Method in the manufacturing of an insulated electric high voltage DC termination or joint

A method in the manufacturing of an insulated electric high voltage DC termination or joint comprising the steps of:

• providing an insulated electric high voltage DC cable comprising a high voltage DC conductor, a polymer based insulation system surrounding the high voltage DC conductor, the polymer based insulation system comprising an insulation layer and a semiconducting layer surrounding the insulation layer, and a grounding layer surrounding the semiconducting layer;
• removing the grounding layer and the semiconducting layer in at least one end portion of the high voltage DC cable, thereby exposing the insulation layer of the polymer based insulation system in the at least one end portion of the high voltage DC cable;
• mounting a field grading adapter or joint body in the at least one end portion of the high voltage DC cable, thereby covering the insulation layer of the polymer based insulation system in the at least one end portion of the high voltage DC cable, the field grading adapter or joint body being part of the high voltage DC termination or joint, wherein at least one substance is present in the insulation layer of the polymer based insulation system in the at least one end portion of the high voltage DC cable in a non-homogenous distribution;
• and
• subjecting the insulation layer of the polymer based insulation system in the at least one end portion of the high voltage DC cable for a heat treatment procedure, while being covered by the mounted field grading adapter or joint body, thereby equalizing a concentration of the at least one substance in the insulation layer of the polymer based insulation system in the at least one end portion of the high voltage DC cable.