Circuit breaker system

Abstract

To provide a circuit breaker system that reduces the risk of occurrence of the delayed current zero phenomenon.SOLUTION: A circuit breaker system (1) is provided with a transformer (5) including primary winding (8) connected to a power supply (3) and secondary winding (9) connected to a reactor (6). The transformer includes a core (7) including the primary winding and the secondary winding that are wound therearound, and sensors (12, 14) for measuring a current in the primary winding or the secondary winding. A current is applied to the transformer to reduce flux change in the core.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a circuit breaker system.

Background Art

[0002] Patent Document 1 discloses a variable control reactor that controls reactive power by a reactor in a power supply system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, although the prior art as described above can be used for reactive power compensation, when an accident occurs in an AC system, a DC current is generated in the reactor. The DC current attenuates due to the impedance of wires etc. and changes with time series. Therefore, the reactor also allows a DC current to flow from the secondary side to the primary side via, for example, a transformer. Therefore, a current zero miss phenomenon occurs in the circuit breaker provided on the primary side of the transformer, and the reactor hinders the power supply cutoff on the primary side of the transformer.

[0005] One aspect of the present invention aims to realize a circuit breaker system that reduces the occurrence of the current zero miss phenomenon.

Means for Solving the Problems

[0006] To solve the above problems, a circuit breaker system according to an aspect of the present invention is a circuit breaker system including a transformer, the transformer including a primary winding to which a power supply is connected, a secondary winding to which a reactor is connected, a core around which the primary winding and the secondary winding are wound, and a sensor configured to measure a first current in the primary winding or the secondary winding, and including a current supply unit configured to apply a second current to the transformer so as to reduce a change in magnetic flux in the core.

Advantages of the Invention

[0007] According to an aspect of the present invention, the occurrence of a current zero miss phenomenon can be reduced.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated.

[0010] 〔Embodiment 1〕 (Circuit Configuration of Power Supply System 100) FIG. 1 is a circuit diagram showing the configuration of a main part of a power supply system 100 according to Embodiment 1. In the power supply system 100, an AC power supply 3, a circuit breaker 4, a transformer 5, and a reactor 6 are connected in series. That is, the AC power supply 3 and the circuit breaker 4 are connected to the primary winding of the transformer 5. The circuit breaker 4 is provided between the primary winding of the transformer 5 and the AC power supply 3. A reactor 6 is connected to the secondary winding of the transformer 5. The reactor 6 is, for example, a shunt reactor.

[0011] FIG. 2 is a diagram showing details of the connection state of the transformer 5 according to Embodiment 1. As shown in FIG. 2, the transformer 5 includes a core 7, a primary winding 8, a secondary winding 9, and a tertiary winding 10. The primary winding 8, the secondary winding 9, and the tertiary winding 10 are wound around the core 7. The primary winding 8 is connected to the circuit breaker 4. The secondary winding 9 is connected to the reactor 6.

[0012] The circuit breaker system 1 includes the circuit breaker 4, the transformer 5, a variable DC power supply 11 (current supply unit), a first sensor 12, a second sensor 13, a third sensor 14, and a control device 20. The first sensor 12 measures the current flowing through the secondary winding 9. The second sensor 13 measures the current flowing through the tertiary winding 10. The third sensor 14 measures the current flowing through the primary winding 8. As the first sensor 12, the second sensor 13, and the third sensor 14, a CT (Current Transformer) may be used.

[0013] The control device 20 acquires the measured current values from the first sensor 12, the second sensor 13, and the third sensor 14. The control device 20 controls the operations of the circuit breaker 4 and the variable DC power supply 11.

[0014] A variable DC power supply 11 is connected to the tertiary winding 10. The variable DC power supply 11 may be a current amplifier that outputs a DC current commanded by the control device 20. Also, the variable DC power supply 11 may be a device including an oscillator and a DC amplifier that amplifies a signal from the oscillator.

