Effect of Partial Outage Representation in Generation System Planning Studies

Large size thennal units are subject to a number of partial outages due to their multitude of components and auxiliaries. These derated states should be correctly included in the generation system capacity outage probability model. Virtually all static capacity planning studies utilize a binary representation of the generating units. Any type of approximation; representing partial outages as full outages, neglecting partial outages or an equivalent forced outage rate EFOR can result in significant error. This paper investigates the quantitative effects of accurate derated and approximate EFOR representation on the possible expansion of a generation system.