Voltage sag immunity factor considering severity and duration

This paper presents an application of fuzzy logic technique to quantify the equipment voltage sag immunity level. It describes the fuzzy sets and IF-THEN inference rules involved in a process of providing an equipment immunity factor based on equipment voltage tolerance test data. Typical voltage tolerance envelopes, such as IEEE Std. 446 and CBEMA curves, are exploited in defining the fuzzy membership functions corresponding to various classes of voltage sags severity and durations. Using the equipment voltage sag tolerance test data, the proposed fuzzy reasoning process provides a single factor that represents the relative immunity level of the tested equipment. Previous voltage tolerance data of personal computers are used to test the proposed method and the immunity factors distributions of the tested equipment using various fuzzy rules are presented.