[0015] (Phenomena at the time of an accident) Consider the case where an accident such as a short - circuit accident or a ground - fault accident occurs at the point P on the primary side of the circuit breaker 4. FIG. 3 is a graph showing the magnetic flux generated in the core 7 according to Embodiment 1. The horizontal axis of FIG. 3 represents time, and the vertical axis represents magnetic flux. The solid line indicates the magnetic flux when the circuit breaker system 1 of Embodiment 1 operates. The dashed line indicates the magnetic flux when there is no tertiary winding 10 and variable DC power supply 11.

[0016] Normally, the magnetic flux generated in the transformer 5 changes periodically due to the alternating current input to the primary winding 8. When an accident occurs at time t1, the reactor 6 starts to output a DC current to the secondary winding 9 of the transformer 5 according to the magnetic flux that the reactor 6 held at that time. The DC current gradually decays due to the impedance of the wire itself and the impedance in the circuit. Therefore, the DC current changes in time series, and the magnetic flux generated in the core 7 by the DC current also changes in time series (the dashed line in FIG. 3). Note that the DC current flowing through the secondary winding 9 also changes in the same manner as the dashed line in FIG. 3.

[0017] The transformer 5 has the property of not passing a current such as a constant DC current that does not cause a change in magnetic flux in the core 7. However, since the current output by the reactor 6 and input to the secondary winding 9 is a DC current that changes in time series, it is a current that causes a change in magnetic flux in the core 7. Therefore, when there is no tertiary winding 10 and variable DC power supply 11, a DC current corresponding to the change in magnetic flux is output from the primary winding 8 to the circuit breaker 4.

[0018] FIG. 4 is a graph showing the current input to the circuit breaker 4 according to Embodiment 1 (the current output from the primary winding 8). The horizontal axis in FIG. 4 represents time, and the vertical axis represents current. The solid line indicates the current when the circuit breaker system 1 of Embodiment 1 operates. The dashed line indicates the current when there is no tertiary winding 10 and variable DC power supply 11. As shown by the dashed line in FIG. 4, when there is no tertiary winding 10 and variable DC power supply 11, the DC current output by the reactor 6 and converted by the transformer 5 is input to the circuit breaker 4, so the current flowing through the circuit breaker 4 may not cross zero. Therefore, there may be a case where the circuit breaker 4 cannot interrupt the current.

[0019] (Operation at the time of an accident) Therefore, by inputting a current from the variable DC power supply 11 to the transformer 5 with respect to the tertiary winding 10, the change in the magnetic flux generated in the core 7 is reduced. As a result, the current output from the primary winding 8 to the circuit breaker 4 is reduced. As a result, the circuit breaker 4 can easily interrupt the current.

[0020] Specifically, when the control device 20 detects that an accident has occurred on the primary side of the circuit breaker 4, the control device 20 switches the circuit breaker 4 to the open state (interrupted state). The control device 20 calculates the change in magnetic flux due to the change in the current flowing through the secondary winding 9. The control device 20 inputs a current from the variable DC power supply 11 to the transformer 5 so as to compensate for the change in magnetic flux, that is, to reduce the magnetic flux change.

[0021] That is, as shown by the solid line in FIG. 3, a DC current is input to the tertiary winding 10 of the transformer 5 so that the magnetic flux generated in the core 7 does not change. In response to the change in magnetic flux due to the change in the current in the secondary winding 9, the control device 20 changes the magnitude of the DC current input from the variable DC power supply 11 to the tertiary winding 10 over time. For example, the control device 20 increases the magnitude of the DC current input from the variable DC power supply 11 to the tertiary winding 10 over time so as to compensate for the decrease in magnetic flux. As a result, as shown by the solid line in FIG. 4, the current input to the circuit breaker 4 asymptotically approaches zero, so that the circuit breaker 4 can interrupt the current.

[0022] Note that the control device 20 may calculate the change in magnetic flux based on the current flowing through the tertiary winding 10 generated by the change in magnetic flux during an accident.

