DC circuit breaker and circuit breaker method

Abstract

To realize a DC circuit breaker that properly interrupts the current when a large current flows and needs to be interrupted.SOLUTION: A DC circuit breaker (1) has a series-connected semiconductor switch (2) and a first switch (3), a first voltmeter (7) that measures the voltage on the secondary side of the semiconductor switch, and an ammeter (6) that measures the current flowing through the semiconductor switch, and the semiconductor switch is turned off when the first voltmeter detects a voltage below a predetermined value until after a predetermined time has passed since the ammeter detected a predetermined current value or higher.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In DC power transmission, when an accident such as a short circuit occurs, the current will continue to increase monotonically. When a short-circuit current flows, the current is interrupted by a circuit breaker. However, in order to prevent the circuit breaker from accidentally interrupting due to the inrush current, the responsiveness is moderately delayed. Therefore, the circuit breaker allows the short-circuit current to flow for a certain period of time, and secondary failures may occur.

[0003] In addition, depending on the magnitude of the short-circuit current, the contacts of the circuit breaker may weld together, and it may not be possible to open the contacts and provide protection. Patent Document 1 discloses a circuit breaker in which a semiconductor switch and a mechanical switch are connected in series, and a current limiter is connected in parallel to the semiconductor switch. By turning off the semiconductor switch in advance, the short-circuit current is reduced to the opening and closing capacity of the mechanical switch.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, since the mechanical switch actually interrupts the short-circuit current, the risk of contact welding remains. In addition, since the current is interrupted by a mechanical switch, the responsiveness is slow.

[0006] One aspect of the present invention aims to realize a DC circuit breaker that appropriately interrupts the current when interruption is required when a large current flows.

Means for Solving the Problems

[0007] To solve the above problems, a DC circuit breaker according to one aspect of the present invention is a DC circuit breaker applied to a DC power transmission system, comprising: a semiconductor switch; a first voltmeter for measuring the secondary voltage of the semiconductor switch; an ammeter for measuring the current flowing through the semiconductor switch; and a control unit for turning off the semiconductor switch when predetermined conditions are met, wherein the predetermined conditions include, as a first condition, that the secondary voltage remains below a predetermined voltage value from the time the current becomes equal to or greater than a predetermined first current value until a predetermined first time has elapsed.

[0008] To solve the above problems, a method for tripping a DC circuit breaker according to another aspect of the present invention is a method for tripping a DC circuit breaker applied to a DC power transmission system, wherein the DC circuit breaker includes a semiconductor switch, and the method includes the steps of: measuring the secondary voltage of the semiconductor switch; measuring the current flowing through the semiconductor switch; and turning off the semiconductor switch when predetermined conditions are met, the first condition being that the secondary voltage remains below a predetermined voltage value from the time the current becomes equal to or greater than a predetermined first current value until a predetermined first time has elapsed. [Effects of the Invention]

[0009] According to one aspect of the present invention, when a large current flows and interruption is necessary, the current can be appropriately interrupted. [Brief explanation of the drawing]

[0010] [Figure 1] This is an electrical circuit diagram of a DC circuit breaker according to Embodiment 1. [Figure 2] This flowchart shows an example of the operation of DC circuit breaker 1 when energized. [Figure 3] This flowchart shows an example of the operation of DC circuit breaker 1 when it trips. [Figure 4] This is a graph of current and voltage when a short-circuit current flows. [Figure 5]This is a graph of current and voltage when an inrush current flows. [Figure 6] This graph shows the current and voltage when the load is released by user operation immediately after the load is applied. [Figure 7] This is an electrical circuit diagram of a DC circuit breaker according to Embodiment 2. [Modes for carrying out the invention]

[0011] [Embodiment 1] Hereinafter, one embodiment of the present invention will be described in detail with reference to Figures 1 to 6.

