A Robust and Fast Solving Approach to improve Relays Coordination considering variable sizes of DGs and their outages

Maintaining the coordination between the inverse-time-grading based relays in the presence of DGs is one of the main areas of research, where the major challenge is that the operating mode of an active distribution system (ADS) is not fixed, it is variable and sometimes uncertain and unpredictable. For example, connections and sizes of DGs can change in normal conditions to meet the variable load demands. While the number of DGs in an area can also change even during the faulty conditions because of sudden undesired outages of DGs such as due to the severe voltage drop, low fault ride through capabilities of DGs, synchronism loss, DG’s transformer loss etc.. This paper analyzes the impact of changing sizes and connections of DGs and their future increasing proliferation on the relays coordination study. Then, to improve the performance of the protective relays, this paper proposes a smart constraints-reduction approach based relays coordination method. Where it presents a novel approach to solve the complex and highly constrained relays coordination optimization problem by utilizing the basic information available at the control and monitoring center. The comparative performance of the proposed technique has been tested on the IEEE 38-bus distribution system. The test results show that the proposed method not only eliminates the unnecessary burden of the constraints from the optimization problem but also provides faster convergence of the optimization and faster operating time of the relays irrespective of the variable connections and sizes of DGs, their sudden outages, and their increasing proliferation.