[0023] (Tertiary winding 10 during normal operation) Note that during an accident, it is necessary to compensate for the magnetic flux generated in the core 7 by flowing a DC current from the variable DC power supply 11 to the tertiary winding 10, but this is not the case during normal times. In particular, if the tertiary winding 10 and the variable DC power supply 11 are connected during normal times, not only the AC current generated in the secondary winding 9 due to the change in magnetic flux caused by the AC input from the primary winding 8, but also an AC current will be generated in the tertiary winding 10.

[0024] Therefore, a switch (not shown) may be provided between the tertiary winding 10 and the variable DC power supply 11 so that no unintended AC is applied to the variable DC power supply 11, and the switch may be in an open state during normal times. Note that the switch may be a semiconductor switch that can be opened and closed at high speed because it is necessary to operate (switch to the closed state) sufficiently quickly during an accident.

[0025] (Variable DC power supply 11) The power supply of the variable DC power supply 11 may be driven by a battery connected to the primary side or the secondary side of the transformer 5. In this case, the battery may be a battery having a capacity such that the variable DC power supply 11 can output a DC current during the period until the circuit breaker 4 can be interrupted during an accident.

[0026] Also, the power supply of the variable DC power supply 11 may be a power supply of a different system from the primary side and the secondary side of the transformer 5.

[0027] (Number of turns of the tertiary winding 10) The number of turns of the tertiary winding 10 may be larger or smaller than that of the primary winding 8 and the secondary winding 9. When the number of turns of the tertiary winding 10 is large, a sufficient change in magnetic flux can be generated in the core 7 by a small current. However, the man-hours for winding the tertiary winding 10 around the core 7 increase, and the cost increases.

[0028] On the other hand, when the number of turns of the tertiary winding 10 is small, it is necessary to cause a change in magnetic flux in the core 7 by a large current. Instead, the man-hour for winding the tertiary winding 10 around the core 7 is small, and the cost can be suppressed.

[0029] (Modification: Control method) Control was performed to reduce the change in magnetic flux acting on the core 7 by using the current input to the secondary winding 9, but it is not limited to this. For example, the magnetic flux acting on the core 7 may be measured with a Hall sensor or the like and used for control. In this case as well, the current in the secondary winding 9 may be measured with a sensor.

[0030] Also, the current output from the primary winding 8 may be used for control. That is, the circuit breaker system 1 may measure the current output from the primary winding 8 with the third sensor 14 and apply a direct current to the tertiary winding 10 so that this current value becomes zero.

[0031] Therefore, the circuit breaker system 1 may include the first sensor 12 or the third sensor 14 that measures the current in the primary winding 8 or the secondary winding 9. These first sensor 12 or third sensor 14 may be used to detect the occurrence of accidents on the primary side and the secondary side of the transformer 5.

[0032] 〔Embodiment 2〕 Another embodiment of the present invention will be described below. For convenience of explanation, members having the same functions as those described in the above embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

[0033] FIG. 5 is a circuit diagram showing the configuration of the main part of the power supply system 100a according to Embodiment 2. The power supply system 100a is different from the power supply system 100 in that a transformer 5a is provided instead of the transformer 5, and further, a variable DC power supply 11 is connected in parallel to the reactor 6. In the present embodiment, the circuit breaker system 1a includes a transformer 5a, a variable DC power supply 11, a first sensor 12, a third sensor 14, and a control device 20.

[0034] FIG. 6 is a diagram showing details of the connection state of the transformer 5a according to Embodiment 2. As shown in FIG. 6, a primary winding 8 and a secondary winding 9 are wound around the core 7, and it does not have a tertiary winding 10. The primary winding 8 is connected to the circuit breaker 4. Reactors 6 and a variable DC power supply 11, which are connected in parallel with each other, are connected to the secondary winding 9.

[0035] Therefore, at the time of an accident, the current input to the secondary winding 9 of the transformer 5a is the sum of the DC current from the reactor 6 and the DC current from the variable DC power supply 11.

[0036] FIG. 7 is a graph showing the current input to the secondary winding 9 according to Embodiment 2. The horizontal axis in FIG. 7 represents time, and the vertical axis represents current. The dashed line is the DC current input only from the reactor 6, and the solid line is the total DC current input from the reactor 6 and the variable DC power supply 11.

