US2154742A - Electrical signaling system - Google Patents

Description

April 1939- P. F. G'UNNING 2,154,742

ELECTRICAL SIGNALING SYSTEM Filed Oct. 14, 1936 f/v VEN TOR Faker FRANK GUNN/NG ATTY.

Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE ELECTRICAL SIGNALING SYSTEM ware ' Application October, 14, 1936, Serial No 105,460

In Great Britain November 5, 1935 11 Claims.

The present invention relates to signaling systems for the remote supervision of'the condition of circuit breakers or the like. located at an electric power substation and is particularly suitable for signaling to a central point from a plurality of substations. For example, in a large electric power network comprising a number of substations, it is not usually a commercial proposition to indicate automatically over pilot wires the oil circuit breaker positions from all substations owing to the prohibitive cost of the pilot lines and equipment required; nor is it a commercial proposition to have the smaller substations continuously staffed, principally on account of these stations being generally in the majority.

The chief object of the invention is to provide a simple and cheap apparatus which can be associated with the ordinary telephone at a remote substation thus obviating the need of special signaling channels to the control centre. The arrangement is preferably such that if when the substation is called there is no verbal reply due to the absence of an attendant-an audible signal will be returned to the caller which signal in addition to giving an indication of the condition of equipment at the substation may also indicate to the caller which substation is responsible for the signal. At the same time the association of the indicating apparatus with each substation telephone neither interferes with nor reduces the efficiency of the telephone system as a whole. It should be mentionedthat the term substation has been used for convenience to cover any point wheregeneration, transformation and/or control of electric power may be effected.

According to one feature of the invention in a signaling system for the remote supervision of the condition of circuit breakers or the like at an electric power substation the supervisory circuit is completed in response to the setting up of a connection over the regular tele phone network.

According to another feature of the invention the necessary information is transmitted by audible signals over a line equipped for telephony over the regular exchange network.

A further feature of the invention is that apparatus responsive to an alteration in the condition of the equipment at the substation causes a call to be set up over the regular telephone network to give warning of such alteration.

According to still another featureof the invention an electric power substationis provided with equipment which is set in operation responsiVe to an incoming telephone call which is not answered within a predetermined time and thereupon transmits audible signals to the calling party to indicate the condition of the circuit breakers or the like at the substation.

The invention will be better understood from the following description of one method of carrying it into effect reference being had to the accompanying drawing which shows, in Fig. 1, a circuit diagram of the apparatus in association with the telephone instrument at a substation.

Fig. 2 shows a circuit diagram of the apparatus used in connection with the circuit breakers to control the transmission of tone pulses indicative of the condition of the circuit breakers.

In the arrangement shown, facilities are also provided whereby a change in the condition of any of the equipment concerned may be auto matically indicated at the telephone exchange even though no call is put through to the substation. It will be appreciated that if this latter facility is not required, the circuit can be still further simplified.

The direct current supply foroperating the equipment is shown by positive and negative symbols in a circle and may be any convenient voltage preferably obtained from a battery so that it would still be available if the main power supply shouldfail. It should also be mentioned that since relay OCB is normally operated the armatures ocbl and 00112 of this relay have been shown in operated position. The switches D, comprising the magnet DM and bank sets DI, D2 and D3, and S comprising the magnet SM and bank sets SI, S2, S3, and S4, which are of the electromagnetically operated step by step type used in telephone systems have been shown as having 25 contacts which is a usual construction but it may be more convenient in practice to provide them with two sets of single ended wipers located at 180 so as to give the eiiect of a 50-point switch.

For the purpose of the description it will be assumed first that the substation is unattended andthat a call is put through to it from the control centre. When ringing current is applied at the exchange to the telephone line the telephone bell BL will be rung while at the same time relay ST will be operated in parallel by way of condenser .QA. This relay is conveniently shunted by a rectifier MRA to enable an ordinary telephone type relay to operate satisfactorily on alternating current. Relay ST upon operating, at armature stl operates relay A which in turn operates relay B. The latter relay then at armature bi energises the magnet SM of the switch S which is of the reversedrive type and therefore does not move its wipers on energisation of the magnet. The interrupter contacts cm are opened however and accordingly the operating circuit of relay A is disconnected. Relay A thereupon releases after a slight interval and in turn releases relay B, which after .a further short interval de-energises the magnet SM whereupon the wipers are advanced to position 2. Positive is then extended over wiper SE to re-operate relay A and the interaction between relays A and B and magnet SM is repeated and causes the wipers to be advanced step-by-step round the bank at a speed of the order of five steps per second or less, this speed being controlled by the copper slugs on the two relays.

