JP2022124163A - vacuum valve - Google Patents

Abstract

To provide a vacuum valve capable of suppressing progress of surface discharge while alleviating electric field concentration (that is, while uniformizing electric field intensity (electric field distribution)).SOLUTION: A vacuum valve comprises: a dielectric insulation container 1 that accommodates a pair of electrodes E1 and E2 separable from and contactable with each other; and discharge progress suppression means that suppresses progress of surface discharge when surface discharge occurs along an outer surface S2 of the insulation container. The discharge progress suppression means sets a dielectric constant of a part of the insulation container (a low-dielectric constant region 1b) to a value different from that of the other part (a high-dielectric constant region 1a).SELECTED DRAWING: Figure 1

Description

Embodiments of the invention relate to vacuum valves.

2. Description of the Related Art A switchgear equipped with a switch such as a circuit breaker or a disconnecting switch is known as a switchgear for receiving and distributing power provided in a building or a large facility. A vacuum valve is applied to the switchgear as a component of the switchgear. The inside of the vacuum valve is maintained in a constant insulating state by an insulating container (vacuum container), and a pair of electrodes are detachably accommodated inside this insulating container. In this case, by connecting and disconnecting the pair of electrodes, the fault current is interrupted and the load current is opened and closed, and electric power is stably supplied from the switchgear.

Japanese Patent No. 6161354 Japanese Patent No. 6122577

By the way, as a use of the vacuum valve, it is assumed that the outside of the vacuum valve is exposed to the atmosphere. In this state, since the air that constitutes the atmosphere has low insulation performance, the discharge progresses along the outer surface of the insulating container that is directly exposed to the atmosphere (for example, the outer peripheral surface of a cylindrical insulating container). Form, that is, creeping discharge (creeping corona discharge) is likely to occur.

Here, when creeping discharge occurs, an "electron avalanche" may occur along the outer surface of the insulating container. "Electron avalanche" is an electric field formed on the outer surface of an insulating container. When free electrons collide with gas molecules, new electrons are ejected, which are accelerated by the electric field and collide with other gas molecules. , refers to the phenomenon in which the number of electrons increases at an accelerating rate.

When such an "electron avalanche" occurs, creeping discharge progresses and dielectric breakdown further progresses. In order to suppress the development of creeping discharge, it is effective to improve the insulation performance of the outside of the vacuum valve. As a method for improving the insulation performance of the outside of the vacuum valve, conventionally, there is a method of providing a pleated molded body on the outer surface of the insulating container to extend the creepage distance on the outer surface of the insulating container, or a method of forming a high dielectric constant insulating layer on the outer surface of the insulating container. is provided to relax the electric field at the sealed portion of the insulating container (for example, the opening of the insulating container having a triple junction).

However, along with the miniaturization of the vacuum valve, it has become difficult to extend the creepage distance. There is also a problem that the provision of the high-dielectric-constant insulating layer conversely promotes creeping discharge. For this reason, there is a limit to improvement in insulation performance outside the vacuum valve.

Therefore, in order to solve such a problem, the electric field concentration is alleviated over the entire insulating container (that is, the electric field strength (electric field distribution) is made uniform), and at the same time, the creeping discharge progresses on the outer surface of the insulating container. There is a demand for a vacuum valve to which a suppressing technique is applied.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vacuum valve capable of alleviating electric field concentration (that is, making the electric field strength (electric field distribution) uniform) and at the same time suppressing the progress of creeping discharge.

According to the embodiment, when a creeping discharge occurs along the outer surface of the insulating container containing a pair of separable electrodes and having a dielectric property, the discharge progress suppression suppresses the progress of the creeping discharge. and the discharge progression suppressing means sets a part of the insulating container to a dielectric constant different from that of the other part.

