US2015591A - Control circuit - Google Patents

Description

Sept. 24, 1935. E. D. cooK 2,015,591

CONTROL CIRCUIT Original Filed Aug. 8, 1928 2 Sheets-Sheet 1 /Z l l fmh. WW 6 Fig.2. a 4 W V Inventor: T EI lsworth D.Cook, X i W V Hls Attorney.

Sept. 24, 1935. E. D. cooK 2,015,591

I CONTROL CIRCUIT Original Filed Aug. 8, 1928 2 Sheets-$heet 2 Pi g .4. xsmfa g/ i UUUU" i a9 Inventor:

El lsworth D. CooK, bydfifi /w MW l'l 1's A'tt oTTfiey.

Patented Sept. 24, 1935 UNITED. STATES PATENT OFFICE CONTROL cmcor'r Ellsworth D. Cook, Flushing, N. Y., assignor to General Electric Company, a corporation. of

New York 12 Claims. (Cl. 177 -352) My present application-is a division of my copending application, which matured into Patent No. 1,876,449, entitledControl circuits and which is assigned to the same assignee as my present application.

My present invention relatefio control circuits and more particularly to automatically operating circuit closing devices.

In Patent No. 1,696,566, issued December 25, 1928, of Emmett F. Carter, is disclosed an electron discharge oscillation generator, the operation of which is controlled in response to a control potential which is produced by voice, or other signal, waves. result is effected by utilizing a second electron discharge device connected in the anode circuit of the oscillation generator, the grid of the second device being normally biased negatively to a value such that insufiicient anode current flows to permit the generator to produce oscillations. By applying the control potential to the grid of this second,,cr control electron discharge device, the anode current, and hence, the operation of the oscillation generator may be efliciently and reliably controlled.

In accordance with one aspect of my present invention a coupling between the grid circuit of a control electron dischargedevice, which is utilized in the manner taught'by the above mentioned application, and the circuit of the oscillation generator, is provided whereby oscillations produced by the generator are supplied to the grid of the control device. Control potential is appried to the grid of the control device in the usual manner. When the control potential which is applied to the grid of the control device is of an order such that the impedance of that device is reduced sufllciently to permit anode current to flow in suificient magnitude to permit the production of oscillations, the oscillations produced are supplied back upon the grid 01 the control device. This, in turn, further reduces the impedance of the control device and increases the anode current and the amplitude of the produced oscillations, this accumulative, or regenerative action continuing until the normal operating conditions of the generator are reached. Dependent upon the degree of coupling employed, as will later be eirplained, the oscillation generator will then continue in operation, notwithstanding that the control potential-is removed from the grid of the control device, until, by suitable means provided for the purpose, its operation is interrupted.

As thus arranged the circuit has very important advantages in connection with the operation of electrical devices, such as relays, switches and the like. My present invention has for one of its objects to provide means whereby a system of the type indicated may be applied to the operation of circuit interrupters, such as are used in power transmission lines and particularly to the auto- 6 matic reclosing of such circuit interrupters when power is applied to the line and in response to line conditions.

A further purpose of the invention is to provide means whereby the oscillatory circuits provided, 10 as indicated above, may be utilized not only in the operation of the circuit interrupter but also, in producing signaling operations at a remote point indicating the condition of the switches.

A further object of my invention is to provide an automatic reclosing circuit breaker which operates in response to circuit impedance variations of extremely small magnitude whereby the circuit is capable of efliciently discriminating between impedances of the order of magnitude of full load impedance on the power line in which the circuit breaker is used and a very slightly lower impedance which may be due to a fault on the line.

