GB478336A - Improvements in or relating to electric cables - Google Patents

Abstract

478,336. Cables. SOC. ITALIANA PIRELLI. April 9, 1936, No. 10486. Void. Convention date, June 13, 1935. [Class 36] A cable comprises one or more conductors provided with a covering of porous insulating material impregnated with a fluid insulating composition and enclosed in an impermeable sheath, the insulating fluid being saturated, at a pressure considerably higher than the degree of vacuum ordinarily used in effecting impregnation, with a gas and/or vapour having an "ionization potential gradient" greater than that of air. Suitable gases are ethylene, acetylene and nitrous oxide : suitable vapours are carbon bisulphide and mercaptans. In making the cable, the porous material and insulating fluid are first degasefied and the insulated conductors are then immersed in the fluid, preferably hot, and the gas introduced, after a suitable interval, above the surface of the fluid: the cable is then cooled under pressure and sheathed. Alternatively the insulation and impregnating fluid are separately impregnated with gas and degasefied, after which fluid impregnation is effected. When using a mixture of gas and vapour, the mixture may be prepared by bubbling the gas through the vaporizable liquid.