vacuum valve

Abstract

To provide a low-cost vacuum valve capable of keeping an insulation performance (cutoff performance) constant and maintaining a floating potential of an arc shield at an electrode opening time in an optimal state while utilizing an existing vacuum valve as it is without changing a design.SOLUTION: The present invention relates to a vacuum valve P comprising a cylindrical insulation container 1, in which electrodes E1 and E2 are accommodated in an approachable / separable state, and a cylindrical arc shield 5 extending so as to enclose the electrodes, and the insulation container is configured by connecting cylindrical insulation porcelain tubes 1a and 1b to both terminals T1 and T2 of the arc shield. The vacuum valve includes arc shield potential raising means 14 which raises a potential of the arc shield at an electrode opening time. The arc shield potential raising means is provided in contact with at least a partial region in an entire region including the insulation porcelain tubes constituting the insulation container and the arc shields, and electrostatic capacitance in the partial region is changed to be increased / decreased.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of this invention relate to vacuum valves.

Background Art

[0002] As a switching device for power reception and distribution provided in buildings and large facilities, for example, a switchgear equipped with a switch such as a circuit breaker or a disconnector is known. A vacuum valve is applied to the switchgear as a component of the switch. The inside of the vacuum valve is maintained in a certain insulating state by an insulating container, and a pair of electrodes are accommodated in the insulating container so as to be separable. In this case, by separating and contacting the pair of electrodes, the interruption of accident current and the opening and closing of load current are performed, and power is stably supplied from the switchgear.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the vacuum valve is opened (that is, the pair of electrodes are separated) when shifting from the energized state to the open state, arc discharge (hereinafter referred to as arc) generated between the electrodes locally heats, for example, the opposing surfaces of the electrodes (hereinafter referred to as electrode opposing surfaces), and the surface temperature rises. Depending on the degree of the rise in the surface temperature, for example, metal vapor may be ejected from the electrode opposing surface, or the electrode opposing surface may melt (dissolve), and a part thereof may diffuse into the insulating container. *Note: There seems to be a formatting issue with ID=38 in the original text where it has an extra asterisk (*) which is not present in the translation. It's possible this is an error in the original and should be removed. The translation has been done as per the provided rules while maintaining the original tags and line breaks.*

[0005] 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 0) is applied to the vacuum valve.

[0006] Methods for applying arc shields to vacuum valves include, for example, the projection clamping method, in which a projection that partially protrudes in a flange-like manner along the circumferential direction of the outer circumference of a cylindrical arc shield is clamped between two insulating tubes, and the double-ended clamping method, in which both ends of a 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) that is clamped between these insulating tubes.

[0007] 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 total length of the insulating tube that constitutes the insulating container to be shortened in the double-ended clamping method. As a result, the double-ended clamping method makes it possible to reduce the cost of the vacuum valve compared to the protruding clamping method.

[0008] On the other hand, the clamping method at both ends increases the area of ​​the arc shield that is exposed to the outside compared to the clamping method at the protruding part. In other words, with the clamping method at both ends, the entire length of the arc shield is exposed to the outside. For this reason, it becomes difficult to maintain the floating potential of the arc shield at an optimal state when transitioning from an energized state to an open state (in other words, when the vacuum valve is opened (i.e., when the electrodes are separated from each other)). The optimal floating potential (which can also simply be called the optimal potential) refers to the potential at 50% and its vicinity, which is the midpoint value, when the potential difference between one (movable) side and the other (fixed) side of the vacuum valve is defined as 100% when viewed in the direction of electrode separation.

[0009] 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 cylindrical metal member, and redesigning the external shield (also called an electric field mitigation shield) of a vacuum valve molded with insulating resin.

[0010] However, none of the above-mentioned methods for improving potential sharing can utilize existing vacuum valves as they are; they all involve 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 stray potential of the arc shield at open polarity in an optimal state, it may become impossible to maintain the insulation performance (breaking performance) that the existing vacuum valve originally possessed.

