Application of the pressure wave propagation method for the analysis of insulating materials

In the field of electrical insulation, polymers are replacing progressively formerly used materials. When such an insulator is subjected to a voltage gradient, an internal space charge and a polarization develop, eventually reducing the apparent electrical strength of the material. We have applied the pressure wave propagation method to the analysis of the phenomenum in polyethylene. The spatial charge distribution is successively measured in samples subjected to various processes. The obtained data show that charge injection at the electrode-insulator interface occurs at much lower applied voltage gradients than previously assumed. A comparison of the results at 20°C and 70°C also shows the influence of the transport properties of the material itself.