Patent GB-392247-A (GB)
Title: Improvements in or relating to thermionic valve circuits for use in systems such as electric signalling or control systems
IPC: H03F1/54
Filed: 1931-12-03
Abstract: 392,247. Protective cut-out arrangements. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, WILLIS, F. B. and WESTELL, E. P. L., c/o General Electric Co., Stoke, Coventry. Dec. 3, 1931, No. 33508. [Class 38 (v).] When a valve becomes defective, a signal or control, foreign to normal operating conditions, is effected by means influenced by the emission of the valve. The invention is applied to a control system, such as that described in Specification 378,006, which relates to a pro. tective arrangement comprising a circuitbreaker at one end of a section of a power line tending'to trip to isolate the end of the section when power flows into the section to a fault. The control system prevents the tripping of the circuit-breaker, when the fault is in another section, by a transmitter at the remote end of the section operating a receiver at the other end to prevent the circuit-breaker tripping, when power also flows out at the remote end to the fault. Transmitter. When power passes out of the end of a section to a fault, overload relays connect terminals 69 together to operate relays 7, 47. The relay 7 closes contacts 10, 12 to connect the output of an amplifying valve 6 to a tuned circuit 4 through a coupling 8, and opens contacts 10, 11 to remove the shortcircuit from a condenser 46 which tunes the coupling circuit to the frequency of an oscillating valve 5. The high-frequency is applied through the circuit 4, a conductor 26 and a condenser bushing to the phase conductor of the power line. The local receiver 2 is disconnected from the circuit 4 by the opening of contacts 49 by the relay 47. Receiver. When a signal is received from the transmitter at the remote end, the. highfrequency current from the circuit 4 is applied to the grid of a detecting valve 15 through transformers 16, 64. The anode current flowing through a restraining coil 18 of a balanced relay 14 is thus reduced and causes the relay to close contacts 17. This connects terminals 71 together to operate apparatus to prevent the tripping of the circuit breaker which isolates the section. Safety devices. To ensure reliability, a warning is given of the failure of any of the valves 15, 5, 6 or the relay 14. For this purpose the supply currents to the operating coil 19 of the relay 14 and to the anodes of the valves pass through coils 39 of relays 27 .. 30, and these currents are normally sufficient to operate the relays. If any one of the currents falls below a predetermined value, the associated relay releases to close its contacts 40, 41. The contacts 40 complete a circuit through an associated alarm lamp 42, and the contacts 41 'complete a circuit from a supply across terminals 74 through operating coils 36 of a relay 35, which closes its contacts 37, 38. The contacts connect terminals 73, across which an, alarm bell is connected, to the supply terminals, 74. A periodic examination of the current flowing to the relay 14 and the anodes of the valves is made by the milliameters 31 .. 34 by opening short-circuiting switches 43. To test the output of the transmitter on a milliameter 24, a short-circuiting switch 25 is opened, and a button 75 pressed.