Restoring recloser-fuse coordination by optimal fault current limiters planning in DG-integrated distribution systems

• Recloser-fuse coordination is studied in presence of DGs.
• Optimal fault current limiters are applied to solve this protection problem.
• Multi-objective formulation is proposed for the problem.
• Mitigation of voltage sag is considered.

In this paper, the Fault Current Limiter (FCL) is used to restore the coordination between the protection devices in distribution systems with high-level of DG penetration. The FCL allocation may be described as an optimization problem involving multiple objective functions which are contradictory and of different dimensions. So, it is formulated as a multi-objective constrained nonlinear programming problem. The interaction among different objectives gives rise to a set of compromised solutions, largely known as the Pareto-optimal solutions. The objectives are to simultaneously minimize: the increase in fault current levels due to the penetration of DG, voltage sag, and the total cost (size) of required limiters. The optimization problem is solved using Particle Swarm Optimization (PSO). The method is applied to two distribution test systems. Effects of different operating factors are assessed. Comparative analysis of results is provided.