Conduction and partial discharge activity in HVDC cable insulation of lapped polypropylene films

The purpose of the work presented here is to characterise polymeric HVDC cable insulation consisting of lapped thin film polypropylene with respect to DC current conduction and partial discharge activity in air filled butt gaps. The PD activity was found to strongly increase with increasing temperature and applied electric stress. The discharge frequency decreased with time after voltage application and the effect of the void size was found to be of minor importance. These observations agree very well with the proposed theory stating that the discharge frequency will be proportional to the current flowing through the insulation.