GB944412A - Improvements relating to high voltage electric installations - Google Patents

Abstract

944,412. Switchgear structures. MASERGLASER & CO. A.G. March 17, 1960 [March 17, 1959; Jan. 21, 1960], No. 9480/60. Heading H2B. [Also in Division H1] In order to reduce the dimensions of high voltage installations such as isolators, busbars, circuit-breakers, &c., the high voltage component or components are insulated by enclosing them in a gas having a dielectric strength greater than that of air which is confined around the component by a thin insulating envelope. The leads to the high voltage components) which extend outside the envelope are enclosed in solid insulation having an external earthed conducting layer which does not extend into the envelope. The component may be arranged in the innermost of a plurality of envelopes each containing a gas and arranged one within another, the gas nearest to the component having the greatest dielectric strength. The walls of the envelope or envelopes may follow an approximately equipotential surface. The envelopes may be of material such as synthetic resin, polythene, terylene, nylon, &c. strengthened with textile or glass silk gauze or tapes and each may have a lining of plastics foil. They may have relief valves and parts of lower tearing strength and, may be surrounded at a distance by earthed wire mesh cages which may be embedded in transparent plastics material. Conductors extending through the envelope are provided with solid insulation of the kind described in Specification 886,290 which has, outside the envelope, an earthed external conducting layer attached to the wire mesh cage. Inside the envelopes irregular or sharp metal members or those carried on supports may be enclosed in solid insulation. The gas used may be air under pressure N 2 , CO 2 , SF 6 , a carbon fluoride such as C 4 F 8 , a gaseous chlorine compound, neon, argon or mixtures. The gas pressure may decrease from the inner envelope to the other envelope. The gas may be circulated so that it can be purified and dried and its temperature or pressure can be controlled. The chamber in which the apparatus is housed may be filled with filtered air or with a gas or gas mixture having a higher dielectric strength. Fig. 1 shows one phase of a high voltage switch gear installation in which insulating envelopes 20-27 enclose the isolators 3, 4 and circuit breaker 7, 8. Admission and outlet pipes 27, 28 are provided for the gas as well as a valve 29 for exhausting the gas from the circuit breaker. Envelope 22 is separated from envelope 25 by a substantially gas-tight plug 30 of elastic foamed plastic. Fig. 3 shows an isolator having a contact pin 56 operated by an insulated shaft 61 by a servomotor 62. The gas is enclosed in a transparent plastic envelope 63 surrounded by a wire mesh screen 64 connected to the external conducting layers on insulation 59, 60 of the H.T. bus-bars 57, 58. A bulge 65 in the plastic envelope encloses an earthed electrode 66 which prevents flashover between poles 54, 55. An installation connecting two three-phase systems is also described (Figs. 2a and 2b, not shown).