Modified multi-objective PSO for coordination of directional overcurrent relays in interconnected networks

Directional overcurrent relays are used to protect transmission lines against short circuits. Reducing the total operating time of relays has always been a challenge for protection engineers. For this purpose, various optimization algorithms have been introduced, some of which are based on multi-objective optimization. The objective functions of multi-objective algorithms must have the Pareto optimality property, which it’s ignoring is one of the drawbacks of previous studies. In this paper, new objective functions are proposed for a multi-objective optimization problem. To solve the optimization problem, the Multi-object PSO (MOPSO)algorithm is applied with small but effective changes to get the fastest settings of relays. These changes include a leader selection method, a removal method of repository surplus members, and a new velocity vector for particles based on the value of the objective function in the previous iteration. The proposed algorithm is evaluated in IEEE 30-bus network and compared with the standard MOPSO. There is also a comparison with the recent outstanding papers. The proposed method, compared to the 15 algorithms of other papers, results in the lowest total operating time of relays with a 7% reduction.