Switchgear

Abstract

The switchgear (100) comprises a tank (10) filled with gas, a vacuum circuit breaker (20) including a vacuum valve (20B), a fixed-side connecting conductor (5), a fixed-side support insulator (29) that electrically insulates the fixed-side connecting conductor (5) from the tank (10), and a fixing plate (30) that is fixed to the tank (10) perpendicular to the axial direction (Z) of the tank (10) and fixes the fixed-side end of the vacuum circuit breaker (20). The part (29) is fixed to the fixed side support insulating part (29) and has a threaded rod (40A) protruding outward in the axial direction (Z), the fixing plate (30) has three first through holes (30H) whose inner diameter (R1) is larger than the outer diameter (R2) of the threaded rod (40A), and the vacuum circuit breaker (20) is fixed to the fixing plate (30) by nuts (N, N3) that screw onto the threaded rod (40A) that is passed through the first through holes (30H).

Description

[Technical Field]

[0001] The present disclosure relates to a switching device. [Background technology]

[0002] Switchgear stores devices such as vacuum circuit breakers inside a tank, and fills it with SF6 gas, which has excellent insulating properties, thereby shortening the insulation distance and reducing the overall dimensions of the device.In recent years, in consideration of the impact on the environment, insulating gases are sometimes changed from SF6 gas to gases with a lower environmental impact (for example, gases with a lower global warming potential).

[0003] When using gases with a low environmental impact, increasing the gas pressure inside the tank improves insulation performance, making it possible to achieve a housing size equivalent to that of SF6 gas, which has excellent insulation performance.To increase the gas pressure, a commonly used method is to make the tank cylindrical, which has a structure that is strong against pressure.

[0004] On the other hand, fixing a circuit breaker to the inner surface of a tank is more difficult than fixing it to a rectangular tank because the inner surface of the tank is curved. In Patent Document 1, each phase of the vacuum circuit breaker is fixed by an insulator extending horizontally from the tank. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-81697 Summary of the Invention [Problem to be solved by the invention]

[0006] The circuit breaker fixing method described in Patent Document 1 requires the circuit breakers to be arranged in parallel. Arranging the circuit breakers in a straight line in a high-pressure cylindrical tank results in wasted space, requiring the tank itself to be larger. Therefore, to reduce the size of the switchgear in the radial direction of the cylindrical tank, it is preferable to arrange three circuit breakers in a triangular configuration and fix them at the top and bottom of the circuit breakers. In this case, fixing the circuit breakers to the tank at the top is simple, as all three phases are fixed to the tank via a fixing plate. However, correcting the tolerances of the three phase components of a vacuum circuit breaker at the fixing parts places a load on the vacuum valve, which is an issue.

[0007] The present disclosure discloses a technique for solving the above-described problems, and aims to provide a switchgear that can be fixed inside a tank while accommodating the tolerances of components without applying a load to multiple vacuum circuit breakers. [Means for solving the problem]

[0008] The opening and closing device according to the present disclosure comprises: a tank filled with gas; a three-phase vacuum circuit breaker including a vacuum valve provided inside the tank, a fixed-side connecting conductor connected to the vacuum valve, and a fixed-side supporting insulator that electrically insulates the fixed-side connecting conductor from the tank; a fixing plate that is fixed to the tank perpendicular to an axial direction of the tank and that fixes fixed side ends of the three-phase vacuum circuit breakers, the fixed-side support insulator has a threaded rod fixed to the fixed-side support insulator and protruding outward in the axial direction, the fixing plate has three first through holes each having an inner diameter larger than an outer diameter of the threaded rod; the vacuum circuit breakers for three phases are fixed to the fixing plate by nuts threaded onto the threaded rods passed through the first through holes, The nut is a flat nut having an outer diameter larger than an inner diameter of the first through hole, a presser plate that sandwiches and fixes the flat nut between the presser plate and the fixing plate from the outside in the axial direction, The presser plate has a second through hole having an inner diameter larger than the outer diameter of the threaded rod. It is something. [Effects of the Invention]

