Impact of Interruption Duration on Cost of Unserved Energy: A Survey Based Study for the Commercial Sector in Sri Lanka

The cost of unserved energy is a parameter used to calculate the worth of electricity that is not served by a power system due to planned and unplanned outages. This figure is influenced by several factors such as affected group, duration of interruption, time of interception, etc. This paper studies the impact of interruption duration on the cost of unserved energy experienced by the consumers in the commercial sector. The study is based on a consumer survey conducted to gather the data required from the consumers belong to 15 subcategories. Using the collected data, average and weighted average cost of unserved energy due to expected and unexpected outages corresponding to 5 outage durations are computed. Results are analyzed and identified patterns in variations are discussed. The analysis reveals that the cost of unserved energy due to unexpected outages of most subcategories is high for short outage durations, when compared to that of long outage durations. Whereas, the cost of unserved energy due to expected outages gradually increases with the interruption duration. Thus, this study reveals that the cost of unserved energy shows different variations with the interruption duration for expected and unexpected outages.