GB818521A - Improvements in and relating to gas-blast electric circuit breakers - Google Patents

Abstract

818,521. Gas-blast switches. ENGLISH ELECTRIC CO. Ltd. Dec. 2, 1955 (Dec. 3, 1954], No. 35070/54. Class 38 (5). A gas-blast switch 3 has means to maintain the blast valve 6 open once it has opened during an opening operation, the means becoming inoperative only when an isolating contact element of the switch has completed at least a major part of its movement to an open position. When the switch is to be opened, the coil 10a of a pilot valve 10 is energized moving the valve to the left and admitting air under pressure to a valve 9a. This causes valves 9a and 9b to move down to open valve 9b and admit pressure to the left-hand side of a piston 8a. The piston 8a moves a two-way valve 8 to the right to cut off the air supply to the space below a piston 6a and to exhaust this space to the atmosphere. The pressure in the chamber la moves the piston 6a down to open the blast-valve 6. Pressure air entering the column 1 can now act through a non-return valve 12, a cut-off valve 14, a pipe 11 and a non-return valve 13 on the valve 9a to maintain the valves 9a, 9b in their lower position, so maintaining the valve 6 open until an isolating contact arm 15 has been moved sufficiently to close the cut-off valve 14. At this instant the coil 10a would normally be de-energized e.g. by the opening of auxiliary contacts associated with the arm 15. In a multiphase arrangement the pipes between the valves 12, 14 associated with the respective phases may be interconnected by a pipe 16 to ensure that the switch of one phase cannot remain closed while the others open. In Fig. 2 (not shown), the pipe 11 may be connected so that the maintaining pressure acts directly on to the piston 8a. In a further arrangement similar to that of Fig. 1, the maintaining pressure is derived from the pipe between the valve 9b and cylinder 8b, Fig. 3 (not shown). The isolating contact may be an arm 15 as shown, but it could be one of the main interrupting contacts which, by continued movement, establishes an isolating gap.