NEW PRINCIPLE OF SINGLE-PHASE-TO-GROUND FAULT PROTECTION FOR FEEDERS BASED ON THE PHASE ASSOCIATED FEATURE OF PHASE TRANSIENT CURRENT
Miao Youzhong, Sun Yarning (Tianjin University, Tianjin 300072, China)
The faulty phase transient current component (TCC) of faulty feeder is composed of the healthy phase TCCs of all feeders including the faulty one, and then a combinatorial complex wavelet transform (CCWT) sequence is formed in every phase of the faulty feeder, which will lead to relative associated features of magnitude and argument between the phases when single-phase-to-ground fault occurs in the distribution network. First a new principle of single-phase-to-ground fault protection for the faulty feeder is proposed by extracting the equivalent band phase features between the phase CCWT sequences and regards it as the protection criterion. A risk coefficient is introduced into this criterion to eliminate bad data in the CCWT sequences. It has been verified by ATP simulations that the protection principle proposed can correctly distinguish single-phase-to-ground fault and is highly reliable, sensitive and adaptable without the need for setting calculation and is used for all kinds of distribution systems. This kind of protective mode can be merged with the gap units and conveniently realize the disposable auto-reclosing mode to greatly enhance the reliability of power supply.