Patent GB-448789-A (GB)
Title: Improvements in or relating to electric circuit-breakers
IPC: H01H33/70
Filed: 1934-12-13
Abstract: 448,789. Liquid-blast switches. ELECTRICAL IMPROVEMENTS, Ltd., Carliol House, Newcastle-on-Tyne, GREGORY, R. W., Ridgeway-on-Yarridge, Hexham, Northumberland, and BEARD, J. R., Amberhurst, Silver Lane, Purley, Surrey. Dec. 13, 1934, No. 35847. [Class 38 (v)] Extinction of the arc formed on opening the contacts of a circuit-breaker is assisted by utilizing the surge pressure (" water - hammer ") set up by the sudden closing of a valve in a passage through which extinguishing liquid, or oil, is flowing, to project the liquid at high velocity through an orifice. A pressure of over 300 lbs./in. can be realized by the sudden stoppage of liquid flowing at six ft. /sec. In Fig. 1, the movable contact B is operable by means of a rod B<1> passing through the cover A<1> of an insulating oil-tank A, into engagement with a fixed contact C surrounding an orifiee D<1> of a metal pipe D, which orifice is normally closed by the contact B. The inlet D communicates through a port D<2>, normally opened by a valve E<1>, with an outlet pipe E. Continuous circulation of oil occurs from D to E and thence to a sump from which a pump raises the oil to a reservoir, whence it flows into the pipe D again. The valve E<1> is arranged to he closed by, and as nearly instantaneously as possible with, the tripping action of the breaker, so producing the surge pressure in D which is released through D<1> into the arc-path of the separating contacts. The length of piping from the reservoir to the inlet D should be sufficient to ensure maintenance of the pressure during the arcing period. The fixed contact C may be insulated from the pipes D, E, which may themselves be insulating, and may be connected to the circuit by a lead passing through an insulating bushing in the cover. Contact B may be mounted on a pivoted arm. Two or more series breaks may be provided, each having an orifice in the inlet pipe. In Fig. 2, an insulating cylinder G has metal end caps H, J, the former of which is connected to two fixed contacts K by means of the metal inlet pipe M, whereas the latter serves to admit the insulating operating rod L<4> of the movable contacts L which are mounted on a spider L<2> guided on a pair of insulating rods, as L3. When K, L are in contact, the latter close passages N<2> leading into the tank from a chamber N<1> in an insulating structure N. An extension L<5> of rod L<4> normally holds a valve M<1> away from an orifice N<3> into which oil normally flows from chamber N<1>, but when L<4> is lowered to open circuit, a spring M<2> urges the valve M<1> into the mouth of the orifice N3 to produce the surge pressure, which is released by the opening of passages N<2> when the contacts separate. The mouths of the passages N<2> are directed upwards to reduce the strain on cylinder G, and reinforcing members N<4> afford further protection. The arrangement in this Figure may be adapted to breakers of conventional type, with the main oil pipe leading into the casing, or with a tee connection leading into the casing from an external pipe, the latter providing a suitable means of supplying a bank of breakers from one pipe having a valve for each breaker just beyond the tee connection. To avoid the waste involved in driving a pump continuously, the flow may be initiated by the tripping action, with slight loss of speed, however. In this case the liquid may be set in motion by a pump-plunger operated by a solenoid or by an electromagneticallyreleased spring or pneumatic or other force, or a valve releasing a static head, or a combination of such elements.