US3751678A

US3751678A - Circuit breaker device

Info

Publication number: US3751678A
Application number: US00198799A
Authority: US
Inventors: K Kawasaki; K Oose
Original assignee: Fuji Electric Co Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 1970-11-20
Filing date: 1971-11-15
Publication date: 1973-08-07
Anticipated expiration: 1990-08-07
Also published as: CA946062A; JPS5132230B1

Abstract

A circuit breaker device comprising a main circuit breaker unit adapted to interrupt the flow of a large current and an auxiliary circuit breaker unit adapted to interrupt the flow of a current smaller than the first-mentioned current and connected in series with the former unit, the operating speed of the main circuit breaker unit being set quicker than that of the auxiliary circuit breaker unit, a circuit-breaking operation of the main circuit breaker unit being initiated only when a load current which is too large for the device occurs.

Description

United States Patent Kawasaki et al.

[ Aug. 7, 1973 CIRCUIT BREAKER DEVICE [75] Inventors: Kikuo Kawasaki; Katsuhiro Oose,

both of Kawasaki, Japan [22] Filed: Nov. 15, 1971 [21] Appl. No: 198,799

Primary Examiner-Herman J. Hohauser Att0rneyl-lolman & Stern [57] ABSTRACT A circuit breaker device comprising a main circuit breaker unit adapted to interrupt the flow of a large [30] Foreign Application Priority Data N 2 4 current and an auxiliary circuit breaker unit adapted to 0v. 0,1970 Japan, 45/10254 interrupt the flow of a current smaller than the first mentioned current and connected in series with the forg% 307/136 200/146 mer unit, the operating speed of the main circuit 146 breaker unit being set quicker than that of the auxiliary I 1 B g ia 'ijg l H circuit breaker unit, a circuit-breaking operation of the V I H main circuit breaker unit being initiated only when a I load current which is too large for the device occurs.

[56] References Cited 7 V UNITED STATES PATENTS 10 Claims, 7 Drawing Figures 2,032,149 2/1936 Rawlins..... 200/146 A '8 II AUXILIARY CIRCUIT BREAKER UNIT MAIN CIRCUIT IO BREAKER UNIT CONTROL l7 DEVICE 6 pp I3 l4 TRIPPING OPERATION GENERATOR DEVICE PAIENIEDAUQ mu SHEEI 1 OF 4 zOrEmmmO OZEEE. v-

mmfik mz FIG. 3

PAIENTEUAm: ma

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PAIENIED M18 I'll I l W IIIIIA VIII, 6 5 I tio TIME

. 1 CIRCUIT BREAKER DEVICE BACKGROUND OF THE INVENTION The present invention relates to a circuit breaker device comprising a main circuit breaker unit adapted to interrupt the flow of a large current and an auxiliary circuit breaker unit adapted to interrupt a current smaller than the first-mentioned current and connected in series with the main circuit breaker unit.

DESCRIPTION OF THE PRIOR ART It is a well known in the art to provide an overcurrent relay or an under-voltage relay in a circuit breaker device thereby to speedily isolate faults caused in a power system. A device comprising, in combination, a circuit breaker and an over current relay mentioned above can be serviceably employed in a simple power system. However, when the power system becomes complicated, it has become impossible to determine, by means of only the simple over-current detecting element or under-voltage detecting element, whether or not the circuit breaker sould conduct its circuit-breaking operation. Therefore, in general, the conventional circuit breaker installed on a power transmission system has a single, func-tion such that the breaking or closing operation is conducted only when the circuit breaker receives a command signal from an external device. Furthermore, whether or not the circuit breaker should be operated is determined by a protective relay and it is a present tendency for the relay to utilize notonly the terminal voltage, current and their phase relation of the circuit breaker but also various elements such as various inputs of other remote terminals, operational conditions of circuit breakers involved in the related other systems and a continuous period of time of a fault, so as to judge the operational conditions of the circuit breaker, utilizing several inputs simultaneously thereby to determine the operation thereof. On the other hand, as the power system is made more complicated, and made greater in capacity, requirements for the circuit breaker become much severe, and it is a matter of great necessity to make the circuit breaker quicker in circuit interruption and larger in breaking capacity. In addition to the above fact, requirements such as an increment of closing and breaking repetition frequency and reduction of noise caused during the operation are becoming increasingly significant and sought after.