Sectional drawing which shows the internal structure of the vacuum valve which concerns on one Embodiment. FIG. 2 is a schematic diagram showing a dielectric constant distribution in the insulating container of FIG. 1; (a) is a schematic diagram showing the equipotential distribution of the existing insulating container, and (b) is a schematic diagram showing the equipotential distribution of the insulating container of FIG. FIG. 4 is a schematic diagram showing a dielectric constant distribution in an insulating container according to another embodiment; FIG. 4 is a schematic diagram showing a dielectric constant distribution in an insulating container according to another embodiment;

"one embodiment"
FIG. 1 is an arrangement configuration diagram of a vacuum valve P according to this embodiment. In this embodiment, as the application of the vacuum valve P, it is assumed that the outside of the vacuum valve P (for example, the outer surface (peripheral surface) S2 of the cylindrical insulating container 1 described later) is exposed to the atmosphere (air). is doing.

In the example of FIG. 1, the vacuum valve P includes a fixed electrode E1, a movable electrode E2, an insulating container 1 (also referred to as a vacuum container), a fixed side sealing member 2, a movable side sealing member 3, and an airtight maintenance electrode. It has a mechanism 4 and an arc shield 5 .

As shown in FIG. 1, the fixed electrode E1, the movable electrode E2, the airtight maintenance mechanism 4, and the arc shield 5 are accommodated in the insulating container 1. As shown in FIG. The insulating container 1 is made of a material having insulating properties as described later. The fixed-side sealing member 2 and the movable-side sealing member 3 are made of, for example, a metal material whose main component is stainless steel.

The insulating container 1 has a cylindrical shape centered on an imaginary axis Px defining the center of the vacuum valve P. As shown in FIG. The cylindrical insulating container 1 is open at both ends when viewed in the direction of the imaginary axis Px. Both openings (the fixed side opening K1 and the movable side opening K2) are covered with the fixed side sealing member 2 and the movable side sealing member 3 . Specifically, the fixed-side sealing member 2 closes one fixed-side opening K<b>1 of the insulating container 1 via the fixed-side sealing fitting 6 . The movable-side sealing member 3 closes the other movable-side opening K2 of the insulating container 1 via the movable-side sealing fitting 7 .

The arc shield 5 is made of, for example, a metallic material containing copper, stainless steel, or the like as a main component. The arc shield 5 has a hollow cylindrical shape and is fixed to the inner surface S<b>1 of the insulating container 1 . The arc shield 5 is arranged inside (inside) so as to accommodate a fixed contact 8 of the fixed electrode E1 and a movable contact 10 of the movable electrode E2, which will be described later.

The fixed electrode E1 and the movable electrode E2 are aligned and extended along the imaginary axis Px. The fixed electrode E<b>1 includes a fixed contact 8 and a fixed conducting shaft 9 . The movable electrode E<b>2 includes a movable contact 10 and a movable current-carrying shaft 11 .

The fixed contact 8 and the movable contact 10 are arranged facing each other. The fixed contact 8 is connected to one end of a fixed current-carrying shaft 9, and the other end of the fixed current-carrying shaft 9 is immovably fixed to the vacuum valve P via the fixed-side sealing member 2 along the virtual axis Px. there is The movable contact 10 is connected to one end of a movable current-carrying shaft 11 , and the other end of the movable current-carrying shaft 11 is connected to an operation mechanism (not shown) via a movable-side sealing member 3 .

Here, the movable current-carrying shaft 11 is moved along the imaginary axis Px by the operating mechanism. Thereby, the movable contact 10 can be separated from and contacted with the fixed contact 8 . As a result, the vacuum valve P can be opened and closed (that is, the pair of electrodes E1 and E2 can be opened and closed).

Further, an airtightness maintaining mechanism 4 is arranged between the movable current-carrying shaft 11 and the movable-side sealing member 3 . The airtightness maintaining mechanism 4 is made of elastic bellows, and the bellows (airtightness keeping mechanism) 4 is made of thin metal such as stainless steel. The bellows 4 has a bellows shape that can be expanded and contracted in the direction of the virtual axis Px, and covers the outside of the movable current-carrying shaft 11 without gaps.

One end of the bellows 4 is joined to the movable side sealing member 3 with no gap, and the other end is joined to the movable current-carrying shaft 11 without any gap. Thereby, the inside of the insulating container 1 is always maintained in an airtight state (that is, in a vacuum state). As a result, when the vacuum valve P is opened and closed, the atmosphere (air) does not enter the insulating container 1 even while the movable current-carrying shaft 11 is being moved along the imaginary axis Px.

