JPH04179016A - Vacuum circuit-breaker - Google Patents

Abstract

PURPOSE:To suppress a drop in a withstand voltage between contacts and reduce the occurrence of a restrike by using vacuum bulbs in serial connection, and providing a differential in the gap lengths of respective vacuum bulbs. CONSTITUTION:A lever ratio which is used for operating two vacuum bulbs 8a, 8b connected to each other in series is changed so as to change the gap lengths of the vacuum bulbs 8a, 8b. Then, one of the vacuum bulbs is always threw-in in advance so that an arc of an inrush current to be generated on throwing-in can be formed only between the contacts of the other vacuum bulb which is threw-in later. The vacuum bulb threw-in first can consistently maintain the initial state of its surface, making for suppressing a drop in a withstand voltage and preventing the occurrence of a restrike.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a vacuum circuit breaker that is less prone to restriking.

(Prior art) When an electric circuit is opened and closed, a transient phenomenon occurs in the circuit. Even in capacitor circuits to which a vacuum circuit breaker is applied, transient phenomena occur in the circuit when the vacuum circuit breaker is opened and closed. When the power is turned on, a high-frequency inrush current with a high peak value flows through the circuit in the process of charging the capacitor from the power supply side. Furthermore, due to the residual voltage of the capacitor when the circuit is cut off, the voltage between the poles of the vacuum circuit breaker becomes higher than that of a general resistor/reactor load. The high-frequency, large-current rush current that occurs when the valve is turned on becomes a concentrated arc on the surface of the vacuum valve contact due to pre-arc chattering, melting the surface and causing craters and welding. This reduces the withstand voltage between the contacts. On the other hand, since a high recovery voltage is generated when the contact is opened, a discharge may occur between the electrodes after the current is cut off due to a drop in withstand voltage on the contact surface when the contact is turned on. This is generally called restriking. If a restriking occurs in the capacitor circuit, an overvoltage will be generated that will compromise the grid insulation. When the equipment insulation is destroyed by this overvoltage, the energy stored in the capacitor is discharged.

In order to prevent such a phenomenon from developing, the vacuum circuit breaker applied to the capacitor circuit must be designed to prevent restriking. For this reason, special measures are taken for vacuum circuit breakers, such as performing special aging treatments, using contacts with high withstand voltage, and increasing the gap length between contacts.

One of the countermeasures against this problem is to use two vacuum valves connected in series for each valve, and this method is used in some vacuum circuit breakers. In addition to the effect of increasing the apparent gap length of the vacuum circuit breaker, this is a countermeasure that focuses on the fact that the vacuum circuit breaker will stochastically re-ignite. In other words, the probability that two vacuum valves connected in series will re-ignite at the same time is very small for the vacuum circuit breaker as a whole, since a time factor is added to the probability of one valve re-igniting. This is aimed at the effect of increasing the incidence rate.

However, even if such measures are taken, when used for a long period of time, it is unavoidable that the contacts become rough due to inrush current, and restriking gradually becomes more likely to occur.

(Problems to be Solved by the Invention) As described above, when a vacuum circuit breaker having two vacuum valves in series is used in a capacitor circuit or the like for a long time, the surface of the vacuum valve contact becomes rough and the withstand voltage decreases. This makes restriking more likely to occur gradually.

An object of the present invention is to suppress the roughness of the vacuum valve contacts, suppress the drop in withstand voltage between the contacts, and reduce the occurrence of restriking.

[Structure of the Invention] (Means for Solving the Problems and Their Effects) The present invention changes the gap length of the vacuum valves by changing the lever ratio for operating two vacuum valves connected in series.
By always turning on one vacuum valve first,
An arc of inrush current that occurs when the vacuum valve is turned on is formed only between the contacts of the vacuum valve that is turned on later, so that roughness of the contacts occurs only in the vacuum valve that is turned on later.

As a result, the surface of the vacuum valve that is turned on first always maintains its initial state, suppressing a decrease in withstand voltage as a whole, and providing a vacuum circuit breaker that prevents the occurrence of restriking.

