Online Location of Faults on AC Cables in Underground Transmission Systems

224 Pages·2014·10.98 MB·English

by  Christian Flytkjær Jensen (auth.)

Springer Theses
Recognizing Outstanding Ph.D. Research
Christian Flytkjær Jensen

Online Location of
Faults on AC Cables
in Underground
Transmission
Systems
Springer Theses
Recognizing Outstanding Ph.D. Research
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Christian Flytkjær Jensen
Online Location of Faults on
AC Cables in Underground
Transmission Systems
Doctoral Thesis accepted by
Aalborg University, Aalborg, Denmark
123
Author Supervisors
Christian Flytkjær Jensen Prof.ClausLeth Bak
Department of EnergyTechnology Department of EnergyTechnology
Aalborg University Aalborg University
Aalborg Aalborg
Denmark Denmark
UnnurStella Gudmundsdottir
Transmission Lines
Energinet.dk
Fredericia
Denmark
ISSN 2190-5053 ISSN 2190-5061 (electronic)
ISBN 978-3-319-05397-4 ISBN 978-3-319-05398-1 (eBook)
DOI 10.1007/978-3-319-05398-1
Springer ChamHeidelberg New YorkDordrecht London
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(cid:2)SpringerInternationalPublishingSwitzerland2014
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Parts of this thesis have been published in the following articles:
• C. F. Jensen C. L. Bak, U. S. Gudmundsdottir, ‘‘State of the art Analysis of
Online Fault Location on AC Cables in Underground Transmission Systems’’,
NORD-IS 2011.
• C. F. Jensen, U. S. Gudmundsdottir, C. L. Bak, and A. Abur, ‘‘Field Test and
Theoretical Analysis of Electromagnetic Pulse Propagation Velocity on
Crossbonded Cable Systems’’, IEEE transaction on power delivery.
• C.F.Jensen,O.M.K.K.Nanayakkara,A.D.Rajapakse,U.S.Gudmundsdottir,
and C. L. Bak, ‘‘Online Fault Location on Crossbonded Cables Using Sheath
Current Signals’’, IPST 2013, Vancouver, Canada.
• C.F.Jensen,O.M.K.K.Nanayakkara,A.D.Rajapakse,U.S.Gudmundsdottir,
and C. L. Bak, ‘‘Online Fault Location on Crossbonded Cables Using Sheath
Current Signals’’,Electric PowerSystems Research (EPSR)Special IPST 2013
edition.
• C. F. Jensen, U. S. Gudmundsdottir and C. L. Bak, ‘‘Online Fault Location on
Crossbonded AC Cables in Underground Transmission Systems’’, Cigré 2014
Paris session.
• C.F.JensenandC.L.Bak,‘‘DistanceProtectionofCrossbondedTransmission
Cable- Systems’’, DPSP 2014.
To Nicoline Louisa Frank Iversen
Supervisor’s Foreword
I have had the pleasure of following Christian during his studies from the early
beginningsatthefirstsemesterandfromtimetotime,bothasalecturerandalsoas
a supervisor. Gradually, it became clear to me that he was more talented than the
average student, not only in the ability to learn, but also in having a better
fundamental understanding of Physics, a profound interest in Electric Power
Engineering,theabilitytoworkindependentlyandcomeupwithcleverideasand
at the same time being a very nice guy.
Christian had many outstanding presentations during his postgraduate studies.
He independently selected a very interesting and complicated ninth semester
projectrelatedtoswitchingtransientsinoffshoretransmissioncableconnectionto
a large offshore wind farm. This study wasconducted in cooperationwith Danish
TSO Energinet.dk. His results were of such high quality that they were published
in the highly esteemed IPST conference in a scientific paper, ‘Switching studies
for the Horns Rev 2 wind farm main cable’. A ‘normal’ student would have
selected some kind of similar continuation for the 10th semester master’s thesis
project in order tocontinue the success and avoid risk inthe final project, butnot
Christian. He wanted a new technical challenge and so it became. I selected,
together with a clever Ph.D. student I supervised at that time, a very challenging
projectrelatedtotheharmonicsemittedfromlargeoffshorewindfarms.Thiswork
includedmanydisciplinessuchasadvancedstochasticmethodsandpowersystem
modelling as well as the interpretation and processing of huge amounts of data
fromreal-lifemeasurements.Hesucceededagainandreceivedthehighestpossible
markinhisfinalexamination.Again,hisworkwasofsuchhighqualitythatitwas
publishedintheWindIntegrationWorkshop2011inapaperentitled‘Probabilistic
aspects of harmonic emission of large offshore wind farms’. Christian was a
brilliant student and a pleasure to work with, not only seen from a professional