By the way, in the insulating container 1 directly exposed to the atmosphere (air), there is a case where a form of discharge (that is, creeping discharge) occurs in which dielectric breakdown progresses along the outer surface S2. During creeping discharge, an “electron avalanche” is generated along the outer surface S2 of the insulating container 1 . In this case, creeping discharge develops in the existing insulating container 1 made of an insulating material having a high dielectric constant, such as alumina ceramics.

Therefore, the vacuum valve P according to the present embodiment has discharge progress suppression means for suppressing the progress of the creeping discharge when the creeping discharge occurs along the outer surface S2 of the insulating container 1 . The discharge progress suppressing means sets a part of the insulating container 1 to a dielectric constant different from that of the other part. Specifically, the discharge progression suppressing means provides a height difference between the dielectric constant of a part of the insulating container 1 and the dielectric constant of the other part.

As an example of a method of providing a difference in dielectric constant, an insulating material with a low dielectric constant (hereinafter referred to as a low dielectric constant material) is applied to a part of the insulating container 1, and the other part of the insulating container 1 is made of , an insulating material with a high dielectric constant (hereinafter referred to as a high dielectric constant material) is applied. A portion of the insulating container 1 to which the low-dielectric-constant material is applied reduces the amount of electrostatic energy stored there and improves the insulation performance, so that the effect of suppressing the progress of creeping discharge can be enhanced. Note that the low dielectric constant material and the high dielectric constant material are set according to, for example, the purpose of use and the environment of use of the vacuum valve P (insulating container 1), and are not particularly limited here.

Furthermore, assuming a direction from the fixed-side opening K1 to the movable-side opening K2 (or from the movable-side opening K2 to the fixed-side opening K1) as an example of the progress direction of creeping discharge, the discharge progress suppressing means It is provided continuously in a direction transverse to the direction in which creeping discharge develops along the outer surface S2 (that is, in the circumferential direction in the case of a cylindrical insulating container). As a result, the “electron avalanche” that develops along the outer surface S<b>2 of the insulating container 1 can be dammed up and suppressed.

In the example of FIG. 1, a low dielectric constant region 1b is provided in a portion (ie, center) of the insulating container 1, and a high dielectric constant region 1a is provided in other portions (ie, both sides of the center) of the insulating container 1. ing. The high dielectric constant region 1a and the low dielectric constant region 1b are formed concentrically around the virtual axis line Px.

The low dielectric constant region 1b has a hollow cylindrical shape that accommodates the entire arc shield 5 therein. The high dielectric constant region 1a is provided adjacent to both sides of the low dielectric constant region 1b. The high dielectric constant region 1a on one side has a hollow cylindrical shape extending from one end of the low dielectric constant region 1b to the fixed side opening K1. The high dielectric constant region 1a on the other side has a hollow cylindrical shape extending from the other end (opposite side of the one end) of the low dielectric constant region 1b to the movable side opening K2.

Here, as a method of manufacturing the insulating container 1, for example, a method of integrally molding the entire insulating container 1 by combining a low dielectric constant material and a high dielectric constant material, or a method of combining a low dielectric constant material and a high dielectric constant material into an insulating container. 1, or a method of providing on both the inner surface S1 and the outer surface S2 (hereinafter referred to as both surfaces S1 and S2).

First, in the method of integrally molding the entire insulating container 1 by combining a low dielectric constant material and a high dielectric constant material, for example, powdery low dielectric constant material and high dielectric constant material are prepared, and the center of the insulating container 1 is While arranging the low dielectric constant material on the part to be the center and arranging the high dielectric constant material on both sides of the central part, these are laminated to a predetermined thickness and fired. Thereby, the insulating container 1 in which the high dielectric constant regions 1a are adjacent to both sides of the low dielectric constant region 1b can be integrally molded.

