Online Location of Faults on AC Cables in Underground Transmission Systems

289 Pages·2017·21.31 MB·English

Aalborg Universitet

Online Location of Faults on AC Cables in Underground Transmission Systems
Jensen, Christian Flytkjær
Publication date:
2013
Document Version
Publisher's PDF, also known as Version of record
Link to publication from Aalborg University
Citation for published version (APA):
Jensen, C. F. (2013). Online Location of Faults on AC Cables in Underground Transmission Systems.
Department of Energy Technology, Aalborg University.
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July2013
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Online Location of Faults on AC Cables in
Underground Transmission Systems
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ChristianFlytkjærJensen
Energinet.dk&AalborgUniversity
email: [email protected]

ONLINE LOCATION OF FAULTS ON AC CABLES IN
UNDERGROUND TRANSMISSION SYSTEMS
by
ChristianFlytkjærJensen
DissertationsubmittedtotheFacultyofEngineering,ScienceandMedicineat
AalborgUniversityinpartialfulfilmentoftherequirementsforthedegreeof
DoctorofPhilosophyinElectricalEngineering
DepartmentofEnergyTechnology
AalborgUniversity,Denmark
July2013

Preface
This thesis is submitted to the Faculty of Engineering, Science and Medicine at Aalborg
University in partial fulfilment of the requirements for the PhD degree in Electrical Engi-
neering. Theresearchhasbeencarriedoutbetweenthe1.09.2010andthe15.07.2013atthe
DepartmentofEnergyTechnologyforEnerginet.dkbywhichIwashiredasaPhD-student
fortheentireprojectperiod.
The project has been followed full time by two supervisors: Professor Claus Leth Bak
(DepartmentofEnergyTechnology)andDr. UnnurStellaGudmundsdottir(Energinet.dk).
Energinet.dkhasfullyfundedtheresearchleadingtothisthesis”OnlineLocationofFaults
onACCablesinUndergroundTransmissionSystems”. Thisfundinghasbeenvitalforthis
researchproject. Travellingtoconferences,twovisitsatforgingresearchinstitutions,rent-
ingoflaboratoryequipmentandperformanceofandfieldmeasurementswasmadepossible
thankstosupportfromthecompany.
IspendtheperiodfromApriltoJune2013atNortheasterUniversityinBoston,USA,under
thesupervisionofProfessorAliAbur. Here,iworkedontwoIEEEtransactionpaperswith
oneofthemco-authoredbyProfessorAbur.
InSeptember2013ispendonemonthattheManitobaHVDCResearchCentreinWinnipeg
working on fault location on hybrid lines and analysing my field measurements. During
this stay I corroborated with PhD-student K. Nanayakkara and Professor A. D. Rajapakse
bothfromthedept. ofElectricalandComputerEngineerUniversityofManitoba,Winnipeg
Canada.
DuringtheprojetperiodIsupervisedtwomasterprojectsandthoughtonesemestercourse
inpowersystemtransients.
ThescientificpaperswrittenasapartofthisPhDareincludedinthebackofboththeprinted
versionofthethesisaswellasinthePDF-file. Thepapersshouldnotbeconsideredapart
ofthismonograph,butareenclosedifthereaderisinterested.
This thesis has five parts and appendices. An overall literature reference list is presented
at the end of the main report. A list of the authored publications is presented at the end of
the thesis. Literature references are shown as [i], where i is the number of the literature in
the reference list. Tables, figures and equations are shown as C.F, where C is the chapter
numberandFisauniquenumberforthefigureortable.
Acknowledgements
Iowegratitudetomanypeoplewhohelpedmeindifferentways. Iwouldliketothank:
• Mysupervisors,ClausLethBakandUnnurStellaGudmundsdottirforalltheirhelp,
comments,andmanytechnicaldiscussionsduringthelastthreeyears.
• Carl-ErikMadsen,HenrikKastbergandCarlWilliHansenfortheirhelpwithcarrying
outthefieldmeasurements. Inthesameregards,averyspecialthanksisextendedto
Filipe Faria da Silva and Unnur Stella Gudmundsdottir for participating during all
measurements.
• FilipeFariadaSilvafornumeroustechnicaldiscussions,forreadinglargepartsofthe
thesisandformanygoodtimesintheoffice.
