Simulation of ionic contribution on space charge characteristics of XLPE insulations

Contribution of ionic conduction to space charge and electric field dynamics in XLPE insulation were simulated with bipolar charge transport model. Physical processes and relevant parameters for electronic charge carriers were fixed to typically accepted ones found in the literature while ionic contribution was modelled by adopting theory of ionic conduction in liquid dielectrics. Simulations were performed for a 1 mm thick flat XLPE sample. Results indicated that presence of impurities (or ionic charges) leads to accumulation of hetero-charges in the insulation. While constant temperature across the insulation thickness results to a symmetrical hetero-charge accumulation, having a temperature gradient results to hetero-charges being concentrated closer to low temperature electrode. In general effect of ionic charges on electric field distribution is less significant under temperature gradient as compared to constant temperature. Space charge accumulation is not significantly affected by field dependency of dissociation rate, which primary characterized the ion generation rate.