DC circuit breaker

Abstract

The DC circuit breaker (10) comprises a current limiter (11) in which a plurality of current limiting modules (111) are connected in series to interrupt fault currents flowing through the power system and limit them to a current zero point; a residual current circuit breaker (12) that interrupts residual currents that flow after the fault current has been interrupted; and a master control device (13) that controls and monitors the status of the current limiter (11) and the residual current circuit breaker (12). The master control device (13) has a first function of interrupting fault currents by outputting interruption control commands to the current limiting modules (111) and then the residual current circuit breaker (12) in that order, and a second function of outputting closing control commands to the current limiting modules (111) and then the residual current circuit breaker (12) in that order. When the first function is executed, the master control device (13) outputs an interruption control command to the residual current circuit breaker (12) if a preset number or more of the plurality of current limiting modules (111) have successfully interrupted.

Description

Technical Field

[0006] , , , , , ,

[0001] The present disclosure relates to a DC circuit breaker for interrupting DC current.

Background Art

[0002] The development of a DC power transmission system capable of transmitting power generated offshore to remote areas with low loss and low cost is progressing rapidly. In a DC power transmission system, a DC circuit breaker having a function of quickly interrupting the fault current generated by an accident in the power system to prevent the spread and expansion of the accident, as well as a self-protection measure function, is essential.

[0003] A DC circuit breaker is known to have a configuration including a current suppressor (CSD: Current Suppression Device) that interrupts the fault current and limits the current to the current zero point, and a residual current switchgear (RCS: Residual Current Switchgear) that interrupts the residual current flowing after the fault current is interrupted. Further, as a method of interrupting the current suppressor, a mechanical switch, a semiconductor switch using a power semiconductor, and a hybrid switch of a mechanical type and a semiconductor type are known.

[0004] The master control device is responsible for outputting control commands to the current suppressor and the residual current switchgear that make up the DC circuit breaker at an appropriate timing according to the interruption command and the closing command from an upper control device such as a protection relay device and a monitoring and control device. By the master control device, safe interruption and closing of the DC circuit breaker after the accident is removed are realized.

[0005] Patent Document 1 discloses a timing chart showing the operation of a DC circuit breaker having a current suppressor including a mechanical switch, a resonance circuit section including a capacitor, a reactor, and a closing switch that forms a current zero point, and a residual current switchgear.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] However, the DC circuit breaker disclosed in Patent Document 1 does not consider coordinated control for interrupting fault currents using a current limiter, which is a current limiter having a resonant circuit section consisting of a mechanical switch and a power electronics circuit that forms a current zero, connected in series, and a residual current circuit breaker, nor does it consider simultaneous monitoring control to reduce variations in switching operations between current limiting modules. For this reason, the DC circuit breaker disclosed in Patent Document 1 has difficulty in safely interrupting fault currents and safely switching them back on after the fault current has been interrupted.

[0008] This disclosure has been made in view of the above, and aims to provide a DC circuit breaker that can safely interrupt fault current and safely switch back on after the fault current has been interrupted. [Means for solving the problem]

[0009] To solve the above-mentioned problems and achieve the objective, the DC circuit breaker according to this disclosure comprises a current limiter having a plurality of current limiting modules connected in series to interrupt fault currents flowing through the power system and limit them to a current zero point, a residual current circuit breaker that interrupts residual currents that flow after the fault current has been interrupted, and a master control device that controls and monitors the status of the current limiter and the residual current circuit breaker. The master control device has a first function that interrupts fault currents by outputting interruption control commands in the order of current limiting modules and residual current circuit breaker, and a second function that outputs closing control commands in the order of current limiting modules and residual current circuit breaker. When the first function is executed, if a preset number or more of the plurality of current limiting modules successfully interrupt the current, the master control device outputs an interruption control command to the residual current circuit breaker. [Effects of the Invention]

[0010] This disclosure provides the advantage of obtaining a DC circuit breaker that can safely interrupt fault current and safely switch back on after the fault current has been interrupted. [Brief explanation of the drawing]

