JPH09231877A - Direct current circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shut off a small current in a short time without influencing the breaking operation of a large current to be required in the event of short- circuiting, etc., of a track by forming the second circuit consisting of a capacitor and reactor in series connection, and connecting this second circuit parallel with a vacuum valve. SOLUTION: The second circuit 5a consisting of a series connection of a capacitor 2a and reactor 3a is connected parallel with a vacuum valve 1 and a commutator circuit 5. When a turn-on comand S2 is given from a control circuit 11, a commutation switch 4 is closed, and a current starts flowing from a commutation capacitor 2. The combined impedance of the capacitor 2a and reactor 3a has a significant value, and the current from the capacitor 2 flows to the valve 1, wherein the current to the valve 1 will be such as directed oppositely to the load current on which a high-frequency discharge current is superposed. Accordingly a small current can be shut off in a short time without influencing the breaking operation of a large current if the impedance of the second circuit 5a is made over several tens of times greater than the commutator circuit 5 while the capacitance of the circuit 5a is made below several percent of the circuit 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when a vacuum valve is opened, superimposes a high-frequency discharge current from a commutation circuit connected in parallel with the vacuum valve on the current flowing through the vacuum valve to cut off a direct current. The present invention relates to the structure of a DC circuit breaker.

[0002]

2. Description of the Related Art FIGS. 3 to 5 show a conventional DC circuit breaker, FIG. 3 shows a circuit configuration example of the DC circuit breaker, and FIG. 5 is a waveform diagram of current and voltage, and FIG. 5 is a waveform diagram when a small current is cut off. A DC circuit breaker used to protect against ground faults and short-circuit accidents in electric railway power supply lines is provided with a capacitor in parallel with the vacuum valve, and by supplying discharge current from this capacitor, the vacuum valve at the time of interruption can be It has a structure that cuts off by causing a current zero point in the flowing fault current.

Conventionally, a DC circuit breaker of this type has a vacuum valve 1 and a capacitor (commutation capacitor) 2 and a reactor (commutation reactor) 3 connected in parallel to the vacuum valve 1 as shown in FIG. And a switch (commutation switch) 4 connected in series, and a non-linear resistance 7 for suppressing an overvoltage generated between the contacts of the vacuum valve 1 after being cut off. A charging circuit 6 connected to the line, a current detector 10 for detecting the line current of the main circuit which flows out of the DC power source 8 of the line and passes through the vacuum valve 1 to the load 9, and the line detected by the current detector 10. An opening command S ₁ for shutting off the vacuum valve 1 when the current reaches a predetermined magnitude due to a short circuit of the line or the like.
And a control circuit 11 for issuing a closing command S ₂ for parallelizing the commutation circuit 5 with the vacuum valve 1 in order to make a zero point in the passing current of the vacuum valve 1.

The operation at the time of fault current interruption by the DC circuit breaker having the above configuration will be described based on the time-series current and voltage waveform characteristics in the DC circuit breaker configuration section shown in FIG. In (a), when an accident occurs, a fault current flows through the line, and when the value detected by the current detector 10 becomes equal to or greater than the set value, the control circuit 11 gives an opening command S ₁ to the vacuum valve 1. (B) At the time when the vacuum valve 1 is opened, an arc is generated between the electrodes of the vacuum valve 1. (C) At the time when the commutation switch 4 is closed by the closing command S ₂ from the control circuit 11 and the current from the commutation capacitor 2 charged by the charging circuit 6 starts to flow. The discharge current, which is in the opposite direction to the fault current, flows from the commutation capacitor 2 through the commutation reactor 3 and a superimposed current flows. (D) It is the time when the vacuum valve 1 is extinguished, and then the fault current flows from the DC power supply 8 through the commutation circuit 5, the commutation capacitor 2 is charged by this current, and the voltage of the commutation capacitor 2, that is, the contact opening. The inter-electrode voltage of the vacuum valve 1 is increased. (E) It is the time when the inter-electrode voltage of the vacuum valve 1 reaches the operating voltage of the non-linear resistance 7 and the current commutates to the non-linear resistance 7 and begins to flow. (F) The commutation switch 4 is generally composed of a thyristor, a discharge gap or the like, and opens when the current of the commutation circuit 5 becomes zero. (G) Since the energy stored in the inductance of the circuit is consumed by the non-linear resistor 7, the current decreases and the current in the main circuit becomes zero, thus completing the interruption.

