Relay Coordination Scheme in Microgrids Based on Non-Standard Tripping Curve of DOCRs With Multiple Setting Groups

The coordination of directional overcurrent relays (DOCRs) gets affected upon variation in microgrid mode of operation. The changes in distributed generations (DGs) penetration level, distribution line or DG outages significantly imposes difficulties on the performance of DOCRs coordination. The proposed protection coordination scheme is designed by considering N-1 contingency conditions that can result in single DG outage, line outage, and substation outage conditions. The proposed scheme is tested on the nine bus Canadian benchmark system to validate the effectiveness. The proposed method obtains the optimal setting of the relays in the offline mode using a new metaheuristic technique called wild horse optimizer, and the working steps to execute the proposed approach in real time environment are demonstrated. Further, the user defined or nonstandard tripping characteristics for the DOCRs have been proposed, which enhances the coordination among relay pairs. All the important network topologies are designed into several setting groups or clusters suitable for modern numerical relays to adaptively change upon variation in network conditions. The performance of the proposed scheme is compared with the standard relay characteristics scheme and validated in real-time digital simulator environment using both synchronous and inverter-based DG to demonstrate the potential ability of the proposed protection scheme for reliable protection measures in microgrids.