[0011] [Figure 1] Diagram showing the configuration of a DC circuit breaker according to Embodiment 1 [Figure 2] This figure shows the configuration of the master control device for a DC circuit breaker according to Embodiment 1. [Figure 3] Diagram showing the configuration of the current limiter of the DC circuit breaker according to Embodiment 1. [Figure 4] A flowchart showing the tripping control flow of a DC circuit breaker according to Embodiment 1. [Figure 5] Flowchart showing the flow of closing control for a DC circuit breaker according to Embodiment 1 [Figure 6] Flowchart showing the processing flow for reclosing start lock of a DC circuit breaker according to Embodiment 1 [Figure 7] This figure shows the hardware configuration of the processing unit of the master control device for a DC circuit breaker according to Embodiment 1. [Modes for carrying out the invention]

[0012] A DC circuit breaker according to an embodiment will be described in detail below with reference to the drawings.

[0013] Embodiment 1. Figure 1 shows the configuration of a DC circuit breaker according to Embodiment 1. The DC circuit breaker 10 according to Embodiment 1 includes a current limiter 11 that interrupts the fault current and limits it to the current zero point, a residual current circuit breaker 12 that interrupts the residual current that flows after the fault current is interrupted, and a master control device 13 that controls the current limiter 11 and the residual current circuit breaker 12 based on interruption commands and on-off commands received from a higher-level control device 20. The higher-level control device 20 is a collective term for a group of devices including a protective relay device, a monitoring control device, an emergency stop button, a locally connected operating device, and a remotely connected operating device.

[0014] The DC circuit breaker 10 according to Embodiment 1 is equipped with two master control devices 13, master control devices 13a and 13b, and each of the master control devices 13a and 13b is connected to a higher-level control device 20. In the DC circuit breaker 10 according to Embodiment 1, both master control devices 13a and 13b are redundant as active systems, so even if one of the two master control devices 13a and 13b fails, the system can continue to operate without stopping. In addition, the DC circuit breaker 10 according to Embodiment 1 is connected to two higher-level control devices 20a and 20b. Therefore, the DC circuit breaker 10 according to Embodiment 1 can continue to operate even if one of the two higher-level control devices 20a and 20b fails. Although a configuration in which the master control devices 13a and 13b and the higher-level control devices 20a and 20b are duplicated is given as an example here, the DC circuit breaker 10 may have only one master control device 13, and the DC circuit breaker 10 may have only one higher-level control device 20. In the following explanation, when the master control devices 13a and 13b are to be distinguished, they will be referred to as master control device 13a or master control device 13b; when they are not to be distinguished, they will be referred to as master control device 13. Similarly, when the higher-level control devices 20a and 20b are to be distinguished, they will be referred to as higher-level control device 20a or higher-level control device 20b; when they are not to be distinguished, they will be referred to as higher-level control device 20.

[0015] The current limiter 11 is equipped with multiple current limiting modules 111a, 111b, ..., 111n. In the following description, when distinguishing between current limiting modules 111a, 111b, ..., 111n, they will be referred to as current limiting module 111a, current limiting module 111b, or current limiting module 111n, and when not distinguishing between them, they will be referred to as current limiting module 111. The master control device 13 and the current limiting modules 111 are connected by optical fibers. The master control device 13 and the residual current circuit breaker 12 are connected by metal cables. Although Figure 1 shows a star topology configuration in which each current limiting module 111 is individually connected to the master control device 13, the connection configuration between the current limiting modules 111 and the master control device 13 may also be a ring topology. By using a ring topology for the connection configuration between the current limiting modules 111 and the master control device 13, the total length of the optical fibers connecting the current limiting modules 111 and the master control device 13 can be shortened.

[0016] Figure 2 shows the configuration of a master control device for a DC circuit breaker according to Embodiment 1. The master control device 13 includes a protection relay interface 131 for communication with a protection relay, an emergency stop button interface 132 for communication with an emergency stop button, a remote operation interface 133 for accepting remote operations, a local operation interface 134 for accepting local operations, a processing unit 135 for performing processing for control, monitoring, and protection, a current limiter interface 136 for communication with a current limiter 11, and a residual current circuit breaker interface 137 for communication with a residual current circuit breaker 12. The master control device 13 uses the current limiter interface 136 to periodically perform serial communication with the current limiting module 111 at a communication cycle of 3 μs or less to send and receive data. The master control device 13 also uses the residual current circuit breaker interface 137 to monitor and control the residual current circuit breaker 12.

