ABRUPT CHANGE DETECTION WITH WAVELET FOR SMALL CURRENT FAULT RELAYING

A novel method for single-phase-to-ground fault relaying is presented in this paper. In this method, singularity detection with wavelet is employed to obtain the polarities and magnitudes of the abrupt change of voltage and current caused by the fault, and through comparing the polarities and magnitudes the fault circuit can be determined. This method is not only immune from the moment when a fault occurs and the condition whether a Peterson coil exists or not, but also more bearable to interference. EMTP simulations and field tests verified the effectiveness and practice of the proposed method.