GB1227350A - Improvements in cable terminations - Google Patents

Abstract

1,227,350. Electric couplings. BRITISH INSULATED CALLENDER'S CABLES Ltd. 29 Nov., 1968 [30 Nov., 1967], No. 54609/67. Heading H2E. A termination for a coaxial superconducting cable comprises a plurality of coaxial conductors electrically connecting the conductors of the cable to those of a coaxial terminal, a tubular insulating envelope sealed at one end and axially movable relative to the cryogenic envelope of the cable, and sealed at the other end to the coaxial terminal; and insulating spacing and vacuum sealing means between the terminal conductors, the termination being so shaped that it reduces transfer of heat by direct radiation from the conductors of the terminal to those of the cable. In a superconducting cable comprising three tubular conductors 1, enclosing an evacuated space 5 and separated from each other and from an outer tubular cryogenic envelope 2 by annular evacuated spaces 3 (the spacers not being shown), each of conductors 1 is welded at 7 to a separate part-spherical conductor 6, which itself is welded at 9 to a conductor 8 of the coaxial terminal. The conductors 6, 8 are cooled by an internal cryogenic fluid duct. The sinuous passages between the conductors prevent direct radiation reaching the cable conductors. The coaxial conductors 8 increase in diameter from the point 9 to a maximum diameter, after which they become cylindrical, the cylindrical portion being either formed integrally with the first portion, or formed separately and welded on, so that as the temperature rises away from the superconductive state, the conductors still carry the same current. At the point where the conductors 8 emerge into the atmosphere, they are spaced apart by annular insulating spacers which also form vacuum seals. Inside the innermost, spacer is a central cryogenic fluid supply duct 12, there being an expansible member 13 to permit said duct longitudinal movement. A similar member 24 permits the tubular glass insulator 25 to move longitudinally relative to the cryogenic envelope 2, there also being provided thermal and electrical shields 26 to cut off radially-entering radiation. The duct 12, which has two heat shields 14, 15, feeds a stainless steel generally spherical manifold 16, through the walls of which pass glass cryogenic fluid distributing ducts to the hollow conductors 6. The ducts are allowed relative radial movement by the expansible members, 18. The conductors exposed to the atmosphere are provided with glass outlet ducts 22, with corona shields 23 for the cryogenic fluid. The ducts for cooling fluid may alternatively be secured externally to the conductors, in which case they may also act as conductor spacers. The sinuous spaces are formed by the conductors of the cable and/or the termination first increasing and then reducing in diameter. When the innermost conductors of the cable and the termination are both evacuated tubes, a heat shield may be formed by staggered baffles projecting from the tube walls.