JP7566658B2 - Vacuum valve - Google Patents

Description

An embodiment of the present invention relates to a vacuum valve.

Switchgear equipped with switches such as circuit breakers and disconnectors is known as a switching device for receiving and distributing electricity installed in buildings and large facilities. A vacuum valve is used 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 housed inside this insulating container so that they can be connected and disconnected. In this case, fault currents are interrupted and load currents are opened and closed by connecting and disconnecting the pair of electrodes, and power is supplied stably from the switchgear.

Patent No. 6161354 Patent No. 6122577

In one application, the vacuum valve is expected to be used in a state where the outside of the vacuum valve is exposed to the atmosphere. In this state, the air that makes up the atmosphere has low insulating properties, so a discharge form in which insulation breakdown progresses along the outer surface of the insulating container that is directly exposed to the atmosphere (for example, the outer circumferential surface of a cylindrical insulating container), 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. An "electron avalanche" refers to the phenomenon in which, in the electric field formed on the outer surface of the insulating container, when free electrons collide with gas molecules, new electrons are knocked out, and these electrons are accelerated by the electric field and collide with other gas molecules, causing the number of electrons to increase at an accelerating rate.

When such an "electron avalanche" occurs, creeping discharge progresses, causing further breakdown. Improving the insulation performance of the outside of the vacuum valve is an effective way to suppress the progression of creeping discharge. Conventional methods for improving the insulation performance of the outside of the vacuum valve include providing a pleated body on the outer surface of the insulating container to extend the creeping distance on the outer surface of the insulating container, and providing a high dielectric constant insulating layer on the outer surface of the insulating container to reduce the electric field at the sealed portion of the insulating container (for example, the opening of an insulating container having a triple junction portion).

However, as vacuum valves become smaller, it is becoming more difficult to increase the creepage distance, and there are issues such as the inability to achieve sufficient electric field relaxation when creepage discharge occurs in areas other than the sealed portion, and the provision of a high-permittivity insulating layer actually causes creepage discharge to progress. For these reasons, there are limitations to how much insulation performance can be improved outside the vacuum valve.

Therefore, to solve these problems, there is a demand for a vacuum valve that uses technology that can reduce electric field concentration (i.e., make the electric field strength (electric field distribution) uniform) throughout the entire insulating container while at the same time suppressing the progress of creeping discharge on the outer surface of the insulating container.

The object of the present invention is to provide a vacuum valve that can reduce electric field concentration (i.e., make the electric field strength (electric field distribution) uniform) while at the same time suppressing the progression of creeping discharge.

According to an embodiment, the insulating container includes a dielectric container that houses a pair of detachable electrodes and an arc shield, and a discharge progression suppression means that suppresses the progression of a creeping discharge when a creeping discharge occurs along the outer surface of the insulating container, and the discharge progression suppression means sets a part of the insulating container to a dielectric constant different from that of the other part , and the part of the insulating container is disposed adjacent to the other part and is shaped to house the entire arc shield .

FIG. 2 is a cross-sectional view showing the internal configuration of a vacuum valve according to one embodiment. FIG. 2 is a schematic diagram showing the dielectric constant distribution in the insulating container of FIG. 1 . 2A is a schematic diagram showing an equipotential distribution in an existing insulating container, and FIG. 2B is a schematic diagram showing an equipotential distribution in the insulating container of FIG. 1 . FIG. 13 is a schematic diagram showing the dielectric constant distribution in an insulating container according to another embodiment. FIG. 13 is a schematic diagram showing the dielectric constant distribution in an insulating container according to another embodiment.

"One embodiment"
1 is a diagram showing the layout of a vacuum valve P according to this embodiment. In this embodiment, the vacuum valve P is intended to be used in a state where the outside of the vacuum valve P (for example, the outer surface (outer peripheral surface) S2 of a cylindrical insulating container 1 described later) is exposed to the atmosphere (air).

In the example of FIG. 1, the vacuum valve P has a fixed electrode E1, a movable electrode E2, an insulating container 1 (also called a vacuum container), a fixed sealing member 2, a movable sealing member 3, an airtightness maintaining mechanism 4, and an arc shield 5.