In view of an average system fault rate, the necessary number of times of the actual interruption of the fault current is presumed to be once a year or less in the case of a circuit breaker provided in an extra-high voltage system. Speaking of the noise caused by the circuitbreaking operation, there is a great difference in influence between the noise caused once a year and the noises caused every day. If the caused noise is in the order of once a year, a noise of considerably high level could be allowed.

Furthermore, a circuit breaker employing a compressed gas as an arc-extinguishing medium is also well known in the art. The pressure of the compressed gas is raised by means of a compressor and the highly compressed gas is then stored in a tank. The thus stored gas is gradually discharged by the circuit-breaking operation, thereby lowering its pressure. If the gas pressure is thus reduced, it is impossible for the circuit breaker to perform its function. The main circuit breaker unit comsumes gas much more in quantity than the auxiliary circuit breaker unit, as apparent from their circuitbreaking capabilities. Accordingly, with the arrangement of the same compressor and tank, if operation of the main circuit breaker unit is limited to the time when said operation is indispensably necessary, it becomes possible to control the number of the circuit breaking operations which are conducted before the gas pressure is reduced to a pressure at which the circuitbreaking operation cannot be accomplished. Furthermore, in general, it is only necessary to make the operational life of the main circuit breaker unit meet actually the number of times of the circuit-breaking operations caused by faults so that the number of the mainbreaking operations may be several hundreds or less, which renders it possible to provide an economical main circuit breaker unit.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a circuit breaker device in which a main circuit breaker unit and an auxiliary. circuit breaker unit are series-connected, said main circuit breaker unit being constructed compactly and economically. I g

Another object of the present invention is to provide a circuit breaker device which has a reducedoperational noise.

A further object of the present invention is to provide a circuit breaker device which is low in cost and operative at a high speed in interrupting a large current.

A still further object of the present invention is to provide a circuit breaker device which is compact in construction and low in cost, in which the breaking and closing operations of a main circuit breaker unit are limitatively conducted, depending on the magnitude of a current to be interrupted, whereby interruption of a large current is effected significantly fast.

These and other objects and features of the present invention will be better understood when the following detailed description considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:.

FIG. 1 is a systematic construction diagram illustrating a circuit breaker device according to the present invention;

FIG. 2 is a schematic circuit diagram of a control device 17 shown in FIG. 1;

FIG. 3 is a connection diagram of part of an operating coil in the case where electrical detonators are employed for a main circuit breaker unit;

FIG. 4 is a sectional diagram of an electrical detonator section;

FIG. 5 is a sectional view of a main circuit breaker unit which is driven by explosion energy of an electrical detonator;

FIG. 6 illustrates an arrangement adapted to change over an ignition coil of the electrical detonator; and

FIG. 7 is a characteristic diagram illustrating variation of a pressure in an exhaust gas chamber in the case when the circuit-breaking operation of the main circuit breaker unit is conducted.

DETAILED DESCRIPTION OF THE INVENTION With reference now to FIG. 1, there are shown two circuit breaker units: one is a main circuit breaker unit whose operating speed is quick, and the other is an auxiliary circuit breaker unit 11 whose operating speed is slower than that of the main circuit breaker unit 10. These two circuit breaker units are seriesconnected, and inserted in a power system.

