Optimal placement of switches on DG enhanced feeders with short circuit constraints

Planning of protection systems plays a significant role to achieve an efficient behavior (or performance) of distribution systems. Feeders that offer high robustness and reliability are essential to ensure continuous energy delivering to all customer loads. Since distributed generation (DG) has increased its penetration in distribution systems, it has become necessary to place protective devices (such as reclosers) in order to allow DG islanded operation, which decreases the energy not supplied. This paper addresses efficient placement of protective switches, which mainly comprises circuit breakers and reclosers. Two optimization approaches are proposed to enhance reliability indices. First, a single objective optimization problem is defined to maximize the profit of the distribution system operator. Such problem is solved through implementing the differential evolution algorithm (DE). Second, a multi-objective optimization problem is defined to reduce the system average interruption duration index (SAIDI), the system average interruption frequency index (SAIFI), and system costs. This approach yields optimal planning of switches by applying the non-dominated sorting differential evolution algorithm (NSDE). The heuristic algorithms are implemented in Matlab, while the power system is modeled in DIgSILENT in order to use a co-simulation environment between these two tools. Simulations are developed on a real test feeder for two cases: (i) without DG; and (ii) with 6 MW penetration of distributed sources. Results show the importance of both DG and protective devices to enhance reliability, and the effect of enabling intentional islanded operation.