A voltage sag severity index considering the power system and consumer equipment

Voltage sag indices are essential for the evaluation of voltage sag effects on the power system and electric utilities, and for the improvement of power quality. In the paper, a comprehensive index is presented to describe the voltage sag severity considering the supply and consumer side simultaneously. First, the IEC 61000-2-8 table is applied to derive the statistical index of power system with the improved analytic hierarchy process. Then the utility outage probability is obtained based on a modified equipment outage model. Finally, the comprehensive index is extracted from the preceding two indices via the vector normalization method. The voltage sags are analyzed based on the power quality monitoring system installed in some city in China. Calculated results have shown that the proposed index could represent the voltage sag severity of given monitoring sites more explicitly, which is beneficial for the improvement of power quality and supply reliability.