Optimal Coordination of Directional Overcurrent Relays using Particle Swarm Optimization Technique

The main function of the protective devices in the power system is to detect and remove the selected faulty parts as fast as possible. Directional over current relays are commonly used for the protection of interconnected sub transmission systems, distribution systems, or as a secondary protection of transmission systems. For the systems having more than one source connected, that is meshed or looped networks, directional over current relays become the suitable choice for better selectivity, since directional relays operate only when the fault current flows in the specific tripping direction desired. The most vital task when installing directional relays on the system is selecting their suitable current and time settings such that their fundamental protective functions are met under the requirements of sensitivity, selectivity, reliability and speed. The problem of setting Directional Over Current Relay(DOCR) is a highly constrained optimization problem that has been solved as a linear programming problem. The