Calibration of MV Voltage Instrument Transformer in a Wide Frequency Range

A set-up for the measurement of the frequency response of voltage measurement transformers under actual waveform conditions is presented. It is based on a two steps 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. Standard uncertainty in the measurement of the voltage transformer error is estimated 200 V/V for the ratio error and 300 µrad for the phase displacement up to 15 kHz. First applications to the frequency calibration of voltage measurement transformers with different rated primary voltages up to 50 kV are presented.