Analysis of Key Factors Affecting Electronic Transformer Calibration System Error

Abstract

Recently, electronic instrument transformers (EIT) meet some problems such as high error and instability in practical application, and some new EITs and the calibration system of electronic instrument transformers (CSEIT) are attracting wide concern. In this paper, some key factors affecting CSEIT error, including sampling synchronization, digital signals processing and error estimation of the calibration system itself, are analysed, and the corresponding solutions are also offered. Sampling synchronization is realized by outputting second pulse and trigger pulse at the same time, and the length of pulses response has been controlled in a short period. Digital signal processing synthesizes some special design such as FIR digital filter, industrial frequency measurement and zero-phase filter to overcome the effects of harmonics and noise, and uses FFT interpolated algorithm based on Hanning window to eliminate the calculation error when fundamental frequency spectrum leakage happens. A novel error estimation scheme of CSEIT is proposed based on the instruments with lower measuring error. Results of the error estimation of the CSEIT itself show that the system can reach the error of 0.01 % in magnitude and 30 second in phase at rated operation state.

DOI: http://dx.doi.org/10.5755/j01.eee.19.5.1674