Wavelet‐based approach for high impedance fault detection of high voltage transmission line

This paper presents a new method for high impedance single‐phase ground fault (HIF) detection based on wavelet transform (WT) in the high voltage transmission line. As high impedance single‐phase ground faults usually have low fault currents, it cannot be easily detected by the conventional protection. The voltages and currents vary simultaneously when a ground fault occurs in the transmission lines, even if it is grounded with a high impedance. Therefore, the signals measured by the protective device contain significant transient components. They have much more fault information than the steady components. With the WT the modulus maxima of the zero sequence current, the faulted phase current, and the zero sequence voltage present special characteristics which can be used to detect HIF. The new scheme can also discriminate if the ground fault locates in the forward zone or the backward zone. The realization of the proposed protection device is also described in this paper. Both simulation and field results show that the scheme can detect HIF with high reliability during all operating conditions.