Assessment of electric service reliability worth

The basic function of a modern electric power system is to satisfy the system load and energy requirements at the lowest possible cost, while maintaining an adequate degree of continuity and quality of supply. Establishing the worth of service reliability is a difficult and subjective task. Direct evaluation is not considered feasible, and an approach that is evolving is to evaluate the impacts and monetary losses resulting from electrical supply interruptions, which is, in effect, the societal cost of unreliability. These interruption costs are not considered equal to the reliability worth, but merely a surrogate of it. The authors provide a survey of the range of methods used to evaluate reliability worth or costs of unreliability (outage costs) as reported in the literature. The general evolving trends of the various methods are summarized and the customer postal survey method is identified as the method preferred by utilities