[0011] The object of the present invention is to provide a low-cost vacuum valve that can be used as is without requiring any design changes to the basic structure of existing vacuum valves, while maintaining the original insulation performance (breaking performance) of the vacuum valve at a constant level, and at the same time maintaining the stray potential of the arc shield at the time of opening at an optimal state. [Means for solving the problem]

[0012] According to the embodiment, the vacuum valve comprises a cylindrical insulating container housing electrodes that can be connected to and disconnected from each other, and a cylindrical arc shield extending to surround the electrodes. The insulating container is configured 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 electrode is open. The arc shield potential raising means is provided in contact with at least a portion of the entire region including the insulating tubes and arc shield that constitute the insulating container, and increases or decreases the capacitance in that portion of the region. [Brief explanation of the drawing]

[0013] [Figure 1] A diagram showing the internal structure of a vacuum valve according to an embodiment. [Figure 2] A diagram in which the floating capacitance shown in FIG. 1 is circuit-modeled. [Figure 3] A diagram showing the relationship between the thickness and relative permittivity of the arc shield potential raising means. [Figure 4] A diagram showing the internal structure of a vacuum valve according to a first modification. [Figure 5] A diagram showing the internal structure of a vacuum valve according to a second modification. [Figure 6] A diagram showing the internal structure of a vacuum valve according to a third modification. [Figure 7] A diagram showing the internal structure of a vacuum valve according to a fourth modification. [Figure 8] A diagram showing the internal structure of a vacuum valve according to a fifth modification. [Figure 9] A diagram showing the relationship between the coating length of the dielectric material and the change in the arc shield potential.

Embodiments for Carrying Out the Invention

[0014] "One embodiment" [[ID=…]] FIG. 1 is a diagram showing the basic structure of a vacuum valve P according to the present embodiment. 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 fitting 2, a movable-side sealing fitting 3, an airtightness maintaining mechanism 4, an arc shield 5, a fixed-side external shield 6, and a movable-side external shield 7.

[0015] In the example of FIG. 1, the fixed electrode E1, the movable electrode E2, and the airtightness maintaining 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 arranged is defined as one side of the insulating container 1, and on the opposite side, the side or region where the fixed electrode E1 and the fixed-side sealing fitting 2 are arranged is defined as the other side of the insulating container 1.

[0016] As shown in FIG. 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 is open at both ends when viewed in the direction of the virtual axis Px (in other words, also the direction of separation and contact of the electrodes E1 and E2 described later). Both openings (the fixed-side opening K1 and the movable-side opening K2) are covered by the fixed-side sealing fitting 2 and the movable-side sealing fitting 3. That is, 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.

[0017] The insulating container 1 is configured by connecting insulating barrier tubes (the fixed-side insulating barrier tube 1a and the movable-side insulating barrier 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 of separation and contact of the electrodes E1 and E2). That is, the movable-side insulating barrier tube 1b is connected to one end T1 of the arc shield 5, and the fixed-side insulating barrier tube 1a is connected to the other end T2 of the arc shield 5.

[0018] The insulating barrier tubes 1a and 1b have the same thickness as each other. These insulating barrier tubes 1a and 1b and the arc shield 5 have a hollow cylindrical shape centered on the virtual axis Px, and their respective dimensional sizes (radius, diameter) are set to be substantially the same as each other. As a result, the two insulating barrier tubes 1a and 1b and the arc shield 5 interposed between the insulating barrier tubes 1a and 1b are arranged straight and side by side along the virtual axis Px while extending along it.

[0019] In this state, the arc shield 5 is arranged so as to surround the pair of electrodes E1 and E2. Specifically, inside it (on the inner side), it houses the fixed contact 8 of the fixed electrode E1 and the movable contact 10 of the movable electrode E2, which will be described later.

[0020] Between the two ends T1 and T2 of the arc shield 5, there is a cylindrical main body portion 5m having a constant thickness that extends 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 the same configuration. The two ends T1 and T2 of the arc shield 5 are each composed of a connecting portion 5a and a transition portion 5b.

[0021] 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). When viewed radially with respect to 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 by, for example, 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.

[0022] 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).

[0023] 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 mainly composed of stainless steel, for example. 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 mainly composed of copper or stainless steel, for example.

[0024] 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 state, 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.

[0025] 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 (for example, copper (Cu), copper alloy, silver (Ag)).

[0026] The fixed contact 8 and the movable contact 10 are positioned opposite 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 so as not to move 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.

[0027] 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 to move 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).

[0028] 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 an expandable bellows, 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 can expand and contract in the direction of the virtual axis Px, and covers the outside of the movable energizing shaft 11 without any gaps.