[0017] FIG. 3 is a diagram showing the configuration of a current limiter of a DC circuit breaker according to Embodiment 1. The current limiting module 111 includes a mechanical switch 191, a zero-cross point generation unit 195 having a reactor 192, a capacitor 193, and a power converter (VSC: Voltage Source Converter) 194, and a metal oxide surge arrester (MOSA) 196. The zero-cross point generation unit 195 in which the reactor 192, the capacitor 193, and the power converter 194 are connected in series is connected in parallel with the mechanical switch 191. The surge arrester 196 is connected in parallel to the capacitor 193 and the power converter 194 in the zero-cross point generation unit 195. Each current limiting module 111 is connected in series. The zero-cross point generation unit 195 superimposes an amplified oscillating alternating current on the DC fault current to generate a current zero point. After the mechanical switch 191 of the current limiting module 111 is opened, the zero-cross point generation unit 195 forms a current zero point and interrupts the current, so that the current is diverted to the surge arrester 196, and the energy of the current is converted into thermal energy and consumed to interrupt the current.

[0018] A plurality of current limiting modules 111 are combined to play a role of consuming energy when interrupting the DC current and a role of ensuring the withstand voltage performance against the system voltage. The role of consuming energy when interrupting the DC current is performed by the surge arrester 196. Since a large amount of energy needs to be consumed when interrupting the DC current, the surge arresters 196 of a plurality of current limiting modules 111 share and consume the energy. Also. After the DC current is interrupted, the system voltage is applied to the current limiter 11. Since the withstand voltage performance of each current limiting module 111 is small, the withstand voltage performance against the system voltage is ensured by sharing among a plurality of current limiting modules 111.

[0019] In the interruption of the fault current flowing through the DC circuit breaker 10 due to a fault in the power system, the fault current is interrupted by the current limiter 11 and the current is limited to the current zero point, and then the residual current is interrupted by the residual current circuit breaker 12. Since the residual current circuit breaker 12 does not have the function of interrupting the DC current, it is necessary to prevent equipment damage by means of an interruption control flow considering the coordinated operation of the current limiter 11 and the residual current circuit breaker 12. For this reason, the master control device 13 has a first function of interrupting the fault current by outputting an interruption control command in the order of the current limiting module 111 and the residual current circuit breaker 12, and a second function of outputting an input control command in the order of the current limiting module 111 and the residual current circuit breaker 12.

[0020] Figure 4 is a flowchart showing the flow of interruption control of the DC circuit breaker according to Embodiment 1. In step S11, the master control device 13 receives a DC circuit breaker interruption control command from the upper control device 20.

[0021] In step S12, the master control device 13 determines whether or not the current limiter interruption control interlock condition is released.

[0022] The current limiter interruption control interlock condition is a condition for preventing the interruption operation of the fault current in order to protect the DC circuit breaker 10 under the event that a serious fault has occurred in the current limiter 11. That is, the DC circuit breaker 10 does not perform the interruption operation of the fault current when the current limiter interruption control interlock condition is satisfied, and executes the interruption operation of the fault current only when the current limiter interruption control interlock condition is released. Here, the event that a serious fault has occurred in the current limiter 11 means that the current limiter 11 is in a state where it cannot perform its original role of interrupting the fault current and limiting the current to the current zero point. When the current limiter interruption control interlock condition is satisfied, it becomes No in step S12. When the current limiter interruption control interlock condition is not satisfied, it becomes Yes in step S12. When it becomes No in step S12, the interruption operation cannot be executed, so the process ends. When it becomes Yes in step S12, the process proceeds to step S13.

[0023] In step S13, the master control device 13 outputs a shutoff control command to the current limiting module 111.

[0024] In step S14, the current limiting module 111, having received a shutdown control command from the master control device 13, performs a shutdown operation.

