GB1458378A - Electric cables - Google Patents

Abstract

1458378 Electric cables BICC Ltd 1 Oct 1974 [2 Oct 1973] 45937/73 Heading H1A A dielectric for an electrical power cable comprises a plurality of tapes composed wholly of at least one synthetic polymeric material with at least part of at least some of the tapes formed of fibres of that material, a compatible non- draining insulating compound (any conventional such compound, but high aromatic or unsaturated hydrocarbons preferred, two specified) filling the pores between fibres (and possibly coating the surfaces of the tapes) and an insulating gas consisting of sulphur hexafluoride alone, or in admixture with one or more of nitrogen and the stable fluorinated and fluorochlorinated hydrocarbon gases filling the interstices between tapes. The dielectric may be formed from fibrous tapes alone, or fibres bonded to one surface or both surfaces of a polymeric foil, or fibres sandwiched between foils or a combination thereof. Suitable materials for the dielectric are listed. Depending on temperature conditions the pressure may be from atmospheric up to 1À7 MN/m.<SP>2</SP>, not sufficient to liquefy the sulphur hexafluoride. A cable Fig. 2 has three metallic conductors 1 about which are conductive plastics tapes 2 and over which is the dielectric 3 as above, and a dielectric screen 4 of conductive plastics tapes. The interstices between cores are occupied by fillers 5 accommodating open helix gas ducts 15. A pressure tight covering of metal sheath 6 and serving 7 completes the cable.