Benchmarking utilities for the impact of voltage sags on customers

Most utilities have increased their focus on voltage sags as the sags account for vast majority of recorded equipment trips. Although these events are not necessarily the most frequent, they have a tremendous economic impact on end-users. The process of benchmarking customer voltage sag levels generally requires voltage sag monitoring data for a period of minimum one year. This data can then be quantified to relate voltage sag performance with standardized limits for acceptable performance. This paper suggests a methodology for benchmarking the impact of voltage sags on customers of different utilities by means of a three stage reporting procedure that covers a site, a network and a utility. This is followed by a simple method of defining a single sag index for a utility that deals with the average values across the utility which enable comparison of different utilities for their overall sag performance.