Effects of Degassing on Space Charge and Conductivity in Water Tree-Resistant XLPE

This study investigates water-tree resistant XLPE, focusing on space charge and conductivity characteristics before and after degassing treatment. The measurements included the polarity and distribution of space charges, as well as the changes in average bulk charge density and current density under various electric fields. The results indicate that after degassing, the average bulk charge density and threshold electric field for conductivity both decreased, while the electric field required for charge injection increased. At electric fields of 70 kV/mm and above, negative space charges dominated in samples before degassing. In contrast, after degassing, positive charges began to accumulate and exhibited layered distributions. These phenomena can be attributed to the removal of cross-linking byproducts and impurities during degassing, resulting in deeper trap levels within the samples.