JPH08148066A - Commutation type DC circuit breaker - Google Patents

Abstract

(57) [Abstract] [Object] An object of the present invention is to reduce an overcurrent flowing into a DC circuit when a small current such as a rated current is cut off, and to improve charging efficiency of a capacitor in a commutation circuit. To supply the commutated DC circuit breaker. The commutation type DC circuit breaker of the present invention comprises a main contact 2 inserted in a DC circuit 1 connecting a DC power supply 17 and a load 18.
And a commutation circuit 3 in which a first switch 4, a reactor 5, and a first capacitor 6 connected in series are connected in parallel to the main contact, and a second switch 8 and a second switch connected in series are provided. Capacitor 9 is connected in parallel to the first capacitor 6, and the main contact 2, the first switch 4, and the first switch 4 are connected in accordance with the current value measured by the current transformer 10 provided in the DC circuit 1 or the external command 11. And a control circuit 12 for controlling opening / closing of the second switch 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a commutation type DC circuit breaker, and in particular, commutation circuit capacitors are connected in parallel to reduce an overcurrent flowing into the DC circuit when a small current such as a rated current is cut off. Commutation circuit configuration.

[0002]

2. Description of the Related Art A capacitor of a commutation circuit of a DC circuit breaker is divided into a plurality of blocks and connected in series, and a commutation path for a commutation current is generated by short-circuiting or unwinding a part of the capacitor. A DC circuit breaker configured to supply commutation current by changing it according to the breaking current value is disclosed in Japanese Patent Laid-Open No. 58-3842.
It is described in issue 0.

[0003]

However, the above-mentioned prior art does not mention the use of the capacitors of the commutation circuit connected in parallel, and the excessive current flowing into the DC circuit when the DC current is cut off. There is no mention of reducing the current.

An object of the present invention is to reduce the overcurrent flowing into a DC circuit when a small current such as a rated current is cut off, and to improve the charging efficiency of a capacitor in a commutation circuit. To supply vessels.

[0005]

In order to achieve the above object, a commutation type DC circuit breaker of the present invention is connected in series with a main contact inserted in a DC circuit connecting a DC power source and a load. A commutation circuit in which a first switch, a reactor, and a first capacitor are connected in parallel to the main contact, and a second switch and a second capacitor connected in series are provided in the first capacitor. Circuit connected in parallel to the main circuit and controlling the opening and closing of the main contact, the first switch and the second switch by the current value measured by the current transformer provided in the DC circuit, the amount of change in the current value or an external command And to prepare.

[0006]

Operation When shutting off a large current such as a short circuit current, by closing the first switch while keeping the second switch closed, both the first and second capacitors are discharged and transferred to the main contact. Send a current. If you want to cut off a current that is sufficiently smaller than the short-circuit current, such as the rated current,
By opening the first switch and closing the first switch, only the first capacitor is discharged and a commutation current is passed to the main contact. In this way, when the small current is cut off, the capacitance of the capacitor to be discharged is made smaller and the commutation current value is greatly reduced compared to the case where the large current is cut off. The overcurrent value that flows in can be reduced.

[0007]

EXAMPLE An example of the present invention will be described below with reference to FIG.

Reference numeral 1 is a DC circuit through which a DC current flows. Two
Is a main contact of a DC circuit breaker inserted in the DC circuit 1, such as a vacuum valve, which is normally closed and is opened when the DC current is cut off. Reference numeral 3 is a commutation circuit of a DC circuit breaker connected in parallel to the main contact 2. The commutation circuit 3 is configured by connecting a first switch 4, a reactor 5, and a first capacitor 6 in series.

A series circuit 7 of a second switch 8 and a second capacitor 9 is connected in parallel to the first capacitor 6. The electrostatic capacity (C1) of the first capacitor 6 is the electrostatic capacity necessary for the current to be interrupted to interrupt a small current such as the rated current, and the electrostatic capacity (C2) of the second capacitor 9 is used. Is the electrostatic capacitance such that the combined electrostatic capacitance (C1 + C2) with the electrostatic capacitance (C1) of the first capacitor 6 becomes the electrostatic capacitance necessary for interrupting the short circuit current. Normally, the first switch 4 is open and the second switch 8
Is closed.

Reference numeral 10 is a current transformer attached to the DC circuit 1 for measuring the current of the DC circuit 1, and 11 is an external command for controlling the opening and closing of the DC circuit breaker from a distance, and both are sent to the control circuit 12. Input the signal. The control circuit 12 is the current transformer 1
0 and a signal from the external command 11
The opening and closing of the switch 4 and the second switch 8 are controlled. When the direct current is cut off, the main contact 2 is first opened, and then the first switch 4 is closed. However, when the small current is cut off, the second switch 8 is opened and then the main contact 2 is opened. The switch 4 is closed.