[0012] (Configuration of DC circuit breaker 1) Figure 1 is an electrical circuit diagram of a DC circuit breaker 1 according to Embodiment 1. The DC circuit breaker 1 is a circuit breaker inserted between DC circuits to interrupt the current. The DC circuit breaker 1 comprises a semiconductor switch 2, a first switch 3, a second switch 4, an overvoltage suppression circuit 5, an ammeter 6, a first voltmeter 7, a second voltmeter 8, and a control unit 9.

[0013] In the DC circuit breaker 1, the semiconductor switch 2 and the first switch 3 are connected in series in that order between the positive terminal of the primary side and the positive terminal of the secondary side. In addition, the second switch 4 is connected between the negative terminal of the primary side and the negative terminal of the secondary side.

[0014] The semiconductor switch 2 is a semiconductor switch, and is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), FET (Field Effect Transistor), or IGBT (Insulated Gate Bipolar Transistor). A diode may be connected in parallel to the semiconductor switch 2 in reverse polarity. The first switch 3 and the second switch 4 are mechanical switches, and are relays or electromagnetic contactors.

[0015] An overvoltage suppression circuit 5 is connected in parallel to the semiconductor switch 2. The overvoltage suppression circuit 5 is a circuit that suppresses the overvoltage applied to the semiconductor switch 2. Examples include a snubber circuit, an RC circuit, or a surge absorber.

[0016] An ammeter 6 is arranged between the primary side positive electrode and the secondary side positive electrode, and can measure the current flowing through the circuit. The ammeter 6 can take any form such as a resistance detection type or a magnetic field detection type sensor. Also, the ammeter 6 is not limited to measuring the current at the positive electrode and may measure the current at the negative electrode.

[0017] The first voltmeter 7 is a sensor that measures the potential difference (secondary side voltage of the semiconductor switch) between the potential of the primary side negative electrode and the potential between the semiconductor switch 2 and the first switch 3. Also, the second voltmeter 8 is a sensor that measures the potential difference (primary side voltage of the semiconductor switch) between the potential of the primary side negative electrode and the potential of the primary side positive electrode. The first voltmeter 7 and the second voltmeter 8 may be any voltage sensors.

[0018] The control unit 9 comprehensively controls each part of the DC circuit breaker 得る事態であるため、意図的に応答性を遅らせている。そのため、遮断器が動作する段階では、十分に短絡電流の電流値が上昇しており、接点が溶着する可能性がある。1. Specifically, based on the respective measurement values by the ammeter 6, the first voltmeter 7, and the second voltmeter 8, the semiconductor switch 2, the first switch 3, and the second switch 4 are controlled.

[0019] (When a short-circuit current occurs) Prior to the description of the operation example, first, the behavior of current and voltage in the case of a short-circuit accident is sorted out. When a short-circuit accident occurs, the current increases monotonically and the voltage instantaneously drops to 0V.

[0020] Generally, a circuit breaker does not immediately start interruption when a predetermined current value is detected, but starts interruption with a certain delay. This is because a large current may flow not only in the case of a short-circuit current but also in the case of an inrush current, so the responsiveness is intentionally delayed. Therefore, at the stage when the circuit breaker operates, the current value of the short-circuit current has risen sufficiently, and there is a possibility that the contacts will weld.

[0021] (Operation of DC circuit breaker 1) Next, we will explain the operation of DC circuit breaker 1 and demonstrate that DC circuit breaker 1 can properly interrupt short-circuit current.

[0022] Figure 2 is a flowchart showing an example of the operation of DC circuit breaker 1 when energized.

[0023] (Checking the status of semiconductor switch 2) First, before current flows from the primary side to the secondary side, it is determined whether the semiconductor switch 2 is functioning correctly. This ensures that the short-circuit current can be properly interrupted in the event of a short-circuit fault.

[0024] The control unit 9 turns off the semiconductor switch 2 (S101). Then, the control unit 9 opens the first switch 3 and the second switch 4 (S102). The first voltmeter 7 measures the voltage on the secondary side of the semiconductor switch 2 as the first voltage value, and the second voltmeter 8 measures the voltage on the primary side of the semiconductor switch 2 as the second voltage value (S103). The first voltmeter 7 and the second voltmeter 8 output the measured first and second voltage values ​​to the control unit 9, respectively.

