WO2021106191A1

WO2021106191A1 - Direct-current circuit breaker

Info

Publication number: WO2021106191A1
Application number: PCT/JP2019/046772
Authority: WO
Inventors: 優平橋本; 健作宮崎
Original assignee: 株式会社東芝; 東芝エネルギーシステムズ株式会社
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2021-06-03
Also published as: EP4068326A4; JP7214893B2; EP4068326B1; JPWO2021106191A1; CN114467161B; CN114467161A; EP4068326A1

Abstract

This direct-current circuit breaker has a mechanical circuit breaker, a surge arrester, and a commutation circuit. The mechanical circuit breaker is connected to a first direct-current transmission line at a first end thereof and to a second direct-current transmission line at a second end thereof. The commutation circuit has a first switch, a second switch, a reactor, a capacitor, and a resistor. The commutation circuit, the surge arrester, and the mechanical circuit breaker are parallelly connected between the first direct-current transmission line and the second direct-current transmission line. The first switch, the capacitor, and the reactor are serially connected between the first direct-current transmission line and the second direct-current transmission line. The second switch and the resistor are serially connected and disposed in parallel with the first switch.

Description

DC circuit breaker

An embodiment of the present invention relates to a DC circuit breaker.

In recent years, electric power has been transmitted by a DC transmission network in which a plurality of DC transmission lines are configured in a grid pattern. In the case of an accident in the DC power grid, only a specific power line may be cut off and the remaining power lines may continue to transmit power. In this regard, a technique related to a DC cutoff device that cuts off the current flowing through the DC transmission line is known.

By the way, the DC circuit breaker includes a semiconductor circuit breaker using a semiconductor circuit breaker, a mechanical circuit breaker using a mechanical circuit breaker, and a hybrid circuit breaker using both a semiconductor circuit breaker and a mechanical circuit breaker. A mechanical circuit breaker type DC circuit breaker closes a commutation circuit equipped with a commutation switch, a commutation capacitor, and a commutation reactor, and generates a resonance current in the current flowing through the DC transmission line to generate a zero point. As a result, the mechanical circuit breaker is cut off, and the current flowing through the DC transmission line is cut off.

In addition, the commutation switch includes a mechanical method that mechanically moves one or both of the electrodes to make the electrodes electrically and mechanically conductive, and semiconductors such as thyristors and IGBTs (Insulated Gate Bipolar Transistor). There are a semiconductor method that uses an element to make it conductive, and a discharge method that makes it electrically conductive by lowering the insulation performance by adding an external factor between the fixed electrodes. Further, the mechanical commutation switch has a pair of electrodes, and at least one of the electrodes is moved to bring the distance between the electrodes closer, and the insulation performance between the electrodes is lowered from the open state to cause dielectric breakdown. There are a contact method in which the electrodes are closed with a pair of electrodes, and a non-contact method in which the electrodes have a pair of fixed electrodes and the insulation performance between the electrodes is lowered from that in the open state to cause dielectric breakdown.

Here, in the mechanical commutation switch, in the closed state, an arc is generated due to dielectric breakdown between the electrodes, and the switch becomes electrically conductive. Therefore, the mechanical commutation switch has a problem that a surge may be generated due to dielectric breakdown and peripheral circuit elements and other peripheral devices may malfunction or fail.

In addition, the DC cutoff device may be required to be responsible for reclosing the circuit. In hybrid circuit breaker and semiconductor circuit breaker DC circuit breakers, the commutation capacitor is charged by the recovery voltage when the accident current is interrupted, so even after the reclosing is performed, the mechanical circuit breaker is interrupted. It was possible to cut off the current flowing through the DC transmission line.

On the other hand, in a DC cutoff device that uses a mechanical commutation switch, the current flowing between the electrodes is cut off by recovering the insulation performance between the electrodes of the commutation switch, or the arc is extinguished at the current zero point. Therefore, the electrical conduction state may be terminated without the charging state of the commutation capacitor being appropriate. In this case, there is a problem that the commutation capacitor is not sufficiently charged or is charged to a predetermined voltage or higher, and the circuit cannot be properly reclosed.

International Publication No. 2015/1666600

The problem to be solved by the present invention is to provide a DC circuit breaker capable of appropriately reclosing the circuit while suppressing a surge.

The DC circuit breaker of the embodiment has a mechanical circuit breaker, a lightning arrester, and a commutation circuit. The first end of the mechanical circuit breaker is connected to the first DC transmission line, and the second end is connected to the second DC transmission line. The commutation circuit has a first switch, a second switch, a reactor, a capacitor, and a resistor. The commutation circuit, the lightning arrester, and the mechanical circuit breaker are connected in parallel to each other between the first DC power transmission line and the second DC power transmission line. The first switch, the capacitor, and the reactor are connected in series between the first DC power transmission line and the second DC power transmission line. A switch in which the second switch and the resistor are connected in series is provided in parallel with the first switch.

