Patent GB-831586-A (GB)
Title: Improvements in or relating to electric switches
IPC: H01H3/30
Filed: 1958-01-21
Abstract: 831,586. Electrically released switches; hightension switches; actuation of switches; protective cut-out arrangements. WESTING- HOUSE ELECTRIC CORPORATION. Jan. 21, 1958 [Jan. 31, 1957], No. 1985/58. Class 38 (5). An earthing switch comprises a metal enclosure 28, Fig. 3, at earth potential, an elongated insulating casing 30 above the enclosure, a fixed contact 46 inside the casing and supported from the top thereof, a reciprocating contact member 54 extending from the enclosure into the casing and normally spaced from the fixed contact, energy storage means, e.g. a spring 156, Fig. 8, for closing the contacts and operating means for opening the contacts, the casing and part of the .enclosure being filled with gas having a dielectric strength of at least 1.4 times that of air. The gas may be sulphur hexafluoride, selenium hexafluoride, bromotrifluoromethane, perfluoropropane or dichlorodifluoromethane. Electrically-released switches.-The moving contact 54 is moved by an operating lever 81 secured to a shaft 82 which is latched in the contact open position by an underset toggle 95, 97, Fig. 6, engaging a latch lever 105. The toggle is biased by a spring 104 but is prevented from collapsing by a component of the spring forces acting on the shaft 82. When `a tripping electromagnet 108 is energized, a latch 102 releases the toggle lever 97 .which is turned anticlockwise by the-force applied by the lever 105. This prises the toggle lever 95 out of engagement with the latch lever 105 and enables the switch to close. Latching switches.-When the switch closes it is latched to prevent contact rebound by means of a. latch 158, Fig 10, which engages a shoulder 164 on a plate 143 secured to the shaft 82. To open the switch, an operating handle 149, Fig. 8, secured to a hollow shaft 144 is turned, so that a pin 166 on an arm 165 secured to the shaft 144 initially engages an extension 167 of the latch 158 and lifts this latch out of engagement with the shoulder 164. The pin 166 then engages a shoulder 168 on the plate 143 and turns the plate 143 to open the contacts and to stress the spring 156 which is connected to the plate 143 by a link 157. Retarding switches,-In addition to the closing spring 156, a spring 68, Fig. 3, is provided to accelerate the moving contact 54 which is provided with a piston 63. When the piston passes apertures in a tube 55, gas is compressed in the tube by the piston to cushion the final closing movement. Rubber sheets 91 also act as a buffer for the moving contact assembly. Protective cut-out arrangements.-In the arrangement shown in Fig. 2, the earthing switch is used in conjunction with a disconnect switch to protect a transformer. In the event of an internal fault in the transformer, differential relays open a low-voltage circuit-breaker and cause the earthing switch to close. This causes sufficient current to flow to operate protective relays which trip a remote high-voltage circuitbreaker. Pressure-operated relays 176, 177, Fig. 6, in the enclosure 28 perform various protective functions should there be a loss of gas pressure within the casing. Specifications 710,925 and 736,090 are referred to.