[0025] In step S15, the master control device 13 determines whether the number of current-limiting modules 111 that have successfully shut off is equal to or greater than the number of current-limiting modules 111 required to limit the fault current. If the number of current-limiting modules 111 that have successfully shut off is equal to or greater than the number of current-limiting modules 111 required to limit the fault current, the result in step S15 is Yes, and the process proceeds to step S16. If the number of current-limiting modules 111 that have successfully shut off is less than the number of current-limiting modules 111 required to limit the fault current, the result in step S15 is No, and the process ends.

[0026] The point at which the current limiting module 111 determines that it has successfully performed the interruption operation is at least one of the following: the current in the main circuit becomes zero, or an inter-pole voltage is generated in the mechanical switch 191.

[0027] In step S16, the master control device 13 determines whether or not the residual current circuit breaker trip control interlock condition has been released.

[0028] The residual current circuit breaker interruption control interlock condition is a condition that prevents the DC circuit breaker 10 from interrupting the fault current in order to protect the DC circuit breaker 10 in the event of a severe fault in the residual current circuit breaker 12. In other words, the DC circuit breaker 10 does not interrupt the fault current when the residual current circuit breaker interruption control interlock condition is met, and only performs the fault current interruption operation when the residual current circuit breaker interruption control interlock condition is released. Here, the event of a severe fault in the residual current circuit breaker 12 is a state in which the residual current circuit breaker 12 is unable to perform its original role of interrupting the residual current that flows after the fault current has been interrupted. If the residual current circuit breaker interruption control interlock condition is met, the result in step S16 is No. If the residual current circuit breaker interruption control interlock condition is not met, the result in step S16 is Yes. If the result in step S16 is No, the interruption operation cannot be performed, so the process ends. If the result in step S16 is Yes, the process proceeds to step S17.

[0029] In step S17, the master control device 13 outputs a tripping control command to the residual current circuit breaker 12.

[0030] In step S18, the residual current circuit breaker 12, having received a tripping control command from the master control device 13, performs a residual current tripping operation.

[0031] In step S19, the master control device 13 checks the tripped state of the residual current circuit breaker 12. If the residual current circuit breaker 12 is tripped, the response in step S19 is Yes, and the process proceeds to step S20. If the residual current circuit breaker 12 is not tripped, the response in step S19 is No, and the process ends.

[0032] In step S20, the master control device 13 notifies the higher-level control device 20 that the DC circuit breaker 10 has entered the tripped state.

[0033] Furthermore, if there is a possibility that the cause of the fault may disappear naturally after the fault current flowing through the DC circuit breaker 10 is interrupted due to an accident in the power system, the DC circuit breaker 10 is closed in the order of the current limiting module 111 and then the residual current circuit breaker 12. When closing the DC circuit breaker 10 to connect the DC bus and the DC line, unlike the residual current circuit breaker 12 which has withstand voltage against the system voltage as a standalone device, the current limiting module 111 alone does not have withstand voltage against the system voltage. Therefore, it is necessary to prevent equipment damage by using a closing control flow that takes into account the coordinated operation of the current limiter 11 and the residual current circuit breaker 12.

[0034] As described above, the DC circuit breaker 10 according to Embodiment 1 outputs the tripping control command to the residual current circuit breaker 12 when the first function is executed and a number of current-limiting modules 111 or more of the plurality of current-limiting modules 111 have successfully tripped. In other words, when the DC circuit breaker 10 according to Embodiment 1 is executed, it confirms that a number of current-limiting modules 111 or more of the preset number have tripped before tripping the residual current circuit breaker 12. Therefore, the residual current circuit breaker 12 will not trip when some of the current-limiting modules 111 have failed and fewer than the preset number of current-limiting modules 111 have tripped. This prevents the residual current circuit breaker 12 from tripping when the fault current has not been limited to a size that the residual current circuit breaker 12 can trip, thus preventing the residual current circuit breaker 12 from failing.

[0035] Figure 5 is a flowchart showing the flow of DC circuit breaker closing control according to Embodiment 1. In step S31, the master control device 13 receives a DC circuit breaker closing control command from the higher-level control device 20.

