Vacuum valve

Abstract

To provide a low-cost vacuum valve capable of suppressing the emission of field electrons from a preset portion that may become the starting point of dielectric breakdown.SOLUTION: A vacuum valve includes a dielectric insulating container 1 having an internal space 1f maintained in a constant vacuum state, and various metal members E1, E2, 5, 6, 7, 10, 11, 12, 13 that are housed in the internal space of the insulating container and serve to pass and cut off electric current. From among all the surfaces of the metal members exposed to the internal space, predetermined portions are provided with molten layers 5p, 6p, 7p, 10p, 11p for suppressing the emission of field electrons. In terms of the surface roughness of the molten layer, when the arithmetic mean roughness Ra is the average value of a number of peaks that protrude in a direction perpendicular to the surface of the metal member on which the molten layer is provided, and the average distance between the peaks in the direction along the surface of the metal member on which the molten layer is provided is Rsm, the relationship Ra<Rsm is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a vacuum valve. [Background technology]

[0002] As a switching device for receiving and distributing electricity installed in a building or a large facility, for example, a switchgear equipped with a switch such as a circuit breaker or a disconnecting switch 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 constant insulating state by an insulating container, and a pair of electrodes are housed inside the insulating container so as to be connectable and disconnectable. In this case, by connecting and disconnecting the pair of electrodes, a fault current is interrupted and a load current is opened and closed, and power is stably supplied from the switchgear. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-089828 [Patent Document 2] JP 2020-042906 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, inside a vacuum valve (insulating container), for example, there are exposed parts where the electric field becomes high, such as electrodes and arc shields (for example, the surface of a metal member that becomes a high electric field), and when a voltage is applied, field electrons (primary electrons) are emitted from these parts (i.e., the metal surface) due to field emission. In particular, if there are irregularities or minute protrusions on the metal surface, the electric field becomes locally high starting from these irregularities or minute protrusions, which promotes the emission of field electrons, and may result in dielectric breakdown.

[0005] To reduce the risk of dielectric breakdown, it is necessary to suppress the emission of field electrons. One solution to this is the voltage conditioning treatment for metal surfaces described above. In voltage conditioning treatment, dielectric breakdown is intentionally repeated to improve voltage resistance (insulation performance). That is, when dielectric breakdown occurs, the discharge current flowing through the metal surface melts and smooths out irregularities and minute protrusions (reducing surface roughness). This makes it difficult for field electrons to be emitted, suppressing the breakdown current and increasing the breakdown voltage. As a result, voltage resistance (insulation performance) is improved.

[0006] However, in the voltage conditioning process, it is not possible to control the part (location, position, etc.) where the dielectric breakdown occurs. Therefore, it is not possible to perform the voltage conditioning process with high precision on a preset part (metal surface). This makes it difficult to sufficiently suppress the emission of field electrons when a voltage is applied, and as a result, there is a certain limit to the improvement of the voltage resistance performance (insulation performance).

[0007] One way to sufficiently suppress the emission of field electrons is, for example, to increase the number of times that insulation breakdown occurs during the manufacturing process of the vacuum valve. However, doing so increases the manufacturing cost of the vacuum valve by the amount of the increase in the number of times that it is repeated.

[0008] An object of the present invention is to provide a low-cost vacuum interrupter that is capable of suppressing emission of field electrons from a predetermined portion that may become the starting point of dielectric breakdown. [Means for solving the problem]

[0009] According to an embodiment, it includes an insulating container with an internal space maintained in a certain vacuum state and having dielectric properties, and various metal members accommodated in the internal space of the insulating container for conducting and interrupting current. Among all the surfaces of the metal members exposed to the internal space, a melting layer for suppressing the emission of field electrons is provided on a preset portion. Regarding the surface roughness of the melting layer, the arithmetic mean roughness Ra, which is the average value of a plurality of peaks protruding in a direction perpendicular to the surface of the metal member provided with the melting layer, and the average distance Rsm between the peaks in the direction along the surface of the metal member provided with the melting layer, satisfy the relationship Ra < Rsm.

