JPH1092277A - Vacuum-down detecting device for vacuum valve type opening/closing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sense the reduction of the degree of vacuum of a vacuum valve via the detection of an abnormal discharge by providing a built-in outer electrode exposed on the outside of an insulating container to face a metal shield held in the insulating container, and providing a voltage dividing capacitor between the outer electrode and the ground. SOLUTION: A metal shield 7 surrounding a pair of contact pieces 2, 3 at intervals is provided inside the cylindrical insulating container 35 of the vacuum valve 41 of an opening/closing device connected to a three-phase AC power system. A cylindrical outer electrode 42 buried in a container wall is provided on the outer periphery of the insulating container 35 to face the metal shield 7, and an outer terminal 42A exposed on the outside is connected to the ground via a voltage dividing capacitor. An abnormal discharge between both contact pieces 2, 3 and the metal shield 7 is detected by the voltage dividing capacitor, and the reduction of the degree of vacuum of the vacuum valve 41 is sensed. The reduction of the degree of vacuum of the vacuum valve 41 can be accurately sensed by a simple and small vacuum-down detecting device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching device such as a vacuum circuit breaker or a vacuum switch using a vacuum valve, which detects a decrease in the degree of vacuum of the vacuum valve by electrically detecting an abnormal discharge inside the vacuum valve. The present invention relates to an apparatus for detecting a decrease in vacuum degree.

[0002]

2. Description of the Related Art A vacuum circuit breaker and a vacuum switchgear use a highly degassed and evacuated completely sealed vacuum valve in a portion corresponding to an arc extinguishing chamber of another circuit breaker. Vacuum is an ideal insulating medium, but its function cannot be exerted when the degree of vacuum is reduced. Therefore, the reliability of vacuum valves occupies a large weight in the reliability of vacuum circuit breakers and vacuum switches. I have.

[0003] Therefore, in order to ensure high reliability in the manufacture of vacuum valves, management of the manufacturing process such as selection and purchase of materials, processing accuracy and degassing treatment, and performance confirmation tests and inspections from the acquisition of materials to product shipment are strict. Quality control is implemented. In particular, the control of the degree of vacuum of the vacuum valve is the most important, and careful management is performed for all the valves. FIG. 4 is a view for explaining the principle of the cause of the decrease in the degree of vacuum of the vacuum valve. The vacuum valve sealed at the time of manufacture is 10 ^-6 to 10 ^-7.
The internal gas release is maintained at a high vacuum of about Torr, but the gas molecules remaining inside the vacuum vessel, electrodes and conductors constituting the vacuum valve are gradually released from the surfaces thereof, and the vacuum valve And gradually decreases due to slow leaks in which air gradually penetrates from the outside through a few defective holes in the constituent materials and joints. Among them, the one caused by outgassing is a curved change having a saturation value, while the one caused by a slow leak is a linear change corresponding to the size of the hole. Therefore, the change as a whole is shown as a total gas obtained by superimposing these. In order to manage the vacuum life of the vacuum valve, it is necessary to take an appropriate method for these deterioration factors.

FIG. 5 is a schematic sectional view showing a conventional vacuum valve provided with a sensor for directly detecting a decrease in the degree of vacuum.
The vacuum valve 1 includes a cylindrical insulating container 5, a fixed contact 2 supported by a metal end plate 4A connected to one end thereof, an end plate 4B and a metal bellow 6 connected to the other end of the insulating container. The movable contact 3 supported by the above is used as a main component, and the movable contact 3 is driven by an operating device (not shown), thereby forming a circuit breaker or a switch having a switching function of a load current or a charging current. A metal shield 7 is provided concentrically inside the insulating container 5 inside the vacuum valve 1, and metal vapor generated by an arc at the time of current interruption adheres to the inner wall of the insulating container 5, thereby deteriorating insulation performance. Is configured to prevent that. Reference numeral 10 denotes, for example, a magnetron element as a vacuum sensor, which is hermetically attached to the end plate 4A to detect the vacuum inside the vacuum valve. However, this method has a drawback that a new slow leak is generated at a hermetically coupled portion between the vacuum valve and the vacuum degree sensor, and has a drawback that the reliability of the vacuum valve is impaired. It is almost impossible to attach a vacuum sensor to an existing vacuum valve by post-processing.

