Failure Probability Analysis of Sensitive Equipment Due to Voltage Sags Using Fuzzy-Random Assessment Method

The impact of voltage sags on equipment is usually described by equipment failure probability, and it is in general very difficult to assess and predict because of uncertainties with both the nature of voltage sags at the power supply side and the voltage tolerance level of equipment. By defining the equipment failure event caused by voltage sags as a fuzzy-random event, a fuzzy-random assessment model incorporating those uncertainties is developed. The model is able to convert the probability problem of a fuzzy-random variable to that of a common random variable with the use of -cut set and it is thus valuable in theoretical analysis and engineering application. The validity of the developed model has been verified by Monte Carlo stochastic simulation using personal computers as the test equipment.