Impacts of repair state residence time distributions in an electric power generating capacity adequacy assessment

The primary function of an electric power system is to satisfy the load requirement as economically as possible with an acceptable assurance of continuity and quality. A generating capacity adequacy evaluation involves the determination of the total system generation required to satisfy the load requirement. In these studies, a generating unit is usually represented by a two-state model in which the unit is either available or unavailable for service. These models are valid representations for base load units but do not adequately represent intermittent operating units used to meet peak load conditions. The two-state model for a base load unit has been extended to a four-state peaking unit model that is widely used in practice. The generating unit state residence time distributions in these models are assumed to be exponential in form in virtually all practical system studies. This may not be a valid assumption for the repair state in some situations. A sequential Monte Carlo simulation technique is utilized to incorporate Weibull distributed generating unit state residence times in the two-state and four-state models. The effects on the adequacy indices and the adequacy index distributions are illustrated by application to two practical test systems.