GB513377A - Improvements in electric cable installations - Google Patents

Abstract

513,377. Cables. CALLENDER'S CABLE & CONSTRUCTION CO., Ltd., and ARMAN, A. N. June 14, 1938, No. 17701. [Class 36] A high-tension cable comprises a conductor 1 surrounded by inner and outer layers 2, 4 of laminated dielectric which are separated by an impervious envelope 3 consisting solely of insulating material, the inner dielectric layer being maintained under pressure (e.g. a pressure of between 150 and 300 pounds per square inch) by compressed gas, such as nitrogen or carbondioxide, contained within the envelope 3. A metallic screen 5 and a lead or like outer impervious sheath 6 complete the cable. The inner dielectric layer may be of dry or preimpregnated paper, the interstices of which are filled by the compressed gas ; or oil-impregnated paper may form the inner dielectric layer, the envelope 3 being a loose fit on the layer to provide a space in which the gas is accommodated. The envelope 3 may be formed of rubber, "Neoprene" or other oil-resistant rubber-like compositions, cellulose products, such as benzyl cellulose or cellulose acetate, or of polyvinyl chloride resins, such as those known under the registered Trade Marks "Mipolam," "Igelit" and "Koroseal." The envelope maybe applied by extrusion, or by lapping the inner dielectric layer with thin tape, the turns of which are subsequently coalesced by heat. The outer dielectric layer 4 may consist of oilimpregnated paper, varnished cloth or paper, cellulose acetate, or acetylated or esterified paper. Specification 439,575 is referred to.