Optimal coordination of directional overcurrent relays in the presence of distributed generation using FCLs

The penetration of distributed generations (DGs) would drastically affect traditional power system fault current level and the characteristic of fault current, consequently affect on coordination of over current relays. Implementation of fault current limiters (FCLs) to locally limit the DG fault current, could somewhat overcome with this problem. Kind and value of FCLs must be chosen by considering from an economical standpoint. Also connecting and disconnecting DGs to the power system according to network operating scheduling or other reasons make power distribution system (PDS) topology time varying and so optimal coordination of DOR will affect. In this study a new approach is proposed to solve these problems of PDS in the presence of DGs. In the proposed approach, settings of relays are chosen based on minimizing a new cost function that assume value of FCLs to be zero, If stopping criteria is satisfied, optimization is done and algorithm will finish. otherwise, the value of FCLs will raise and the algorithm will repeat until sopping criteria satisfy.