Next, in the method of providing the low-dielectric-constant material and the high-dielectric-constant material on the inner surface S1 or the outer surface S2 of the insulating container 1, or on both surfaces S1 and S2, for example, an existing insulating container 1 integrally molded with a predetermined insulating material is prepared. Then, the central inner surface S1 or outer surface S2 or both surfaces S1 and S2 of the insulating container 1 are coated (applied) with a low dielectric constant material, and the central inner surface S1 or outer surface S2 or both surfaces S1 of the insulating container 1 are coated (applied). , S2 are coated (applied) with a high-low dielectric constant material. As a result, the existing insulating container 1 can be used as it is, and a new insulating container 1 in which the high dielectric constant regions 1a are adjacent to both sides of the low dielectric constant region 1b can be realized.

FIG. 2 is a dielectric constant distribution diagram of the insulating container 1 manufactured by the manufacturing method described above. As shown in FIG. 2, the dielectric constant of the insulating container 1 is lowest in the central low dielectric constant region 1b and highest in the high dielectric constant regions 1a on both sides of the center. As a result, the low dielectric constant region 1b, which has higher insulation performance than other portions, is formed in the center of the insulating container 1 in the circumferential direction crossing the progress direction of the creeping discharge that develops along the outer surface S2 of the insulating container 1. It can be seen that they are set continuously.

FIG. 3(a) is an equipotential distribution map of an existing insulating container (not shown), and FIG. 3(b) is an equipotential distribution map of the insulating container 1 of this embodiment. Comparing the two, the equipotential distribution of the existing insulating container (FIG. 3(a)) is dense at both ends (the fixed side opening K1 and the movable side opening K2). It can be seen that the equipotential distribution of the insulating container 1 (FIG. 3(b)) is sparse at both ends (the fixed side opening K1 and the movable side opening K2). That is, the equipotential distribution (FIG. 3(b)) of the present embodiment is substantially uniform over the entire insulating container 1, thereby relaxing the electric field concentration over the entire insulating container 1. I understand.

As described above, according to the present embodiment, the insulating container 1 is partially provided with the low dielectric constant region 1b, and the other portion of the insulating container 1 is provided with the high dielectric constant region 1a. In this case, the low dielectric constant region 1b is provided continuously in a direction transverse to the progress direction of the creeping discharge that develops along the outer surface S2 of the insulating container 1. As shown in FIG. In the low dielectric constant region 1b, the amount of electrostatic energy stored there is reduced, the insulation performance is improved, and the effect of suppressing the progress of creeping discharge is enhanced. As a result, the "electron avalanche" that develops along the outer surface S2 of the insulating container 1 can be suppressed so as to be blocked by the low dielectric constant region 1b. As a result, the electric field concentration can be alleviated (that is, the electric field strength (electric field distribution) can be made uniform) over the entire insulating container 1, and at the same time, the creeping discharge on the outer surface S2 of the insulating container 1 can be suppressed.

Furthermore, according to the present embodiment, unlike the prior art, it is not necessary to extend the creepage distance on the outer surface S2 of the insulating container 1. Therefore, the insulating container 1 (that is, the vacuum valve P) can be downsized and at the same time development of creeping discharge on the outer surface S2 of the can be suppressed.

"other embodiments"
In the above-described embodiment, it is assumed that the insulating container 1 is provided with the low dielectric constant region 1b in one portion (ie, the center) and provided with the high dielectric constant region 1a in the other portion (ie, both sides of the center). Alternatively, although not shown, the high dielectric constant region 1a may be provided in the center and the low dielectric constant regions 1b may be provided on both sides thereof.

In the above-described embodiment, it is assumed that a part of the insulating container 1 (that is, one central part) is set to have a dielectric constant different from that of the other parts. may be set to a dielectric constant different from that of other portions. For example, low dielectric constant regions 1b are provided at the center and both ends of the insulating container 1, and high dielectric constant regions 1a are interposed between the low dielectric constant regions 1b. Alternatively, high dielectric constant regions 1a are provided at the center and both ends of the insulating container 1, and low dielectric constant regions 1b are interposed between the high dielectric constant regions 1a.