In this case, the main circuit breaker unit 10 itself may be, for instance, an electromagnetic repulsion type circuit breaker unit and the auxiliary circuit breaker unit 11 may be, for instance, a mechanically operative circuit breaker unit. A tripping instruction is fed through a conductor 12 to a tripping signal generator 13 provided for the main circuit breaker unit 10 and also to a tripping operation device 14 provided for the auxiliary circuit breaker unit 11. The tripping signal generator 13 generates a first tripping signal in response to a tripping instruction given through the conductor l2, and the first tripping signal is transferred to the main circuit breaker unit through a signaltransferring means 15. In view of problems involved in proving insulation between the main circuit breaker unit 10 placed at high potential and the tripping signal generator 13 placed at low potential, a photo signal may be employed as'the signal-transferring means 15. Where a photo signal is employed as the signaltransferring means 15,.a luminescence diode maybe provided on the tripping signal generator 13 so as to transfer a photo signal through a light-conducting bar, and a photo-electrical conversion element is provided at the remote end of the light-conducting bar, said remote end being on the side of the main circuit breaker unit 10. On the other hand where the high speed transferring of the signal is not so critical in practice, the signaltransferring means could, of course, be of a mechanical arrangement 15 which may assume the form of an operating rod. Such a mechanical arrangement is in the instant embodiment employed for the tripping construction of the auxiliary circuit breaker unit 11. The tripping operation device 14 maybe constructed as an electromagnetic valve for instance, and an operating pipe 16 or an operating rod is inserted between the auxiliary circuit breaker unit 11 placed at high potential and the tripping operation device 14 placed at low potential. In addition, an exciting coil 141 is provided for the tripping operation device 14 constructed as the electromagnetic valve.

It is desirable to provide a control device 17 installed on the main circuit breaker unit 10. According to the present invention, it is preferable to provide the control device 17 at high'potential region of the main circuit breaker unit 10, but it may be alternatively be placed at low potential regions. A current transformer 18 is arranged in series with the main circuit breaker unit 10 so as to detect a system current, and a secondary current of the current transformer 18 is fed as a control input to the control device 17. Furthermore, a voltage element (not shown) of the system may be employed as means for supplying input of the control device 17.

It is most expedient to construct the control device 17 as an electronic device, but the control device 17 can be made as a pneumatic pressure type control device, a fluid operation type control device or a device obtained by properly combining the former types.

Referring now to FIG. 2, shown is an embodiment of the control device 17 constructed as an electronic device. A photoelectrical conversion element 20 is adapted to convert a photo signal, which is a tripping signal produced from the tripping signal generator 13 (FIG 1), into an electrical signal, and this electrical output is applied through a transformer 21 and a resistor 22 to the gate circuit of a thyristor 23, or applied between the gate terminal and the cathode. An impedance element 24 for protection is connected between the gate and the cathode of the thyristor 23.

A resistor 25 is connected as a load to a secondary winding 182 of the current transformer 18 shown in FIG. 1; and a limit element 26 which serves to break over at a given voltage or higher, is connected, as an over-voltage protection means, in parallel with the resistor 25. Both terminals of the limit element 26, or of the resistor 25 or the secondary winding 182 are connected to a.c. terminals of a rectifier circuit 27. A protective high resistor 29 and a capacitor 28, which are connected in parallel with each other, are connected to the d.c. terminals of the rectifier circuit 27. The positive d.c. terminal of the rectifier circuit 27 is further connected to the anode of the thyristor 23 through a limit element 30 and an operating coil 31 which are connected in series between said terminal and said anode. The operating coil 31 is provided for feedinga tripping signal to the main circuit breaker unit 10 (FIG. 1). On the other hand, the negative d.c. terminal of the rectifier circuit 27 is connected to the cathode of the tyristor 23. The limit element 30 is selectively chosen so that its break-over voltage be lower than that of the limit element 26. The operating coil is placed so as to be opposite to a movable contact of the main circuit breaker unit.

A circuit 32 for maintaining a conductive condition is connected between the anode and cathode of the thyristor 23. The circuit 32 is composed of two circuits: one is formed by connecting in series a resistor 321, a diode 322 and a capacitor 323, and the other is formed by connecting in series a dc. source 324 and a resistor 325, the latter circuit being connected across a capacitor 323.