[0037] As shown in FIG. 7, similar to Embodiment 1, the DC current input only from the reactor 6 will decay. The variable DC power supply 11 outputs a DC current to the secondary winding 9 of the transformer 5 so as to compensate for this decayed current. As a result, the magnetic flux in the core 7 becomes almost constant as in FIG. 3. Therefore, the current output from the primary winding 8 to the circuit breaker 4 becomes sufficiently small, and the circuit breaker 4 can cut off the current.

[0038] 〔Embodiment 3〕 Other embodiments of the present invention will be described below. For the sake of convenience of explanation, members having the same functions as those described in the above embodiments are given the same reference numerals, and the description thereof will not be repeated.

[0039] In Embodiments 1 and 2, in order to gradually bring the current output from the primary winding 8 to zero, the change in the magnetic flux generated in the core 7 was reduced. However, depending on the control state, the current may approach zero but not reach zero. In this case, there is a possibility that the current cannot be interrupted. Therefore, in Embodiment 3, after gradually bringing the current to zero, the current is made to cross zero more reliably.

[0040] In Embodiment 3, an AC component is superimposed on the DC current output by the variable DC power supply 11. As a result, the DC current output by the variable DC power supply 11 is a DC current whose amplitude repeatedly increases and decreases. That is, the DC current output by the variable DC power supply 11 oscillates around a non-zero value.

[0041] FIG. 8 is a graph showing the magnetic flux generated in the core 7 according to Embodiment 3. As shown in FIG. 8, in this case, the magnetic flux generated in the core 7 also has an oscillating component.

[0042] FIG. 9 is a graph showing the current input to the circuit breaker 4 (the current output by the primary winding 8) according to Embodiment 3. Since the magnetic flux generated in the core 7 oscillates, the current output by the primary winding also has an oscillating component. As a result, the current output by the primary winding that has gradually approached zero has an opportunity to cross zero. Therefore, the circuit breaker 4 can interrupt the current.

[0043] Note that the amplitude of the superimposed AC component needs to be larger than the current value when approaching zero. This is for causing the current to cross zero.

[0044] 〔Example of Realization by Software〕 The functions of the control device 20 (hereinafter referred to as the "device") are programs for causing a computer to function as the device, and can be realized by programs for causing a computer to function as the device.

[0045] In this case, as hardware for executing the above program, the above device includes a computer having at least one control device (for example, a processor) and at least one storage device (for example, a memory). By executing the above program with this control device and storage device, each function described in the above embodiments is realized.

[0046] The above program may be recorded on one or more computer-readable recording media, rather than temporarily. This recording medium may or may not be provided in the above device. In the latter case, the above program may be supplied to the above device via any wired or wireless transmission medium.

[0047] Also, part or all of the functions of the above control blocks can also be realized by a logic circuit. For example, an integrated circuit in which a logic circuit functioning as each of the above control blocks is formed is also included in the scope of the present invention. In addition to this, for example, it is also possible to realize the functions of the above control blocks by a quantum computer.

[0048] 〔Summary〕 The circuit breaker system according to Aspect 1 of the present invention is a circuit breaker system including a transformer, the transformer including a primary winding to which a power supply is connected, a secondary winding to which a reactor is connected, a core around which the primary winding and the secondary winding are wound, and a sensor for measuring a first current in the primary winding or the secondary winding, and including a current supply unit that supplies a second current to the transformer so as to reduce a change in magnetic flux in the core.

[0049] According to the above configuration, by reducing the change in magnetic flux in the core, the current output from the primary winding can be reduced. Therefore, it becomes possible to easily interrupt the current with a circuit breaker.

[0050] In the circuit breaker system according to Embodiment 2 of the present invention, in the above Embodiment 1, the transformer may include a tertiary winding wound around the core, and the current supply unit may be configured to supply the second current to the tertiary winding.

[0051] According to the above configuration, the change in magnetic flux due to the attenuation of the direct current output from the reactor input to the secondary winding can be compensated by the tertiary winding wound around the core. Therefore, the current can be easily interrupted by the circuit breaker.

