Detecção da saturação dos transformadores de corrente e seu impacto sobre a qualidade do sinal corrigido

Abstract

This paper evaluates the performance of a method to compensate the distorted waveform intervals secondary current signals, which occur due to the saturation of current transformers (CTs) core, when associated with three techniques for detection of those intervals. Both the method of compensation, as the detection techniques are presented didactically and were chosen because they presented promising results, being well accepted by the researchers. Short circuits were simulated using software EMTP-ATP to obtain the current signals. The detection methodologies were implemented in Matlab® and evaluated in terms of recognition of distorted ranges and speed of response. Also the compensation method was evaluated in terms of accuracy and processing time. Simulations were conducted involving different types of short circuit and different values for CT burden. Moreover, the remanent flux in the CT core was varied and it was found that the higher is the value of remanent flux the lower the time to CT saturation. Calculations of transient error and the use of a Fourier filter to obtain the RMS values of the compensation were taken as basis for the qualitative analysis of the performance of the correction technique. It was observed that different instants of detection of distorted parts provide different margins of error to the method of compensation associated with the detector, showing the dependence of the correction to the accuracy of the saturation detectors.