LAUSR

Protection coordination for the microgrid system in both islanded and grid connected modes is considered a challenge for microgrid operation. The variation in short circuit currents in each mode of operation, limitation of protection curves in the relays, and the need for fast and reliable communication are the main challenges tackled in research. Direction overcurrent relays are considered the main protection instrument for the microgrid. However, one protection setting for both (main and backup) operation does not provide a fast-operating time. On the contrary, the dependence on communication to maintain the proper backup protection operation is not a reliable solution for protection system. Therefore, this paper introduces a fast, reliable, and simple protection scheme for secure microgrid operation in both islanded and grid connected modes. In this context, one set of protection settings is optimized and used in both modes of operation. A protection setting consists of two time-dial settings and one pickup current setting for each relay. The proposed design technique minimizes the total operating time for both main and backup relays. As all protection functions are executed in the forward direction, no communication is needed among relays. The proposed scheme is tested and verified on a modified portion of IEEE 30 bus test system equipped with distributed generation units. A comparative analysis is carried out and the results demonstrate superior performance by the proposed scheme in comparison with the dual setting scheme with communication.