Inserting polarization processes in a fluid charge transport model: Improvements and difficulties

Understanding the space charge behaviour in solid organic insulations under thermo-electrical stress is of particular interest as charge dynamics is closely related to electric field distortion, charge accumulation and at last to materials ageing. Many polymers used as electrical insulators are polar materials, and have a non-linear behaviour as regards conduction processes. Hence, the underlying physics is not easily accessible and understandable. A charge transport model coupled with relaxation functions has been developed recently. In this paper, a comparison between the experimental measurements and the simulation results extracted from the coupled models is proposed, for two different materials: a polar material (PEN) and a weakly polar material (LDPE). From these results, we discuss the issues related to the prediction of the thermo-electrical behaviour of solid organic insulating materials, when the difficulty arises not only from the experimental observation (i.e. separating polarisation from transport processes), but also from the mathematical treatment required for modelling.