Det här examensarbetet har utförts på uppdrag åt Trollhättan Energi AB (TEAB). Examensarbetet är en utredning beträffande förutsättningar för sammankoppling av TEAB:s och Hjärtum Elförenings elnät. De nuvarande ledningsnäten har radialnät och det innebär att det endast har inmatning från ena ledningsänden. En sammankoppling skulle ge möjlighet till sektionerad drift vilket innebär inmatningsmöjligheter från båda ledningsändar. Det gör att ledningsnätet blir mer säkert, tillförlitligt och effektivt. Ett förslag på ett nytt ledningsnät där delar av TEAB:s och Hjärtum Elförenings ledningsnät är sammankopplade har tagits fram. Med det nya förslaget blir ledningsnätet mer driftsäkert och uppfyller lag- och myndighetskrav. Beräkningarna som ligger till grund för arbetet är teoretiskt utförda. Därför bör en fortsatt planering och undersökning inom ämnet utföras innan ledningsnäten sammankopplas. Budgetpriset för ombyggnationen i ledningsnätet har beräknats till cirka 700 000 kronor och investeringen anses nödvändig för att kunna utföra en sammankoppling utav elnäten. / This bachelor´s thesis is conducted on behalf of Trollhättan Energi AB (TEAB). The bachelor´s thesis is an investigation of conditions for interconnection of TEAB and Hjärtum Elförenings electrical grids. The current electrical grids are radial electrical grids and means that it can only be fed from one cable end. An interconnection would allow for sectional operation of the electrical grid. This means input opportunities from both cable ends and that the electrical grid becomes more safely, reliably and efficiently. Suggestion for new electrical grids which parts of TEAB and Hjärtum Elförenings electrical grids are interconnected has been developed. With the new suggestions becomes the electrical grid more reliable and complies with legal and regulatory requirements. The calculations that are underpinning the work is theoretical. Therefore, a continued planning and research in the subject should be performed before the electrical grids are interconnected. Budget price for the reconstruction of the electrical grids have been estimated to be about 700 000 SEK and the investment is considered essential for the interconnection.

The power distribution system is the final link to transfer the electrical energy to the individual customers. It is distributed in a complex technical grid but is associated with the majority of all outages occurring. Improving its reliability is an efficient way to reduce the effects of outages. A common way of improving the reliability is by designing loop structures containing two connected feeders separated by a section point. The location of the section point will decide how the system structure is connected and its level of reliability. By finding the optimal location, an improved reliability may be accomplished. This Master’s thesis has developed a method of finding optimized section points locations in a primary distribution system in order to improve its reliability. A case study has been conducted in a part of Mälarenergi Elnät’s distribution system with the objective of developing an algorithm in MATLAB able to generate the optimal section points in the area. An analytical technique together with a method called Failure Modes and Effect Analysis (FMEA) as preparatory step, was used to simulate the impact of outages in various components based on historical data and literature reviews. Quantifying the impact was made by calculating the System Average Interruption Duration Index (SAIDI) and the Expected Cost (ECOST) which represented the reliability from a customer- and a socio-economic perspective. Using an optimization routine based on a Greedy algorithm an improvement of the reliability was made possible. The result of the case study showed a possible improvement of 28% on SAIDI and 41% on ECOST if optimizing the location of section points. It also indicated that loop structures containing mostly industry-, trade- and service-sectors may improve ECOST considerably by having a relocated section point. The analysis concluded that based on the considerable improvement the case study showed, a distribution system could be highly benefitted by optimizing the location of section points. The created algorithm may provide a helpful tool well representative for such a process in a cost-effective way. Applying it into a full size system was considered being possible but it would first require some additional improvements of reliability inputs and to resolve some fundamental issues like rated current in lines and geographical distances to substations.