QUANTITATIVE-DETERMINATION OF THE RESIDUAL MECHANICAL-STRESS AND ITS RELAXATION IN SYNTHETIC RESIN WITH AN EMBEDDED ELECTRODE

Significant residual internal mechanical stress (RIMS) is produced during the manufacture of samples of synthetic resin electrical insulators containing embedded electrodes. It is shown that this RIMS can be quantified for simple axially symmetrical pin-plane geometries using photoelastic analysis with the aid of a fictive force model first introduced by Shibuya. It is found that the RIMS decays with a time constant of about four years in the epoxy resin CT200. The existence Of RIMS and its time dependence is important in that it influences the electrical breakdown characteristics of polymer materials where the pin-plane geometry is commonly used to assess electrical treeing performance.