When the wipers of switch S reach position 25 the magnet DM of the switch D is energised over wiper S2 in parallel with magnet SM from armature b I and on release of relay B, the switch S is advanced to position i while the switch D is advanced to position 2. Positive is now extended over wiper D3 to operate relay SS which at armature ss2 bridges the winding of the transformer T directly across the line in order to trip the ringing at the telephone exchange and at armature ssl prepares a circuit for the self-interrupted tone generating relay TR. Relay ST releases due to the cessation of ringing current but the switch S continues to step since relay A is re-operated in position I by way of wiper DI in position 2. The first rotation of the switch S is thus used to time an interval during which the station attendant may answer the telephone and pass on the information verbally. If however the telephone is unanswered during this period, then on the second and subsequent rotations of the switch S, tone indicating signals will be impressed on the incoming telephone line in a manner now to be described.

It will be seen that bank contacts engaged by wipers S3 and S4 are wired to a cross-connection frame, to which are also wired signaling contacts on the equipment to be supervised, in this case, three oil circuit breakers. During each rotation of the switch S positive potential picked up by wipers S3 or S4 will operate relay P and since relay SS is now operated, armature pl will on each operation energise the tone relay TR from the local dry battery BA and an audible tone will be impressed by induction through the windings of the transformer T on to the line and thus transmitted to the calling party. If relay P is operated over wiper S3 a pulse of tone will be sent out for the full period during which the wipers are resting in that position while if it is operated over wiper S4 tone will be sent out only for the period during which relay A is operated, which period represents approximately half the time the wipers remain in each position. It will be assruned by way of example that the code signal representing the particular substation responsible for the signal comprises three dots or short pulses of tone. An indication will then be given of each circuit breaker in turn, a dash or long pulse being transmitted when a particular breaker is in a closed position while a dot is transmitted if it is in a tripped or open position. The whole cycle for this particular substation with the first and third breakers closed and the second breaken open would thus be: dotdot-dotsilence-dashsilence-dot silence dash, this cycle being repeated for any predetermined number of times in a manner to be described later.

Accordingly on this assumption contacts 8, I6 and 24 in the bank of wiper S3 are cross-connected to signaling contacts of the breakers concerned and contacts I, 2, 3, 8, l8 and 24 in the bank of wiper S4 are connected to positive. Thus on rotation of the switch wipers relay P will be operated over wiper S4 for the operated time of relay A on each of the first three steps thus transmitting the station identification signal consisting of three short pips of tone to the calling party. In position 8 since breaker 0013! is closed, a long pulse of tone will be transmitted, in position I6 since breaker OCB2 is open a short pulse is transmitted while in position 24 a long pulse is transmitted since breaker OCBS is closed.

It will be seen that with the arrangement described the switch S serves to control the initial delay period and also the actual sending of the supervisory signals. By simple alterations of the strapping arrangements, any variation of the code combination and any desired relation be tween the lengths of the long and short pulses can be effected. Thus by arranging that each marking in the bank of wiper S3 occupies two strapped contacts, the long pulse can be made much greater than the short pulse, though it would then be necessary to employ bridging type wipers to prevent disconnection of the pulse during the transit time between contacts. Each breaker indication might, moreover, be preceded by a number of short pulses corresponding to the breaker number, thus preventing any possible confusion.

When the switch S after its second rotation reaches the last position, the magnet DM will be energised in parallel with the magnet SM as above described and the sending operation of the switch S will be repeated. After any predetermined number of rotations as determined by the strapping of the bank of wiper DI it will be seen that the switch D in making a further step will disconnect the circuit for relay A at its wiper DI thus arresting the motion of the swich S in position I, while the switch D then homes in a self-interrupted circuit over the remaining strapped contacts on its bank DI. Relays A, B and SS will now release and the indicating equipment at the station will then be restored to normal and will send no further impulses to the caller unless he hangs up and re-calls or unless a circuit breaker now changes position. The repeat facility provides a check in case signals are lost or misconstrued on the first cycle.

