Improving the polarisation and depolarisation current measuring method to avoid ground wire interference

Abstract The ground wire is significantly interfered by the current above 1 μA in the industrial field during the traditional polarisation and depolarisation current (PDC) measurement. This paper explains a method to test PDC from high‐voltage wire using a principle of equipotential picoammeter, which is completely isolated from the ground wire and connected in series with the high voltage wire. In this method, a device is designed with a multi‐range automatic switching function. The device can automatically switch the test range current from 1 pA to 10 mA with a resolution of 1 pA. To demonstrate the device and effectiveness of this new method, the traditional and the proposed new device are used to test the PDC of cable samples in the laboratory as well as in an industrial environment. It is worth noting that there is almost no interference on the Earth wire in the laboratory environment but massive interference in the industrial environment using a traditional method of PDC measurement from ground or Earth wire. The new method of high‐voltage testing can efficiently eliminate the interference and accurately measure PDC in a strong industrial interference environment. Furthermore, the wiring of this new method and device is relatively simple, which is convenient for industrial applications.