Now, the current transformer 18 serves to feed the resistor 25 with a secondary current corresponding to magnitude of a load current of the circuit breaker device; as a result a terminal voltage corresponding to the magnitude of the load current is produced across the resistor 25. In this case, the limit element 26 is useful as an over-voltage protection element when a large current flows due to a fault. The tenninal voltage across the resistor 25 is rectified through the rectifier circuit 27, and the thus rectified voltage is used for charging the capacitor 28.

A tripping signal transferred, by means of light, from the tripping signal generator 13 is coverted into an electrical signal by the photo-electrical conversion element 20 thereby to trigger the thyristor 23. At this time, if the capacitor 28 is charged to a value higher than a predetermined value, the breakover operation of the limit element is effected, and the charge of the capacitor 28 is discharged through the limit element 30, the operating coil 31 and then the thyristor 23, thereby to open the main circuit breaker unit 10. The operating coil 31 may drive the main circuit breaker unit 10 directly, or may drive it indirectly in such a manner that an output obtained through operation of a proper electrical or mechanical amplifier means is utilized to obtain sufficient energy to drive the main circuit breaker unit. However, the former method of driving the main circuit breaker unit directly is quick in operational speed, while the latter method of driving it indirectly is ranked next in operational efficiency, but the latter method may have other advantages.

As apparent from the above description, when the load current flowing through the current transformer 18 becomes abnormal in value, the charge voltage of the capacitor 28 reaches a value over the break-over voltage of the limit element 30, whereby the main circuit breaker unit is made to start its circuit-breaking operation. A second thyristor (not shown), which becomes conductive at a phase angle slightly before a zero point of the load current, may be inserted in series with the thyristor 23 in order to make easier the break ing operation of the main circit breaker unit 10, thereby to construct a circuit breaker unit which effects a circuit-breaking operation is synchronization with load current at all times.

In the case when the load current is lower than a predetermined value, the charge voltage of the capacitor 28 becomes lower than the break-over voltage of the limitelement 30. As a result, even if the thyristor 23 becomes conductive by receiving a tripping signal, the limit element 30 blocks discharge of the capacitor 28. Therefore, no current flows through the operating coil 31, so that the main circuit breaker unit 10 is not operated at all. In this case, accordingly, only the auxiliary circuit breaker unit 11 is operated so as to interrupt the load current.

Once the thyristor 23 has become conductive, the conductive condition maintaining circuit 32 acts so as to maintain the conductive condition for a certain period of time. In this cirucit 32, value of the resistor 325 is selected to be lower than the holding current of the thyristor 23, and the conductive condition holding time of the thyristor 23 is determined by the capacitor 323 and the resistor 321. v

This circuit is provided so that the main circuit breaker unit 10 can immediately perform its circuitbreaking operation in the case when a path of a fault current is varied with operation of another circuit breaker even if there is hardly present a system current when a tripping instruction is issued, or in the case when a large current flows during opening-operation of only the auxiliary circuit breaker unit 11 for instance, in the case when a fault occurs during the openingoperation of the auxi'iary circuit breaker. The conductive condition holding time of the thyristor 23 may be less than several cycles. However, such a circuit can be, of course, eliminated if the thyristor 23 is provided with a means which triggers the thyristor 23 every proper time interval.

In the above-described device, the main circuit breaker unit 10 performs its circuit-breaking operation only when an abnormal load current exceeding a predetermined value flows; only the auxiliary circuit breaker unit 11 operates and the main circuit breaker unit does not operate when the load current is lower than said predetermined value. This makes it possible to provide a reasonable and economical design or arrangement of the main circuit breaker unit 10 and especially to design a circuit breaker device capable of carrying out switching operations of a repetitive nature within a given period of time. Furthermore, the number of times the main circuit breaker unit 10 trips is reduced, and therefore the noise caused by the circuitbreaking operation can be reduced correspondingly.

