Enhancement of over current coordination for a distribution system connected to a microgrid using unidirectional fault current limiter

The growth in integrating more distributed generation (DG) urged the step for modern distribution networks (DN) to operate in microgrids mode. However, integrating DG into DN, increase the short-circuit level, and consequently disorientate and disturbed the operation of protection schemes. However, utilizing of Unidirectional Fault Current Limiter (UFCL) is one of the numerous practical solutions used currently to mitigate the impact of DG on the microgrid protection schemes. Employment of UFCL at the point of connection of downstream network to the upstream network overcome DG influences on relays coordination and preserve the current coordination time interval (CTI) among different protective relays. Placement of UFCL at the tie node decreases the contribution of the upstream network to fault currents in the downstream network and not vice versa. This property decreases the complexity required to coordinate protective devices in presence of DG in the microgrid, and ensures preserving the existing schematic configuration of the protective devices. Due to that, improvement in the Performance of protective relays during various fault conditions. In this study, a 30 KV medium voltage DN was simulated in ETAP and the effectiveness of the proposed method for a number of potential scenarios in the network was verified.