In directly grounded power systems, the protection relay generally gain currents enough to interpret fault if any type of grounded faults occurs. But, the fault currents can be considerably reduced by the system with high impedance or non-grounding for secure stability. For such reasons, it must be provided not only zero-sequence current but also zero-sequence voltage for increase operating stability to OCGR(Over Current Ground Relay). Because it can have direction by using measured ... 전체 초록 보기