Estimation of sensitive equipment disruptions due to voltage sags

This paper presents a method for predicting the number of equipment disruptions due to voltage sags in a unit of time based on a concept described in IEC 61000-3-7. The proposed method uses the probabilistic distributions of system disturbance and equipment immunity indices obtained from a unified fuzzy inference engine to represent the disturbance severity and equipment susceptibility of voltage sags. It takes stochastic behavior of service performance into account in the estimation of equipment disruption. The proposed framework is also applicable if other power-quality indices, such as the voltage sag energy index and voltage sag severity index, are adopted. It can be used as an alternative for performing voltage sag coordination and financial analysis.