pointofview,butalsofromhavinghimasakindofcolleague.Iactuallyfacedhis
immediatepartingupon master’s withregret.It wasashametoletgo ofso much
clever thinking just in the perfectly right ‘engineering mode’.
Sowhattodoasauniversityman?Theonlyrightthingtodoistotryoffering
such a guy a Ph.D. position. In this way, Christian would be able to develop his
skills, let them grow and mature, and as a supervisor, I would benefit from
accessingandbeingapartofthehighlyinterestingresearchworkhewillperform
for 3 years.
ix
x Supervisor’sForeword
Danish TSO Energinet.dk and I have had a very long ongoing and fruitful
cooperation.Once,Iworkedinthepracticallifetransmissionengineeringbusiness
inaregionaltransmissioncompanywherewecooperatedmuchwithEnerginet.dk
(at that time ELSAM), and this continued when I got the position at the Depart-
ment of Energy Technology, Aalborg University. Many student masters’ theses
and personal research were initiated by this valuable cooperation. Together,
Energinet.dkandIestablishedaresearchprogramme‘DANPAC’(DANishPower
systemwithAcCables)researchinghowtouselongundergroundACcablesinthe
150 and 400 kV transmission system. One position came up in this programme
relatedtofaultlocationinundergroundcablesystems.IknewChristianwouldlike
to continue his research-oriented way of working so I decided to offer him the
Ph.D. position. Today, I am happy to say that it turned out to be a very good
decision!
In order to understand the motivation of the project and its usefulness, some
background information is necessary. Usually, a transmission system consists of
overhead lines and only a very limited (and short length) amount of underground
cables. The Danish government has decided that almost the entire transmission
systemhastobeundergroundedduetoaestheticreasons.Whenafaulthappensin
an overhead line, you can easily find the faulted location and repair it, simply
because it is visible. This is not the case with underground cables as they are
literally buried and thereby, faults are much more difficult to locate as the cable
has to come up from underground for inspection. Therefore, fault location for
cable systems is more difficult, time-consuming and expensive compared to
overhead lines.
Christian’s task was to develop and implement a method capable offinding a
fault in an undergrounded cable and with the best possible precision, taking into
account the practical limitations a real power system would pose on such a
method.Inotherwords,wewanttobeable,moreorless,todigdirectlytothefault
instead of having to dig up several kilometres of cable.
Christian has solved this very complex task in a very fine and structured way;
he worked like a real scientist. However, even more importantly, he always kept
full connection with the real world with numerous discussions with me and
Energinet.dk, in the end ensuring that his method is actually almost directly
applicable to the power system, and Energinet.dk intends to do this for future
works. The work was solved using:
• Impedance-based methods for detecting the faulted location
• Travelling wave-based methods for detecting the faulted location
• High quality real-life measurements on the Anholt offshore wind farm 220 kV
cable
• Implementation and validation of travelling wave method into Labview
environment
Supervisor’sForeword xi
Christian’sPh.D.thesiswasassessedbyhighlyesteemedProfs.FredeBlaabjerg,
CarloAlbertoNucciandAkihiroAmetaniwiththedesignation,‘heisanexcellent
researcher’, aconclusion Istrongly support.
When thinking back over the years with Christian, I have come to the con-
viction that what I liked most when working with him was the profound physics
discussions. He is perhaps the student whom I have spent most time supervising,
but numerous were our fruitful discussions related to electromagnetic field theory
and wave propagations. He could send emails in the evening putting up weird
questions like ‘Why do we see this bump at the curve here and not when we
change?’. The next day, we would use an hour in my office and always come up
withtheexplanation,knowingthatwegotmoreandmoreclevereachtimewedid
it.IhaveverymuchenjoyedworkingwithChristianduringthis3-yearperiod!The
bookinfrontofyoupresentsChristian’sfineworkduringhisPh.D.andIsincerely
hope you will find it valuable and enjoy reading it.
Aalborg, December 2013 Claus Leth Bak