[0005]

The operation of the DC circuit breaker in the case of interrupting a high-current fault current such as a line short-circuit fault by the vacuum valve has been described above. However, the load current, especially several A to several When attempting to interrupt the line current of about 10 A, the commutation from the commutation circuit 5 to the non-linear resistance 7 as in the case of interruption of the fault current does not occur, and depending on the condition of the load 9, the commutation to the commutation capacitor 2 is performed. The applied current is several seconds to several tens.
It may continue to flow for more than a second. This state will be described based on the current and voltage waveform characteristics in the circuit breaker component shown in FIG. 5, as in the above. (B ') is the time when the vacuum valve 1 is opened, and at the time (C'), the commutation switch 4 of the commutation circuit 5 is closed to transfer the current from the commutation capacitor 2 to the vacuum valve 1. Shed. Then, at the time of (d '), the current of the vacuum valve 1 becomes zero and the vacuum valve 1 is extinguished and cut off. Although the current waveform diagram of the non-linear resistor 7 is omitted in FIG. 5, since the inter-electrode voltage of the vacuum valve 1 does not rise to the operating voltage of the non-linear resistor 7 when the small current is cut off, the above (d ') The current of the commutation capacitor 2 does not commutate to the non-linear resistance 7, but a current for charging the commutation capacitor 2 flows from the DC power supply 8 in a superposed manner. This current continues to flow until the voltage of the commutation capacitor 2 reaches the voltage of the DC power supply 8.

Usually, the commutation capacitor 2 has a very large capacity of about several thousand μF because it is necessary to supply a current equal to or higher than the fault current to the vacuum valve 1. Therefore, after the time point (d ') in FIG. 5, a small charging current continues to flow for a long time until the voltage of the commutation capacitor 2 reaches the voltage of the DC power supply 8 of the main circuit, and the load 9 is very light. In the case of load, it reaches several seconds to several tens of seconds. As described above, since the commutation switch 4 is generally composed of a thyristor, a discharge gap, or the like, and has no arc extinguishing means, the point where the current of the commutation capacitor 2 becomes zero is described above. If not, it will not close. In a state where such a current is continuously flowing, if the disconnector 12 provided for safety purposes on the load 9 side is opened for safety, an arc is generated from the disconnector 12, There is a problem that the worker is in a dangerous state and there is a risk that a ground fault may occur due to this arc.

Further, in order to ensure safety during inspection work on the load 9 side after the vacuum valve 1 is shut off, as shown in FIG. 6 of Japanese Patent Laid-Open No. 5-234471,
The blocking means 13 for blocking the flow of the commutation current from the commutation circuit 5 to the load 9 side is provided, and the blocking means 13 is opened by the opening command S ₁ of the control circuit 11 to open the vacuum valve 1 which is the main contact. A configuration has been proposed in which the commutation current is prevented from flowing into the load 9 side by opening the commutation switch 4 almost at the same time as or until the commutation switch 4 is closed by the closing command S ₂ . . However, in the DC circuit breaker having such a configuration, even if the blocking means 13 such as a vacuum valve is used, the current from the commutation capacitor 2 is cut by the blocking means 13 described above, so that an overvoltage is generated. There is a problem that it may affect other devices.

An object of the present invention is to solve the above problems, and to cut off a small current in a short time without affecting a breaking operation of a large current such as a fault current at the time of a line short circuit accident. To provide a container.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a vacuum for a DC circuit breaker provided with a commutation circuit consisting of a commutation capacitor, a commutation reactor and a commutation switch connected in series. A second circuit composed of a capacitor and a reactor connected in series was connected in parallel to the valve. As a result, even when the load current, especially the line current of a small current of about several A to several tens of A is cut off, after the vacuum valve is extinguished and opened by the discharge current from the commutation circuit,
By commutating the current that charges the commutation capacitor of the commutation circuit that flows from the DC power source to the second circuit that is connected in parallel to the vacuum valve, a zero point is formed in the current that flows in the commutation circuit. Since the switch can be opened, the current flowing to the load side can be attenuated by the second circuit. Since the blocking means for blocking the flow of the commutation current to the load side is not provided as described above, it is possible to obtain a DC circuit breaker that does not cause overvoltage due to current cutting.

