A novel MILP formulation for optimal allocation and coordination of protective and switching devices in active distribution networks

In the last decade, the increasing penetration of distributed generation has prompted the proposal of new formulations for distribution protection system planning, as the typical indications of coordination may not be reliable for active networks. In this context, a few papers that explicitly enforce coordination constraints have been published. However, these papers are mostly based on heuristics and metaheuristics; therefore, although the solutions are feasible, there is no guarantee of optimality. This paper presents a mixed-integer linear formulation for the allocation and coordination of control and protective devices in distribution systems with distributed generators. Thus, the proposed approach guarantees both the optimal investment plan and feasibility of the protection system operation. The proposed formulation is tested for a 69-node system considering load restoration possibilities via island operation, using protective devices, and load transfer to neighboring feeders and fault permanent isolation, using switching devices. The results attest to the cost-effectiveness of the protection system and its operational feasibility, as well as the superiority of the proposed model over simpler existing ones.