Design and Optimum Overcurrent Relay Coordination for Ring Main Distribution System

Abstract

In a distribution network, there are mainly primary distribution system (11kV) and secondary distribution system (440V). On the primary distribution side radial feeder topology is generally establish with overhead lines. Now a day, this topology is converted to ring main system by introducing Ring Main Units (RMU) for the protection of distribution system. RMU's are used to provide multiple power sources to the load maintain continuity of power supply at the time of fault. The main problem in ring main system is relay coordination because many relays are present in the system for protection purpose. If relays are not coordinated properly, mal-operation, instantaneous tripping, cascade tripping may result in such system configuration. Hence, it is required to design proper relay coordination to reduce these types of problems.