JPH0471130A - Three-phase vacuum circuit breaker - Google Patents

Abstract

PURPOSE:To open a vacuum circuit breaker near the zero-current point twice in one cycle in either one phase, interrupt a large current, and suppress the occurrence of surges by opening the vacuum circuit breaker while individual phases are drifted by the preset phase angle when the vacuum circuit breaker is opened. CONSTITUTION:When a trip signal is inputted while a vacuum circuit breaker is closed, a motor is activated, and a cam 9 is rotated clockwise. A roller 10a is moved by the rotation of the cam 9 from the position hooked by a tip hook section 92 to the position hooked by a step section 91. The moving shaft 6 of a vacuum valve 4 is moved downward via a link 10, an action rod 11 and a wipe spring 12 to open contacts while the roller 10a is moved from the tip to the step section. Cams 9a, 9b, 9c of individual phases are displaced by the preset angle and fitted to a main shaft 8, and the vacuum valves of individual phases are displaced by the preset phase angle and opened when a vacuum circuit breaker is opened.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) This invention opens and closes each line of three-phase alternating current using three contacts sealed in a vacuum container of 1O-2Pa or less. The present invention relates to three-phase vacuum circuit breakers, and in particular to suppressing switching surges and improving withstand current characteristics.

(Prior Art) Vacuum circuit breakers have excellent arc-extinguishing properties and are therefore applied to many circuits. However, although it has excellent arc-extinguishing characteristics, it has the drawback of generating a peculiar switching surge when a small current is interrupted. For this reason, when vacuum circuit breakers are applied to circuits where switching surges are a concern, they have been used without problems in actual use by installing a surge protection device that suppresses the generated surges.

On the other hand, a "low surge vacuum circuit breaker" has been developed as a vacuum circuit breaker that can be applied to various circuits without a surge protection device. This reduces the arc-extinguishing characteristics of the vacuum circuit breaker and reduces the cutting current value, which is the main cause of surge generation.

However, since this low-surge vacuum circuit breaker has reduced arc-extinguishing characteristics to suppress surge generation, there is a limit to its ability to interrupt large currents that flow in the event of a short circuit or the like.

Currently developed low-surge vacuum circuit breakers have a large current interrupting limit of approximately 20 kA. Therefore, the short circuit current is 3
Vacuum circuit breakers that require 1.5 kA or more have been equipped with surge protection devices to solve the problem of opening/closing surges.

This is because the "low-surge vacuum circuit breaker" reduces the arc-extinguishing characteristics and suppresses the occurrence of surges, which causes the contacts to become rough due to arcing when interrupting large currents, leading to arc concentration and a reduction in insulation recovery after the current is extinguished. As a result, it is difficult to realize a vacuum circuit breaker that can handle a large current and satisfy low surge characteristics because it cannot withstand the recovery voltage after the current is extinguished.

In addition, in a vacuum circuit breaker, when a cutting surge caused by current cutting occurs in a small gap between contacts, the withstand voltage between the gaps of the contacts may not be able to withstand the cutting surge, resulting in re-ignition. This re-ignition causes a large surge called multiple re-ignition or three-phase simultaneous shutdown. For this reason,
In low-surge vacuum circuit breakers that keep the cutting current value low, the problem is not so much the cutting surge but the surge caused by multiple re-ignitions and three-phase simultaneous shutdown (Proceedings of the Institute of Electrical Engineers of Japan Vol. 1.93,
No. 8).

In order to prevent these surges from occurring, it is best to remove the vicinity of the current zero point of each phase and open the contacts, but in a three-phase vacuum circuit breaker, the contacts are normally opened for each phase almost simultaneously (opening). Since the deviation time is approximately 0 to 3 ms or less), there are six opportunities for any phase to open near the current zero point within one cycle, and the range of phases that can actually be opened is extremely limited. Very high precision phase control is required.

(Problems to be Solved by the Invention) As described above, in a low-surge vacuum circuit breaker, contact roughness and multiple re-ignitions in a small gap length region occur when interrupting a large current.
It is necessary to suppress simultaneous shutoff of three phases, and when controlling the opening phase by performing phase control on these, very highly accurate phase control is required.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a vacuum circuit breaker that is capable of interrupting large currents using a phase control method with low accuracy and suppressing surge generation.

[Structure of the invention]

(Means for Solving the Problems) In the first basic invention, in a three-phase vacuum circuit breaker that opens and closes each three-phase AC line, the opening timing of each of the three contacts is adjusted to the current phase of each line. Opening phase difference control means is provided to shift the current phase by 120° or to shift the current phase by 60° in the opposite phase.

