Underground low voltage loop system of KEPCO

Abstract

KEPCO has adopted radial system at low voltage distribution. Recently KEPCO began to have the problems. As low voltage customer's limit was changed from 499 kW to 999 kW, the uses of large capacity transformer are increased. Installation space of TR & CB are insufficient at downtown area. Utility rate of transformer is low. When transformer is replaced, LV system experiences interruption. So we developed the underground low voltage loop system. KEPCO's LV loop system is consisted of HV CB, TR, LV loop IED, LV CB, operation system (server). To develop the low voltage loop system, we simulated the load flow and fault analysis by EMTDC program, made a simulator for lab test, developed the protection coordination and established test bed at 22.9kV network. And field test was done.