• Rasmus Schmidt Olsen, Unnur Stella Gudmundsdottir, Joachim Holbøll, Per Balle
Holst, PoulErikPedersen, ThomasKvarts, CarstenRasmussen, ClausLethBakand
Bjarne Søndergaard Bukh for their contributions and comments during the project
period.
• EveryoneatthetransmissiondepartmentatEnerginet.dkfortheircontributions.
• Professor Ali Abur for his hospitality and comments to my work during my three
monthstayatNorthEasternUniversityinBoston2012.
• Everybody at the Manitoba HVDC Research Centre, Winnipeg, Manitoba for their
help with my research during the month I spent there in 2013. A special thanks to
JohnNordstromandJuanCarlosGarciaforhelpingtoarrangemystayattheResearch
Centrewithveryshortnoticeandformakingmystaytherepleasant.
• AspecialthankstoDr. JeewanthaDaSilvafornumerousdiscussions,valuableadvice
andguidancethroughouttheentireprojectperiod.
• To Prof. Athula Rajapakse and PhD-student Kasun Nanayakkara both from Univer-
sity of Manitoba, Winnipeg, Manitoba for valuable discussions during my stay in
Winnipeg.
• ToTineLykkeTindalSørensenforproofreadingmostpartsofthethesis.
• Finally, to my girlfriend Nicoline Louisa Frank Iversen for her patience, understan-
ding,loveandsupportespeciallyduringthefinalisingofthethesis.
ChristianFlytkjærJensen,July2013,Aalborg
Abstract
A transmission grid is normally laid out as an almost pure overhead line (OHL) network.
The introduction of transmission voltage level XLPE cables and the increasing interest in
the environmental impact of OHL has resulted in an increasing interest in the use of un-
derground cables on transmission level. In Denmark for instance, the entire 150 kV, 132
kV and 220 kV and parts of the 400 kV transmission network will be placed underground
before2030.
Toreducetheoperatinglossesofacable-basedtransmissionsystem,crossbondingschemes
arenormallyused. Theuseofcrossbondingintroducesnewdifficultiesforthefaultlocator
systems currently in use and such can therefore not be applied directly. In this thesis, the
analysis and development of a fault locator system capable of locating faults with high
accuracy on crossbonded cables and hybrid lines is presented. The thesis is divided into
five parts; The preliminaries, a part which deals with the use of impedance-based fault
location methods on crossbonded cables, a part which deals with travelling wave-based
faultlocation,apartlistingtheconclusionsandcontributionsofthethesisandanappendix.
Astate-of-the-artanalysisisconductedontheuseofbothimpedance-andtravellingwave-
based fault location methods, and it is found in both cases that the research field is not
covered in detail. Therefore, the use of both fault location methods is examined in detail.
It is found that an impedance-based method is difficult to implement in practice due to
the electrical behaviour of the crossbonded cable system under fault conditions. The fault
loopimpedanceappearsasbeingdiscontinuousatthecrossbondings. Thesediscontinuities
dominate the fault loop impedance for shorter cables and the result is large errors if the
reactivepartisuseddirectlytodeterminethedistancetofault. Thediscontinuitiesmakethe
utilisation of an analytical methods difficult, as fault location methods in general expect a
homogenousseriesimpedancematrixfortheentirecablerun.
An analysis of the influencing parameters is carried out and it is found that the fault loop
impedance is almost independent on the grounding resistances in the field at the ends of
eachmajorsectionandonthegroundingresistanceatthesubstations. Thisisbecauselittle
currentreturnstothesourceinthegroundandthefaultloopimpedanceisthereforemostly
dependentonparametersdescribingthecableitself.
Theuseofanimpedance-basedmethodforfaultlocationonhybridlinesisexamined. The
very different fault impedances of the overhead lines and cable systems make a practical
implementationofthefaultlocatordifficult. SmalldeviationsintheparametersoftheOHL
willresultinlargeerrorsforfaultlocationinthecablesection.