Brief Description of the Drawings

[0010] [Figure 1] Internal configuration diagram of a vacuum valve according to an embodiment. [Diagram 2] Comparison diagram of the starting voltage of the field electron emission current. [Diagram 3] Diagram showing the relationship between the arithmetic mean roughness Ra and the average distance Rsm of the surface roughness of the melting layer.

Embodiments for Carrying Out the Invention

[0011] 「One Embodiment」 FIG. 1 is a basic configuration diagram of a vacuum valve P according to this embodiment. The vacuum valve P incorporates a technical concept applicable to both ordinary vacuum valves and molded vacuum valves. That is, the vacuum valve P has a fixed electrode E1, a movable electrode E2, an insulating container 1 (also referred to as a vacuum container), a fixed-side sealing member 2, a movable-side sealing member 3, an airtight maintenance mechanism 4, an arc shield 5, a fixed-side electric field relaxation shield 6, and a movable-side electric field relaxation shield 7.

[0012] In this embodiment, metal members such as the fixed electrode E1 (fixed contact 10 and fixed current-carrying shaft 12 described later), the movable electrode E2 (movable contact 11 and movable current-carrying shaft 13 described later), the arc shield 5, the fixed electric field mitigation shield 6, the movable electric field mitigation shield 7, and the airtightness maintaining mechanism 4 are housed in the internal space 1f of the insulating container 1. The insulating container 1 has dielectric properties, and the internal space 1f is maintained in a constant vacuum state. The above-mentioned metal members are constituent elements for passing and blocking current.

[0013] The fixed electric field reduction shield 6 and the movable electric field reduction shield 7 are components of a molded vacuum valve. When the vacuum valve P of this embodiment is configured as a molded vacuum valve, the outside of the insulating container 1 is molded with insulating resin (not shown). As the insulating resin, for example, epoxy resin, polyester resin, or the like is used.

[0014] 1, for example, the insulating container 1 is formed into a hollow cylindrical shape from an insulating material such as alumina ceramic, etc. The fixed side sealing member 2 and the movable side sealing member 3 are made of a metal material mainly composed of stainless steel, for example.

[0015] As shown in Fig. 1, a hollow cylindrical insulating container 1 is concentric with an imaginary axis Px that defines the center of a vacuum valve P. When viewed in the direction of the imaginary axis Px, the insulating container 1 is open at both ends. Both openings (fixed-side opening K1 and 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 8. 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 9.

[0016] 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 insulating container 1. The arc shield 5 is arranged so as to accommodate, inside thereof, the fixed contact 10 of the fixed electrode E1 and the movable contact 11 of the movable electrode E2.

[0017] The fixed electrode E1 and the movable electrode E2 are configured concentrically about the imaginary axis Px and extend in alignment along the imaginary axis Px. In this state, the fixed electrode E1 and the movable electrode E2 are positioned such that their respective electrode opposing surfaces (the fixed-side electrode opposing surface E1s and the movable-side electrode opposing surface E2s) face each other in parallel.

[0018] The fixed electrode E1 includes a fixed contact 10 and a fixed current-carrying shaft 12. The movable electrode E2 includes a movable contact 11 and a movable current-carrying shaft 13. The fixed contact 10 has a fixed-side electrode opposing surface E1s, and the movable contact 11 has a movable-side electrode opposing surface E2s.

[0019] The fixed contact 8 and the movable contact 10 are disk-shaped and have the same diameter, and are made of an alloy of a conductive material such as Cu or Ag and an arc-resistant material such as chromium (Cr), tungsten (W), tungsten carbide (WC), etc. The fixed conductive shaft 12 and the movable conductive shaft 13 are cylindrical and have the same diameter, and are made of a material with high conductivity (e.g., Cu).

[0020] The fixed contact 10 and the movable contact 11 are arranged opposite to each other so that their electrode opposing surfaces E1s, E2s face each other in parallel. The fixed contact 10 is connected to one end of a fixed current-carrying shaft 12, the other end of which is fixed to the vacuum valve P via a fixed-side sealing member 2 so as not to move along a virtual axis Px. The movable contact 11 is connected to one end of a movable current-carrying shaft 13, the other end of which is connected to an operating mechanism (not shown) via a movable-side sealing member 3.

