Simulation of electric fields in insulation of a DC model cable under temperature gradient

The evolution of electric field and the dynamics of space charges in insulation (thickness of 4.5 mm) of a DC model cable exposed to temperature gradient have been studied by means of computer simulation. Bipolar charge transport (BCT) model that includes the generation and conduction of both electronic and ionic charge carriers was developed. The model is able to reproduce the important experimental observations, e.g., (a) the inversion of the electric field distribution under a temperature gradient, which is in contrast with the negligible variation of electric field at room temperature, and (b) the evidence of the localized electric field at both electrodes (a larger increase detected at the electrode of lower temperature). The results emphasize the crucial contribution of ionic charges in the electrical conduction processes in the insulation of DC cables. It is also underlined that the interaction between ionic and electronic charges at interfaces should be accounted and further improved in the model.