Water treeing: interaction between test temperature and other test parameters

The authors discuss complementary studies on the effect of temperature on water tree growth, conducted at two different laboratories, using the same LDPE (low-density polyethylene) reference product at 23°C and 65°C, in a point-to-plane geometry. These very similar tests yielded totally contradictory conclusions on the effect of temperature on water tree growth. In one test the water trees propagated more favourably at 23°C than at 65°C. In the other test the water trees grew larger at 65°C than at 23°C. The latter result has been observed exclusively in the case of a wet grounding environment. As this was the only fundamental difference between the tests, the authors hypothesize that the enhanced water tree growth at 65°C is to be due to an enrichment in water at the tip of the growing water tree resulting from water diffusion by dielectrophoresis followed by water condensation under the effect of the electric field