Optimal coordination of over current relay using opposition learning-based gravitational search algorithm

In this paper, the optimum coordination of over current relay in distribution system has been performed. The time dial setting (TDS) of over current relay is optimized by minimizing total operating time of relays. As the power system is a complex and highly interconnected, the complexity may be occurred in calculating optimum relay coordination time (TDS, phase setting etc.) by conventional or analytical methods. Therefore, an opposition learning-based gravitational search algorithm (OLGSA) is proposed for relay coordination optimization problem. The proposed optimization method can search the optimum solution for relay coordination problem from both the direction (initial populations and their opposite direction populations) in search space to reach global solution as early as possible. Three different distribution power systems are considered to verify the performance of the proposed algorithm for optimum relay coordination problem. The simulation results for all three cases have been compared with existing results. The outcome of the proposed method for relay coordination problem shows that the total relay operating time is minimized (20-40 % improvement in relay total operating time for different cases) comparably than available results for all three cases by maintaining coordinations among relays and satisfying different constraints.