Ajuste adaptativo aplicado a técnicas para detecção dos intervalos distorcidos pela saturação de tcs nos sinais de corrente secundária

Abstract

This work presents concepts related to magnetic saturation in Current Transformers (CTs) and its consequences on the protection schemes of Electric Power Systems (EPS). Also, the main aspects of the CTs are described, such as constructive types, equivalent circuit, dimensioning, remaining magnetic flux, among other information that is necessary to understand the problem addressed. In addition, two new methods are presented for detecting the distorted intervals of secondary current signals. Both proposed algorithms are based on adaptive limits. One uses the adaptive limit for comparison with the Signals of Difference Functions of the sampled current signal. The other method uses the calculation of the angle between consecutive samples of the current signal, to perform the detection through comparison with the proposed limit. Through simulations of short circuits, performed in the EMTP-ATP software, secondary current signals distorted by saturation were obtained. The proposed methods were implemented in the MATLAB® software and several tests were carried out to prove their efficiencies. Among the analyzes performed, simulated single-phase and three-phase faults, in addition to the variation of the magnetic flux remaining in the transformer core and the load connected at its secondary terminals. In all tests, for both methodologies, the results were satisfactory in detecting the distorted intervals. Thus, the methods proposed in this research proved to be robust and efficient, thus being able to collaborate with the mitigation of the negative effects caused by the saturation of CTs in the EPS protection schemes.