GB1473499A - Electric cable joints and terminations - Google Patents

Abstract

1473499 Cable joints or terminations BICC Ltd 21 June 1974 [22 June 1973] 29733/73 Heading H2E In a method of jointing or terminating a cable the dielectric 4 is overlayed with a vulcanizable layer 9 of ethylene homo- or copolymer applied to cover at least the tapered surface 5, heat-shrinkable polyethylene tape 10 is then wound on to build up a thickness greater than that of the untapered dielectric, and the joint or termination is heated to vulcanize layer 9 and bond it to the dielectric 4 and to the tape 10 and to shrink and bond the turns of tape 10. The outer surface of tapes 10 may be restrained against expansion. In the joint shown, for a 15 kV cable, semi-conducting vulcanizable ethylene-polythene elastomer tape 8 is applied over the ferrule 3 up to the cut ends of the conductor screen 7. Insulating tape of the same elastomer is then applied as a single layer 9 to abut but not overlap the dielectric screen 6. A replacement screen 11 is formed using a single layer of semi-conducting carbonloaded polyethylene tape, irradiated but not heat shrinkable, covered by two layers of similar but 40% heat shrinkable tape followed by a temporary layer of fluorinated ethylene-propylene tape 12. A split brass tube 16 acts as an oven and the temperature, raised by the hand application of a propane flame or otherwise, monitored by the thermocouple 14. In another embodiment (not shown) two layers of 40% heat shrinkable polyethylene tapes are substituted for the replacement screen 11. After heat treatment the dielectric screen, outer conductor 1 and sheath are restored conventionally. In a further embodiment (Fig. 2, not shown) layers 12, 13 of tapes woven from wire and oven 16 are replaced by a close fitting mould 17. The dielectric 4 is preferably tapered by a knife or edge tool and may be from a wide range of polymeric materials some of which are specified. The tape 10 may be modified by the inclusion of a small amount of comonomer such as vinyl acetate or ethylacrylate at the formation stage of the tapes.