In order to construct a main circuit breaker unit 10 which operates at a high speed, explosion energy of an explosive can be utilized instead of the abovementioned electromagnetic repulsion force. In this case, as shown in FIG. 3, the operating coil 31 is constructed as an ignition coil 312 provided with terminals which are connected-so as to be switched over by a change-over switch 311 so that an electrical detonator is selected and ignited by the control device (shown in FIG. 2). 1

With reference to FIG. 4, there is shown an electrical detonator ignited by the ignition coil 312. FIG. 4 relates to a case where a plurality of the electrical detonator sections are provided in parallel. Of course, the detonator sections may be provided so that the electrical detonators are automatically replaced after every operation. However, the electrical detonator section of simple construction will be described herein, referring to FIG. 4.

A detonator cylinder 44 has an I-I-shaped section. An electrical detonator 45 associated with the ignition coil 312 and continuing an explosive is mounted on one side of a center partition wall 441 of the cylinder 44 by means of a mounting piece 46. Reference symbol 313 is a lead connected to the ignition coil 312. An explosive which will be exploded secondarily by explosion of the explosive contained in the detonator 45 or an expansion material which will considerably expand in volume by combustion, is filled in a pressure chamber 42 surrounded by both the partition wall 441 and the electrical detonator 45,forming a V-shape in section. A thin portion 47 is formed on a peripheral portion of the partition wall 441. The thin portion 47 is fractured cut and opened by explosion of the electrical detonator 45 as explained later. The electrical detonator device is secured in a high-pressure tube 49 with the aid of a threaded member 48. A high-pressure chamber 50 is formed in the state of penetrating through the center part of a high-pressure tube 49. As soon as the thin portion 47 of the detonator cylinder 44 is cut and opened due to explosion of the electrical detonator 45, communication between the high-pressure chamber 50 and the pressure chamber 42 is established, whereby the pressure in the high-pressure chamber 50 is abruptly brought to a high-pressure. A compression spring 51 is interposed between the partition wall 441 and the highpressure tube 49 so that the thus cut and opened portion of the detonator cylinder is restored back to its initial or original state.

The electrical detonator 45 causes explosion when an electric current is fed to the ignition coil through the connecting lead 313, as a result of which the detonator cylinder 44 is cut at the thin portion 47 by explosive of the pressure created in the filled material. The detonator 45 further continues combustion with consequent increase of pressure inside the high-pressure chamber 50. The high-pressure chamber 50 communicates with an explosive-pressure-introducing tube 62 of the main circuit breaker unit shown in FIG. 5.

An exemplary construction of the main circuit breaker unit 10 driven by explosion of the electric detonator of FIG. 4 is shown in FIG. 5,-in which a movable contact means 54 is disposed opposite to a stationary contact means 53, both contact means 53 and 54 being made in the form of a nozzle. These nozzle-shaped contact means 53 and 54 are hermetically in contact with each other through a nozzle packing 55 when they are closed, and the contact portions of these contact means are positioned inside a high-pressure chamber 561 formed in a high'pressure gas tank 56. An electrically conductive contact means 57 having a slidable contact portion is arranged on the side wall of the movable contact means 54. A return spring 58 acts to push the movable contact means 54 towards the stationary contact means 53. An exhaust tank 59 forms an exhaust gas chamber 591 communicating with a nozzle chamber of the movable contact means 54. The exhaust gas chamber 591 and a return spring chamber 581 containing therein a return spring 58 are communicated with each other through a passage 582. An exhaust tube 61, and a detection tube 60 adapted to detect a circuitbreaking action are connected to the exhaust gas chamber 591 formed by the exhaust tank 59.

The explosive-pressure-introducing tube 62 communicated with the high-pressure chamber 50 of FIG. 4 is further communicated with a pressure chamber 64. The pressure chamber 64 is provided so as to permit the movable contact means 54 to conduct an circuit breaking operation against the elastic force of the return spring 58 in the case when the pressure inside the pressure chamber 64 is increased.