[0025] The control unit 9 determines whether the absolute value of the potential difference between the first voltage value and the second voltage value is less than or equal to a predetermined value (S104). If the answer in S104 is Yes, the control unit 9 determines that the semiconductor switch 2 has a short-circuit failure (S105). If the answer in S104 is No, the process proceeds to S106.

[0026] The control unit 9 turns on the semiconductor switch 2 (S106). The first voltmeter 7 measures the voltage on the secondary side of the semiconductor switch 2 as the first voltage value, and the second voltmeter 8 measures the voltage on the primary side of the semiconductor switch 2 as the second voltage value (S107). The first voltmeter 7 and the second voltmeter 8 output the measured first voltage value and second voltage value, respectively, to the control unit 9.

[0027] The control unit 9 determines whether the absolute value of the potential difference between the first voltage value and the second voltage value is greater than a predetermined value (S108). If the answer in S108 is Yes, the control unit 9 determines that the semiconductor switch 2 has an open circuit failure (S109). If the answer in S108 is No, the process proceeds to S111.

[0028] If the semiconductor switch 2 is short-circuited or open-circuited, the control unit 9 determines that the DC circuit breaker 1 is faulty (S110). Therefore, the DC circuit breaker 1 may be software-locked to prevent power from being supplied to it. The failure of the DC circuit breaker 1 may also be indicated to the user by an LED (Light Emitting Diode) or a buzzer.

[0029] Through the steps S101 to S110 described above, the control unit 9 checks the state of the semiconductor switch 2. Therefore, after confirming that the semiconductor switch 2 is not short-circuited or open-circuited, the power supply of the primary circuit can be connected to the secondary circuit. As a result, the DC current can be interrupted when necessary, resulting in a highly reliable DC circuit breaker 1.

[0030] (Checking the status of the secondary circuit) The following process is a determination process for when power is being supplied from the primary power source to the secondary load. Therefore, this determination process is repeatedly performed as long as power is being supplied.

[0031] The first switch 3 and the second switch 4 are closed (S111). In this case, the semiconductor switch 2 may be turned off once, then the first switch 3 and the second switch 4 may be closed, and then the semiconductor switch 2 may be turned on. This is a measure to reduce the risk of contact welding due to arcs generated when the first switch 3 and the second switch 4 are closed while current is flowing, which can cause chattering, etc.

[0032] The first voltmeter 7 measures the voltage on the secondary side of the semiconductor switch 2 as the first voltage value, and the ammeter 6 measures the current flowing through the semiconductor switch 2 as the current value (S112). The first voltmeter 7 and the ammeter 6 output the measured first voltage value and current value to the control unit 9, respectively.

[0033] The control unit 9 checks whether the current value is equal to or greater than a predetermined first overcurrent setting value I1 (S113). If the answer in S113 is No, the control unit 9 resets the counts for the first duration t1 and the second duration t2, which will be described later (S114). Then, the process returns to S112, and the power supply connected to the primary circuit is kept connected to the secondary circuit.

[0034] If the answer to S113 is Yes, the control unit 9 counts up the first duration t1 and the second duration t2 (S115). The first duration t1 is the duration since the current value became equal to or greater than the predetermined first overcurrent setting value I1. The second duration t2 is the duration from when the current value became equal to or greater than the predetermined first overcurrent setting value I1 until the first voltage value was less than the setting voltage value V1 described later.

[0035] The control unit 9 determines whether the current value is greater than or equal to a predetermined second overcurrent setting value I2 (S116, second condition). If the answer in S116 is Yes, the process proceeds to S118.

