Patent ID: 8398803

Claim:
A method for providing an insulated electric high voltage DC cable or a high voltage DC termination or joint, the method comprising: providing a polymer based insulation system comprising a compounded polymer composition, wherein providing the polymer based insulation system comprises exposing the polymer based insulation system to a heat treatment procedure while an outer surface of the polymer based insulation system is covered by a cover impermeable to at least one substance present in the polymer based insulation system in a non-homogenous distribution, thereby equalizing a concentration of the at least one substance in the polymer based insulation system, wherein the method is a method for production of insulated electric high voltage DC cable, and wherein providing a polymer based insulation system includes extruding the polymer based insulation system around a conductor, and wherein the extruded DC cable is rolled up on a drum or in a vessel and the roll of extruded DC cable is covered by the cover impermeable to the at least one substance.