In the above-described embodiment, it is assumed that the dielectric constant of a portion (ie, the center) of the insulating container 1 and the dielectric constant of the other portions (ie, both sides of the center) are provided with a single stepped height difference. However, instead of this, for example, as shown in FIG. A height difference may be given step by step. Thereby, the equipotential distribution of the insulating container 1 can be made more uniform. As a result, the electric field concentration can be more relaxed (that is, the electric field strength (electric field distribution) can be made more uniform) over the entire insulating container 1 .

In the above-described embodiment, it is assumed that the dielectric constant of a portion (ie, the center) of the insulating container 1 and the dielectric constant of the other portions (ie, both sides of the center) are provided with a stepwise height difference. Alternatively, however, as shown for example in FIG. 5, there is a continuous may be given a height difference. As a result, the electric field concentration can be more relaxed (that is, the electric field strength (electric field distribution) can be made more uniform) over the entire insulating container 1 .

"Variation"
The insulating container 1 of the vacuum valve P according to this modification is coated with a surface resistance control material, a low secondary electron emission coefficient material, and a nonlinear resistance material over a predetermined portion including its inner surface S1, outer surface S2, or both surfaces S1 and S2. , a nonlinear dielectric material. Each material will be described individually below.

<Surface resistance control material>
In the vacuum valve P according to the above-described embodiment, the insulation performance of the insulating container 1 in which a part thereof is set to have a dielectric constant different from that of the other part may greatly change depending on the surface resistance of the inner surface S1 and the outer surface S2. . For example, when free electrons collide with the surface of the insulating container 1, secondary electrons are emitted from the surface of the insulating container 1, so that the surfaces (the inner surface S1 and the outer surface S2) of the insulating container 1 are easily charged. , it becomes difficult to keep the insulation performance constant. In this case, the surface resistance control material is applied all over the inner surface S1 or the outer surface S2 of the insulating container 1 or both surfaces S1 and S2. As a result, it is possible to ensure the same effect as the above-described embodiment while suppressing the occurrence of electrification on the surface of the insulating container 1 . As the surface resistance control material, for example, chromium oxide, silicon carbide, titanium nitride, vanadium, etc. can be applied.

<Low secondary electron emission coefficient material>
The low secondary electron emission coefficient material has the function of suppressing emission of secondary electrons from the surface of the insulating container 1 as well as the function of the surface resistance control material described above. In this case, a low secondary electron emission coefficient material is applied over the entire inner surface S1, outer surface S2, or both surfaces S1 and S2 of the insulating container 1 instead of the surface resistance control material. As a result, it is possible to secure the same effects as those of the above-described embodiment while suppressing the generation of electrification on the surface of the insulating container 1 and the emission of secondary electrons. As materials with a low secondary electron emission coefficient, for example, vanadium, chromium, carbon, iron, silicon carbide, copper, molybdenum, and titanium nitride can be applied. Since it is often very small, it is necessary to prevent a sudden drop in surface resistance by thin film processing or the like.

<Nonlinear resistance material>
Instead of the surface resistance control material and the low secondary electron emission coefficient material described above, a nonlinear resistance material may be applied over the inner surface S1, the outer surface S2, or both surfaces S1 and S2 of the insulating container 1. FIG. The non-linear resistance material has a characteristic that the resistance value becomes small in the high dielectric constant region 1a and the resistance value becomes large in the low dielectric constant region 1b. As a result, nonlinear resistance characteristics are developed along the surfaces (inner surface S1, outer surface S2) of the insulating container 1 having a dielectric constant distribution in the direction of the virtual axis Px when a voltage is applied. , K2) can be relaxed. As the nonlinear resistance material, for example, zinc oxide, silicon carbide, carbon, triiron tetroxide, etc. can be applied. Here, when the nonlinear resistance material is applied to the inner surface S1 of the insulating container 1 in a vacuum environment, it is not preferable to use an organic material such as an epoxy resin as a binder for the nonlinear resistance material. It is preferred to use a system binder.

