Transforming characteristics of the Rogowski coil current transformer with a digital integrator for high‐frequency signals

Abstract

The Rogowski coil current transformer is widely used in intelligent substations for its rapid response, wide bandwidth measurement, and non-magnetic saturation. In most cases, it works with a digital integrator to restore the differential signal output by the coil. However, its output waveform can be deformed when transforming high-frequency signals generated in the transient process of the power system. The working process of the Rogowski coil current transformer is presented, including Rogowski coil head transferring, analogue filter filtering, analogue-to-digital converter sampling, and digital integrator restoring. The reason for the waveform deformation when transforming high-frequency signals is investigated by theoretical derivation. In order to show the waveform deformation phenomenon, an experiment is devised and the results output by the Rogowski coil transformer and low power current transformer are compared and analysed. Several measures to improve the output waveform deformation are proposed, such as increasing the sampling rate of the converter, decreasing the cut-off frequency of the filter, or replacing the digital integrator with the analogue integrator. The researches provide important guidelines for the application of the Rogowski coil current transformer with the digital integrator in the case of frequency aliasing.