Optimal coordination of overcurrent and distance relays with hybrid genetic algorithm

To achieve better protection, it is common to use both distance and overcurrent relays as main and backup relays respectively, in power transmission protection scheme. In this situation it is necessary to coordinate these two types of relays simultaneously that makes the problem harder to find a global optimal point. To overcome the complexity, it is a good idea to use an optimization algorithm like (GA) to perform coordination between distance and overcurrent relays. In this paper, a hybrid algorithm based on GA and linear programming (LP) is proposed to obtain the relay settings which are Time Multiplier Setting (TMS) and I_set for overcurrent relays and Second Zone Time (T_z2) for distance relays. By this assumption, new variables are added to the problem and size of search space will become bigger, thus finding the global optimal point will be harder. It is shown that the proposed hybrid GA can find a better solution in comparing to the conventional methods.