Coordination Preservation of Directional Overcurrent Relays in a Multiple-Topology Network with Distributed Generations by Fault Current Limiters

This work studies the directional overcurrent relays (DOCRs) coordination in multiple topology networks with DGs. The optimal use of fault current limiters (FCLs) is catered. A Two-stage system is done. The optimal time and current settings of DOCRs are determined to achieve coordinated operation of backup-main DOCR pairs under all possible topologies in the first stage. After distributed generators (DGs) are connected, FCLs are optimally allocated to preserve the same DOCRs settings. The locations and sizes of FCLs are got by solving an optimization problem in the second stage. Optimally-allocated FCLs impose a sustained coordinated operation of DOCRs under DGs for all network topologies.