GB960402A - Improvements in or relating to electric circuit-breakers - Google Patents

Abstract

960,402. Gas-blast switches. ENGLISH ELECTRIC CO. Ltd. June 1, 1960 [June 2, 1959], No. 18794/59. Heading H2B. A gas-blast circuit-breaker comprises a centre section 16, a pair of oppositely-projecting hollow insulators 20 mounted one on each side of the centre section and each forming an enclosure for a pair of co-operating contacts, a common source of compressed gas and a common exhaust valve 18 to control the flow of gas from the source through the enclosures, through a nozzle contact of each pair of contacts and the valve to atmosphere. To open the circuit breaker, the control rod 106, Fig. 4, is moved upwardly and the rod, through a bell-crank lever 105, displaces a valve control lever 101 to the left to open a pilot valve 102 which admits compressed air to the lower face of a piston 74, Fig. 2, to open the exhaust valve 18. The resulting reduction in pressure within the hollow moving contacts 41 permits the pressure in the contact enclosures to cause the initial movement of each moving contact 41 which separates from resilient fixed contact fingers 27, the " fixed " arcing contact 29 moving with the moving contact 41 under the bias of a spring 33. This initial movement causes each contact actuating piston 49 to uncover a port 50, Fig. 5, to admit compressed air to a cylinder 48 and cause the piston to withdraw the associated moving contact 41 from the arcing contact 29. As each moving contact 41 is moved from its closed to its open position, an associated spring toggle 91, 92 moves over centre to maintain the contacts open. Providing both moving contacts 41 open, the toggles, through links 96 . . . 100, turn the valve control lever 101 to release the pilot valve 102 which recloses and so permits the exhaust valve 18 to reclose. The lever 101 also operates a valve 103 which exhausts cylinders 31 so that the compressed air in the circuit breaker moves pistons 32 to retract the arcing contacts 29 to provide contact gaps adequate for isolation purposes. To close the circuit-breaker, the rod 106 is moved downwardly causing the bell-crank lever 105 to move the lever 101 to the right to release the valve 103. This allows each arcing contact 29 to move towards the associated moving contact 49 under the bias of its spring 33. The right hand end of the lever 101 operates a valve 104 to admit compressed air to the operating cylinder 124 of a change-over valve 122 which opens each port 50 to atmosphere and admits compressed air to another port 51 of each cylinder 48. The pistons 49 now close the contacts, the toggles 91, 92 passing back through their deadcentre positions to bias the contacts closed and to cause the lever 101 to pivot so that the valve 104 is released and recloses, shutting off the supply of compressed air to the cylinder 124 so that the change-over valve 122 restores. Specifications 960,403, 960,404, 960,405 and 960,406 are referred to. Reference has been directed by the Comptroller to Specification 919,843.