Minimization of the discrimination time between the backup and main overcurrent relays is one of the most important issues in the relays coordination of a power system. Finding the Time Setting Multipliers (TSMs) by the evolutionary algorithm has been investigated in the previous papers. In this paper, in addition to TSM, different characteristics of the overcurrent relays are considered to improve coordination. On the other hand, the coordination problem can be considered as an optimization problem, which can be solved by artificial intelligent methods. Recently, a novel optimization algorithm, Hyper-Sphere Search (HSS) algorithm, has been introduced. The HSS algorithm is adapted to the problem of this paper, in order to select the characteristics of the overcurrent relays and their TSMs. The result of HSS is compared with the genetic algorithm which is used in the previous studies. The simulation results on the sample network show the effectiveness of HSS and relays characteristics in terms of better coordination.
