentcommonroleofthefibreopticcore.

2 Both the number from Cigre and the number calculated fromUK export-cable experience suffer from being based onrelatively small sample sizes. Although neither number has strong statistical support, the UK number at least has theadvantageofbeingsolelybasedonrelevantcabletypes.


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2 EXPORTCABLEFAILURERATE–UKEXPERIENCE

AninvestigationhasbeenundertakenintothereliabilityofthehighvoltageexportcablesusedtoconnectUKoffshorewindfarmstotheonshoregrid.Thishasexaminedcablefailuresthatmetthefollowingsetofcriteria:

i) Thefailedcablewasathree-coreACsubmarinecableoperatingatanominalvoltageof132kVorhigher3.

ii) ThepurposeofthefailedcablewastoconnectaUKoffshorewindfarmtothegrid.

iii) Thefailedcablehadbeencommissionedandwasinnormalservicewhenthefailureoccurred.Theresultspresentedinthisdocumentthereforeexcludedamageduringconstructionthatrequiredthecabletoberepairedbeforeitcouldbeputintoservice4.Theresultsalsoexcludecaseswhereacablesufferedknownmechanicaldamageduringinstallationbut,asamatterofconvenience,thecablewastemporarilyputintoservicependingrepair.

iv) Thefailurethataffectedthecablemightbeeitherafault(shortcircuit),or

apre-plannedrepairtothecablewheretheownerbelievesthatafaultislikelytodevelop.Ineithercasetheaffectedcablewillbecut,thefaulty(orsuspect)partremoved,andareplacementlengthofsparecablejointedintoplace.

TheinvestigationfoundatotalofsevencablefailuresfromNovember2011todatethatmetthecriteriasetoutabove.Inaddition,atleasttwosituationsexistintheUKwhereanexportcable,whichremainsinservice,isexhibitingsymptomsthatsuggestthatafaultmaydevelop.Discussionswithalimitednumberofnon-UKcableownerssuggestthatasimilarsituationmayexistonatleastoneexportcableoutsideoftheUK.Uptotheendof2016thetotalexperience-baserepresentedbytheUK’sfleetofhigh-voltageoffshorewindexportcablestotalledover4,400km.years.Thesevenfailuresthatoccurred,therefore,representameantimebetweenfailuresofjustunder630km.years.Readersshouldnotethat–liketheCigredatadiscussedinSection5below–thismeantimebetweenfailuresnumberisbasedonalimitedsamplesizewiththefaultsbeingconcentratedonafewprojects.Thismeansthatunusuallygoodorbadresultsfromahandfulofprojectscaneasilybiastheresultsupordown.

3Noattempthasbeenmadetoexaminetheperformanceof lowervoltagethreecoreACcablessuchasthe33kVcableswidelyusedwithinoffshorewindfarms.Differencesinownershipmeanthatadifferentorganisationalapproachmayberequiredifitisdesiredtoextendtheworkdescribedinthisreporttoencompasssuchcables.

4Thehighlevelofinsuranceclaimsarisingfromsubmarinecabledamageduringload-out,laying,burial,orfromotherwindfarmconstructionactivities,hasbeenpubliclydocumentedbyseveral insurancecompanies.Suchsourcestypicallyshowcablesrepresentingaboutthreequartersofallclaimsonawindfarm’sconstructionallrisks(CAR)insurance.


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3 CAUSEOFTHISHIGHFAILURERATE–UKEXPERIENCE

Allthree-coreACcablesusedbyoffshorewindfarmscontainatleastonefibreopticcore(seefigure1).Figure1:(Left)crosssectionofatypical3-coresubmarinecableshowingtwopowercoresandthefibreopticcore.(Right)closeupofthefibreopticcore.Thisshowsopticalfibres(brightlycolouredstandsemergingfromcable),themetaltubeenclosingthefibres(thesilvercirclearoundthefibres),armouring(thethickersilverstandsaroundthemetaltube–notpresentinallfibreopticscores),andtheanti-corrosionsheath(thickblackplasticaroundthearmourlayer).Inthisdesignthefibreopticcoreisheldinplacebyamouldedplasticinsertwhichfillstheintersticesbetweenthepowercoresandthearmouring.Accordingtoinformationprovidedbythecableowners,sixofthesevencablefailuresreferredtoinSection2involvedfailureswithinthefibreopticcore.Thesefailuresinthefibreopticcoreeitherdevelopedtoaffectapowercore(themorecommonsituation),oranoutageofthepowercoreswasrequiredtorepairthefibres(lesscommon).Wherefailuresinthefibreopticcorehavedevelopedandaffectedapowercore,thedamagetothecablecausedbytheeventualshortcircuitmaymakeitdifficulttoestablishanyrootcause,andtherootcausesofthefailuresinthefibreopticcoresappeartovarybetweencases.Nevertheless,afewpointsaboutthefibreopticcorearerelevant:

