This paper presents the impact of environmental variables on the rating of a transmission line of Colombia and the energy dispatch of a system with overloaded lines. The IEEE Std. 738-2012, a method of calculation regarding Dynamic Line Rating (DLR), was programmed in LAB+i. Two analyses were conducted; these show differences in calculations when using DLR and static line rating (SLR). In the first analysis, twelve case studies were conducted: Each of environmental variables and the current flowing through the line was varied and the others remained constant. The second analysis consisted in evaluating the generation costs and technical losses of a system with overloaded lines. Eight case studies were evaluated: The environmental parameter to be analyzed varied and the other variables remained constant. The assessment indicated that the variables that have the greatest influence on the rating of a conductor (Idyn) are speed and wind incidence angle. The conductor temperature was lower when the wind impinged perpendicularly on the conductor. Idyn was in a range of values between 0.66 and 2.29 times the static line rating. Generation costs ranged up to 17.49% in relation to the minimum cost presented. In addition, costs ranged from -5.41% to 11.62% in relation to the cost calculated with SLR. These results allowed establishing the selection criteria of the critical span; recommendations were made to include DLR in the energy dispatch.