JPH0298024A - DC circuit breaker - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC circuit breaker of reverse current insertion type that improves the opening time of the circuit breaker.

[Conventional technology]

A conventional DC circuit breaker of the reverse current insertion type has a configuration as shown in FIG. 3 described in, for example, the September 1980 issue of Denki Hyōron. A circuit breaker 2 connected in series to the DC main line 1 and a commutating capacitor 3 connected in parallel to the circuit breaker 2. Reactor 4.
It is composed of a commutation circuit 10 consisting of a commutation switch 5.

When performing a breaking operation, as shown in Fig. 4 (A), an opening command is given to the circuit breaker 2 at time t1, and after the circuit breaker 2 opens at time t2 and an arc indicated by a chain line is generated, the commutation switch is turned off. 5 is turned on at time t8, and the discharge current from the commutation capacitor 3 is made to flow in the opposite direction to the energizing current of the circuit breaker 2, the current passing through the circuit breaker 2 reaches the current zero point at the time t4, and the circuit breaker 2 is turned off. The main line current is then commutated to the commutation circuit 10 to complete the interrupting operation. Note that FIG. 4(A) shows the case of short circuit current iz, and FIG. 4(B) shows the case of normal current 12.

[Problem to be solved by the invention]

In this way, when the commutation switch 5 is operated after the circuit breaker 2 is opened, the circuit breaker 2 will interrupt a large arc current, and there is a limit to the current that can be interrupted with one vacuum valve, and this limit It was necessary to use multiple vacuum valves in parallel for interrupting currents exceeding . In this case, a balance resistor is required to equalize the current flowing through the multiple vacuum valves, and complicated adjustment of the operating device is required to reduce variations in the operating time of the multiple vacuum valves. There was a problem.

An object of the present invention is to provide a DC circuit breaker that can cut off current with a single vacuum valve.

[Means to solve the problem]

The breaking ability of a vacuum valve is mainly controlled by the arc energy from opening to breaking, the rate of change of current at breaking, and the re-electromotive voltage. Among these, the arc energy from opening to breaking in the first term is This can be suppressed by controlling the time difference between opening the device and turning on the commutation switch. In other words, the operation of the commutation switch is made faster than the opening of the circuit breaker,
Moreover, by controlling the time difference between the two according to the current value to be interrupted, the current value when the circuit breaker is opened can be made smaller than the current to be interrupted, and the above object can be achieved.

[Effect]

The maximum value of the discharge current supplied by the commutating capacitor is set to be greater than the maximum value of the current to be interrupted, and if the interrupting current is constant, the time from the operation of the commutating switch to the opening of the circuit breaker is controlled to a constant value, and the arc current during opening is suppressed to a small value. Also, if the breaking current is undefined.

A current detector measures the absolute value and time rate of change of the main line current and predicts the current value at the breaking point.

Considering this value and the waveform of the discharge current caused by the capacitor, the commutation switch operates so that the arc current between the circuit breaker contacts when the circuit breaker opens is a moderately small value that is almost constant regardless of the value of the current to be interrupted. Controls the time from the time to the opening of the circuit breaker.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

A circuit breaker, such as a vacuum circuit breaker, connected in series with the DC main line 1 and a commutating capacitor connected in parallel to the circuit breaker 3. Reactor 4. It consists of a commutation circuit 10 consisting of a commutation switch 5. A current detector 6 is provided on the DC main line 1, and a control device 7 is provided that controls the operating time of the circuit breaker 2 and the commutation switch 5 based on the output value of the current detector 6.

Next, the operation of the commutation circuit 10 will be explained with reference to FIG. 2. When a cutoff command is given at time ti, the control device 7 predicts the current value at the cutoff point based on the output of the current detector 6, and calculates this value. Considering the discharge current waveform caused by the capacitor 3, the arc current between the circuit breaker contacts at the time of opening is set to a reasonably small value that is almost constant regardless of the value of the current to be interrupted, that is, a current value near the current zero point. 5 The time difference is controlled and an operation command is given to the commutation switch 5 and the circuit breaker 2.

When the commutation switch 5 is turned on at time t2, the commutation capacitor 3 vibrates and discharges in a closed circuit consisting of the commutation circuit 10 and the circuit breaker 2, and the current passing through the circuit breaker 2 decreases sufficiently. The circuit breaker 2 is opened at time t8 near the current zero point, and the circuit breaker 2 is extinguished at the current zero point, which is then reached, and the main line current is commutated to the commutation circuit 10 to complete the breaking operation.

In this way, in the present invention, the control device 7 is used to open the circuit breaker 2 in the vicinity of the current zero point after the commutation switch 5 is turned on, so that the arc current can be broken at a small value. This not only makes it possible to reduce the number of DC circuit breakers that were previously used, but also increases the life of the contacts in the vacuum valve.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to interrupt a small arc current at the time of opening regardless of the magnitude of the interrupting current. , electrical contact life can be increased.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a DC breaker showing an embodiment of the present invention,
FIG. 2 is a breaking characteristic diagram of the breaking current flowing through the breaker section of the DC breaker according to the present invention, FIG. 3 is a circuit diagram of a conventional DC breaker, and FIG. 4 is a breaking characteristic diagram of FIG. 3. 1... DC main line, 2... Circuit breaker, 3... Commutation capacitor, 4... Reactor, 5... Commutation switch, 6... Mitsutaka 1 Figure 2nd day 3rd Nippon Tower Gokuko Go (I)

Claims (1)

[Claims] 1. Reverse current insertion in which a pre-charged capacitor is connected by a switch and a capacitor discharge current in the opposite direction to the main circuit current is caused to flow through the circuit breaker contacts to forcibly generate a current zero point and interrupt the operation. In the DC circuit breaker of this type, the switch is turned on earlier than the opening of the breaker contacts during the breaking operation, and the arc current between the breaker contacts at the time of opening is reduced by the discharge current of the capacitor. A DC circuit breaker characterized by: 2. The current value at the breaking point of the current to be interrupted is predicted based on the detected current of the main circuit detected by the current detector, and the arc current between the circuit breaker contacts at the time of opening is determined regardless of the value of the current to be interrupted. 2. The DC circuit breaker according to claim 1, wherein the time difference between the closing of the switch and the opening of the circuit breaker contact is controlled so as to maintain a substantially constant, moderately small value. 3. The DC circuit breaker according to claim 1, wherein the opening time of the circuit breaker is delayed from the switch closing time during the breaking operation. 4. The direct current according to claim 1 or 2, further comprising a control device that opens the circuit breaker after turning on the switch based on the detected current of a current detector provided in the main circuit. circuit breaker. 5. Claims 1 or 2, characterized in that a control device is provided to open the circuit breaker near the current zero point after the switch is turned on by the detected current of a current detector provided in the main circuit. DC circuit breaker as described in section. 6. Connect a vacuum circuit breaker to the main circuit, input a commutation circuit in which a commutation capacitor and a commutation switch are connected in parallel to the vacuum circuit breaker, and input the detected current of the current detector connected to the main circuit to the control device, A DC circuit breaker characterized in that a vacuum circuit breaker is opened after a commutation switch is turned on by a control device.