[0036] The determination made by the control unit 9 is whether the large current is an inrush current or a short-circuit current, based on whether the large current is greater than the second overcurrent setting value I2. If the secondary circuit is short-circuited, as described above, the current value will continue to increase monotonically, and after a sufficient amount of time has passed, it will exceed the second overcurrent setting value I2 (a value greater than the first overcurrent setting value I1). In contrast, in the case of an inrush current, it is an instantaneous current for charging capacitors, etc., in the secondary circuit, and it is generally known that the current value does not increase monotonically but converges while oscillating. In other words, this process in the control unit 9 is one indicator for determining whether the large current is an inrush current or a short-circuit current. This determination is called the "second overcurrent determination".

[0037] If the answer to S116 is No, then it is determined whether the first duration t1 is equal to or greater than the first setting time T1 (S117). In other words, it is determined whether the state in which the current value is equal to or greater than the first overcurrent setting value I1 continues from the time the current value becomes equal to or greater than the first overcurrent setting value I1 until after the first setting time T1 has elapsed (third condition).

[0038] If the answer in S117 is Yes, the process proceeds to S118. If the answer in S118 is No, the process returns to S112. After that, the process returns to S112, and the power supply connected to the primary circuit is kept connected to the secondary circuit.

[0039] The determination made by the control unit 9 is a process that determines how long a large current is continuing. If the secondary circuit is not short-circuited, a large current will flow due to inrush current, but this inrush current will only continue until the capacitors and other components of the secondary circuit are charged, and will not last long. On the other hand, if the secondary circuit is short-circuited, a short-circuit current will flow, and the large current will continue until the current is interrupted. In other words, this process in the control unit 9 is one indicator for determining whether the large current is an inrush current or a short-circuit current. This determination is called the "first overcurrent determination".

[0040] Next, it is determined whether the first voltage value is less than the set voltage value V1 (S118). In other words, it is determined whether the state in which the first voltage value remains less than the set voltage value V1 continues from the time when the current value becomes equal to or greater than the first overcurrent set value I1 until after the first set time T1 has elapsed (first condition).

[0041] If the answer to S118 is No, the control unit 9 resets the count for the second duration t2 (S119). Then, the process returns to S112, and the power supply connected to the primary circuit is kept connected to the secondary circuit. Conversely, if the answer to S118 is Yes, the process proceeds to S120.

[0042] The determination made by the control unit 9 is whether the secondary circuit is short-circuited or not. If the secondary circuit is not short-circuited, a certain voltage will be applied to the first voltage value. However, if the secondary circuit is short-circuited, the first voltage value will be close to 0V. The control unit 9 uses this difference in state to determine the state of the secondary circuit.

[0043] After processing S116 to S118, the control unit 9 determines whether the second duration t2 is greater than or equal to a predetermined second setting time T2 (S120). If the result in S120 is No, the process returns to S112, and the power supply connected to the primary circuit is kept connected to the secondary circuit. Note that the first setting time and the second setting time are arbitrary predetermined values, and there is no restriction on their relative order. Also, steps S116 and S117 may be omitted, and S118 may be processed after S115. Furthermore, either step S116 (second condition) or S117 (third condition) may be omitted. In other words, the first condition is mandatory, while the second and third conditions are optional.

[0044] If the answer to S120 is Yes, the control unit 9 determines that the current flowing through the semiconductor switch 2 is a short-circuit current and that a DC fault has occurred in the secondary circuit (S121). This determination is called the "continued voltage drop determination". In other words, if the first and second conditions are met, or if the first and third conditions are met, the control unit 9 may determine that a DC fault has occurred in the secondary circuit. Alternatively, the determination of the second and third conditions may be omitted, and if the first condition is met, the control unit 9 may determine that a DC fault has occurred in the secondary circuit.

[0045] If the semiconductor switch experiences a short-circuit or open-circuit failure, or if a DC fault occurs in the secondary circuit, the control unit 9 turns off the semiconductor switch (S122). Subsequently, the first switch 3 and the second switch 4 are opened (S123). At this time, the current value may be checked, and the first switch 3 and the second switch 4 may be opened only after it has been determined that the current value is less than a predetermined zero current setting value. This is a measure to prevent contact welding due to arcs generated in the first switch 3 and the second switch 4.