[0029] The bellows 4 is joined to the movable side sealing fitting 3 at one end without any gaps, and to the movable energizing shaft 11 at the other end without any gaps. As a result, the inside of the insulating container 1 is always maintained in an airtight state (i.e., a vacuum state). Consequently, even when the movable energizing shaft 11 is moved 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.

[0030] 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.

[0031] Furthermore, the vacuum valve P, which is molded into a cylindrical shape using insulating resin 12, is provided with a conductive grounding layer 13 that covers the outside of the insulating resin 12. The grounding layer 13 is formed by, for example, applying conductive paint to the outer circumference of the cylindrical insulating resin 12 and is grounded.

[0032] Such molded vacuum valves P are provided with external shields (fixed-side external shield 6, movable-side external shield 7) to mitigate the concentration of electric fields 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).

[0033] 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 the entire surface of the fixed-side sealing fitting 2. The non-contact shield portion 6b does not contact the outer peripheral region of the insulating container 1, but extends continuously from the contact shield portion 6a in the direction of the virtual axis Px (the direction in which electrodes E1 and E2 move toward and away from each other) so as to partially surround the outer peripheral region.

[0034] 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 the entire surface of the movable sealing fitting 3. The non-contact shield portion 7b does not contact the outer peripheral region of the insulating container 1, but extends continuously from the contact shield portion 7a in the direction of the virtual axis Px (the direction in which electrodes E1 and E2 move toward and away from each other) so as to partially surround the outer peripheral region.

[0035] 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 performance of the arc shield potential raising means 14 and the insulating resin 12, which will be described later.

[0036] Here, the outer peripheral region of the insulating container 1 includes the outer peripheral region 1s that defines the outer circumference of both insulating tubes 1a and 1b described above, and the outer peripheral region 5s of the arc shield 5 that defines the outer circumference of the arc shield 5. The outer peripheral region 5s of the arc shield is defined by the area that includes the main body portion 5m described above and both ends T1 and T2 (connection portion 5a, transition portion 5b).

[0037] By the way, in a 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 viewing.

[0038] In FIGS. 1 and 2, C1 represents the parasitic capacitance between the fixed electrode E1 and the arc shield 5, C2 represents the parasitic capacitance between the movable electrode E2 and the arc shield 5, C3 represents the parasitic capacitance between the fixed-side external shield 6 and the arc shield 5, C4 represents the parasitic capacitance between the movable-side external shield 7 and the arc shield 5, and C5 represents the parasitic capacitance between the arc shield 5 and the ground layer 13, which are schematically shown.

[0039] In FIGS. 1 and 2, as an example, it is assumed that 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 is expressed as follows. That is, Vs = Vi×(C1 + C3) / (C1 + C2 + C3 + C4 + C5) Here, when the potential Vi of the fixed side is defined as 100%, the conditions for the potential Vs of the arc shield 5 to be 50% which is the intermediate value and the potential in its vicinity during energization are expressed as follows. That is, C1 + C3 = C2 + C4 + C5... Equation 1 Normally, the parasitic capacitances C1 and C2 in the insulating container 1 (i.e., in vacuum) are small, and the parasitic 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 Then, at the time of opening the electrode (when the vacuum valve P is opened (i.e., when the 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. At this time, if the creepage insulation distance of the insulating container 1 is not sufficient, there is a risk of breakdown.

[0040] In order to prevent the occurrence of such problems, the parasitic capacitances C3, C4, and C5 may be controlled so that Inequality 1 approaches Equation 1. As an example of the control method, a method of increasing the parasitic capacitance C3 on the high-potential side or a method of reducing the parasitic capacitances C4 and C5 on the grounded side is assumed.

[0041] 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 the potential Vs of the arc shield 5 when open to be increased while using the basic structure described above without any design changes.

[0042] 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.

[0043] 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 have the effect of raising the potential Vs of the arc shield 5 when the electrodes are open.

[0044] 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 region 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.

[0045] Furthermore, the arc shield potential raising means 14 is made of 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. Such arc shield potential raising means 14 are laminated without gaps 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.

[0046] As a method for laminating the arc shield potential raising means 14, for example, the desired film thickness can be set by applying a low dielectric constant material over the entire outer peripheral regions 1s and 5s of the insulating container 1. In this case, the outer contour of the coating layer made of the low dielectric constant material is configured to be a smooth cylindrical shape without irregularities.

