A Proposed FLISR Approach for Distribution Networks with Distributed Generators

Integration of Distributed Generators (DGs) into a distribution network (DN) can significantly improve the reliability of power supply and reduction on power losses. However, the operation of DGs can also lead to complexity in the protection of distribution networks. As a case study, this paper will consider the effects of two DG types on the protection system of DNs through analyzing a proposed Fault Location, Isolation, and Service Restoration (FLISR) approach. This FLISR approach can achieve fast total fault processing time and meanwhile consider DGs as ancillary services for post-fault restoration planning of the DN to minimize the number of outage customers and the amount of lost power. Specifically, tripping-threshold currents of overcurrent relays are combined with the status of switching devices and the loss of voltage to detect and locate different faults in a distribution network with DGs. Isolation of faulted sections and post-fault service restoration in the DN are implemented by solving an objective function with two constraints. Six performance indices are selected for the post-fault SR process. By using E-Terra software for a distribution management system (DMS), simulation results of a 22kV distribution network with DGs are used to validate the proposed FLISR approach. Consequently, the developed FLISR approach could be effectively adaptable to high penetration of DGs into the distribution network and able to properly indicate risks of protection mis-coordination, quickly detect and locate various faults as well as rank all possible post-fault SR plans in DG-integrated distribution networks within a total time of two minutes.