FIG. 6 is a characteristic diagram showing the relationship between the internal pressure of the vacuum valve and the AC flashover voltage between the electrodes.
When the degree of vacuum in the vacuum valve is reduced (deteriorated) to the order of 10 ^-3 Torr, the flashover voltage starts to decrease, and the lower limit (10 ^-1 k) in the order of 10 ^-2 to 10 ^-1 Torr.
Shows the V order), flashover voltage is 10 ⁰ Torr order above recovered to gradually rise to flashover voltage at atmospheric pressure in air. In general, when the degree of vacuum is reduced to about 10 ^-2 Torr, the vacuum valve cannot withstand the normal ground voltage of the power system. Abnormal discharge occurs, and in the closed state, abnormal discharge occurs between the pair of contacts and the metal shield. Therefore, even in the prior art, there are some known vacuum degree decrease detection devices that detect the decrease in vacuum degree indirectly by electrically detecting abnormal discharge from outside the vacuum valve by focusing on the above-described characteristics. Have been.

FIG. 7 is a block diagram showing a first prior art. A vacuum valve 1 such as a circuit breaker or a switch provided between an AC power system 11 and a load system 12 has a load side. arrester 13, CR-type surge absorber 14 and the like are provided, and noticed that the discharge current I _S due to abnormal discharge between the poles flows, an arrester 13 or current sensor 15 to the ground line side of the surge absorber 14 provided, opening It is configured to detect a decrease in the degree of vacuum by detecting a discharge current generated at the time.

FIG. 8 is a block diagram showing a second prior art, in which high-frequency noise generated accompanying the abnormal discharge 100 between the electrodes of the vacuum valve 1 is transmitted to the power supply system side of the vacuum valve via a high-voltage capacitor 16. The high-frequency noise detector 17 is connected to the high-frequency noise detector 17. FIG. 9 is a block diagram showing a third conventional technique, in which the potential of the metal shield 7 which rises due to the abnormal discharge 101S generated between the metal shield 7 and the contactor at the time of opening and closing is determined. 5, a voltage dividing capacitor 18 is connected to the external terminal 7A of the metal shield drawn out through the high voltage capacitor 17,
The potential of the voltage dividing capacitor 18 is configured to be measured by the voltage detector 19.

FIG. 10 is a block diagram showing a fourth prior art, in which an abnormal discharge 101 which occurs similarly to the third prior art.
An increase in the potential of the metal shield 7 due to S is detected by a potential sensor 20 provided with a gap between the metal shield 7 and the outer surface of the insulating container 5.

[0009]

In the first prior art, an abnormal discharge can be detected by using a lightning arrester or a surge absorber. It is necessary to provide a discrimination circuit for discriminating the discharge current from the output side of the current sensor 15, and there is a problem that the detection circuit is complicated.

In the second prior art, it has been experimentally verified that the transition to arc discharge occurs immediately when an abnormal discharge occurs between the poles. There is a problem that the charge amount of noise is extremely small at several pC, and it is difficult to perform highly reliable detection. Further, it is necessary to provide a high-voltage capacitor 16 for high-frequency noise detection for each vacuum valve, and the device becomes large. is there.

Also, the third prior art requires a high-voltage capacitor 16 as in the second prior art, and an external terminal must be provided through the insulating container, which adversely affects the performance of maintaining the degree of vacuum. There is a danger. In the fourth prior art, since the coupling capacitance between the metal shield and the potential sensor is small, capacitance coupling is easily generated between the metal shield and the other phase vacuum valve or the like. There are drawbacks that are easy to commit.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus for detecting abnormal discharge caused by a decrease in the degree of vacuum of a vacuum valve with high accuracy without using a high-voltage capacitor. It is in.

