Analysis of Criteria for Overreaching Zone Settings in Distance Protection for Dense Systems with High Penetration of Inverter-Based Resources

Distance protection schemes are increasingly constrained by reduced system inertia, the presence of harmonics, subharmonics and interharmonics, and the difficulty of ensuring reliable backup protection for faults on adjacent lines and equipment. In highly meshed networks, where nearby transmission lines may significantly differ in length and electrical characteristics, these factors collectively complicate traditional protection philosophies. When fault current contributions from remote terminals differ in magnitude and / or phase, distance relays perceive an apparent impedance displaced from the true fault location.

Disturbance analysis and a comprehensive set of simulated scenarios revealed that, due to the difficulty in obtaining ideal IBR models and the high system density of the system, conventional criteria for defining distance overreach settings have become significantly more complex.

The growing difficulty in defining appropriate backup zone settings, together with the absence of consolidated methodologies, highlights the need for more detailed, case-specific approaches.

This paper investigates performance limitations arising from the difficulty of setting up overreaching backup zones, explores traditional techniques, their limitations, and the potential risks of miscoordination. The study emphasizes the need for collaboration among utilities and the development of adaptive intelligent protection schemes to ensure system reliability amidst the evolving generation scenario.