Water cycle algorithm for optimal overcurrent relays coordination in electric power systems

The coordination of overcurrent relays in interconnected mesh systems with many sources can be formulated as an optimization problem. Different conventional and heuristic algorithm-based optimization procedures have been presented to deal with this nonlinear highly constrained optimization problem. This paper presents an attempt to apply water cycle algorithm (WCA) in order to optimally deal with this coordination problem. The design variables contain the time dial, pickup current, and type of inverse characteristic of each relay. The viability of the proposed method is compared to other competing methods for different interconnected mesh systems including distributed generation units such as the 15-bus system. For obtaining a realistic study, the proposed WCA method is tested in solving the coordination problem for a detailed IEEE 30-bus system, which involves 111 industrial commercial relays type SEPAM-2000 and 333 design variables within the search space along with 726 inequality constraints. The IEEE 30-bus system is modeled using the Electrical Transient Analyzer Program. The strength of the WCA based on methodology is extensively confirmed using the simulation results and comprehensive comparisons.