Influence of the nonlinearity of measurement transformers on effectiveness of module error correction

Abstract

The article presents the program spectral line method of module error correction in linear input circuits. The method requires the knowledge of the frequency characteristics of the module errors and the phase errors of the input circuit to be corrected. The method was used for frequency error correction of measurement transformers applied in electronic power transducers. Such input circuits are nonlinear and distort the measured signals. The article presents the analysis of the influence of the nonlinearity of the input circuits upon the effectiveness of correction of frequency errors of the input circuit module at measurements of the root-mean-square value.

Improvement the efficiency of frequency errors correction of current transformer within the range of non-linear operation

“…Under the assumption that N samples of the measured signals are gathered in the course of sampling process, the active power P δ is calculated as follows: [4] presents the concept of measurement of frequency errors of input stages used in electronic devices for measurement in power systems. For measurement of the said errors the complex voltage ratio measurement in the sampling two-channel measurement system has been proposed ( fig.…”

“…The correction efficiency depends inter alia on the accurateness of determination of the characteristics of the input stage errors. The results of the research presented in papers [4,5] show, that within the range of non-linear current transformer operation, on the effectiveness of frequency error correction, when measuring RMS value of current and power, determines the effectiveness of errors correction of the fundamental harmonic. This is due to the decisive participation of the fundamental harmonic in power systems.…”

“…7 and 8 results do not take into account higher harmonics appearing in the secondary current of the current transformer. The influence of higher harmonics on the effectiveness of frequency errors correction of current transformer within the range of non-linear operation was shown in papers [4,5].…”

“…Very high efficiency of the method was shown with the measurement of the non-sinusoidal power with the use of the transformer input stages applied in the industrial measurement instruments, in the linear range of their operation [3]. Papers [4,5] present the findings of the research which show the efficiency of the method of frequency error correction within the range of the nonlinear operation of the current transformer. The findings of the research prove the reduction of the correction efficiency when the measured signal is included in the range of the non-linear characteristics of the transformer conversion, but they do not disqualify this correction method under such circumstances.…”