Novel approach for optimum coordination of overcurrent relays to enhance microgrid earth fault protection scheme

Ground faults are the most common type of faults in the microgrid. In addition, the configuration of the grounding strategy significantly affects the characteristics of the ground faults response and intensity. Consequently, affecting insulation specifications, equipment safety, and protection requirements. Therefore, extensive knowledge of the grounding strategies used is a significant and prominent factor in the protection of the microgrid. In this study, a new different objective function (OF) has been suggested for overcurrent relay (OCR) coordination based on combining the phase and earth overcurrent protection functions in the formulation of OCR coordination problem. Converse to the traditional coordination strategies in the literature review which depends on the phase OCR function in solving the OCR coordination problem, this approach merges the phase and earth OCR functions to ensures selectivity and speed in isolating all ground and phase faults currents and avoid sympathetic tripping situations. Also, this paper proposes an optimal and single protection scheme suitable for all type of faults based on a single line to ground fault calculations. A new optimization algorithm based on an evaporation rate water cycle algorithm (ER-WCA) is used. A modified IEC microgrid benchmark network implemented in ETAP to investigate the effectiveness of the proposed new approach to enhance the constrained optimization technique.