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

Qualified coordination between over-current and distance relays in power transmission systems is one of the important issues to the system security. To achieve this issue have proposed by earlier researches to use a proper and powerful optimization program. In this paper, the coordination of the over-current and distance relays is proposed by using an improved particle swarm optimization algorithm (IPSO). In the presented IPSO, exploration and global search capabilities of the PSO is improved by an artificial intelligence technique and a new method of updating exploration search. 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.

coordination; distance relay; IPSO; over-current relay