JP7830164B2 - vacuum valve - Google Patents

Description

This embodiment of the invention relates to a vacuum valve.

Switchgears equipped with switches such as circuit breakers and disconnectors are known as power distribution devices installed in buildings and large facilities. In these switchgears, vacuum valves are used as components of the switches. The inside of the vacuum valve is maintained in a constant state of insulation by an insulating container, and a pair of electrodes are housed inside this insulating container so as to be able to connect and disconnect. In this case, by connecting and disconnecting the pair of electrodes, fault currents are interrupted or load currents are switched on or off, and power is stably supplied from the switchgear.

Japanese Patent Publication No. 2021-150260 Patent No. 6519167 Japanese Patent Publication No. 2006-80036 Patent No. 5175516

Incidentally, when transitioning from an energized state to an open state, if the vacuum valve is opened (i.e., the pair of electrodes are separated), the arc discharge generated between the electrodes (hereinafter referred to as the arc) causes localized heating of, for example, the opposing surfaces of the electrodes (hereinafter referred to as the electrode opposing surfaces), raising their surface temperature. Depending on the degree of the surface temperature increase, for example, metal vapor may be ejected from the electrode opposing surfaces, or the electrode opposing surfaces may melt, and some of this may diffuse into the insulating container.

At this time, if metal vapor or molten material diffused from the electrode-facing surface adheres to the inner surface of the insulating container, the inner surface of the insulating container becomes contaminated, making it difficult to maintain a constant insulating performance (shutting performance) of the vacuum valve. To prevent this, a cylindrical metal arc shield with a stray potential (i.e., a voltage at which the current is zero) is applied to the vacuum valve.

Methods for applying arc shields to vacuum valves include, for example, the projection clamping method, in which a portion of the cylindrical arc shield's outer circumference is partially flanged and protrudes circumferentially, and this projection is clamped between two insulating tubes; and the double-ended clamping method, in which both ends of the cylindrical arc shield are clamped between two insulating tubes. In either clamping method, a single cylindrical insulating container is formed by two insulating tubes and the arc shield (or projection) clamped between these tubes.

In this case, with the double-ended clamping method, the arc shield is used as part of the insulating container along its entire length. This allows the overall length of the insulating tube required to constitute the insulating container to be shortened in the double-ended clamping method. As a result, the double-ended clamping method allows for lower costs for vacuum valves compared to the protruding clamping method.

On the other hand, the clamping method at both ends increases the area of the arc shield exposed to the outside compared to the clamping method at the protruding portion. That is, with the clamping method at both ends, the entire length of the arc shield is exposed to the outside. Therefore, it becomes difficult to maintain the arc shield's stray potential at an optimal level during the transition from the energized state to the open state (in other words, when the vacuum valve is opened (i.e., when the electrodes are separated)). The optimal stray potential (or simply the optimal potential) refers to, for example, the potential difference between one (movable) side and the other (fixed) side of the vacuum valve, when viewed in the direction of electrode separation, defined as 100%, and the potential at or near 50% of that value.

Conventionally, various methods have been proposed to improve the potential distribution of the arc shield in order to avoid such situations. For example, these include adding multiple sub-shields in addition to the arc shield, doubling the arc shield, covering the outside of a vacuum valve molded with insulating resin with a metal cylindrical member, and redesigning the external shield (also called an electric field mitigation shield) of a vacuum valve molded with insulating resin.

However, none of the above-mentioned methods for improving potential sharing can utilize existing vacuum valves as they are. They require various design changes, such as deformation or modification of the basic structure of the vacuum valve. Therefore, depending on the extent of the design changes, while it may be possible to maintain the arc shield's stray potential at an optimal state when the valve is open, it may become impossible to maintain the original insulation performance (breaking performance) of the existing vacuum valve.

The objective of this invention is to provide a low-cost vacuum valve that can maintain the original insulation performance (breaking performance) of an existing vacuum valve while simultaneously maintaining the stray potential of the arc shield at an optimal state when open, without requiring any design changes to the basic structure of the existing vacuum valve.

