New findings on water tree in high polymer insulating materials

This paper first treats confirmation on that moisture absorption behavior of XLPE (crosslinked polyethylene) satisfies Fick´s equation and relates the effects of moisture absorption and temperature on water tree in XLPE under water. Secondly, the results of experiments and the considerations on them related with the findings about water trees in humid air and in epoxy resin are described. By a few examples, for instance, it became clear that water tree can be generated in XLPE even under 65% relative humidity and that water tree can grow in epoxy resin even below glass transition point of temperature. This paper further proposes a hint of view stand for that water tree is a fruit of chemical reaction induced by alternation in chemical equilibrium of the insulating materials due to impressed electric field and takes up a certain preventive means against the generation of water tree.