Abstract
A stable and reliable electric power supply system is an unavoidable requirement for any country's technological and economic development. As a result, utilities must work hard to ensure that their customers' requirements for reliability are met, as well as the requirements of regulators at the cheapest price possible. Failures in the distribution system causes service interruptions. As a result, reliability worth assessments are important to consider because they allow for the inclusion of the cost or losses incurred by utilities customers as a result of power outages, which must be factored into planning and operating practices. This will allow system planners and designers to find better ways to improve the reliability of a typical single-end fed radial secondary distribution substation system. The research work is primarily concerned with the reliability assessment of a distribution system substation using an analytical method, based on outage data obtained from a utility company for a period of 5 years. The findings show that the analysis of the 11kV five feeders shows that Sabo feeder is the most reliable feeder between 2016 to 2019, while, Molipa feeder was the most reliable in 2020. The study also reveals that GRA feeder is the least reliable feeder among the five feeders.

Key words: Reliability, availability, MTBF, MTTR, distribution substation, feeders