According to the embodiment, the vacuum valve comprises a cylindrical insulating container housing electrodes that can be connected and disconnected, and a cylindrical arc shield extending to surround the electrodes. The insulating container is constructed by connecting cylindrical insulating tubes to both ends of the arc shield, and has an arc shield potential raising means for raising the potential of the arc shield when the electrodes are open. The arc shield potential raising means is provided in contact with at least a portion of the entire area including the insulating tubes and arc shield constituting the insulating container, and increases or decreases the capacitance in that portion of the area.

A diagram showing the internal structure of a vacuum valve according to one embodiment. Figure 1 shows a circuit model of the stray capacitance. A diagram showing the relationship between the thickness of the arc shield potential raising means and the relative permittivity. A diagram showing the internal structure of a vacuum valve according to the first modified example. A diagram showing the internal structure of a vacuum valve according to the second modified example. A diagram showing the internal structure of a vacuum valve according to the third modified example. A diagram showing the internal structure of a vacuum valve according to the fourth modified example. A diagram showing the internal structure of a vacuum valve according to the fifth modified example. This figure shows the relationship between the coating length of the dielectric material and the change in arc shielding potential.

"One embodiment"
Figure 1 shows the basic structure of the vacuum valve P according to this embodiment. The vacuum valve P comprises a fixed electrode E1, a movable electrode E2, an insulating container 1 (also called a vacuum container), a fixed-side sealing fitting 2, a movable-side sealing fitting 3, an airtightness maintenance mechanism 4, an arc shield 5, a fixed-side external shield 6, and a movable-side external shield 7.

In the example shown in Figure 1, the fixed electrode E1, the movable electrode E2, and the airtightness maintenance mechanism 4 are housed in the insulating container 1. In this case, the side or region where the movable electrode E2 and the movable side sealing fitting 3 are located is defined as one side of the insulating container 1, and the side or region on the opposite side where the fixed electrode E1 and the fixed side sealing fitting 2 are located is defined as the other side of the insulating container 1.

As shown in Figure 1, the insulating container 1 has a hollow cylindrical shape centered on a virtual axis Px that defines the center of the vacuum valve P. The insulating container 1 has openings at both ends when viewed in the direction of the virtual axis Px (in other words, the direction of contact and separation of electrodes E1 and E2, as described later). Both openings (fixed-side opening K1 and movable-side opening K2) are covered by a fixed-side sealing fitting 2 and a movable-side sealing fitting 3. Specifically, one movable-side opening K2 of the insulating container 1 is closed by the movable-side sealing fitting 3. The other fixed-side opening K1 of the insulating container 1 is closed by the fixed-side sealing member 2.

The insulating container 1 is constructed by connecting insulating tubes (fixed insulating tube 1a and movable insulating tube 1b) to both ends (one end T1 and the other end T2) of the arc shield 5 in the direction of the virtual axis Px (the direction in which electrodes E1 and E2 move away from each other). Specifically, the movable insulating tube 1b is connected to one end T1 of the arc shield 5, and the fixed insulating tube 1a is connected to the other end T2 of the arc shield 5.

The insulating tubes 1a and 1b have the same thickness. These insulating tubes 1a and 1b, along with the arc shield 5, form a hollow cylindrical shape centered on a virtual axis Px, and their respective diameters (radius, diameter) are set to be approximately the same. As a result, both insulating tubes 1a and 1b, and the arc shield 5 interposed between them, are aligned straight along the virtual axis Px.

In this state, the arc shield 5 is positioned to surround the pair of electrodes E1 and E2, specifically, to house the fixed contact 8 of the fixed electrode E1 and the movable contact 10 of the movable electrode E2, which will be described later, inside it.

A cylindrical body portion 5m, having a constant thickness, is provided between the two ends T1 and T2 of the arc shield 5, extending along the direction of the virtual axis Px (the direction in which electrodes E1 and E2 move toward and away from each other). The two ends T1 and T2 of the arc shield 5 have identical configurations. Each end T1 and T2 of the arc shield 5 consists of a connecting portion 5a and a transition portion 5b.

The connection portion 5a has a constant thickness and extends along the direction of the virtual axis Px (the direction of contact and separation of electrodes E1 and E2). Viewed radially around the virtual axis Px, the thickness of the connection portion 5a is set to be thinner than the thickness of the main body portion 5m. The connection portion 5a can be connected to the insulating tubes 1a and 1b, for example, by brazing using silver solder. As a result, one end T1 (connection portion 5a) of the arc shield 5 is connected to the movable insulating tube 1b, and the other end T2 (connection portion 5a) of the arc shield 5 is connected to the fixed insulating tube 1a.

