RELIABILITY ASSESSMENT AND MITIGATIONS FOR JIGJIGA CITY ELECTRIC POWER DISTRIBUTION SYSTEM, ETHIOPIA

Abstract

The power system is a network made up of a generation, transmission and distribution system. The distribution system reliability for electricity is one of the most criteria for determining how effectively the power system can reliably distribute electricity to the load. Customers must receive energy from distribution feeders consistently because the reliability of the electric power distribution system is a primary concern for any electric power utility provider. Power utility companies are implementing numerous techniques to deliver reliable power. This thesis evaluates the Lefessa 15 kV distribution feeder, one of the feeders that distributes electric power to Jigjiga City, for its reliability as a distribution feeder of electric power. Power interruption data on daily basis for a period of two years on the feeder was collected and analyzed for the main causes of interruptions wind, open section, tree contact, line loaded, maintenance and operational practices. Based on the data collected, the exiting distribution system reliability indices System Average Interruption Frequency Index (SAIFI), System Average Interruption Duration Index (SAIDI), Average Service Availability Index (ASAI), Average Service unavailability Index (ASUI), Expected energy not supplied (EENS), and Average energy not supplied (AENS) of the feeder were calculated using analytical method and simulation. The obtained results are 365.5 f/customer. yr, 548 hr/ customer. yr, 0.94 pu, 0.06 pu, 2,663 MW hr / yr, 25.362 MW hr / customer. yr and, 4,707,901.702 ETB per year loss due to power interruption respectively. The oneline diagram of Lefessa feeder-15kV existing and future distribution systems was modeled without and with reclosers, and solar PV distributed generations using ETAP 19.0.1 software and simulated differently in five cases. The results showed that, the reliability indices of existing system are beyond the Ethiopian standards and among all the cases of reliability improvement, the values of reliability indices were significantly enhanced in case 5 (three reclosers and solar distribution generator). SAIFI was reduced to 96.0840 f/customer interruptions per customer per year, SAIDI was reduced to 144.9994 hr/ customer. yr, ASAI increased to 0.9834 pu, ASUI decrease to 0.01655 pu, EENS decrease to 721.670 MW hr / yr, and finally AENS decrease to 6.8730 MW hr / customer. yr. In case 5 the utility can save revenue of 4,543,876.146 ETB/year. The installation of reclosers in distribution lines and integration of solar PV distributed generations is proposed for reliability improvement of the existing distribution system.