It is a figure which shows an example of the structure of the DC circuit breaker 1 of an embodiment. It is a figure which shows typically the abnormality which occurred in the DC system. It is a figure which shows the state of the DC circuit breaker 1 in which the mechanical circuit breaker 10 is controlled to the mechanically open state. It is a figure which shows the state of the DC circuit breaker 1 which controlled the surge switch 80 to the closed state. It is a figure which shows the state of the DC circuit breaker 1 which controlled the commutation switch 50 to the closed state. It is a figure which shows the state of the DC circuit breaker 1 in which the mechanical circuit breaker 10 is electrically controlled to open state. It is a figure which shows the state of the DC circuit breaker 1 in which a lightning arrester 15 operated. It is a figure which shows the state of the DC circuit breaker 1 controlled in the state which charges a commutation capacitor 60. It is a figure which shows the state of the DC circuit breaker 1 which controlled the commutation switch 50 in an open state. It is a figure which shows the state of the DC circuit breaker 1 which controlled the surge switch 80 to the open state. It is a figure which shows the state of the DC circuit breaker 1 which controlled the 1st disconnector 20 and the 2nd disconnector 30 in an open state. It is a graph which shows an example of the time-dependent change concerning DC circuit breaker 1. It is a flowchart which shows an example of the operation of a DC circuit breaker 1.

Hereinafter, the DC circuit breaker of the embodiment will be described with reference to the drawings.

(Embodiment)
[Configuration of DC circuit breaker 1]
FIG. 1 is a diagram showing an example of the configuration of the DC circuit breaker 1 of the embodiment. The DC circuit breaker 1 is a device that electrically conducts or cuts off the first DC transmission line LN1 and the second DC transmission line LN2 among the DC transmission lines constituting the DC system. In the following description, the DC voltage in the first DC transmission line LN1 will be referred to as the first voltage VDC1, and the DC voltage in the second DC transmission line LN2 will be referred to as the second voltage VDC2. The first voltage VDC1 and the second voltage VDC2 are, for example, a voltage of about several tens to several hundreds [kV]. For example, a power transmission facility exists on the first DC transmission line LN1 side, and a consumer exists on the second DC transmission line LN2 side. In this case, the first voltage VDC1 is usually larger than the second voltage VDC2. Therefore, normally, the DC system current flows in the direction from the first DC transmission line LN1 to the second DC transmission line LN2.

The DC circuit breaker 1 includes, for example, one or more mechanical circuit breakers 10, one or more disconnectors, a lightning arrester 15, a commutation circuit 40, and a control unit 100. In the present embodiment, a case where the DC circuit breaker 1 includes two disconnectors, a first disconnector 20 and a second disconnector 30, will be described. In the following description, when the first disconnector 20 and the second disconnector 30 are not distinguished, they are simply referred to as "disconnector". The commutation circuit 40 includes, for example, a commutation switch 50, a commutation capacitor 60, a commutation reactor 70, a surge switch 80, and a surge resistor 90.

The control unit 100 indicates, for example, a signal (hereinafter, cutoff) indicating that the first DC power transmission line LN1 and the second DC power transmission line LN2 are electrically cut off from a detection device (not shown) for detecting an abnormality in the DC system. (Instruction signal) is received. When the control unit 100 receives the cutoff instruction signal, the mechanical circuit breaker 10, the first disconnector 20, and the first disconnector so as to electrically cut off the first DC power transmission line LN1 and the second DC power transmission line LN2. 2 Controls the open / closed state of the disconnector 30, the commutation switch 50, and the surge switch 80. An abnormality in a DC system is, for example, an abnormality caused by an accident such as a ground fault or a short circuit occurring in a DC transmission line.

The mechanical circuit breaker 10 includes a first terminal 10a and a second terminal 10b. The first disconnector 20 includes a first terminal 20a and a second terminal 20b. The second disconnector 30 includes a first terminal 30a and a second terminal 30b. The commutation circuit 40 includes a first terminal 40a and a second terminal 40b. The commutation switch 50 includes a first terminal 50a and a second terminal 50b. The surge switch 80 includes a first terminal 80a and a second terminal 80b.

The first disconnector 20, the mechanical circuit breaker 10, and the second disconnector 30 are connected in series between the first DC transmission line LN1 and the second DC transmission line LN2 in the order described. Specifically, the first terminal 10a of the first disconnector 20 is connected to the first DC transmission line LN1, and the second terminal 20b of the first disconnector 20 and the first terminal 10a of the mechanical circuit breaker 10 Is connected, the second terminal 10b of the mechanical circuit breaker 10 and the first terminal 30a of the second disconnector 30 are connected, and the second terminal 30b of the second disconnector 30 is connected to the second DC transmission line LN2. Will be done.

The lightning arrester 15 and the commutation circuit 40 are connected to the mechanical circuit breaker 10 in parallel with each other. Specifically, the first terminal 10a of the mechanical circuit breaker 10, one end of the lightning arrester 15, and the first terminal 40a of the commutation circuit 40 are connected to each other, and the second terminal 10b of the mechanical circuit breaker 10 and the second terminal 10b. The other end of the lightning arrester 15 and the second terminal 40b of the commutation circuit 40 are connected to each other.

In the commutation circuit 40, the commutation switch 50, the commutation capacitor 60, and the commutation reactor 70 are connected in series between the first terminal 40a and the second terminal 40b in the order described. Specifically, the first terminal 40a and the first terminal 50a of the commutation switch 50 are connected to the second terminal 50b of the commutation switch 50 and one end of the commutation capacitor 60 (positive electrode terminal in the figure). Is connected, the other end of the commutation capacitor 60 (negative electrode terminal in the figure) and one end of the commutation reactor 70 are connected, and the other end of the commutation reactor 70 and the second terminal 40b are connected. Further, in the commutation circuit 40, the surge switch 80 and the surge resistor 90 are connected in series in the order described and connected in parallel to the commutation switch 50. Specifically, the first terminal 80a of the surge switch 80 is connected to the first terminal 50a of the commutation switch 50, the second terminal 80b of the surge switch 80 is connected to one end of the surge resistance 90, and the surge resistance 90 The other end of is connected to the second terminal 50b of the commutation switch 50.

