Optimal Recloser-Fuse and Distribution Network Protection Coordination including Distributed Generation Relays

This paper proposes two different approaches to optimally coordinate overcurrent protection devices in medium voltage distribution systems with distributed generation (DG). The first approach combines linear programming with particle swarm optimization. The second approach combines linear programming with genetic algorithms optimization. The analysis considers two 20 kV radial distribution systems with DG, applying different network protection schemes: (i) solely based on directional overcurrent relays, and (ii) based on a typical recloser-fuse combination. In the first case, optimal coordination between the positive/negative/zero-sequence directional overcurrent elements of the network relays and the voltage-dependent overcurrent elements of the DG unit relays is considered. In the second case, optimal coordination between the latter and the reclosers is achieved, also considering the non-settable fuse characteristics. The simulation results show that both algorithms are quite robust and give a very low total tripping time for each test system considered.