Implementation of Directional Over-current Relay Coordination Approaches in Electrical Networks

As the smart grid concept is employed in the electric power system, network load flow and topology changes intensively to meet the best generation-demand balancing point. These changes must account for protection devices to enhance their performance. The coordination of directional over-current relays is most commonly studied based on fixed network operation and topology within a mesh power system. But sub-transmission and distribution systems constantly operate differently to satisfy the variety of load demand levels throughout the day and year. Hence, if the setting of directional over-current relays changes according to the different operations of the system, then relay operation time and sensitivity can both be enhanced. This can potentially improve the protection performance in a smart grid system. Therefore, this study is carried out based on the comparison among three coordination approaches: conventional (fixed settings), discrete (groups of settings), and continuous or real time (dynamic settings).