As shown in FIG. 1, the fixed electrode E1, the movable electrode E2, the airtightness maintaining mechanism 4, and the arc shield 5 are housed in an insulating container 1. The insulating container 1 is made of an insulating material as described below. The fixed side sealing member 2 and the movable side sealing member 3 are made of a metal material whose main component is, for example, stainless steel.

The insulating container 1 has a cylindrical shape centered on an imaginary axis Px that defines the center of the vacuum valve P. When viewed in the direction of the imaginary axis Px, the cylindrical insulating container 1 is open at both ends. Both openings (fixed side opening K1, movable side opening K2) are covered by a fixed side sealing member 2 and a movable side sealing member 3. Specifically, the fixed side sealing member 2 closes one of the fixed side openings K1 of the insulating container 1 via a fixed side sealing metal fitting 6. The movable side sealing member 3 closes the other movable side opening K2 of the insulating container 1 via a movable side sealing metal fitting 7.

The arc shield 5 is made of a metal material whose main components are, for example, copper or stainless steel. The arc shield 5 has a hollow cylindrical shape and is fixed to the inner surface S1 of the insulating container 1. The arc shield 5 is arranged so as to accommodate within its interior (inside) the fixed contact 8 of the fixed electrode E1, which will be described later, and the movable contact 10 of the movable electrode E2.

The fixed electrode E1 and the movable electrode E2 are aligned and extend along the imaginary axis Px. The fixed electrode E1 has a fixed contact 8 and a fixed current-carrying shaft 9. The movable electrode E2 has a movable contact 10 and a movable current-carrying shaft 11.

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

The movable current-carrying shaft 11 is then moved along the imaginary axis Px by the operating mechanism. This allows the movable contact 10 to be brought into contact with and separated from the fixed contact 8. As a result, the vacuum valve P can be opened and closed (i.e., the pair of electrodes E1, E2 can be brought into contact and separated from each other).

Furthermore, an airtightness maintaining mechanism 4 is disposed between the movable current-carrying shaft 11 and the movable-side sealing member 3. The airtightness maintaining mechanism 4 is made of a bellows having elasticity, and the bellows (airtightness maintaining mechanism) 4 is made of a thin metal such as stainless steel. The bellows 4 is shaped like a bellows that can expand and contract in the direction of the imaginary axis Px, and covers the outside of the movable current-carrying shaft 11 without any gaps.

One end of the bellows 4 is tightly joined to the movable sealing member 3, and the other end is tightly joined to the movable current-carrying shaft 11. This ensures that the inside of the insulating container 1 is always kept airtight (i.e., vacuum state). As a result, when opening and closing the vacuum valve P, the atmosphere (air) does not enter the inside of the insulating container 1, even while the movable current-carrying shaft 11 is being moved along the imaginary axis Px.

However, when an insulating container 1 is directly exposed to the atmosphere (air), a discharge pattern (i.e., creeping discharge) may occur in which dielectric breakdown progresses along the outer surface S2 of the insulating container. During creeping discharge, an "electron avalanche" occurs along the outer surface S2 of the insulating container 1. In this case, creeping discharge progresses in an existing insulating container 1 made of an insulating material with a high dielectric constant, such as alumina ceramics.

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

As an example of a method for 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 portion of the insulating container 1, and an insulating material with a high dielectric constant (hereinafter referred to as a high dielectric constant material) is applied to the other portion of the insulating container 1. The portion of the insulating container 1 to which the low dielectric constant material is applied has a smaller amount of electrostatic energy stored therein, improving the insulating performance, thereby enhancing the effect of suppressing the progress of creeping discharge. Note that the low dielectric constant material and the high dielectric constant material are set according to, for example, the purpose and environment of use of the vacuum valve P (insulating container 1), so there are no particular limitations 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 progression direction of the creeping discharge, the discharge progression suppression means is continuously provided in a direction transverse to the progression direction of the creeping discharge progressing along the outer surface S2 of the insulating container 1 (i.e., in the circumferential direction in the case of a cylindrical insulating container). This makes it possible to suppress the "electron avalanche" progressing along the outer surface S2 of the insulating container 1 as if it were a dam.

