JPH0765676A - Vacuum-down detector of vacuum interrupter - Google Patents

Abstract

PURPOSE:To provide a vacuum down detector which accurately detects vacuum- down over the whole region of 0.03-10Torr without decrease the withstand voltage of a breaker. CONSTITUTION:A circular arc-shaped detector electrode 14 is installed in the vicinity of the circumference of a vacuum interrupter within the range where the withstand voltage of the vacuum interrupter is not decreased. Discharge pulse current is caught by the detector electrode, and sent to a vacuum detector to detect the vacuum-down of the vacuum interrupter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum degree drop detecting device for detecting a drop in vacuum degree inside a vacuum interrupter.

[0002]

2. Description of the Related Art Generally, a vacuum interrupter has a large difference in breaking performance depending on the degree of vacuum inside, and when the degree of vacuum is lowered, the breaking ability is lowered. Therefore, it is necessary to constantly monitor this degree of vacuum.

FIG. 4 is a schematic block diagram of a vacuum degree reduction detecting device for a vacuum interrupter. In the figure, 1 is a vacuum interrupter, which has a fixed lead having a fixed electrode 7a and a movable electrode 8a in a vacuum container composed of an insulating cylinder 2, 3, a metal cylinder 4 and end plates 5, 6. Movable lead 8
Are opposed to each other. An arc shield 9 is provided to prevent the insulating cylinders 2 and 3 from being contaminated by the metal vapor generated when the electrodes 7a and 8a are separated.

Reference numeral 10 denotes a circular flat plate-shaped or disk-shaped detection electrode provided outside the vacuum interrupter so as to face the arc shield 9, to which one end of a lead wire 11 made of a coaxial cable is connected and the other end of the lead wire 11 is connected. Is connected to the vacuum monitoring device 12.

The vacuum degree monitoring device 12 detects the discharge pulse current generated when the vacuum of the vacuum interrupter 1 is lowered by the disc-shaped detection electrode 10 and inputs it to the current / voltage conversion circuit 12a, which is supplied to the discharge frequency band. Selection and rectification circuit 12b
Rectification is performed, and the determination circuit 12c determines a vacuum abnormality based on the voltage level and the duration time. If the voltage level and the duration time are equal to or greater than a preset reference value, the alarm circuit 1
An output signal is output to 2d, an alarm lamp L (or a buzzer) is turned on, and an alarm contact output S is sent to a transmission device.

The discharge pulse current is a capacitance between the electrodes 7a and 7b in the vacuum interrupter 1 and the arc shield 9, a capacitance between the arc shield 9 and the detection electrode 10, and between the detection electrode 10 and the vacuum monitoring device 12. Although determined by the capacitance of the lead wire 11, if the capacitance between the arc shield 9 and the detection electrode 10 is larger, the discharge pulse current can be captured as a large signal.

FIG. 5 shows a vacuum interrupter 1 and a detection electrode 10.
The vacuum discharge characteristics (Paschen curve) when the distance between the electrodes is 30 mm, the horizontal axis represents the degree of vacuum (Torr), and the vertical axis represents the discharge starting voltage (kV).
This is the case where a and 7b are closed and the b curve is open.

[0008]

When the electrodes in the vacuum interrupter 1 are in the open state, the detection range of the vacuum degree reduction by the vacuum degree monitoring device 12 is as shown by the curve b in FIG.
The discharge start voltage is low and it is easy to catch the discharge pulse current, but in the closed state, the discharge start voltage becomes high as shown by the curve a and it becomes difficult to detect. 03-0.07 Torr, 1.0-1
In the range of 0.0 Torr, it is difficult to detect in the so-called Paschen curve characteristic valley region PV in the range of 0.07 to 1.0 Torr.

The upper part of FIG. 3B shows the detected discharge pulse current when the electrodes 7a and 8a are closed and the degree of vacuum is reduced to 0.4 Torr. The current value is small and it is difficult to distinguish it from noise. , Accurate detection is difficult.

In order to improve the detection accuracy, the diameter of the detection electrode may be increased, or the detection electrode may be brought closer to the vacuum interrupter and the distance to the arc electrode may be shortened. (External flashover of the vacuum interrupter section) and there is a limit.

In view of the above points, the present invention expands the detection range of the degree of vacuum reduction without lowering the withstand voltage, and even when the electrode is closed, the degree of vacuum in the entire range of 0.03 to 10.0 Torr can be obtained. It is an object of the present invention to provide a detection device of this kind that can detect a drop with high accuracy.

