Compensation of Complex Frequency Errors of Voltage Instrument Transformers

The paper focuses on a system for the compensation of the frequency response of voltage instrument transformers through the use of a digital filter. After a brief review of the compensation method, the performances of the digital filter in the correction of the frequency response of voltage transformers with first resonances within the 50th harmonic are investigated and quantified. Examples of implementation of the filter both in LabVIEW, for off-line correction, and by FPGA, enabling realtime correction, are given. First results show a reduction of the voltage transformer errors up to two orders of magnitude at the first resonance frequency.