GB1469146A - Method of detecting a leak in a vacuum interrupter - Google Patents

Abstract

1469146 Vacuum switches GENERAL ELECTRIC CO 21 June 1974 [11 July 1973] 27759/74 Heading H1N The invention relates to methods of leak detection in a vacuum-type circuit breaker in which the circuit breaker includes a housing 10 filled with pressurized insulating gas, e.g. SF6, containing a plurality of series-connected vacuum interrupters 20 of conventional design operatively interconnected via a ladder-type linkage 42, 42 and overtravel devices 55 (Figs. 3 and 4, not shown), to an operating rod 45 which is disconnectably coupled to a closing mechanism 65 by a pin 67. The gas pressure tends to hold the interrupter contacts 26, 27 closed and also exerts an ejecting force on the operating rod 45 at the entry point to the housing where it is sealed by a bellows 47 and the breaker opening force is derived from a spring 50 bearing against a thrust plate 52 on to a shoulder 54 on the operating rod, which spring force can be rendered ineffective by operating jack screws 68 to move the thrust plate 52 clear of the shoulder 54. To test for a major leakage in any interrupter 20 the circuit breaker is opened, the closing mechanism disconnected by removing the pin 67 and the net force on the operating rod 45 is then measured and compared to a standard value with the interrupters intact and when the gas pressure (gauge 15) is at a given value, due allowance being made for the force exerted by the opening spring 50. For more accurate assessment the additional step of rendering the opening spring 50 ineffective can be taken before the net force is measured. For minor leaks an electrical test method of applying a voltage across the plurality of interrupters (circuit breaker open) results in a glow discharge within a leaky interrupter and by making the interrupters with translucent casings the discharge can be detected externally of the housing 10 through a lightsensitive device 75.