Optimal Protection of Smart Grids Using Communication-based Dual-setting Directional Overcurrent Relays Considering Different Grid Configurations

Abstract

The variations of short circuit currents' flows and values in microgrids (MGs) and smart grids (SGs) might change because these electrical networks could be operated in various grid topologies and operating paradigms. Optimizing the SGs' protective schemes based on islanded mode, besides the base operating mode, has received a great deal of attention. However, less attention has been paid to developing optimum protectives schemes according to selectivity constraints for other topologies in addition to grid-connected/islanded conditions. This study tries to improve the existing protective schemes for SGs and MGs by the dual-setting directional overcurrent relays (DS-DOCR), according to several topologies regarding the distributed generations (DGs) unavailability/disconnecting, in addition to the base configuration and islanded operating condition. The DS-DOCRs operate independently using different relay parameters in the introduced scheme during short circuits and events in forward/backward directions. The desired forward or backward curves operate as a signal received from the other side of the protection zone. The features of the introduced communication-aided protection network based on DS-DOCRs are utilized to distinguish the optimum settings in accordance with different selectivity constraints for various topologies. This research is simulated in the distribution grid of the IEEE 30-bus test system. To implement the introduced study, DIgSILENT has been chosen for the load flow/short circuit evaluations. In addition, MATLAB has been chosen to program the genetic algorithm (GA)-based for solving the optimization problem. Comparing the obtained results with available references shows that no mis-coordination appears in various topologies, whereas the DS-DOCR's tripping time is satisfying.