398,889. Switchgear structures. REYROLLE & CO., Ltd., A., Hebburn-on- Tyne, and ALLAN, A., Cragside, Ashleigh Grove, Tynemouth. March 34, 1932, No. 8768. [Class 38 (v).] Oil switches; fluid actuation.-In metal-clad switchgear comprising a tank or chamber containing a circuit-breaker or other electrical apparatus, a chamber containing a busbar or like conductor, and an insulated conductor so mounted that it can project into the apparatus tank and the busbar chamber to connect the busbar or like conductor to a terminal of the apparatus and can be moved longitudinally to break such connection, fluid-pressure operated means are provided for effecting the longitudinal movements of the insulated conductor. The insulated conductor is preferably mounted, as claimed in Specification 398,891, in such a manner that it can be withdrawn towards or into the apparatus tank, whereby the conductor can be removed with the apparatus tank from the switchgear. The invention may also be combined with the devices for sealing a body of insulating liquid between the busbar or other conductor and the metal walls of the chamber claimed in Specification 398,890. In the arrangement shown. in Figs. 1 and 2, a circuit-breaker controls the connection from a busbar 62 to a feeder or other circuit. The circuit-breaker tank 50 rests on the ground, and oil-filled chambers 60, 70 are mounted above it on pillars or a framework (not shown). The chamber 70 is associated with the feeder circuit and contains a contact 71 to which the feeder cable 75 may be connected through a hollow insulator 73. The circuit-breaker comprises two main contacts 51, 52 and a movable bridging contact 53 arranged to give six breaks in series. The contacts 51, 52 are connected to or disconnected from the busbar contact 61 and the contact 71, respectively by movable conductors 100, each of which comprises a central tube 101 surrounded by condenser type insulation and provided with contact members' 106, 107 at each end. The lower contact 106 comprises spring-pressed plungers 105 engaging a metal tube 85 secured to one of the main contacts 51, 52, while the upper contact 107 is in the form of spring-pressed butt contacts adapted to engage the busbar or feeder contacts 61 or 71. The tube 85 is carried by a condenser type insulator 80 which projects through the cover of the tank 50 and is connected at its upper end to a metal casing 90, containing a cylindrical trunk 91 surrounded by an annular chamber 92 which may house current transformers. The metal trunk 91 is connected to a valve chest 140 beneath the busbar or feeder chamber 60, 70 by a flexible metal bellows 93 protected by a metal shield 94. The valve chest contains a sluice valve operated by a hand-wheel 143 to seal the orifice at the bottom of the chamber 60 or 70 when the movable conductor has been withdrawn. The movements of the conductor are effected hydraulically by varying the pressure above and below piston rings 108 by means of a pump 110 driven by an electric motor 111. A latch member 120, adapted to engage grooves 124, 125 in the outer sheath of the movable conductor, is provided to hold the latter in the on and off positions. The latch member is operated through a rod 135 which also controls the operation of auxiliary switches 137 for indicating or interlocking purposes, the arrangement being such that the pump motor cannot be energized until the latch has been released, or when the sluice valve is closed. In a modification. Fig. 7, for use with a duplicate bus bar installation, three oil-filled chambers are mounted above the circuitbreaker oil tank 180, two of them, 170, 175, containing contacts 171, 176 connected to the two bus bars, while the third (not shown) contains a contact connected to the feeder circuit. One of the main circuit-breaker contacts 181 is connected to contact rings 193 in hollow insulators 190, the contact rings being adapted to be selectively connected to the contacts 171 or 176 by movable insulated conductors, each comprising a metal tube 210 with upper butt contacts 211 and lower spring contacts 212. The central tube 210 is surrounded bv condenser insulation, the upper part of which is enclosed within a metal sheath 215 which slides within the trunk 201 and is therefore always earthed. An intermediate metal layer of the condenser insulation is provided with spring contacts 216, which, in the operative position of the movable conductor, are earthed through the metal tube 197. When the movable conductor is in the isolating position, shown on the left side of the Figure, the intermediate contacts 216'may be alive, owing to the connection of the circuitbreaker contact 181 to the other bus bar, but the end contact 212 is, in t h i s position, earthed by connection to a metal tube 195 on the bottom of the insulator 190. Instead of condenser type insulation, an oil-filled type of insulati n g bushing, comprising concentric insulating tubes of graded lengths, may be used for the movable conductor. In another arrangement, Fig. 10, a single withdrawable conductor 290 is used for selectively connecting one of the main circuit-breaker contacts to either of two bus bars respectively mounted in chambers 250, 251. The movable conductor is carried in an insulator 283 mounted in a metal casing 280 which can be rocked about a hollow shaft 272, a contact 285 at the bottom of the insulator engaging a curved plate 261 connected to one of the main circuit-breaker contacts. In an arrangement for a three-phase installation, Figs. 11 12 (not shown) three single-phase circuit-breakers are mounted one behind the other on a wheeled truck, and potential transformers mounted in separate wheeled tanks are provided for each phase. The invention may also be applied to switchgear, wherein horizontal isolating movements are used, and to arrangements in which the bus bar or other chambers are mounted beneath the circuitbreaker tank. In the arrangement shown in Fig. 13 the sealing device is dispensed with, and the movable conductor 460 carries spring contacts 462 at each end, the contacts at the lower end being in permanent engagement with a metal tube 452 carried by a metal cap 451 secured to the circuit-breaker contact. In its raised position, the movable conductor enters an insulator 472 and its upper contact engages a metal cap 474 connected to the bus bar 475. The movements of the conductor are controlled by a pump through ducts 458, and the conductor is surrounded by a metal sheath 463 with grooves 465, 466 co-operating with a latching device 467. In another arrangement, Fig. 14 (not shown), the movable conductor is withdrawn into the fixed portion of the switchgear for isolating purposes. In a further modification, Fig. 15, for a duplicate bus bar installation, the bus bar chambers 510, 520 are mounted one above the other over the circuitbreaker tank, and the connections from the respective bus bars to the terminal of the circuitbreaker are controlled bv two coaxial insulated conductors 540, 550, one of which is adapted to engage a pin contact 534 and the other a tubular contact 535, both contacts 534, 535 being connected to the circuit-breaker terminals. The movements of the conductors are controlled by a pump through ducts 528, 529, and the conductors are withdrawn,. for isolating purposes, into the fixed part of the switchgear, which may then be sealed by a sluice valve 526. In modifications of this arrangement, Figs. 16 and 17 (not shown), a single movable insulated conductor is employed in combination with one or more sliding insulators to effect bus bar selection, the insulated conductor being withdrawable downwards towards the circuitbreaker tank for isolating purposes.