Considering now a call when the substation is attended, the bell will be rung and relay ST will be operated as before and will initiate the operation of the switch S in the normal manner and this advances step-by-step to time the delay period. If the attendant answers the call before the lapse of this period, the switch-hook contacts SH complete a direct current circuit to the exchange and this trips the ringing whereupon relay ST releases. Relay CO which is arranged to be non-operative in series with the bell and relay ST in response to ringing current, now opcrates and extends positive over wiper D3 in position I to operate relay P which at armature p2 cuts off any circuit for the magnet DM when the switch S reaches the last position. The switch S continues to rotate under the control of relays A and B until it reaches position I when there will be no re-energising circuit for relay A and the switch will be stopped. The station attendant in the meantime may pass verbal information on to the calling party. On release of the connection, relay CO releases and releases relay P and the equipment is again restored to normal.

In case one of the breakers changes position, its indicating contacts will be operated and during the transit time of the contacts in the chain holding circuit for relay OCB, this relay will release. In the alternate position of the contacts a holding circuit is again prepared for relay OCB, since the contacts are closed in both positions of the breaker. Relay OCB upon releasing, at armature ocbl further disconnects its holding circuit and extends positive over Wipers D2 and SI in position I to energise relay A. This relay thereupon starts up the switch S in the normal manner and also each time relay A operates a circuit is completed over armature a3 operated, and armature ocb'2 normal to operate relay SS. Relay SS therefore pulses in synchronism with relay A and at armature 882 the left-hand winding of the transformer T is intermittently bridged across the line thus causing the calling lamp at the exchange to flash. This warns the telephone operator that there has been a change in the condition of the equipment at the station and she will inform the control centre. Thereupon a call is put through to the station in the usual manner in order to ascertain the actual condition prevailing. When the witch S reaches the last position, the magnet DM is energised over wiper S2 and hence when the switch S steps to position I the switch D will be stepped to position 2 in the normal manner. The switch S will commence to rotate a second time but relay SS will now be maintained operated over wiper D3 and the flashing of the operators calling lamp will thus be stopped but a steady calling signal will be maintained. If the operator challenges the line, she will hear the tone indications transmitted by the pulsing of relay P. After the predetermined number of rotations of the switch S, the switch D will home and the switch S will be stopped in the normal position and relays A, B and SS will be released. At armature ssZ the calling signal will now be removed from the main exchange.

It will be understood that if the telephone exchange operated on the automatic principle instead of on the manual principle as above assumed, comparatively small alterations to the equipment would be necessary to enable it to send a train of impulses corresponding to the digit or other code ordinarily used for calling an operator. Moreover the equipment could be arranged to send out the call number of the control centre and transmit the indicating tone signals only when the call was answered though this would involve some increase in the complexity and expense of the equipment.

The tone generating arrangement suggested above using a separate dry battery may be replaced by the use of a tone transformer, the secondary winding of which can be connected across the line at will While the primary is associated with a tone generating relay operated from the signaling equipment battery. Since however it is necessary to isolate the high voltage equipment from the telephone lines as indicated by the dotted line insulation would have to be provided between the transformer windings and this arrangement might therefore prove more costly than the method described.

Wiper S2 and its associated bank are only effective in one position and might therefore be replaced by cam operated contact springs which could be arranged to close only when the wipers are set in the last position.

It will be understood that the supervision need not be confined to breakers but could be arranged to give information about isolators, relay flags, water level, winding temperature, meter readings, transformer taps, protective pilot conditions, battery conditions, voltage, current, power, water pressure, gate positions, valve positions and other data.

By variation of the tone frequency or of the length of time during which the supervisory tone is applied to the line the audible signals can be used for quantitative as well as qualitative supervisory indications. Again, the system can be arranged so that the supervisory telephone can initiate equipment tests or operations at the called s'tation'and the results of these tests or operations can be indicated back to the calling party in the form of audible supervisory signals.

The arrangement described transmits the audible tone signals a predetermined number of times but as an alternative the signaling could be stopped by the arrival of a further call or by the transmission of a tone or other signal from the calling party.

