A study on electrical breakdown by water treeing in XLPE

We investigated the space charge characteristics in sheet samples under AC field which have water trees developed by using various kinds of electrolytes. The results show that: homo charge was formed around the tip of water trees independent of the electrolyte species; the amount of space charge varied with electrolyte species (among the electrolytes used, ferrous sulfate induced the largest space charge in spite of water tree growth being relatively small); the space charge induced by water trees changes the internal field distribution in the insulation; the harmfulness of specific ions with regard to electrical breakdown cannot be explained simply by the change in the field distribution.