The Measure of Customer Equipment Failure Event Due to Voltage Sag

An effective evaluation method of sensitive equipment failure event in customer side is proposed. In this method, the voltage sag severity and maximum entropy principle are used to present the voltage sag severe degree and its probability distribution. The voltage sag duration and magnitude with certain physical performance are converted to severity indices namely sag duration severity index (DSI) and voltage magnitude severity index (MSI). Based on maximum entropy principle, the probability distribution functions of sag severity indices are calculated without any assumption. Cumulative summing method is used to determine the probability of customer equipment failure event. As a case study, the personal computer is simulated and the results show that this method is reasonable and accurate.