Further, the impedance value of the second circuit composed of the condenser and the reactor connected in parallel to the vacuum valve is several tens of the impedance value of the commutation circuit composed of the commutation capacitor and the commutation reactance. It is assumed that the value of the capacitance of the capacitor of the second circuit is more than a factor of 2 and is less than several tenths of the value of the capacitance of the commutation capacitor of the commutation circuit. As a result, a small current can be interrupted in a short time without affecting the interrupting operation of a high-current accident current such as a line short-circuit accident.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a DC circuit breaker according to an embodiment of the present invention. FIG. 1 is a circuit configuration diagram of the DC circuit breaker, and FIG. 2 is a current and voltage waveform diagram of each part of the circuit breaker at the time of circuit break. As shown in FIG. 1, the present invention is configured by connecting a vacuum valve 1 and a commutation circuit 5 in parallel with a second circuit 5a in which a capacitor 2a and a reactor 3a are connected in series. Hereinafter, the operation of the DC circuit breaker having the circuit configuration shown in FIG. 1 when a small load current is interrupted will be described based on the current and voltage waveforms in the DC circuit breaker configuration section shown in FIG. (B ₁ ) is the time when the vacuum valve 1 is opened by the opening instruction S ₁ of the control circuit 11. (C ₁ ) It is the time when the commutation switch 4 is closed by the closing command S ₂ from the control circuit 11 and the current starts to flow from the commutation capacitor 2. In this case, since the combined impedance of the capacitor 2a and the reactor 3a of the second circuit 5a has a certain magnitude, the current from the commutation capacitor 2 flows to the vacuum valve 1 and the vacuum valve 1
A current in which a high-frequency discharge current in the opposite direction to the load current is superimposed flows through this. (D ₁ ) It is the time when the current of the vacuum valve 1 becomes zero, and the vacuum valve 1 is extinguished at this time. Therefore, up to this point, the operation is the same as that of the conventional configuration shown in FIG. 3 in which the second circuit 5a of the embodiment of the present invention is not provided. Commutation circuit 5 after the vacuum valve 1 is extinguished
An oscillating current flows between the second circuit 5a and the second circuit 5a. That is, the remaining voltage of the commutation capacitor 2 is used as a power source, and the commutation circuit 5 described above is used.
And an oscillating current forming a current zero flows through the closed loop of the second circuit 5a.

In the embodiment of the present invention, if the impedance of the second circuit 5a is set to be several tens of times greater than the impedance of the commutation circuit 5, that is,
Commutation capacitor 2 and commutation reactance 3 of commutation circuit 5
And the capacitor 2a and the reactance 3 of the second circuit 5a.
When the respective capacitance and inductance of a are C ₁ and L ₁ and C ₂ and L ₂ , (L
By setting ₂ / C ₂ ) ^1/2 >> (L ₁ / C ₁ ) ^1/2 , almost all the current flowing from the DC power supply 8 to the load 9 is the commutation circuit 5 of the commutation capacitor 2 and the commutation reactor 3. The current flowing through the commutation circuit 5 of the capacitor 2 and the commutation reactor 3 has a waveform obtained by combining the current flowing from the DC power source 8 to the load 9 and the oscillating current as shown in FIG. (F ₁ ) As described above, the zero point is formed by the oscillating current flowing in the commutation circuit 5. Therefore, when the thyristor is used as the commutation switch 4, if the gate pulse supply is stopped at an appropriate timing. , The thyristor extinguishes at the current zero point after this stop. The same applies to the gapless switch.

Then, because the commutation switch 4 is extinguished at the time point (f ₁ ) in FIG. 2 described above, a current for charging the capacitor 2a of the second circuit 5a flows from the DC power source 8 through the load 9. , This charging current is less than several tenths of the capacitance (C ₂ ) of the capacitor 2a compared to the capacitance (C ₁ ) of the commutation capacitor 2 (C ₁ >> C ₂ ).
As a result, the oscillating current is likely to be generated, and the decay time constant can be reduced, so that the capacitor 2a can reach the power supply voltage in a short time and the charging current can be reduced to zero. For example, the ratio commutation capacitor 2 capacitor 2a of the second circuit 5a (C ₂ / C ₁₎
Is set to a very small value of 1/100, a commutation current continuously flows for about several seconds in the conventional DC circuit breaker having a circuit configuration not including the second circuit 5a shown in FIG. Even if it is present, by providing the above-mentioned second circuit 5a, it can be significantly shortened to about several tens of milliseconds.

Then, the second circuit 5a of this embodiment is used.
Even in the case of a DC circuit breaker equipped with, in the case of interrupting a high-current fault current such as a line short-circuit accident, the vacuum valve 1 extinguishes and shuts off by the discharge current from the commutation circuit 5 as described above. After that, the current flowing from the DC power source 8 to the commutation capacitor 2 of the commutation circuit 5 does not have a zero point, and the nonlinear resistance 7
Commute to flow. Therefore, the operation is the same as that of the conventional DC circuit breaker of FIG. 3 shown in FIG. 4, and there is no influence on the large current interruption operation due to the provision of the second circuit 5a.

