Abstract: This disclosure deals with the minimization of electric stresses and the increase of breakdown-withstanding capabilities in DC insulation systems or conductivity, or conductance and resistance, within the insulation media. The stress is kept at a minimum by arranging the layers of insulations to follow a particular pattern based on conductivity constants of the material at its distance from the conductor.

Abstract: Insulation is extruded onto a conductor and immediately quench-cooled to obtain solidification for retaining concentricity of conductor and envelope. The envelope is reheated under pressure to melt a surface zone, followed by gradual cooling whereby the melted zone migrates into the interior. Reheating under pressure and gradual cooling, possibly also under pressure, improves texture, and provides for a more ordered crystal structure and/or fuller crosslinking. Following extrusion, and on reheating, the cable is freely suspended and assumes catenoidal contour while advancing to avoid sliding contact of the outer surface until adequately stable solidification has taken place.