Patent GB-266965-A (GB)
Title: Improvements relating to electric switches
IPC: H01H33/02
Filed: 1926-06-18
Abstract: 266,965. British Thomson-Houston Co., Ltd., (General Electric Co.). June 18, 1926. High-potential switches; are-rupturing devices. -A method of interrupting a high-potential circuit consists in opening the circuit to draw a relatively long arc initially through air, free to expand and remain of uniform pressure, and finally continuing the arc into an insulating liquid. In Fig. 2, the fired contact 1 is carried on a support 22 on an insulator string 20 and is of a form to frictionally engage the contact-rod 2 which is carried on a support 21 on the lower end of the string 20. The rod 2 is secured to a piston 5 working in a cylinder 6 having a partition 26 carrying a contact 25 by which the rod is connected to the cylinder. The cylinder communicates by slots 28 and pipes 30 with a reservoir 31, the whole being filled to the level shown with a liquid of high-dielectric strength. An auxiliary switch 9, 10 in a vessel 12 is controlled by a solenoid 39 the contacts of which normally short-circuit a solenoid 14 of which the core is secured to the rod 9. The vessel 12 communicates both with that 6 and a reservoir 35 and is filled with the same liquid as the vessel 6. In operation, a predetermined overload in the solenoid 39 will remove the short-circuit from the solenoid 14 and open the switch 9, whereupon the arc forms a quantity of gas which passes into the cylinder 6 and depresses the piston 5 to open the main switch 1, 2. The arc of the main break is thus drawn first through air and then through liquid, the piston during its stroke forcing the liquid through the slots 28 into the reservoir 31 until it reaches the lower limit, when the slots are entirely closed. The switch 9, 10 recloses by gravity, but for the reclosing of the switch 1, 2 a rod 44 is provided to engage the piston 5, the latter having a bayonet slot 49 for engaging a pin 50 for manual opening of the switch by the rod 44. The parts may be duplicated or triplicated for polyphase switches, individual mechanism for each phase of a polyphase switch being shown in Fig. 3. Fluid actuation.-In this form, the contact rod 102 carries two pistons 114, 115 in cylinders 116, 117 between which is a casing 121 for holding a cushioning fluid such as oil. Bleed holes 118, 119, 122 are provided in the cylinders and casing. The cylinders communicate with a reservoir 125 for compressed fluid by means of valves 129, 130, the latter being manually operated by a rod 131. The valve 129 is connected to a lever 135 which is connected to the core 139 of a solenoid 140. The lever 135 also engages the rod of a piston 152 so as to be operated by the latter when compressed air is admitted to it. The reservoir 125 is fed from a pipe 126 and communicates through a valve 147 with a header 149 from which pipes 150 lead to the cylinder 151 of each switch. When an overload occurs in any phase, the solenoid 140 opens the valve 129 and admits fluid above the piston 114 to open the switch 101, 102, the arc as before being drawn first through air and then through liquid. At the same time the core 139 depresses the rod 160 to open the valve 147 and open the switches in the other phases. A handle 163 is provided for manually opening all three switches and a dashpot 158 is provided to prevent reclosure of the valve 147 before enough air has escaped to effect the opening. The switches are reclosed by means of the handles 133 either individually or by a common operating mechanism. A pipe 164 may lead to the disconnecting switches 142, 144 to operate them pneumatically.