Characterization and Error Compensation of a Rogowski Coil in the Presence of Harmonics

This paper reports the results of an experimental study dealing with a commercial Rogowski coil current transducer (RCCT) in the presence of harmonic distortion. The RCCT was observed under two conditions: 1) sinusoidal excitation with frequencies from 50 to 750 Hz and 2) nonsinusoidal excitation using fundamental frequency and one harmonic, with adjustable amplitude and phase shift. The experimental results show only a weak dependence of the harmonic current ratio error and phase displacement on the amplitude and phase shift of the excitation harmonic. The phase displacement is also independent of the conductor position within the Rogowski coil window. An error compensation method, based on the frequency response, was implemented and tested with a distorted waveform. The compensation method allows one to obtain an improvement of the RCCT accuracy class from 1% and 1°, in the case of a sinusoidal signal at mains frequency, to 0.05% and 0.05°, both for the fundamental and the distorted signal harmonics.