Modeling of combined cycle units in probabilistic production costing models

To simulate the economic operation of a power system, production costing models utilize the multi-block representation of the conventional units. Each capacity block of a conventional thermal unit is described by a two-state reliability model. In this paper a reliability model for combined cycle units is proposed. With the model proposed a combined cycle unit consisting of N gas turbines and a steam generator can be represented by N blocks, each of which corresponds to the various operating levels of the unit. For each operating block a multi-state reliability model is proposed, in order to take into account the partial failures of the unit when required to operate at that level, taking into consideration the forced outage rates of the gas turbines and the forced outage rate of the steam generator.