Improvement of Overcurrent Relay Coordination in Isolated Distribution System Using Grasshopper Optimization Algorithm

Abstract

The increasing penetration of distributed generation (DG) has raised short-circuit current levels, potentially affecting the coordination of overcurrent relays (OCRs) used for distribution network protection. To address this issue, this study applies the grasshopper optimization algorithm (GOA) to optimize the time dial setting (TDS) with the objective of minimizing the total operating time of main relays while satisfying the required coordination time interval (CTI) constraints. The optimization results are compared with those obtained using particle swarm optimization (PSO) for three IEC standard inverse-time characteristics, and the selected characteristic is validated using ETAP simulations. The optimization results show that the Extremely Inverse (EI) characteristic achieves the minimum total main relay operating time of 3.0780 s while maintaining the minimum CTI requirement of 0.20 s. Furthermore, GOA produces optimization results comparable to PSO, with differences of less than 0.3% across all tested characteristics. These findings indicate that GOA is an effective alternative for improving OCR coordination while maintaining the required CTI standards.