[0047] Figure 3 shows the results of an electric field analysis that determined 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 the relative permittivity as parameters. According to this, by using a low relative permittivity and increasing the thickness of the coating layer, the potential of the arc shield 5 when the electrode is open can be increased.

[0048] As described above, according to this embodiment, a coating layer made of a low dielectric constant material can be provided as an arc shield potential raising means 14 while utilizing the existing vacuum valve P without any design changes to its basic structure. This reduces the cost of the vacuum valve P and, at the same time, maintains the original insulation performance (breaking performance) of the vacuum valve P while simultaneously reducing the stray capacitance C5 between the arc shield 5 belonging to the low potential side and the ground layer 13, and the stray capacitance C4 between one of the external shields 7 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% when viewed 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 when open in an optimal state.

[0049] 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 improves the flow of the arc shield potential raising means 14 and the insulating resin 12 through the gap W, for example, during casting. As a result, a decrease in yield during casting can be prevented.

[0050] "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 in Figure 4, the arc shield potential raising means 14 is provided in contact with both the arc shield 5 (outer peripheral region 5s of the arc shield) and the grounding layer 13, and extends between the arc shield 5 (outer peripheral region 5s of the arc shield) and the grounding layer 13.

[0051] 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 made. A temperature-variable dielectric material has the characteristic that its relative dielectric constant becomes low only when the temperature is rising. An expandable material has the characteristic of expanding with heat.

[0052] Furthermore, for temperature-variable dielectric materials, for example, if they are paraelectric materials other than ferroelectrics such as barium titanate, which form a ferroelectric phase within the operating temperature range or have a Curie temperature within the operating temperature range, the dielectric constant generally decreases with increasing temperature. For expansion materials, it is necessary to use materials that do not exhibit negative thermal expansion. Generally, insulating resins have a positive thermal expansion coefficient, but for insulating resins with added fillers, the overall thermal expansion coefficient of the material may become negative depending on the material and orientation of the filler or fibers. Also, since the thermal expansion coefficient may decrease due to phase transitions, it is desirable to use insulating resins below their glass transition temperature.

[0053] 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.

[0054] As a result, regardless of whether a temperature-variable dielectric material or an expandable material is applied as the arc shield potential raising means 14, the stray capacitance C5 between the arc shield 5 and the ground layer 13 can be reduced. As a result, it is possible to maintain the stray potential of the arc shield 5 at an optimal state when the pole is open. The other configurations and effects are the same as those of the embodiment described above, so their explanation is omitted. Furthermore, for disconnectors that are not responsible for interrupting the current, no arc is generated due to the interruption of the current, so the temperature of the arc shield does not rise. For this reason, neither a temperature-variable dielectric material nor an expandable material can be applied.

[0055] "Second variation" Figure 5 is a diagram showing the arrangement of the arc shield potential raising means 14 according to the 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 grounding layer 13.

[0056] This arrangement configuration can achieve 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 will be omitted.

[0057] "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).

[0058] In this case, the arc shield potential raising means 14 is made of 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.

[0059] 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 low-potential 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).

[0060] 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. A nonlinear dielectric material has 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 when there is no electric field (i.e., in the low electric field region) and high in the high electric field region.

[0061] 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 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 very large on the low-potential side (for example, on the external shield 7 side), and the relative dielectric constant does not become high. This eliminates the problems that occur when the high dielectric constant material described above is applied.

[0062] 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 without gaps 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 is thought to 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.

[0063] "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 in 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.

[0064] This arrangement configuration can achieve 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 will be omitted.

[0065] "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.

[0066] 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 important 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. On the other hand, 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 the embodiment.

[0067] "Other variations" In the embodiment and its modifications described above, 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.

[0068] 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 more than the outer peripheral region 5s of the arc shield, or the outer peripheral region 5s of the arc shield may be positioned to protrude more than the outer peripheral region 1s of the insulator tube. In either layout, as in the embodiment described above (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 configured as a smooth cylindrical shape without irregularities.

[0069] 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 a variety of 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 in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0070] 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

1. 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.

2. 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 and thereby molded into a predetermined contour shape.

3. 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 insulator, 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.

4. 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 that defines the outer circumference of the cylindrical insulating container.

5. 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.

6. 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 defining the outer periphery of the non-contact shield portion.

7. 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.

8. 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.

9. 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.

10. 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.

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