A microgrid protection scheme using differential and adaptive overcurrent relays

This paper proposes a hybrid adaptive overcurrent and differential protection scheme to deal with the drastic changes in microgrid short circuit current characteristics following shifts between grid and islanded operational modes. The scheme proposes using adaptive overcurrent relays to protect individual load points or feeders while using differential relays to protect load buses or backbone feeders in order to reduce infrastructure upgrade requirements and setting computation complexity. In the context of this paper, multiple time-domain simulations are conducted to determine the efficiency of the proposed scheme in protecting a microgrid network while operating in grid or islanded modes. Time domain simulations for validation purposes have been conducted using a typical microgrid test network in the EMTP-RV software environment.