GB967012A - Improvements in or relating to electric cables with compressed gas insulation - Google Patents

Abstract

967,012. Gas-filled cables. CENTRAL ELECTRICITY GENERATING BOARD. Aug. 7, 1963 [May 7, 1962], No. 17548/62. Heading H1A. A compressed gas insulated coaxial cable comprises an inner conductor 10 supported within an outer concentric support 12 by a plurality of dielectric webs 15 extending in a direction such that, in any radial plane, the length of the path through the solid dielectric is small compared with the length through the gas. As shown, the inner conductor 10 comprises a stranded conductor of copper or aluminium covered by an extruded layer 11 of conductive material or a layer of conductive tapes, e.g. conductive polythene, which forms a conductor screen. This screen 11 and a similar core screen 12, which is also backed by further metallic tapes, are covered with layers 13 and 14 of insulating material which are said to make the breakdown strength less dependent on the surface roughness of the screens 11 and 12. Layers 13, 14 and webs 15, which extend both radially and circumferentially and do not overlap each other, may be simultaneously extruded, for example from polypropylene. The compressed gas used is nitrogen with from e.g. 10 to 20% by volume, of sulphur hexafluoride and is maintained at a pressure between 200 and 500 pounds per square inch. Fig. 2 (not shown) illustrates a termination for this cable using a stress cone comprising a series of concentric conducting foils over which layer 12 is continued and connected to the outermost.