Development and Evaluation of a Polarization/Depolarization Current Measurement Device for High-Voltage Cable Insulation Analysis

To measure the polarization/depolarization current (PDC) of cross-linked polyethylene (XLPE) power cables in service, a micro-current measurement device was developed, which can be placed on the high-voltage side of the cable and other electrical equipment. Traditional PDC testing methods are not suitable for field measurements and are significantly affected by field interference. By comparing several kinds of common PDC measurement methods, the measuring circuit in which a micro-current measurement unit was placed between the high-voltage power supply output and the high-voltage side of the test object was chosen. Firstly, the micro-current measurement device was developed according to the requirement of high-voltage side measurement. Then the steady-state current measuring result of self-designed device was contrasted and verified with that of Keithley 6517B. For a segment of 110 kV XLPE cable, PDC tests were also conducted using both the self-designed device and 6517B. The measuring results of steady-state current and cable by the self-designed device are close to the results by 6517B. Meanwhile the self-designed device can avoid low-frequency signal interference introduced by the ground wire. The PDC measurement and corresponding analysis can provide a more accurate assessment for the active cable insulation condition.