Patent GB-425107-A (GB)
Title: Improvements in or relating to metal-clad electric switchgear
IPC: H02B13/035
Filed: 1933-08-04
Abstract: 425,107. Switchgear structures. REYROLLE & CO., Ltd., A., Hebburn-on-Tyne, ALLAN, A., Cragside, Ashleigh Grove, Tynemouth, and SMALL, J., 9, Broadway, Sheriff Hill, Gateshead-on-Tyne. Aug. 4, 1933, Nos. 21908 and 27034. [Class 38 (v)] Metal - clad switchgear comprises busbar sections normally connected together to form a closed ring, in combination with a circuit - breaker panel associated with each junction between the sections and comprising a liquid-insulated breaker controlling a teeconnection from the busbar to the external circuit. A liquid-filled chamber associated with the breaker contains a switch or switches for controlling the connections between the two busbar sections and the breaker, whereby all three or any two thereof can be connected together. As applied to a 66 kV. three-phase system, in which four feeders H and two transformers H<1> are adapted to be connected to the busbars, single-phase oil circuit-breakers A are arranged one behind the other, Fig. 3 in two rows, Fig. 2, each row consisting of three panels which correspond to two feeders and a transformer, Fig. 4. The fixed contacts of each breaker A, Fig. 5, extend into compartments in an upper oil-chamber Band carry contacts E, D respectively connected to the feeder H or transformer connection, and carrying an isolating arm D<1> which can be rotated to engage either contact F, F<1> on adjacent busbar sections C or an earthing contact D<2>. The contact F pivotally carries an arm F<2> which can be moved into or out of engagement with F<1> for sectionalizing the busbars, and is made arcuate so that in its engaging position, the contact D<1> can be moved to and fro between F, F<1> without breaking contact with the busbars. Switches G on a shaft or shafts G<1> are provided for engaging the contacts F, F<1> to earth the busbar sections provided they are disconnected at both ends, and an earthing switch H<3> for the contact E is also provided. The busbars C extend through chambers B from end to end of the rows, Fig. 2, and are interconnected at the ends at C<1>, Fig. 3, to form a closed ring. Each busbar C, Fig. 7, comprises an oil-conduit C containing a conductor C<2> surrounded by impregnated paper insulation C<3>, to which at one end of chamber B a metal flange C<4> is attached in an oil-tight manner. At the other end the insulation C<3> can slide freely through a gland C<5> to accommodate temperature changes, or is connected to the chamber wall by a flexible diaphragm, and the conduit is formed, as with a corrugated part C<6>, for the same purpose. To inspect a panel, the three breakers A therein are opened and the switches D<1> moved to their earthing contacts D<2>. The switches D<1> of the adjacent panels are then moved to engage the busbar sections remote from the panel to be inspected, (if not already there), and the switches F<2> of those panels opened. Switches G and H3 of the panel to be inspected are then moved to earthing position, so that the panel is isolated and earthed without affecting the supply to the other panels. Any breaker can be earthed on both sides by means of D<1>, H3 while leaving the sections through the panel connected by F<2> and alive. The usual interlocks are provided but are not shown, and in addition an interlock prevents application of the lowering-and-removing truck to the breaker unless H<3> is in the earthed position. The truck, Figs. 2, 3, comprises standards J on a wheeled base J<1> and threaded shafts J<2> carrying nuts forming parts of carriages J<3>. The shafts J<2> are rotatable by an electric motor J4 or handle J<5> to raise J<3> until recesses therein engage lugs on the tank A, the bolts connecting A to its top-plate B<4> are then undone and the tank is lowered. Where the breaker has its own top-plate, it may be lowered bodily, plug-and-socket isolating contacts being provided for connecting with contacts D, E. The master interlocking handle and actuating handles for the section-aligning and other switches of the panels are shown at K, K<1>, respectively. Modifications of the sectionalizing and isolating arrangement comprise the following. Two switch arms are mounted for rotation about and connected to, the busbars and arranged so that each can be moved into or out of engagement with the other for sectionalizing and into or out of engagement with the breaker contact for isolating, Figs. 8, 9, (not shown). A single rotary contact of sector shape can be moved to interconnect any two or all three of the contacts D, F, F<1>, provision being also made for insertion to the sector-contact of a testing terminal, subject to the switches being in appropriate positions, Figs. 10-14, (not shown). Provision may also be made in the cable compartment for a connection to a potential transformer which is located on the ground and isolated by a longitudinally-movable, insulated conductor, withdrawable from the compartment through an orifice in the base thereof, which orifice is closed by a sliding sluice valve or other means when the conductor is withdrawn. The sector contact may also be replaced by two independently-movable, sector contacts, both engageable with the contacts D, F, F<1>, Figs. 15, 16, (not shown). For lower voltages, the set of single-phase breakers may be replaced by a single three-phase breaker.