Tillförlitlighetsanalys av Fortums lokalnät med hjälp av Tekla NIS

When making decisions regarding investments and planning of the distribution network, it is of great help to be able to calculate and analyze the reliability. The main interest is to study how many of the faults occur and the duration of these faults. The software Tekla NIS contains a module for calculation of the reliability of distribution systems, this is also known as reliability based network analysis. To perform the calculations a set pf parameters are used as input. In this report it is shown how these parameters can be calculated from fault statistics for several different geographical areas. Also, a sensitivity analysis has been performed to show the effect each individual parameter has on the results. A method on how to verify the parameters against fault statistic is presented. The aim here has been to match the calculation results in Tekla NIS with fault statistic from Fortum between 2011 and 2013. Tekla NIS lacks support to perform calculations on meshed networks. Therefore the calculations have been concentrated to three radial areas, Halland, Skaraborg and north Värmland. After the parameters have been calculated and verified some simple analysis is made to show how Tekla NIS can be used to evaluate investments for improved reliability. For example it is studied how replacing overhead lines with ground cable affects the reliability. The conclusion is that Tekla NIS is not at present a sufficiently good tool to calculate the reliability in Fortum’s local network, especially if one is interested in knowing the number of faults for a specific line. The results for a single line can have a big discrepancy with the statistics even though the area as a whole has results that corresponds well with the statistics. The inability for Tekla NIS to perform calculations on meshed networks is a major weakness and is the main reason that not all areas of Sweden were calculated. To identify weak parts of a network is the key feature of Tekla NIS at present. If the objective is to find the weakest lines in an area and the exact reliability is not of interest then Tekla NIS can be used with good results. If current problems in the software can be corrected Tekla NIS could be of the great use for Fortum and other utilities in the future, mainly to help with evaluation of investments. Tekla NIS is easily configured, enabling fast evaluation of different and reliability calculations for single lines are very fast