This paper presents an efficient and reliable evolutionary based approach to solve the economic load dispatch (ELD) with security constraints. A new approach is proposed which employs attractive and repulsive particle swarm optimization (ARPSO) algorithm for ELD. Incorporation of ARPSO as a derivative-free optimization technique in solving ELD with security (voltages and line-flows) constraints significantly relieves the assumptions imposed on the optimized objective function. The proposed approach has been implemented on three representative systems, i.e. IEEE 14 bus, IEEE 30 bus and IEEE 57 bus systems, respectively. The feasibility of the proposed method is demonstrated and the results are compared with linear programming, quadratic programming and genetic algorithm, respectively. The premature convergence problem, that is common in all evolutionary computation techniques, is solved in ARPSO by including the diversity factor in the Type 1 PSO algorithm. The developed algorithms are computationally faster (in terms of the number of load flows carried out) than the other methods because only one run is required. © 2006 Elsevier Ltd. All rights reserved.