A Method to Calculate the Short Circuit Current and a Novel Protection Scheme for Cross-country Faults in Resonant Grounding System

Great fault current developed by cross-country fault in resonant grounding system (RGS) will influence the safe operation of the systems. So it is necessary to implement protection schemes when cross-country faults occur in RGS. This paper presents a novel protection scheme in terms of this fault. Firstly, the short circuit current is calculated by separating the system zero-sequence impedance. Then, a fault protection scheme is put forward to discriminate the fault feeder by using the value of short circuit currents. Finally, a method to decide which line should trip firstly in cross-country faults is proposed by using fuzzy comprehensive evaluation method. EMTP simulation results of a 10 kV distribution system show that the fault protection scheme can discriminate the fault feeder effectively. In addition, a case analysis shows that the protection scenario based on fuzzy comprehensive evaluation method can meet the selective trip decision and improve the reliability power supply.