Prevention of overcurrent relays miscoordination in distribution system due to high penetration of distributed generation

The introduction of distributed generation (DG) units provided an opportunity to enhance the reliability of distribution networks. However, it is expected that DG contribution in fault current can affect existing protective devices, especially overcurrent relays (OC) coordination. The system reliability can deteriorate when protective devices lose their coordination and the problem is more complicated in case of high penetration of DG units. Accordingly, in this paper a protection coordination scheme is proposed to prevent the reliability degradation from OC relays miscoordination. The description of the proposed method is tested by evaluating the reliability indices of a radial distribution test system. The results verified the effects of proposed coordination strategy on improving the reliability indices of the test system.