GB1262872A - Method of jointing and terminating electric cables - Google Patents

Abstract

1,262,872. Welding by fusion. BRITISH INSULATED CALLENDER'S CABLES Ltd. 10 April, 1969 [11 April, 1968; 10 June, 1968 (2); 11 Nov., 1968 (2)], Nos. 17308/69, 17309/69, 17310/69, 17311/69 and 17312/69. Divided out of 1,262,871. Heading B3R. [Also in Division H2] In jointing or terminating by welding an electric cable having a hollow stranded conductor through the bore and interstices of which liquid impregnant can pass, a mandrel is inserted in the end of the bore, 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. A headed mandrel 1 is driven into the bore of the end of an oil-filled hollow cable 2, after an internal support 3 is cut back, to expand the strands and form radial passages therein. The end 7 is contracted on to the neck 8 of the mandrel and a heat sink 12 of copper if the conductor is of aluminium or of mild or stainless steel if the conductor is of copper is assembled about the conductor, the inclined end face 13 of the heat sink assisting in cutting the end of the conductor, with the end of the mandrel, to the shape shown in Fig. 3. An annular groove 15 in the heat sink is connected to a vacuum source to prevent flow of oil from the cut end, a reservoir of oil being connected to the other end of the cable, and the cut surface 17 of the conductor is washed and then a layer of weld metal is applied by MIG welding to the cut surface. The heat sink is removed and with another similarly prepared cable end is arranged in a heat sink 20, Fig. 5, including a ferrule 21 and forming a mould within which the prepared ends form a V gap 30. Holes 25 are provided in the ferrule to provide for outflow of oil from holes in the mandrel and the radial gaps in the strands and annular grooves 27 in the heat sink are connected to a vacuum source. The gap between the ends is filled with weld metal by MIG welding and an outer part 22 of the heat sink is removed, the ferrule remaining as part of the joint. In a modification the second cable end is replaced by a solid joint member having oil flow passages and a joint is similarly made, except that no initial weld coating of the solid member is required. Inert gas may be applied to the end of the cable to assist oil clearance. In modifications, an oil passage is maintained through the end of the conductor by employing a tubular mandrel, an additional mandrel being inserted in the tubular mandrel to prevent burning through during welding. When connecting two cable ends, a tube is fitted, possibly screwed, in the tubular mandrels and preferably having a branch for oil escape during jointing. The tube and part of the branch are included in the MIG welded joint with the branch finally plugged. If direct connection between the cables is not required two angle tubes are employed for oil escape from the tubular mandrels. A simple tube may be inserted into the mandrels when the ends of the conductors are cut to frusto-conical shape, two heat sinks then being employed for the final welding step which includes rotating a MIG welding gun about the conductor axes. The end of the conductor need not be weld metal coated, being merely hammered for sealing.