Optimal overcurrent relay coordination in power distribution system using a new approach

This work presents a new approach to optimize overcurrent relay coordination in power distribution systems by using a genetic algorithm, involving transformer protection. An effective objective function with constraints is adopted to solve the relay coordination problem, considering not only the time setting but also the current setting multiplier. There are various types of curves such as Very Inverse (VI), moderate or Normal Inverse (NI) of relays and the damage curve of the transformer are considered in the simulation, the result shows that the proposed method is fast, accurate and applicable. In this study, time–current relay curves are plotted on a log–log scale plan and compared with those of an existing industrial power system, in addition, an example of single-ring power distribution system is tested to demonstrate the coordination and confirm that the proposed approach method is practical.

► Optimize overcurrent relay coordination in power distribution systems.
► Various types of curves of relays are considered in the simulation.
► An industrial power system and a single-ring power distribution system are tested.
► The relay settings obtained by using GA are compared with traditional method.
► The minimum grading margins that better than traditional method are presented.