Relative importance of trapping and extraction in the simulation of space charge distribution in polymeric insulators under DC potentials

Under high DC voltages polymeric insulators tend to accumulate space charge, leading to a deviation from the designed electric field for the system. Consequently local fields may reach high enough values to cause ageing and eventual failure. A particularly dangerous instance is the appearance of heterocharge at one or both electrodes. The origin for such charge is not very clear, it may be due to the field separation of charged entities intrinsic to the insulation or alternatively to the injection and transit of charges. Here we present a simple simulation model for the latter situation in which we identify the conditions required for the formation of heterocharges. The model led to interesting results showing a high dependence of the space charge distribution on the extraction rate and on the trapping rate.