The identification of the values with good accuracy of physical parameters of transmission systems is very important because using very different values from the real ones seriously distorts the evaluation of the planning, design, operation, maintenance and commercialization of the transmission systems. The present work describes the identification of physical parameters of a real transmission system using a mathematical model with variable values of the physical parameters. The identification is done by comparing the real operation of the system with the simulated operation of the model, varying iteratively the physical parameters values of the mathematical model. To this purpose two different techniques were applied, a classical and a modern meta-heuristic technique to 47 high voltage transmission lines of the Peruvian electrical system. The real operation is obtained from the database of the measurements of the operating variables of the transmission system. The correct values of the physical parameters will be those that correspond to the simulated operation identified. This paper is organized as follows: Section II describes the philosophy of the parameter estimation problem, here is included the symbology, the model of the transmission system, the formulation of the problem and its solution. In section III, the results of the identified parameters are presented and discussed. Finally, in section IV the conclusions are presented.