Abstract: A high voltage electrical power cable with a stranded central conductor encircled by insulation, a metal tape, metal strips or metal wires following helical paths outwardly of the insulation and a water swellable material at least between the adjacent edges of the tape, strips or wires. Preferably, the water swellable material is included with a polymeric material which is flowable at a temperature at least as low as 100.degree. C., the polymeric material has a 100 gram needle penetration value in the range from 50-100 tenths of a millimeter at 25.degree. C. and the water swellable material has a particle size not greater than 200 microns.

Abstract: Insulation for an electric power cable, and a power cable including such insulation, the insulation having an improved dielectric strength and being irradiation cross-linked polymeric material having mixed therewith carbon black having a particle size in the range from about 200 to about 500 millimicrons, the carbon black content being about 10% to about 40% of the weight of the mixture of carbon black and the polymeric material. Also, the cable insulation may be layers of different density polyethylene, at least one of the layers being the described mixture of polyethylene and carbon black.