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An Analysis of Mechanical Stress in Solid Dielectrics Caused by Discharges in Voids

The stress waves generated by electrical discharges within a void in polyester resin were analyzed quantitatively. The rise time of the stress transient acting against the void wall was 800 ns. The acoustic energy submitted to the solid was 3 nJ which was 0.002% of total energy released by the discharge. These values were determined by the original wave analysis in which the influence of the transfer functions of a propagation path and a piezoelectric transducer were eliminated from the detected waveforms using a deconvolution technique. The shape of the time function of the source is discussed. It is shown that the pressure waves from large electrical discharges within voids in polyethylene are too small to cause any mechanical damage.