Optimal fault current limiter sizing for distribution systems with DG

Integration of Distributed Generation (DG) in distribution systems results in new fault current levels. Among various DG types, synchronous based DG provides the highest fault current levels. Variations in fault current levels can lead to protection coordination failure or device failure due to excessive fault levels. In this paper, it is proposed to use Fault Current Limiters (FCL) in series with the DG and utility interconnection point to restore fault current levels to the original values (without DG). FCL are composed of a resistive and reactive component which are determined optimally by using Particle Swarm Optimization (PSO). The FCL sizing problem is formulated as a Nonlinear Programming (NLP) problem where the main objective is to minimize changes in fault current levels due to the addition of DG. The results show that FCL can be designed optimally to maintain fault current levels and thus avoid the possibility of protection coordination failure.