JP2004319150A - D.c. circuit breaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce control force of an operation mechanism of an auxiliary circuit breaker serially connected to a main circuit breaker. <P>SOLUTION: This D.C. circuit breaker is provided with: the main circuit breaker 1 and the auxiliary circuit breaker 2 serially connected to a D.C. circuit; a commutation circuit 6 having a capacitor 4 and a commutation switch 3 connected in parallel with the circuit breaker 1 for superposing a reverse commutation current on the D.C. circuit; a first operation mechanism 11 for switching the circuit breaker 1; and a second operation mechanism 12 for switching the circuit breaker 2. The D.C. circuit breaker is characterized by that the circuit breaker 1 and the circuit breaker 2 start to open and the commutation current is carried from the commutation circuit 6; control force of the operation mechanism 11 is so set that the electrodes of the circuit breaker 1 reach open positions with respect to each other by the time a D.C. current comes to a current zero point between the electrodes of the circuit breaker 1; and control force of the operation mechanism 12 is so set that the electrodes of the circuit breaker 2 reach open positions with respect to each other by the time the D.C. current of the D.C. circuit is attenuated to come to a current zero point. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a DC circuit breaker in which the operation of a sub circuit breaker connected in series with a main circuit breaker when a DC circuit is cut off by a vacuum circuit breaker.
[0002]
[Prior art]
A conventional DC breaker has a main circuit breaker and a sub circuit breaker connected in series to a DC circuit, and a commutation current is injected from a commutation circuit connected in parallel to the main circuit breaker to create a current zero point and cut off at the main circuit breaker. And a DC circuit is opened by a sub-breaker (for example, see Patent Document 1).
[0003]
As shown in FIG. 2, in this type of DC circuit breaker, a main circuit breaker 1 and a sub circuit breaker 2 having a pair of detachable electrodes are connected in series between PN of a DC circuit. . A commutation circuit 6 in which a commutation switch 3, a capacitor 4, and a reactor 5 are connected in series is connected to the main circuit breaker 1 in parallel, and a surge absorber 7 for absorbing energy is also connected in parallel. . The main circuit breaker 1 and the sub circuit breaker 2 are opened and closed almost simultaneously by the same operation mechanism 8.
[0004]
In such a circuit configuration, as shown in FIG. 3, considering a case where an excessive fault current Ia flows in the DC circuit, a cutoff command is issued from the control circuit to the main circuit breaker 1 and one of the main circuit breakers 1 The other electrode is separated from the electrode, and a fault current Ia flows between the two electrodes. When the fault current Ia reaches a time t1 at which the electrode opens to the opening position, the commutation switch 3 operates to discharge the pre-charged capacitor 4, and the fault current Ia flows in a direction opposite to the fault current Ia. The commutation current is superimposed, and becomes an AC waveform as shown by the solid line, and is interrupted at time t2 when the current reaches zero. By the time t2, the main circuit breaker 1 reaches the opening position.
[0005]
At the same time as the main circuit breaker 1, the sub-circuit breaker 2 also starts operating to separate the electrodes, and the same fault current Ia flows between both electrodes of the sub-circuit breaker 2. The fault current Ia continues to rise until the time t2 at which the main circuit breaker 1 completes the interruption as indicated by the dotted line, and then attenuates due to the time constant of the capacity of the capacitor 4 of the commutation circuit 6 and the load resistance of the DC circuit. Therefore, the current is cut off at time t3 when the current becomes zero.
[0006]
As described above, the main circuit breaker 1 and the sub circuit breaker 2 are operated by the same operation mechanism 8 and start opening at almost the same time. After the main circuit breaker 1 interrupts the fault current Ia, the sub circuit breaker 2 Is to be opened.
[0007]
For this reason, the operating mechanism 8 sets the opening / closing speed of, for example, 2 to 3 m / s, particularly the opening speed, so that the main circuit breaker 1 and the sub circuit breaker 2 reach the opening position by time t2. In order to obtain this, an operating force of 40 to 50 kN is given at a rated current of 3000 A class per vehicle. That is, the operating force of, for example, the open circuit spring of the operating mechanism 8 is required to be 80 to 100 kN which is twice as large as that described above in order to simultaneously open the main and sub circuit breakers 1 and 2.
