On-site Calibration Technology of Current Transformer Based on Background Current Modulation

This paper proposes an active on-site calibration method through background current modulation. It can measure the error of the current transformer in service from 1% to 120% rated current percentage without power supply interruption. To prove the effectiveness of the method, an experimental validation was carried out. The on-site calibration results are compared with those obtained from off-line calibration. Calibration results showed that, the ratio and the phase angle errors under on-site and off-line calibration condition are less than 0.01% and 1′ respectively, which meets the requirement of the 0.2 accuracy class calibration.