In the conventional protection system of the distribution system in Korea, modified International Electrictechnical Commission (IEC) curves and curves developed by Korea Electric Power Research Institute (KEPRI) have been used. The use of such mixed curves causes the protective coordination system to malfunction. It is argued that this malfunction must be corrected for the protection coordination system of the domestic distribution system, and the only one unified international standard IEC curve should be used for this. And in case of fuse, it is installed only in single phase in Korean distribution system. Therefore, the rated current is so small that it does not suitable for protective coordination. Therefore, in this paper, we describe the results of the coordination of Epoxy Fault Insulator (EFI), which replaces the fuse with the unified very inverse curve of IEC. A protective coordination simulation which simplified the protection system of the Korean power system is conducted through Electrical Transient Analyzer Program (ETAP). The simulation results show that each protective device follows the protective coordination rules within the prescribed rules.

Distribution system,Epoxy Fault Insulator,ETAP,IEC curve,Protective Coordination