When the electrical detonator 45 shown in FIG. 4 is exploded upon receiving a tripping signal, the pressure in the high-pressure chamber 50 becomes abruptly high and this high pressure thus created is introduced into the pressure chamber 64. Therefore, the movable contact means 54 is moved right, leaving from the stationary contact means 53, as a result of which a highpressure gas filled in the high-pressure gas chamber 561 is blown through the nozzles of both contact means thereby to quench arcs and to interrupt the flow of an electric current. The thus blown high-pressure gas is once stored in the exhaust gas chamber 591 through the inside of the movable contact means 54 and is then exhausted gradually out to the atmosphere. The return spring chamber 581 is gradually filled with a gas by the pressure in the exhaust gas chamber until the conditions, shown in FIG. 5, of the main circuit breaker unit are restored by the action of the return spring 58 after a certain period of time. Usually, several tens mS is-sufficient as the period of time required for restoring said conditions, though said time has a relation to the operating period of time of the auxiliary circuit breaker unit 11. The main circuit breaker unit starts its operation again after the pressure in the exhaust gas chamber 591 is restored back to its original pressure.

The gas inside the high-pressure chamber 50 shown in FIG. 4 is gradually exhausted, whereby the pressure therein becomes equal to that of the atmosphere after a certain period of time. The electrical detonator is constructed so that, when the detonator has been used, the detonator seals, by its explosion, a hold accomdating a connecting lead; and leakage through the hold is substantially of same degree as that found in a closed condition thereof. A portion cut at the thin portion 47 of the electrical detonator cylinder 44 and separated therefrom returns on decrease of pressure in the highpressure chamber 50. The high-pressure chamber 50 is so designed that said chamber 50 can be commonly used for a plurality of the detonator cylinders. The electrical detonator used up is no longer serviceable, and is therefore automatically switched over to the ignition coil of the next electrical detonator by means of the change-over switch 31 1 shown in FIG. 3 so as to be ready for an operation in response to the next tripping signal. It goes without saying that the used electrical detonators will be replaced with new ones at an appropriate time. In the electrical detonator shown in FIG. 4, members such as the detonator cylinder 44 to be replaced after its operation are unitarily screwed in a body of the high-pressure tube, so that the members can be readily replaced with new ones.

If, however the electrical detonator is not dependable enough in view of a break-down of the ignition coil or possible failure of the explosive, a plurality of detonators may then be ignited at the same time in order to eliminate any possible tripping failures of the circuit breaker, because the electrical detonator is not expen srve.

The arrangement shown in FIG. 5 is, of course, one of the embodiments according to the present invention. As found in the application to a usual circuit breaker, the arrangement may be designed so that a charge or exhaust valve forming a part of the circuit breaker device is driven by an explosive thereby to achieve the circuit-breaking operation. Thus, it becomes possible to quicken the in speed of operation of the whole circuit-breaking mechanism or the operation of a part of the circuit-breaking mechanism.

With reference now to FIG. 3, an embodiment of the change-over switch 311 will be explained. The pressure of the exhaust gas chamber 591 (FIG. 5) can be utilized for the switching operation of the change-over switch 311. The pressure inside the exhaust gas chamber 591 begins to increase at the time (t=0) when the operation of the movable contact means 54 starts, and the pressure then gradually lowers after having reached a predetermined value thereof. If a mechanism capable of being rotated by a predetermined angle for one operation in accordance with the pressure variation mentioned above can be obtained, an electrical system of the electrical detonators can be automatically switched over, every operation of the detonator, with provision of a switching contact at every rotary angle predetermined, as found in the well known rotary type switch.