In the example shown in FIG. 1, a low dielectric constant region 1b is provided in a portion of the insulating container 1 (i.e., the center), and a high dielectric constant region 1a is provided in another portion of the insulating container 1 (i.e., both sides of the center). The high dielectric constant region 1a and the low dielectric constant region 1b are configured in a concentric shape with the virtual axis Px described above as the center.

The low dielectric constant region 1b has a hollow cylindrical shape that accommodates the entire arc shield 5 therein. The high dielectric constant regions 1a are 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 that extends 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 that extends from the other end (opposite the one end) of the low dielectric constant region 1b to the movable side opening K2.

The insulating container 1 can be manufactured, for example, by combining a low-permittivity material and a high-permittivity material to integrally mold the entire insulating container 1, or by providing a low-permittivity material and a high-permittivity material on the inner surface S1 or outer surface S2 of the insulating container 1, or on both the inner surface S1 and the outer surface S2 (hereinafter referred to as both surfaces S1 and S2).

First, in a method of integrally forming the entire insulating container 1 by combining low- and high-dielectric constant materials, for example, powdered low- and high-dielectric constant materials are prepared, and the low-dielectric constant material is placed in the center of the insulating container 1, while the high-dielectric constant material is placed on both sides of the center, and these are stacked to a predetermined thickness and sintered. This makes it possible to integrally form an insulating container 1 with high-dielectric constant regions 1a adjacent to both sides of a low-dielectric constant region 1b.

Next, in a method of providing a low dielectric constant material and a high dielectric constant material on the inner surface S1 or outer surface S2 or both surfaces S1 and S2 of an insulating container 1, for example, an existing insulating container 1 integrally molded with a specified insulating material is prepared, and the inner surface S1 or outer surface S2 or both surfaces S1 and S2 in the center of the insulating container 1 is coated (applied) with a low dielectric constant material, and the inner surface S1 or outer surface S2 or both surfaces S1 and S2 on both sides of the center of the insulating container 1 are coated (applied) with high and low dielectric constant materials. This makes it possible to realize a new insulating container 1 in which high dielectric constant regions 1a are adjacent to both sides of a low dielectric constant region 1b by using the existing insulating container 1 as is.

Figure 2 is a diagram showing the dielectric constant distribution of the insulating container 1 manufactured by the above-mentioned manufacturing method. As shown in Figure 2, the dielectric constant of the insulating container 1 is lowest in the low dielectric constant region 1b in the center, and highest in the high dielectric constant regions 1a on both sides of the center. This shows that the low dielectric constant regions 1b, which have higher insulating performance than other parts, are continuously provided in the center of the insulating container 1 in the circumferential direction transverse to the direction of progress of the creeping discharge that progresses along the outer surface S2 of the insulating container 1.

Figure 3(a) is an equipotential distribution diagram of an existing insulating container (not shown), and Figure 3(b) is an equipotential distribution diagram of the insulating container 1 of this embodiment. Comparing the two, it can be seen that the equipotential distribution of the existing insulating container (Figure 3(a)) is dense at both ends (fixed side opening K1, movable side opening K2), whereas the equipotential distribution of the insulating container 1 of this embodiment (Figure 3(b)) is sparse at both ends (fixed side opening K1, movable side opening K2). In other words, it can be seen that the equipotential distribution of this embodiment (Figure 3(b)) is almost uniform over the entire insulating container 1, and thus electric field concentration is alleviated over the entire insulating container 1.

As described above, according to this embodiment, a low dielectric constant region 1b is provided in a part of the insulating container 1, and a high dielectric constant region 1a is provided in the other part of the insulating container 1. In this case, the low dielectric constant region 1b is provided continuously in a direction transverse to the direction of progress of the creeping discharge progressing along the outer surface S2 of the insulating container 1. In the low dielectric constant region 1b, the amount of electrostatic energy stored therein is reduced, improving the insulating performance and enhancing the effect of suppressing the progress of the creeping discharge. As a result, the "electron avalanche" progressing along the outer surface S2 of the insulating container 1 can be suppressed as if it were dammed up by the low dielectric constant region 1b. As a result, the electric field concentration can be alleviated (i.e., the electric field strength (electric field distribution) is made uniform) over the entire insulating container 1, while at the same time suppressing the progress of the creeping discharge on the outer surface S2 of the insulating container 1.

