JPS61263015A - Vacuum drop detector for vacuum interrupter - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for detecting a decrease in the degree of vacuum in a vacuum interrupter, and in particular detects a decrease in the degree of vacuum by using an impedance change between a grid potential member and an intermediate shield. Regarding equipment.

B6 Summary of the Invention The present invention provides a vacuum interrupter vacuum level drop detection device that detects a vacuum level drop using impedance changes between a grid potential member and an intermediate shield. By determining whether the degree of vacuum has decreased based on a change in the voltage waveform of the voltage waveform, and storing this determination signal, it is possible to detect the decrease in the degree of vacuum before it reaches a pressure that cannot be shut off, and to prevent the decrease in the degree of vacuum from occurring rapidly. This also enables reliable detection.

C1 Conventional technology Vacuum incretors have a longer lifespan than other switching devices, both mechanically and mechanically, and require almost no maintenance. In addition to the accompanying drop in vacuum level, although very rare, the vacuum level may drop rapidly due to vacuum leakage from bellows, airtight joints, etc.

The vacuum interrupter (current interrupter) has a lower vacuum level and thus has lower interrupting performance, and eventually becomes unable to interrupt. Therefore, the degree of vacuum of the vacuum interrupter is required to be checked periodically or constantly.

Furthermore, it is desired that the vacuum interrupter can accurately and easily test the degree of vacuum in a charged state after being assembled with an operating mechanism to form a vacuum breaker.

By the way, the degree of vacuum of the vacuum interrupter and the discharge starting voltage of the vacuum gap have a relationship similar to Paschen's law, as shown in FIG. In FIG. 2, the horizontal axis represents the internal pressure of the vacuum interrupter, and the vertical axis represents the discharge starting voltage, and the solid line (partially broken line) in the figure shows the characteristics when the vacuum gap is 101 m. As can be seen from Figure 2, the degree of vacuum inside the vacuum interrupter is 10-'Fllll Hg (13,
The high vacuum tear lever discharge starting voltage of 33 mPa or less is extremely high. However, the degree of vacuum deteriorated to 10″″H
g (13.33 pa), it decreases to 500 ■.

Conventionally, in order to monitor the degree of vacuum in the charging state by utilizing such a law, the connection between the system potential members such as electrodes and the intermediate/lead in the open state or closed state of the vacuum interrupter has been proposed. There is a method that detects a decrease in the degree of vacuum from the change in ground voltage between the two.

FIG. 3 shows a case where detection is performed from the voltage change of the load side electrode when the contact is opened. The vacuum interrupter 1 has a fixed electrode 2 on the grid line side and a movable electrode 3 on the load side. The vacuum level drop detection device for this vacuum interrupter 1 includes a voltage detector 4 which is connected to the ground voltage of the movable electrode 3 as a series circuit of an impedance element for detecting the level, and a voltage detector 4 which is connected to the ground voltage of the movable electrode 3 in a series circuit of an impedance element that detects the level. The detection level is the grid line voltage (fixed electrode 2
A determination circuit 5 is provided which determines whether the degree of vacuum has decreased based on whether the voltage has risen to a level corresponding to 1C8.

In such a configuration, as the degree of vacuum in the vacuum interrupter 1 decreases, the discharge starting voltage between the electrodes 2 and 3 decreases, and eventually a flashover occurs between the electrodes 2 and 3. That is, a discharge occurs between electrodes 2 and 3 due to a decrease in the degree of vacuum, and the voltage I of electrode 3 increases.
! ! , increases, and finally the voltage of electrode 2]! 11, and a decrease in the degree of vacuum is detected by detecting an increase in the voltage E.

FIG. 4 shows a case where detection is performed from a change in the ground voltage of the intermediate shield. In the figure, intermediate shield 1 (metal #)
60 ground voltage E is detected by the voltage detector 7, and based on the change in this detection level, the determination circuit 5 obtains an output for determining whether or not the degree of vacuum has decreased.

This detection □ device has 2.3 electrodes compared to the one in Figure 3.
As long as the electrode 2 is charged, a decrease in the degree of vacuum can be detected regardless of whether the electrode 2 is in an open state or a closed state.

Problems that D0 invention attempts to solve The conventional vacuum level drop detection device detects the voltage K of the electrode 3.

