Patent GB-967853-A (GB)
Title: Improvements relating to high-voltage insulation and insulating components
Inventor: SCALES WILLIAM PERRY
IPC: H02G15/107
Filed: 1960-03-25
Abstract: 967,853. Insulators; cable end sleeves; cable joints; two-part couplings. A. REYROLLE & CO. Ltd. March 22, 1961 [March 25, 1960; Jan. 11, 1961]. Nos. 10755/60 and 1129/61. Headings H2C and H2E. [Also in Divisions B5 and H1] High-voltage insulation comprises a skeleton of insulating material formed of laminations of " expanded " sheet material whose overall thickness is many times the thickness of the sheet, the skeleton having voids therein and being embedded in a solidified dielectric material comprising a mixture of synthetic casting resin and an organic filler, which fills the voids. Titanium dioxide may be used as the filler to increase the permittivity. The preferred dielectric is a silica-filled casting resin in which the skeleton is immersed during curing. The " expanded " sheet material is preferably corrugated cardboard of the form shown in Fig. 3 with a plain facing sheet 13 fixed by adhesive to a " fluter " 14. Alternatively the sheet material may be paper tubes glued to a backing sheet; paper sheet with dimples pressed out; or a stiff paper sheet with tags pressed out, and may be partly cured before use. Bushing insulators (Fig. 1) may be formed by wrapping layers of " expanded " sheet 11 around a conductor 10. Each lamination may have on its plain face a perforated aluminium foil 15 for stress-grading. The insulator is then placed in a mould filled with a casting resin which is then cured. Cable terminations (Fig. 29) may be formed by " stepping" the cable insulation 201 and winding the cable end with similar laminations 206 and stress-grading foil 203, the whole being immersed in casting resin in a mould and cured. Cable joints for a single phase cable may be made by jointing and taping the conductor conventionally but surrounding the conductor on one side of the joint with an insulator as shown in Fig. 1, but with a centrally moulded flange which contacts a joint cover to form an oil seal, the space between the insulator and the frustoconical end of the joint cover being filled with oil (Fig. 21, not shown). A three-phase joint may be made similarly, the insulator comprising three insulators according to Fig. 1, within one moulding. Each individual insulator is surrounded by a spiral spring electrically connected to the outer layer of foil, for stress-grading purposes (Fig. 22, not shown). In a further modification (Fig. 28), an insulator 180 is constructed of " expanded " layers 182 and foil 181 and cured in a mould to form re-entrant cones at each end. Incorporated in the insulator 180 is a metallic socket 184 into which are plugged fittings 186 on the conductor 187. A resin sleeve 195 surrounds the joint and is coupled to the cable sheath 190 by conical end flanges 192. The sleeve 195 is filled with oil, and a spring 197 surrounds the sleeve for strapping together the cable sheathing. In each case the insulator is normally prefabricated, but could be made up on site. A joint particularly designed for construction on site is shown in Fig. 25. The conductors 158 are mechanically jointed and surrounded by a number of split tubes 160 of " expanded " paper temporarily held in place by crepe paper. A metal sleeve 162 and end caps 163 are added and the joint filled with oil. The earthed cable-sheath 177 is electrically connected to a foil insert 161 by means of a flared funnel 178 of wire mesh surrounded by a flattened helical spring 179. Specification 967,855 is referred to.