Duty cycle effects on generating unit availability

The author presents and discusses unit reliability models and unit failure rates as functions of unit duty cycle. The duty cycle experienced by a generating unit has an important effect on the unit´s failure rate and on the probability that the unit is available when needed. Consequently, unit duty cycles should be considered and properly modeled in studies of system capacity requirements and benefits. Unit failure modes that are associated with stop/start events are discussed. A sample system study is used to illustrate how the effects of generating unit duty cycles on failure rates and availabilities of generating units in a system influence system reliability and capacity requirements. This study shows that ignoring the effects of duty cycle on unit failure rates can seriously degrade the accuracy of the study