Or voltage 1 of intermediate shield 6! It detects i,
In both cases, a decrease in the degree of vacuum is determined from the change in the absolute value of the ground voltage. For this reason, it becomes susceptible to fluctuations in the system potential and superimposed high-frequency noise, and there is a problem in that the vacuum interrupter cannot detect the early stage of a decrease in the degree of vacuum, which has the interrupting ability.

In other words, if the vacuum level drop detection sensitivity is set high, erroneous detection will occur due to system potential fluctuations and noise, and conversely, if the detection sensitivity is set low, a flash short will occur between electrodes 2 and 3 or between electrode 2 and the intermediate shield. Since the vacuum interrupter cannot be detected until the voltage is reached, the vacuum interrupter is already in a state where it cannot be shut off.

In addition, with conventional detection devices, if the degree of vacuum rapidly decreases due to a vacuum leak due to a pinhole, etc. that occurs in the bellows, and the pressure rises to near atmospheric pressure, there is a problem that detection of a decrease in the degree of vacuum will fail. . That is, when the degree of vacuum decreases to near atmospheric pressure, as shown in the Paschen characteristic in Figure 2 above, at the atmospheric pressure point P, the discharge starting voltage that once decreased according to the characteristic recovers and the withstand voltage characteristics change. is good to some extent, so if, for example, the operating voltage of the vacuum interrupter is lower than the system potential ■ in FIG. 2, the judgment output of the detection device will incorrectly judge that the degree of vacuum is good.

Means for Solving Problem E0 The present invention has been made in view of the above problem E, and includes a vacuum interrupter [a first detector for detecting the ground voltage waveform of a grid potential member connected to the vacuum interrupter], and an intermediate shield. a second detector for detecting a ground voltage waveform; a determination circuit that obtains a determination signal of a decrease in the degree of vacuum of the vacuum interrupter based on a change in the detection waveform of the second detector with respect to the detection waveform of the first detector; The vacuum degree drop detection device is provided with a memory holding circuit that stores and holds the judgment signal of this judgment circuit.

By memorizing and retaining the determination output of the 70 action determination circuit, the detection output is prevented from disappearing even when the degree of vacuum rapidly decreases to atmospheric pressure.

Further, by using the detected waveform of the grid potential member as a comparison standard for the detected waveform of the second detector, the influence of fluctuations in the grid potential and superimposed high-frequency noise can be eliminated.

In addition, detection by comparison of detection waveforms, that is, comparison of detection signals is not limited to amplitude (voltage) but also phase difference.

By comparative detection including waveform distortion, it is possible to detect a decrease in the degree of vacuum before it progresses to the point where it cannot be shut off. This point will be explained in detail below.

As a result of researching the correlation between the degree of vacuum and the voltage waveform of the intermediate shield in a vacuum interrupter, the inventors of the present invention found from experimental results that even in the early stages of decreasing the degree of vacuum, a phase change and a change in the amount of waveform distortion appear in the detected waveform. I was able to obtain it, and I was also able to obtain it as the calculation result from the isosynthetic circuit.

As an example of this experiment, the detected voltage waveform e3 of the intermediate shield 6 and the detected voltage waveform eI of the electrode 2 in FIG. 4 described above were observed, and these waveforms e3. 5 and 6 were obtained. FIG. 5 shows the waveform e1. when local discharge occurs at the beginning of the vacuum level decreasing (vacuum level PI shown in FIG. 2). e, is shown. In this case, the intermediate shield voltage waveform e,
The change in amplitude is small with respect to waveform e1, and waveform distortion and phase shift occur.

Figure 6 shows that the degree of vacuum further decreases (the degree of vacuum P shown in Figure 2,
) shows the waveform al l 83. At this time, discharge and flashover occur in each vacuum gap l, and waveform e with respect to waveform e has an increase in waveform distortion and phase shift (delay), as well as a rise in the peak value, and waveform e becomes waveform e. .

The amplitude will be close to .