i) Thefibreopticcoreismuchsmallerandlighterthanthepowercoreswithinthesamecable.Itisthereforemorevulnerabletobeingdamagedduringtheassemblyofthecablewherelargerandheaviercableelementsareinmotionaroundit.


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ii) Thefibreopticcoreisexposedtoa50Hzmagneticfieldfromtheadjacent

powercores.Thefibreopticcoresusedinsubmarinecablealwaysincludeametallictubetopreventseawaterfromreachingtheopticalfibresthemselves,andthemagneticfieldsthatthefibreopticcoreisexposedtocancausecurrentsandvoltagestobeinducedonthismetallictube,especiallyiffaultsortransientscausethemagneticfieldstobeunusuallystrong.(Forthecabledesignshowninfigure1above,thetubeismadefromstainlesssteelandissurroundedbyarmourwires;theseincreasemechanicalstrengthbutcanalsocarryaninducedelectricalcurrent).

iii) Despitethefactthatitmaybeexposedtosignificantcurrentsandvoltages,thedesignandtestingofthefibreopticcoreisfocussedontheopticalcharacteristicsoftheopticalfibresthatitcontains–notonitsabilitytowithstanditselectricalserviceconditions.Indeedwithsomedesignstheelectricalconditionofthefibreopticcoreisinherentlydifficulttomeasure,evenwhilethecableisstillinthefactory.

Althoughthelevelofdamagefromshortcircuitsoftenmakesdiagnosisdifficult,analysisbycableownerssuggeststhatthemechanismsbywhichafailureinafibreopticcorecouldaffecttheadjacentpowercore(s)alsovarybetweencases.Mechanismsinvolvingelectricaldischarge,overheatingandelectrochemicaleffects(corrosion)havebeensuggestedinvariouscasesandallneedtobefurtherinvestigatedandunderstood.ThereareseveraltypesoffibreopticcorepresentacrosstheUKexportcablefleet.Thefaultsthathaveoccurredhaveaffectedmorethanonetypeoffibreopticcore.Althoughsometypesoffibrecorehavenotyetbeenaffected,thelimitedamountofdataavailablemeansthatitisnotpossibletobeconfidentthatthesetypesdonotsharesomeorallofthesamevulnerabilitiesasthosetypesthathavealreadyexperiencedfailures.Whilethereismuchuncertaintyabouttheexactmechanismsandrisks,theanalysisundertakenbythecableownershighlightonekeypoint:ifthefibreopticcorehadnotbeenpresentinsidethepowercablethenthefailurewouldnothaveoccurred.Thisanalysissuggeststhatthefibreopticcoremaybeaweakpointforthewholepowercable:relativetothepowercoresitissmaller,lighter,haslimitedelectricalwithstandcapabilities,andissubjecttolittleornoelectricaltesting.Yetthepresenceofthefibreopticcoremayincreasethevulnerabilityofthewholecabletofullelectricalfailure.

4 OTHERRELEVANTEXPERIENCE

TheauthorsareawareofafewfailuresofsimilarhighvoltagethreecoreACcablesoutsideoftheUKoffshorewindindustry,thoughwedonothaveaccesstoacomprehensivelistoffailuresortheircauses.


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TheGuernsey-Jersey90kVcablehassufferedtwofailureswhichtheownerhaspubliclystated5wererelatedtoanissuewithinthefibreopticcore.Theseare:

i) Afaultonthecablein2012

ii) Apre-emptiverepairin2015.Inthiscaseforensicanalysisofthereplacedsectionofcableshowedthat“thepowercablewouldinevitablyhavefailedwithinaveryshortperiodoftime”hadthepre-emptiverepairnotbeenundertaken.

