Overcurrent and Earthfault Relay Coordination for Microgrid with Numerical Relay Features

Abstract

This Paper deals with the Relay Coordination for microgrids by considering the symmetrical and unsymmetrical faults. A microgrid is an active distribution system in which the renewable energy sources and loads connected to feeders operate parallel or autonomously from the main power grid. In a microgrid, Overcurrent relays can be used as the protection device. When there is changeover from grid connected to islanded mode or disconnection of DG will lead to variation in short circuit current. So, the relay may fail to operate or there will be delay in operation. Relay Coordination is done on the basis of load flow and short circuit analysis. Simulation is done using the ETAP (Electrical Transient and Analysis Program) Software by taking the 9 bus 18 node system.