Test and analysis on sensitivity of low-voltage releases to voltage sags

This study discusses the sensitivity (i.e. ride-through performance) of low-voltage releases to voltage sags on the basis of extensive tests, and presents two sensitivity models to assess the tripping characteristics of low-voltage releases, which have not been studied before. First, working principle of low-voltage release and existing standards are reviewed. Second, a detailed test scheme is proposed and ten kinds of low-voltage releases have been tested. Test results show that magnitude, duration and point-on-wave angle of voltage sag jointly determine the sensitivity of low-voltage releases. After extremely processing test results and applying the curve fitting theory, the functions representing the relationship between magnitude and duration at different point-on-wave angles are formed, which symbolise a detailed sensitivity model of low-voltage release. Moreover, the other simpler and more practical sensitivity model is proposed by introducing rectangular envelope lines of voltage tolerance curves at different point-on-wave angle.