JP2006260925A - Direct current high speed vacuum circuit breaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably shut off a large direct current, to completely cut off a circuit after shutdown, and to prolong a contact service life of a vacuum bulb. <P>SOLUTION: This direct current high speed vacuum circuit breaker composed by connecting in series, a first serial circuit with a commutation capacitor 1, a thyristor 2 and a commutation reactor 3 is connected in parallel to a second serial circuit with the vacuum bulb 4 and a saturable reactor 6 serially connected, and a capacitor 7 is connected with the saturable reactor 6 in parallel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a DC high-speed vacuum shut-off device using a vacuum valve that is installed mainly in a DC substation for electric railways and shuts off a main circuit and protects a power supply circuit in the event of an overhead wire short circuit accident.

  2. Description of the Related Art Conventionally, for example, in a DC substation for electric railways, a DC high-speed vacuum shut-off device using a vacuum valve has been installed to protect a power supply circuit in the event of an overhead wire short circuit accident.

  FIG. 4 shows a circuit configuration of such a conventional DC high-speed vacuum interrupter.

  This DC high-speed vacuum circuit breaker is a first series in which a commutation capacitor 1, a commutation switch 2 (hereinafter often referred to as a thyristor because a thyristor is often used), a commutation reactor, or a floating inductance 3 of wiring is connected in series. A saturable reactor 6 is connected in series to a parallel connection circuit of a circuit, a vacuum valve 4 that cuts off direct current, a nonlinear resistor 5 that absorbs energy stored in the inductance of the vacuum valve 4 and wiring, and a snubber capacitor 8. The two series circuits are connected in parallel, and are provided in a main circuit that connects a power supply circuit (not shown) and an overhead line.

  FIG. 5 shows a circuit configuration of a DC high-speed vacuum interrupter using a mechanical switch in place of the thyristor, and the other configuration is exactly the same as FIG. 4 (for example, Patent Document 1).

  Next, the operation of the DC high-speed vacuum interrupter shown in FIG. 4 will be described.

  It is assumed that the main circuit current I is flowing through the vacuum valve 4 and that the commutation capacitor 1 is charged to the illustrated polarity by a charging circuit (not illustrated) in advance.

  In such a state, when a shut-off signal is given to the vacuum valve 4 from the outside, or when it is detected that an abnormal current is flowing in the main circuit by current detection means (not shown), the vacuum valve 4 is first opened. Immediately after that, the thyristor 2 is ignited.

  Then, a series resonance circuit is formed by a loop of the commutation capacitor 1, the vacuum valve 4, the saturable reactor 6, the thyristor 2, the commutation reactor 3, and the commutation capacitor 1, and the resonance current is generated by the electric charge stored in the commutation capacitor 1. Flows.

  The values of commutation capacitor 1 and commutation reactor 3 and the initial charging voltage of commutation capacitor 1 are determined so that the maximum value of this current is larger than the predicted maximum value of main circuit current.

  After the opening of the vacuum valve, the main circuit current continues to flow as an arc. At this time, since the resonance current is larger than the main circuit current, the current in the vacuum valve passes the zero point and tries to reverse the polarity. At this time, the saturable reactor 6 is released from saturation and becomes a high inductance, and the rate of change of current is weakened.

  Near the time t2 when the current passes near the zero point, the arc in the vacuum valve 4 disappears, and the insulation is restored in the gap to generate a voltage. The voltage generated in the vacuum valve 4 is substantially equal to the voltage of the commutation capacitor 1. The voltage of the commutation capacitor 1 continues to increase in the opposite direction due to the energy stored in the stray inductance existing in the reactor 3 of the commutation circuit and the power supply and load of the main circuit.

  When this voltage increases to some extent, a current flows through the nonlinear resistor 5. Since the energization threshold voltage of the non-linear resistance 5 is set higher than the power supply voltage, the main circuit current attenuates and eventually becomes zero, and the interruption is completed.

  In the DC high-speed vacuum cutoff device shown in FIG. 5 as well, a mechanical switch 21 is used instead of a thyristor as a switch for flowing a resonance current, and the cutoff operation is exactly the same as described above.

  FIG. 6 shows current / voltage waveforms at various points when the short-circuit fault current is interrupted.

  In FIG. 6, when a short circuit accident occurs at time t0, the vacuum valve 4 starts opening at time t1, and the current flowing through the vacuum valve 4 by the resonance current becomes zero at time t2. When the current starts to flow through the non-linear resistance 5 at time t3, the main circuit current gradually decreases, and at time t4, the main circuit current becomes zero and the interruption is completed.

  FIG. 7 is an explanatory diagram of the operation in the vicinity of passing through the zero point of the vacuum valve among the operation waveforms shown in FIG. 6, (a) is an equivalent circuit near time t2, and (b) is an enlarged waveform of the time axis. is there.

