Study on a protection coordination approach for over-current relays in distribution generator-integrated distribution networks

Abstract

Presence of distributed generators (DGs) can impact on the operation reliability of over-current protection relays (OCPRs) which are installed to protect a distribution network (DN). Plug-and-play and peer-to-peer operating characteristics of DGs can make a significant change in fault current values, which could lead to protection mis-coordination or mal-function of adjacent OCPRs for a distribution network having DGs. Therefore, the OCPRs should be properly adjusted to get high sensitivity and selectivity when considering the DG's operating characteristics in the DN. In this paper, an Over-Current Protection Coordination Optimization (OCPCO) approach will be developed for a DG integrated distribution netwok. This developed OCPCO approach is based on fault analysis results combined with a selected meta-heuristic search algorithm, GSA (gravitational search algorithm), in order to determine coordination factors , , and corresponding to each OCPR and the configuration change of DG-based DN, specifically right after a FLISR (Fault Detection, Location, Isolation and Service Restoration) tool has proposed possible ISR (Isolation and Service Restoration) plans. An objective function of OCPCO approach is established by considering the total coordination time of consecutive OCPRs and will be then solved by the GSA method in order to find the best protection coordination solution with the effective coefficents , , and before updating them to the OCPRs by a communication system support. Simulation results of a real distribution network model with DG models from ETAP software are used for validating the proposed OCPCO approach in this research.