[0021] Here, the movable current-carrying shaft 13 is moved along the imaginary axis Px by the operating mechanism. This allows the movable contact 11 to be brought into contact with or separated from the fixed contact 10, i.e., the electrode opposing surfaces E1s, E2s of both electrodes to be brought into contact or separated. As a result, the vacuum valve P can be opened and closed (the pair of electrodes E1, E2 can be brought into contact or separated).

[0022] Furthermore, an airtightness maintaining mechanism 4 is disposed between the movable current-carrying shaft 13 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 is expandable and contractible in the direction of the imaginary axis Px, and covers the outside of the movable current-carrying shaft 11 without any gaps.

[0023] 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 13. This ensures that the inside of the insulating container 1 is always kept airtight (i.e., vacuum state). As a result, when the vacuum valve P is opened or closed, the atmosphere (air) does not enter the inside of the insulating container 1, even while the movable current-carrying shaft 13 is being moved along the imaginary axis Px.

[0024] In addition, it is assumed that an electric field may concentrate at the joints where the insulating container 1 and the sealing members 2, 3 are joined via the above-mentioned sealing metal fittings 8, 9, when the vacuum valve P is opened or closed. In order to alleviate such electric field concentration, a fixed electric field alleviation shield 6 and a movable electric field alleviation shield 7 are provided.

[0025] 1, as an example, the fixed-side electric field mitigation shield 6 has a hollow cylindrical shape, is disposed so as to cover the above-mentioned joint portion when fixed to the fixed-side sealing member 2, and extends from the fixed-side sealing metal fitting 8 along the inside of the insulating container 1. An extending end 6t of the mitigation shield 6 is bent inward (i.e., in the direction of the fixed current-carrying shaft 12).

[0026] The movable-side electric field mitigation shield 7 has a hollow cylindrical shape, and is disposed so as to cover the above-mentioned joint portion when fixed to the movable-side sealing member 3, and extends from the movable-side sealing metal fitting 9 along the inside of the insulating container 1. An extending end 7t of the mitigation shield 7 is bent inward (i.e., in the direction of the movable current-carrying shaft 13).

[0027] In the internal space 1f of the insulating container 1, the above-mentioned metal members E1, E2, 5, 6, 7, 10, 11, 12, and 13 are in an exposed state where the electric field becomes high when a voltage is applied (i.e., the surface of the metal member where the electric field becomes high). In this case, depending on the surface condition of the metal member (for example, the surface condition where unevenness or minute protrusions (not shown) exist), the emission of field electrons from the surface may be promoted, leading to dielectric breakdown. In this case, in order to reduce the risk of dielectric breakdown, it is necessary to suppress the emission of field electrons.

[0028] 1, the vacuum valve P is provided with molten layers 5p, 6p, 7p, 10p, and 11p for suppressing emission of field electrons at least in predetermined portions of all surfaces of the metal members exposed to the internal space 1f. These molten layers 5p, 6p, 7p, 10p, and 11p achieve the same effect as the conventional voltage conditioning process described above.

[0029] That is, the molten layers 5p, 6p, 7p, 10p, and 11p smooth out the surface condition (e.g., irregularities and minute protrusions) of the metal member, reducing the surface roughness. This makes it difficult for electron emission to occur. This in turn suppresses the breakdown current and increases the breakdown voltage. This improves the voltage resistance performance (i.e., insulation performance). As a result, the risk of dielectric breakdown is reduced, and dielectric breakdown is suppressed.

[0030] The predetermined portion is a concept including both the entire surface of the metal member (i.e., the entire surface) and a part of the entire surface, i.e., a high electric field portion where the electric field becomes high when a voltage is applied. The high electric field portion includes a portion that may become the starting point of dielectric breakdown when a voltage is applied.

