Duty cycle effects on generating unit availability

The author presents and discusses power station unit reliability models and unit failure rates as functions of unit duty cycle. The effect of the duty cycle experienced by a generating unit on the units failure rate and on the probability that the unit is available when needed is shown to be significant. Consequently, it is argued that unit duty cycles should be considered and properly modeled in studies of power system capacity requirements and benefits. Unit failure modes which are associated with stop/start events are discussed. A sample power system study is used to illustrate effects on system reliability and capacity requirements. The study shows that ignoring the effects of duty cycle on unit failure rates can seriously degrade the accuracy of the study.<>