High voltage cable insulators with moulded rubber sheaths - for greater resistance to thermal or mechanical shock than ceramic covered insulators

摘要

Insulators for supporting high voltage cables comprise a core rod of strong insulating materials with integral collars to secure an insulating sheath made from shock-resistant rubber which is moulded on to the core under deaerated conditions, i.e. 1mm Hg pressure. An integral metal cap is fitted on each end of the insulator. The Core may be a conventional rod of glass filaments impregnated with epoxy or polyester resin. The sheath material 13 pref. tough and impact resistant at -50 degrees to +70 degrees C, has hardness of 30-40 degrees Shore A and a tear strength of approx. 16 kg/cm. Pref. the sheat is made of polyurethane or silicone rubber, has annular ribs and is an effective insulator at 175 kV. The sheath/core interface may be adhesive-bonded ne.g. using "Dow Corning 1210" primer (RTM) for a silicone rubber sheath of Liofol UK 4500 (RTM - Henkel) for a polyurethane sheath) near the ends of the sheath, leaving the central portions of the sheath free to slide over the core body to relieve differential expansion effects whilst remaining close fitting. Insulators are less fragile than ceramic insulators, and more resistant to interfacial penetration by air or moisture and consequent risk of insulation breakdown.