[0031] Furthermore, the parts (surfaces) that become a high electric field when a voltage is applied can be set in advance by an existing electromagnetic field (EMC) analysis method. In Fig. 1, as an example, the extension ends 5t on both sides of the arc shield 5, the extension end 6t of the fixed electric field reduction shield 6, the extension end 7t of the movable electric field reduction shield 7, the fixed electrode facing surface E1s, and the movable electrode facing surface E2s are each set as a high electric field part, and melt layers 5p, 6p, 7p10p, and 11p are provided along each high electric field part.

[0032] The melting layer 5p is provided in an annular band shape along the portion (surface) of the extending end 5t on both sides of the arc shield 5 that faces the electrodes E1, E2. The melting layer 6p is provided in an annular band shape along the portion (surface) of the extending end 6t of the fixed-side electric field reduction shield 6 that faces the fixed current-carrying shaft 12. The melting layer 7p is provided in an annular band shape along the portion (surface) of the extending end 7t of the movable-side electric field reduction shield 7 that faces the movable current-carrying shaft 13. The melting layer 10p is provided along the fixed-side electrode facing surface E1s. The melting layer 11p is provided along the movable-side electrode facing surface E2s. Note that the hatching shown in FIG. 1 shows the arrangement of the melting layers 5p, 6p, 7p10p, 11p, and does not show a cross section.

[0033] Furthermore, the molten layers 5p, 6p, 7p, 10p, and 11p are formed by irradiating a high-energy beam onto a preset portion of the entire surface of the metal member exposed to the internal space of the insulating container. The high-energy beam can be accurately irradiated toward the preset portion (surface) by an existing electron beam irradiation device (EPS: Electron Beam Processing System). The high-energy beam includes an electron beam, a laser beam, an ion beam, and a high-frequency plasma beam, and any of these beams can be irradiated by the above-mentioned electron beam irradiation device (EPS).

[0034] Here, it is assumed that the arc shield 5 is set in an electron beam irradiation device (EPS). In this case, the electron beam irradiation device (EPS) irradiates a high-energy beam along the extension ends 5t on both sides of the arc shield 5. The irradiation amount and irradiation time at this time are appropriately controlled according to the size and material of the extension ends 5t that are the targets.

[0035] As an example of controlling the irradiation of the high energy beam, the metal material constituting the metallic extension end 5t may be molten, and the beam may be irradiated onto the extension end 5t until the molten metal covers the entire extension end 5t. Then, the extension end 5t is covered with the molten metal that has spread in a thin film shape. After this, the molten metal is cooled.

[0036] At this time, the thickness of the thin film of molten metal is extremely thin, at a few μm or less (for example, 1 μm). Therefore, the molten metal can be cooled by any cooling method, for example, forced cooling by blowing cold air or natural cooling by leaving it in the natural environment.

[0037] This allows the molten layer 5p to be formed on a preset portion (surface). The same method as above can be used to form molten layers 6p, 7p10p, and 11p of optimal thickness for the other metal members 6, 7, 10, and 11. After this, the metal members 5, 6, 7, 10, and 11 with the molten layers 5p, 6p, 7p10p, and 11p formed thereon are fed into an assembly line to complete the vacuum valve P as shown in FIG. 1.

[0038] Fig. 2 is a comparison diagram of the field electron emission suppression effect. In Fig. 2, the voltage at which the field electron emission current starts to flow in the metal members 5, 6, 7, 10, and 11 is measured and compared in the case where the molten layers 5p, 6p, 7p, 10p, and 11p are present (with beam irradiation) and in the case where they are not (without beam irradiation).

[0039] The higher this voltage is, the more the field electron emission current is suppressed, and the insulating effect and the effect of suppressing partial discharge in vacuum can be expected. Then, as is clear from FIG. 2, it can be seen that the voltage in the case of having the molten layers 5p, 6p, 7p, 10p, 11p (with beam irradiation) is more than twice as large as the voltage in the case of not having them (without beam irradiation). Thus, it has been found that the case of having the molten layers 5p, 6p, 7p, 10p, 11p (with beam irradiation) has a higher effect of suppressing the emission of field electrons than the case of not having them (without beam irradiation).

