Process for producing a crosslinked polyolefin insulated power cable

A process for producing a crosslinked polyolefin insulated power cable consisting of a conductor, an inner semiconductive layer formed on the outer surface of said conductor and a crosslinked polyolefin insulating layer formed on said inner semiconductive layer, the process comprising:

• extrusion-coating, on the outer surface of a conductor, (1) a first layer of a material, for the formation of an inner semiconductive layer, comprising a base polymer and N-vinylcarbazole, (2) a second layer of a crosslinkable polyolefin material for the formation of a crosslinked polyolefin insulating layer, said second layer being superimposed on said first layer, and (3) a third layer of a material for the formation of an outer semiconductive layer said third layer being superimposed on said second layer;
• and then
• subjecting the coated conductor to a crosslinking treatment to cause a portion of said N-vinylcarbazole to diffuse into said second layer, thereby increasing the AC breakdown voltage of said second layer, and to form, on the outer surface of the conductor, an inner semiconductive layer, an intermediate crosslinked polyolefin insulating layer containing the diffused N-vinylcarbazole and an outer semiconductive layer.