A Comparative Analysis of Optimal Coordination of Distance and Overcurrent Relays with Standard Relay Characteristics using GA, GWO and WCA

One of the important aspects in the design of protection schemes is to confirm the proper coordination among various relays used in power system. Directional overcurrent relays (DOCRs) are generally used in power system networks due to its cost effectiveness as compared to other protective relays. However, the use of distance relays is also very popular in transmission and sub-transmission system due to its fast operation. This paper presents a combined study of optimal coordination of distance and DOCRs which is a highly constrained, non-linear optimization problem. Optimal coordination study of distance-DOCR has already been performed considering a fixed characteristic of DOCRs. To improve the coordination scheme, in this paper two different standard relay characteristics namely normal inverse (NI) and very inverse (VI) has been considered and a comparative analysis of distance-DOCR coordination is presented. To obtain the optimal values of time multiplier setting (TMS), plug setting (PS) and second zone operating time (Tz2), three heuristic techniques namely genetic algorithm (GA), grey wolf optimization (GWO) and water cycle algorithm (WCA) has been used. The performance of the proposed scheme is tested on 6-bus test system and the results are compared in terms of total relay operating time.