Uncertainty Assessment of Sensitive Equipment Failure Probability Caused by Voltage Sags

The failure probability of sensitive equipment due to voltage sag usually depends on the characteristics of voltage sags and the voltage tolerance of equipment, they are both uncertainty. It is difficult to assess and predict equipment failure probability well and truly in practical engineering. The uncertain properties both of voltage sag and equipment tolerance are considered in this paper in order to assess the failure probability of sensitive equipment due to voltage sag. The failure event of equipment caused by voltage sags is considered as a fuzzy-random event and a fuzzy-random variable is used to describe equipment failure event. A fuzzy-random model is developed and ¿-cut sets of the fuzzy-random variables are introduced also. The validity of the proposed method is proved using personal computer and comparing with the results of Monte Carlo simulation.