<Nonlinear dielectric material>
Instead of the nonlinear resistance material described above, a nonlinear dielectric material may be added (mixed) over a predetermined portion of the insulating container 1 . The nonlinear dielectric material has a characteristic that the dielectric constant in the high dielectric constant region 1a is high and the dielectric constant in the low dielectric constant region 1b is low. In this case, in the method of manufacturing the insulating container 1 according to the embodiment described above, the nonlinear dielectric material is added (mixed) to the low dielectric constant material and the high dielectric constant material. As a result, the responsiveness to relatively high frequencies such as commercial frequencies and lightning impulse voltages can be improved. As a result, even in the event of a high voltage or high frequency surge such as a lightning surge in particular, the electric field concentration is alleviated (that is, the electric field strength (electric field distribution) is made uniform) over the entire insulating container 1, and at the same time, It is possible to suppress the development of creeping discharge on the outer surface S2. Inorganic particles such as titanium dioxide, silicon dioxide, potassium titanate, and barium titanate can be used as the nonlinear dielectric material. Here, since the high dielectric constant region 1a to which the non-linear dielectric material is added (mixed) may become a state in which discharge progresses easily, in order to avoid this, a region where the creeping discharge does not contact, for example, the inner surface S1 of the insulating container 1 It is preferred to add (mix) the nonlinear dielectric material only on the side.

Although one embodiment and several modifications of the present invention have been described above, these embodiments and modifications are presented as examples and are not intended to limit the scope of the invention. These embodiments and modifications can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1... Insulating container (vacuum container), 1a... High dielectric constant area, 1b... Low dielectric constant area, 2... Fixed side sealing member, 3... Movable side sealing member, 4... Airtight maintenance mechanism, 5... Arc shield, 6 Fixed-side sealing fitting 7 Movable-side sealing fitting 8 Fixed contact 9 Fixed current-carrying shaft 10 Movable contact 11 Movable current-carrying shaft P Vacuum valve Px Virtual axis E1 Fixed electrode, E2... Movable electrode, K1... Fixed side opening, K2... Movable side opening, S1... Inner surface, S2... Outer surface.

Claims (9)

an insulating container containing a pair of separable electrodes and having dielectric properties;
discharge progress suppression means for suppressing the progress of the creeping discharge when the creeping discharge occurs along the outer surface of the insulating container,
The discharge progression suppressing means is a vacuum valve that sets a part of the insulating container to a dielectric constant different from that of the other part. 2. The vacuum valve according to claim 1, wherein said discharge progress suppressing means provides a height difference between a dielectric constant of a part of said insulating container and a dielectric constant of another part. 3. The vacuum valve according to claim 2, wherein said discharge progress suppressing means provides a stepwise or continuous height difference between a dielectric constant of a part of said insulating container and a dielectric constant of another part. 2. The vacuum valve according to claim 1, wherein said discharge progress suppressing means is provided continuously in a direction transverse to the progress direction of said surface discharge progressing along the outer surface of said insulating container. 2. The vacuum valve according to claim 1, wherein said discharge progress suppressing means is provided on the outer surface or the inner surface of said insulating container, or on both the outer surface and the inner surface of said insulating container. 2. The vacuum valve according to claim 1, wherein the insulating container is set in a state of use in which the outer surface thereof is exposed to the atmosphere. The discharge progress suppressing means is provided in a part and another part of the insulating container and is composed of a plurality of insulating materials having different dielectric constants,
The insulating container is integrally molded with a plurality of the insulating materials,
2. The vacuum valve according to claim 1, wherein said insulating material integrally molded on a part of said insulating container and said insulating material integrally molded on another part are set to have different dielectric constants. The discharge progress suppressing means is provided in a part and another part of the insulating container and is composed of a plurality of insulating materials having different dielectric constants,
The outer surface or the inner surface of a part of the insulating container and the other part, or both the outer surface and the inner surface of the part of the insulating container and the other part are coated with the insulating material different from each other,
6. The vacuum valve according to claim 5, wherein the insulating material covering a portion of the insulating container and the insulating material covering the other portion are set to have different dielectric constants. The insulating container of the vacuum valve according to claim 7 or claim 8 is coated with a surface resistance control material, a low secondary electron emission coefficient material, or a nonlinear resistance material over a predetermined portion including its outer surface, inner surface, or both surfaces. , a vacuum valve constructed with the addition of one of the nonlinear dielectric materials.

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