<p>Detailed knowledge of the electric field in the insulation of mass-impregnated HVDC cables is important in order to understand their breakdown mechanisms and to improve their design. When calculating the local electric field, the wrapped structure of paper and impregnating oil needs to be taken into account. This gives information that is lost when the insulation is treated as a single, homogeneous material, which is done when the macro-scopic electric field is calculated.<br />We have modeled mass-impregnated cable insulation with finite element analysis software and subsequently calculated the local electric field with the finite element method. The wrapped structure of paper and impregnating oil was taken into account.<br />In our model, the magnitude of the local field in the paper was up to twice as high as the magnitude of the macroscopic field. Field enhancements came from oilfilled butt gaps, and particularly from their edges. The geometry of the insulation influenced the magnitude of the field enhancements.</p>
Local Electric Field in Mass-Impregnated HVDC Cables