JPH03219513A - Vacuum-type circuit breaker - Google Patents

Abstract

PURPOSE:To shut a large electric current without any apparatus for protection from surge current by specifying pole opening speed 200-400mus before and after poles are opened. CONSTITUTION:When a trip signal is input, a motor starts working to rotate a cum 9 clockwise, and a roller 10a moves from the position where a tip stopping part is locked to the position where it is locked at a first step part. As soon as the roller 10a comes is contact with the first step part, a wipe is removed by a wipe spring 12 and during the roller 10a moves from the base part to the end part, the stroke of the roller 10a increases slowly and pole opening speed is made high. The speed of a contact of a vacuum valve 4 is set to 0.03m/s or less for 200-400mus after pole opening and to 1m/s or more after that. Consequently, high frequency electric current due to arc regeneration becomes small and large current can be shut off without installing an apparatus for protection from surge current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a vacuum circuit breaker that suppresses switching surges.

(Prior Art) It is known that when an inductive load current is interrupted by a vacuum circuit breaker, a peculiar switching surge is generated.

This opening/closing surge can be classified into three types based on its generation mechanism: ■ Current cutting surge ■ Multiple re-ignition (repetitive recurrence fi) surge ■ Three-phase simultaneous cut-off (three-phase induced cutting) surge.

■ is a phenomenon in which the current is forcibly cut off without waiting for the natural zero point of the AC current, and occurs during the process in which electromagnetic energy stored in the inductance of the load is converted to electrostatic energy in the stray capacitance of the circuit. do. (2) When the transient recovery voltage that occurs between the electrodes of the vacuum valve after the current is cut off exceeds the withstand voltage between the electrodes, a re-ignition occurs between the electrodes. When the high-frequency current flowing between the electrodes is extinguished at this time, a transient recovery voltage is generated again, and a discharge occurs between the electrodes. This is a phenomenon in which the voltage between the two ends increases. (3) When a re-ignition occurs between the poles of the first phase of interruption, the high frequency current flowing at this time is superimposed on the AC current of other phases via the stray capacitance of the circuit, forcibly forming a current zero point, This refers to a phenomenon that is interrupted at that zero point. At this time, the other phase appears to be the same as cutting a current equivalent to the load current, and a large surge voltage is generated.

As a method for suppressing these opening/closing surges, (a) the contacts of the vacuum valve are formed from a material with a low cutting current value.

(b) Install surge protection devices such as CR surge suppressors and lightning arresters.

It can be roughly divided into two types. Method (a) is applied to equipment that does not require large current interruption, such as vacuum contactors. The method (b) is used in devices that require large current interruption in the event of an accident, such as vacuum circuit breakers (see Proceedings of the Institute of Electrical Engineers of Japan Vol. 93. Nα8).

(Problems to be Solved by the Invention) Generally, switching surge protection in a vacuum circuit breaker is performed by installing a surge protection device such as a CR surge suppressor or lightning arrester. However, installing these surge protectors worsens the space factor of the equipment and requires the work of selecting a surge protector suitable for the circuit to which the vacuum circuit breaker is applied, which burdens the work of system engineers. , there is a concern that selection errors may occur.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a vacuum circuit breaker that is capable of interrupting large currents and does not require a surge protection device.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a vacuum circuit breaker equipped with a vacuum valve that opens and closes a pair of contacts in a high-vacuum container with a pressure below IO-''Pa, in which the opening speed at the time of opening is The speed is 0.03 m/s or less before 200 to 400 μs after opening, and 1 m/s or more after 200 to 400 μs.

(Function) The gap length between the contacts is as small as 3 to 12 μs until 200 to 400 μS after contact opening, and the insulation recovery voltage is suppressed to a low value of several hundred pol 1 − or less. However, 200~400μ after opening
After s, the gap length between the contacts increases at a rate of 1 m/s or more, and the insulation recovery voltage increases at a rate of 10 x 106 volts/sec or more, making it possible to prevent re-ignition.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing one embodiment of the present invention.

3- In the same figure, the vacuum circuit breaker consists of a mount 1 which is provided with wheels 1a and is movable, an insulating support frame 2 fixed to the mount 1, and an operation panel fixed to the front side of the insulating support frame 2. A mechanism 3 and a vacuum valve 4 fixed to the back side of the insulating support frame 2
In this vacuum valve 4, a fixed shaft of a fixed contact (not shown) is connected to an upper outlet terminal 5, and a movable shaft 6 of a movable contact (not shown) is connected to a lower outlet terminal 7 via a flexible conductor 7a. is connected to.

On the other hand, the operating mechanism 3 includes a main shaft 8 connected to an internally mounted motor (not shown) and an appropriate torque transmission means.
A cam 9 is attached to the main shaft 8 so as to rotate together with the main shaft 8, and the cam 9 is connected to a link 10 via a roller 10a. This link 10 is
It is rotatably supported by the insulating support frame 2, and the - side (upper side) is connected to the movable shaft 6 of the vacuum valve 4 via the operating rod 11 and wipe spring 12, and the other side (lower side) is for tension adjustment. It is connected to a return spring 13 that makes it possible to

Further, the cam 9 is provided with a first four-step portion 9a and a second step portion 9b, as shown in FIG. Therefore, the first step portion 9a has a step at its base (a position at a radius r from the center of the main shaft 8) from the tip locking portion 9c by an amount corresponding to the wipe amount of the wipe spring 12, and has a radius r. It is formed by a circular arc (indicated by a dotted line) that is inclined toward the center. The base of the second step 9b has a step difference corresponding to the opening/closing stroke of the vacuum valve 4 minus the amount of opening/closing at the first step 9a.
It is provided between the end of a.

