Intelligent Overcurrent and Distance Relay Coordination in Power Networks

The increased deployment of distributed generators (DGs) in distribution networks has brought new challenges to power system protection coordination. With multiple generation sources supplying the distribution network, the conventional protective devices that were designed for centralized generation may not be sufficient to ensure proper protection coordination in case of fault. This research provides an overview of the impact of distributed generations (DGs) on protection coordination in distribution networks, as well as an analysis of the different approaches that can be used to select and coordinate protection systems in the presence or absence of DGs. The proposed approach for selecting the optimal overcurrent (O/C) relays for protection coordination takes into account various relay characteristics and uses the Teaching Learning Based Optimization (TLBO) algorithm to determine the best combination of relays for achieving optimal coordination. Optimization of the zones of distance relays is also done and proper coordination time interval (CTI) of 0.2s or more is maintained. The optimization results are tested and validated in Electrical Transient Analyzer Program (ETAP). The effectiveness of the proposed method for achieving optimal coordination in practical power system networks like IEEE-9 bus test system is demonstrated through simulation results, which show that the method can produce feasible and effective solutions.