DC electric field distribution in planar dielectric in the presence of space charge

Electric field in a dielectric material under dc conditions is determined by conductivity of the material. It is well known that the dc conductivity is a function of both temperature and electric field. This is generally not serious issue for a thinner planar sample as the temperature gradient is not great and the applied field is uniform across the sample. However, in the presence of space charge, electric field will be modified. As a result, the conductivity varies with the position, leading to change in electric field distribution. In this paper, we present a numerical simulation of electric field considering the effect of space charge. Space charge distributions were obtained from low density polyethylene (LDPE) and crosslinked polyethylene (XLPE) subjected to high dc voltage. Homocharge was formed in LDPE while heterocharge in XLPE. Electric field obtained from simulation has been compared with that without considering conductivity effect. It has been found that electric field retains its general shape. However, the maximum field has been significantly modified.