Furthermore, according to this embodiment, there is no need to extend the creepage distance on the outer surface S2 of the insulating container 1 as in the conventional case, so it is possible to miniaturize the insulating container 1 (i.e., the vacuum valve P) while at the same time suppressing the progress of creepage discharge on the outer surface S2 of the insulating container 1.

Other Embodiments
In the above-described embodiment, it is assumed that the low dielectric constant region 1b is provided in a part of the insulating container 1 (i.e., the center) and the high dielectric constant region 1a is provided in the other part (i.e., both sides of the center). However, instead of this, although not specifically 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 of the high dielectric constant region 1a.

In the above embodiment, it is assumed that a portion of the insulating container 1 (i.e., one location in the center) is set to a dielectric constant different from that of the other portions. Alternatively, although not specifically shown, multiple locations may be set to a dielectric constant different from that of the other portions. For example, low dielectric constant regions 1b are provided in three locations 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 in three locations 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 embodiment, it is assumed that there is a single step difference in the dielectric constant between a portion (i.e., the center) of the insulating container 1 and the other portions (i.e., both sides of the center). However, instead, as shown in FIG. 4, there may be multiple steps in the dielectric constant between a portion (i.e., the center) of the insulating container 1 and the other portions (i.e., both sides of the center). This makes it possible to make the equipotential distribution of the insulating container 1 more uniform. As a result, it is possible to further alleviate the electric field concentration throughout the insulating container 1 (i.e., to make the electric field strength (electric field distribution) more uniform).

In the above embodiment, it is assumed that there is a stepwise difference in the dielectric constant between a portion (i.e., the center) of the insulating container 1 and the other portions (i.e., both sides of the center). However, instead of this, as shown in FIG. 5, for example, there may be a continuous difference in the dielectric constant between a portion (i.e., the center) of the insulating container 1 and the other portions (i.e., both sides of the center). As a result, it is possible to further alleviate the electric field concentration throughout the insulating container 1 (i.e., to make the electric field strength (electric field distribution) more uniform).

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

<Surface resistance control material>
In the vacuum valve P according to the embodiment described above, the insulating container 1, a part of which is set to a dielectric constant different from that of the other parts, may have a large change in insulating performance 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, which makes the surface of the insulating container 1 (inner surface S1, outer surface S2) easily charged, making it difficult to maintain a constant insulating performance. In this case, a surface resistance control material is applied over the entire inner surface S1 or outer surface S2 or both surfaces S1 and S2 of the insulating container 1. This makes it possible to ensure the same effect as the embodiment described above while suppressing the generation of charging on the surface of the insulating container 1. In addition, for example, chromium oxide, silicon carbide, titanium nitride, vanadium, etc. can be applied as the surface resistance control material.

<Low secondary electron emission coefficient material>
The low secondary electron emission coefficient material has a function of suppressing emission of secondary electrons from the surface of the insulating container 1 in addition to the function of the surface resistance control material described above. In this case, instead of the surface resistance control material described above, a low secondary electron emission coefficient material is applied over the entire inner surface S1 or outer surface S2 or both surfaces S1 and S2 of the insulating container 1. This makes it possible to ensure the same effect as in the above embodiment while suppressing the generation of charge on the surface of the insulating container 1 and the emission of secondary electrons. Note that, for example, vanadium, chromium, carbon, iron, silicon carbide, copper, molybdenum, titanium nitride, etc. can be used as the low secondary electron emission coefficient material. However, since the resistance of the low secondary electron emission coefficient itself is often very small, it is necessary to prevent a sudden decrease in surface resistance by thin film processing or the like.

<Nonlinear resistance materials>
Instead of the above-mentioned surface resistance control material or low secondary electron emission coefficient material, a nonlinear resistance material may be applied over the entire surface of the inner surface S1 or outer surface S2 or both surfaces S1 and S2 of the insulating container 1. The nonlinear resistance material has a characteristic that the resistance value is small in the high dielectric constant region 1a and the resistance value is large in the low dielectric constant region 1b. This allows the nonlinear resistance characteristic to be expressed along the surface (inner surface S1, outer surface S2) of the insulating container 1 having a dielectric constant distribution in the virtual axis Px direction when a voltage is applied, and the electric field in the high electric field portion (for example, near the openings K1 and K2 of the insulating container 1) can be relaxed. For example, zinc oxide, silicon carbide, carbon, triiron tetroxide, etc. can be applied as the nonlinear resistance material. Here, when applying the nonlinear resistance material 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, so it is preferable to use an inorganic binder that does not contain organic matter.