[0013]

According to the present invention, a vacuum valve of a switchgear connected to a three-phase AC power system includes an insulating container and one end of the insulating container. A fixed contact supported by an end plate coupled to the end plate, and a movable contact supported by an end plate and a metal bellows coupled to the other end of the insulating container. A metal shield which is concentrically arranged while holding a vacuum gap between the contacts and detects a decrease in the degree of vacuum of the vacuum valve by abnormal discharge between the contacts and the metal shield. An external electrode buried in the vessel wall of the insulating container and insulated and supported so as to face the metal shield, and only external terminals thereof are disposed so as to be exposed outside the insulating container,
It is provided with a voltage dividing capacitor connected between the external electrode and the ground, and the abnormal discharge is detected by a terminal voltage of the voltage dividing capacitor.

In the above means, an external electrode and a voltage dividing capacitor conductively connected to the external electrode are provided at a position facing the metal shield on the outer peripheral side of the cylindrical insulating container of the vacuum valve, so that the relative dielectric constant is increased. Can be used as a high-voltage capacitor with the capacitance of an insulating container larger than that of a gas, and the potential rise of the metal shield due to abnormal discharge can be detected as a potential rise of the voltage dividing capacitor for each vacuum valve, so the degree of vacuum reduction can be accurately detected. In addition, detection can be performed for each phase. Further, by embedding the external electrode in the container wall of the insulating container and disposing only the external terminal outside the insulating container, a sufficient creepage insulation distance with respect to the pair of end plates can be secured. In addition, the reliability of the external insulation becomes higher.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments.
explain. 1 and 2 show a reference example of the present invention.
FIG. 3 is a cross-sectional view of a vacuum valve including a vacuum degree reduction detection device.
FIG. 1 shows the closed state, and FIG. 2 shows the opened state.
It is. In FIG. 1, the cylindrical shape of the vacuum valve 31 is shown.
A pair of contacts 2 and 3 is provided inside the insulating container 5 with a gap.
L_TwoA metal shield 7 for holding and surrounding the
A circle is formed on the outer peripheral surface of the edge container 5 so as to face the metal shield 7.
An external electrode 32 formed in a cylindrical shape is provided.
2 is grounded via a voltage dividing capacitor 33,
Terminal voltage V of the sensor 33_SIs detected by an electrometer not shown
Is done. The insulating container 5 is made of an insulating material having a relative dielectric constant of about 5 to 7.
, The metal shield 7 and the contacts 2 and 3
Capacitance C between ₁Is a metal shield and an external electrode 32
Capacitance C between_TwoAnd a partial pressure condenser
Capacitance C of the sensor 33_SIs C₁<C_Two≪C_SCondition
The size is set to a satisfactory size. Therefore, during steady operation
To the ground voltage V of the three-phase AC power system 11_gIs each phase vacuum
Each valve has a series capacitance C₁, C_Two, C_SReverse to
Since the capacitance is divided in proportion to the capacitance, a voltage dividing capacitor
33 terminal voltage V_SIs a very small voltage value. On the other hand vacuum
The degree of vacuum of lube 31 is 10^-2Down to Torr order
Then, between the pair of contacts 2 and 3 and the metal shield 7
Causes an abnormal discharge 101S, and the potential of the metal shield 7 is
It rises to the normal ground voltage Vg of the power supply system, and this potential V_gTo
Capacitance C_TwoAnd C_STo split the capacitance.
You. Therefore, the terminal voltage V of the voltage dividing capacitor 33_SIs above
The potential rise can be detected by an electrometer.
Can detect the occurrence of abnormal discharge and reduce the degree of vacuum.
Vacuum valve can be easily detected.