The fact that the relationship between these waveform changes and the degree of vacuum can be considered to be based on the change in impedance between the electrode 2 and the intermediate shield 6 is based on computer calculations from any circuit, such as that shown in Figure 7. was also confirmed. In FIG. 7, the voltage IC of the electrode 2 is changed to the impedance element Z.
, , Z-, is detected as voltage e1 by the partial voltage of
The impedance between the electrode 2 and the intermediate shield 60 is defined as the capacitance C
8 and the discharge resistor R in parallel, and the voltage ll113 of the intermediate shield 6 is connected to the capacitor O□0. When the voltage e is detected by the partial pressure of the voltage e, and the decrease in the degree of vacuum is simply a decrease in the discharge resistance, the phase shift of the voltage e with respect to the voltage e is 03=100 pF, and the calculation results shown in Figure 8 are obtained. . The figure also shows the ground voltage es due to the change in resistance R.
It also shows the level change of (intermediate 7-wave voltage).

Based on the experimental examples and the calculation results from several circuits, we can detect a decrease in the degree of vacuum at its initial stage (the degree of vacuum at which the vacuum interrupter has the ability to interrupt) by monitoring changes in the detected waveform, especially changes in phase shift or waveform distortion. It turns out that it is possible to detect this.

G. Example FIG. 1 is a circuit diagram showing one embodiment of the present invention.

Reference numeral 1 denotes a vacuum interrupter that includes a metal intermediate shield 6 insulated from the fixed electrode 2 and the movable electrode 3. The vacuum level drop detection device of this vacuum interrupter 1 includes a fixed electrode 20 connected to the system line, a first detector 8 consisting of a series circuit of impedance elements z, y, and z2 for detecting the divided voltage waveform of the ground voltage, and an intermediate shield. A second detector 7 consisting of a series circuit of capacitors C, , C, which divides and detects the ground voltage waveform of 6, and a second detector 7 using the detected waveform of the first detector 8 as a comparison base single input. A digital or analog phase shift determination circuit 9 that detects that a change in phase shift of the detected waveform exceeds a predetermined angle; a storage circuit 10 that stores the determination output of this determination circuit 9; and this storage circuit. An alarm device 11 is provided which generates an alarm for a decrease in the degree of vacuum at the same time as the storage operation in step 9 is performed.

In such a configuration, electrodes 2 and 3 are in an open state.

Regardless of the closed state, as long as the electrode 2 is in a charged state, a ground voltage appears on the intermediate shield 6, and a detected waveform of fj7J is obtained together with the detected waveform of the detector 8.

The detection waveforms of these rain detections a8 and 7 are similar to the system line voltage waveform, and the rain detection waveforms change at the same rate when line voltage fluctuations and double superimposed high frequency noise occur. Therefore, by using the voltage e1 as a reference for determining the degree of vacuum reduction based on the change in the detected waveform by the determination circuit 9, voltage fluctuations can be avoided.

Detection is performed with the influence of noise removed.

Then, the determination circuit 9 makes a determination based on the amount of change in the phase shift between the detection voltages 01.03, and detects the decrease in the degree of vacuum before it progresses to the point where it cannot be shut off (approximately the degree of vacuum P1 in FIG. 2). Furthermore, by storing and retaining the judgment output from the judgment circuit 9 in the memory holding circuit 10, even when the degree of vacuum in the vacuum interrupter rapidly decreases and reaches atmospheric pressure, the judgment signal of the decrease in the degree of vacuum is maintained, and the alarm is activated. 11 alarm operation continues.

Embodiment I shows a case in which the degree of vacuum is determined from a change in phase shift, but this can also be determined from a change in waveform distortion, or a combination of both, or even a change in amplitude. Of course, it is possible to obtain a more reliable determination by using a configuration that does this.

In addition, in the embodiment, the structure of the vacuum interrupter 1 is provided with a vacuum gap between the intermediate shield and the grid potential member that discharges in a vacuum range where the vacuum level can be cut off when the vacuum level is low. This can be made even more reliable. The reason for this will be explained in detail below.

The inventors of the present invention investigated the discharge phenomenon in a vacuum interrupter and obtained the characteristics shown in FIG. In Figure 9, the horizontal axis represents the vacuum interrupter internal pressure.

The vertical axis represents the discharge starting voltage. In FIG. 9, solid line 14. Solid lines 15 and 16 indicate the characteristics of vacuum gaps A, B, and O, respectively, and the gap lengths have a relationship of A>B>O.

