Patent GB-542931-A (GB)
Title: Improvements in systems for the remote supervision of circuit breakers or the like in electric supply networks
IPC: H02J13/00
Filed: 1940-07-31
Abstract: 542,931. Electric signalling systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., BURNS. G. A., and RICHARDSON, J. V. July 31, 1940, No. 12369. [Class 40 (i)] [Also in Group XXXIX] In a system in which the condition of circuitbreakers &c. at a sub-station is signalled to a central station by means of impulses of voicefrequency alternating current, the supervisory cycle is initiated by a signal from the central station and is repeated several times, first controlling a lamp indicator and subsequently giving audible indications to an attendant. Each sub-station, Figs. 1, 3, is connected to the central station, Figs. 2, 4, by a line 19, 20 which serves both for supervision and for telephony. Relay S is connected over front and back contacts OCB controlled by the circuit-breakers so that it falls back momentarily when any change occurs and operates relay SAR, which completes the signalling loop through relays M, MM. The calling lamp SCL lights, whereupon the attendant actuates the corresponding speak key KS and hears in his instrument over leads 23, 24 a tone generated by buzzer relay BZ which is connected up by M, P. To initiate supervisory signalling he actuates key KRA to extend the line to receiving apparatus comprising valves V 1 , V 2  and throws key KR to send continuous ringing current. Relay ST responds at the sub-station and by means of STA, STB connects up PS. Relay STA is shunted by a condenser QB of high capacity to prevent its operation in response to interrupted ringing current, which is used for telephone calling and is applied when key KC is thrown in addition to KR. If no change has taken place at the sub-station, relay M is connected up by STB. When ringing current ceases, the switch SW rotates under the control of stepping relays A, B and relay P operates one or more times over wiper SW 2  to send a number of tone-impulses identifying the sub-station. These are repeated by relay AA to step the switch R which connects up a relay such as 1SA, 2SA to light an appropriate lamp and then goes to position 26. Three positions of the switch SW are allotted to each circuit-breaker from position 26 onwards, and one or two impulses are sent according to the position of contacts OCB. Wipers SW 3 ,  6,  are brought into action after SW 5  by relay W under the control of an auxiliary switch D which steps after each revolution of SW. The switch R follows the movement of SW and has two positions for each circuit-breaker, so that one impulse goes to the releasing side of a relay such as IC and the following one if sent to the operating side. These relays are of the locking type and control green and red lamps GL, RL corresponding to the circuit-breakers. Wipers R 4 ,  7  are brought into action after R 6  by relay WS. When the cycle is complete, relay SSR energizes and connects the output of the valves V 1 , V 2  to a loudspeaker LS so that during subsequent cycles the impulses are heard as a series of pips of tone. The switch D is wired to provide for as many repetitions as may be desired. The indicating lamps are arranged in columns on a display panel, Fig. 5 (not shown), and a drum indicator may be turned to show a list of circuitbreakers &c. at the appropriate sub-station opposite the green and red lamps. The display remains set up until re-set key KAR is actuated. Relays IV, TC are provided for signalling alarm conditions at the sub-station, positions of the switch SW being allotted for this purpose. Supervisory signalling is prevented while telephony is in progress by the shunting effect of the sub-station instrument.