In addition to this configuration, in the second invention, the current in the line is detected, and when the current is relatively large, the contact is opened at a phase timing near the zero point of the current, so that the current is relatively large. If the current is small, an opening phase control means is provided to open the contact at a phase timing that deviates from the vicinity of the zero point of the current.

(Function) According to the present invention, when opening a vacuum circuit breaker, each phase opens with a predetermined phase angle difference, and there is no chance of opening near the zero current point in any phase within one cycle. This is 1/3 chance of opening twice and each phase almost simultaneously, and the range of phases that open outside the vicinity of the current zero point becomes wider. Also, depending on whether the current flowing in the main circuit is a large current or a small current, it may be near the zero current point (within 30 degrees around the zero current point) or outside the zero current point (over 30 degrees around the zero current point). range), the vacuum circuit breaker will be opened. Therefore, it is possible to interrupt large currents and suppress the occurrence of surges.

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

In the figure, the vacuum circuit breaker includes a frame 1 that is movable with wheels 1a, an insulating support frame 2 fixed to the frame 1, and an operating mechanism 3 fixed to the front side of the insulating support frame 2. 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 is provided with a main shaft 8 connected to an internally mounted motor (not shown) by an appropriate torque transmission means, and a cam 9 is mounted on the main shaft 8 so as to rotate together with the main shaft 8. This cam 9 is connected to the roller 10.
It is connected to the link 10 via a. This link 10
is rotatably supported by the insulating support frame 2, with the − side (upper side)
is connected to the movable shaft 6 of the vacuum valve 4 via an operating rod 11 and a wipe spring 12, and the other side (lower side) is connected to an opening spring 13 whose tension can be adjusted.

The cam 9 is provided with a stepped portion 91 as shown in FIG. Here, the cam 9, the roller 10a, the link 10, the operating rod 11, and the wipe spring 12 are each independently provided as a set for each phase vacuum valve of the three-phase vacuum circuit breaker. 9a, 9b, and 9c are each attached to the main shaft 8 with a predetermined angle shift about the main shaft 8. This shift is the essential part of the opening phase difference control means.

FIG. 2 is a diagram showing the relationship between the opening phase of the vacuum valve of each phase and the current of each phase of the vacuum circuit breaker according to the present invention, and shows the relationship between the cams 9a, 9b, and 9c of each phase with the main shaft 8 as the rotation center. Due to the provided deviation in the rotational direction, a deviation occurs in the opening phase of each phase. This shift is set so that if the phase of the first opened phase is at the zero current point, the other two phases will also be at the zero current point. That is, as shown in FIG. 2, the opening phase of the vacuum valve of each phase of the vacuum circuit breaker 2 is 12 degrees, which is the same as the electrical angle.
It is shifted by 0' or by 60° in the opposite order to the electrical angle shift.

The operation of the embodiment configured as above will be explained. 1st
When a trip signal is input with the vacuum circuit breaker in the closed state shown in the figure, a motor (not shown) is started and rotates the cam 9 clockwise in the figure. This rotation of the cam 9 causes the roller 10a to move from the position where it is locked by the tip locking part 92 to the position where it is locked by the step part 91. While the roller 10a moves from the tip to the step, the link 10 and the operating rod 1
1. The movable shaft 6 of the vacuum valve 4 is moved downward via the wipe spring 12, and the contacts are opened. At this time, the cams 9a, 9b, and 9c of each phase are attached to the main shaft 8 with a predetermined angle shift, so when the vacuum circuit breaker is opened, the vacuum valve of each phase is opened with a predetermined phase angle shift. . At this time, the relationship between the current of each phase and the opening point is as shown in Figure 2,
When the vacuum valve of either phase opens near the zero current point, the vacuum valves of the other two phases also open near the zero current point. Conversely, when the vacuum valve of either phase deviates from the vicinity of the current zero point and opens, the other two phase vacuum valves also deviate from the vicinity of the current zero point and open. For this reason, there are two opportunities for one cycle to open near the current zero point.
times, and the range of phases that open near the current zero point becomes narrower. On the other hand, as shown in Figure 3, in a conventional three-phase vacuum circuit breaker, each phase opens almost simultaneously (opening deviation time is 0 to 3
ms or less), there are six opportunities for one of the phases to open near the zero current point within one cycle, and the range of phases that open near the zero current point becomes very wide.

When a small current is interrupted by a low-surge vacuum circuit breaker with reduced arc-extinguishing characteristics, the cutting current does not become completely zero, but becomes a small cutting current. Therefore, if the vacuum circuit breaker opens at a phase lower than this cutting current, current cutting will occur at the same time as the opening, causing a cutting surge. Since the gap length of the vacuum bulb at this time is minute, electric discharge occurs between the gaps due to cutting surges, causing re-ignition. This causes a large surge to occur. Therefore, if the opening point of the vacuum circuit breaker 2 is in phase equal to or higher than the cutting current value, current cutting will not occur immediately after the vacuum circuit breaker 2 opens, and when current cutting occurs, the vacuum circuit breaker 2 will Since the gap length is wide enough to withstand the cutting surge that occurs,
It is possible to prevent the phenomenon from developing into a large surge.