  When the current IVSC of the vacuum valve decreases and comes close to the zero point, the saturable reactor 6 is released from saturation, and thus shows a large inductance.

  As a result, the inductance of the saturable reactor is dominant in the inductance of the circuit, and the inductance of the commutation reactor 3 may be ignored. Therefore, the equivalent circuit is as shown in FIG. At this time, the voltage VC of the commutation capacitor is almost applied to the saturable reactor, and VC = VSL.

  After that, when the arc of the vacuum valve is extinguished and the insulation between the poles is restored, the IVSC rapidly decreases to zero. As a result, the voltage VSL applied to the saturable reactor also becomes zero, but a large voltage is instantaneously induced between the terminals of the saturable reactor due to the current change at this time, and this voltage is applied between the electrodes of the vacuum valve.

At the same time, since the voltage of the commutation capacitor is also applied between the electrodes of the vacuum valve, the voltage VVSC between the electrodes of the vacuum valve increases rapidly. At the time when this voltage is applied, the arc of the vacuum valve has just disappeared, the insulation is incomplete, and the distance between the poles is small, so that the arc may recur and fail to shut off. In particular, when a large accident current is interrupted, the arc energy due to the accident current is large, and re-arcing is likely to occur. Moreover, since it is necessary to cut off in a state where the distance between the poles is not sufficiently secured in order to realize high-speed cut-off, the re-arcing is easier. In order to prevent this, a snubber capacitor 8 is provided. The snubber capacitor suppresses an increase in the inter-electrode voltage VVSC of the vacuum valve and changes as shown by a dotted line in the figure.
JP-A-4-259719

  As described above, the conventional DC high-speed vacuum circuit breaker has a problem that even after completion of the circuit breakage, current flows through the snubber capacitor 8 and the load and the power source cannot be completely insulated.

  FIG. 8 shows a circuit configuration including a power source and a load when a conventional DC high-speed vacuum circuit breaker is applied as a high-speed circuit breaker of a DC power source for electric railways or the like. In FIG. 8, 9 is a diode rectifier and 10 is a train load.

  Usually, the direct current output voltage of a diode rectifier is not perfect direct current but includes a considerably large ripple voltage. Since this ripple voltage is an alternating current component and the capacitor has a low impedance with respect to the alternating current component, an alternating current flows through the snubber capacitor 8 along the route of the solid arrow 11 even in an open state. As a result, the circuit is not completely opened, and there is a problem that an unnecessary voltage is applied to the load.

  Furthermore, since the snubber capacitor 8 is charged to the illustrated polarity by the rectifier 9, the charge charged in the capacitor 8 is discharged along the route indicated by the dotted arrow 12 when the vacuum valve 4 is next turned on. And for a while, the mechanical vibration is generated at the contact point of the vacuum valve 4 to repeat the contact state and the non-contact state. At this time, the capacitor charge is discharged and the contact point becomes rough and the life is shortened. There was also a problem.

  The present invention has been made to solve the above problems, and can prevent a rapid increase in the interelectrode voltage that occurs simultaneously with the extinction of the arc of the vacuum valve. An object of the present invention is to provide an inexpensive direct-current high-speed vacuum interrupter capable of realizing a simple interrupted state and preventing rough contact of the vacuum valve at the time of charging.

  In order to achieve the above object, the present invention provides a first series circuit in which a first capacitor, a switch and an inductance are connected in series, and a second series circuit in which a vacuum valve and a saturable reactor are connected in series. Are connected in parallel, and a second capacitor is connected in parallel to the saturable reactor.

  According to the present invention, it is possible to prevent the voltage between the electrodes of the vacuum valve from rising rapidly by flowing the current flowing through the saturable reactor immediately after the current interruption to the parallel capacitor, and gradually discharging the capacitor. Without re-arcing, a large current can be shut off stably, and the circuit can be completely disconnected with a vacuum valve after the shut-off. Furthermore, since the electric charge of the capacitor is discharged through the saturable reactor after being cut off, the capacitor discharge current does not flow when the vacuum valve is turned on again, preventing contact roughening and extending the life.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit configuration diagram showing a first embodiment of a DC high-speed vacuum interrupter according to the present invention, and the same components as those in FIG.

  As shown in FIG. 1, a first series circuit in which a commutation capacitor 1, a thyristor 2 and a commutation reactor 3 are connected in series, and a second series circuit in which a vacuum valve 4 and a saturable reactor 6 are connected in series. Are connected in parallel, a non-linear resistance 5 is connected in parallel to the vacuum valve 4, and a capacitor 7 is connected in parallel to the saturable reactor 6.

  Next, the operation will be described.

  It is assumed that the main circuit current is flowing through the vacuum valve 4 and that the commutation capacitor 1 is charged to the illustrated polarity in advance by a charging circuit (not illustrated).