[0012]

Means for solving the above-mentioned problems in the present invention are as follows. A detection electrode is provided outside the vacuum interrupter at a predetermined interval, and the detection electrode generates when the vacuum degree of the vacuum interrupter decreases. In the vacuum degree decrease detecting device, the discharge level is detected as a discharge pulse current, and when the current level is converted into a voltage and the voltage level reaches a preset reference level, it is determined that there is a vacuum abnormality. Are formed in an arc shape along the outer diameter of the vacuum interrupter at substantially equal intervals.

[0013]

As described above, since the detection electrodes are formed in an arc along the outer diameter of the vacuum interrupter at substantially equal intervals, the capacitance with the arc shield in the vacuum interrupter increases and the electrode in the vacuum interrupter opens. Of course, the vacuum drop can be detected over the entire range of 0.03 to 10.0 Torr even when it is closed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

FIG. 1 is an explanatory view showing an embodiment of the present invention.
FIG. 2 is a plan view of the three-phase AC circuit breaker (only the vacuum interrupter with the container removed), and FIG. 2 is a right side view of the same.

In these drawings, 1 is a vacuum interrupter, 14 is a detection electrode, 11 is a part of the detection electrode 14, one end of which is connected, and the other end is the vacuum degree monitoring device 12 shown in FIG.
Is a lead wire connected to.

The detection electrode 14 is formed in an arc shape, and is provided close to the outer circumference of the vacuum interrupter 1 along the outer diameter thereof at the same distance d within a range that does not reduce the withstand voltage of the vacuum interrupter 1, Moreover, the length L of the detection electrode 14 is as long as possible in the direction along the axis of the vacuum interrupter 1,
Further, the central angle θ surrounding the vacuum interrupter 1 is made as large as possible.

In the case of the three-phase AC circuit breaker as shown in the figure, the interval between the vacuum interrupter 1 and the adjacent phase is made as narrow as possible without lowering the withstand voltage, and the circuit breaker is downsized and detected. Electrode 14 is vacuum interrupter 1
Considering that the central angle that surrounds is as large as possible, the optimal central angle θ is 100 to 120 °.

FIG. 3 is an oscillograph of the discharge pulse current when the vacuum degree of the vacuum interrupter in SF ₆ gas of a three-phase AC circuit breaker using a vacuum interrupter is reduced to 0.4 Torr. In the case of the arc-shaped detection electrode according to the above, FIG. 7B shows the case of the conventional disc-shaped detection electrode, where i _P is the discharge pulse current and V is the applied voltage.

In the experiment, the diameter φ of the vacuum interrupter is 94.
mm, the distance d between the vacuum interrupter and the detection electrode is 4
Under the same condition that the electrode inside the vacuum interrupter is 0 mm and the vacuum degree of the vacuum interrupter is 0.4 Torr, the length L of the detection electrode is 80 m in the case of FIG.
m and the width W are 100 mm, and in the case of FIG. 7B, the detection electrode has a disc-shaped diameter of 125 mm.

As can be seen from this figure, in the present invention, the discharge pulse current i _P can be greatly captured, which is clearly distinguished from the noise signal and enables highly accurate detection.

Similarly, the degree of vacuum is changed to 0.03 to 1
Although it was detected over the entire range of 0.0 Torr, the present invention was able to detect over the entire range, but the conventional detection electrode could not accurately detect the range of 0.07 to 1.0 Torr.

[0023]

As described above, the vacuum degree reduction detecting device according to the present invention has a simple shape, but the vacuum interrupter is provided in the entire region of the Paschen curve, that is, 0.03 to 10 Torr. This has an extremely excellent effect of being able to detect a decrease in the degree of vacuum with high accuracy.

[Brief description of drawings]

FIG. 1 is a plan view of a main part of a three-phase AC circuit breaker according to an embodiment of the present invention.

FIG. 2 is a right side view of the same.

FIG. 3 is an oscillograph for detecting a discharge pulse current. (A) is the case according to the present invention. (B) In the case of the conventional example.

FIG. 4 is an explanatory diagram of a vacuum degree reduction detecting device for a vacuum interrupter.

FIG. 5 is a vacuum discharge characteristic diagram of a vacuum interrupter.

[Explanation of symbols]

 1 ... Vacuum interrupter 12 ... Vacuum degree monitoring device 14 ... Detection electrode L ... Electrode length θ ... Electrode central angle

Claims (1)

[Claims] 1. A detection electrode is provided outside the vacuum interrupter at a predetermined interval, the discharge generated when the vacuum degree of the vacuum interrupter is lowered is detected by the detection electrode as a discharge pulse current, and the current is input to a vacuum monitoring device. Then, in the vacuum degree drop detecting device for judging a vacuum abnormality when the reference level set in advance by the vacuum monitoring device is reached, the detection electrodes are arc-shaped along the outer diameter of the vacuum interrupter at substantially equal intervals. A vacuum degree reduction detecting device for a vacuum interrupter, which is characterized in that