The transition section 5b is provided between the connection section 5a and the main body section 5m so as to continuously connect the connection section 5a to the main body section 5m. In the example in Figure 1, the transition section 5b has a tapered shape from the main body section 5m toward the connection section 5a (in other words, a widening shape from the connection section 5a toward the main body section 5m).

In the example shown in Figure 1 above, the fixed-side sealing fitting 2 and the movable-side sealing fitting 3 are made of a metal material, for example, stainless steel as the main component. The insulating tubes 1a and 1b are formed into a hollow cylindrical shape from an insulating material, such as alumina ceramic. The arc shield 5 is made of a metal material, for example, copper or stainless steel as the main component.

Furthermore, the fixed electrode E1 and the movable electrode E2 are arranged concentrically around a virtual axis Px and extend in alignment along the virtual axis Px. In this configuration, the fixed electrode E1 and the movable electrode E2 are positioned so that their respective electrode opposing surfaces E1s and E2s are parallel to each other.

The fixed electrode E1 comprises a fixed contact 8 and a fixed current-carrying shaft 9. The movable electrode E2 comprises a movable contact 10 and a movable current-carrying shaft 11. One of the electrode opposing surfaces E1s is provided on the fixed contact 8, and the other electrode opposing surface E2s is provided on the movable contact 10. The fixed current-carrying shaft 9 and the movable current-carrying shaft 11 are cylindrical in shape with the same diameter and are made of a highly conductive material (e.g., copper (Cu), copper alloy, silver (Ag)).

The fixed contact 8 and the movable contact 10 are arranged facing each other such that their respective electrode surfaces E1s and E2s are parallel to each other. The fixed contact 8 is connected to one end of the fixed energizing shaft 9, and the other end of the fixed energizing shaft 9 is fixed to the vacuum valve P immovably along the virtual axis Px via the fixed-side sealing fitting 2. The movable contact 10 is connected to one end of the movable energizing shaft 11, and the other end of the movable energizing shaft 11 is connected to an operating mechanism (not shown) via the movable-side sealing fitting 3.

Here, as shown in Figure 1, the movable energizing shaft 11 is moved along the virtual axis Px by the operating mechanism. This allows the movable contact 10 to move toward and toward the fixed contact 8; specifically, the opposing electrode surfaces E1s and E2s can be moved toward and toward each other. As a result, the vacuum valve P can be opened and closed (i.e., the pair of electrodes E1 and E2 can be moved toward and toward each other).

Furthermore, an airtightness maintenance mechanism 4 is positioned between the movable energizing shaft 11 and the movable side sealing fitting 3. The airtightness maintenance mechanism 4 is composed of a bellows with expandability, and the bellows (airtightness maintenance mechanism) 4 is made of a thin metal, such as stainless steel. The bellows 4 has a bellows-like shape that expands and contracts in the direction of the virtual axis Px, and completely covers the outside of the movable energizing shaft 11 without any gaps.

The bellows 4 is joined seamlessly at one end to the movable sealing fitting 3, and its other end is joined seamlessly to the movable energizing shaft 11. This ensures that the inside of the insulating container 1 is always airtight (i.e., a vacuum). As a result, even while the movable energizing shaft 11 is moving along the virtual axis Px during the opening and closing operation of the vacuum valve P, no air enters the inside of the insulating container 1.

In addition, the vacuum valve P having the basic structure described above, together with the arc shield potential raising means 14 described later, is covered with an insulating resin 12, thereby molding it into a predetermined contour shape. In the example in Figure 1, the vacuum valve P is molded into a cylindrical contour by the insulating resin 12. In this case, the insulating resin 12 can be, for example, epoxy resin or polyester resin.

Furthermore, the vacuum valve P, molded into a cylindrical shape using insulating resin 12, includes a conductive grounding layer 13 that covers the outside of the insulating resin 12. The grounding layer 13 is formed by, for example, applying a conductive paint to the outer circumference of the cylindrical insulating resin 12, and is grounded accordingly.

