Modeling Charge Transport in Insulating Materials for High Voltage Direct Current (HVDC) Application

High Voltage Direct-Current (HVDC) is rapidly growing for long-distance power transmission applications where typical AC solutions are not efficient (generally >80km). However, extruded insulation material systems utilized in AC applications are challenged in DC applications due to the accumulation of injected charge within the insulation, which can significantly alter the electrical field and subject the insulation system to electrical stresses that are many times the “design stress” (Laplacian). Charge accumulation within polymeric insulating systems has been related to the temperature and stress-dependence of conductivity. A steady-state solution for the space charge profile and resulting electric field has been developed. However, the assumption of steady state avoids the treatment of charge injection and the rate of charge transport, and may not capture transient phenomena which are entirely relevant for the DC application. Therefore, a computational model of the transient development of the space charge field can provide valuable insight into the development of materials suitable for extruded DC power cables. We developed a finite element analysis method treating the charge injection process and conduction process based on a trapped-charge hopping mechanism.