[0015]

As described above, in the present invention, the second circuit composed of the capacitor and the reactor connected in series is connected in parallel to the vacuum valve of the DC circuit breaker provided with the commutation circuit. As a result, the current flowing in the commutation circuit is not interrupted when the small-current line current of several A to several tens of amperes is interrupted. Therefore, overvoltage does not occur when the disconnector is opened during inspection, and It is possible to ensure the safety of workers and prevent the occurrence of a ground fault accident due to overvoltage. Moreover, as described above, it is possible to provide a DC breaker having a simple structure including a circuit in which a capacitor and a reactor are connected in series.

Further, in the present invention, the impedance value of the second circuit composed of the condenser and the reactor connected in parallel to the vacuum valve described above is determined by the impedance value of the commutation circuit composed of the commutation capacitor and the commutation reactance. By setting the value of the capacitance of the second circuit capacitor to be several tens of times or more and the value of the capacitance of the commutation capacitor of the commutation circuit to several tenths or less, the large fault current It is possible to interrupt a small current in a short time without affecting the interruption operation of.

As described above, the second circuit consisting of the capacitor and the reactor connected in series is connected in parallel to the vacuum valve of the DC circuit breaker provided with the commutation circuit, and the impedance of the second circuit is connected. Is more than tens of times the value of the impedance of the commutation circuit, and the value of the capacitance of the capacitor of the second circuit is less than a few tenths of the value of the capacitance of the commutation capacitor of the commutation circuit. By having a configuration that does not affect the interrupting operation of a large current such as a fault current of a line short circuit accident,
Moreover, it is possible to provide a DC circuit breaker capable of interrupting a small current in a short time. However, when applied to an actual product, by providing a disconnector on the load side of the DC circuit breaker, it is possible to improve safety. The safety can be improved.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a DC circuit breaker according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of current and voltage in each component when the DC circuit breaker of FIG. 1 is disconnected.

FIG. 3 is a circuit configuration diagram of a conventional DC circuit breaker.

4 is a waveform diagram of current and voltage in each component when a large current is interrupted at the time of a line fault in the DC circuit breaker of FIG.

5 is a waveform diagram of current and voltage in each component when a small current is interrupted by the DC circuit breaker of FIG.

[Explanation of symbols]

 1 Vacuum Valve 2 Commutation Capacitor 2a Capacitor 3 Commutation Reactor 3a Reactor 4 Commutation Switch 5 Commutation Circuit 5a Second Circuit

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[Procedure amendment]

[Submission date] June 25, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a DC circuit breaker according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of current and voltage in each component when the DC circuit breaker of FIG. 1 is disconnected.

FIG. 3 is a circuit configuration diagram of a conventional DC circuit breaker.

4 is a waveform diagram of current and voltage in each component when a large current is interrupted at the time of a line fault in the DC circuit breaker of FIG.

5 is a waveform diagram of current and voltage in each component when a small current is interrupted by the DC circuit breaker of FIG.

FIG. 6 is a circuit configuration diagram of a conventional DC circuit breaker different from that of FIG.

[Explanation of Codes] 1 vacuum valve 2 commutation condenser 2a condenser 3 commutation reactor 3a reactor 4 commutation switch 5 commutation circuit 5a second circuit

Claims (3)

[Claims] 1. A vacuum valve inserted in series in a main circuit connecting a DC power source and a load, a commutation capacitor connected in parallel with the vacuum valve, a commutation reactor and a commutation switch connected in series. Current flowing through the vacuum valve from a commutation capacitor that has been charged in advance by closing the commutation switch of the commutation circuit when the vacuum valve is opened. A DC circuit breaker which is superposed on and causes a zero current value to be cut off, wherein a second circuit consisting of a capacitor and a reactor connected in series is connected in parallel to a vacuum valve. 2. The DC circuit breaker according to claim 2, wherein the impedance value of the second circuit connected in parallel with the vacuum valve is several tens of times or more the impedance value of the commutation circuit. DC breaker. 3. The DC circuit breaker according to claim 2, wherein the value of the capacitance of the capacitor of the second circuit is less than a few tenths of the value of the capacitance of the commutation capacitor of the commutation circuit. A characteristic DC circuit breaker.