Method for the manufacture of a power cable

Claim 1

In a method for manufacturing a power cable wherein a polymeric, electrically-conducting layer is extruded into surrounding relationship with respect to a cable conductor, an initially thermoplastic, heat cross-linkable, polymeric layer of insulation is extruded at a predetermined temperature into surrounding relationship with respect to the conducting layer, and thereafter cross-linking is caused to occur in said insulation layer by heating the composite under pressure, the improvement which comprises: using for said polymeric, electrically-conducting layer a material characterized by sufficient resistance to indentation at said predetermined extrusion temperature to prevent the same from being deformed or damaged during the extrusion of said insulation layer and during said cross-linking operation, said material being sufficiently resistant to indentation that the same will receive an indentation which amounts to no more than 10 percent of the original thickness of a test specimen of said material, when formed by compression-moulding at 175° C. and when having a thickness of 1.50 mm and a diameter of 15.0 mm, and when such specimen is subjected to loading with a pressure of 13 kp/cm 2 for 5 minutes at a temperature of 125° C. and the indentation is then measured after the specimen with the remaining load has been allowed to cool for one hour at room temperature; and heating said cable to a temperature which is lower than said predetermined temperature but which is within 75° C. thereof prior to said extrusion of said insulation layer.