[0040] FIG. 3 is a cross-sectional configuration diagram of the surface roughness of the molten layer. In FIG. 3, as an example, the surface roughness of the molten layers 5p, 6p, 7p, 10p, 11p provided on the above-described metal members 5, 6, 7, 10, 11 is shown in a cross-sectional view.

[0041] As shown in FIG. 3, in the molten layers 5p, 6p, 7p, 10p, 11p formed by the above-described beam irradiation, a plurality of peaks T with different heights are scattered at intervals over the entire surface. In this state, the relationship between the arithmetic mean roughness Ra and the mean spacing Rsm of the surface roughness of the molten layers 5p, 6p, 7p, 10p, 11p is set to satisfy the relationship Ra < Rsm.

[0042] The arithmetic mean roughness Ra is the average value of the heights of a plurality of peaks T protruding in a direction perpendicular to the surface M of the metal members 5, 6, 7, 10, 11 provided with the molten layers 5p, 6p, 7p, 10p, 11p. For example, assuming 100 peaks T, the value obtained by dividing the sum of the heights of each peak T by 100 is the arithmetic mean roughness Ra. Note that the height of each peak T is defined as the distance from the surface M of the metal members 5, 6, 7, 10, 11 to the apex of the peak T as viewed in a direction perpendicular to the surface M.

[0043] The average spacing Rsm is the average spacing between the peaks T in the direction along the surface M of the metal members 5, 6, 7, 10, and 11 on which the molten layers 5p, 6p, 7p, 10p, and 11p are provided. For example, assuming 100 peaks T, the average spacing Rsm is the sum of the spacing between the peaks T divided by 99. The spacing between the peaks T is defined as the distance between two adjacent peaks T when viewed in the direction along the surface M.

[0044] As described above, according to this embodiment, at least a predetermined portion of all the surfaces of the metal members 5, 6, 7, 10, 11 exposed to the internal space 1f of the insulating container 1 is provided with the molten layers 5p, 6p, 7p10p, 11p for suppressing the emission of field electrons. This makes it possible to achieve the same effect as the conventional voltage conditioning process described above. That is, the molten layers 5p, 6p, 7p10p, 11p smooth the surface state (e.g., unevenness or minute protrusions) of the metal members 5, 6, 7, 10, 11, and reduce the surface roughness. This makes it difficult for electron emission to occur. This suppresses the breakdown current and increases the breakdown voltage. This improves the withstand voltage performance (i.e., insulating performance). As a result, the risk of dielectric breakdown is reduced, and dielectric breakdown can be suppressed.

[0045] According to this embodiment, it is possible to control in advance the portion (location, position, etc.) where dielectric breakdown occurs. Therefore, it is possible to perform a process for smoothing (reducing surface roughness) a preset portion (metal surface) with high accuracy. This makes it possible to sufficiently suppress the emission of field electrons when a voltage is applied, and as a result, it is possible to dramatically improve the withstand voltage performance (insulation performance).

[0046] According to this embodiment, it is only necessary to provide the molten layers 5p, 6p, 7p, 10p, and 11p at predetermined locations, and there is no need to repeat the voltage conditioning process as in the conventional method. This allows the manufacturing cost of the vacuum valve P to be significantly reduced.

[0047] According to this embodiment, the relationship between the arithmetic mean roughness Ra and the mean spacing Rsm of the surface roughness of the molten layers 5p, 6p, 7p, 10p, and 11p is set to satisfy the relationship Ra < Rsm. Thereby, compared with the conventional voltage conditioning process, the smoothing of the surface of the molten layers 5p, 6p, 7p, 10p, and 11p or the accuracy of the surface roughness can be improved. As a result, the effect of suppressing the emission of field electrons during voltage application can be significantly enhanced compared to the prior art.

[0048] "Modification" In the above-described embodiment, the case where the molten layers 5p, 6p, 7p, 10p, and 11p are provided on a part of the metal members 5, 6, 7, 10, and 11 (the extending ends 5t, 6t, 7t, and the opposing surfaces E1s, E2s) is assumed. Instead, the molten layers 5p, 6p, 7p, 10p, and 11p may be uniformly provided on all surfaces (i.e., the entire surface) of the metal members 5, 6, 7, 10, and 11.