[0036] In step S32, the master control device 13 determines whether or not the current limiter closing control interlock condition has been released.

[0037] The current limiter closing control interlock condition is a condition that prevents the DC circuit breaker 10 from closing in order to protect it when a severe fault occurs in the current limiter 11. In other words, the DC circuit breaker 10 does not close when the current reducer interruption control interlock condition is met, and only closes when the current limiter interruption control interlock condition is released. Here, a severe fault in the current limiter 11 means that the current limiter 11 is in a state where it cannot perform its original role of interrupting the fault current and limiting the current to zero. If the current limiter closing operation interlock condition is met, the result in step S32 is No. If the current limiter closing operation interlock condition is not met, the result in step S32 is Yes. If the result in step S32 is No, the closing operation cannot be performed, so the process ends. If the result in step S32 is Yes, the process proceeds to step S33.

[0038] In step S33, the master control device 13 outputs an activation control command to the current limiting module 111.

[0039] In step S34, the current limiting module 111, having received a closing control command from the master control device 13, performs a closing operation.

[0040] In step S35, the master control device 13 checks whether the current limiter 11 is in the closed state. If the current limiter 11 is in the closed state, the result in step S35 is Yes, and the process proceeds to step S36. If the current limiter 11 is not in the closed state, the result in step S35 is No, and the process ends.

[0041] In step S36, the master control device 13 determines whether or not the residual current circuit breaker closing control interlock condition has been released.

[0042] The residual current circuit breaker closing control interlock condition is a condition that prevents the DC circuit breaker 10 from closing in order to protect it when a serious fault occurs in the residual current circuit breaker 12. In other words, the DC circuit breaker 10 does not close when the residual current circuit breaker closing control interlock condition is met, and only closes when the residual current circuit breaker closing control interlock condition is released. Here, a serious fault in the residual current circuit breaker 12 means that the residual current circuit breaker 12 is in a state where it cannot perform its original role of interrupting the residual current that flows after the fault current has been interrupted. If the residual current circuit breaker closing control interlock condition is met, the result in step S36 is No. If the residual current circuit breaker closing control interlock condition is not met, the result in step S36 is Yes. If the result in step S36 is No, the closing operation cannot be performed, so the process ends. If the result in step S36 is Yes, the process proceeds to step S37.

[0043] In step S37, the master control device 13 outputs a closing control command to the residual current circuit breaker 12.

[0044] In step S38, the residual current circuit breaker 12, having received a closing control command from the master control device 13, performs a closing operation.

[0045] In step S39, the master control device 13 checks the closed state of the residual current circuit breaker 12. If the residual current circuit breaker 12 is closed, the result in step S39 is Yes, and the process proceeds to step S40. If the residual current circuit breaker 12 is not closed, the result in step S39 is No, and the process ends.

[0046] In step S40, the master control device 13 notifies the higher-level control device 20 that the DC circuit breaker 10 has been closed.

[0047] As described above, the DC circuit breaker 10 according to Embodiment 1 closes the residual current circuit breaker 12 only after confirming that all current limiting modules 111 are closed. Therefore, the residual current circuit breaker 12 will not be closed when some of the current limiting modules 111 are faulty and only some of the current limiting modules 111 are closed. This prevents the residual current circuit breaker 12 from being closed when the current limiter 11 cannot ensure sufficient voltage resistance against the system voltage, thereby preventing the current limiter 11 from failing.

[0048] When a fault current is interrupted, the energy of the fault current is handled by the surge arrester 196 located within the current-limiting module 111. The fewer the number of current-limiting modules 111, the greater the energy that each current-limiting module 111 needs to handle, so it is necessary to operate in a way that does not exceed the capacity of the surge arrester 196.

[0049] The DC circuit breaker 10 has a high-speed reclosing responsibility as part of its tripping duties, and it is necessary to perform "Ot-CO". Generally, for high-speed reclosing duties, t = 300 ms is required. Here, "O" represents the tripping operation, "t" represents the time interval between consecutive tripping operations, and "CO" represents the tripping operation following the closing operation. In other words, the tripping duty of the DC circuit breaker 10 is to perform a closing operation after a predetermined time of approximately 300 ms has elapsed since the tripping operation, and to perform a tripping operation immediately if the cause of the fault has not been resolved. This allows power transmission to be resumed if a fault is falsely detected or if the cause of the fault is resolved in a short time.