Such molded vacuum valves P are equipped with external shields (fixed-side external shield 6, movable-side external shield 7) to mitigate the electric field concentration on the sealing fittings 2 and 3 when energized or open. This reduces the electric field on these sealing fittings 2 and 3. The external shields 6 and 7 can be molded from, for example, a metal (conductive) material such as aluminum or stainless steel (SUS).

The fixed-side external shield 6 has a contact shield portion 6a and a non-contact shield portion 6b. The contact shield portion 6a contacts the fixed-side sealing fitting 2 and covers its entire surface. The non-contact shield portion 6b extends continuously from the contact shield portion 6a in the direction of the virtual axis Px (the direction of contact and separation of electrodes E1 and E2) without contacting the outer peripheral region of the insulating container 1, partially surrounding the outer peripheral region.

The movable external shield 7 has a contact shield portion 7a and a non-contact shield portion 7b. The contact shield portion 7a contacts the movable sealing fitting 3 and covers its entire surface. The non-contact shield portion 7b extends continuously from the contact shield portion 7a in the direction of the virtual axis Px (the direction of contact and separation of electrodes E1 and E2) without contacting the outer peripheral region of the insulating container 1, partially enclosing the outer peripheral region.

In this case, the gap W between the contact shield portions 6a and 7a of the external shields 6 and 7 and the outer peripheral region of the insulating container 1 is set to be at least half the thickness of the insulating tubes 1a and 1b. This improves the filling efficiency of the arc shield potential raising means 14 and the insulating resin 12, which will be described later.

Here, the outer periphery of the insulating container 1 includes the outer periphery region 1s defining the outer periphery of both insulating tubes 1a and 1b described above, and the outer periphery region 5s defining the outer periphery of the arc shield 5. The outer periphery region 5s of the arc shield is defined by the entire area including the main body portion 5m and both ends T1 and T2 (connection portion 5a, transition portion 5b).

By the way, in the molded vacuum valve P having the basic structure described above, when a voltage is applied to opposing conductors (electrodes E1, E2, arc shield 5, external shields 6, 7, and ground layer 13), an invisible capacitor (electric charge reservoir) is generated between them. This is called "stray capacitance" (simply put, capacitance). Figure 1 shows the stray capacitance generated in the molded vacuum valve P, and Figure 2 shows a circuit model that organizes this stray capacitance for easier visualization.

In Figures 1 and 2, C1 schematically represents the stray capacitance between the fixed electrode E1 and the arc shield 5, C2 represents the stray capacitance between the movable electrode E2 and the arc shield 5, C3 represents the stray capacitance between the fixed-side external shield 6 and the arc shield 5, C4 represents the stray capacitance between the movable-side external shield 7 and the arc shield 5, and C5 represents the stray capacitance between the arc shield 5 and the ground layer 13.

Figures 1 and 2 show, as an example, a case where a high voltage is applied to the fixed side (electrode E1, external shield 6) of the vacuum valve P, and the movable side (electrode E2, external shield 7, arc shield 5) is grounded. In this case, let the potential of the fixed side be Vi and the potential of the arc shield 5 be Vs. Then, the potential Vs of the arc shield 5 can be expressed as follows.
That is, Vs=Vi×(C1+C3)/(C1+C2+C3+C4+C5)
Here, if the potential Vi on the fixed side is defined as 100%, the conditions under which the potential Vs of the arc shield 5 becomes an intermediate value of 50% or near that value when energized can be expressed as follows: That is, C1 + C3 = C2 + C4 + C5 ... Equation 1
Normally, the stray capacitances C1 and C2 inside the insulating container 1 (i.e., in a vacuum) are small, while the stray capacitances C3, C4, and C5 in the insulating resin 12 are large. Therefore, the following relationship holds.
That is, C1+C3<C2+C4+C5... Inequality 1
Consequently, when the electrodes are open (when the vacuum valve P is opened, i.e., when electrodes E1 and E2 are separated from each other), the potential Vs of the arc shield 5 decreases, and as a result, an extreme voltage may be applied to one side of the insulating container 1. In this case, if the creepage distance of the insulating container 1 is insufficient, there is a risk of dielectric breakdown.

To prevent such malfunctions, the stray capacitances C3, C4, and C5 should be controlled to bring inequality 1 closer to equation 1. One possible control method is to increase the stray capacitance C3 on the high-potential side, or to decrease the stray capacitances C4 and C5 on the ground side.

