Quality control of electrical measurements is fundamental because activities as important as the operation of the electrical system, as well as planning, commercialization and supervision, make use of these measurements, therefore it is necessary that they have a good degree of precision. This paper presents a quality control system for measurements based on: A statistical process of the six variables measured in a transmission line (active powers, reactive powers and voltages in its two bars); a process of estimation of state and a process of optimal identification of physical parameters. This system allows to detect, identify and reconstruct adequately the absent and anomalous measurements in the lines, also allowing to identify the physical component of the measurement process that is causing the problem to perform its proper maintenance. Finally, as a sample of the application to the Peruvian transmission system, the results of the detection, identification and reconstruction of the anomalous measurements in the 232 Chimbote - Trujillo transmission line are presented and discussed. The application of the system to the validation of the monthly technical evaluation of the same line is also presented, taking into account the quality of the measurements used in the corresponding analysis.