[0046] (Procedure for interrupting the current) Figure 3 is a flowchart showing an example of the operation of DC circuit breaker 1 when it is tripped.

[0047] The control unit 9 turns off the semiconductor switch 2 (S201). Then, the ammeter 6 measures the current flowing through the semiconductor switch 2 as a current value (S202). The ammeter 6 outputs the measured current value to the control unit 9.

[0048] The control unit 9 checks whether the current value is less than a predetermined zero current setting value (S203). If the answer in S203 is No, the process returns to S202 and waits for the current to be completely cut off. If the answer in S203 is Yes, the control unit 9 opens the first switch 3 and the second switch 4 (S204).

[0049] (Time-series changes in current and voltage) Figure 4 shows the graphs of current and voltage when a short-circuit current flows. A short-circuit current flows when a short circuit occurs in the secondary circuit. As mentioned above, the short-circuit current continues to increase monotonically, but in Figure 4, the secondary circuit short-circuits at 0.2 seconds, and the short-circuit current begins to flow. At the same time, the voltage drops to 0V.

[0050] The first duration t1 and the second duration t2 are counted up when the current value exceeds the first overcurrent setting value I1. From time t3, when the first duration t1 exceeds the first setting time T1, the control unit 9 determines that a first overcurrent has occurred. Furthermore, from time t4, when the current value exceeds the second overcurrent setting value I2, the control unit 9 determines that a second overcurrent has occurred. In addition, from time t5, when the second duration t2 exceeds the second setting time T2, the control unit 9 determines that a voltage drop continues.

[0051] The control unit 9 determines that the secondary circuit is short-circuited by detecting a continued voltage drop and initiates the tripping operation of the DC circuit breaker 1 (however, Figure 4 shows the case where no tripping operation is performed).

[0052] Figure 5 shows a graph of current and voltage when an inrush current flows. When an inrush current flows, the current and voltage oscillate due to the RC circuit in the secondary circuit. Figure 5 is also an enlarged view of a part of this oscillation between current and voltage.

[0053] The determinations regarding the first and second overcurrents in the control unit 9 are the same as those in the case where the secondary circuit is short-circuited. Furthermore, it can be seen that the first voltage value rises as the capacitors and other components of the secondary circuit are charged, and at time t6 it exceeds the set voltage value V1. Therefore, in this case the count for the second duration t2 is reset, and the second duration t2 does not exceed the second set time T2. In other words, the control unit 9 does not make a determination that the voltage drop is continuing, and as a result, the control unit 9 determines that the large current flowing through the DC circuit breaker 1 was an inrush current and does not interrupt the large current.

[0054] Figure 6 shows the graph of current and voltage when the load is released by user operation immediately after the load is applied. The determination regarding the first overcurrent in the control unit 9 is the same as in the case where the secondary circuit is short-circuited as described above. Also, because the first voltage value increased due to the opening of the DC circuit breaker 1, it is greater than or equal to the set voltage value V1 at time t7. Therefore, in this case, the count for the second duration t2 is reset, and the second duration t2 does not exceed the second set time T2.

[0055] Furthermore, Figure 6 shows that the current value drops sharply when the DC circuit breaker 1 is opened. Therefore, since the current value does not exceed the second overcurrent setting value I2, the control unit 9 does not perform a second overcurrent determination.

[0056] [Embodiment 2] Other embodiments of the present invention will be described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0057] Figure 7 is an electrical circuit diagram of a DC circuit breaker 1a according to Embodiment 2. Unlike DC circuit breaker 1, DC circuit breaker 1a includes a first semiconductor switch 2a and a second semiconductor switch 2b instead of semiconductor switch 2. Also, unlike DC circuit breaker 1, DC circuit breaker 1a includes a first overvoltage suppression circuit 5a and a second overvoltage suppression circuit 5b instead of overvoltage suppression circuit 5. Furthermore, the control unit 9a has the same basic function as control unit 9, but when operating semiconductor switch 2, it also operates the first semiconductor switch 2a and the second semiconductor switch 2b.