Still a further object of my invention is to provide a circuit interrupter of the type indicated which is responsive to impedance conditions on the line in either direction from the circuit breaker when power is applied to the line from the opposite direction.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. m invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 represents a portion of the circuits employed in accordance with my invention; Fig. 2 represents certain operating characteristics thereof; Figs. 3 and 4 disclose circuits of this form employed in an automatic reclosing circuit breaker; Fig. 5 indicates a transmission line to which my invention is applied; and Fig. 6

represents an indicating device which may be the cathode conductors of the discharge device 2, space between the cathode and'anode of the device 2, conductor 4, space between the cathode and anode of the device I, choke coil 5, actu- 5 ating winding of relay 8 to the positive side of the source of potential I. The cathodes of the discharge devices I and 2 are energized by means of alternating current applied to the transformers I and 8 respectively. Connected between the grid andanode of the discharge device I is the usual oscillatory circuit 9. This oscillatory circuit is coupled to the grid of the control device 2 through a circuit extending through the secondary winding of a transformer It), the primary winding of which comprises a part of the oscillatory circuit 9, secondary winding of a transformer ll, source of biasing potential I2, to the cathode of the control device 2. The source of potential [2 is of an order such that a negative potential is impressed upon the grid of the control device sufllcient to preclude the flow of current in the anode circuit, or at least sufhcient to maintain this current at a value such that no oscillations are produced by the device I.

The primary winding of the transformer Ii may be connected to any suitable source of control electromotive force. It the device is to be used in connection with the operation of overload circuit breakers this primary winding may be connected in shunt with an impedance I: which is connected in series with the line to be protected. In such application of the system the relay 6 may be used to control the actuating winding of the circuit breaker.

As thus arranged when the potential across the impedance l3, and hence across the secondary winding of the transformer il increases beyond a certain value current will be caused to flow in the anode circuit of the devices I and 2 and oscillations will be produced by the device I. These oscillations will be supplied through the transformer III to the grid of the control device 2. This in turn additionally reduces the impedance of the device 2 and further increases the flow of anode current, thereby increasing the amplitude 01' the oscillations produced. This accumulative or regenerative action will continue until the anode current has built up to its normal value and the oscillation generator i operates under normal conditions.

In the operation of my device it has been found that with a certain relatively close coupling between the windings of the transformer ill at a certain critical valued the control potentiala very slight change in voltage. across the impedance l3 will cause the anodecurrent to build up practically instantaneously to its normal value, that is, substantially square line action of this current may be had. In this manner relay 8, which may require a comparatively large current, may be reliably operated in almost instantaneous response to a very slight variation in the voltage across the impedance l3. With this coupling after the relay 6 has been operated it will be maintained in its energized condition by the.

regenerative connection between the oscillatory circuit 9 and the grid of the device 2.

With a degree of coupling less than the above mentioned certain relatively close coupling, the

rate of increase of anode current with respect to the increase of applied control potential will be dependent upon the degree of coupling employed. This characteristic of the device is illustrated in Fig. 2 in which curves (1 and I) represent the increase in anode current when the degree of coupling is less than that above mentioned, the curve 0 represents the static characteristics of the circuit and curve d represents the increase in anode current when the degree of cou- 5 pling iseither equal to or greater than that above mentioned. If the lesser degree of coupling be employed the anode current will decrease when the control potential is removed and the production of oscillations will cease whereas if a cou- 10 pling corresponding to curve d be employed oscillations and hence the increased anode current will continue to flow notwithstanding that the control potential is removed.

In Fig. 3 I have shown a circuit arrangement 15 of the type shown in Fig. 1 as applied to the automatic reclosing of circuit breakers when power is applied to the line and in response to the conditions of the line. Since my device has the property of sensitive discrimination between 20 potentials such as may be caused to result from varying impedance of the line it has particular utility in this connection.

