An improved simulated annealing–linear programming hybrid algorithm applied to the optimal coordination of directional overcurrent relays.

• A novel hybrid technique to coordinate DOCRs. • Five well-known IEEE test systems are used to validate the proposed technique. • Simplified implementation, as it combines two well-known algorithms. • Excellent performance and convergence, suitable for online adaptive coordination. • Results are comparable with the best reported in the specialized literature. The coordination of directional overcurrent relays (DOCRs) is a constrained and nonlinear optimization problem which consists in finding suitable plug and time dial settings so that the relay operational times are minimized, keeping selectivity and sensitivity characteristics. Recently, several efforts have been devoted to automate the coordination of DOCRs. This paper proposes a hybrid technique entitled simulated annealing–linear programming (SA-LP) to achieve the optimal coordination of DOCRs. Five test-systems (IEEE-3, IEEE-6, IEEE-8, IEEE-15 and IEEE-30 bus) are used to verify the effectiveness of the proposed technique. Results obtained with the SA-LP are confronted against other optimization techniques reported in specialized literature, under identical conditions. The proposed approach presented good quality solutions, low computational processing times and great convergence towards the optimum solution, presenting an advantage over adaptive coordination tendency by enhancing monitoring, communication capabilities and grid control. [ABSTRACT FROM AUTHOR]