[0008]
[Patent Document 1]
Patent No. 3135338 (page 2, FIG. 1)
[0009]
[Problems to be solved by the invention]
The above-described conventional DC circuit breaker has the following problems.
[0010]
The main circuit breaker 1 and the sub circuit breaker 2 are required to open by the same operating mechanism 8 and have a high opening / closing speed, so that the operating mechanism 8 requires an excessive operating force. This operating force is an indispensable condition for the main circuit breaker 1, but not an indispensable condition for the sub circuit breaker 2. In the auxiliary circuit breaker 2, if the DC current reaches the opening position by the time t3 at which the DC current attenuates and reaches the current zero point, the DC circuit can be opened.
[0011]
However, in the auxiliary circuit breaker 2, the operation force of the operation mechanism 8 must be increased, and the operation force of the operation mechanism 8 is increased. For this reason, it has been desired to make the operating force of the main circuit breaker 1 and the sub circuit breaker 2 appropriate.
[0012]
Therefore, an object of the present invention is to provide a DC breaker that reduces the operating force for operating the sub-breaker.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a DC circuit breaker of the present invention is a DC circuit having a main circuit breaker and a sub circuit breaker connected in series to a DC circuit, and a capacitor and a commutation switch connected in parallel to the main circuit breaker. A commutation circuit for superimposing a reverse commutation current on a circuit; a first operation mechanism for opening and closing the main circuit breaker; and a second operation mechanism for opening and closing the sub circuit breaker. A commutation current is injected from the commutation circuit when the circuit breaker starts opening, so that the gap between the electrodes of the main circuit breaker reaches the opening position before the DC current reaches the current zero point between the electrodes of the main circuit breaker. The operation force of the first operation mechanism is set to the second operation so that the gap between the electrodes of the auxiliary circuit breaker reaches the opening position before the DC current of the DC circuit attenuates and reaches the current zero point. The operation force of the mechanism is set.
[0014]
According to such a configuration, since the opening / closing speed of the second operating mechanism of the sub circuit breaker is made slower than that of the first operating mechanism of the main circuit breaker, the operating force of the second operating mechanism is greatly reduced. be able to.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
A DC breaker according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a circuit configuration diagram of a DC breaker according to an embodiment of the present invention, and FIG. 3 is an explanatory diagram for explaining an operation of the DC breaker according to the embodiment of the present invention. In each of the drawings, the same components as those in the related art are denoted by the same reference numerals.
[0016]
As shown in FIG. 1, a main circuit breaker 1 and a sub circuit breaker 2 having a pair of detachable electrodes composed of, for example, a vacuum valve are connected in series between PN of the DC circuit. The main circuit breaker 1 is connected in parallel with a commutation circuit 6 in which a commutation switch 3, a capacitor 4 and a reactor 5 are connected in series, and a surge absorber 7 for energy absorption is also connected in parallel. I have. The main circuit breaker 1 and the sub circuit breaker 2 are provided with first and second operation mechanisms 11 and 12, respectively, so that they can be individually opened and closed.
[0017]
In such a circuit configuration, as shown in FIG. 3, when an excessive fault current Ia flows through the DC circuit, a control circuit (not shown) issues a cutoff command to the main circuit breaker 1, and the first operating mechanism 11 is turned off. The main circuit breaker 1 is operated to separate one electrode from the other electrode. At this time, a fault current Ia flows between the two electrodes via an arc. When the fault current Ia reaches a time t1 at which the two electrodes start to be separated from each other and reach the opening position, the commutation switch 3 operates to discharge the pre-charged capacitor 4, and the fault current Ia Thus, the commutation current is superimposed in the reverse direction, and becomes an AC waveform as shown by the solid line, and is interrupted at time t2 when the current reaches zero.
[0018]
The first operating mechanism 11 has an opening / closing speed such that the electrodes of the main circuit breaker 1 start separating and reach the opening position, which is the final position of the separation, by the time t2 when the current becomes zero. I have. That is, the opening / closing speed is, for example, 2 to 3 m / s, and particularly, an opening speed for separating the electrodes can be obtained. In order to obtain this opening / closing speed, for example, the operating force of the open-circuit spring of the first operating mechanism 11 is set to 40 to 50 kN at a rated current of 3000 A class.