Referring to Fig. 3, I have shown a circuit interrupter 30 which is included in a transmission 25 line 3!. The transmission line it may comprise a part of a loop circuit such as that shown in Fig. 5, which is later to-be described, and has the characteristic that power may be supplied through the line in eitherv direction. A suitable 30 impedance 3'! is connected in shunt with the contacts of the interrupter 30 so that a portion of the line potential is supplied to that part of the line on the opposite side of the interrupter from which the power is applied. Connected in shunt 35 with the line 3|, or between the line and ground, and upon opposite sides of the circuit interrupter 30, are a pair of transformers 32 and 33 which may comprise the usual distribution transformers of the system. Connected in circuit with 40 the secondary winding of these transformers are the usual load circuits, not shown, and also the actuating windings of relays 34 and 35 respectively. These relays are arranged to control the energization and operation of the circuit 36 which 45 is provided as indicated above foroperating the circuit interrupter 30.

It is thought that this form of my invention will best be understood by reference to its operation. If it be assumed that power is supplied to 50 the transmission line 3| at a point to the left of interrupter 30 it will be seen that full voltage is applied to the relay 34 and that this relay is actuated thereby. Upon operation of this relay 'power will be supplied to an alternating current 55 motor 49 through a circuit extending from the upper terminal of the secondary winding of transformer 32, through the lower contacts of interrupter 30, conductor 50, alternating current motor 49 and upper armature and upper contacts of 60 relay 34 tothe lower terminal of the secondary winding of transformer 32. The alternating cur rent motor 49 drives a direct current generator 43 to energize the anode circuits of devices I, 2 and 38, the cathode circuits of these devices be- [35 mg energized through transformers 5| the primariesv of which are connected in shunt with the alternating current motor 49.

The potential which appears across the secondary winding of transformer 33 is dependent upon 70 impedance conditions on the line 3| beyond the transformer 33 and upon the circuit which is connected to the secondary winding of the transformer. If a heavy load, such as that of a lighting circuit, is connected to the line either through 75 transformer 33 or other transformers to the right the circuit 36 is operated in response to the po- 4 tential of this secondary winding to close the interrupter. By utilizing a coupling between the windings I which is greater than the critical coupling mentioned the circuit may be made to discriminate between a low impedance fault, and the low impedance condition caused by a heavy 1 ad connected to the line notwithstanding that t impedances of the line under these conditions are but slightly different.

If a short circuit, or other low impedance fault condition, exists upon the line beyond the trans-' former 33, or on the secondary load circuit of the transformer 33, potential which appears across the secondary winding of this transformer will not be suflicient to cause the production of oscillations and hence no further operation will result. If the impedance on the line-beyond the interrupter 30, however, be but slightly greater as would be the case if a large' load were connected to the line then sufficient potential will appear across the secondary winding of the transformer 33 to cause the operation of the equipment winding of transformer 40, a portionof resistance 4|, upper armature and its lower contacts of relay 35 to the lower terminal of the secondary winding 33. It will be understood that this potential is not sufficiently great to cause the actuation of the relay 35. This potential is amplified by the device 38 and supplied through transformer 42 and secondary winding of transformer ll] of the discharge device I to the grid of control device 2, these circuits being as indicated in Fig. 1. Oscillations will be produced by the device I and supplied to the grid of the device 2, causing full anode current immediately to build up in the anode circuit of thesedevices. Thiscircuit extendsfrom the negative side of the source of potential 43 through smoothing reactor 44, space between the cathode and anode of the discharge device 2, space between the cathode and anode of discharge device I, choke coil 5, relay 6 to the positive side of the source-of potential 43. Relay 6 will then be energized closing a circuit which extends from the upper terminal of the secondary winding'of the transformer 32 through conductor 39, lower contacts of the circuit interrupter 30, actuating winding of relay 45, conductor 46, contacts of relay 6, conductor 41, conductor 48 and upper armature and its upper contacts of relay 34, to the opposite side of the secondary winding of transformer 32. Relay 45 will then be operated t hereby deenergizing the alternating current motor 49 and deenergizing the anode and cathode circuits of the devices I and 2.

