Reliability Assessment and its Improvement of Power Distribution Systems

Abstract

Unreliable electric power distribution affects daily activity and drags the modern lifestyle. The existing substation has encountered frequent power interruptions problems. The interruptions are caused mainly by the short circuit (SC) and earth fault (EF). There are also planned outages for operation and maintenance purpose. The substation?�?s System Average Interruption Frequency Index (SAIFI) and System Average Interruption Duration Index (SAIDI) are 521.46 interruptions per customer per year and 446.82 hours per customer per year, respectively. The substation is not reliable by the standard of Ethiopian Electric Agency (EEA) which has set SAIFI as equal to 20 interruptions per customer per year and SAIDI which is around 25 hours per customer per year. This reliability gap calls for exploring effective methods for improving the reliability of the distribution system. Thus, the objective of the study is to assess the reliability of the existing distribution system and suggest solutions for reliability improvement in heuristic techniques. To limit the scope of the study, 15 kV Harar city feeder of the substation has been chosen for reliability improvement measures. The historical outage interruption data of years 2016-2018 G.C has been used as a base year. The study has evaluated five different mitigation scenarios to improve the system reliability. From the mitigation scenarios with the lowest SAIDI, SAIFI and Expected Energy Not Supplied (EENS) at a reasonable cost has been selected. The simulation results have been done with the help of Electrical Transient Analysis Program (ETAP 12.6) software. The result of this thesis work reveals that the reliability of the system has been improved significantly by implementing reliability improvement solutions that