Levantamento da curva de saturação de transformadores de potência a partir de registros das formas de onda da tensão e corrente de energização

Abstract

The computational models developed to represent the electrical equipment and transmission lines that are part of a given power system depend on the prior knowledge of the parameters necessary to reproduce the electrical phenomenon of interest. For the studies of electromagnetic transients that involve the energization of power transformers, as well as for the reproduction of transient phenomena that are influenced by the nonlinear behavior of these equipment, it is necessary to model accurately, besides the electrical parameters and type of connection of its windings, the saturation curve of the transformer in question. To carry out these parameters, it is necessary to carry out laboratory tests. However, for transformers of high voltage and power levels, the saturation characteristics of the magnetic material are usually obtained through calculations and estimates, since the laboratories do not usually have sufficient electrical power to bring the transformer to the appropriate saturation levels, which can lead to inaccuracies. In view of the concern to increase safety in the operational decisions made from simulation results of electromagnetic transient studies, Chesf identified the need to develop a methodology that allows the measurement of the saturation curve of its transformers in order to measure the curves supplied by manufacturers and obtain accurate models of power transformers in ATP_EMTP format. Thus, a measuring device and software were developed that allow the analysis of the transformer magnetization characteristics in operation in the electric system, whose chosen methodology is based on the inrush current waveforms of the respective transformer. The validation of the methodology was done by comparing the waveforms of the electric quantities of interest, obtained through field records, with those obtained in the computational simulations, using the STC model of the ATP, where the saturation curves raised by the application of the developed technique and that reported by the manufacturer. The obtained results showed that the methodology used is robust and can be applied from the waveform records obtained not only by the developed measuring device but also from any oscillography, including those Oscillography Network.