In the above description, the case where the commutation circuit 40 includes the first terminal 40a and the second terminal 40b has been described, but the present invention is not limited to this, and the commutation circuit 40 includes the first terminal 40a and the second terminal 40b. It does not have to be provided. In this case, in the above-described configuration, the parts connected via the first terminal 40a and the second terminal 40b are directly connected. Hereinafter, for convenience of explanation, the commutation circuit 40 will be described as including the first terminal 40a and the second terminal 40b.

The lightning arrester 15 absorbs the surge voltage generated when the mechanical circuit breaker 10 is controlled to the closed state. The limiting voltage of the lightning arrester 15 is 1.5 [p.] When the first voltage VDC1 and the second voltage VDC2 are used as a reference in a state where no abnormality such as an accident has occurred in the DC system. u] is about the size.

The commutation switch 50 is, for example, a mechanical switch. Specifically, the commutation switch 50 has a pair of electrodes, and at least one of the electrodes is moved based on the control of the control unit 100 to bring the distance between the electrodes closer, and the insulation performance between the electrodes is opened. It is a contact type switch that closes by lowering it and breaking the insulation. The commutation switch 50 is an example of a “first switch”.

The commutation switch 50 may be a non-contact switch. In this case, the commutation switch 50 has a pair of fixed electrodes, and the insulation performance between the electrodes is lowered from the open state to break down the insulation based on the control of the control unit 100, so that the commutation switch 50 is closed.

The commutation capacitor 60 is, for example, in a state in which the voltage generated between the positive electrode terminal and the negative electrode terminal (hereinafter referred to as the capacitor voltage) by a charging device (not shown) in the initial state does not cause an abnormality such as an accident in the DC system. It is charged so as to match or substantially match the first voltage VDC1 and the second voltage VDC2 in the above. The initial state is, for example, when the DC circuit breaker 1 is installed or when the operation of the DC circuit breaker 1 is started. The charging device may charge the commutation capacitor 60 by applying a system voltage of the DC system, for example, or may charge the commutation capacitor 60 by an external power source other than the system voltage of the DC system. The commutation capacitor 60 is, for example, a capacitor having a charging capacity of several to several tens [μF].

The commutation capacitor 60 and the commutation reactor 70 form an LC resonance circuit as the commutation switch 50 is controlled to a closed state, and the capacitor component of the commutation capacitor 60 and the reactor of the commutation reactor 70 are formed. The DC system current is resonated by the resonance frequency corresponding to the component, and the timing at which the DC system current becomes 0 [A] is generated. Hereinafter, generating the timing at which the DC system current becomes 0 [A] is also described as "generating a zero point". The commutation reactor 70 is commutated so that the reclosing time from the time tg to th, which will be described later, does not exceed a predetermined maximum value of the reclosing time while ensuring a predetermined reclosing time. A value is set according to the capacity of the capacitor 60.

The surge switch 80 is, for example, a mechanical switch. The surge switch 80 is an example of a “second switch”.

The surge resistor 90 reduces the surge generated when the commutation switch 50 is controlled to the closed state by dielectric breakdown while the surge switch 80 is controlled to the closed state. The surge resistor 90 is, for example, a resistor having a resistance value of about several hundred to several k [Ω].

Hereinafter, each state of the DC circuit breaker 1 will be described with reference to FIGS. 2 to 11. Further, with reference to FIG. 12, a time-dependent change in the open / closed state of each part of the DC circuit breaker 1 or an electrical time-dependent change in each part will be described. FIG. 12 is a graph showing an example of a change with time of the DC circuit breaker 1. In FIG. 12, the horizontal axis represents time. The waveform W10 indicates the open / closed state of the mechanical circuit breaker 10, the waveform W12 indicates the open / closed state of the surge switch 80, the waveform W14 indicates the open / closed state of the commutation switch 50, and the waveform W16 indicates the open / closed state of the disconnector. Indicates the state. In the waveforms W10 to W16, "C" represents a closed state (Close), and "O" represents an open state (Open).

Further, the waveforms W20 to W26 are waveforms showing the time course of the current related to the DC circuit breaker 1, and the vertical axis of the waveforms W20 to W26 shows the magnitude of the current. In the waveforms W20 to W26, the value of the DC system current flowing in the direction from the first DC transmission line LN1 to the second DC transmission line LN2 is shown as a positive value, and the direction from the second DC transmission line LN2 to the first DC transmission line LN1. The value of the DC system current flowing through is indicated by a negative value.

The waveform W20 is a waveform showing a change over time in the direct current system. The waveform W22 is a waveform showing a change over time in the current flowing through the mechanical circuit breaker 10. The waveform W24 is a waveform showing a change over time in the current flowing through the commutation capacitor 60. The waveform W26 is a waveform showing a change over time in the current flowing through the lightning arrester 15.