After the circuit interrupter 30 has been actuated to its closed position full potential will be applied across the primary of transformer 33, thereby actuating the relay 35 to its upper position. This operation interrupts the circuit of the primary of transformer 40 at the upper armature and lower contacts of relay 35 such that the high potential of the secondary winding of transformer 33 is not impressed upon this transformer. The

interrupter 30 may be retained in its closed posi-' tion, and operated to its open position, by any of the usual expedients which are well-known in the art.

If we assume that the interrupter 30 is in its open position and that power is supplied from the right-hand end of the line, relay 35 will be energized and relay 34 will be in its lower position. In closing its upper contacts relay 35 completes the circuit for the motor 49, which extends from thejupper terminal of the secondary winding of transformer 33 through conductor 39, lower contacts of interrupter 30, conductor 50, alternating current motor 49 and the primary winding of cathode transformers in parallel, conductors 52 and 48, upper armature and its upper contact of relay 35 to the lower terminal of the secondary winding of transformer 33. The cathodes of the discharge devices will then be energized and the motor 49 will drive the direct current generator 43 to supply power to the anodes of the different discharge devices. If the impedance of the line at the left of interrupter 30 be sufficiently great potential will be applied through the upper armature and its lower contacts of relay 34, a portion of resistance 4| and transformer 40 to the grid of the amplifier 38, such that when amplified and applied to the control device 2 through transformer 42 the device I will produce oscillations and cause the energization of the relay-6. The interrupter'will then be operated to its closed position as before thereby deenergizing the circuits of the devices I, 2 and 33. Operation of relay 34 will then protect the transformer 40 from the high potential of the secondary winding of transformer 32.

It will be noticed that the device I produces oscillations until the circuit interrupter has been closed. These oscillations may, if desiied, be supplied as carrier currents to the transmission line by any suitable means. As illustrated this means comprises a pair of coupling condensers 53, which are connected to the transmission line 3| on opposite sides of the interrupter 30. One terminal of each of these condensers is connected through the winding 54 which is in inductive relation with the oscillatory circuit of the oscillation generator I to ground.- Thus during a predetermined time interval prior to the operation of the circuit breaker, high frequency oscillatory currents are supplied to the transmission line for transmission in eitherldirection. These currents may be received at a remote point to indicate that the circuit breaker has operated. The interval during which these currents are produced may be made as long as desired by any suitable time delay mechanism which may be associated with the relay 6, for example, to retard its operation If for some reason, as due to an inoperative condition of the switch 30 such'as might result from faulty toggle mechanism, or the like, the circuit interrupter does not closeafter the relay 6 has been operated, it will be seen'that carrier curwinding of relay 45, conductor 63,

thereby indicating, in a manner later to be described, that the switch is in faulty condition.

transformers 32 and 33 are of the double secondary type. It will further be noticed that the circuits of the electron discharge devices I and 2 are energized by means of alternating current which is supplied through a transformer 55 having a plurality of secondary windings 56, 51, 58, 59 and B0. The winding 56 is utilized to energize the anode circuit of two asymmetrically conducting electron discharge devices 6| and 62, which are connected to supply direct current biasing potential to the grid of the control device 2. The winding 51' supplies heating current to the cathodes of these devices. The windings 58 and 59 supply heating currents to the cathodes of the devices 2 and l respectively and the winding 60 supplies potential to the anode circuits of these and 2 extends from the cathode conductors of the device 2 through the-space between the cathode and anode of this device, cathode conductors of the device I, space between the cathode and anode of the device I, choke coil 5, relay 6, and winding 60 to the cathode conductors of the device 2.

