GB1262871A - Method of jointing and terminating electric cables - Google Patents

Abstract

1,262,871. Welding by fusion and pressure. BRITISH INSULATED CALLENDER'S CABLES Ltd. 10 April, 1969 [11 April, 1968; 10 June, 1968 (2); 11 Nov., 1968 (2)], Nos. 17484/68, 27499/68, 27500/68, 53371/68 and 53372/68. Heading B3R. [Also in Division H2] In jointing or terminating by welding an electric cable having a stranded conductor through the interstices of which liquid impregnant can pass, the stranded conductor is surrounded by a heat sink, metal in a molten state is applied to the whole of the end face of the conductor or between the end face of the conductor and the end of the terminal member or the end of the other conductor and liquid impregnant is removed from the interstices in the region of the end of the stranded conductor by applying vacuum to the stranded conductor. To join two oil-filled cables a heat sink 1 of copper if the conductors are of aluminium or of mild or stainless steel if the conductors are of copper is assembled about each conductor end 4, the sink having its end face 2 inclined, and the conductors are cut at the angle of the heat sink. An annular groove 5 in the inner surface of the heat sink is connected by a passage 6 to a vacuum pump whereby oil is drawn from the conductor, whose opposite end is connected to an oil reservoir, until oil no longer flows from the cut surface. The cut surface is washed and a thin layer of weld metal is applied to the cut face by MIG welding. With both conductors so prepared they are aligned in another heat sink forming a mould which provides access to the V-shaped gap between the ends, the mould having annular grooves connected to vacuum. The V gap is filled with weld metal by MIG welding using argon and subsequent to removal of the heat sink the joint is filled or milled. A separate manifold may be provided between the heat sink and the cut back end instead of in the heat sink or an extra manifold connected to insert gas may be used to facilitate oil clearance. Instead of initially coating the cut surface with weld metal it may be hammered. In a modification the end of a conductor is provided with its weld coating layer as before and the prepared end is then inserted in a composite heat sink 17, Fig. 6, comprising an inner part 18, threaded and of the same metal as the conductor, and an outer removable part 19. A vacuum manifold 20 is also employed. The space 21 is filled by MIG welding with weld metal to join the sleeve 18 to the conductor. After removal of the parts 19, 20 a terminal is screwed on to the sleeve 18, the terminal being copper if the conductor is of aluminium. In further modifications the heat sink about the screwed sleeve becomes part of the connection, in one case the inner sleeve is screwed and sweated to the heat sink and in another a tapered aluminium inner sleeve is friction welded or flash butt welded in a copper body prior to the welding of the sleeve to the conductor. The impregnant may, instead of oil, be an oil-wax mixture which becomes liquid at the temperature of jointing.