Therefore, the vacuum valve P of this embodiment has an arc shield potential raising means 14 that can control the stray capacitances C3, C4, and C5. The arc shield potential raising means 14 allows for raising the potential Vs of the arc shield 5 when open, while utilizing the basic structure described above without any design changes.

The arc shield potential raising means 14 is provided in contact with at least a portion of the entire area, including both insulating tubes 1a and 1b that constitute the insulating container 1 and the arc shield 5, and increases or decreases the stray capacitances C3, C4, and C5 in that portion of the area.

Here, inside the insulating container 1 (in a vacuum), the stray capacitances C1 and C2 have small values. Therefore, even if the arc shield potential raising means 14 is provided inside the insulating container 1, it cannot be expected to increase the potential Vs of the arc shield 5 when the electrodes are open.

In this case, it is preferable that the arc shield potential raising means 14 be provided in contact with at least a portion of the outer peripheral regions 1s and 5s of the insulating container 1 described above. In the example in Figure 1, the arc shield potential raising means 14 is provided in contact with both the outer peripheral regions 1s of the insulating tubes 1a and 1b described above, and the outer peripheral region 5s of the arc shield 5, without contacting the grounding layer 13 described above.

Furthermore, the arc shield potential raising means 14 utilizes a low dielectric constant material, which has a lower dielectric constant than the insulating resin 12. Examples of low dielectric constant materials include resin materials such as silicone and polytetrafluoroethylene. This arc shield potential raising means 14 is seamlessly laminated across the entire outer peripheral regions 1s and 5s of the insulating container 1, including both insulating tubes 1a and 1b and the arc shield 5.

One method for laminating the arc shield potential raising means 14 is to apply a low dielectric constant material over the entire outer peripheral regions 1s and 5s of the insulating container 1, thereby setting the desired film thickness. In this case, the outer contour of the coating layer made of the low dielectric constant material is formed into a smooth cylindrical shape without irregularities.

Figure 3 shows the results of an electric field analysis determining how much the potential of the arc shield 5 (i.e., the floating potential) changes, using the thickness of the coating layer made of a low dielectric constant material and its relative permittivity as parameters. According to this, by using a material with a low relative permittivity and increasing the thickness of the coating layer, the potential of the arc shield 5 at the open electrode can be increased.

As described above, according to this embodiment, a coating layer made of a low dielectric constant material can be provided as the arc shield potential raising means 14, without requiring any design changes to the basic structure of the existing vacuum valve P. This reduces the cost of the vacuum valve P, maintains its original insulation performance (breaking performance) at a constant level, and simultaneously reduces the stray capacitance C5 between the arc shield 5 (belonging to the low potential side) and the ground layer 13, as well as the stray capacitance C4 between one of the external shields 7 (also belonging to the low potential side) and the arc shield 5. As a result, when the potential difference between one side and the other side of the vacuum valve P is defined as 100% in the direction of the virtual axis Px (the direction of contact and separation of electrodes E1 and E2), the stray potential of the arc shield 5 when open can be controlled to rise to an intermediate value of 50% or a potential near that value. Thus, it becomes possible to maintain the stray potential of the arc shield 5 at open state in an optimal condition.

According to this embodiment, the gap W between the contact shield portions 6a and 7a of the external shields 6 and 7 and the outer peripheral region of the insulating container 1 is set to be at least half the thickness of the insulating tubes 1a and 1b. This allows for improved flow of the arc shield potential raising means 14 and the insulating resin 12 through the gap W during casting, for example. As a result, a decrease in yield during casting can be prevented.

"First Variation"
Figure 4 is a diagram showing the arrangement of the arc shield potential raising means 14 according to the first modified example. In the example of Figure 4, the arc shield potential raising means 14 is provided in contact with both the arc shield 5 (arc shield outer peripheral region 5s) and the grounding layer 13, and extends between the arc shield 5 (arc shield outer peripheral region 5s) and the grounding layer 13.

In this case, the arc shield potential raising means 14 may be made of the low dielectric constant material described above, or alternatively, a temperature-variable dielectric material or an expandable material may be used. A temperature-variable dielectric material has the characteristic of having a lower relative dielectric constant only when the temperature is rising. An expandable material has the characteristic of expanding with heat.