The waveforms W30 and W32 are waveforms showing the time course of the voltage related to the DC circuit breaker 1, and the vertical axis of the waveforms W30 and W32 shows the magnitude of the voltage. The waveform W30 is a waveform showing a change over time in the voltage applied between the electrodes of the mechanical circuit breaker 10. The waveform W34 is a waveform showing a change over time in the capacitor voltage.

[From continuity to abnormal occurrence]
As shown in FIG. 1, in a state where the first DC power transmission line LN1 and the second DC power transmission line LN2 are electrically conducted by the DC circuit breaker 1 (hereinafter referred to as a conduction state), the control unit 100 sets each unit. Control to the following states. In FIG. 12, the conduction state is between time t0 and ta.
-Mechanical circuit breaker 10: Closed state-Lightning arrester 15: Stopped state-First disconnector 20: Closed state-Second disconnector 30: Closed state-Commutation switch 50: Open state-Surge switch 80: Open state-Rolling Flow capacitor 60: Charged state

FIG. 2 is a diagram schematically showing an abnormality occurring in a DC system. In FIG. 2, a ground fault has occurred in the second DC transmission line LN2, and the second voltage VDC2 has a ground potential. As shown in FIG. 12, the ground fault occurs at time ta. Therefore, as shown by the waveforms W20 to W22, the DC system current and the current flowing through the mechanical circuit breaker 10 hold predetermined values from the time t0 to the time ta, and the commutation circuit 40 moves from the time ta to the time ta. It rises until it operates (until the time td described later).

[After an abnormality occurs]
FIG. 3 is a diagram showing a state of the DC circuit breaker 1 in which the mechanical circuit breaker 10 is controlled to the mechanically open state. The detection device transmits a cutoff instruction signal to the DC circuit breaker 1 when an abnormality occurs in the DC system. The control unit 100 receives a cutoff instruction signal from the detection device at time tb, and controls the mechanical circuit breaker 10 in the open state. The state of each part of the DC circuit breaker 1 at this time is as follows.
-Mechanical circuit breaker 10: Mechanically open state-Lightning arrester 15: Stopped state-First disconnector 20: Closed state-Second disconnector 30: Closed state-Commutation switch 50: Open state-Surge switch 80: Open state・ Commuting capacitor 60: Charged state

As shown by the waveform W10 in FIG. 12, the mechanical circuit breaker 10 is controlled to be closed at time tb, and the electrodes are physically separated from each other. However, in the mechanical circuit breaker 10, even if the electrodes are physically separated from each other, an arc is generated between the electrodes, so that the mechanical circuit breaker 10 is not electrically cut off (that is, it is in a mechanically open state). Therefore, as the waveforms W20 to W22 show, the DC system current and the current flowing through the mechanical circuit breaker 10 increase even during the time tb to tk.

[Surge suppression]
FIG. 4 is a diagram showing a state of the DC circuit breaker 1 in which the surge switch 80 is controlled to the closed state. The control unit 100 controls the surge switch 80 to be closed at time ct in order to reduce the surge associated with closing the commutation switch 50 (see FIG. 12). The state of each part of the DC circuit breaker 1 at this time is as follows.
-Mechanical circuit breaker 10: Mechanically open state-Lightning arrester 15: Stopped state-First disconnector 20: Closed state-Second disconnector 30: Closed state-Commutation switch 50: Open state-Surge switch 80: Closed state・ Commuting capacitor 60: A state in which discharge is slightly started.

In FIG. 4, the surge switch 80 is mechanically controlled to be in a closed state by the control unit 100, and before the electrodes come into contact with each other, an arc is generated by causing dielectric breakdown between the electrodes, and the surge switch 80 is in an electrically conductive state. Become. Therefore, a surge is generated by controlling the surge switch 80 in the closed state, and this surge is suppressed by the surge resistance 90. Further, as the surge switch 80 is controlled to the closed state, in the DC circuit breaker 1, the loop of the mechanical circuit breaker 10, the commutation reactor 70, the commutation capacitor 60, the surge resistance 90, and the surge switch 80 , The capacitor voltage of the commutation capacitor 60 that has been charged in advance, the surge resistance 90, and the commutation reactor 70 act, and a minute commutation current L3 begins to flow.

Since the commutation capacitor 60 is discharged by the flow of this minute commutation current L3, the commutation capacitor 60 is charged from the time ct until the commutation circuit 40 operates, as shown by the waveform W24 in FIG. The flowing current rises slightly. Along with this, as shown by the waveform W32, the capacitor voltage of the commutation capacitor 60 slightly decreases from the time ct until the commutation circuit 40 operates.

