A study of water tree suppression in polymeric insulating materials

To study the water tree suppression in polymeric insulating materials, experiments were conducted on LDPE and XLPE specimens applying voltage stress of 3kV/mm for up to 1000 hours in copper sulfate solution and sodium chloride solution. The results demonstrate that XLPE specimens containing lipophilic surfactants with HLB value smaller than 6.5 show a significant effect of water tree suppression. Taking the results of the experiments into consideration, the mechanism of water tree suppression was examined. It was presumed that the surfactant molecules in LDPE or XLPE insulation might form micelles and accept excess moisture in hydrophobic polymeric material, resulting in the suppression of water tree generation