Dielectric aging and dielectric degradation (breakdown) of polymer films in AC electric fields

An explanation is proposed for the difference in the electrical strength properties of polymers in DC and AC fields. Energy release during recombination of electrons and holes injected into a polymer dielectric is considered as a factor accelerating the process of electrical aging of these dielectrics in AC field. It is shown that the nonradiative relaxation of electronic excited states, which causes bond breaks in macromolecules and the formation of free radicals, leads to the formation of deep electron traps in a polymer dielectric, as a result of which the ionization of macromolecules in the electric field is accelerated due to electron transitions into these traps. In solid-state plasma, a shielding effect occurs, leading to a decrease in the ionization potential of molecules. As a result, the ionization rate of macromolecules increases, i.e. the rate of formation of charge carriers, which leads to a decrease in the electrical life time of the polymer dielectric in AC field compared with the life time of polymers in DC field.