[0050] In the tripping duty of the DC circuit breaker 10, the closing operation performed after a preset time has elapsed following the tripping operation is called "reclosing." However, if the DC circuit breaker 10 is given a reclosing function, two current tripping duties will occur with a short time interval between tripping operations. This creates a large and demanding condition for the surge arrester 196, as it will have to process a large amount of fault current energy. For this reason, the DC circuit breaker 10 according to Embodiment 1 temporarily locks the activation of the closing operation according to the number of current limiting modules 111 at the time of the initial tripping, thereby preventing damage to the surge arrester 196 due to exceeding the processing energy limit. After the lock is released, the circuit breaker recloses based on commands from the higher-level control device 20 and the master control device 13. Thus, in addition to the first and second functions described above, the DC circuit breaker 10 according to Embodiment 1 has a third function that, during reclosing after the fault current has been interrupted, stops the output of the closing control command to the current limiting module 111 from the time the current limiting module 111 performs the tripping operation until it returns to a state where it can perform the operation to interrupt the fault current.

[0051] Figure 6 is a flowchart showing the processing flow for the reclosing start lock of a DC circuit breaker according to Embodiment 1. In step S51, the master control device 13 determines whether the module interruption control command output to the current limiter 11 is the first interruption control command. If the module interruption control command output to the current limiter 11 is the first interruption control command, the result in step S51 is Yes, and the process proceeds to step S52. If the module interruption control command output to the current limiter 11 is not the first interruption control command, the result in step S51 is No, because it has already been executed when the first interruption control command was output, and the process ends.

[0052] In step S52, the master control device 13 determines whether the number of current-limiting modules 111 that have successfully shut off is equal to or greater than the number of current-limiting modules 111 required to limit the fault current. If the number of current-limiting modules 111 that have successfully shut off is equal to or greater than the number of current-limiting modules 111 required to limit the fault current, the result in step S52 is Yes, and the process proceeds to step S53. If the number of current-limiting modules 111 that have successfully shut off is less than the number of current-limiting modules 111 required to limit the fault current, the result in step S52 is No, and the process proceeds to step S61.

[0053] In step S61, the master control device 13 starts counting the cool time counter.

[0054] In step S62, the master control device 13 locks the reclosing start. After the processing in step S62, the process proceeds to step S57.

[0055] In step S57, the master control device 13 waits until the count value c of the cool time counter becomes equal to or greater than a preset second threshold T2. The second threshold T2 is set based on the time it takes for the surge arrester 196 to recover to a state where it can perform the reclosing operation again after the completion of the second tripping operation. In step S58, the master control device 13 releases the reclosing start lock.

[0056] In step S59, the master control device 13 terminates the count of the cool time counter and clears the count value c to zero.

[0057] In step S53, the master control device 13 starts counting the cool time counter.

[0058] In step S54, the master control device 13 determines whether or not to output a second module shutdown control command to the current limiter 11. If the second module shutdown control command is output to the current limiter 11, the result in step S54 is Yes, and the process proceeds to step S55. If the second module shutdown control command is not output to the current limiter 11, the result in step S54 is No, and the process proceeds to step S60.

[0059] In step S55, the master control device 13 locks the reclosing start. In step S56, the master control device 13 waits until the count value c of the cool time counter is equal to or greater than a preset first threshold T1. The first threshold T1 is set based on the time it takes for the surge arrester 196 to recover after the completion of the first tripping operation and to be able to perform the second tripping operation.

[0060] In step S60, the master control device 13 determines whether the count value c of the cool time counter is equal to or greater than a preset first threshold T1. If the count value c of the cool time counter is equal to or greater than the preset first threshold, the process proceeds to step S59. If the count value c of the cool time counter is not equal to or greater than the preset first threshold T1, the result in step S60 is No, and the process proceeds to step S54.

