Advanced Three‐Level Characteristic of Overcurrent Relays Based on Non‐Standard Characteristic for Enhanced Microgrid Protection

The growing integration of distributed generations (DGs) and the islanding capabilities of microgrids (MGs) have fundamentally changed the configuration of power distribution networks (DNs), significantly impacting short‐circuit current levels and thereby, challenging the reliability of conventional protection systems. The increasing complexity of modern power networks necessitates the adoption of more than two setting groups to manage various network scenarios and multiple fault levels effectively. This research introduces an advanced three‐level overcurrent relay (OCR) protection scheme, based on a non‐standard characteristic, for MGs and comprehensively evaluates it across different grid operation modes. The study specifically examines the following power grid configurations: A 33‐IEEE grid without DGs (PV or wind), a grid incorporating a photovoltaic (PV) unit, and a grid featuring a wind unit. Experimental results from the 33‐IEEE grid demonstrate that the proposed three‐level OCR scheme reduces total tripping time by over 40%, thereby, enhancing fault sensitivity and enabling faster fault isolation. This, in turn, minimises disturbance duration and the risk of faults that could lead to significant system damage. For instance, in the case involving a PV unit at fault location F6, the three‐level scheme decreased the tripping time of OCR 6 from 1.52 to 0.97 s, underscoring the scheme’s high performance in fault management. Furthermore, experimental testing is utilised to evaluate the three‐level OCR scheme in real‐time, employing the OMICRON‐256 and SIPROTEC 7SJ631 protection relay. The findings suggest that the proposed OCR protection scheme represents a significant advancement in MG protection, offering a scalable and robust solution for future power distribution systems.