Reliability Analysis Of 15kv Distribution System Network (Case Study: Addis Alem Substation Network)

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Addis Ababa University


Reliability engineering with regard to distribution systems involves gathering outage data and evaluating system designs. The great majority of service interruptions that affect customers are caused by problems on the distribution system. For the analysis, data has been collected from Addis Alem electric distribution system. The collected data are a recorded data that includes types of faults, frequency and duration of interruption of 15kV outgoing feeders’ of the distribution system. Currently customer served from Addis Alem substation are affected by frequent power interruptions and power quality problems. The interruptions are caused mostly by earth fault and short circuit. There also planned outage for operation purposes. The substation’s System Average Interruption Frequency Index (SAIFI) is 178.37 Interruption per customer per year, System Average Interruption Duration Index (SAIDI) is 152.22 Hour per customer per year. The substation is not reliable by the standard of Ethiopian Electric Agency (EEA) which set (SAIDI = 25 and SAIFI = 20). This reliability disparity requires finding the best solution for improving the reliability of distribution system. Therefore, the best solutions to distribution system reliability problems, integrating Distribution Generation (DG) to the existing network as backup, which is evaluated in this thesis. For best placement of DG on the distribution system at different load point, reliability improvement with DG has been investigated. The size of a single DG is 4MW and fed to the grid as backup when there is power interruption. Reliability analysis based on simulation studies carry out by DIgSILENT Power Factory Software. Holeta feeder was studied to investigate the effect of DG at the end line to reliability. From the simulation, SAIFI and SAIDI of this feeder without of DG are 291.99 interruption per customer per year and 195.63 Hour per customer per year respectively. With DG option at the end of the line, the simulation result shows that the SAIFI and SAIDI of this feeder improved to 91.16% and 91.16% respectively.



Distribution Network, Distribution System, Distribution Generation (DG), Availability, Feeders, Distribution Faults & Others, Reliability Analysis