Frequency Response of MV Voltage Transformer Under Actual Waveforms

A setup for the measurement of the frequency response of voltage measurement transformers under actual waveform conditions is presented. It is based on a two-step procedure that makes use of high voltage gas insulated capacitors and a digital bridge. It allows calibrations using distorted waveforms, with a fundamental tone at medium voltage level and superimposed harmonics up to 20% and 15 kHz. Combined standard uncertainty in the measurement of the voltage transformer (VT) error is estimated at 200 µV/V for the ratio error and 300 µrad for the phase displacement up to 10 kHz. First applications to the measurement of the frequency response of VTs with different rated primary voltages up to 50 kV are presented.