[Commutation circuit operation]
FIG. 5 is a diagram showing a state of the DC circuit breaker 1 in which the commutation switch 50 is controlled to the closed state. The control unit 100 closes the commutation switch 50 at time td and operates the commutation circuit 40 (see FIG. 12). As described above, since the surge is already suppressed by the surge resistance 90, the surge does not occur even when the commutation switch 50 is controlled to the closed state, or peripheral circuit elements and other peripheral devices are used. Surge is sufficiently suppressed to the extent that it does not malfunction or break down. The state of each part at this time is as follows.
-Mechanical circuit breaker 10: Mechanically open state-Lightning arrester 15: Stopped state-First disconnector 20: Closed state-Second disconnector 30: Closed state-Commutation switch 50: Closed state-Surge switch 80: Closed state・ Disconnecting capacitor 60: Discharged state

As the commutation switch 50 is controlled to the closed state, the loops of the mechanical circuit breaker 10, the commutation reactor 70, the commutation capacitor 60, and the commutation switch 50 are precharged in the DC circuit breaker 1. The capacitor voltage of the commutation capacitor 60 and the commutation reactor 70 act, and a commutation current L3 that is larger than the minute commutation current L3 that flowed in the scene of FIG. 4 described above starts to flow. The direction of the commutation current L3 differs depending on the connection direction between the positive electrode terminal and the negative electrode terminal of the commutation capacitor 60, the location of the accident that occurred in the DC system, and the like. When the direction of the commutation current L3 is the same as the direction in which the DC system current flows (that is, the same polarity), the commutation current L3 has a commutation current L3 between the time td and 1/2 to 3/4 of the resonance frequency. A zero point is generated. Further, when the direction of the commutation current L3 is different from the direction in which the DC system current flows (that is, the polarity is opposite), the commutation current L3 has a zero point between the time td and the quarter period of the resonance frequency. Will be generated. In the present embodiment, the case where the commutation current L3 is a current having the same polarity as the DC system current will be described.

After time td, a commutation current L3 resonating at a resonance frequency corresponding to the capacitor component of the commutation capacitor 60 and the reactor component of the commutation reactor 70 flows through the mechanical circuit breaker 10. Specifically, as shown by the waveforms W22 and W24 in FIG. 12, the mechanical breaker 10 and the commutation capacitor 60 are provided with the mechanical breaker 10 and the commutation capacitor 60 during the period from the time td to the time te when the 3/4 cycle of the resonance frequency elapses. A commutation current L3 with a resonance frequency of less than 3/4 wave flows, and a zero point is generated at time te. Further, as shown by the waveform W32, since the commutation capacitor 60 acts and the commutation current L3 flows, the capacitor voltage decreases from the time td to the time te.

[Electrical circuit breaker 10]
FIG. 6 is a diagram showing a state of the DC circuit breaker 1 in which the mechanical circuit breaker 10 is electrically controlled to be in the open state. The control unit 100 electrically controls the mechanical circuit breaker 10 in an open state when a zero point is generated in the commutation current L3 flowing through the mechanical circuit breaker 10 at time te. The control unit 100 electrically controls the mechanical circuit breaker 10 in an open state by extinguishing the arc by, for example, gas shutoff or vacuum cutoff when a zero point is generated. Further, as shown in FIG. 6, as the mechanical circuit breaker 10 is electrically controlled to be in the open state, the DC system current is changed from the first DC transmission line LN1 to the first disconnector 20 and the commutation switch. It flows to the second DC transmission line LN2 through the path of 50, the commutation capacitor 60, the commutation reactor 70, and the second disconnector 30. The state of each part at this time is as follows.
-Mechanical circuit breaker 10: Open mechanically and electrically-Lightning arrester 15: Stopped-First disconnector 20: Closed-Second disconnector 30: Closed-Commuting switch 50: Closed- Surge switch 80: Closed state / commutation capacitor 60: Discharged state

As the waveform W10 in FIG. 12 shows, the arc of the mechanical circuit breaker 10 is extinguished at time te, and after time te, the mechanical circuit breaker 10 is controlled to be in an open state both mechanically and electrically. Further, as shown by the waveform W30, since a transient recovery voltage is generated between the electrodes of the mechanical circuit breaker 10 that is mechanically and electrically controlled to be in the open state, the lightning arrester 15 is moved from time te. The voltage between the electrodes of the mechanical circuit breaker 10 rises until it operates (until the time tf described later). Further, as shown by the waveform W24, a direct current system current flows in the commutation capacitor 60 from the time te until the lightning arrester 15 operates. Therefore, as shown by the waveform W32, the capacitor voltage rises from the time te until the lightning arrester 15 operates.

[Operation of lightning arrester 15]
FIG. 7 is a diagram showing a state of the DC circuit breaker 1 in which the lightning arrester 15 is operated. As described above, since the transient recovery voltage is generated between the electrodes of the mechanical circuit breaker 10 after the time te, the voltage applied between the electrodes of the mechanical circuit breaker 10 (that is, it is applied to both ends of the lightning arrester 15). Voltage) rises. Then, the voltage between the electrodes of the mechanical circuit breaker 10 reaches the operating voltage of the lightning arrester 15, and the lightning arrester 15 operates. As the lightning arrester 15 operates, the DC system current flows from the first DC transmission line LN1 to the second DC transmission line LN2 via the paths of the first disconnector 20, the lightning arrester 15, and the second disconnector 30. The state of each part at this time is as follows.
-Mechanical circuit breaker 10: Open mechanically and electrically-Lightning arrester 15: Operating state-First disconnector 20: Closed-Second disconnector 30: Closed-Commuting switch 50: Closed- Surge switch 80: Closed state / commutation capacitor 60: Almost no charge / discharge

As the waveform W30 of FIG. 12 shows, the voltage between the electrodes of the mechanical circuit breaker 10 reaches the operating voltage of the lightning arrester 15 at time tf. Then, as shown by the waveform W26, the lightning arrester 15 starts operating at time tf and absorbs the recovery voltage. Therefore, as shown by the waveform W26, the current flowing through the lightning arrester 15 that has increased sharply at the time tf gradually decreases from the time tf to the time tg, and becomes 0 [A] at the time tg. Along with this, as the waveform W20 shows, the DC system current gradually decreases from the time tf to the time tg.

