Analysis of Frequent Power Cut on Ugbowo 2x15MVA, 33/11kV Electric Power Distribution Network Feeders

Received 15 August 2020 Revised 19 August 2020 Accepted 20 August 2020 Available online 31 August 2020 This paper investigates the frequent power cut on the 11kV feeders of Ugbowo 2x15MVA, 33/11kV electric power distribution network. Annual data of daily power outages from August 2019 to July 2020 of the 11kV feeders were collated and collected from the Ugbowo distribution network. The daily outages of the 11kV feeders were used to compute the monthly and the yearly reliability indices of the feeders of the Ugbowo distribution network. Both the monthly and annual failure rates, MTTR, MTTF, MTBF, availability and unavailability were computed and analyzed using the Load Point Indices (LPI) and the Microsoft Excel was used for graphical interpretation in order to estimate the reliability indices and to determine the frequency of power outages of the network. Also, the Performance Indices (PI) of the system were evaluated for an in-depth assessment. The annual and monthly failure rates, mean time to repair, mean time to failure, mean time between failure, system average interruption frequency indices (SAIFI), system average interruption duration indices (SAIDI), average service availability index (ASAI), etc for a period of twelve (12) months were analyzed. The computed results obtained from the analyses of the 11kV feeders of the distribution network showed that the power unavailability is very high for the period under study with Ugbowo 11kV feeder having the highest power unavailability of 76.52%, Eguaedaiken 11kV feeder 73.42%, FGGC 11kV feeder 69.50% and Uselu 11kV feeder 66.96% in the network. The annual failure rate results revealed that Ugbowo 11kV feeder has the highest failure rate of 46.52%, followed by Eguaedaiken feeder 44.83%, FGGC feeder 44.27% and Uselu feeder 41.60%. This is due to frequent power outages resulting from regimented load shedding (scheduled outages) being practice in the network as way to manage equipment limitations, poor energy management system, etc. and unscheduled (forced) outages due to faults in the network. Furthermore, the PI of the system revealed that the annual total outage duration (SAIDI), outage frequency (SAIFI) and percentage availability (ASAI) were 175.7504hours, 3.3780f/cu.yr and 97.99% which is a far cry from the international acceptable standard value (IASV) of 2.5 hours, 0.01 and 99.99% respectively which showed that the power supply services in the network is unreliable.