GB924092A - Improvements in or relating to electric switchgear - Google Patents

Abstract

924,092. Switchgear structures; oil-break switches; actuation of switches. GENERAL ELECTRIC CO. Ltd. Sept. 17, 1959 [Sept. 17, 1958], No. 29795/58. Class 38 (5). In switchgear having means for earthing a terminal of a switch by movement of a contact of the switch into engagement with an earthing terminal, interlocking means are provided to permit the use of the earthing terminal as a test terminal after the removal of the earth therefrom, the interlocking means being arranged to prevent movement of the contact whilst the earth connection is removed. Fig. 1 shows one phase of a three-phase switchgear structure for a ring main circuit and having two oil-break switches per phase, the oilbreak switches having moving contacts 17, 17a, each movable from the " on " position shown into an intermediate " off " position and thence into an earth position in which it engages an earthing contact 25 or 25a. The contacts 25 or 25a of the corresponding switches in each phase are earthed by a common earthing blade 43 which is pivoted at 50, Fig. 2, and connected to a push-rod 51. To open the corresponding switches in the three phases an operating handle (not shown) is turned to move a cam member 55, Fig. 3, which stresses a spring 67 and then raises a bar 56 from a detent 57 in a fixed member 58. A member 54 secured to the switch-operating shaft 22 is then turned until the bar 56 engages a detent 60, the contacts 17 being opened. Further operation of the handle causes the movement of the shaft 22 and the member 54 into the position where the contacts 17 engage the earthing contacts 25 and the bar 56 engages a detent 66. In this position, a depression 68 in the cam-like member 54 is over the end of the rod 51 so that the earthing blade 43 may be swung out of engagement with the terminals of the contacts 25, the end of the rod entering the depression 68 and preventing any further movement of the shaft 22 and contacts 17. In Fig. 1, the ring main bus-bar 21 is connected to a tie-off circuit by the isolator 29, fuse assembly 16 and oil-break circuit-breaker 17b described in Specification 29794/58.