Optimal Combined and Adaptive Protection of Active Distribution Networks Considering Different System Topologies Incorporating Optimal Selection of Standard Relay Curves

The change in the topology of active distribution networks (ADNs) is one of the essential challenges that might affect the protection schemes. The conventional protection schemes based on base topology result in some coordination constraint violations in other topologies due to the outage of upstream substations and distributed generation units. In this article, new combinational and adaptive protection schemes considering all ADNs’ topologies are proposed. In the proposed combinational protection scheme, one setting group is considered for all relays. The relays’ optimal settings are determined by solving one optimization problem, including all constraints corresponding to all topologies. Although the coordination constraint violations are reduced in the combinational protection scheme, the operating time of relays is increased due to the small feasible area of the optimization problem. Hence, proposing an adaptive protection scheme with different setting groups is useful. The number of coordination constraint violations is reduced in the proposed adaptive protection method, while the speed of the protection system is satisfying. Optimal selection of curves for the overcurrent relays is another contribution of this paper that has received less attention in the available research works. The proposed methods are applied to 8-bus and 30-bus IEEE test systems. Test results show that the proposed adaptive function is more appropriate than the combinational one.