Theauthorsarealsoawareofatleastonenon-UKoffshorewindfarmexportcablewhereafaulthasbeenlinkedtoanissuewiththefibreopticcore.

5 EXPECTEDEXPORTCABLEFAILURERATE

Priortotheworkundertakenforthisreport,estimatesofthereliabilityofsubmarinecablestypicallyreferencedCigreTechnicalBrochure379(TB-379):“UpdateofServiceExperienceofHVUndergroundandSubmarineCableSystems”.Thepartofthisreportthatdealswithsubmarinecablesmadeuseofsubmarinecablefailuredatafrom32sources,coveringtheperiodfrom1990to2005.ThemostrelevantreliabilitydataprovidedbyTB-379isameantimebetweenfailuresofover1400km.yearsforthecategoryof“ACXLPE6cables”,withthebulkofthesefailuresbeingexternal(i.e.thecablebeinghitbyananchor,trawlboardorsimilar).UnfortunatelytheACXLPEcablescategoryusedbyCigreisextremelybroad,encompassingmanytypesofcablethatareirrelevantforUKoffshorewindapplications:

i) Nearlyhalfofthecablesinthiscategoryareatvoltagesbetween60kVand

110kV,makingtheirrelevancefortheUKfleetofcablesat132kVandabovequestionable.

ii) Athirdofallthecablesinthecategoryaresingle-core,andsoimmunetotheproblemsdescribedinSection3,whichareuniquetothreecorecables.AllwindfarmACcablesareofthethreecoretype.

iii) NoinformationisprovidedregardingwhetherthethreecorecablesinCigre’sdatasetincludefibreopticcoresornot(showinghowthisissuewasnotconsideredrelevantforreliabilityuntilrecently).

iv) Noinformationisprovidedregardingwhetherthecableisburiedornot.It

seemslikelythatmostoftheexternalfaultsindicatedbyCigreoriginatefromunburiedcablesections,andthatCigre’smeantimebetweenfailureswouldbemuchhigherifallofthecablesintheirdatasetwereburied,asUKwindfarmcablesare.

5SeetheannualreportofGuernseyElectricity,March2015.6CrossLinkedPolyethylene


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Despitethe“ACXLPE”categorybeingextremelybroad,thedatasetavailabletoCigrewasnotparticularlylarge:evenin2005,whenthefleetstudiedbyCigrewouldhavebeenatitslargest,thedatasetfor“ACXLPE”cableswasnotsignificantlylargerthanthecurrentUKoffshorewindhighvoltageexportcablefleet.This,presumably,iswhythewritersofTB-379wereunabletoprovidemoredetailedbreakdowns.Cigrehasrecentlyestablishedaworkinggroup(B1.57)whichaimstoupdateTB-379,andUKcableownersareurgedtocontributetoitswork.Thisgroupisnotexpectedtoissueitsfinalreportuntil2018:inthemeantimepartiesseekingstatisticaldataonexportcablereliabilitywillstillneedtoreferenceTB-379,butshouldconsidercombiningthiswithnewerdataknowntobedirectlyrelevanttowindfarmexportcables–suchastheUKexportcableexperiencesetoutinSection2above.

6 COSTOFCABLEFAILURES

Theeconomicimpactofawindfarmexportcablefailurecanbeexaminedunderthefollowingcategories:

i) Thecostofrepairingthecable.

ii) Thecostoflostwindfarmproductionoveraperiodthatcanrangefromseveralweeks(forapre-emptiverepair)to3-5months7.foranunexpectedfault.

iii) Incaseswherethereisonlyasinglecableconnectinganoffshore

substation,thefailureofthiscablewillresultinthelossofallauxiliarypowertothewindturbines.Thisinturnwillleadtocostsfortheprovisionoftemporaryemergencygeneratorsand/orextramaintenancecostswhereturbinesareleftwithoutpowerforanextendedperiod.