The operation of this form of my invention is as follows: If it be assumed that power he received from'the left-hand end of the circuit 3| and that the ,main contacts of the interrupter 30 are open the relay 34 will be energized. This relay. will complete an energizing circuit through the lower contacts of interrupter 30 for the pri mary of transformer 55. Potential will be supplied, as before, through resistance 31 to the opposite end of the circuit and a portion of this potential will appear across the secondary winding of the transformer 33. This potential will be supplied through the lower contacts of relay 35 and transformer 40 to the grid of the control device 2. If the impedance conditions beyond the transformer are such that the main contacts of the interrupter 3;] may properly be closed this potential will be sufliciently great to cause suflicient current to flow in the anode circuits of devices I and 2 to cause the device I to produce ,oscillations and the relay 6 to be operated. The

operation of the relay 6 completes a circuit extending from the lower terminal of the secondary winding of the transformer 32, through conductor 46, contacts of relay 6, conductor 48, actuating lower armature and its-upper contacts of relay 34 to the upper terminal of the secondary winding of transformer 32. Relay 45 will then close its contacts, thereby energizing, through an obvious circuit, the actuating windings of the interrupter 30, causing this interrupter to close its main contacts and to open its auxiliary contacts 64, thereby interrupting the supply of energy to the transformer 55, and the operation of the oscillator l. The interrupter 30 will then be maintained in its closed position by mechanical or other means customarily employed in connection with switches utilized for this purpose.

When power is supplied from the right-hand end of the circuit it will be apparent that the operation of devices I and 2 is the same except that their operation is dependent upon line conditions beyond the transformer 32.

L} It will be noticed that the oscillation generator of this figure is similarly provided with an 2,015,591 rents will be continuously supplied to the line,

output winding 54 which is adapted to apply high frequency currents through condensers 53 to the line for transmission ineither direction.

Since the-anode circuit of the oscillation generator is supplied with alternating potential it opcrates only during the portion of the alternating current cycle during which the anode is at positive potential. Accordingly if the line impedance in the direction opposite to that from which power is supplied is such that oscillations are 10 produced by the device I but this impedance is reduced, as due to trouble on the line, before suiiicient time interval has elapsed to permit closing of the interrupter 30 the operation of the device I will be interrupted and the interrupter 15 30 will not be closed.

In Fig. 5 I have shown a transmission circuit in connection with which my invention has particular utility. The transmission line comprises a loop extending from a power station 66. 20 Power may be supplied to either end of the loop through interrupters 61 and 68 located at the station. Distributed about the loop are a plurality of interrupters 30, associated with each of which is apparatus 69 which may be of the type 25 indicated in either Figs. 3 or 4. Located at the station and associated with each end of the loop 65 is a high frequency responsive circuit, such as is shown in Fig. 6. The circuit is of any wellknown construction employing an electron discharge detector 12 which is connected to the line through a transformer 10 and a coupling condenser 'H. Either, the primary or secondary of this transformer, or both may be tuned to the frequency of oscillations produced by the gen- 35 erators in the different devices 69. Connected in the output circuit of the electron discharge device. 12 of the receiving circuit is the actuating winding of an ordinary step by step selector switch having an armature 13 which is adapted 40 to be actuated over a bank of contacts H by means of a suitable ratchet and pawl arrangement of well-known form. Each contact 14 is connected in circuit with a suitable signal lamp l5, and source of potential 16, such 45 that when the armature 13 engages any one of these contacts a corresponding lamp I5 will be lighted. Also connected in the anode circuit .of the rectifier I2 is a relay 1! which is adapted when energized to close the circuit of a signal 50 lamp 18 for a purpose later to be indicated.

' Let us assume that a fault has occurred in that section of the loop circuit 65 which is indicated by an X in the drawings and'that all of the interrupters are in their open position. The op- 55 orator at the station 66, desiring to ascertain in what section the fault lies will first close the switch 61 and supply power to the left-hand end of the loop circuit. Since the impedance condition between the first and second interrupters 60 from this end of the line are proper,- one interrupter 30 will be closed. Since a fault exists in the next section the next interrupter'will not close with the result that only one high frequency impulse will be supplied to the receiving appa- 65 ratus associated with the left-hand end of the loop atthe station 66. The armature 13 of the selector switchof thisapparatus will engage its first contact and cause the first one of the lamps 15 to be lighted. The operator will then close 70 the switch 68 which is associated with the opposite end of' the line. Since the impedance conditions in all of the sections to the right of the section marked X are correct four of the switches 30 will be closed and the selector which is associated with the righthand end of the loop will engage its fourth contact, thereby energizing a correspondinglamp. The operator is then in-' formed that the fault lies between the second and third interrupters from the left. If for any reason any of the switches 30 do not close notwithstanding that the impedance conditions in the direction opposite from that in which power is supplied is correct, then high frequency currents,

