Optimal coordination of over-current relay with Distributed Generation consideration

Utilizing Distributed Generation (DG) is greatly increasing in recent years. This is mostly because of simple installation, environmental effects and loss reduction due to closeness to the load centers. However, DG installation, especially in distribution networks, raises some problems. One of these problems is over-current (OC) relays coordination. In this paper, DGs´ effects on OC relays in distribution network are studied. An IEEE 8-bus standard system is simulated in MATLAB software. A new method is proposed to optimize the operating time of OC relays in such a way that using DGs in any bus will not affect on the main and backup protection relays operation and coordination. In this method, optimized relays settings are obtained by linear programming approach.