Thecostofcablerepairincludespreciselocationofthefault;mobilisationofasuitablerepairvessel,equipmentandpersonnel;deburialofthefailedcable;removalofalengthofcable–oftenseveralhundredmeterslong–thatincludesthefaultlocation;jointinginalengthofsparecabletoreplacetheremovedsection;andreburyingorotherwiseprotectingtherepairedcable.Costswilldependonmarketconditionsandweatherconditionsduringtherepair,butcanbeextremelyhigh.Table1showsaselectionofpubliclydisclosedcablerepaircosts:

7TherepairtimesforthefoursubmarinecablefaultsindicatedbytheNGETC17documentare106days(3.5months),133days(4.4months),153days(5.0months)and105days(3.5months)


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Table1:PubliclydisclosedcablerepaircostsRepair

Cost Source

Guernsey-Jersey(2012) £8m BBCNews

Guernsey-Jersey(2015,pre-emptive) £3.5m Owner’sannualreport

Moyle(2011-12),2repairs £15.5maverageperrepair

Owner’sannualreport

GwyntyMor(summer2015) £10.2m Ofgem(incomeadjustmentclaim)

GwyntyMor(2015-16) £14.2m Ofgem(incomeadjustmentclaim)

Thanet(2015) £11.7m Ofgem(incomeadjustmentclaim)

Excludingthesinglepre-emptiverepair,theaveragerepaircostfromthisdatasetis£12.5m.Thecostofapre-emptiverepairissubstantiallylessthanthecostofanunplannedrepair8.Inpractice,however,pre-emptiverepairsarefrequentlyimpossible:eitherbecausethecablegiveslittleornowarningoffailure,orbecause–giventhatthefailuremechanism(s)arestillpoorlyunderstood–theriskofunnecessarilyrepairingahealthycableisjudgedtobetoohigh.Asnotedabove,followinganunplannedfailureonaUKhighvoltageexportcablethetypicaltimerequiredtorepairthecableandreturnittoserviceis3-5monthsDuringthistimetheoutputofthewindfarmwillbecurtailed:

i) Ifthefailedcableistheonlyconnectiontoanoffshoresubstationthenalloftheoutputfromtheturbinesservedbythissubstationwillbelostuntiltherepairiscomplete.

ii) Iftherearetwo(ormore)cablesconnectinganoffshoresubstationthentheturbinesservedbythesubstationcancontinuetooperatewhilethefailedcableisrepaired,buttheiroutputwillberestrictedattimesofhighwind.

Basedontherepaircostsindicatedabove,theactualrepairtimesandsubstationconfigurations,andassumingthatexistingUKoffshorewindfarmshaveanaverageloadfactorof40%andatypicalincomeof£140/MWhr,aroughestimateofthetotalcosttotheindustryofthesevencablefailuresdescribedinSection2abovecanbecalculated.Theauthorestimatesthatthistotalcostisontheorderof£160m,roughlyequallysplitbetweenrepaircostsandthecostsoflostoffshorewindproduction.

8 Since Table 1 shows a cost for only one pre-emptive repair, we do not know if this £3.5m cost is typical or not.Nevertheless, it issomuch lowerthanthecosts fortheunplannedrepairsthat it issafetostatethatthecostofapre-emptiverepairwillbemuchlowerthanthatofanunplannedrepair.


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7 SUGGESTEDACTIONSFORCOMPANIESORDERINGNEWCABLES

FromthecalculationdescribedinSection6above,thesevenfaultsthathaveoccurredtodatehaveresultedincoststhathavealreadyreachednearly£170kperkmofexportcable.Suchacostisasignificantpercentageofthecapitalcostofthesecables,implyingthatsignificantactionsandexpendituresmaybejustifiedonnewprojectsinordertoensurethatnewlyprocuredcablesdonotsufferfromthesameissues.Thisreportisnotintendedtobeinstructional,anddoesnotmakeanyrecommendationstotheprocurersofnewhighvoltageexportcables.HoweverwehavesummarisedbelowthetwomainopinionsexpressedbymembersoftheExportCableReliabilityProject,theindustrygroupcreatedbytheOWPBtoaidindiscussionsonthisissue.Whethertofolloweitheroftheseopinionsisadecisionforthereader.OFTOs’OpinionTheOffshoreTransmissionOwners(OFTOs),actingthroughtheirrepresentativebody,theElectricityNetworksAssociationOFTOForum,haveprovidedthefollowingstatement:

Integral FOC presents an inherent weakness where any single/ minor defectcaused during manufacture, load out, or installation leads to a power corefailure. This failure mode was not foreseen and is not identified in publiclyavailablefailurestatistics.NoFATorSATregimeisinplaceatpresenttoidentifythepresenceofdefectsimpactingtheFOC.IntheopinionoftheENAOFTOForumitisessentialthatFATandSATtestsareinplace to verify the integrity of 3-core AC transmission submarine cables withintegralfibreopticcable(s).UntilsuchtestsareinplacethereisariskoffuturefailuresrelatedtotheFOC,andthisriskshouldberecognisedbyallstakeholders.FOC=fibreopticcoreFAT=factoryacceptancetestSAT=siteacceptancetest

Generators’OpinionsWhilethereisnoequivalent“official”viewheldbygenerators,severalpersonsinvolvedinthedevelopmentofgeneratorconnectionshaveexpressedtheviewthatitisprematuretoconsiderremovingfibreopticcoresfrompowercables.Inparticular,therewereconcernsthatmovingthefibrecorefromtheexportcabletoacableofitsownwouldresultinunnecessarycostsandcouldintroducenewrisks–bothknownrisks(e.g.fibredamageduringinstallation)andunanticipatedrisks.Furthermoreremovingfibreopticcoresfrompowercablesmayreducedevelopers’abilitytoapplydynamicratings,atechniquewhichcanofferoverallcostreductions–particularlyasdistancesincrease–andwhichcanallowincreasedwindfarmoutputduringoutages.


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Ifadecisionismadetoretainafibrecoreinsidetheexportcable,however,greatcarewillberequiredinordertominimisetheriskofafailureinthefibrecore.Ithasbeensuggestedthatsometypesoffibreopticcoremaybeinherentlylessvulnerable,ortheirintegrationintotheoverallcabledesignmaybeimproved,anditmaybepossibleforbuyerstoassessorimprovethevulnerabilityofcabledesignsby:

i) Suitablyaddingtotheirtechnicalrequirements.Forinstance,cablebuyerscouldspecifymaximumcurrents/voltagesallowedonthefibrecore’smetallictubeundernormalandfault/transientconditions.

ii) Explicitlyspecifyingdesignsthatshouldreducefibrecorevulnerability.Forinstance,weunderstandthatconsiderationhasbeengiventospecifyinganoptimisedlocationforthefibrecorewithinthepowercableinordertominimiseitsexposuretoelectromagneticfields,andtospecifyingabalancedsetoffibreswithperiodicphaserotationwithrespecttothepowercores.

iii) Questioningmanufacturers(includingrequestsforinformationandvalidation

tests)onrelevantissues(forinstancethemagnitudeofinducedcurrentsandvoltagesundervariouscircumstances)beforeplacinganorder.

iv) Suitablymonitoringthemanufacturing(and/orinstallation)processes(i.e.

enhancedqualityassurance).

8 NEXTSTEPS

TheExportCableReliabilityprojecthasdevelopedaplanwhichwouldproduceadvicethatoffshorewinddeveloperscouldusewhenprocuringnewexportcablesforfutureprojects.Thiscouldinclude,forinstance:

i) Adviceonquestionsthatshouldberaisedwithcablemanufacturers.

ii) Adviceoncalculationmethodologiesthatcablemanufacturerswouldbeaskedtousewhenrespondingtosuchquestions.

iii) Adviceonadditionstodevelopers’technicalrequirements.

iv) Adviceontestsofthefibreopticcoresthatdevelopers,OFTO’sandgenerators

shouldaskcablemanufacturerstoundertake.Atanyearlystagewithinsuchfuturework,itwillbenecessarytocollectinformationoneachfault(throughquestionnairesand/orreviewofrootcauseanalysisreports)forreviewbyasingleexpertteamtocheckforcommonalitiesandtoverifytheroleofthefibreopticcore.Workisongoingonrefiningthisplanandobtainingfundingforitsexecution.


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Documents

Export Cable Reliability Description of Concerns … Cable Reliability – Description of Concerns 2 DISCLAIMER This report has been written by Transmission Excellence Ltd on behalf