FIG. 6 illustrates such a mechanism adapted to drive the changeover switch mentioned above. The pressure in the exhaust gas chamber 591 is introduced to a pressure-introducing hole 651 of a cylinder 65 through the detection tube 60, and the pressure thus introduced pushes a piston 66 left in FIG. 6, as a result of which a rotary plate 67 with steps is rotated clockwise by one step with the aid of a piston rod 661, and there the rotary plate 67 is retained by means of a stopper 68 at a position advanced by one step, even if the pressure in the exhaust gas chamber 591 is reduced, whereby the piston 66 is returned back to the right side by means of a return spring 69. Though the position of the stopper 68 is varied in a radial direction with rotation of the rotary plate 67, the variation thus caused is compensatively adjusted by action of a spring loaded in the stopper 68. A spring 662 provided at a portion where the driving piston engages with the rotary plate 67 has the same function as the spring 681. A restraint piece 70 constantly provides a biasing force to rotate the rotary plate counterclockwise with the aid of the resilient force of a pulling spring 70, as a result of which the rotary plate 67 maintains itself stably at a position where the stopper 68 imparts force to the rotary plate. Thus, the change-over switch drive mechanism shown in FIG. 6 renders it possible to rotate the roatary plate 67 by the predetermined angle at one operation of the main circuit breaker unit. If the well known rotary type switching mechanism having electrical contact at every rotary angle predetermined is arranged on a shaft 72 of the rotary plate 67, it will be able to change over the ignition coils 312 shown in H6. 3. FIGS. 3 and 6 show the switching mechanism in which the number of the change-over operations is nine, but the number of the change-over operations can be considerably increased by increasing the number of the positions where rotation of the rotary plate is stopped, or by use, in combination, the two switching mechanisms or more.

.In the circuit breaker according to the present invention, if there is no load current present, the main circuit breaker unit 10 cannot be operated. Therefore, if test terminals are is provided on the secondary side of the current transformer 18 shown in FIGS. 1 and 2 and then a current is fed to the testing terminals from a external power sourse, the test operation of the main circuit breaker unit can be conducted with a tripping signal, thereby to check the operational condition of said main circuit breaker unit.

It is preferable to carryout high speed driving of the circuit breaker by using an explosive, because said driving system is low in expense; but the explosive means used once, is no longer servicable as stated previously and this must be borne in mindwhile designing circuit breaker arrangements. However, in view of the use of the power circuit breaker in an extra-high voltage system, it can be said that number of circuit-interruptions due to faults is very small and, the circuit breaker should be operated at a super-high speed only when the circuit-breaking operation is required to isolate any faults. Accordingly, it is advantageous to construct the circuit breaker device by series-connecting both the main circuit breaker unit used for the circuit-breaking operation due to faults and the auxiliary circuit breaker unit used for interrupting a load current. Furthermore, the above-mentioned circuit breaker device which employs the explosive driving system for the main circuit breaker unit is arranged so as to operate only when a large current flows due to circuit faults, as explain-ed previously. When a fault current is not present, or when the current is of the order of the rated current of the system, the circuit-interrupting operation is conducted by the auxiliary circuit breaker unit only. As a result, the average frequency of operation of the main circuit breaker unit can be made once a year, and reliable operation can be ensured if the explosives for approximately ten circuit-breaking operations are loaded in circuit breaker unit and they are used after being switched over through the switching operation mentioned previously. Therefore, it is possible according to the present invention, to provide the circuit breaker device low in cost which can operate at a super-high speed.

It is intended that all matter contained in the foregoing description and in the drawings shall be interpreted as illustrative only not as limitative of the present invention.

We claim:

1. A circuit interrupting apparatus comprising a main circuit breaker unit having a tripping means for tripping the main circuit breaker within a first time interval; means associated with the main circuit breaker to receive a tripping command signal and produce a tripping signal; a tripping control means associated with the main circuit breaker for effecting tripping of the main breaker only when said tripping signal and a current through the main circuit breaker in excess of a predetermined limit are simultaneously present; an auxiliary circuit breaker unit having an inherent tripping time longer than said first time interval, said auxiliary circuit breaker having a tripping device for tripping the auxiliary circuit breaker independent of said main circuit breaker unit, said auxiliary circuit breaker unit being connected electrically in series with the main circuit breaker, whereby the main circuit breaker limitatively performs circuit breaking operation when fast circuit interruptions are required, and the auxiliary circuit breaker unit performs slower circuit trippings under control of said tripping device.

2. An apparatus as claimed in claim 1 wherein said tripping device of the auxiliary circuit breaker unit is. connected to receive said tripping command signal.

