Impedance change localization for live underground cable using time-frequency domain reflectometry

In this paper, an impedance change localization method for a live underground XLPE cable with a straight joint using the time-frequency domain reflectometry (TFDR) is proposed. To inject the reference signal to the live cable, an inductive coupler is used. Thus, the characteristics of the cable and the coupler are analyzed and the reference signal is designed to fit for the characteristics of the coupler and the cable. The on-voltage experiment using the TFDR is performed to localize the impedance change of cable. As a result, the accuracy of the TFDR for the on-voltage cables is proved.