Patent GB-476742-A (GB)
Title: Improvements in or relating to liquid-insulated electric circuit-breakers
IPC: H02B1/00
Filed: 1936-06-13
Abstract: 476,742. Switchgear structures ; oil - blast switches. REYROLLE & CO., Ltd., A., and ALLAN, A. June 13, 1936, No. 16549. [Class 38 (v)] A liquid-insulated breaker for use in switchgear has insulated lead-in conductors carried by the tank at or near the bottom thereof, and arranged so that engagement between their outer ends and contacts on the fixed part of the gear can be broken for isolation by movement of the breaker tank, whilst connections between their inner ends and a fixed and moving contact structure carried by the tank-cover can be broken, without disturbing the lead-in conductors, by withdrawing the cover, for example, for inspecting the contact structure carried thereon. The circuit-breaker may have arc-control devices of the character described in Specifications 435,250 and 435,308. General lay-out. Fig. 1 shows a single panel of a row, each panel of which controls a threephase T-connected circuit. Each panel comprises a rectangular oil-filled cubicle A containing a removable frame B with a top plate B' supporting a breaker in a cylindrical oil-tank L and constituting the cover of the cubicle. The latter houses an instrument and relay panel A<3> and is formed also with a bus-bar chamber D with bottom inspection cover D<1>, the chamber and bus-bars E running the length of the row of panels. Each panel has three conductors El each connected to the associated bus-bar and passing upwardly through bushings E<2> to plug contacts E<3> within orifice insulators E<4>. The part B<2> of frame B carries three orifice insulators F containing plug contacts F<2> which are provided with terminals F<3>. The contacts E<S>, F<2> are respectively arranged in equilateral triangle fashion. Conducting straps G extend from terminals F<3> through current transformers C and over conductors G<1> to earth terminals H provided with contacts H<4> for engagement by an earthing switch J. A potential transformer K is mounted in a separate tank K<1> and connectible with either the conductors G or the terminals H over withdrawable H.T. fuses K<2> and conductors K<3>, the fuses being attached to a cover K<5> through the orifice of which a testing bushing for the cable may be inserted when the fuse is withdrawn. The cover K<5> may also carry links for breaking the L.T. transformer-connections when it is withdrawn. Oil switch. The contacts E<3>, F2 co-operate with isolating socket contacts M<2>, N<2> on conductors M, N passing through, preferably laminated, insulators M<1>, N<1> respectively. Each conductor N terminates in a contact engageable with a socket O<4>, whereas M carries a socket M<3> with which the movable contact P slidably engages, the three latter being mounted on radial insulating arms P<1> on a metal hub P<2> which is slidable on a central pillar P<3> extending down from the tank-cover L<1>. The fixed contacts O<1> are carried in arc-control devices preferably of the character described in Specification 460,219. Each device comprises side plates R, R<1>, which are extended upwards for securing to the cover L<1>, and main blocks R<2>, R<3>, the latter being provided with vents R<4> and the whole being secured by through bolts R<6>. Fibre plates may, however, be provided between each side plate and the main blocks. The fixed contact O<1> comprises a suitably-shaped ring cut into sectors and mounted in a housing O formed on a metal member O<3> which carries socket O<4>. Member O<3> is removably secured to plates R<1>, R<2> by means of pins O<5> passing through them and through lugs O<6> on the members and secured by split pins 0<7>. Contact structures O<2>, O<4>, M<2>, N<2> are preferably standardized for interchangeability reasons. The tank L normally rests on stops B<5> on plate B<2>, in which position its upper end projects above plate B<1>. Fig. 3 shows the isolated position whereas Fig. 1 shows the service position. A rubber ring L<5> is located between lugs L<6>, L<7> on the tank inside an extension B<6> of plate B<1>, this ring serving to maintain a weatherproof joint by rolling on itself during movement of the tank. A similar ring L4, as described in Specification 460,970, is located between an inner skirt L<2> on the cover and the inside of the tank, to which the cover is normally secured by bolts (not shown). Insulating barriers project inwardly from the tank-lining to divide the tank into sectors, each containing the apparatus of one phase, and the arc-products are arranged to discharge towards the junction of the barrier and lining. Raising and lowering mechanism. This is shown in Fig. 4 and provides for raising the breaker unit as a whole to isolating position and then, when the securing bolts are removed, raising the cover further for inspection of the contacts. A central tube S is welded to a tubular member S<1> bolted to the base of the tank and provided with a mushroom extension S<3>. A tube T within the tube S is screwed to a cup-shaped support W which is bolted to the frame-plate B<2>. Secured to T is a nut T<1> which is threaded to engage a rod U having a thrust bearing U<2> so that U can be rotated, but cannot move longitudinally relatively to the tank-cover L<1>. A bevel wheel U<10> is keyed to U and co-operates with a bevel wheel U<9> on a shaft U<8> on the cover, U<8> being rotated from a handle-driven shaft U<3>, Fig. 1, through gearing U<5>, U' and a squared shaft U<6> which allows longitudinal movement relative to the gear U<5> as the cover rises. When the unit is in isolating position, a pair of spring-pawls V pivoted at V<2> to W move inwards under the support S<3> in order to take the weight of the tank and permit removal of the bolts so that the cover can be further raised. To release the pawls and allow return of the unit, each pawl has an arm V<3> with toothed rack V<4> engaged by a pinion X having an extension X<1> with square bore X<3> engaged by a rod X4. The latter passes up through rod U and terminates in a rotatable knob X<6>, which is preferably small enough to be only rotatable when the weight of the tank has been taken by the bolts securing it to the cover. Alternatively, the pawls may be locked by projections on the support S<3>. The rod X<4> is not long enough to engage X3 when the cover is raised above the tank. Instead of the screw-threaded arrangement, a central cylindrical tube passing through and fixed to the tank may contain two pistons, the lower of which is fixed to the frame and the upper to the cover, whereby when oil is pumped into the cylinder between the pistons, first the unit is raised, and then the cover alone. Interlocking mechanism. The cover securing bolts may be locked against movement by means (not shown) associated with the means for supporting the tank in isolating position. The earthing switch J may also be locked against movement while the tank is in service position, by resting on a lug on a rod linked to the spindle of J. The latter may also be padlocked. Contacts M<2>, N<2> may be arranged to engage earthing contacts in the isolated position. When the unit and frame B are to be lifted from the cubicle, lifting tackle is employed. The gear as a whole can be accommodated in a cellar or. vault below a pavement or road or in other positions where a considerable depth of water may accumulate.