This is illustrated in FIG. 4. Furthermore, the maximum cutting current of a vacuum circuit breaker is determined by the arc extinguishing characteristics of the vacuum circuit breaker. Also, the circuit current is determined by the load. The phase angle at which the vacuum circuit breaker opens below the maximum cutting current value is within the phase range of the current zero point portion 2φ1.

In this embodiment, as shown in Fig. 2, the opening phase is shifted by a predetermined angle, so the relationship between the current phase of each phase and the opening phase is exactly the same for each phase, and the opening phase is first shifted. It is sufficient if the phase satisfies the open phase condition. Therefore, there are two opportunities for opening in the 2φ1 region near the zero current point in one cycle, and the range of phases in which the contact opens near the zero current point is 2×2φ1.

This range is as shown in Figure 3, in a normal three-phase vacuum circuit breaker, each phase opens almost simultaneously (opening deviation time is 0 to 3 m).
s or less), there are six opportunities for any phase to open near the zero current point within one cycle, and the range of phases that open near the zero current point is extremely wide, 6×2φ1. It turns out that this is a very narrow range compared to what happens.

The range of the phase that opens near the current zero point is, for example, φ1
-15', it is 60'' in this embodiment, whereas it is 180'' in the conventional three-phase vacuum circuit breaker, which shows that the effect of shifting the opening phase by a predetermined angle is great.

With the above means, the probability of opening at a phase near the current zero point where a surge occurs when interrupting a small current is reduced to 1/3 of that of a conventional vacuum circuit breaker. Therefore, the probability that a surge will occur due to multiple re-ignition or three-phase simultaneous shutdown is 173 times that of a conventional vacuum circuit breaker, and the occurrence of opening/closing surges is suppressed.

Next, a second invention in which the above-mentioned opening phase control means is added will be explained according to the embodiment shown in FIG.

In FIG. 5, a main circuit 5 to which a vacuum circuit breaker 52 is connected
The detection output of a current sensor 53 such as a current transformer installed at the terminal 1 is input to a discrimination circuit 54 and a synchronizing signal generation circuit 55. After rectifying and smoothing the detection output of the current sensor 53, the determination circuit 54 determines whether the current is a large current equivalent to a short circuit current or a small current equivalent to several tens of amperes. Discrimination circuit 54
The outputs of the first and second delay time setting circuits 56 and 57
The information is entered into the respective fields. Discrimination circuit 54
Based on the determination result, when the current is small, the delay time setting circuit 5
A drive signal is output to 7. and,
The output of the delay time setting circuits 56 and 57 is the tripping circuit 58.
It is becoming more and more human-powered. Further, the output of the synchronizing signal generation circuit 55 is input to a tripping circuit 58, and the output of this tripping circuit 58 is inputted to the vacuum circuit breaker 52.

Here, the opening phase of the vacuum valve of each phase of the vacuum circuit breaker 2 is:
As shown in FIG. 2 described above, the electric angles are shifted by 120 degrees, the same as the electrical angles of three-phase AC, or they are shifted by 60 degrees in the reverse order of the electric angle shifts.

Further, the current flowing through the main circuit 51 is detected by a current sensor 53, and its detection output is input to a discrimination circuit 54 and a simultaneous signal generation circuit 55. The determination circuit 54 determines whether the current is a large current equivalent to a short circuit current or a small current equivalent to several 1 OA. Based on this determination result, if the current is large, the delay time setting circuit 5
A drive signal is applied to the delay time setting circuit 57, and if the current is small, the drive signal is output to the delay time setting circuit 57.

On the other hand, since the human power signal from the current sensor 53 is an AC waveform, the synchronization signal generating circuit 55 detects its zero point, generates a pulse signal, rectifies the pulse signal, and as a result, the human power signal 1 The same pulse signal is output every 2 cycles and is manually input to the tripping circuit 58.

Here, when the tripping signal of the vacuum circuit breaker 52 is input from the outside to the tripping circuit 58 as shown in FIG. 6, the first signal from the synchronizing signal generation circuit 55 is inputted after the tripping signal is input. The delay time setting circuit 56
Alternatively, the tripping signal of the vacuum circuit breaker 52 is output to the circuit breaker with a delay of the delay time t8 or t7 set in step 57. This output signal causes the vacuum circuit breaker 52 to
The contact is opened after the second operation time t2.