[0058] The first semiconductor switch 2a and the second semiconductor switch 2b have opposite polarities to each other. Furthermore, diodes are connected in parallel to both the first and second semiconductor switches 2a and 2b, respectively, in the opposite polarity to the first and second semiconductor switches 2a and 2b. As a result, these two diodes have opposite polarities to each other.

[0059] The first overvoltage suppression circuit 5a is connected in parallel to the first semiconductor switch 2a. The second overvoltage suppression circuit 5b is connected in parallel to the second semiconductor switch 2b.

[0060] In the DC circuit breaker 1 according to Embodiment 1, the positive terminal of the DC power supply had to be connected to the primary side positive terminal, and the negative terminal of the DC power supply had to be connected to the secondary side negative terminal. In contrast, in the DC circuit breaker 1a according to Embodiment 2, there are no restrictions on the polarity of the power supply connected to the primary side first terminal and primary side second terminal. That is, the negative terminal of the DC power supply may be connected to the primary side first terminal, in which case it will operate with the opposite polarity to Embodiment 1.

[0061] Since the first semiconductor switch 2a and the second semiconductor switch 2b are connected in series with opposite polarities, when current flows, one semiconductor switch conducts the current and the other diode conducts the current. If the polarity of the connected power supply is reversed, the relationship between the semiconductor switch and the diode that conducts the current is also reversed. In other words, the DC circuit breaker 1a is designed to allow current to flow in both directions.

[0062] [Variation] Embodiments 1 and 2 show a configuration with two switches, designated as the first switch 3 and the second switch 4. However, the system is not limited to this configuration, and a configuration that only interrupts the positive terminal of the power supply is also acceptable. In other words, the system may not include the second switch 4, and the current may be interrupted solely by semiconductor switches 2, 2a, and 2b and the first switch 3.

[0063] Furthermore, in embodiments 1 and 2, the first switch 3 and the second switch 4 are located on the secondary side of the semiconductor switches 2, 2a, and 2b, but the invention is not limited to this. That is, the first switch 3 and the second switch 4 may be located on the primary side of the semiconductor switches 2, 2a, and 2b.

[0064] Furthermore, while the example uses short-circuit current, any other fault current is acceptable.

[0065] 〔summary〕 To solve the above problems, a DC circuit breaker according to one aspect of the present invention is a DC circuit breaker applied to a DC power transmission system, comprising: a semiconductor switch; a first voltmeter for measuring the secondary voltage of the semiconductor switch; an ammeter for measuring the current flowing through the semiconductor switch; and a control unit for turning off the semiconductor switch when predetermined conditions are met, wherein the predetermined conditions include, as a first condition, that the secondary voltage remains below a predetermined voltage value from the time the current becomes equal to or greater than a predetermined first current value until a predetermined first time has elapsed.

[0066] To solve the above problems, a method for tripping a DC circuit breaker according to another aspect of the present invention is a method for tripping a DC circuit breaker applied to a DC power transmission system, wherein the DC circuit breaker includes a semiconductor switch, and the method includes the steps of: measuring the secondary voltage of the semiconductor switch; measuring the current flowing through the semiconductor switch; and turning off the semiconductor switch when predetermined conditions are met, the first condition being that the secondary voltage remains below a predetermined voltage value from the time the current becomes equal to or greater than a predetermined first current value until a predetermined first time has elapsed.

[0067] With the above configuration, by monitoring the voltage value when a large current flows, it is possible to determine whether the large current is a short-circuit current or an inrush current, and the current can be interrupted only if it is a short-circuit current.

[0068] The aforementioned predetermined conditions include, as a second condition, that the current is equal to or greater than a predetermined second current value, and the control unit may determine that the aforementioned predetermined conditions have been met when the first and second conditions are met.

[0069] The second current value may be greater than the first current value.

[0070] With the above configuration, it is possible to detect that the current value of the large current flowing is increasing. Therefore, it can be determined that the large current flowing is a short-circuit current.

