Design of Setting Group-Based Overcurrent Protection Scheme for Active Distribution Networks Using MILP

In active distribution networks, system reconfiguration and connection/disconnection of distributed generation (DG) can result in protection coordination failure of overcurrent relays. Determining one set of optimal relay settings that would satisfy all possible network topologies is either infeasible or results in high relay operating times. To address this problem, recently the concept of clustering the various network topologies into a limited set is proposed where an optimal Setting Group (SG) is determined for each network topology cluster. This article proposes a novel problem formulation that simultaneously obtains the optimal relay SG and network topology clusters. Due to the complexity and non-linearity of the SG protection coordination problem, the SG protection coordination problem is reformulated as a mixed-integer linear programming (MILP) problem. The effect of the relay characteristic type on reducing the operating times of relays is also investigated. Comparative analysis is provided that highlight the superior performance of MILP over other heuristic optimization techniques. Data exchange between circuit breakers, DGs, CPU and relays are developed based on the IEC 61850 standard to illustrate the implementation of the proposed adaptive protection scheme on real networks.