It will thus be seen that with the system according to the invention the facilities of all stations so equipped are available at all telephones on the telephone system and thus in times of trouble when a control engineer is busy, information as to what has happened at a substation may be obtained by other engineers on other telephones thus relieving the control engineer and the tramc on his control telephone. Furthermore the control engineer by simply making a call to a station may ascertain whether the telephone line to the station is good or otherwise thus providing a simple and cheap form of pilot test. In practice this advantage is considerable as the distant station. may be unattended and the prevailing safety regulations may demand that a telephone maintenance ofiicial shall only obtain access to the station when accompanied by one of the power authoritys engineers.

What is claimed is:

1. In a power supervisory system, a power substation, a telephone line connecting said substation with a central office, a tone genera-ting device at said substation, indicating contacts at said substation controlled by circuit breakers, means eifective upon the expiration of a predetermined time interval for rendering said tone generator effective to transmit a. characteristic series of tone pulses over said line for identifying said substation, and means coacting with said indicating contacts for transmitting another characteristic series of tone pulses for indicating the condition of said circuit breakers.

2. In a power supervisory system as claimed in claim 1, a step-by-step switch, and means controlling said switch to measure the predetermined time by the advance of said switch through a given number of steps.

3. In a power supervisory system as claimed in claim 1, a step-by-step switch, means for controlling said switch to measure the predetermined time by the advance of said switch through a given number of steps, and means eifective upon the. termination of said predetermined time interval for connecting said switch to control the transmission of audible signals over said line.

4. In a power supervisory system as claimed in claim 1, a step-by-step switch, means for controlling said switch to measure the predetermined time by the advance of said switch through a given number of steps, means effective upon the termination of said predetermined time interval for connecting said switch to control the transmission of audible signals over said line, and means for terminating the transmission of said audible signals after said signals have been transmitted a predetermined number of times.

5. In a telephone system, a telephone substation, a line connecting said substation with a central ofiice, switching devices at said substation each having an open and a closed position, and means responsive to a change in position of one of said switching devices for transmitting a series of pulses over said line.

6. In a. signaling system, a telephone line, a tone generator, means for controlling said generator to transmit tone pulses of variable duration over said line, indicating contacts controlled by a switching device having a closed and an open position, means for operating said first means to transmit a tone pulse having a definite duration over said line when said indicating contacts are in their closed position, and means for operating said first means to transmit a tone pulse having a different duration over said line when said indicating contacts are in their open position.

'7. In a signaling system, a telephone line, a tone generator, means for controlling said generator to send tone pulses of variable duration over said line, indicating contacts having a closed and an open position controlled by a switching device, a first circuit for operating said means including said indicating contacts, a second circuit for operating said means in multiple with said first circuit, means for closing said first circuit for a definite time interval with said contacts in their closed position, and means for closing said second circuit for a different time interval.

8. In a signaling system, a telephone line, a tone generator, indicating contacts controlled by a switching device having a closed and an open position, a first circuit including said indicating contacts, a second circuit in multiple with said first circuit, and means controlled over said circuits for controlling said tone generator to trans:-

mit tone pulses of variable duration over said telephone line.

9. In a signaling system, a telephone line, a tone generator for transmitting a tone pulse of variable duration over said line, indicating contacts, one circuit associated with the generator and said indicating contacts for controlling the transmission of said pulse for a definite time interval, and another circuit similarly associated for causing a prolonged transmission of said pulse in accordance with a particular position of said indicating contacts.

10. In a supervisory system a substation, a telephone line, a central office having means for calling said substation over said line, a tone generating device at said substation, indicating contacts at said substation, means at said substation operated at a predetermined time after said substation. has been called for operating said tone generator to transmit a characteristic series of tone pulses over said line for identifying said substation, and thereafter coacting with said indicating contacts for transmitting characteristic tone pulses over said line for identifying the condition of said contacts.

11. In a supervisory system, a. substation having an automatic responding device, a telephone line, means controlled over said line for signaling said substation, means in said device operated through a complete cycle when the substation is signaled for measuring a time interval, said means reoperated upon termination of said cycle for causing the transmission of a distinctive series of tone pulses over said line for identifying said. substation.

PERCY FRANK GUNNING.

Images