Study of Reliability of Power Distribution System and Improvement Options at Awash7 kilo Substation, Ethiopia

This paper presents a study of reliability of power distribution system and improvement options at Awash7 kilo substation in Ethiopia. Basically, power distribution reliability has been a major challenge in Awash7 kilo city. The existing substation has encountered frequent and long 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. 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 Awash7 kilo city feeder of the substation has been chosen for the reliability improvement measures. In the study, four different mitigation scenarios have been assessed using the heuristic method to improve the system reliability. From the mitigation scenarios with the lowest SAIDI, SAIFI and Expected Energy Not Supplied (EENS) has been selected as an optimal one. The simulation results have been done with the help of Electrical Transient Analysis Program (ETAP 16.0) software. The result of this study reveals that the overall reliability of Awash7 kilo city feeder has been improved by 86%, 85.4% and 92.94% for SAIFI, SAIDI, and EENS respectively as compared with the existing system by incorporating a mitigation technology in to the network model. The economic analysis shows that the selected solution results in a cost saving of 20,229.47 USD per year from the unsold energy of one feeder only with three years payback period investment for the implementation of the reliability mitigation technology.