GB1280762A - Improvements in or relating to electric cables - Google Patents

Abstract

1280762 Cables CENTRAL ELECTRICITY GENERATING BOARD 19 April 1971 [27 Feb 1970] 9691/70 Heading H1A A cable with compressed gas insulation e.g. sulphur hexafluoride, has conductors 10, 11, 12 which may be stranded, and an outer conductive sheath 18, possibly flexible and corrugated. A number of spacers 16, 17 having low permittivity and low dielectric loss may be used or, alternatively a single extruded spacer may extend along the whole or a substantial portion of the cable length. The spacers have a number of radial webs 13, 14, 15 equal to the number of conductors and conforming to their helical lay. Materials suitable for the spacers which can be injection moulded, are polyphenylene oxide, polysulphone or a polycarbonate; if a single long spacer is required, a material suitable for extruding e.g. polypropylene, is used. If a number of spacers are used then the conductors are clipped together between them with either metal or insulating clips. Each conductor, especially if of aluminium may be formed from extrusions which fit together to give each conductor its cylindrical shape. An electrical stress relieving conductive coating, e.g. plastics material with a conductive filler, and an outer plastics covering may be provided on each conductor. Each conductor may be provided with a corrugated metal sheath. If a rigid pipe-line is used for the outer sheath then the inner conductor assembly can be formed separately and stored on a drum, the flexible inner assembly then being led into the pipe-line when required. If rigid inner conductors are used then they would preferably be aligned parallel to the axis of the outer rigid sheath, the spacer webs then extending in flat radial planes.