Furthermore, for temperature-variable dielectric materials, for example, paraelectric materials other than ferroelectrics, such as barium titanate which forms a ferroelectric phase within the operating temperature range or which have a Curie temperature within the operating temperature range, generally show a decrease in dielectric constant with increasing temperature. The expanding material must be one that does not exhibit negative thermal expansion. While insulating resins generally have a positive thermal expansion coefficient, insulating resins with added fillers may have a negative overall thermal expansion coefficient depending on the material and orientation of the filler (such as fillers or fibers). Also, since a decrease in thermal expansion coefficient due to phase transitions is possible, it is desirable to use insulating resins below their glass transition temperature.

Here, when the electrodes are open, the arc generated between electrodes E1 and E2 diffuses and comes into contact with the arc shield 5, which may cause the temperature of the arc shield 5 itself to temporarily rise. In this case, in the arc shield potential raising means 14 using a temperature-variable dielectric material, the relative permittivity of the arc shield potential raising means 14 decreases due to the heated arc shield 5. On the other hand, in the arc shield potential raising means 14 using an expandable material, the arc shield potential raising means 14 expands due to the heated arc shield 5, increasing the distance between the arc shield 5 and the ground layer 13.

This allows for a reduction in the stray capacitance C5 between the arc shield 5 and the ground layer 13, regardless of whether a temperature-variable dielectric material or an expandable material is used as the arc shield potential raising means 14. As a result, the stray potential of the arc shield 5 during opening can be maintained at an optimal state. Note that the other configurations and effects are the same as those of the embodiment described above, and therefore their explanation is omitted. Furthermore, for disconnectors that are not responsible for current interruption, no arc is generated due to current interruption, and therefore the temperature of the arc shield does not rise. For this reason, neither the temperature-variable dielectric material nor the expandable material can be applied.

"Second variation"
Figure 5 is a diagram showing the arrangement of the arc shield potential raising means 14 according to a second modified example. In the example of Figure 5, the arc shield potential raising means 14 is provided in contact with the arc shield 5 (outer peripheral region 5s of the arc shield) without contacting the ground layer 13.

This arrangement configuration achieves the same effects as the arrangement configuration of the first modified example described above. Note that the other configurations and effects are the same as those of the embodiment described above, and therefore their explanation is omitted.

"Third variation"
Figure 6 is a diagram showing the arrangement of the arc shield potential raising means 14 according to the third modified example. In the example in Figure 6, the arc shield potential raising means 14 is provided in contact with both external shields 6 and 7. Specifically, the arc shield potential raising means 14 is filled between the non-contact shield portions 6b and 7b of the external shields 6 and 7 and the outer peripheral region of the insulating container 1 surrounded by the non-contact shield portions 6b and 7b (i.e., the outer peripheral region 1s of the insulator tube).

In this case, the arc shield potential raising means 14 uses a high dielectric constant material with a higher dielectric constant than the insulating resin 12. Examples of high dielectric constant materials include resin materials such as barium titanate and strontium titanate.

This arrangement configuration allows for an increase in the stray capacitances C3 and C4 between the arc shield 5 and the external shields 6 and 7. However, applying a high dielectric constant material to the low-potential side (e.g., the external shield 7 side) may increase the stray capacitance C4 on that side, potentially reducing the potential improvement effect. In this case, it is preferable to apply the high dielectric constant material only to the high-potential side (e.g., the external shield 6 side).

Here, the effect of increasing the stray capacitances C3 and C4 as described above can also be achieved by applying, for example, a nonlinear dielectric material as the arc shield potential raising means 14 instead of a high dielectric constant material. Nonlinear dielectric materials have the characteristic that the dielectric constant of the material changes nonlinearly in response to the magnetic field strength; in other words, the relative permittivity is low in the absence of an electric field (i.e., in the low electric field region) and high in the high electric field region.

Therefore, as shown in Figure 6, by providing a nonlinear dielectric material in contact with both external shields 6 and 7, the area near the external shields 6 and 7 becomes locally high in dielectric constant when the electrodes are open, thus achieving the same effect as the high dielectric constant material described above. In this case, the magnetic field strength does not become significantly larger on the low-potential side (for example, on the external shield 7 side), and the relative dielectric constant does not become high either. This eliminates the drawbacks that occur when applying the high dielectric constant material described above.