[0052] In the circuit breaker system according to Embodiment 3 of the present invention, in the above Embodiment 1, the current supply unit may be configured to supply the second current to the secondary winding.

[0053] According to the above configuration, by applying a current to the secondary winding, the change in magnetic flux can be reduced. Therefore, the current can be easily interrupted by the circuit breaker.

[0054] In the circuit breaker system according to Embodiment 4 of the present invention, in any one of the above Embodiments 1 to 3, the second current may be a direct current.

[0055] According to the above configuration, the second current can be a direct current.

[0056] In the circuit breaker system according to Embodiment 5 of the present invention, in any one of the above Embodiments 1 to 4, the second current may be a direct current whose amplitude repeats increase and decrease.

[0057] According to the above configuration, simply reducing the change in magnetic flux does not necessarily mean that the current output from the primary winding becomes zero. Here, by causing the amplitude of the current for reducing the change in magnetic flux to repeat increase and decrease, the change in magnetic flux can be vibrated. As a result of the change in magnetic flux vibrating, the current output from the primary winding also vibrates, and the current naturally crosses zero.

[0058] The circuit breaker system according to aspect 6 of the present invention includes, in any one of aspects 1 to 5 above, a circuit breaker provided between the power supply and the primary winding, and during a period after the circuit breaker is switched to the open state, the current supply unit may be configured to supply the second current to the transformer so as to reduce a change in magnetic flux in the core.

[0059] According to the above configuration, by supplying the second current to the transformer, it is possible to reduce a change in magnetic flux generated in the core. As a result, it is possible to reduce the direct current output from the primary winding, and the circuit breaker can cut off the direct current.

[0060] The circuit breaker system according to aspect 7 of the present invention includes, in any one of aspects 3 to 6 above, a circuit breaker provided between the power supply and the primary winding, and during a period after the circuit breaker is switched to the open state, the current supply unit may be configured to supply the second current to the secondary winding of the transformer so as to compensate for a decrease in the first current supplied from the reactor to the secondary winding.

[0061] According to the above configuration, by setting the total amount of current flowing through the secondary winding to the first current and the second current, it is possible to make it substantially constant. Therefore, it is possible to reduce the current output from the primary winding, and the circuit breaker can cut off the direct current.

[0062] 〔Supplementary Notes〕 The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Explanation of Reference Numerals

[0063] 1, 1a Circuit breaker system 3 AC power supply 4 Circuit breaker 5, 5a Transformer 6 Reactor 7 Core 8 Primary winding 9 Secondary winding 10 Tertiary winding 11 Variable DC power supply (current supply unit) 12, 13, 14 Sensor 20 Control device 100, 100a Power supply system

Claims

1. A circuit breaker system including a transformer, The transformer is a primary winding to which a power supply is connected; a secondary winding to which a reactor is connected; a core around which the primary winding and the secondary winding are wound; a sensor for measuring a first current in the primary winding or the secondary winding, A circuit breaker system comprising a current supply configured to supply a second current to the transformer to reduce magnetic flux changes in the core.

2. the transformer includes a tertiary winding wound around the core; The circuit breaker system according to claim 1 , wherein the current supply unit supplies the second current to the tertiary winding.

3. The circuit breaker system according to claim 1 , wherein the current supply unit supplies the second current to the secondary winding.

4. The circuit breaker system of claim 1 , wherein the second current is a direct current.

5. The circuit breaker system of claim 1 , wherein the second current is a direct current whose amplitude repeatedly increases and decreases.

6. a circuit breaker provided between the power source and the primary winding; 6. The circuit breaker system according to claim 1, wherein the current supplier supplies the second current to the transformer so as to reduce a magnetic flux change in the core during a period after the circuit breaker is switched to an open state.

7. a circuit breaker provided between the power source and the primary winding; 4. The circuit breaker system according to claim 3, wherein, during a period after the circuit breaker is switched to an open state, the current supply unit supplies the second current to the secondary winding of the transformer so as to compensate for a decrease in the first current supplied from the reactor to the secondary winding.

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