At this time, almost no DC system current flows from the first DC transmission line LN1 in the direction of the commutation circuit 40. Therefore, the voltage between the electrodes of the mechanical circuit breaker 10 shown by the waveform W30 and the capacitor voltage shown by the waveform W32 hold the values at the timing of the time tf from the time tf to the time tg. As the waveform W16 shows, the arc generated between the electrodes of the commutation switch 50 is extinguished from the time tf to the time tg.

[Charging the commutation capacitor 60]
FIG. 8 is a diagram showing a state of the DC circuit breaker 1 controlled in a state of charging the commutation capacitor 60. When the lightning arrester 15 finishes suppressing the recovery voltage, the DC system current is changed from the first DC transmission line LN1 to the first disconnector 20, the commutation switch 50, the commutation condenser 60, the commutation reactor 70, and the second disconnector 30. It flows to the second DC transmission line LN2 via the path of. The state of each part at this time is as follows.
-Mechanical circuit breaker 10: Open mechanically and electrically-Lightning arrester 15: Stopped-First disconnector 20: Closed-Second disconnector 30: Closed-Commuting switch 50: Closed- Surge switch 80: Closed state / commutation capacitor 60: Charged state

As shown by the waveform W20 in FIG. 12, the DC system current oscillates from the time tg to the time th when the commutation capacitor 60 ends the transient vibration. The vibration of the DC system current is damped as the transient vibration subsides. Therefore, the DC system current gradually converges from the time tg to the time th. Further, as shown by the waveform W24, a DC system electric voltage vibrating due to transient vibration flows through the commutation capacitor 60. Therefore, as shown by the waveform W32, the capacitor voltage gradually converges to a predetermined voltage while oscillating due to transient vibration from time tg to time th. The predetermined voltage is a voltage that matches or substantially matches the first voltage VDC1.

The period from time tg to time th is an example of the reclosing time. The reclosing time is the time from when the DC circuit breaker 1 electrically cuts off the first DC transmission line LN1 and the second DC transmission line LN2 until it is electrically conducted again. As described above, the capacitance of the commutation capacitor 60 and the value of the commutation reactor 70 ensure the predetermined reclosing time, and the transient vibration converges within a range not exceeding the predetermined maximum value of the reclosing time. Is set.

Here, before the capacitor voltage converges to a predetermined voltage, the insulation performance between the electrodes of the commutation switch 50 is restored, the arc of the commutation switch 50 is cut, or the arc is extinguished by the zero point of the current. It may arc and become open. In this case, the commutation capacitor 60 is charged to a predetermined voltage by the DC system current flowing from the first DC transmission line LN1 to the second DC transmission line LN2 via the path of the surge switch 80 and the surge resistance 90.

[Open state of commutation switch 50]
FIG. 9 is a diagram showing a state of the DC circuit breaker 1 in which the commutation switch 50 is controlled to be in the open state. The control unit 100 determines whether or not the capacitor voltage of the commutation capacitor 60 is a predetermined voltage after the time tg. For example, when the transient vibration of the DC system current has converged, the control unit 100 determines that the commutation capacitor 60 has been charged to a predetermined voltage. When the control unit 100 determines that the commutation capacitor 60 has been charged to a predetermined voltage, the control unit 100 controls the commutation switch 50 to be in the open state. The state of each part at this time is as follows.
・ Mechanical circuit breaker 10: Open mechanically and electrically ・ Lightning arrester 15: Stopped ・ First disconnector 20: Closed ・ Second disconnector 30: Closed ・ Commuting switch 50: Open ・Surge switch 80: Closed state / commutation capacitor 60: Charged state

As shown by the waveform W20 in FIG. 12, the control unit 100 determines that the commutation capacitor 60 has been charged to a predetermined voltage at time th, and controls the commutation switch 50 to be in the open state.

[DC system cutoff]
FIG. 10 is a diagram showing a state of the DC circuit breaker 1 in which the first disconnector 20 and the second disconnector 30 are controlled to be in the open state. FIG. 11 is a diagram showing a state of the DC circuit breaker 1 in which the surge switch 80 is controlled to be in the open state. The control unit 100 controls the commutation switch 50 to be in the open state, and then controls the first disconnector 20 and the second disconnector 30 to be in the open state. Then, the control unit 100 controls the first disconnector 20 and the second disconnector 30 in the open state, and then controls the surge switch 80 in the open state. The state of each part in the scene of FIG. 11 is as follows.
-Mechanical circuit breaker 10: Mechanically and electrically open state-Lightning arrester 15: Stopped state-First disconnector 20: Open state-Second disconnector 30: Open state-Commutation switch 50: Open state- Surge switch 80: Open state / commutation capacitor 60: Charged state

As shown by the waveform W12 in FIG. 12, the control unit 100 controls the first disconnector 20 and the second disconnector 30 in the open state at time ti. Further, as shown by the waveform W12, the control unit 100 controls the surge switch 80 to be in the open state at time tj.