Next, the operation of the embodiment configured as above will be explained. When a trip signal is input with the vacuum circuit breaker in the closed state shown in FIG. 1, a motor (not shown) is started and rotates the cam 9 clockwise in the figure. This rotation of the cam 9 moves the roller 10a from the position where it is locked by the tip locking part 9c to the position where it is locked by the first step part 9a. At this time, the moment the roller 10a comes into contact with the base of the first step 9a, the wipe by the wipe spring 12 is removed, and the roller 1
While 0a moves from the base to the end, the stroke of the roller 10a increases slowly, and the contact point of the vacuum valve 4 is opened at an opening speed of 0.03 m/s or less from 200 to 400 μs after opening. Open the pole. At this time, the gap length between the contacts of the vacuum valve 4 is as small as 6 to 12p or less, and the insulation recovery voltage is kept low as several hundred volts or less. On the other hand, after opening 20
After 0 to 400 IIS, the roller 10a moves away from the first step 9a and moves to the second step 9b. At this time, the gap length between the contacts of the vacuum valve 4 increases rapidly,
Opens at a speed of 1 m/s or more. The insulation recovery voltage at this time increases at a rate of 10 x 10 G volts/second or more.

The reason why the opening speed was varied before and after 200 to 400 m after the contact was opened as described above is as follows.

In other words, when the contact is opened at a very slow opening speed of about 0.03 m/s, the insulation recovery is very slow <1 x 10 G volt/s or less before 200 to 400 μs, but the Even if the gap length increases at the same rate, after 200 to 400 μs after opening, it increases by 10 x 10' volts/
The insulation recovery voltage increases at a rate of about seconds. At this time, if the opening speed is large, the speed of insulation recovery increases accordingly. When the relationship between the elapsed time after contact opening and the insulation recovery voltage was investigated, the results shown in FIG. 3 (solid line) were obtained. As is clear from the figure, the characteristics suddenly change 200 to 400 μs after opening. Note that the dotted line in the same figure indicates that the opening speed is 2.
The characteristics when the speed is as slow as 0.03 m/s even after 00 to 400 μs are shown.

Therefore, according to the embodiment described above, the following effects can be obtained.

When a vacuum circuit breaker interrupts a current with a lagging power factor of /11, unique surges occur, such as current cutting surges, repeated re-ignition surges, and three-phase simultaneous interruption surges. Among these, simultaneous three-phase shutdown generates the largest surge. This is a phenomenon that occurs because the high-frequency current generated when the first phase of interruption is re-ignited is superimposed on the other phase current to form a current zero point, and the current is extinguished at that zero point. The insulation recovery characteristics according to this example are 200 to 400μ as shown in FIG.
Previously, the insulation recovery voltage was several hundred volts or less after S, and even if the first phase of the shutdown were to fire again, the high frequency current that would be generated would be small, and the alternating current of the other phases would be forced to No zero point is created and three-phase simultaneous shutdown does not occur. Furthermore, after 200 to 400 μs, the current cutting surge that occurs in the first phase of interruption will not re-ignite because the insulation recovery voltage is sufficiently large. This eliminates the occurrence of surges caused by simultaneous three-phase interruption, which is the most severe problem in the circuit.

It should be noted that the present invention is not limited to the above embodiments, but the opening speed is defined around 200 to 400 μs after opening so that the insulation recovery characteristics as shown in FIG. 3 can be obtained. Any method may be used as long as it is carried out, and it may be carried out by other means.

〔Effect of the invention〕

Since the present invention is configured as described above, when a delayed small current is interrupted, the first phase of interruption is 200 to 400 I after opening.
When a re-ignition occurs within J5, the insulation recovery voltage is several hundred volts or less, and the high frequency current generated by the re-ignition is small and does not forcibly create a zero point in the alternating current of other phases.
Three-phase simultaneous shutdown does not occur. Also, 200 to 400 μs
Thereafter, the current cutting surge that occurs in the first phase of interruption will not cause a re-ignition because the insulation recovery voltage is sufficiently large. As a result, it is possible to eliminate the occurrence of surges caused by simultaneous three-phase interruption, which is the most severe problem in a circuit, and the troublesome selection of a surge protection device can be eliminated, as well as the need for installation space.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing an embodiment of the present invention, Fig. 2 is a detailed view showing the main parts of an embodiment of the invention, and Fig. 3 is a diagram of insulation recovery characteristics of an embodiment of the invention. be.

Claims (1)

[Claims] In a vacuum circuit breaker equipped with a vacuum valve that opens and closes a pair of contacts in a high vacuum container of 10^-^2 Pa or less, the opening speed at the time of opening is set to 0.0 within 200 to 400 μs after opening.
3m/s or less, 1m/s after 200~400μs
A vacuum circuit breaker characterized by the above.