The issue of ensuring selective and reliable earth faults in modern microgrids still persists due to sympathetic zero sequence currents and multi-source coupling complexities. In this paper, the customized Earth Fault Protection (EFP) logic has been formulated and tested to successfully discriminate between true in-feeder Earth faults and other non-fault sympathetic currents within the AC microgrid environment modeled in MATLAB/Simulink. The customized logic utilizes the dual-threshold strategy with residual current (I？) and the minimum phase current (Imin), further bolstered by time-blocking action to prevent unwarranted operations. The simulation results indicate that the customized protection logic provides complete immunity to false operations during sympathetic I？ currents. Yet, it also manifests sensitivity to low-intensity internal faults if the stationary Imin threshold is unexceeded. The customized solution compares favorably with the state-of-the-art in terms of simplicity, understandability, and direct realizability without requiring heavy computations through artificial intelligence frameworks such as ANFIS topology-independent models and AI-powered microgrid fault detection techniques.
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