The control unit 100 may control the first disconnector 20 and the second disconnector 30 in the open state after controlling the surge switch 80 in the open state, and the first disconnector 20 and the second disconnector 20 may be controlled in the open state. The vessel 30 may be controlled to the open state in order.

[Operation flow]
FIG. 13 is a flowchart showing an example of the operation of the DC circuit breaker 1. First, the control unit 100 determines whether or not a cutoff instruction signal indicating that the first DC power transmission line LN1 and the second DC power transmission line LN2 are electrically cut off has been received from the detection device (step S100). .. The control unit 100 waits until the cutoff instruction signal is received from the detection device. When the control unit 100 receives the cutoff instruction signal, the control unit 100 controls the mechanical circuit breaker 10 in the open state (step S102). Next, the control unit 100 controls the surge switch 80 to be in the closed state (step S104). At this time, the surge generated by controlling the surge switch 80 to the closed state is suppressed by the surge resistance 90.

Next, the control unit 100 controls the commutation switch 50 to be in the closed state (step S106). At this time, since the surge is sufficiently suppressed by the surge resistance 90, the surge does not occur even when the commutation switch 50 is closed, or the peripheral circuit elements and other peripheral devices do not malfunction or break down. Surge is sufficiently suppressed. Further, as the commutation switch 50 is controlled to the closed state, the loop of the mechanical circuit breaker 10, the commutation reactor 70, the commutation capacitor 60, and the commutation switch 50 is charged in advance in the DC circuit breaker 1. The capacitor voltage of the commutation capacitor 60 and the commutation reactor 70 act on each other, and the commutation current L3 resonates with the resonance frequency corresponding to the capacitor component of the commutation capacitor 60 and the reactor component of the commutation reactor 70. Flows.

The control unit 100 electrically controls the mechanical circuit breaker 10 in an open state when a zero point is generated in the resonant commutation current L3 flowing through the mechanical circuit breaker 10 (step S108). Since the mechanical circuit breaker 10 is electrically controlled to be in the open state, a transient recovery voltage is generated between the electrodes of the mechanical circuit breaker 10, so that the voltage applied between the electrodes of the mechanical circuit breaker 10 is generated. (That is, the voltage applied to both ends of the lightning arrester 15) rises. Then, the voltage between the electrodes of the mechanical circuit breaker 10 reaches the operating voltage of the lightning arrester 15, and the lightning arrester 15 operates (step S110).

As the lightning arrester 15 operates, the DC system current flows from the first DC transmission line LN1 to the second DC transmission line LN2 via the paths of the first disconnector 20, the lightning arrester 15, and the second disconnector 30. The DC system current vibrates until the commutation capacitor 60 finishes the transient vibration. The DC system current is damped as the transient oscillations subside. Further, since a direct current system current flows through the commutating capacitor 60 in the charging direction, the capacitor voltage gradually converges to a predetermined voltage while vibrating due to transient vibration. The predetermined voltage is a voltage that matches or substantially matches the DC voltage supplied by the DC system such as the first DC transmission line LN1 and the second DC transmission line LN2.

The control unit 100 determines whether or not the capacitor voltage of the commutation capacitor 60 is a predetermined voltage (step S112). For example, when the transient vibration of the DC system current has converged, the control unit 100 determines that the commutation capacitor 60 has been charged to a predetermined voltage. The control unit 100 stands by until the commutation capacitor 60 is charged to a predetermined voltage. When the control unit 100 determines that the commutation capacitor 60 has been charged to a predetermined voltage, the control unit 100 controls the commutation switch 50 to be in the open state (step S114). Next, the control unit 100 controls the disconnector to the open state (step S116). Next, the control unit 100 controls the surge switch 80 to be in the open state (step S118). As a result, the DC circuit breaker 1 can electrically cut off the first DC transmission line LN1 and the second DC transmission line LN2.

[Summary of Embodiment]
As described above, the DC circuit breaker 1 of the embodiment includes a mechanical circuit breaker 10, a lightning arrester 15, and a commutation circuit 40. In the mechanical circuit breaker 10, the first terminal 10a is connected to the first DC transmission line LN1 via the first disconnector 20, and the second terminal 10b is connected to the second DC transmission line LN2 via the second disconnector 30. Be connected. The commutation circuit 40 includes a commutation switch 50, a commutation capacitor 60, a commutation reactor 70, a surge switch 80, and a surge resistor 90. The commutation circuit 40, the lightning arrester 15, and the mechanical circuit breaker 10 are connected in parallel to each other between the first DC transmission line LN1 and the second DC transmission line LN2. The commutation switch 50, the commutation capacitor 60, and the commutation reactor 70 are connected in series between the first DC transmission line LN1 and the second DC transmission line LN2. A surge switch 80 and a surge switch 80 connected in series are provided in parallel with a commutation switch 50.

Here, when the series circuit of the surge switch 80 and the surge resistor 90 is not provided in parallel with the commutation switch 50, the commutation switch 50 is set before the capacitor voltage converges to a predetermined voltage. The insulation performance between the electrodes may be restored, and the commutation switch 50 may be opened. If the commutation switch 50 is opened before the capacitor voltage converges to a predetermined voltage, the next time the first DC transmission line LN1 and the second DC transmission line LN2 are cut off, the commutation switch 50 is opened. There are cases where the commutation capacitor 60 is not charged with enough power to pass a sufficient commutation current L3, or the commutation capacitor 60 is overcharged with enough power to pass an excess commutation current L3.

