Abdol-rahim kami - lecturer ۱ University of applied science and technology, UAST Tehran, Iran
Michael Noorani kalteh - Instructor ۲ Fakhrodin institute of higher education Gorgan, Iran

Proper coordination between different relays in power transmission systems is one of the important issues to the system security. To achieve the best and optimal relay coordination is necessary and essential to use a powerful optimization program. In this paper, the over-current and distance relays arecoordinated through an improved particle swarm optimization algorithm (IPSO). In the presented IPSO by an artificial intelligence technique similar to the commonly used genetic algorithm (GA) exploration and global search capabilities of the PSO is improved. The proposed method is investigated on a 6-bus IEEE system. It is shown that IPSO has better results in comparison with PSO and GA algorithm.

distance relay; IPSO; over-current relay