  In such a state, when a shut-off signal is given to the vacuum valve 4 from the outside, or when it is detected that an abnormal current is flowing in the main circuit by current detection means (not shown), the vacuum valve 4 is first opened. Immediately after that, the thyristor 2 is ignited.

  Then, a series resonance circuit is formed by a loop of the commutation capacitor 1, the vacuum valve 4, the saturable reactor 6, the thyristor 2, the commutation reactor 3, and the commutation capacitor 1, and the resonance current is generated by the electric charge stored in the commutation capacitor 1. Flows.

  The values of commutation capacitor 1 and commutation reactor 3 and the initial charging voltage of commutation capacitor 1 are determined so that the maximum value of this current is larger than the predicted maximum value of main circuit current.

  After the opening of the vacuum valve 4, the main circuit current I continues to flow as an arc, but at this time, the resonance current flows superimposed on the main circuit current, and the maximum value of the resonance current is larger than the main circuit current. The current in the valve 4 approaches zero, the saturable reactor 6 is released from saturation, and the current passes through the zero point at a slower rate of change.

  FIGS. 2A and 2B are diagrams for explaining the operation in the vicinity of the current passing through the zero point of the vacuum valve, where FIG. 2A is an equivalent circuit near time t2, and FIG. 2B is an enlarged waveform of the time axis.

  At the moment when the current IVSC becomes zero, the arc in the vacuum valve 1 is extinguished, the insulation between the valve poles is restored, and the voltage VVSC is generated. At this time, the current IVSC of the vacuum valve suddenly changes to zero. As a result, the current of the saturable reactor flows through the capacitors connected in parallel and decreases with the discharge of the capacitor due to this current, so that the rate of change of the terminal voltage VSL is suppressed.

  Furthermore, since the voltage VVSC between the electrodes of the vacuum valve is substantially equal to the difference voltage between the commutation capacitor voltage VC and the saturable reactor voltage VSL, the voltage increase rate of the voltage VVSC between the electrodes is suppressed, and even after the large current is cut off. No re-arcing.

  As described above, in this embodiment, the snubber capacitor 8 connected in parallel to the vacuum valve 4 is removed, and the capacitor 7 is connected in parallel to the saturable reactor 6, thereby obtaining the following effects. it can.

  That is, when the DC high-speed vacuum circuit breaker is applied as a high-speed circuit breaker for a DC power source for electric railways or the like, in the conventional circuit configuration, as shown by the solid line arrow in FIG. Since a small current flows through the power source side and the load side through 8, the circuit could not be completely disconnected. However, in the present embodiment, such a circuit as indicated by the solid line arrow is not configured, so the vacuum valve 4 After disconnection is complete, the circuit can be completely disconnected.

  Furthermore, since the electric charge of the capacitor 7 is discharged through the saturable reactor 6 as shown in FIG. 3 after completion of the interruption as described above, the electric charge of the capacitor 7 is changed to the vacuum valve when the vacuum valve 4 is turned on next time. There is no discharge through 4. Therefore, roughening of the vacuum valve contact due to the discharge current can be prevented, so that the life of the vacuum bulb can be extended.

The circuit block diagram which shows 1st Embodiment of the high-speed vacuum interrupter by this invention. In the same embodiment, it is a figure for demonstrating the operation | movement of the vicinity which passes the electric current zero point of a vacuum valve, (a) is an equivalent circuit schematic of the electric current zero point vicinity vicinity, (b) is an enlarged waveform figure of a time-axis. . The figure which shows the electric current path after completion | finish of interruption | blocking in the same embodiment. The circuit block diagram which shows an example of the conventional high-speed vacuum interrupter. The circuit block diagram which shows the other example of the conventional high-speed vacuum interrupter. The wave form diagram of each part for demonstrating the operation | movement at the time of interruption | blocking of a conventional apparatus. 6A and 6B are diagrams for explaining the operation of the vacuum valve near the current zero point, where FIG. 6A is an equivalent circuit diagram near time t2, and FIG. 6B is an enlarged waveform diagram of the time axis. The figure which shows the electric current path after completion | finish of interruption | blocking in a conventional apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Commutation capacitor, 2 ... Thyristor, 3 ... Commutation reactor, 4 ... Vacuum valve, 5 ... Nonlinear resistance, 6 ... Saturable reactor, 7 ... Capacitor, 8 ... Snubber capacitor, 9 ... Diode rectifier, 10 ... Load

Claims (1)

  A first series circuit in which a first capacitor, a switch, and an inductance are connected in series, and a second series circuit in which a vacuum valve and a saturable reactor are connected in series are connected in parallel, and the saturable reactor is connected to the saturable reactor. A direct-current high-speed vacuum circuit breaker characterized in that a second capacitor is connected in parallel.

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