When the capacitor voltage is larger than the voltage of the DC system (that is, the commutation capacitor 60 is overcharged), the resonant commutation current L3 becomes large and flows to the mechanical circuit breaker 10 during the period from time td to te. The current change rate (di / dt) at the current zero point may increase. Depending on the performance of the mechanical circuit breaker 10, the commutation current L3 having a large current change rate (di / dt) cannot be electrically opened, and the first DC transmission line LN1 and the second DC power transmission There is a possibility that the interruption with the line LN2 will fail.

On the other hand, when the capacitor voltage is smaller than the voltage of the DC system (that is, the commutation capacitor 60 is insufficiently charged), the resonant commutation current L3 at the time of reclosing is reduced, and the mechanical circuit breaker 10 is used. The zero point cannot be generated by the commutating current L3 that flows, and there is a possibility that the disconnection between the first DC transmission line LN1 and the second DC transmission line LN2 fails.

According to the DC breaker 1 of the embodiment, the series circuit of the surge switch 80 and the surge resistance 90 is provided in parallel with the commutation switch 50, so that the current between the electrodes of the commutation switch 50 is increased. Even if the arc is cut or extinguished at the zero point of the current, the DC system current continues to flow through the surge switch 80 and the surge resistor 90 in the commutation capacitor 60, so that the commutation capacitor 60 is surely brought to a predetermined voltage. It can be charged. Therefore, the DC circuit breaker 1 of the present embodiment can appropriately reclose the circuit while suppressing the surge.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... DC disconnector, 10 ... Mechanical disconnector, 10a, 20a, 30a, 40a, 50a, 80a ... First terminal, 10b, 20b, 30b, 40b, 50b, 80b ... Second terminal, 15 ... Lightning striker, 20 ... 1st disconnector, 30 ... 2nd disconnector, 40 ... commutation circuit, 50 ... commutation switch, 60 ... commutation capacitor, 70 ... commutation reactor, 80 ... surge switch, 90 ... surge resistance, 100 ... control Unit, L3 ... commutation current, LN1 ... first DC transmission line, LN2 ... second DC transmission line

Claims

A mechanical circuit breaker whose first end is connected to the first DC transmission line and whose second end is connected to the second DC transmission line.
With a lightning arrester
A commutation circuit having a first switch, a second switch, a reactor, a capacitor, and a resistor is provided.
The commutation circuit, the lightning arrester, and the mechanical circuit breaker are connected in parallel to each other between the first DC power transmission line and the second DC power transmission line.
The first switch, the capacitor, and the reactor are connected in series between the first DC power transmission line and the second DC power transmission line.
A switch in which the second switch and the resistor are connected in series is provided in parallel with the first switch.
DC circuit breaker.
A control unit for controlling the open / closed state of the first switch is further provided.
The first switch is a non-contact switch having a pair of fixed electrodes.
The control unit controls the non-contact switch to the closed state by lowering the insulation performance between the electrodes as compared with the open state and causing dielectric breakdown.
The DC circuit breaker according to claim 1.
A control unit for controlling the open / closed state of the first switch is further provided.
The first switch is a contact type switch having a pair of electrodes.
The control unit controls the contact type switch to be in the closed state by moving at least one of the electrodes to bring the distance between the electrodes closer, lowering the insulation performance between the electrodes from the open state and causing dielectric breakdown. To do,
The DC circuit breaker according to claim 1.
When at least one of the electrodes is moved, the control unit does not bring the electrodes into contact with each other and moves them to a position separated by a predetermined distance.
The DC circuit breaker according to claim 3.
The capacitor is charged by applying the system voltage of the DC system supplied to the first DC transmission line or the second DC transmission line.
The DC circuit breaker according to any one of claims 1 to 4.
The capacitor is charged by applying a voltage supplied from another device and equivalent to the system voltage of the DC system supplied to the first DC transmission line or the second DC transmission line. Be done,
The DC circuit breaker according to any one of claims 1 to 4.
A control unit for controlling the open / closed state of the first switch is further provided.
The reactor and the capacitor are systems of a DC system supplied to the first DC power transmission line or the second DC power transmission line as the first switch is controlled to a closed state by the control unit. The current is resonated by the resonance frequency to generate a zero point in the system current.
The DC circuit breaker according to any one of claims 1 to 6.
A control unit for controlling the open / closed state of the mechanical circuit breaker, the first switch, and the second switch is further provided.
The control unit
The mechanical circuit breaker is opened and the control for electrically shutting off the first end and the second end is started.
After starting the control to open the mechanical circuit breaker, the second switch is controlled to be closed.
After controlling the second switch to the closed state, the first switch is controlled to the closed state.
After controlling the first switch to the closed state, the reactor and the capacitor resonate the system current of the DC system supplied to the first DC transmission line or the second DC transmission line by the resonance frequency. At the zero point generated by the above, the first end and the second end of the mechanical circuit breaker are electrically cut off.
When the voltage of the capacitor becomes a voltage equivalent to the system voltage of the DC system, the second switch is controlled to be in the open state.
After controlling the second switch to the open state, the first switch is controlled to the open state.
The lightning arrester limits the voltage generated between the first end and the second end as the mechanical circuit breaker is electrically cut off.
The DC circuit breaker according to any one of claims 1 to 7.