Assessment of system voltage sag performance based on the concept of area of severity

This study presents a new approach for voltage sag assessment based on the concept of 'area of severity' (AOS). The network regions, where the fault occurrences will simultaneously lead to voltage sags at different sensitive load points, can be determined by performing an AOS analysis. The impact rankings of the network lines and buses are also addressed. The impact rankings are determined according to the contribution degree of each line and bus faults to the total expected number of voltage sags in the power system. The concepts of AOS and the impact ranking are useful in establishing efficient planning for the mitigation of voltage sags, and for evaluating the relationship between sensitive load points and system voltage sag performance.