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Analys av systemegenskaper på ett regionnät hos Härjeåns Nät AB
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
2015 (Swedish)Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
Sustainable development
Sustainable development according to the University's criteria is not relevant for the essay/thesis
Abstract [sv]

Det ställs höga krav på att elleveransen i Sverige skall vara kontinuerlig och av hög kvalité. Asymmetri i elnät på grund av elektriska och magnetiska fält mellan faserna kan leda till att nollpunktspänningen i nätet blir hög. Detta examensarbete undersöker huruvida otransponerade ledningar påverkar asymmetrin, och därmed nollpunktspänningen i nätet. Transponering innebär att faserna i en kraftledning byter plats med varandra så att de ligger lika lång sträcka i varje position. En fallstudie på Härjeåns Nät har utförts med fokus på detta. Härjeåns Nät har problem med hög nollpunktspänning i delar av sitt regionnät. Med hjälp av ett modelleringsprogram som tillhandahålls av Sweco utförs beräkningar av vad den teoretiska nollpunktspänningen i ett otransponerat nät bör bli. En litteraturstudie har även gjorts för att ta reda på om andra författare anser att transponering är nödvändigt eller inte. Både resultaten av litteraturstudien och de beräknade resultaten pekar åt samma håll. Resultaten visar att den höga nollpunktspänningen mest troligt inte beror på otransponerade elledningar men en slutsats är trots detta att transponeringar bör utföras vid ny- eller ombyggnad av större ledningar.    

Abstract [en]

There are high demands on the supply of electricity in Sweden. The supply shall be continuous and of high quality. Asymmetry of power grids due to electric and magnetic fields between the phases may cause high neutral-point displacement voltage. This bachelor degree work investigates whether untransposed transmission lines affect the asymmetry, and thus the neutral-point displacement voltage in the network. Transposing of a transmission line means that the phases of the line change places so that they occupy the same distance in each position. A case study on Härjeåns Nät has been conducted focusing on this. Härjeåns Nät has problems with high neutral-point displacement voltage in parts of their sub transmission network. With the help of a modeling program provided by Sweco, calculations have been performed of what the theoretical neutral-point displacement voltage in an untransposed network should be. A literature study has also been carried out to find out if other authors consider that transposition is necessary or not. Both the results of the literature study and the calculated results points in the same direction. The results show that the high neutral-point displacement voltage is most likely not due to untransposed power lines, but one conclusion is, nevertheless, that transpositions should be carried out when building a new transmission line or reconstructing an old one.   

Place, publisher, year, edition, pages
2015. , 23 p.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:hig:diva-21186OAI: oai:DiVA.org:hig-21186DiVA: diva2:900833
External cooperation
Härjeåns Nät AB
Subject / course
Energy systems
Examiners
Available from: 2016-02-11 Created: 2016-02-05 Last updated: 2016-02-11Bibliographically approved

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