GB1073606A - Improvements in or relating to electric cables with compressed gas insulation - Google Patents

Abstract

1,073,606. Gas-filled cables. CENTRAL ELECTRICITY GENERATING BOARD. Nov. 10, 1965 [Jan. 11, 1965], No. 1216/65. Addition to 967,012. Heading H1A. In a compressed gas insulated cable, an inner conductor is located within a concentric support by means of a plurality of separate spacers of dielectric material each consisting of an inner tube, or part of a tube joined to a coaxial outer tube or part of a tube by webs extending in a direction such that, in any radial plane, the length of the path through the solid dielectric material is small compared with that through the gas. As shown in longitudinal section, a stranded or segmental copper or aluminium conductor 1 is surrounded by a screen 2 of extruded or lapped tapes of conductive material which in turn is surrounded by an insulating layer 3. Spacers 4 consist of tubular portions 10 and 12 joined together by webs 11. Inner portion 10 is a sliding fit on layer 3 and has an axial length shorter than that of outer portion 12. Adjacent outer portions are connected by a linking element 5 engaging grooves 13. The outer support consists of lapped layers of insulating and conducting material. As best seen in Fig. 2 (not shown), the webs lie in planes which are non- radial but parallel to or inclined to the axis of the cable. To manufacture the cable, the injection-moulded spacers may be assembled with the outer layers and drawn into an oversized aluminium tube. The screened insulated conductor is drawn through the assembly and the aluminium tube passed through a sinking die or corrugating head. Alternatively, the spacer elements may consist of semi-circular or other part-circular elements which can be fitted round the conductor and are bound together by the outer layers. The gas insulation may be sulphur hexafluoride with or without nitrogen at a pressure between 200 and 500 p.s.i.