GB524989A - Improvements in or relating to electric cables - Google Patents

Abstract

524,989. Electric cables and couplings. PIRELLI-GENERAL CABLE WORKS, Ltd., and HORLEY, R. E. Jan. 12, 1939, No. 1035. [Classes 36 and 38 (i)] In an electric cable, the dielectric material is surrounded with,a metal &c. sheath impervious to gas, around which and spaced therefrom is a second similarly impervious sheath, the space within the inner sheath and that between the sheaths being charged with gas under pressure. The two spaces may be charged with different gases and at different pressures. In Fig. 1, the conductor 1 has insulation 2 within a metal sheath 3 with reinforcement 4 about which, spaced by members 5, is a second metal sheath 6 with reinforcement 7 and protective covering 8. The space within the sheath 3, and that between the sheaths 3, 6 are charged with gas. At a joint, Fig. 4, the spaces within the sheath 3 and between the sheaths 3, 6 of one section may be connected to the corresponding spaces of an adjoining section by means of sleeves 10, 12 with plumbed joints, 11, 13 ; tubular connections 14, 15 may be provided for supply of gas and/or communication with pressure-indicating or warning devices. In another form, Fig. 5, each of the joined cables has an inner gas-tight sealing end 16 through which the conductors 1 project for connection by a flexible member 17 ; one sealing end 16 is wiped to the sheath 3 at 11 and the other fits in a diaphragm 18 extending across the sleeve 12 and sweated at 20 to the other sheath 3. An insulating sleeve 21 is located between the sealing ends 16 and the sleeve 12, the gas-filled spaces within one cable being cut off from those of the other. A terminal device, Fig. 6, has the inner sheath 3 fitted within a sleeve 16 through the end of which the end of the conductor projects to form a plug 22 co-operating with a socket formed in a metal cup 23 of an insulator 24 communicating with the gas-filled space between the sheaths 3, 6. The insulation within the inner sheath may be impregnated with an oil &c. which develops gas under the action of the electric field if the internal pressure falls unduly. Reinforcement of the inner sheath may be omitted. A cable may have a higher pressure within the sheath 3 than between the sheaths 3, 6, and an alarm device may be connected to the sheath 6 to give warning of a fall in pressure due to a leak in the sheath 6 or a rise due to a leak in the sheath 3.