JP2019110010A - Vacuum valve - Google Patents

Abstract

An object is to provide a vacuum valve having a high creeping withstand voltage of a vacuum insulating container.
A cylindrical vacuum insulating container made of ceramic and having openings at both ends, a pair of electrodes housed in the vacuum insulating container and capable of coming into contact with each other, and the openings at both ends of the vacuum insulating container A vacuum valve comprising: a lid closing each of the lids; and a low secondary electron emission coefficient layer respectively formed on inner wall surfaces of both ends of the vacuum insulating container and made of a material having a secondary electron emission coefficient lower than that of the ceramic.
[Selected figure] Figure 1

Description

  Embodiments of the present invention relate to vacuum valves.

  A high electric field is applied to the inner surface of the ceramic vacuum insulation container (insulator container) of the vacuum valve, which is the current interrupting portion of the vacuum circuit breaker, when no current is applied. When the surface of the vacuum insulation container can not withstand a high electric field, dielectric breakdown occurs on the surface of the vacuum insulation container. Since the creepage surface of the vacuum insulation container has smaller dielectric strength than the vacuum itself, it is required to improve the withstand voltage of the creepage surface of the vacuum insulation container.

  In particular, in the solid insulated switchgear in which the vacuum valve is covered with an epoxy resin and the outer periphery thereof is grounded, a ground potential exists near the vacuum valve as compared to the air insulated switchgear. For this reason, since a high electric field is applied to the creeping surface of the vacuum insulating container of the vacuum valve, the need to improve the withstand voltage thereof is further heightened. Therefore, various measures have conventionally been proposed.

JP, 2014-17220, A

  As described above, in the vacuum valve, conventionally, it has been required to increase the creeping withstand voltage of the vacuum insulating container.

  The problem to be solved by the present invention is to provide a vacuum valve having a high creeping withstand voltage of a vacuum insulating container.

  The vacuum valve according to the embodiment includes a cylindrical vacuum insulating container made of ceramic and having openings at both ends, a pair of electrodes that can be separated and contacted, housed in the vacuum insulating container, and the above-mentioned both ends of the vacuum insulating container. A lid for closing the opening and a low secondary electron emission coefficient layer respectively formed on inner wall surfaces of both ends of the vacuum insulating container and made of a material having a secondary electron emission coefficient lower than that of the ceramic There is.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows typically the longitudinal cross-section structure of the vacuum valve which concerns on 1st Embodiment. The figure which shows typically the state of the front-end | tip periphery of the electric field relaxation shield of the vacuum valve of FIG. FIG. 6 schematically shows an example of a formation pattern of a low secondary electron emission coefficient layer. FIG. 7 schematically shows another example of the formation pattern of the low secondary electron emission coefficient layer. The figure which shows typically the longitudinal cross-section structure of the vacuum valve which concerns on 2nd Embodiment. The figure for demonstrating the measuring method of a dielectric breakdown voltage. The graph which shows the measurement result of dielectric breakdown voltage. FIG. 7 is a view schematically showing a state around the tip of the electric field relaxation shield when there is no low secondary electron emission coefficient layer.

  Hereafter, the vacuum valve of embodiment is demonstrated with reference to drawings.

  FIG. 1 is a view schematically showing a longitudinal sectional configuration of the vacuum valve 100 according to the first embodiment. As shown in FIG. 1, the vacuum valve 100 comprises a cylindrical vacuum insulating container 101 made of ceramic and having openings at both ends. Inside the vacuum insulation container 101, a pair of electrodes consisting of the fixed side electrode 102 and the movable side electrode 103 are disposed so as to be capable of coming into and coming out of contact with each other. The stationary side conductive shaft 104 is connected to the stationary side electrode 102. Further, the movable side conductive shaft 105 is connected to the movable side electrode 103.

  An arc shield 106 is disposed around the fixed electrode 102 and the movable electrode 103 so as to surround them. Further, plate-like flanges 107 and 108 are disposed on the top and bottom of the vacuum insulation container 101 as lids covering the opening of the vacuum insulation container 101, respectively.

  The stationary side conduction shaft 104 extends through the flange 107 to the outside of the vacuum insulation container 101. Further, the movable side energization shaft 105 extends through the flange 108 to the outside of the vacuum insulating container 101, and between the movable side energization shaft 105 and the flange 108, the space between them is hermetically sealed. In addition, a bellows 109 is provided which allows the movable side energizing shaft 105 to move along the axial direction.

  At the periphery of the flanges 107 and 108, electric field relaxation shields 110 and 111 having a shape protruding toward the inside of the vacuum insulation container 101 and bent at the tip end side wall side of the vacuum insulation container 101 are disposed. . Further, as shown in FIG. 2 which is an enlarged view of the main part of the vacuum valve 100, a metallized layer 112 for joining to the flanges 107 and 108 is formed on the end face of the vacuum insulating container 101.

