Abstract :
A reliability model is described which more closely simulates the states of power systems during faults than do the usual "two-state" models. This is achieved primarily by modelling the effects of comnponent failures on the system through three-state cycles, which include a state following the fault and another after the failed device is isolated, through switching, for repair. The effects of component maintenance are also incorporated. A sample study is presented, wherein the average outage frequency and duration of a small 115-kV network are calculated. The findings include the observations that, in most cases, the effects of all but the lowest contingency system failures can be neglected; and that coincidences of failures and maintenance are often more frequent causes of system outages than coincidences of faults.
