Fuzzy inference supported current differential protection for HV transmission lines

In this paper enhanced differential current protection scheme dedicated for HV transmission lines is described. The adaptive fuzzy relay scheme is proposed that combines strengths of both current and phase comparison protection criteria. The relay stabilization characteristic is adapted online depending on the output of the fuzzy reasoning scheme supplied with information from the phase comparison unit. As a result improved performance of the scheme for cases of external faults with CT saturation is reached. The performance of presented fuzzy protection scheme has been tested with the signals generated with use of EMTP-ATP program and compared to the traditional solutions.