First capacitor 6 and second capacitor 9
Is charged by the charging circuit 13. The charging circuit 13 is composed of a charging switch 14, a charging power source 15, and a charging resistor 16 connected in series. When charging the first capacitor 6 and the second capacitor 9, the first switch 4 is opened to charge the first capacitor 6 and the second capacitor 9. The switch 14 is closed. The capacitor is charged until the terminal voltage of the capacitor reaches the voltage of the charging power supply 15. The charging time is the combined capacitance (C1 + C2) of the first capacitor 6 and the second capacitor 9 and the charging resistor 16
Is determined by

Reference numeral 17 is a DC power supply for supplying DC power to the DC circuit 1. Reference numeral 18 denotes a load, and in a normal state, DC power is supplied from the DC power supply 17 to the load 18 through the DC circuit 1.

Next, the operation of the commutation type DC circuit breaker will be described.

Normally, a rated current determined by the DC power source 17 and the load 18 flows in the DC circuit 1. But load 1
In Fig. 8, when the load 18 is short-circuited due to an accident or the like, a very large short circuit current may flow through the DC circuit 1 as compared with the rated current.

The procedure for interrupting a large current such as a short circuit current is as follows. When a large current flows through the DC circuit 1, the current value measured by the current transformer 10 is input to the control circuit 12,
The control circuit 12 gives an opening command to the main contact 2, and then the first contact
A closing command is given to the switch 4. In this case, both the first capacitor 6 and the second capacitor 9 are discharged and LC
A large commutating current that resonates flows through the main contact 2 and is superimposed on the direct current, and when the current reaches the zero point, the current is cut off.

The cutoff of the rated current is mainly performed when the DC circuit 1 is opened / closed in a normal state. The interruption procedure at that time is as follows. An open command for the DC circuit breaker is input to the control circuit 12 as an external command 11. Control circuit 1
Reference numeral 2 takes in the current value measured by the current transformer 10, and if the current value is about the rated current value, gives an opening instruction to the main contact 2 and then gives an opening instruction to the second switch 8. Finally, a closing command is given to the first switch 4. In this case the first
Only the capacitor 6 is discharged, and the second capacitor 9 is not discharged but remains charged.

Therefore, the commutation current becomes as small as the rated current, and even if the commutation current flows into the DC circuit 1 when the DC current is cut off, the overcurrent does not flow into the load 18. Therefore, it is safe even if the worker comes into contact with the load 18 by looking at this opening instruction.

Furthermore, the capacitor must be recharged to cut off the current next time, but after the cutoff of the rated current, the second capacitor 9 remains charged, so that only the first capacitor 6 needs to be charged. It is good and the charging efficiency can be improved.

In the above-described embodiment, the electrostatic capacity C1 of the first capacitor 6 is the electrostatic capacity necessary for interrupting the small current such as the rated current to be interrupted, and the second capacitor 9 The electrostatic capacitance C2 of is the electrostatic capacitance such that the combined electrostatic capacitance (C1 + C2) with the electrostatic capacitance C1 of the first capacitor 6 becomes the electrostatic capacitance necessary for interrupting the short-circuit current. The electrostatic capacity C1 of the first capacitor 6 may be an electrostatic capacity necessary for the current to be interrupted to interrupt a small current other than the rated current.

The capacitance C1 of the first capacitor 6
And the second capacitor 9 may have the same capacitance C2. In this case, since the same product can be used for the first capacitor 6 and the second capacitor 9, there is compatibility between these two capacitors. It is possible to reduce the manufacturing cost of the DC circuit breaker.

[0021]

As described above, in the commutation type DC circuit breaker, the capacitors of the commutation circuit are connected in parallel so that the DC circuit can be used especially when a small current such as a rated current is cut off. It is possible to reduce the overcurrent flowing into the. Further, it is safe even if the worker comes into contact with the load 18 while seeing the opening instruction. Furthermore, since the second capacitor 9 is not discharged after the small current is cut off, it is sufficient to charge only the first capacitor 6 and the charging efficiency of the capacitor in the commutation circuit can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a commutation type DC circuit breaker which is an embodiment of the present invention.

[Explanation of symbols]

1 ... DC circuit, 2 ... Main contact point, 3 ... Commutation circuit, 4 ... First switch, 5 ... Reactor, 6 ... First capacitor, 7
... series circuit, 8 ... second switch, 9 ... second capacitor, 10 ... current transformer, 11 ... external command, 12 ... control circuit,
13 ... Charging circuit, 14 ... Charging switch, 15 ... Charging power source, 16 ... Charging resistance, 17 ... DC power source.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Haruo Honda 1-1-1 Kokubuncho, Hitachi City, Ibaraki Hitachi Kokubun Plant, Hitachi Ltd.

Claims (3)

[Claims] 1. A main contact inserted in a DC circuit connecting a DC power supply and a load, a first switch, a reactor, and a first contact.
A commutation type DC circuit breaker comprising a main circuit and a capacitor connected in parallel to the main contact, and a second switch and a second capacitor connected in parallel to the first capacitor. A commutation type characterized by comprising a main contact, a control circuit for controlling the opening and closing of the first switch and the second switch according to a current value measured by a current transformer provided in the DC circuit or an external command. DC circuit breaker. 2. The commutation type DC circuit breaker according to claim 1, wherein the first capacitor is a capacitor having a smaller electrostatic capacity than that of the second capacitor. 3. The commutation type DC circuit breaker according to claim 1, wherein the first capacitor and the second capacitor are capacitors having the same electrostatic capacity.