[0061] Thus, in the DC circuit breaker 10 according to Embodiment 1, if the result in step S52 is No, the reclosing start is locked until the count value c of the cool time counter activated in step S61 becomes equal to or greater than the second threshold T2. Therefore, even if the DC circuit breaker 10 receives a new tripping control command from the higher-level control device 20 immediately after failing to trip, it is possible to prevent reclosing until it becomes possible to interrupt the fault current.

[0062] The master control device 13 outputs control commands to the current limiting module 111 and the residual current circuit breaker 12 at the appropriate timing in accordance with the interruption and on-off commands from the higher-level control device 20. In addition, it is responsible for the interlock function of the current limiting module 111 and the residual current circuit breaker 12 related to the above control function, and for monitoring the status of the current limiting module 111 and the residual current circuit breaker 12.

[0063] In controlling the switching of the DC circuit breaker 10, it is necessary to control the current limiting module 111 and the residual current circuit breaker 12 at the appropriate timing. If the current limiting module 111 and the residual current circuit breaker 12 receive the tripping command and the closing command at the inappropriate timing, unintended operation may occur, potentially damaging the equipment. The DC circuit breaker 10 according to Embodiment 1 is equipped with the necessary interlock conditions for each of the following: tripping command by the protective relay, operation of the emergency stop button, remote switching operation, and local switching operation. This prevents the current limiting module 111 and the residual current circuit breaker 12 from receiving the tripping command and the closing command at the inappropriate timing.

[0064] Furthermore, in the DC circuit breaker 10 according to Embodiment 1, the master control device 13 constantly monitors the status of the current limiting module 111 and the residual current circuit breaker 12, receives status signals from the current limiting module 111 and the residual current circuit breaker 12 indicating the control status, setting status, abnormal status, and measurement information of the equipment, and executes a pre-set action when an abnormality is detected. For example, if some of the multiple current limiting modules 111 fail, the master control device 13 will not output a tripping control command or a switching control command to the failed current limiting module 111 or to the residual current circuit breaker 12 during tripping control or switching control. As a result, even if some of the multiple current limiting modules 111 fail, if the current limiter 11 can still perform its original function, the failed current limiting module 111 can be disconnected and operation can continue.

[0065] Furthermore, in the DC circuit breaker 10 according to Embodiment 1, if only a number of current-limiting modules 111 are functioning correctly that are insufficient to limit the fault current to a size that can be interrupted by the residual current circuit breaker 12, and the current limiter 11 is unable to perform its intended function, the DC circuit breaker 10 can prevent the residual current circuit breaker 12 from failing by preventing both the current limiter 11 and the residual current circuit breaker 12 from performing interruption and closing operations.

[0066] Furthermore, in the DC circuit breaker 10 according to Embodiment 1, the master control device 13 detects the tripping command received from the protective relay device and distributes the tripping command to each current limiting module 111. After each current limiting module 111 receives the tripping command, the opening and closing control of the zero-crossing point generation unit 195 located within each current limiting module 111 is performed. The zero-crossing point generation unit 195 plays a role in generating a current zero point by superimposing an amplified oscillating AC current onto the DC fault current. However, in order to achieve high-current interruption during a fault in the power system, it is necessary to control multiple current limiting modules 111 simultaneously. In the DC circuit breaker 10 according to Embodiment 1, communication between the master control device 13 and the current limiting modules 111 is performed at a period of 3 μs or less, thus reducing variations in the timing of zero-crossing point generation.

[0067] The hardware configuration of the processing unit 135 of the master control device 13 of the DC circuit breaker 10 according to Embodiment 1 will now be described. Figure 7 is a diagram showing the hardware configuration of the processing unit of the master control device of the DC circuit breaker according to Embodiment 1. The processing unit 135 of the master control device 13 is realized by a computer system that includes a processor 91 that performs various processes, a memory 92 which is the main memory, and a storage device 93 that stores information.

[0068] The processor 91 may be a computing device such as an arithmetic unit, microprocessor, microcomputer, CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), or DSP (Digital Signal Processor). The memory 92 may be a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory). The storage device 93 stores a program for controlling the current limiter 11 and the residual current circuit breaker 12.