<Nonlinear dielectric materials>
Instead of the nonlinear resistance material, a nonlinear dielectric material may be added (mixed) to a predetermined portion of the insulating container 1. The nonlinear dielectric material has a property that the dielectric constant is high in the high dielectric constant region 1a and low in the low dielectric constant region 1b. In this case, in the manufacturing method of 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. This makes it possible to improve the responsiveness to a relatively high frequency such as a commercial frequency to a lightning impulse voltage. As a result, even in the case of a high voltage or high frequency surge such as a lightning surge, it is possible to reduce the electric field concentration (i.e., to make the electric field intensity (electric field distribution) uniform) over the entire insulating container 1 while simultaneously suppressing the progress of creeping discharge on the outer surface S2 of the insulating container 1. Note that, for example, inorganic particles such as titanium dioxide, silicon dioxide, potassium titanate, and barium titanate can be used as the nonlinear dielectric material. Here, the high dielectric constant region 1a to which the nonlinear dielectric material has been added (mixed) may become a state in which discharge is likely to progress. Therefore, in order to avoid this, it is preferable to add (mix) the nonlinear dielectric material only to regions that are not in contact with creeping discharge, for example, only to the inner surface S1 side of the insulating container 1.

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

1...insulating container (vacuum container), 1a...high dielectric constant region, 1b...low dielectric constant region, 2...fixed side sealing member, 3...movable side sealing member, 4...airtightness maintaining mechanism, 5...arc shield, 6...fixed side sealing metal fitting, 7...movable side sealing metal fitting, 8...fixed contact, 9...fixed current-carrying shaft, 10...movable contact, 11...movable current-carrying shaft, P...vacuum valve, Px...imaginary 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 having dielectric properties and housing a pair of detachable electrodes and an arc shield ;
and a discharge progression suppression means for suppressing the progression of a creeping discharge when the creeping discharge occurs along the outer surface of the insulating container,
The discharge progress suppression means sets a dielectric constant of a part of the insulating container different from that of the other part ,
A vacuum valve in which a portion of the insulating container is provided adjacent to another portion and is shaped to accommodate the entire arc shield . The vacuum valve according to claim 1, wherein the discharge progression suppression means creates a difference in dielectric constant between one part of the insulating container and the other part. The vacuum valve according to claim 2, wherein the discharge progression suppression means provides a stepwise or continuous difference in dielectric constant between a portion of the insulating container and the other portion. The vacuum valve according to claim 1, wherein the discharge progression suppression means is provided continuously in a direction transverse to the direction of progression of the creeping discharge that progresses along the outer surface of the insulating container. The vacuum valve according to claim 1, wherein the discharge progression suppression means is provided on the outer surface or the inner surface of the insulating container, or on both the outer surface and the inner surface of the insulating container. The vacuum valve according to claim 1, wherein the insulating container is set in a use state in which its outer surface is exposed to the atmosphere. the discharge progression suppression means is provided in a part and another part of the insulating container, and is made of a plurality of insulating materials having different dielectric constants,
the insulating container is integrally formed from a plurality of the insulating materials,
2. The vacuum valve according to claim 1, wherein the insulating material integrally formed with one portion of the insulating container and the insulating material integrally formed with the other portion have different dielectric constants. the discharge progression suppression means is provided in a part and another part of the insulating container, and is made of a plurality of insulating materials having different dielectric constants,
The outer surface or the inner surface of the part and the other part of the insulating container, or both the outer surface and the inner surface of the part and the other part of the insulating container, are covered with the insulating materials different from each other;
6. The vacuum valve according to claim 5, wherein the insulating material covering one portion of the insulating container and the insulating material covering the other portion of the insulating container have different dielectric constants. The insulating container of the vacuum valve described in claim 7 or claim 8 is a vacuum valve configured by adding any one of a surface resistance control material, a low secondary electron emission coefficient material, a nonlinear resistance material, and a nonlinear dielectric material to a predetermined portion including its outer surface, inner surface, or both surfaces.

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