Abstract- High impedance faults (HIFs) are difficult to be detected by overcurrent protection relays

High impedance faults (HIFs) are difficult to be detected or classified by overcurrent or distance relays. This paper presents a scheme for high impedance fault detection and classification in extra high voltage transmission line. The scheme recognizes the distortion of the current waveforms caused by the arcs usually associated with HIF using a discrete wavelet transform (DWT) based pattern recognition. The scheme uses a recursive method to sum the absolute values of the high frequency signal generated of line current signals measured at one substation end over one cycle. Proposed detector and classifier are tested under a variety of fault conditions on Egyptian 500KV transmission line system by extensive simulation studies using HIF model of distribution system that modified to transmission lines. In addition, a real time HIF data recorded is used to validate the performance of the proposed scheme. All achieved results clearly reveal that the proposed scheme can accurately detect and classify HIFs in the transmission lines unaffected by fault type, fault inception angle, fault resistance, and fault location. Index Terms – High impedance faults (HIF), fault detection and classification, Wavelet Transform, Transmission line.