Mahmood Sadoughi - Department of Electrical Engineering, Islamic Azad University, Ferdows, Iran
Morteza Barkhi - Department of Electrical Engineering, Islamic Azad University, Gonabad, Iran
Poyan Porreza - Department of Electrical Engineering, Islamic Azad University, Ferdows, Iran
Amin Ekrami - Department of Electrical Engineering, Islamic Azad University, Ferdows, Iran
Maryam Sadoughi - Department of Electrical Engineering, Islamic Azad University, Ferdows, Iran
Parisa Moghimi - Department of Electrical Engineering, Islamic Azad University, Ferdows, 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 ۶-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