[0069] The above computer system implements the function of controlling the current limiter 11 and the residual current circuit breaker 12 by having the processor 91 read programs corresponding to the processing of each component stored in the storage device 93 into the memory 92 and execute them. The memory 92 is also used as temporary memory for each process executed by the processor 91. The programs executed by the processor 91 may be provided in a state stored on a storage medium or provided via a network.

[0070] The configurations shown in the above embodiments are merely examples of the content, and can be combined with other known technologies. It is also possible to omit or modify parts of the configuration without departing from the gist of the invention. [Explanation of symbols]

[0071] 10 DC circuit breaker, 11 current limiter, 12 residual current circuit breaker, 13, 13a, 13b master control unit, 20, 20a, 20b higher-level control unit, 91 processor, 92 memory, 93 storage device, 111, 111a, 111b, 111n current limiting module, 131 protective relay interface, 132 emergency stop button interface, 133 remote operation interface, 134 local operation interface, 135 processing unit, 136 current limiter interface, 137 residual current circuit breaker interface, 191 mechanical switch, 192 reactor, 193 capacitor, 194 power converter, 195 zero-crossing point generator, 196 surge arrester.

Claims

1. The system comprises a current limiter having multiple current limiting modules connected in series to interrupt fault currents flowing through the power system and limit them to zero current, a residual current circuit breaker that interrupts residual currents that flow after the fault currents have been interrupted, and a master control device that controls and monitors the status of the current limiter and the residual current circuit breaker. The master control device has a first function of interrupting the fault current by outputting an interruption control command in the order of the current limiting module and the residual current circuit breaker, A second function that outputs an on-off control command in the order of the current limiting module and the residual current circuit breaker, The system also includes a third function that, upon reclosing after interrupting the fault current, stops outputting the current-limiting control command to the current-limiting module from the time the current-limiting module performs the interruption operation until it returns to a state where it can perform the operation to interrupt the fault current, A DC circuit breaker characterized in that, when the first function is executed, if a preset number or more of the current-limiting modules among the plurality of current-limiting modules successfully perform the tripping operation, the circuit breaker outputs the tripping control command to the residual current circuit breaker.

2. The DC circuit breaker according to claim 1, characterized in that the master control device determines whether or not to perform the first function and the second function based on a preset interlock condition.

3. The master control device and the current limiting module are connected serially by an optical fiber. The DC circuit breaker according to claim 1, characterized in that the master control device includes a current limiter interface that periodically sends and receives data with the current limiting module at a preset communication cycle.

4. The DC circuit breaker according to claim 3, characterized in that the communication period between the master control device and the current limiting module is 3 μs or less.

5. The master control device and the residual current circuit breaker are connected by a metal cable. The DC circuit breaker according to claim 1, characterized in that the master control device includes a residual current circuit breaker interface for monitoring and controlling the residual current circuit breaker.

6. A current limiter comprising a plurality of current limiting modules connected in series to interrupt fault currents flowing through a power system and limit them to a current zero point; a residual current circuit breaker to interrupt residual currents that flow after the interruption of the fault current; and a master control device for controlling and monitoring the status of the current limiter and the residual current circuit breaker, The master control device has a first function of interrupting the fault current by outputting an interruption control command in the order of the current limiting module and the residual current circuit breaker, It also has a second function that outputs an on-off control command in the order of the current limiting module and the residual current circuit breaker, When the first function is executed, if a preset number or more of the current-limiting modules among the plurality of current-limiting modules successfully perform the tripping operation, the tripping control command is output to the residual current circuit breaker. If some of the multiple current-limiting modules fail, the master control device will disconnect the failed current-limiting module and output the disconnection control command and the on-off control command only to the non-failed current-limiting modules, thereby continuing the first and second functions, provided that a sufficient number of current-limiting modules remain capable of interrupting and limiting the fault current. A DC circuit breaker characterized in that, if there are not enough current-limiting modules remaining that can interrupt and limit the fault current, it stops the output of the interruption control command and the closing control command to the multiple current-limiting modules and the residual current circuit breaker, thereby stopping the first function and the second function.

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