Patent GB-561078-A (GB)
Title: Improvements in air or gas blast electric switches
IPC: H01H33/16
Filed: 1942-07-30
Abstract: 561,078. Gas-blast switches. FLUR. SCHEIM, C. H., and METROPOLITANVICKERS ELECTRICAL CO., Ltd. July 30, 1942, No. 10682. [Class 38 (v)] Gas-blast switches employing nozzle-contacts or insulating nozzles to guide the blast have the pressure on the discharge side of the nozzle increased or otherwise controlled by means of a valve responsive also to pressure on the inlet side, so as to increase the gapdielectric strength' and compensate for arc - temperature changes. In a simple form, the insulating nozzle itself, or a nozzle contact, is movable to form a valve, and has two unequal piston surfaces subject to the inlet and discharge pressures, the movable contact being withdrawn through the nozzle, or from it, against the blast, Fig. 1 (not shown). Alternatively, the insulating nozzle is formed at the top of a chamber to which blast is supplied, and is closed by a valve so. as to be subject to the dischargepressure, a smaller upper surface of the valve being subject to the inlet-pressure through a pipe, Fig. 2 (not shown). In both these forms' the contact is moved pneumatically against spring action, and accordingly, where a series isolating switch is employed and more particularly where automatic reclosing means are provided for the arrangement as a whole, it is desirable to'maintain the blast-contacts open in a pressure-gas atmosphere, as in Fig. 3. The movable contact 9a is raised by a piston 36 in a cylinder 35 to which air is admitted from chamber 1 through aperture 49 and passage 50, the air also passing through segmented contact 31 to the upper face of piston 41 lying within flange 43. The lower face co-operating with lip 47 forms a valve controlling the discharge to the space between structural members 32, 33 in accordance with the relative pressures. At a given point in the opening movement, ports 56, 57 pass air to the outer cylinder 53 and through restricted passages 54, 55 in members 32, 33, to the upper face of flange 43, so closing the valve 41 after a delay determined by the size of passages 54, 55 and holding the contacts separated in high-pressure atmosphere so long as the main control valve is open, and allowing the series-isolator to reclose. The lower contact 2a may be tubular, or may be movable in the manner of the contact 9a. Two of such blast-switches may be arranged in series, one over the other, with the fixed contact of the second mounted on the top of cylinder 35 and the blast and operating fluid supplied through a pipe leading from chamber 1 into the corresponding chamber of the second, Fig. 4 (not shown). In Fig. 6, a resistance 81 shunts the main break (not shown) in the manner described in Specification 541,949, and is introduced by auxiliary electrodes, of which 73 is fixed to cylinder 35 and the other 74 is movable by piston 90 so as to separate from 73 in a nozzle 72 after the main piston has uncovered a port 64. The auxiliary electrodes are subjected to a blast and may be controlled by a valve 93. Alternatively, the upper electrode also may be fixed at a relatively short distance from the lower one, Fig. 5 (not shown), and a valve provided for it. In both forms, the valvemay be completely closed, as in Fig. 3, after the auxiliary arc is quenched.