GB400716A - Improvements in or relating to withdrawable electric switchgear - Google Patents

Abstract

400,716. Switchgear structures. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and GARRARD, C. C., c/o General Electric Co., Witton, Birmingham. June 17, 1932, No. 17182. [Class 38 (v).] In switchgear of the kind in which a withdrawable circuit-breaker is adapted to be coupled to bus-bars or cables through main isolating contacts 5, 6, separating in air, auxiliary isolating contacts 2, 4 are arranged in parallel with the main isolating contacts and are adapted to separate in an insulating liquid after the main contacts have separated to a distance greater than sparking distance. Sparking at the main isolating contacts due, for example, to the charging current of the insulating bushings, is thereby prevented. In the arrangement shown, the main contacts 5 are mounted on a conducting member 1 secured to a sleeve 7, connected to one of the circuit-breaker contacts. The auxiliary contact 2 is secured to a metallic plunger 13 slidably mounted in the sleeve 7, and is pressed towards the contact 4 by a spring 10. A glass tube 17, surrounding the contacts 2, 4 is filled with oil to a level 21. On withdrawing the circuit-breaker, the plunger 13 moves up the sleeve 7 and maintains the contacts 2, 4 in engagement until the contacts 5, 6 have separated to a sufficient distance, further movement of the plunger is then prevented by its engagement with an abutment 25, and the auxiliary contacts 2, 4 finally separate under oil. A spring 23 maintains a head 24 on the contact 4 in engagement with the member 3 carrying the contacts 6 until after the contacts 2, 4 have separated. In a modified construction, the contact 4 slides within the contact 2, which is in the form of a socket, and does not leave the contact 2, on withdrawing the circuit-breaker, until after the main contacts have been separated sufficiently to prevent sparking.