Oy Nokia Ab

Jukka S Karppo

Matti A Aaltonen

A method of manufacturing a plastic covered highvoltage cable by passing an electrical conductor through two successive separate extrusion heads. In the first extrusion head a conductor shield layer is extruded around said conductor as well as a thin auxiliary insulation layer around the conductor shield layer. In the second extrusion head a main insulation layer is extruded around the auxiliary insulation layer as well as, if preferable, a corona shield layer around the main insulation layer. The auxiliary insulation layer is of the same or electrically equivalent material as the main insulation layer. The auxiliary insulation layer prevents the formation of plastics burr on the surface of the conductor shield layer from during the first extrusion.

Method of manufacturing plastic covered highvoltage cables

An apparatus for continuous curing (vulcanization) of elongated products, such as cables comprising a conductor surrounded by a mantle of a crosslinkable material. The cable is passed longitudinally through a curing tube in which the cable is first subjected to heating in a heating zone for heating the cable to curing temperature and subsequently subjected to cooling. The heating of the cable in the heating zone is carried out by means of heat radiation in a pressurized gas atmosphere and the cooling of the cable in the cooling zone is carried out in the presence of a gas under pressure so that heat is transferred from the heated cable in the cooling zone partially by radiation to the cooled wall of the tube and partly by convection to said cooled gas.

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Helsinki, Finland

Jukka S Karppo