Research on the novel comprehensive fault line selection method for the NUGS based on the fuzzy theory

Because of line parameters, running types, fault grounding impedances and other factors, the veracity of current fault line selection (FLS) method is not high enough and may contain some dead areas for FLS device of non-utility grounding system (NUGS). To overcome this shortage, a novel FLS method is proposed in this paper based on analyzing the fault characters of distribution network, combining merits of prevalent FLS methods, constructing these methods´ subjection functions and then synthesizing them based on the fuzzy theory. Experiments show this method can achieve high sensitivity, adjustability and veracity. The dynamic simulation experiment shows in the neutral un-grounding system(NUS), the method which is made of the zero sequence inactive power (ZSIP) method, the base-wave virtual value (BV) method and the base-wave phase (BP) method of zero sequence current (ZSC) can achieve high accuracy; in the neutral resonant grounding system (NES), the method that combines zero sequence active power (ZSAP) method, 5-harmonic phase (HP) method and remaining current increment (RCI) method can even achieve 100% accuracy. Based on the PC104 industry control computer, a new FLS device of NUGS according to this new FLS shows very high accuracy in dynamic simulation experiments, and it should be widely used in China.