3. An apparatus as claimed inclaim 2 wherein said tripping signal is in the form of a light beam, and

' wherein the tripping control means is a control device including a light sen-sitive element which produces a signal output.

4, An apparatus as claimed in claim 3, wherein said control device includes a tripping element and an SCR the gate of which is connected to said signal output, said tripping element being connected to be actuated by a current representative of a current through the main circuit breaker.

5. An apparatus as claimed in claim 4, wherein a limiting diode is provided in series with said tripping element, whereby said tripping element activates the main circuit breaker unit only when said SCR conducts and, the voltage across said limiting diode is in excess of a predetermined limit.

6. A circuit interrupting apparatus as claimed in claim 1 which further includes explosive means to activate tripping of the main circuit breaker.

7. A circuit interrupting apparatus comprising: a main circuit breaker unit having explosive means to activate tripping of the main circuit breaker, said main circuit breaker being provided with a tripping means activated by said explosive means for tripping the main circuit breaker within a first time interval; means associated with the main circuit breaker to receive a tripping command signal and produce a tripping signal to initiate said tripping means; a tripping control means associated with the main circuit breaker for effecting tripping of the main circuit breaker only when said tripping signal and a current through the main circuit breaker in excess of a predetermined limit are simultaneously present; an auxiliary circuit breaker unit having an inherent tripping time longer than said first time interval, said auxiliary circuit breaker having a tripping device for tripping the auxiliary circuit breaker independent of said main circuit breaker unit, said auxiliary circuit breaker unit being connected electrically in series with the main circuit breaker, whereby the main circuit breaker limitatively performs circuit breaking operation when fast circuit interruptions are required, and the auxiliary circuit breaker unit performs slower circuit trippings under control of said tripping device.

8. An apparatus as claimed in claim 7, wherein said tripping device of the auxiliary circuit breaker unit is connected to receive said tripping command signal.

9. An apparatus as claimed in claim 8, wherein said tripping signal is in the form of a light beam, and

which is in excess of a predetermined limit and representative of the main circuit breaker-current, the gate of said SCR being connected to be con-trolled by said signal output.

Claims

1. A circuit interrupting apparatus comprising a main circuit breaker unit having a tripping means for tripping the main circuit breaker within a first time interval; means associated with the maiN circuit breaker to receive a tripping command signal and produce a tripping signal; a tripping control means associated with the main circuit breaker for effecting tripping of the main circuit breaker only when said tripping signal and a current through the main circuit breaker in excess of a predetermined limit are simultaneously present; an auxiliary circuit breaker unit having an inherent tripping time longer than said first time interval, said auxiliary circuit breaker having a tripping device for tripping the auxiliary circuit breaker independent of said main circuit breaker unit, said auxiliary circuit breaker unit being connected electrically in series with the main circuit breaker, whereby the main circuit breaker limitatively performs circuit breaking operation when fast circuit interruptions are required, and the auxiliary circuit breaker unit performs slower circuit trippings under control of said tripping device.

2. An apparatus as claimed in claim 1 wherein said tripping device of the auxiliary circuit breaker unit is connected to receive said tripping command signal.

3. An apparatus as claimed in claim 2 wherein said tripping signal is in the form of a light beam, and wherein the tripping control means is a control device including a light sensitive element which produces a signal output.

4. An apparatus as claimed in claim 3, wherein said control device includes a tripping element and an SCR the gate of which is connected to said signal output, said tripping element being connected to be actuated by a current representative of a current through the main circuit breaker.

9. An apparatus as claimed in claim 8, wherein said tripping signal is in the form of a light beam, and wherein the tripping control means is a control device including a light sensitive element which produces a signal output.

10. An apparatus as claimed in claim 8, wherein said control device includes a tripping element, an SCR and a limiting diode connected in series to receive a current which is in excess of a predetermined limit and representative of the main circuit breaker-Current, the gate of said SCR being connected to be controlled by said signal output.