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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Obstacles for Remote Air Traffic Services: A Multilevel Perspective / Utmaningar för fjärrstyrda flygtrafiktjänster: Ett multinivåperspektiv

Segersten, Kristoffer, ZHAI, KEREN January 2018 (has links)
Air traffic services (ATS) play an important role for flight safety. Remote air traffic services (RATS) represent a novel, more digitalized, ATS solution. In some aspects, RATS can be argued to outperform conventional ATS. However, as it entails various sociotechnical obstacles, making RATS the dominant solution for ATS is challenging. An inadequate awareness of such sociotechnical obstacles potentially impedes the competitiveness of RATS in general and the RATS providers in particular. This study intends to - from a sociotechnical perspective - identify main obstacles as faced by RATS when aspiring to become the dominant solution for ATS. In order to identify such obstacles, an abductive case study has been conducted. Empirical data was primarily gathered by semi-structured interviews with 10 key stakeholders involved, directly or indirectly, with RATS. The study is delimited to principally gather empirics from Sweden and the United Kingdom. Theoretical concepts of Large Technical Systems (LTS) and the Multilevel Perspective (MLP) are employed to understand and analyze the empirical data. The identified obstacles faced by RATS are mapped into the different levels of the MLP. Obstacles have been identified in all levels of the MLP. The most prominent obstacles seem to lay in social aspects of change processes, a proposition-perception gap, and connectivity infrastructure dependency. / Flygtrafiktjänster (ATS) spelar en viktig roll för flygsäkerhet. Fjärrstyrda flygtrafiktjänster (RATS) representerar en ny, i högre grad digitaliserad, lösning för ATS. I vissa avseenden kan RATS anses prestera bättre än konventionellt utförda flygtrafiktjänster. Vägen mot ett tillstånd där RATS är den dominerande lösningen för RATS är dock kantad av olika sociotekniska utmaningar. En otillräcklig medvetenhet om dessa utmaningar kan potentiellt minska konkurrenskraften för RATS i allmänhet och för utvecklare av RATS i synnerhet. Denna studie syftar till att, från ett sociotekniskt perspektiv, identifiera utmaningar som RATS står inför i, en situation där RATS ämnar ta steg mot att bli den dominerande lösningen för ATS. För att identifiera sådana utmaningar har en abduktiv fallstudie utförts. Empirisk data samlades huvudsakligen in genom semi-strukturerade intervjuer med 10 intressenter, direkt eller indirekt involverade, i RATS. Studien är avgränsad till att huvudsakligen samla in empirisk data från Sverige och Storbritannien. Teoretiska ramverk och begrepp beträffande Large Technical Systems (LTS) och Multilevel Perspective (MLP) används för att förstå och analysera empirisk data. De identifierade utmaningarna kopplas till de olika nivåerna i MLP. Utmaningar har identifierats i alla nivåer av MLP, och de mest framstående utmaningarna tycks ligga i sociala aspekter av förändringsprocesser, ett gap mellan proposition och perception, samt ett beroende av uppkopplingsinfrastruktur.
2

Optimal nätdesign : Utvärdering och jämförelse av nätstrukturer i Stockholms mellanspänningsnät / Optimal grid design : Evaluation and comparison of network structures in Stockholm's MV-grid

Wennberg, Simon January 2017 (has links)
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.

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