Charge dynamics in polymeric materials and its relation to electrical ageing

Electrical Engineering should face the challenge of developing a mature approach in insulation design. Modeling charge transport and linking charge dynamics with dissipative processes responsible for electrical ageing are crucial as regards this objective. Such an approach is exemplified here for polyethylene-based materials by introducing two models describing bipolar Space Charge Limited Current in transient and steady states. They rely on two classical descriptions of the distribution function of the energy levels of trap states - single trapping level or exponential distribution. Their predictions are discussed as regards the experimental behavior. They notably highlight the importance of recombination processes in explaining the sigmoidal shape of the steady-state current-voltage characteristic and explain the development of oscillatory charge packets. The energetic features of charge dynamics is considered through the recombination of charges leading to electroluminescence. The spectral analysis of the emitted light advocates the existence of massive chemical/physical degradation in the electrical regime where recombination is a major factor of the Space Charge Limited Current (SCLC).