[0049] In the above-described embodiment, the current-carrying axes (metal members) 12 and 13 of the electrodes E1 and E2 were not particularly mentioned. However, a molten layer (not shown) may be provided on the surfaces of both current-carrying axes 12 and 13, thereby realizing the same effect as the above-described embodiment.

[0050] In the above-described embodiment, the molten layers 5p, 6p, 7p, 10p, and 11p obtained by partially melting and solidifying the surface of the metal member with a high-energy beam were applied. Instead, the molten layers 5p, 6p, 7p, 10p, and 11p manufactured separately may be retrofitted to a preset portion. In this case, when using the vacuum valve P, it is necessary to devise a way so that the retrofitted molten layer is not easily peeled off from the metal member.

[0051] Although one embodiment of the present invention and some modified examples have been described above, these embodiments and modified examples are presented as examples and are not intended to limit the scope of the invention. These embodiments and modified examples 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 modified examples are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0052] P...vacuum valve, 1...insulating container, 1f...internal space, 2...fixed side sealing member, 3...movable side sealing member, 4...airtightness maintaining mechanism, 5...arc shield, 5t...extension end, 6...fixed side electric field mitigation shield, 6t...extension end, 7...movable side electric field mitigation shield, 7t...extension end, 8...fixed side sealing metal fitting, 9...movable side sealing metal fitting, 10...fixed contact, 11...movable contact, 12...fixed current-carrying shaft, 13...movable current-carrying shaft, E1...fixed electrode, E2...movable electrode, E1s...fixed side electrode opposing surface, E2s...movable side electrode opposing surface, 5p, 6p, 7p10p, 11p...molten layer, M...surface, T...peak.

Claims

1. an insulating container having dielectric properties and an internal space maintained in a constant vacuum state; Various metal members are housed in the internal space of the insulating container and are used to pass and cut off electric current. A molten layer for suppressing emission of field electrons is provided on at least a predetermined portion of all surfaces of the metal member exposed to the internal space, In the surface roughness of the melt layer, the arithmetic mean roughness Ra is the average value of a plurality of peaks protruding in a direction perpendicular to the surface of the metal member on which the melt layer is provided, and the average distance between the peaks in a direction along the surface of the metal member on which the melt layer is provided is Rsm. A vacuum valve that satisfies the relationship Ra<Rsm.

2. The predetermined portion is a high electric field portion where an electric field becomes high when a voltage is applied, 2. The vacuum valve according to claim 1, wherein the high electric field portion includes a portion that may become a starting point of dielectric breakdown when a voltage is applied.

3. The metal member is A pair of electrodes detachably accommodated in the internal space of the insulating container; a cylindrical arc shield provided in the internal space of the insulating container and extending along the contact and separation direction so as to surround the pair of electrodes; The pair of electrodes is A pair of contacts arranged opposite each other so as to be movable together; a pair of current-carrying shafts each connected to a pair of the contacts, 2. The vacuum valve according to claim 1, wherein the molten layer is provided on a predetermined portion of all of the surfaces of the arc shield, the pair of contacts, and the pair of current-carrying shafts.

4. the insulating container has a hollow cylindrical shape with both ends open, and the openings at both ends are closed by sealing members via sealing fittings; the metal member has an electric field relaxation shield that relaxes electric field concentration at a joint between the insulating container and the sealing member via the sealing metal fitting, The vacuum valve according to claim 3, wherein the molten layer is provided on a predetermined portion of all of the surfaces of the arc shield including the electric field mitigation shield, the pair of contacts, and the pair of current-carrying shafts.

5. the molten layer is formed by irradiating a high-energy beam onto a predetermined portion of the entire surface of the metal member exposed to the internal space of the insulating container; 2. The vacuum valve according to claim 1, wherein the high energy beam includes an electron beam, a laser beam, an ion beam, and a high frequency plasma beam.

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