[0071] The predetermined conditions include, as a third condition, that the state in which the current remains at or above a predetermined first current value from the time the current becomes at or above a predetermined first current value until a predetermined second time has elapsed, and the control unit may determine that the predetermined conditions have been met when the first condition and the third condition are met.

[0072] Based on the above configuration, it can be seen that the large current flowing is not short-term. Therefore, it can be determined that the large current flowing is a short-circuit current.

[0073] The system may further include a mechanical switch connected in series with the semiconductor switch, and a second voltmeter for measuring the primary voltage of the semiconductor switch.

[0074] With the above configuration, the primary voltage of the semiconductor switch can be further measured, and the state of the semiconductor switch can be determined by combining it with the secondary voltage.

[0075] When the semiconductor switch and the mechanical switch are in the off position, if the absolute value of the potential difference between the primary voltage and the secondary voltage is less than or equal to a predetermined value, the mechanical switch may be prevented from being turned on.

[0076] With the above configuration, it is possible to determine whether the semiconductor switch has a short-circuit failure.

[0077] In a situation where the semiconductor switch is on and the mechanical switch is off, if the absolute value of the potential difference between the primary voltage and the secondary voltage is greater than a predetermined value, the mechanical switch may be prevented from being turned on.

[0078] With the above configuration, it is possible to determine whether the semiconductor switch is experiencing an open circuit failure.

[0079] The mechanical switch may be connected to the secondary side of the first voltmeter.

[0080] With the above configuration, the state of the semiconductor switch can be checked before applying voltage to the mechanical switch.

[0081] The semiconductor switch may include a first semiconductor switch and a second semiconductor switch connected in series with opposite polarities to each other.

[0082] With the above configuration, the polarity of the voltage applied to the DC circuit breaker is not restricted.

[0083] The mechanical switch may be connected to the primary side of the semiconductor switch.

[0084] According to the above configuration, a mechanical switch can be connected to the primary side of the semiconductor switch.

[0085] [Examples of implementation using software] The function of the control unit 9 of the DC circuit breakers 1 and 1a (hereinafter referred to as "device") is a program for causing the device to function as a computer, and can be realized by a program for causing the device to function as a computer.

[0086] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., memory) as hardware for executing the program. By executing the program using this control device and storage device, the functions described in each of the embodiments are realized.

[0087] The above program may be recorded on one or more computer-readable recording media, not temporary ones. These recording media may or may not be provided by the above device. In the latter case, the program may be supplied to the above device via any wired or wireless transmission medium.

[0088] Furthermore, some or all of the functions of the above-mentioned device can also be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as the above-mentioned device is formed is also included in the scope of the present invention. In addition, it is also possible to realize the functions of the above-mentioned device by, for example, a quantum computer.

[0089] [Additional Notes] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of 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 Symbols]

[0090] 1. 1a DC circuit breaker 2. Semiconductor switches 2a First semiconductor switch 2b Second semiconductor switch 3. First switch (mechanical switch) 4. Second switch 5. Overvoltage suppression circuit 5a First overvoltage suppression circuit 5b Second overvoltage suppression circuit 6 Ammeter 7. First Voltmeter 8. Second Voltmeter 9. Control Unit

Claims

1. A DC circuit breaker applied to a DC power transmission system, Semiconductor switches and A first voltmeter for measuring the secondary voltage of the semiconductor switch, An ammeter for measuring the current flowing through the semiconductor switch, The system includes a control unit that turns off the semiconductor switch when a predetermined condition is met, The aforementioned predetermined conditions include, as the first condition, that the secondary voltage remains below a predetermined voltage value from the time the current becomes equal to or greater than a predetermined first current value until a predetermined first time has elapsed. A DC circuit breaker further comprising a mechanical switch connected in series with the semiconductor switch and connected to the secondary side of the first voltmeter.

