In the transmission and distribution systems there are very important activities such as: planning, design, operation, maintenance and commercialization, which are based on the knowledge with good precision of its operation variables: active powers, reactive powers and phasor voltages. Misleading values of these variables distort the mentioned activities and can cause serious technical, economic and social consequences. The measurements of these variables are made in the bars of the lines by a chain of processes, where each of them introduces an error to the measurement. The power measurement errors are usually large, of the order of 3 or 4%. In the measurements of each line, anomalous or absent measurements are detected in many intervals of each month, mainly due to the indicated limitations and temporary failures in the meters. In the present work a method of calculation for the detection, identification and reconstruction of absent and anomalous measurements in the national system of electrical transmission is proposed and developed through the use of state estimation techniques and estimation of parameters based on least squares and the equations of charge flow of the lines, using all the measurements of active energies, reactive energies and existing tensions in the fifteen minute intervals, in both ends of the lines corresponding to the month in which their evaluation is carried out.