from the oscillation generator associated with that switch will be continuously supplied to the line causing the relay 1! to be continuously energized and the lamp 18 to be lighted. 'Thus for example if the operator observes that the third lamp in the bank of lamps 15 is lighted and that the lamp 18 is also continuously lighted he will know that the mechanism of the third switch from the end of the line at which power is supplied is faulty. If the lamp 18 were "not lighted the operator-would be informed that the difliculty lies in the line section beyond the next switch rather than in the switch itself.

If power is supplied at both ends of the loop circuit and the entire line is in good condition all of the switches will be closed. When the last switch closesydue to the fact that power is supplied at both sides of the switch, it will be seen that both of the relays 34 and 35 will be energized and will close their upper contacts. Resistances 4| prevent the occurrence of a short circuit on transformers 32 and 33 when this occurs. When these relays operate the circuit of the primary winding of the transformer 40 is interrupted and the high potentials which exist upon the transformer windings 32 and 33 will be prevented from causing the circuit 36 to operate.

an actuating winding, means for energizing said winding thereby to actuate said interrupter in variable time response to energy received over said. line in either direction said means including a self oscillatory circuit, mcans for varying the rate at which oscillations in said oscillatory cir-' cuit build up, and means utilizing the variable rate of building up of said oscillations to vary the time of response of said interrupter. 0

2. In combination, a power transmission line, a circuit interrupter included in said line, means for producing electrical oscillations in combined response to energy received 'over said line in a certain direction and to the operating condition of said line in the opposite direction from which energy is received, means for accelerating the rate of building up of said oscillations, and means for operating said interrupter in response to the oscillations produced, whereby said interrupter is operated in rapid response to said energy received over the line. from said certain direction dependent on the condition of the line in'the opposite direction.

3. In combination, a power transmission line including a plurality of circuit interrupters, means for actuating each interrupter in com bined response to energy received over said line from a. certain direction and to the operating condition of the line in the direction opposite to that from which energy is received, said means including means for supplying continuous carrier current to the line during the period required for operation of said last means for transmission in the direction from which energy is received,

. and means responsive to said carrier current for The interrupter 30 will then be closed directly.

The circuit of the actuating coil of relay 45 extending in the case shown in Fig. 3 from the upper wrminal of the secondary winding of transformer 33 to auxiliary contact 64 of the switch 30, actuating winding'of relay 45, lower armature and contacts of relay 34, lower armathrough a circuit extending from the upper terminal of transformer 33 through the lower armature and its upper contacts of relay 35, conductor 63, actuating winding of relay 45, upper armature of relay 35, upper armature of relay 34 and conductor 46 to the lower terminal of the transformer 33. Relay 45 will then be actuated to connect the actuating winding of interrupter 30 in shunt with 'the secondary windings of transformers 32 and 33.

While I have shown particular embodiments of my invention it will, ofv course, be understood that I do not wish to be'limited thereto since many modifications, both in the circuit arrangement and in the instrumentalities employed,

may be made without departing from the spirit and scope of my invention as set forth in the appended claims.

What Igclaim as new and desire to secure by Letters Patent of the United States, is:

1. In combinatioma power transmission line,

a circuit interrupter included in said line having indicating the operation of said interrupters.