2. The aforementioned predetermined condition includes, as a second condition, that the current is equal to or greater than a predetermined second current value. The DC circuit breaker according to claim 1, wherein the control unit determines that the predetermined condition is met when the first condition and the second condition are met.

3. The aforementioned predetermined conditions include, as a third condition, that the state in which the current remains at or above a predetermined first current value from the time the current becomes at or above a predetermined first current value until a predetermined second time has elapsed. The DC circuit breaker according to claim 1, wherein the control unit determines that the predetermined conditions have been met when the first condition and the third condition have been met.

4. The DC circuit breaker according to claim 2, wherein the second current value is greater than the first current value.

5. The DC circuit breaker according to claim 1, further comprising a second voltmeter for measuring the primary voltage of the semiconductor switch.

6. A DC circuit breaker applicable to a DC power transmission system, Semiconductor switches and A first voltmeter for measuring the secondary voltage of the semiconductor switch, An ammeter for measuring the current flowing through the semiconductor switch, The system includes a control unit that turns off the semiconductor switch when a predetermined condition is met, The aforementioned predetermined conditions include, as the first condition, that the secondary voltage remains below a predetermined voltage value from the time the current becomes equal to or greater than a predetermined first current value until a predetermined first time has elapsed. A mechanical switch connected in series with the semiconductor switch, The system further comprises a second voltmeter for measuring the primary voltage of the semiconductor switch, A DC circuit breaker that prevents the mechanical switch from being turned on when the semiconductor switch and the mechanical switch are in the off position, and the absolute value of the potential difference between the primary voltage and the secondary voltage is less than or equal to a predetermined value.

7. A DC circuit breaker applicable to a DC power transmission system, Semiconductor switches and A first voltmeter for measuring the secondary voltage of the semiconductor switch, An ammeter for measuring the current flowing through the semiconductor switch, The system includes a control unit that turns off the semiconductor switch when a predetermined condition is met, The aforementioned predetermined conditions include, as the first condition, that the secondary voltage remains below a predetermined voltage value from the time the current becomes equal to or greater than a predetermined first current value until a predetermined first time has elapsed. A mechanical switch connected in series with the semiconductor switch, The system further comprises a second voltmeter for measuring the primary voltage of the semiconductor switch, A DC circuit breaker that prevents the mechanical switch from being turned on when the semiconductor switch is on and the mechanical switch is off, and the absolute value of the potential difference between the primary voltage and the secondary voltage is greater than a predetermined value.

8. A DC circuit breaker applicable to a DC power transmission system, Semiconductor switches and A first voltmeter for measuring the secondary voltage of the semiconductor switch, An ammeter for measuring the current flowing through the semiconductor switch, The system includes a control unit that turns off the semiconductor switch when a predetermined condition is met, The aforementioned predetermined conditions include, as the first condition, that the secondary voltage remains below a predetermined voltage value from the time the current becomes equal to or greater than a predetermined first current value until a predetermined first time has elapsed. A mechanical switch connected in series with the semiconductor switch, The system further comprises a second voltmeter for measuring the primary voltage of the semiconductor switch, The mechanical switch is a DC circuit breaker connected to the secondary side of the first voltmeter.

9. The DC circuit breaker according to any one of claims 1 to 7, wherein the semiconductor switch includes a first semiconductor switch and a second semiconductor switch connected in series with respect to each other and having opposite polarities.

10. A method for tripping a DC circuit breaker applied to a DC power transmission system, The DC circuit breaker is equipped with a semiconductor switch, The steps include measuring the secondary voltage of the semiconductor switch using a first voltmeter, The steps include measuring the current flowing through the semiconductor switch, The process includes the step of turning off the semiconductor switch when a predetermined condition is met, The aforementioned predetermined conditions include, as the first condition, that the secondary voltage remains below a predetermined voltage value from the time the current becomes equal to or greater than a predetermined first current value until a predetermined first time has elapsed. A circuit breaker method comprising a DC circuit breaker further comprising a mechanical switch connected in series with the semiconductor switch and connected to the secondary side of the first voltmeter.

Images