Adaptive coordination of overcurrent relays in active distribution networks based on independent change of relays' setting groups

The capability of network configuration change and high penetration of distributed generations (DGs) are two important characteristics of modern distribution networks. The configuration change and connection/disconnection of DGs result in the variation of fault currents' magnitude and direction besides changing the role of protective devices as primary or back up protection. This fact can make the protection coordination complicated or even impossible in some cases. One of the solutions to this problem is to use a setting group (SG)-based adaptive protection schemes. SG-based protective schemes protect various network states (different configurations and connection/disconnection of DGs) using a limited number of SGs. Therefore, it is needed to propose an algorithm to specify the settings of each SG and the determination of SG selection in different network states (NSTs). In this paper, previous attempts in the utilization of SG capability of Overcurrent relays (OCRs) are examined and a novel approach is proposed which is capable of protecting the same network with lower delay in relays' operation times although it requires a fewer number of SGs. In this paper, a new method based on integer linear programming (ILP) and particle swarm optimization (PSO) is utilized to specify the proper SG to activate for each relay in each NST, in order to minimize the total operating time of OCRs, considering coordination constraints. The efficiency of the proposed method in comparison to the previous methods is demonstrated by applying on a sample distribution network.