Patent GB-307469-A (GB)
Abstract: 307,469. British Thomson-Houston Co., Ltd., (Assignees of Stewart, C. M.). March 8, 1928, [Convention date]. Selective distant control systems; tell-tale apparatus. - Relates to a system for selectively controlling or supervising any one of a plurality of units, such as circuit breakers, meters &c. located at a remote station. Fig. 1 shows the apparatus at the control station and Fig. 2 shows the apparatus at the substation at which four circuit breakers 1<1>, 2<1>, 24<1>, 25<1> only are shown. Groups of circuit breakers are appropriated to stepping switches, such as A<1>, B<1>, and the circuit breakers are controlled by corresponding keys arranged in groups associated with switches, such as A. B. During a selective operation corresponding group switches A, A<1> at the control and substations respectively are operated synchronously and then the succeeding group switches B, B<1> are operated, transfer being effected under the control of stepping switches T, T<1>. If more than two group switches are provided at each station, the corresponding switches are operated successively in a simitar manner to associate the circuit breakers with their appropriate control keys. The switches at each station are driven by polarized line relays p, p<1> under the control of alternate impulses of reverse polarity transmitted over the line wire s. The control of a selected emit is effected over line c and supervision is effected over line i. The line r constitutes a common return line and may be replaced by an earth return. Selection. Assuming it is desired to select a circuit breaker for operation its corresponding " stop " key 3 is operated to ensure that the selecting switches stop in the selecting position and a " start " key 6 is operated to initiate the stepping operation of the selecting equipment. The key 6 energizes a relay 44 at the substation over the normal contacts of wipers i of the first group switches A, A<1> and line i to complete the line circuit S over wipers s of switches A, A<1>, normal contacts of Wipers t<1111> of switches T. T' and polarized relays p, p<1>. Operation of relays p, p<1> energize the self-interrupting stepping magnets 48, 49, of switches A, A<1> in local circuits and the switches are moved one step. Battery polarities are reversely connected on alternate contacts of the banks s of switches A, A<1> so that operation of the switches through one step causes operation of the polarized relays p, p<1> in the reverse direction to again operate the stepping magnets 48, 49 and cause a further step of the switches. In this manner switches A, A<1> are driven in synchronism until when the wiper s of switch A engages a contact from which battery potential is removed by tha operation of the appropriate " stop " key 3, the stepping operation ceases and the switches A, A<1> remain in their selecting positions. Control of selected unit. The selected unit and its corresponding control key and supervisory apparatus are connected over the line wires c, i, and the appropriate wipers of the switches A, A<1>. The control key 4 and the " master " key 7 are operated to energize a polarized relay, say 271, associated with the selected circuit breaker, over a circuit including wipers c of switches A, A<1> and line c. The relay 27<1> is operated according to the polarity of the operating current to energize the " closing " or " trip coil of its circuit breaker. While the selecting switches remain in their selecting positions, control may be effected as often as desired by manipulation of the control key 4, Supervisory signalling. When the circuit breaker changes its position a circuit is established by auxiliary contacts 34 or 35 over the wipers i of switches A, A<1> and line i for a polarized relay, such as 27, which reverses the indications of the green and red lamps g, r, and extinguishes a white lamp w which is illuminated when the control key is operated. Restoration of selective equipment to normal. After receiving the answer back supervising signal, the operated " stop " key is restored and stepping of the switches A, A<1> is resumed. When the wipers t engage their final contacts circuits are extended to wipers t of the succeeding group switches B, B<1> which in their normal positions close circuits for the stepping magnets 57, 58 of the transfer switches T, T<1> which are thereby moved one step. This operation transfers the line wires to the wipers of the switches B, B' which are then operated in a manner similar to that of the switches A, A<1> until co-operation with the final contacts in the banks t prepares circuits for restoring the switches A, A', B, B<1> to normal. If however more than two group switches are provided the switches B, B<1> again operate switches T, T' to bring into operation the third group switches and this operation is repeated until all the group switches are operated. During operation any pair of group switches may be stopped in a selecting position by operating the appropriate " stop " key. When switches B, B<1> engage their final contacts, switches T. T<1> are again operated and close a circuit over wipers t<111> for magnets 59, 60 which step the switches B, B<1> to normal. Circuits are then closed over wipers t of switches A, B, A', B<1 >for magnets 57, 58 and the switches move a further step to operate magnets 48, 49 and restore, switches A, A<1> to normal. The switches T, T<1> are then moved a further step and the system is restored to normal condition. Signalling automatic operation of circuit breaker. When a circuit breaker changes its position a normally energized relay such as 31 is released at auxiliary contacts 34, 35 to operate a relay 36 which initiates stepping of the switches in a manner similar to relay 44. The switches are operated in synchronism and when they cooperate with contacts associated with the operated' circuit breaker, the appropriate lamp at the control station is illuminated, the relay 31 is re-energized, and the white lamp w, also is operated to signify that the positions of the circuit breaker and its control key are not in agreement. Reversal of the control key extinguishes the white lamp. Auxiliary signalling apparatus. In the normal position of switches A, A' a relay 61 is operated over the line wire c. When the switches are moved off normal due, say, to the automatic operation of a circuit breaker or an abnormal condition such as an inductive surge on the lines, the relay 61 is de-energized to release a relay 42 and thereby extinguish a normally illuminated lamp G, interrupt the " start " circuit at the control station, and release a relay 63 to operate an alarm bell 8. If a key 9 is open continuous ringing of the bell 8 is effected but if closed a relay 64 is operated to re-energize the relay 63 and thereby limit the operation of the bell to a single stroke. The bell 8 remains ineffective when the switches move off normal in response to the operation of the " start " key 6 as this key short-circuits contacts of relay 42. When however the switches return to normal relay 42 is re-operated and the bell is rung. Preventing interference from inductive surges on the line wires. In order to prevent an inductive surge initiating a re-operation of the switches at the moment when they restore to normal, a slow-acting relay 46, which remains inoperative during impulsing and thus opens at contacts 66 the normal circuits over the line relays p, p<1>, is operated when impulsing ceases to release slow-release relay 47 which also controls a contact 67 in the line circuit. In this manner the normal line circuit remains open for a predetermined time during which a surge may leak off through a resistance 65. Preventing control operation in the event of asynchronous operation of switches. When the switches after synchronous operation are stopped upon corresponding contacts, a relay 69, which normally is impulsed by alternate impulses of reverse, polarity in such a manner that its armature remains unattracted, is operated to energize a holding relay 53. If however the switches fall out of synchronism, relay 69 is de-energized to release relay 53 and thereby interrupt the control circuit, Restoring switches after a synchronous operation. Operation of the " reset " key 5 earths the line s intermediate between the relays p, p<1> to cause independent restoration of the switches at each station to normal. Checking positions of circuit breakers. The position of all the circuit breakers is checked upon operation of the " start " key to initiate a complete cycle of operations of the selective equipment.