DC conductivity of voltalit epoxy spacers in SF6

In order to determine the stremes in high voltage DC cable accessering containing a combination of Voltalit (a proprietary epoxy Insulation), SF4 and paper/oil inxulation, a knowledge of the surface and bulk conductivily of the Voltalit is required. It ii also necessary to determine the coefficient govering the dependence of both conductivities with temperature and stress, and the variation of conductivities with time after the application of a itep function of direct voltage. Although the bulk conductity of Voltalit has been determined previously, the surface conductlvity In an environment of SF6 it not available. The time dependence of both bulk and surface conductvities after the application of a direct voltage are also unknown. Measurements are made over the range of stress and temprature expected in cable accessories, and equations relating both bulk and surface conductivities with stress and temperature determined. The variation of conductiviiy with time after the application of a step voltage is also presented