Research on Frequency Characteristics of Errors in Low-Voltage Current Transformers

During the on-site calibration process of low-voltage current transformers (low-voltage CT), there may be a frequency deviation in the calibration current, which can lead to deviation in the calibration results. In response to the above issues, this article proposes a method for calculating low-voltage CT errors under different frequency currents. The use of this method can effectively eliminate the impact of frequency offset on low-voltage CT calibration results. Firstly, measure the magnetic permeability of the iron core material of the transformer at different frequencies, and apply the zero flux method to measure the impedance parameters of the secondary winding of the transformer. Based on the experimental measurement results, derive the parallel branch parameters in the T-type equivalent circuit of the transformer, and calculate the corresponding errors of the transformer at different frequency current ranges.