[0016] When the vacuum valve 31 is in open state shown in FIG. 2, although the contact 3 is substantially zero potential on the load side, abnormal discharge when the vacuum is lowered in comparison to the machining gap dimension L ₁ since having a discharge property of easily the metallic shield 7 side having a larger gap length L _2, it is possible to detect the same abnormal discharge as in the closed state. Since the charging current only flows through the external electrode 32, the external electrode 32 can be easily formed by applying a conductive coating or foil-like electrode with a predetermined width leaving a creeping insulation distance on the outer peripheral surface of the insulating container 5, In particular, by arranging the vacuum valve 31 in an SF ₆ gas atmosphere, it is possible to obtain a highly-reliable external-insulation degree-of-vacuum-drop detecting device.

FIG. 3 is a sectional view of a main part showing an embodiment of the present invention. A vacuum valve 41 has an embedded external electrode 42 embedded in an insulating container 35 for connecting a voltage dividing capacitor. Is different from the above-mentioned reference example in that only the external terminals 42A are exposed to the outside of the insulating container 35. Since a sufficient creepage insulation distance can be secured for the pair of end plates 4A and 4B, Thus, a vacuum valve having a more excellent insulation reliability and a device for detecting a decrease in vacuum degree can be obtained.

[0018]

As described above, according to the present invention, the external electrodes are provided on the insulating container of the vacuum valve, and the capacitance of the insulating container between the vacuum container and the metal shield is also used as a high-voltage capacitor. An advantage is obtained in which of the vacuum valves the degree of vacuum reduction has occurred can be easily detected in both open and closed states. In addition, by burying the external electrodes in the insulating container and disposing only the external terminals outside the insulating container, a vacuum valve type switchgear with higher reliability of external insulation and detection of a decrease in the degree of vacuum are provided. A device is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a reference example of the present invention in a closed state;

FIG. 2 is a cross-sectional view in an open state showing a reference example of the present invention.

FIG. 3 is a sectional view of a main part showing an embodiment of the present invention.

FIG. 4 is a principle explanatory view showing a secular change of the degree of vacuum of a vacuum valve.

FIG. 5 is a schematic sectional view showing a conventional vacuum valve provided with a vacuum sensor.

FIG. 6 is a diagram showing a vacuum degree of a vacuum valve versus a flashover characteristic between electrodes.

FIG. 7 is a configuration diagram showing a first conventional technique.

FIG. 8 is a configuration diagram showing a second conventional technique.

FIG. 9 is a configuration diagram showing a third conventional technique.

FIG. 10 is a configuration diagram showing a fourth conventional technique.

[Explanation of symbols]

1, 31, 41 ... vacuum valve, 2, 3 ... contact, 4A,
4B: end plate, 5, 35: insulating container, 7: metal shield,
DESCRIPTION OF SYMBOLS 10 ... Vacuum degree sensor, 11 ... Power supply system, 12 ... Load system, 16 ... High voltage condenser, 18, 33 ... Voltage division condenser, 32 ... External electrode, 42 ... Embedded external electrode, 100 ...
Abnormal discharge between poles, 100S ... Discharge abnormal to metal shield.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Shibata 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Nobuo Suzuki 1, Tanabe Nitta, Kawasaki-ku, Kawasaki, Kanagawa No. 1 Fuji Electric Co., Ltd.

Claims (1)

[Claims] 1. A vacuum valve of a switchgear connected to a three-phase AC power system, an insulating container, a fixed contact supported by an end plate coupled to one end of the insulating container, and the insulating container. A movable contact supported by a metal bellows and an end plate coupled to the other end of the end plate, and disposed concentrically inside the insulating container while maintaining a vacuum gap between the two contacts. A device having a metal shield and detecting a decrease in the degree of vacuum of the vacuum valve by abnormal discharge between the two contacts and the metal shield, wherein the metal shield is embedded in a wall of the insulating container and faces the metal shield. An external electrode that is insulated and supported and only its external terminals are exposed to the outside of the insulating container, and a voltage dividing capacitor connected between the external electrode and the ground is provided. Minute Vacuum reduction detecting apparatus for a vacuum valve type switchgear and detecting the terminal voltage of the capacitor.