Innovative Adaptive Protection Approach to Maximize the Security and Performance of Phase/Earth Overcurrent Relay for Microgrid Considering Earth Fault Scenarios.

Microgrids are increasingly paying attention to the emerging of distributed energy resources. However, microgrid protection has challenged engineers because of the varying nature of fault current distribution during grid-connected and islanded operations. This paper suggests a novel approach of coordination between phase and earth fault overcurrent relays to ensure stability and security for the performance of protection schemes in active distribution networks. In this study, a combination of phase and earth overcurrent relays is coordinated to avoid mis-coordination in the overcurrent protection schemes. In the proposed approach, phase overcurrent function was employed as backup protection for earth fault function locally in the same relay instead of the traditional remote backup earth fault protection coordination approach. The suggested coordination approach provides a fast and reliable protection performance in different earth faults scenarios. The coordination was tested on the IEC Microgrid Benchmark network. Also, the objective function was modified to reduce the overall operational time using two recently developed metaheuristic optimization algorithms known as the charged system search (CSS) and Teaching-Learning-Based Optimization Algorithm (TLBO) in the MATLAB package. Finally, the time multipler setting values were adapted and compared to verify the speed and reliability of the proposed coordination approach using ETAP.