Space charge development in XLPE insulation with and without tree retardant subjected to DC field

Using the Thermal Step Method (TSM), which is a completely non-destructive technique to determine space charge in polymeric insulation, the evolution of the TSM current response and the space charge density during long-term de aging have been studied. The measurements were performed on two types of XLPE insulation with significantly different electrical tree initiation properties. One type of XLPE contained a hindered amine light stabilizer (HALS) to retard electrical treeing while the other did not. The type of antioxidants and their concentration were the same in both materials. Care was taken during insulation aging to avoid any partial discharges. Space charge density was determined from the TSM measurements using inverse matrix calculations. Although the overall space charge quantities accumulated in both materials during aging were similar, the charge distributions showed notable differences.