GB610576A - Improvements in and relating to methods of and apparatus for manufacturing gas-filled cable - Google Patents

Abstract

610,576. Electric cables. BRITISH THOMSON-HOUSTON CO., Ltd. April 10, 1946, No. 11020. Convention date, April 17, 1945. [Class 36] A method of making a cable having a stranded hollow-core conductor and fibrous insulation consists of removing air and impurities from the core and insulation, impregnating the insulation with liquid, draining off the surplus liquid, applying an inert gas under pressure to the hollow core to force out excess liquid, and finally applying an impervious sheath. The conductor, wrapped with fibrous insulation is wound on a cable drum and placed in the impregnating tank 11, Fig. 2, leads 29 being connected between cable terminals 5 and terminal blocks 28. The gas supply tubes 6 on the cable are connected to supply tubes 30 in each of which is an insulating portion 32. The tank 11 is sealed and evacuated by operation of valve 17, a heating medium is admitted to chamber 26 and a heating current is passed through the cable. After the impurities have been removed by heat and drying, impregnating fluid is admitted by means of valve 12 and allowed to cover the drum. The cable is cooled, nitrogen admitted through valve 20 and surplus oil is drained off by means of valve 15. The tank is re-evacuated and the cable cooled. Any excess fluid still remaining is removed by admitting nitrogen through valve 20 and then applying nitrogen under pressure to the hollow core from supply pipe 21, thus forcing excess fluid out. When the draining process is complete a lead sheath is applied to the cable. Cable sleeves and like end constructions.- During transit the ends of the cable are sealed as shown in Fig. 6. A pull-bolt 37 is inserted under a few of the conductor strands, the remaining strands being cut off at 38. The strands surrounding the bolt are held by means of binding wires 40. The end is completed by a wipe-soldered joint 41 and a threaded plug 43. The opposite end is sealed by means of a flared tube 47, wipe-soldered joint 49 and valve 50 for the supply of gas. Fig. 3 shows the terminal arrangement used during the impregnating process. A gas supply tube 6 is sealed into the electric terminal 5, and firmly secured in the hollow core of the conductor 2.