Abstract
For the Insulation diagnosis of live cables, the method applying DC component current has been developed. The mechanisms for the evolution has been qualitatively explained on the behavior of space charges in XLPE. However, it has not yet been fully understood. Recently, it has been presented that DC component current could be measured owing to the presence of water trees closely linking between the inner and outer semicon-ducting layer. So that, we assumed that DC component current could arise from the composite mechanisms and investigated the phenomenon on the interface between the water and conductor or shielding layer by modeling the water-copper interface. In the copper-water-copper electrodes system, DC component current and the electromotive force due to the difference in the electrode potential were observed when AC voltage was applied. Moreover, from the X-ray analysis it was confirmed that Cu2O (type p semiconductor) was produced on the surface of the electrode. When DC voltage was applied, weak polar effect probably due to the contribution of semiconductor or redox reaction was observed. From the results, it is considered that in the copper-water-copper electrodes system the electromotive force and the polar effect participate in the evolution of DC component current.
