GB513959A - Improvements in electric cables and joints therefor - Google Patents

Abstract

513,959. Cables and cable joints. BEAVER, C. J., DAVEY, E. L., and GLOVER & CO., Ltd., W. T. April 23, 1938, No. 12237. [Classes 36 and 38 (i)] A cable or joint is insulated by wrappings of paper pre-impregnated with a material which remains solid or viscous under normal working conditions of the cable or joint, the interstices of the wrapping being filled with gas at atmospheric or higher pressure and the permittivity of the insulation being adjusted from point to point in the radial thickness of the insulation by varying the proportion of the radial dimensions b, Fig. 2, of the gas spaces between adjacent layers of impregnated paper to the thickness t of the paper of the adjacent layers. As shown in Fig. 2, the gas spaces may be formed by embossing depressions 8 in the impregnated paper tapes so as to produce projections 9 which space adjacent layers of tapes. The layers of paper 2, Fig..1, near the conductor 1 may consist of plain paper so that the gas layers are of negligible thickness, whilst the central and outer layers 3, 4 of insulation are of embossed paper, the outer layers being embossed to a greater extent than the central layers ; the permittivity of the insulation thereby decreases outwardly from the conductor in three stages. Fig. 5 shows a joint between two cable ends. The two conductors are joined by a ferrule 17 over which and the tapered ends of the conductor insulation 18 is wrapped plain permanently impregnated paper 16. A bakelised paper tube 19 surrounds the paper wrapping 16, the tube being wrapped with embossed permanently impregnated paper 20 over which is applied a wrapping of varnished silk tape 21. An outer conducting tape may be applied over the joint to relieve from electric stress the compound with which the space 23 within the joint sleeve 22 may be filled. Specification 393,694 is referred to.