It was generally known that a long gap has a higher discharge starting voltage than a short gap, but as can be seen from Figure 9, this is a phenomenon in high vacuum or near atmospheric pressure.
In the region around 10-'' Iuug (1,333 Pa), on the contrary, the discharge starting voltage is higher in the short gap than in the long gap.

Due to this phenomenon, that is, the phenomenon that the discharge starting voltage between the long gap and the short gap is reversed, the fixed electrode 2 and the intermediate shield 6
The gap length between the fixed electrode 2 and the movable electrode 3 is set to be a long gap that discharges in the early stage of vacuum reduction and in the vacuum range where it can be cut off (for example, the actual IVi114 in FIG. 9), and the opening gap between the fixed electrode 2 and the movable electrode 3 and the By making the gap between the electrode 3 and the intermediate shield 6 short (solid line 16 in FIG. 9), the gap between the intermediate shield and the intermediate shield in the vacuum region S or S, as shown in FIG. A discharge can be obtained, which results in a large amount of change in the detected waveform at the beginning of the vacuum level drop, making detection even more reliable.

■0 Effects of the Invention As described above, according to the present invention, a decrease in the degree of vacuum of the vacuum interrupter is detected from the deformation of the ground voltage waveform of the intermediate shield with respect to the ground voltage waveform of the line, and this detection signal is stored and retained. Therefore, it is possible to detect the early stage of the vacuum level decrease (before it becomes impossible to shut off). Furthermore, by storing the detection signal, it is possible to reliably obtain a detection output and an alarm even when the degree of vacuum drops rapidly. Furthermore, by making the vacuum interrupter equipped with a vacuum gap that discharges at the beginning of the vacuum level decreasing,
This makes it possible to more reliably detect the initial stage of a decrease in the degree of vacuum.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a characteristic diagram based on Paschen's law, Figs. 3 and 4 are circuit diagrams of a conventional detection device, Figures 5 and 6 are diagrams showing changes in the line voltage detection waveform as the degree of vacuum progresses, and changes in the intermediate shield voltage detection waveform, and Figure 7 shows changes in the detection waveform due to changes in the impedance of the intermediate shield. The equivalent circuit diagram, FIG. 8 is a characteristic diagram of the phase and amplitude obtained from FIG. 7, and FIG. 9 is a characteristic diagram showing the relationship between the internal pressure of the vacuum interrupter and the discharge starting voltage when the vacuum gap length is different. 1... Vacuum interrupter, 2... Fixed electrode, 3...
Movable electric sign, 6... Intermediate shield, 7... Second detector, 8... First detector, 9... Phase determination circuit, 1
0...Memory retention circuit, 11...Alarm device. Figure 1 Actual one-row circuit m 1゜1... Kanjo I〉? Ubuy B-' Eagle 1 Nosuni output 2...Fixed electrode 9...Zoryo circuit 3
... Town vJ Den f & 10... Distribution 4! (Amazing special milk 6゛°
゛Middle Shield 11...Alarm and 7゛・Real 2
Fig. 3 Schematic diagram of the equipment used to cut the earth Fig. 4 Schematic diagram of the device for detecting debris Fig. 5! U each voltage and shield voltage between φ Pressure and Φ silt @ pressure 5 anti-gami Fig. 7 5 tar > H 1 oxs.

Claims (2)

[Claims] (1) In a device for detecting a decrease in the degree of vacuum of a vacuum interrupter that includes a metal intermediate shield insulated from a grid potential member, a first device detects a ground voltage waveform of a grid potential member connected to the vacuum interrupter. a second detector that detects the ground voltage waveform of the intermediate shield; and a degree of vacuum of the vacuum interrupter based on the amount of change in the detected waveform of the second detector with respect to the detected waveform of the first detector. A device for detecting a decrease in the degree of vacuum of a vacuum interrupter, comprising a determination circuit that obtains a determination signal for determining a decrease, and a memory holding circuit that stores and retains the determination signal of the determination circuit. (2) The vacuum interrupter is provided with a vacuum gap between the intermediate shield and the grid potential member, which discharges when the degree of vacuum decreases and in a vacuum degree region where interruption is possible. A device for detecting a decrease in the degree of vacuum of a vacuum interrupter as described in 2.