Mechanical processes in the long term degradation of solid insulation

Shows that vibrational electrostatic forces are the dominant influence in the initiation of electrical trees in solid dielectrics. Whilst the electrostatic forces are small they will by virtue of being oscillatory lead to the build-up of appreciable stresses within the material. Voids will thereby be created and grow into cracks according to the well known mechanism of fatigue failure. As the cracks develop, so they will attain a size capable of sustaining discharge activity with the consequent onset of treeing. This paper describes experimental results and outlines the repercussions on insulation system design