Relay Coordination in Resilient and Sustainable Power Systems: Review on Optimization Techniques and Future Directions

This article presents a technical review of advanced relay coordination techniques in modern power systems. Focusing on directional overcurrent relays, the study examines optimization-based methods for tuning key relay parameters, which include the pickup current and the time multiplier setting, to minimize the total relay operating times and ensure reliable protection. Both deterministic and metaheuristic approaches, including various hybrid algorithms, are analyzed in terms of their ability to formulate and solve different objective functions subjected to coordination time intervals and other operational constraints. Various solutions proposed by researchers employing diverse techniques have been validated using multiple test systems and tools and comprehensively discussed. The review also highlights emerging trends in real-time adaptive protection and cybersecurity integration, providing a roadmap for enhancing the robustness of protection schemes in increasingly complex and dynamic power networks.