Optimal Coordination of Directional Overcurrent Relays Considering the Impact of Distributed Generation using GA-ILP

Optimal Coordination of Directional Overcurrent Relays Considering the Impact of Distributed Generation using GA-ILP

Connecting and disconnecting of distributed generation (DG) resources and their performance in normal and is landed operational modes are the critical factors that affect theprotection coordination of over-current relays. Connecting DGs to the distribution networks could lead to the mis-coordination in over-current relays. The over-current relays must be able to maintain coordination when the status of DG resources or operational mode of the network changes. Accordingly in this paper, a new method is proposed which could maintain the protection coordination when status of DGs or operational mode of the distribution network changes. The proposed algorithm is based on combining interval linear programming (ILP) with genetic algorithm (GA). In the proposed method, Time multiplier Setting (TMS) is calculated by the LP and the pickup current setting is calculated by the GA. The proposed method is applied to a sample distribution network. The advantages of this metho d are compared with the conventional GA method. Simulation results show that, the mis-coordination of the directional over current relays (DOCRs) is eliminated and the computational time is improved compared to the conventional GA. In addition, the operating time of DOCRs is decreased. With the changes in DGs, islanding, and the connecting/disconnecting of lines, the coordination of DOCRs will be maintained which denotes the robustness of the proposed method.