  From the material having a low secondary electron emission coefficient so as to extend from the both end portions including the metallized layer 112 to the region facing the electric field relaxation shields 110 and 111 and further to the inside of the inner wall surface of the vacuum insulation container 101 A low secondary electron emission coefficient layer 113 is formed. The low secondary electron emission coefficient layer 113 is preferably disposed on the inner wall surface of the vacuum insulation vessel 101, particularly at a portion where the electric field strength is high. The low secondary electron emission coefficient layer 113 is formed on the inner wall surface of the vacuum insulation container 101 without providing a convex portion or the like, and can be easily formed.

  For example, in the vacuum insulation container 101, the electric field strength of both end portions in the axial direction joined to the flanges 107 and 108 tends to be high. For this reason, electric field relaxation shields 110 and 111 are provided at both end portions in the axial direction of the vacuum insulation container 101. In the case of the configuration having the electric field relaxation shields 110 and 111 as described above, the electric field strength of the inner wall surface portion of the vacuum insulating container 101 opposed to the tips of the electric field relaxation shields 110 and 111 tends to be high.

  Therefore, the low secondary electron emission coefficient layer 113 includes the inner wall surface portion of the vacuum insulation container 101 opposed to the electric field relaxation shields 110 and 111 from the end of the vacuum insulation container 101 including the metallized layer 112. Preferably, it is formed so as to extend, for example, about several cm (for example, about 1 to 3 cm) further inward from a portion facing the tip end portion of H.111. As described later, the low secondary electron emission coefficient layer 113 is not formed on the entire inner wall surface of the vacuum insulating container 101, but is formed to be discontinuous at least in the axial direction.

As a material having a low secondary electron emission coefficient for forming the low secondary electron emission coefficient layer 113, for example, V, Cr, C, Fe, SiC, Cu, Mo, TiN, Cr ₂ O ₃ or the like is used. be able to. The material may have a low secondary electron emission coefficient, and its resistance value is not particularly limited.

  As described above, when the low secondary electron emission coefficient layer 113 is formed, as shown in FIG. 2, the inner wall surface (low secondary electron emission coefficient layer 113) of the vacuum insulating container 101 of the vacuum valve 100 is primary. When the electrons 301 collide, the emission of secondary electrons 302 can be suppressed.

In the case where the low secondary electron emission coefficient layer 113 is not formed on the inner wall surface of the vacuum insulating container 101 as shown in FIG. 8 and the primary electrons 301 directly collide with the ceramic inner wall surface of the vacuum insulating container 101. Since ceramics such as Al ₂ O ₃ have a high secondary electron emission coefficient, many secondary electrons 302 are emitted. Then, when a large number of secondary electrons 302 are emitted when the primary electrons 301 collide, the inner wall surface of the vacuum insulation container 101 is charged and the creeping withstand voltage is lowered. On the other hand, in the vacuum valve 100 of the present embodiment, the discharge of the secondary electrons 302 is suppressed, whereby the charging is suppressed, and the creeping withstand voltage can be improved.

  However, in general, materials having a low secondary electron emission coefficient are often conductors. Therefore, if film formation is uniformly performed on the entire inner wall of the vacuum insulation container 101, the secondary electron emission coefficient is lowered, and the resistance value is greatly reduced, so that it can not function as an insulator. Therefore, in the present embodiment, the low secondary electron emission coefficient layer 113 is formed only at a portion where the electric field is high, such as around the flanges 107 and 108 and around the electric field relaxation shields 110 and 111. Although this suppresses secondary electron emission generated at a portion where the electric field is high, the resistance value of the vacuum insulating container 101 as a whole is not greatly reduced.

  In order to prevent the resistance value of the vacuum insulating container 101 as a whole from being greatly reduced, the length of each low secondary electron emission coefficient layer 113 along the axial direction of the vacuum insulating container 101 is equal to that of the vacuum insulating container 101. It is preferable to form in about 10% or less range with respect to a full length, and it is further more preferable to be 5% or less. For example, when the overall length of the vacuum insulation container 101 is about 100 cm, the length along one axial direction of the low secondary electron emission coefficient layer 113 is preferably 10 cm or less, and more preferably 5 cm or less.

  The low secondary electron emission coefficient layer 113 may be formed in a band shape along the inner wall surface of the vacuum insulating container 101, for example, as shown in FIG. As shown in 4, it may be formed in stripes at intervals. As described above, by forming the low secondary electron emission coefficient layer 113 at intervals in the axial direction of the vacuum insulating container 101, it is possible to suppress a decrease in the resistance value of the vacuum insulating container 101, and also locally It is possible to lower the secondary electron emission coefficient. In FIG. 3 and FIG. 4, the portions where the low secondary electron emission coefficient layer 113 is formed are hatched to be distinguished from the other portions.

