Patent GB-222105-A (GB)
Title: Improvements relating to electrical control systems
IPC: H02J13/00
Filed: 1924-09-03
Abstract: 222,105. Metropolitan-Vickers Elec trical Co., Ltd., (Assignees of Gardner, J. E.). Sept. 20, 1923, [Convention date]. Selective distant-control systems; tell-tale apparatus.-A system for supervising and controlling from a remote point the operation and condition of apparatus units at substations of an electric-supply system is specially arranged for dealing with overload conditions, for example, if a circuit-breaker which has been closed under automatic or distant manual control is immediately tripped owing to a short-circuit. In this case, the code indicating the closure of the circuit is first transmitted to the control office and upon the operation of the corresponding supervisory " Closed " signal, the control code which normally effects the opening of the circuit-breaker is automatically sent back to the substation. The receipt of this code stops the transmission of the closure signal and causes the transmission of the signal code which operates the " Open " signal, so that the successive operation of the " Closed " and '' Open " signals indicates to the control operator that the attempted closure of the circuitbreaker has failed owing to the presence of overload conditions. If the supervisory " Closed " signal does not operate, the transmission of the signal code is automatically repeated These operations take place in the same manner whether the attempted closure is due to automatic control at the substation or to distant control by the operator. The invention is described with reference to a system which is similar to those shown in Specifications 216,085 and 220,309, the points of difference being referred to in detail in the succeeding paragraphs. Operation under overload conditions. If, upon the closure of the circuit-breaker C, there is an excess of current through the transformer T due to a short-circuit, relay 475 energizes, operates the tripping coil 488 of the circuit-breaker, and energizes relay 476 which locks up and energizes relays 420, 421, 422 to start the transmission of the signal code. as described in the above-mentioned Specifications. Relay 476 also connects ground over wiper 514 to the 24th contact 590 in the bank of the wiper 556 of the code-sending switch CD 1 so that when this contact is reached, a further pause occurs in the impulse transmission and the corresponding-pause at the connector switch H1 causes the relapse of a relay 680 which completes a circuit 631, 684, 681, 648 for relay 781 which locks up. The signal-operating circuit 610, 660, 726, 720, 700, which is closed when both switches pause simultaneously in their 25th positions, includes a relav 782 which in conjunction with relay 781 and the signal-operating relay 700 completes a circuit 694, 644, 785, 788, 726, 720, 715, 185, 106, 714 in which relay 106 operates and causes the transmission by the codeswitch CD of the code which normally effects the operation of relay 491 to open the circuit-breaker C. In the present case, the circuit-breaker is already open but relay 491 also short-circuits relay 476 to stop the transmission of the " Closed " code and completes other circuits for relays 420, 421. Relay 422 being now de-energized, the code for signalling the open condition of the circuit-breaker is now transmitted. Since relay 476 remains locked up until it is shortcircuited by relay 491, the code for operating the " Closed " signal will be repeatedly transmitted until the correct supervisory signal has been operated, and since relay 106 remains locked over the circuit 176, 173, 106, 183, 714, the code for opening the circuit-breaker will be repeatedly transmitted back to the substation until the relay 700 has been de-energized to display the "Open" signal. Checking supervision. As in the above-mentioned Specifications, the operation of a special checking key K5, by energizing a relay 191, causes the transmission of a special code to energize relays 401, 402, 403, which operate all relays such as 420, 421 and thus cause the transmission. of checking supervisory signals for all apparatus at the substation. In addition, in the present system, this checking code is also sent if the switches CD 1, HI get out of synchronism and do not reach their 25th positions simultaneously in which case no supervisory-signal circuit is completed, relay 782 does not operate to unlock relay 780, and relay 191 is operated over the circuit 184, 783, 646, 685 upon the restoration of the switch H1 to normal.