Thermal-electric field distribution around a defect in polyethylene

In the presence of a stress enhancement, a lightning surge causes space charge formation and power dissipation which can result in substantial temperature rises in dielectrics. Poisson's equation and the thermal diffusion equation have been solved in 2D with field-dependent material parameters to compute temperature rises of over 80 K during a 100 ns risetime surge which produces a background field of 40 kV/mm applied to a 100 /spl mu/m protrusion with a 0.5 /spl mu/m tip radius. Such a temperature rise could play a major role in the lightning-induced conversion of water trees to electrical trees.