4. In combination, a power station, a transmission line extending from said station including a plurality of circuit interrupters located at intervals along said line, means at the power station for supplying energy to the line, means located at each interrupter which is responsive to,

energy received from the station and to the operating condition of the line beyond the interrupter for initiating the operation of the interrupter and for supplying continuous carrier energy to the line, means for interrupting the supply of carrier energy after the interrupter has been operated and means at the power station responsive to saidcarrier energy for indicating the number of interrupters, which were operated and for indicating an inoperative condition of any interrupter.

5. In combination, a power station, a line comprising a loop extending from said station, a plurality of switches located at spaced intervals around said loop, means located at each switch which is responsive to energy received over the line in either direction and to the operating 'condition of the line in the direction opposite to that from which energy is received for operating the interrupter and for supplying a single carrier impulse to the line for transmission in either direction, and means located at the station responsive to carrier impulses received from the line for indicating the operation of the switches.

6. In combination, a power transmission line, an interrupter included in said line, an impedance connected in shunt with said interrupter, means including an electron discharge oscillation generator for actuating said interrupter, means responsive to energy received'from either direction over said line for energizing said oscillation generator and for causing said generator to produce oscillations in response to potential on the line on the side of said interrupter opposite to that from which power is received thereby to cause the operation of the interrupter.

7. In combination, a power transmission line, an interrupter included in said line, an impedance connected in shunt with said interrupter, an electron discharge oscillation generator having a control element, means for supplying potential from the line on either side of said interrupter to said control element, means responsive to energy received over said line in either direction for interrupting the supply of potential from, the direction in which energy is received to said control element whereby said generator operates in response to potential on the line on the opposite side of said interrupter from which energy is received to which said last means responds, and means for operating said interrupter in response to the oscillations produced.

8. In combination, a power transmission line including a plurality of circuit interrupters, means for actuating each interrupter in combined response to energy received over said line from a certain direction and to the operating condition of the line in the direction opposite to that from which energy is received, said means including means for supplying a carrier current impulse to the line for transmission in the direction from which energy is received when each interrupter is operated, whereby when power is supplied to the line at one end thereof a number of carrier current impulses are supplied to said line for transmission toward said end dependent upon the number of interrupters operated.

9. In combination, a power station, a. transmission line extending from said station including a plurality of circuit internipters located at intervals along said line, means at the power station for supplying energy to the line, means located at each interrupter which is responsive to energy received from the station and to the operating condition of the line beyond the interrupter for initiating the operation of the interrupter and for supplying carrier energy to the line, and means for interrupting the supply of carrier energy after the interrupter has been operated, whereby when power is supplied to the line at one end thereof a number of carrier impulses are supplied to said line dependent upon the number of interrupters operated and carrier energy is continuously supplied to said line upon failure of any interrupter to complete this operation initiated by the second recited means.

10. In combination, a transmission line having a number of circuit interrupters located at spaced intervals therein, means associated with each interrupter responsive to energy from one direction and to the operating condition of the line in the opposite direction for operating the respective interrupter and for supplying a carrier energy impulse to the line for transmission in the direc--- tion from which energy is received and for supplying a continuous carrier impulse to said line upon failure of the associated interrupter to operate, whereby when power is supplied to the line at one end thereof a number of impulses are transmitted toward said end dependent upon the number of interrupters operated and a continuous impulse is transmitted upon failure of operation of an interrupter and means at said end responsive to said carrier energy to produce an indication dependent upon the numbenof impulses received and to produce a different indication in response to receipt of continuous carrier energy.

11. The method of indicating the condition of a plurality of remote automatic reclosing circuit breakers connected at intervals in a line which comprises supplying power to said line, thereby causing each of said breakers to operate, supplying carrier energy to the line during the interval required for operation of each breaker, and indicating the number of impulses supplied to the line.

12. The'method of indicating the condition of a plurality of remote automatic reclosing circuit breakers connected at intervals in a line which comprises supplying power to said line, thereby 40 cating the duration of said carrier energy im- 4 pulses supplied to the line and the number of said impulses.

ELLSWORTH D. COOK.

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