Furthermore, when a nonlinear dielectric material is applied, for example, as shown in Figure 1, the arc shield potential raising means 14 may be laminated seamlessly over the entire outer peripheral regions 1s and 5s of the insulating container 1, including both insulating tubes 1a and 1b and the arc shield 5. In this case, the nonlinear dielectric material could be, for example, a ferroelectric material such as barium titanate or strontium titanate added as a filler to an insulating resin such as epoxy resin.

"Fourth variation"
Figure 7 is a diagram showing the arrangement of the arc shield potential raising means 14 according to the fourth modified example. In the example of Figure 7, the arc shield potential raising means 14 is provided in contact with the outer peripheral regions 6s, 7s that define the outer periphery of the non-contact shield portions 6b, 7b of the outer shields 6, 7. Specifically, the arc shield potential raising means 14 is provided in contact with both the outer shields 6, 7 (non-contact shield portions 6b, 7b) and the ground layer 13, and extends between the outer shields 6, 7 (non-contact shield portions 6b, 7b) and the ground layer 13.

This arrangement configuration achieves the same effects as the arrangement configuration of the third modified example described above. Note that the other configurations and effects are the same as those of the embodiment described above, and therefore their explanation is omitted.

"Fifth Variation"
Figure 8 is a diagram showing the arrangement of the arc shield potential raising means 14 according to the fifth modified example. In the example shown in Figure 8, the arc shield potential raising means 14 is arranged over a region extending from the high potential side to the low potential side. Specifically, the arc shield potential raising means 14 is provided between the grounding layer 13 and the fixed-side insulating tube 1a and the arc shield 5, while partially contacting both of them.

In this case, the arc shield potential raising means 14 can be selectively applied to, for example, the low dielectric constant material, high dielectric constant material, nonlinear dielectric material, temperature-variable dielectric material, and expandable material as appropriate. However, as shown in Figure 9, it is necessary to note that if the coating length of the high dielectric constant material is made too long, the floating potential of the arc shield 5 will rise excessively. In contrast, if the low dielectric constant material is extended as in the embodiment described above (see Figure 1), the low dielectric constant material will be present around the arc shield 5, thereby achieving the same effect as in that embodiment.

"Other variations"
In the embodiment described above and in each of its modifications, the positional relationship between the outer peripheral regions 1s of the insulator tubes 1a and 1b and the outer peripheral region 5s of the arc shield 5 in the direction of the virtual axis Px was not specifically mentioned. However, these outer peripheral regions 1s of the insulator tubes and the outer peripheral region 5s of the arc shield may or may not be positioned flush with each other along the same cylindrical surface.

For example, when viewed radially with respect to the virtual axis Px, the outer peripheral region 1s of the insulator tube may be positioned to protrude beyond the outer peripheral region 5s of the arc shield, or the outer peripheral region 5s of the arc shield may be positioned to protrude beyond the outer peripheral region 1s of the insulator tube. In either layout, as in the above-described embodiment (see Figure 1), when the arc shield potential raising means 14 is stacked over the entire outer peripheral regions 1s and 5s of the insulating container 1, the outer contour formed by the arc shield potential raising means 14 is a smooth cylindrical shape without irregularities.

The above describes one embodiment of the invention and several variations. These embodiments and variations are presented as examples only 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 spirit of the invention. These embodiments and variations are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as described in the claims.

1…Insulating container, 1a…Fixed-side insulating tube, 1b…Movable-side insulating tube, 1s…Outer circumference region of the insulating tube, 2…Fixed-side sealing fitting, 3…Movable-side sealing fitting, 4…Airtightness maintenance mechanism, 5…Arc shield, 5m…Main body, 5a…Connection part, 5b…Transition part, 5s…Outer circumference region of the arc shield, 6…Fixed-side external shield, 7…Movable-side external shield, 6a, 7a…Contact shield part, 6b, 7b…Non-contact shield part, 8…Fixed contact, 9…Fixed current-carrying shaft, 10…Movable contact, 11…Movable current-carrying shaft, 12…Insulating resin, 13…Grounding layer, 14…Arc shield potential raising means, P…Vacuum valve, E1…Fixed electrode, E2…Movable electrode, K1…Fixed-side opening, K2…Movable-side opening, T1…One end, T2…Other end.

