In this paper, a new approach by accomplishing dynamic transmission expansion planning (DTEP) problem, the optimum generation level of generators is determined for annual load peak using a genetic algorithm (GA) based quadratic programming (QP) method. This study is carried out in order to achieve a better prospect from the generation network and consequently the suitable planning for its future expansion. Another important aspect of this paper is taking the advantage of line outage distribution factors (LODFs) or sensitivity analysis for the evaluation of network reliability instead of the direct current load flow (DCLF), that the computations and performance of DTEP problem considerably speeds up in comparison with previous researches. Also, the applied coding for problem solution using GA is more flexible and is significantly improved the performance of the proposed method. The proposed method is successively applied to a realistic system of the 18-buses Azerbaijan regional electric network, which is located in the northwest of Iran, and the results are extensively analyzed. The results evaluation reveals that the generators with high capacity operated in full capacity almost the whole of the planning period, because the generation cost coefficients is decreased as the generator capacity increased and vice versa. (C) 2010 Elsevier Ltd. All rights reserved.