A new genetic algorithm method for optimal coordination of overcurrent and earth fault relays in networks with different levels of voltages

In this paper, a new genetic algorithm (GA) method is presented to solve the optimization problem in coordination of overcurrent and earth fault relays. In addition to optimal coordination of overcurrent relays, earth fault relays are also coordinated by GA, considering critical fault condition for the relays located in two sides of network's transformers. The objective function is developed by adding new terms that are the constraints related to the coordination of overcurrent and earth fault relays in critical fault conditions considering different winding arrangements of transformers. The paper concluded by the results of a study carried out on a sample power network. The results demonstrate that the method can obtain feasible and effective solutions and, it is a promising approach for optimal coordination in practical power networks.