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Optimal nätdesign: Utvärdering och jämförelse av nätstrukturer i Stockholms mellanspänningsnät
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2017 (Swedish)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesisAlternative title
Optimal grid design : Evaluation and comparison of network structures in Stockholm's MV-grid (English)
Abstract [en]

In today’s society the electric grid has become one of the most important infrastructures and industries as well as other infrastructures, and individuals rely on its functionality. The unavailability of electricity caused by outages is increasingly rare but when it occurs it can have serious consequences. An electric grid’s reliability is now a requirement, not only from customers but also from the regulatory authority.The electric grid in Stockholm is owned and operated by Ellevio AB. Over the past decade the reliability, measured in SAIDI (System Average Interruption Duration Index), in the area has deterioated, mainly due to failures of the medium voltage grid (11- kV, MV). The network structure on the MV- grid consists primarily of two parallel medium voltage cables each of which acts redundantly to its pair cable. The technique, called dual cable structure, works most optimally with substations with automatic switching, which automaticly switch over to the redundant cable when failure occurs. However substations without this automatic switching are widely used resulting in a longer interruption time. Another network structure is the ring or loop structure, which still has redundancy, but when failure occurs a load- break switch must close so that the grid can be fed from another direction. The substation in the loop structure can also be remotely controlled, making the load-break swith operable from the control center, resulting in a shorter interruption time.This thesis evaluates and compares different network structures consisting of dual cable with automatic switching and loop structure with remotely controlled substations, based on economy and reliability, on Stora Essingen. The two structures have been designed in the network information system program Trimble NIS and divided into two different environments; one developed and one undeveloped environment. The results show that the technical solutions in network structures of MV- grid do not necessarily mean major differences in economy nor reliability, rather the choice between few but long interruptions and many but short interruptions is central. Results show however that a combination of the dual cable structure with remotely controlled substations in the undeveloped environment is economically motivated while the reliability can be maintained at the same tame.

Place, publisher, year, edition, pages
2017. , 96 p.
Series
UPTEC ES, ISSN 1650-8300 ; 17 005
Keyword [en]
loop structure, ring structure, dual cable structure, reliability, electrical distribution system, smart communication, remote controlled substation, smart secondary substation, ADMS, SAIFI, SAIDI, CAIDI
Keyword [sv]
slingstruktur, dubbelkabelstruktur, tillförlitlighet, distributionsnät, smart kommunikation, fjärrstyrda nätstationer, smarta nätstationer, ADMS, SAIFI, SAIDI, CAIDI
National Category
Energy Systems Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-321898OAI: oai:DiVA.org:uu-321898DiVA: diva2:1095101
External cooperation
Ellevio AB
Educational program
Master Programme in Energy Systems Engineering
Supervisors
Examiners
Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2017-05-24Bibliographically approved

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