GB842986A - Improvements in and relating to electrical circuit-breaker of the gas blast type - Google Patents

Abstract

842,986. Gas-blast switches. GENERAL ELECTRIC CO. Sept. 19, 1956 [Sept. 21, 1955], No. 28677/56. Class 38 (5). In a gas-blast switch having a first piston 52 connected to movable contacts 28 and a second piston 51 connected to a blast valve 40, the pistons abut one another when the contacts and valve are closed. The admission of gas under pressure to the cylinder 32 containing the pistons causes the second piston 51 to move to open the valve 40, the second piston 51 also moving the first piston 52 to open the contacts 28, 25. After a predetermined travel, the first piston 52 uncovers a by-pass 85 to admit pressure gas between the pistons to hold the first piston 52 and the contacts 28 in the open position and to move the second piston back to the position in which the blast valve is closed. The switch is of the kind in which the chamber 11 is maintained filled with gas under pressure and the valve 40 opens outlets extending from arcing electrode nozzles 38. In Fig. 1, the moving contacts 28 are connected by links to a crosshead 59 which is biased to the closed position shown by a compression spring 64, this spring closing the contacts when the cylinder 32 is vented to atmosphere. In this arrangement the cylinder 32 to the right of the piston 52 serves as a dashpot, but in Fig. 5 the dashpot action is provided by a further piston 131. In this Figure, the moving contacts are biased by overcentre springs 125 and the contacts are reclosed when the cylinder 32 is vented to atmosphere by the pressure gas in the chamber acting on the piston 131 which has a larger working surface on its right-hand side. The switch is controlled by a two-way valve 77 which is moved from the position of Fig. 1 to that of Fig. 4 by a spring 79 when a protective relay 83 or push-button switch 82 is operated to energize a solenoid 81 and release a latch 80. In the latter position, gas is supplied through a port 75 and a duct 72 to the cylinder 32 to open the contacts. To reclose the contacts, the valve 77 is moved up to connect the duct 72 to atmosphere and is relatched when a solenoid 94 is energized on the closing of a push-button switch 95. The solenoid also closes contacts 96 to energize an " anti-pumping " relay 97 which closes contacts 99a to complete a holding circuit for itself and opens contacts 98 to de-energize the solenoid 94, so that repeated reclosures on to a fault, whilst the switch 95 is maintained closed, cannot occur.