GB1048462A - - Google Patents

Abstract

1,048,462. Armoured cables. J. A. GIARO. Feb. 4, 1964 [Feb. 5, 1963; Nov. 18, 1963], No. 4691/64. Heading H1A. The armour of a power transmission cable impregnated with an insulated liquid is prestressed so as to develop in the cold cable an internal pressure sufficient to prevent the formation of voids, the dimensions and cabling pitch being determined in accordance with the following equations: where V is the volume of the cable and V 3 that of the armour; K and K 1 are constants depending on the units; E is Young's modulus for the armour in the axial direction of the cable; A is a number less than the unit elongation corresponding to the elastic limit of the armour; b is the ratio between the increase in volume #V 1 resulting from the cold pressure P 1 and the change in volume #V 2 brought about by the heating of the cable; and α is the pitch angle of the armour. The Specification states that for the least volume of armour, #V 1 should equal #V 2 , i.e. b = 1. A cable is described with reference to Fig. 6 (not shown) in which a single-phase conductor having an oval conductor surrounded by, in turn, an oval semi-conductive layer, oil-impregnated paper, a composite layer of semi-conductive tapes and metallized paper and copper tapes, a lead sheath with space between it and the insulation to facilitate pre-pressuring, a padding sheath of P.V.C. to make the cable circular, a layer of textile strip, a layer of flat armouring wires, a layer of round armouring wires, a further layer of textile strip and a P.V.C. sheath. A threephase cable in a triangular sheath with multilayer circular armouring is also described (Fig. 7, not shown), ducts being provided for the impregnating fluid. A single-phase cable with a central impregnating duct is also described (Fig. 8, not shown).