Thermodynamic effect of charge trapping in synthetic insulation of HV cable

An attempt is made to show that the measurement of Cp to characterize the thermodynamic equilibrium of PE (polyethylene) used for HV insulation is of great interest for calculating the cable lifetime. First results have shown that, for bulk samples, δCp increases with the implanted charge, and low charge level already has a significant effect on δCp. Above a critical value of implanted charge, δCp comes back to zero. This means that all the energy stored in the polarized sample is released during the breakdown. Interfaces between each film appear to have a significant effect because results are differ markedly as compared to those for the bulk sample