As described above, according to the embodiment shown in FIG.
It is possible to differentiate the current value flowing through the main circuit 51 into a large current and a small current, and open the polarity at a certain specific phase.

When a small current is interrupted by a low-surge vacuum circuit breaker with reduced arc-extinguishing characteristics, the cutting current does not become completely zero, but becomes a small cutting current. Therefore, if the vacuum circuit breaker opens at a phase lower than this cutting current, current cutting occurs simultaneously with the opening, and a cutting surge occurs. Since the gap length of the vacuum bulb at this time is minute, electric discharge occurs between the gaps due to cutting surges, causing re-ignition. This causes a large surge to occur. Therefore, if the opening point of the vacuum circuit breaker 2 is set to a phase higher than the cutting current value, current cutting will not occur immediately after the vacuum circuit breaker 2 opens, and when current cutting occurs, Since the gap length of the vacuum circuit breaker is wide enough to withstand the cutting surge that occurs, it is possible to prevent the phenomenon from progressing to a large surge.

This is illustrated in FIG. 6. The opening time t2 of the vacuum circuit breaker is determined by the mechanism of the circuit breaker. Furthermore, the maximum cutting current of a vacuum circuit breaker is determined by the arc extinguishing characteristics of the vacuum circuit breaker. Also, the circuit current is determined by the load.

The phase angle at which the vacuum circuit breaker opens below the maximum cutting current value is within the phase range of the current zero point portion 2φ1. Avoid this area
In order for the vacuum circuit breaker to open, it is only necessary to set the current zero point t□ so that t7+t2 does not fall within the 2φ1 region. Since t2 is a value determined by the circuit breaker, this condition is satisfied by setting t7.

On the other hand, when interrupting a large current, if a large current flows at the opening point, the contact will be seriously damaged. Therefore, contrary to surge suppression, if the contact is opened near the current zero point, the current value at the contact opening point is small, so damage to the contacts will be reduced. Figure 6 shows the relationship between the current values at which the vacuum circuit breaker can be disconnected when the current is opened in each phase. From this, rather than opening at the current peak value, it is closer to the current zero point (within 30'' around the current zero point)
It can be seen that it is possible to interrupt even a large current by opening the terminal at .

In this case, the sum of t6 determined by the delay time setting circuit 56 and the opening time t2 of the vacuum circuit breaker is 30'' around the current zero point.
The vacuum circuit breaker will open within this time.

By using the above measures, when interrupting a small current, avoid opening at a phase near the current zero point where a surge occurs, and when interrupting a large current, open at a phase near the small current zero point to prevent damage to the contacts. A surge vacuum circuit breaker can be provided, and at the same time, necessary and sufficient phase control can be performed without increasing the accuracy of phase control by shifting the opening phase of each phase by a predetermined angle.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to provide a vacuum circuit breaker that is capable of interrupting large currents using a low-accuracy, inexpensive phase control method and eliminates the generation of harmful switching surges.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of the basic first invention, FIG. 2 is a diagram showing the relationship between the current of each phase and the opening phase of the three-phase vacuum circuit breaker according to the invention, and FIG. A diagram showing the relationship between the current of each phase and the opening phase of a conventional three-phase vacuum circuit breaker, FIG. 4 is a diagram showing various signals at the time of small current interruption, and FIG. 5 is a diagram showing an embodiment of the second invention. The block diagram, FIG. 6, is a diagram showing the signals of various parts when a small current is interrupted in the configuration of FIG. 5, and FIG. 7 is a diagram showing the relationship between the opening phase and the current that can be interrupted. 3... Operating mechanism 4... Vacuum valve 8... Main shaft 9... Cam 10a... Roller 10... Link 51... Main circuit 52... Vacuum circuit breaker 53... Current Sensor 54...Discrimination circuit 55...Synchronizing signal generation circuit 56.57...Delay time setting circuit 58...Tripping circuit

Claims (2)

[Claims] (1) In a device that opens and closes each three-phase AC line using three contacts sealed in a vacuum container, the opening timing of the three contacts is set to 12 times in phase with the current phase of each line.
A three-phase vacuum circuit breaker, characterized in that it is provided with an opening phase difference control means that shifts the opening by 0° or by 60° in the opposite phase to the current phase. (2) In the three-phase vacuum circuit breaker according to claim 1, the current in the line is detected, and if the current is relatively large, the contact is opened at a phase timing near the zero point of the current, and the contact is opened at a phase timing near the zero point of the current. A three-phase vacuum circuit breaker, characterized in that, when the current is relatively small, opening phase control means is provided for opening the contact at a phase timing that deviates from the vicinity of the zero point of the current.