Claims (10)

A cylindrical insulating container that houses a pair of electrodes so as to be able to move them apart, and has openings at both ends in the direction in which the electrodes move apart and apart,
The device comprises a cylindrical arc shield extending along the direction of separation so as to surround the pair of electrodes,
The insulating container is a vacuum valve configured by connecting cylindrical insulating tubes to both ends of the arc shield in the direction of separation and contact,
It has an arc shield potential raising means for raising the potential of the arc shield when the electrode is open,
The arc shield potential raising means is a vacuum valve provided in contact with at least a portion of the entire region, including both insulating tubes and the arc shield that constitute the insulating container, and which increases or decreases the capacitance in the portion of the region. The vacuum valve according to claim 1, wherein the vacuum valve, together with the arc shield potential raising means, is covered with an insulating resin, thereby being molded into a predetermined contour shape. Between the two ends of the arc shield, there is a cylindrical body portion having a certain thickness and extending along the direction of separation.
The aforementioned ends of the arc shield are,
A connecting portion having a certain thickness and extending along the direction of separation and connection, which can be connected to the insulating tube,
It consists of a connecting portion and a transition portion provided between the connecting portion and the main body so as to connect the connecting portion to the main body in a continuous manner,
The vacuum valve according to claim 1, wherein the thickness of the connecting portion is set to be thinner than the thickness of the main body portion. The vacuum valve according to claim 2, wherein the arc shield potential raising means is provided in contact with at least a portion of the outer peripheral region defining the outer circumference of the cylindrical insulating container. The outer peripheral region of the insulating container includes an outer peripheral region of the insulating tube that defines the outer circumference of each of the insulating tubes, and an outer peripheral region of the arc shield that defines the outer circumference of the arc shield.
The vacuum valve according to claim 4, wherein the arc shield potential raising means is provided in contact with at least one of the outer peripheral regions of the insulator tube, or only the outer peripheral region of the arc shield, or both the outer peripheral region of the insulator tube and the outer peripheral region of the arc shield. The aforementioned vacuum valve is
A sealing fitting that closes the openings at both ends of the insulating container,
The device comprises an external shield to mitigate the concentration of the electric field on the sealing fitting ,
The aforementioned external shield is
A contact shield portion that contacts the sealing fitting and covers the sealing fitting,
The insulating container has a non-contact shield portion that extends continuously from the contact shield portion in the direction of separation without contacting the outer peripheral region, so as to partially surround the outer peripheral region.
The vacuum valve according to claim 4, wherein the arc shield potential raising means is provided in contact with the outer peripheral region that defines the outer peripheral region of the non-contact shield portion. The vacuum valve according to claim 6, wherein the gap between the contact shield portion of the external shield and the outer peripheral region of the insulating container is set to be 1/2 or more of the thickness of the insulating tube. The vacuum valve, which is molded from the insulating resin into a predetermined contour shape,
It comprises a conductive grounding layer provided so as to cover the outside of the insulating resin,
The vacuum valve according to claim 6, wherein, when the potential difference between one side and the other side of the vacuum valve is defined as 100% when viewed in the aforementioned moving-away direction, the arc shield potential raising means has the function of reducing the capacitance between the arc shield belonging to the low potential side and the ground layer such that the potential of the arc shield when open becomes 50% or near that intermediate value. The vacuum valve, which is molded from the insulating resin into a predetermined contour shape,
It comprises a conductive grounding layer provided so as to cover the outside of the insulating resin,
The vacuum valve according to claim 6, wherein, when viewed in the aforementioned connecting/closing direction, the potential difference between one side of the vacuum valve and the other side is defined as 100%, the arc shield potential raising means has the function of reducing the capacitance between the outer shield belonging to the lower potential side and the arc shield so that the potential of the arc shield when open becomes 50% or near that intermediate value. The vacuum valve, which is molded from the insulating resin into a predetermined contour shape,
It comprises a conductive grounding layer provided so as to cover the outside of the insulating resin,
The vacuum valve according to claim 6, wherein, when viewed in the aforementioned moving-away direction, the potential difference between one side and the other side of the vacuum valve is defined as 100%, the arc shield potential raising means has the function of increasing the capacitance between the other external shield belonging to the higher potential side and the arc shield so that the potential of the arc shield when open becomes 50% or near that intermediate value.