[0019]
On the other hand, the sub circuit breaker 2 is issued a disconnection command at the same time as the main circuit breaker 1, and the second operating mechanism 12 operates to start opening as in the case of the main circuit breaker 1. The second operating mechanism 12 reaches the opening position, which is the final position of the separation, at time t4 until the current of the DC circuit attenuates due to the time constant with the load resistance to reach the current zero point t3. It has become. At t3 when the current reaches zero, the sub circuit breaker 2 ensures that the DC circuit is opened.
[0020]
For this reason, the opening / closing speed of the sub circuit breaker 2 is lower than that of the first operation mechanism 11, for example, about 0.5 m / s. That is, the time from when the electrodes of the sub circuit breaker 2 start to be separated to when the electrodes reach the opening position, which is the final position of the separation, is delayed. Accordingly, the operating force of the second operating mechanism 12, which greatly affects the opening / closing speed, may be about 7.5 kN at a rated current of 3000 A class, and is about 1/6 of that of the first operating mechanism 11.
[0021]
According to the DC circuit breaker of the above embodiment, after the fault current is cut off by the main circuit breaker 1 having a fast switching speed, the DC circuit is opened by the sub circuit breaker 2 having a slow switching speed. The operating force of the second operating mechanism 12 can be greatly reduced, and the operating force of the entire operating mechanism can be reduced.
[0022]
The present invention is not limited to the above embodiment, and can be implemented with various modifications without departing from the spirit of the invention. In the embodiment of the present invention, the main circuit breaker 1 and the sub circuit breaker 2 start opening at the same time. Alternatively, the time at which the opening of the sub-breaker 2 is started may be delayed so that the sub-breaker 2 reaches the opening position by time t3.
[0023]
Thereby, in addition to the effect of the present embodiment, the arc continuation time between the electrodes of the auxiliary circuit breaker 2 is shortened, and the consumption of the electrodes can be suppressed. Further, the diameter of the electrode of the sub circuit breaker 2 can be reduced.
[0024]
【The invention's effect】
As described above, according to the present invention, the first and second operating mechanisms are provided in the main circuit breaker and the sub circuit breaker connected in series to the DC circuit, respectively, and the switching speed of these is set to be smaller than that of the main circuit breaker. Since the circuit breaker is made slower, the operating force of the second operating mechanism can be greatly reduced, and the operating force of the entire operating mechanism can be reduced.
[Brief description of the 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 circuit configuration diagram of a conventional DC circuit breaker.
FIG. 3 is an explanatory diagram for explaining the operation of the DC breaker.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main circuit breaker 2 Secondary circuit breaker 3 Commutation switch 4 Capacitor 5 Reactor 6 Commutation circuit 7 Surge absorber 8 Operating mechanism 11 First operating mechanism 12 Second operating mechanism

Claims (3)

A main circuit breaker and a sub circuit breaker connected in series to a DC circuit,
A commutation circuit for superimposing a commutation current in the reverse direction on the DC circuit having a capacitor and a commutation switch connected in parallel to the main circuit breaker,
A first operation mechanism that opens and closes the main circuit breaker and a second operation mechanism that opens and closes the sub circuit breaker,
The commutation current is injected from the commutation circuit when the main circuit breaker and the sub circuit breaker start opening, and the DC current reaches the current zero point between the electrodes of the main circuit breaker. The operating force of the first operating mechanism is set so that
By the time the DC current of the DC circuit attenuates and reaches the current zero point, the operating force of the second operating mechanism is set so that the gap between the electrodes of the sub-breaker reaches the opening position. Circuit breaker. 2. The DC breaker according to claim 1, wherein an opening / closing speed of the second operating mechanism is lower than an opening / closing speed of the first operating mechanism. 3. The direct current circuit breaker according to claim 1 or 2, wherein a time when the sub circuit breaker starts opening is delayed from a time when the main circuit breaker starts opening.

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