(Example) An example based on the present invention is shown in the figure. FIG. 1 shows a side view of the one-phase portion of the circuit breaker.

The vacuum valves 8a and 3b are arranged in a straight line with movable shafts 7a and 7b facing each other, and the force from the operating mechanism is distributed to each vacuum valve 3a and 3b at an intermediate portion between the vacuum valves Ba and Bb. It has become.

The operating force from the operating mechanism of the vacuum circuit breaker is applied to the insulated operating rod 1.
and is transmitted to the operating lever 2 via the drive pinch. The operating lever 2 is configured to be rotatable around a support pin 3. When the operating lever 2 rotates clockwise or counterclockwise around the support pin 3, the operating pins 5a and 5b attached to the operating lever 2 also rotate around the support pin 3, and this movement is caused by the wipe spring 5a, 6b to the movable shafts 7a, 7b of the vacuum valves 8a, 8b, and the movable shafts 7a, 7b move up and down.

At this time, a difference is provided in the distance between the support pin 3 and the operation pins 5a and 5b. In the figure, the distance between the support pin 3 and the operation pin 5a is longer than the distance between the support pin 3 and the operation pin 5b.

In the figure, when the insulated operating rod 1 is driven to the left in the figure, the operating force is transmitted to the operating lever 2 via the drive pinch, and the operating lever 2 rotates counterclockwise around the support pin 3. do. Along with this rotational movement, the operating pins 5a and 5b attached to the operating lever 2 also rotate counterclockwise. This movement is transmitted to the movable shafts 7a, 7b of the vacuum valves Ba, Bb via the wipe springs 6a, 6b. As a result, the movable shaft 7a moves upward, and the movable shaft 7b
is driven downward. As a result, the vacuum valves 8a, 8
The distance between each contact point b becomes smaller, and eventually they come into contact. At this time, if the intervals between the contacts are initially set to be the same, the displacement of the operating pin 5a is larger than that of the operating pin 5b, so the contacts of the vacuum valve 8a are closed before the vacuum valve 8b. Ru.

As described above, according to the present invention, the vacuum valve 8a is turned on before the vacuum valve 8b. When a vacuum circuit breaker with such a configuration is applied to an actual capacitor circuit, the result will be as follows. Even if one valve is turned on first, the power supply side and the capacitor circuit are not separated by the remaining vacuum valve, so no high-frequency, large-current rush current will flow through the circuit at this stage. When the closing operation progresses further and the remaining vacuum valve closes or the distance between the contacts reaches a distance that cannot withstand the circuit voltage, a high frequency, large current rush current flows into the circuit. At this time, the contacts of one vacuum valve are completely connected, so no arc is formed between the contacts.

However, since the other vacuum valve is on the verge of completing its closing, the pre-arc chattering causes an arc to be formed between the contacts, causing the contacts to become rough and melt. Since these are always limited to the vacuum valve 8b that is turned on later, the surface of the vacuum valve 8a that is turned on first is maintained in its initial state.

By doing so, the decrease in the withstand pressure of the vacuum valve is limited to the vacuum valve 8b, so that the withstand pressure close to the initial state is maintained for the vacuum circuit breaker as a whole, and the occurrence of restriking is suppressed.

In the above-mentioned embodiment, the contacts of the vacuum valve 8a, which is inserted first, are made of CuW material, which has high withstand voltage characteristics, and the contacts of the vacuum valve 8b, which is introduced later, are made of Cu material, which has high arc-extinguishing characteristics.
Use uCr contacts.

[Effects of the Invention] According to the present invention, the occurrence of restriking can be suppressed by changing the gap length of the contacts of vacuum valves connected in series.

[Brief explanation of the drawing]

FIG. 1 is a side view showing the configuration of a vacuum valve according to the invention. 1... Insulated operating rod 2... Operating lever 3... Support pin 4... Drive pin 5a , 5b...... Operation pins 6a, 6b...
・・・・・・Wipe springs 7a, 7b・・・・・・・
・Movable axis

Claims (1)

[Claims] In vacuum circuit breakers that use vacuum valves connected in series,
A vacuum circuit breaker characterized by having different gap lengths for each vacuum valve.