Patent GB-196686-A (GB)
Title: Improvements relating to electrical switch gear
IPC: H01H33/46
Filed: 1922-01-26
Abstract: 196,686. Davies, D. R., and Metropolitan-Vickers Electrical Co., Ltd. Jan. 26, 1922. Oil switches; szcitches, interlocking; s w i t c h - boards. - In switchgear of the kind comprising a plurality of units each having two or more enclosed switches, an interlocking system is provided comprising a plurality of sliding locking bars capable of being moved to predetermined positions whereby access may be had to thereleasing means only when predetermined switches are open. As applied to switchgear units 3, 4 (Fig. 1), the feeders 7 pass through isolating switches 6 and main oil switches 5, one terminal of which may be connected to the main bus bar 1 or the auxiliary bus-bar 2 by alternately operable selector switches 8, 9 which are interlocked with each other so that they cannot both be closed together. The isolating switches 6 have containers 10 and the selector switches 8, 9 of the units 3, 4 are provided with removable containers 11 - - 14. The selector switch tanks have lowering gear consisting of cables 15 and winding drums 16 - - 19 adapted to be rotated bv a handle 20 which has a non-circular end adapted to engage a similar recess 22 in the drums. Parallel locking bars are disposed across the switch gear units, one common locking bar 40 extending across all the units and a unit bar 41 across each unit. The common bar 40 has a projection 42 corresponding to each winch spindle and the unit bars 41 have similar projections 44. Holes 43 in the projections 42 and holes 45 in the projections 44 are arranged so that the openings 22 in the winch drums of the main and auxiliary switch tanks are never simultaneously exposed. The common locking bar 40 and unit bars 41 are provided with interlocking means whereby the holes 43, 45 can only be brought into line with the recess 22 pertaining to the tank of a main or auxiliary selector switch tank of any unit when the main or auxiliary selector switches of all the units and both selector switches of the particular unit open. This is obtained by locking projections on the bars 40, 41, which co-operate with locking fingers 38, 37 operatively connected with the main and auxiliary switches respectively. The common bar 40 has two downward projections 46 and the unit bar one downward projection 48 for each unit. To release a main switch tank, e.g. 12, Fig. 2, the common bar 40 and unit bar 41 for that unit are moved to their extreme left positions, movement of the bar 40 causing all the right hand projections 46 to block the fingers 38 and consequently prevent closure of all the main selector switches and the movement of the unit bar 41 causing the projection 48 to block the finger 37 of auxiliary selected switch 9 of the unit 3. The winch 17 can now be operated to lower the tank 12. In lowering a projection 52 on the tank 12 allows a pivoted bar 49 to fall into slots 49, 50 of the common and unit bars to prevent their movement until the tank is raised. Thus the container of any selector switch cannot be lowered until all switches which might render it alive are open. The switches 6, 8, 9 may be of the type described in Specifications 186,733, 187,027 and 187,565, the actuating mechanism of the type described in the latter Specification ensuring that if the main shaft 23 (Fig. 4) is turned in one or other direction, the isolating switch 6 and one or other of the selector switched 8, 9 are closed. The shaft 23 is operated through a chain 24 from a shaft 25 on which are keyed crank arms 28, 29 pertaining to the main and auxiliary seelctor switches. The crank arms 28, 29 are connected by links 30, 31 to rocking levers 32, 33 secured on shafts 34 which may be operated by a removable key 27. The other ends of the levers 32, 33 are connected by links 35, 36 to the locking projections 37, 38 pivoted at 39. The Specification also describes the application of the above interlocking system to three phase switch gear units, and states that a similar system may be applied to the sliding carriage and sectionalized bus. bar types of switchgear.