Research on Time-Domain Transfer Impedance Measurement Technology for High Frequency Current Transformers in Partial Discharge Detection of Cables

Abstract

We focus on the high frequency current method which is widely applied in the partial discharge (PD) detection of cables. Aiming at guaranteeing the accuracy of this method, we study an innovative time-domain technology for effectively measuring the transfer impedance of the high frequency current transformers (HFCTs). The proposed technology called pulse injection method obtains the system response under the excitation of the wide-band instantaneous pulse signal. Firstly, by studying the working principle of HFCTs, we summarize that the bandwidth of the selected signal acquisition device should be at least 100MHz to ensure measurement accuracy. Secondly, Gauss pulse and square wave pulse are generated to determine the effects of different sources. The measurement results indicate that Gauss pulse is more suitable for pulse injection method, and the rise time should be under 10 ns to improve the starting frequency of oscillation distortion. Finally, the transfer impedance curves of five types of HFCTs are acquired by both pulse injection and traditional point-frequency methods. The measurement results show a remarkable consistency between two methods. However, pulse injection method requires the simpler operation and has a higher resolution, obviously improving the measurement efficiency and better displaying the details of the transfer impedance curves.