  Next, the configuration of the vacuum valve 200 of the second embodiment will be described with reference to FIG. FIG. 5 is a view schematically showing a longitudinal sectional configuration of a vacuum valve 200 according to a second embodiment. In the vacuum valve 200 according to the second embodiment, the outside of the ceramic vacuum insulation container 101 is covered with a solid insulator layer 201 such as epoxy resin, and the periphery of the solid insulator layer 201 is connected to the ground potential. A ground potential layer 202 is provided. In addition, about another structure, since it is the same as that of the vacuum valve 100 of 1st Embodiment, the same code | symbol is attached | subjected to a corresponding part and the duplicate description is abbreviate | omitted.

  In the vacuum valve 200 configured as described above, the ground potential due to the ground potential layer 202 is present in the vicinity of the vacuum insulation container 101, so the electric field applied to the surface of the vacuum insulation container 101 is increased. Therefore, compared with the case of the vacuum valve 100, it has a structure in which dielectric breakdown is more likely to occur on the surface. For this reason, it is more important to improve the creeping withstand voltage by providing the low secondary electron emission coefficient layer 113.

Next, the effects of forming a film of a material having a low secondary electron emission coefficient will be described with reference to the results of experiments conducted by measuring the dielectric breakdown voltage. The dielectric breakdown voltage was measured, as shown in FIG. 6, by using a ceramic (Al) having a diameter (D) of 20 mm in diameter (D) between which various films were formed between high-voltage electrodes 220 with a distance (L) of 15 mm. A cylindrical member 230 made of ₂ O ₃ ) was disposed, and the voltage at which dielectric breakdown occurred was measured.

The material of the formed film is V (secondary electron emission coefficient: 1.3), C (secondary electron emission coefficient: 0.8), SiC (secondary electron emission coefficient: 2), Cr ₂ O ₃ (two The next electron emission coefficient: 1.4). The film formation was performed by ion plating. Moreover, the film thickness was about several nanometers. For comparison, the measurement was also performed on a cylindrical member made of Al ₂ O ₃ (secondary electron emission coefficient: 7) without forming a film on the surface.

The measurement result of said dielectric breakdown voltage is shown on the graph of FIG. The vertical axis represents the average dielectric breakdown voltage, and is indicated by a relative value, with the case of a cylindrical member made of Al ₂ O ₃ and having no film formed on the surface as 1.0. As shown in FIG. 7, the surface of the Al ₂ O ₃ made of columnar member, by the Al ₂ O ₃ than the secondary electron emission coefficient to form a film of low material, it can be seen that the breakdown voltage is increased. In this case, if SiC, V, or Cr ₂ O ₃ is used as a film of a material having a low secondary electron emission coefficient, the dielectric breakdown voltage is improved by 1.5 times or more as compared to the case where the film is not formed. It was possible.

  While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

  100, 200: vacuum valve, 101: vacuum insulating container, 102: fixed electrode, 103: movable electrode, 104: fixed conductive shaft, 105: movable conductive shaft, 106: arc shield 107, 108: flange, 109: bellows, 110, 111: electric field relaxation shield, 112: metalized layer, 113: low secondary electron emission coefficient layer, 201: solid insulator layer, 202: ...... Ground potential layer, 301: primary electron, 302: secondary electron.

Claims (7)

A cylindrical vacuum insulating container made of ceramic and having openings at both ends;
A pair of electrodes housed in the vacuum insulating container and capable of coming and going together;
Lids that close the openings at both ends of the vacuum insulation container;
A low secondary electron emission coefficient layer formed on inner wall surfaces of both ends of the vacuum insulation container and made of a material having a secondary electron emission coefficient lower than that of the ceramic;
The vacuum valve characterized by having. An electric field relaxation shield disposed so as to face the inner wall surfaces of both ends of the vacuum insulation container, wherein the low secondary electron emission coefficient layer is disposed at least at a portion facing the electric field relaxation shield The vacuum valve according to claim 1. Each of the low secondary electron emission coefficient layers is characterized in that the length along the axial direction of the vacuum insulation container is formed within a range of 10% or less with respect to the entire length of the vacuum insulation container. The vacuum valve according to claim 1 or 2. A metallized layer for connection to the lid is formed on the end surfaces of both ends of the vacuum insulation container, and the low secondary electron emission coefficient layer is also formed on the inner side surface of the metallized layer. The vacuum valve according to any one of claims 1 to 3, wherein The material having a secondary electron emission coefficient lower than that of the ceramic is any one of V, Cr, C, Fe, SiC, Cu, Mo, TiN, and Cr ₂ O ₃ . The vacuum valve according to item 1. The low secondary electron emission coefficient layer is discontinuously formed on the inner wall surface of the vacuum insulating container at intervals in the axial direction of the vacuum insulating container. 5. A vacuum valve according to any one of the preceding claims. A solid insulator layer covering the periphery of the vacuum insulation container;
A ground potential layer disposed around the solid insulator layer and connected to the ground potential;
The vacuum valve according to any one of claims 1 to 6, further comprising:

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