ABSTRACT
The electrical power system network is considered as one of the most complex systems that have been built by human civilization. The power network is growing larger and larger, and the complexity of power system operation is also increasing. Protective relays play an important role in saving continuity of the electric power network. The main goals of a protective relay are to isolate fault parts quickly, keep healthy parts in service, and maintain the reliability of the electric network. The operating time of directional overcurrent relays (DOCRs) depends on pickup current (Ip) and time dial setting (TDS). Coordination problem of DOCRs have been considered non-linear optimization problems with many constraints. In this chapter, the coordination problem of DOCRs is formulated as a single objective function using different optimization algorithms. Water cycle algorithm (WCA) and modified version for water cycle algorithm (MWCA) are used to solve coordination problem as a single objective function. Also, moth-flame optimization (MFO) and improved moth-flame optimization (IMFO) are suggested to solve the coordination problems in the case of standard and non-standard characteristic relay curves. The feasibility and performance of the proposed techniques for solving the coordination problem of DOCRs are investigated using different systems and compared with several well-known algorithms.