[0009] The switchgear according to the present disclosure can easily accommodate tolerances in the axial direction and in the direction perpendicular to the axial direction of the vacuum circuit breaker that occur during assembly of the vacuum circuit breaker, thereby accommodating the tolerances of the components and fixing them in the tank without applying a load to multiple vacuum circuit breakers. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a switching device according to a first embodiment. [Figure 2] FIG. 2 is a view taken along the arrow AA in FIG. [Figure 3] FIG. 2 is an enlarged view of a main part of FIG. [Figure 4] FIG. 4 is a further enlarged view of the area surrounded by the dashed line in FIG. 3. [Figure 5] 10 is a view of an end fixing portion of a vacuum circuit breaker according to a second embodiment, viewed from the outside in the axial direction Z. FIG. [Figure 6] FIG. 6 is an enlarged view of a main part of FIG. 5. [Figure 7] FIG. 6 is a further enlarged view of the area surrounded by the dashed line in FIG. 5. [Figure 8] 11 is a view of an end fixing portion of a vacuum circuit breaker according to a third embodiment, viewed from the outside in the axial direction Z. FIG. [Figure 9] 11 is a view of an end fixing portion of a vacuum circuit breaker according to a third embodiment, viewed from the outside in the axial direction Z. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiment 1 The opening and closing device according to the first embodiment will be described below with reference to the drawings. In this specification, the axial direction of the cylindrical tank of the switchgear is referred to as the axial direction Z, the center side of the cylindrical tank is referred to as the inside, and the opposite side is referred to as the outside. Also, the lower side of the paper in Figure 1, i.e., the movable electrode side, is referred to as the movable side Z+, and the upper side of the paper, i.e., the fixed electrode side, is referred to as the fixed side Z-.

[0012] Furthermore, the drawings used are schematic illustrations, and the relative sizes and positions shown in different drawings are not necessarily limited to those described and may be changed as appropriate. Furthermore, in the following description, similar components are illustrated with the same reference numerals (or the same last two digits), and their names and functions are also the same or similar. Therefore, detailed descriptions thereof may be omitted.

[0013] FIG. 1 is a cross-sectional view of a switching device 100. As shown in FIG. Fig. 2 is a view taken along the line AA in Fig. 1, showing the fixing portion at the end of the vacuum circuit breaker as seen from the outside in the axial direction Z. FIG. 3 is an enlarged view of a main part of FIG. FIG. 4 is a further enlarged view of the area enclosed by the dashed line in FIG. The switchgear 100 shown in FIG. 1 is a gas-insulated switchgear. The switching device 100 comprises a cylindrical tank 10, a first lid 11 that closes the opening at one end (fixed side Z-) of the cylindrical tank 10, a second lid 12 that closes the opening at the other end (movable side Z+) of the cylindrical tank 10, three vacuum circuit breakers 20, one for each phase of the three-phase AC, movable side bus conductors 4 connected to each vacuum circuit breaker 20, fixed side bus conductors 5 connected to each vacuum circuit breaker 20, and a fixing plate 30 that fixes the fixed side Z- ends of the three vacuum circuit breakers 20 inside the cylindrical tank 10.

[0014] The opening and closing device 100 does not need to have the movable side Z+ arranged in the direction of gravity, and the fixed side Z- may be arranged in the direction of gravity. The opening and closing device 100 may also be arranged so that the movable side Z+ and the fixed side Z- extend in the horizontal direction. An operating unit 17, for example, not shown in detail, is provided at the end of the link portion R of the movable side Z+ of the opening and closing device 100.

[0015] As shown in Fig. 1, a movable bus conductor 4, a fixed bus conductor 5, a vacuum circuit breaker 20, and a fixed plate 30 are housed in a cylindrical tank 10 with both ends closed. Note that the movable bus conductor 4, the fixed bus conductor 5, and the vacuum circuit breaker 20 may be provided with portions exposed from the cylindrical tank 10. The cylindrical tank 10 is grounded.

[0016] The first lid 11 and the second lid 12 are provided on the outside of the cylindrical tank 10, but may be fitted inside the cylindrical tank 10.

[0017] The second lid 12 has a through hole 12H through which the connection portion 20S of the vacuum circuit breaker 20 passes.

[0018] The inner flange 13 is provided inside the cylindrical tank 10. The inner flange 13 is a necessary component for the pressure structure of the switchgear 100. The inner flange 13 is provided on the fixed side Z- relative to the second lid 12. The inner flange 13 is provided on the movable side Z+ relative to the movable side fixed insulating cylinder 21 in the vacuum circuit breaker 20. The inner flange 13 is provided between the second lid 12 and the movable side fixed insulating cylinder 21. The inner flange 13 is provided in partial contact with the second lid 12. The inner flange 13 has a through hole 13H. The insulating rod 22 of the vacuum circuit breaker 20 is passed through the through hole 13H of the inner flange 13.

[0019] The vacuum circuit breaker 20 includes an operating unit 17, a link unit R, a connecting unit 20S, a movable-side fixed insulating cylinder 21, an insulating rod 22, a movable-side cylinder conductor 23, a vacuum valve 20B equipped with contacts 24, a movable electrode rod 25A, a fixed electrode rod 25B, and a bellows 27 for ensuring electrical continuity even when the switching mechanism operates, a fixed-side connecting conductor 28 connected to the vacuum valve 20B, and a fixed-side supporting insulator 29. The fixed-side supporting insulator 29 electrically insulates the fixed-side connecting conductor 28 from the cylindrical tank 10. A full screw 40A (threaded rod) for fixing the vacuum circuit breaker 20 in the cylindrical tank 10 is fixed to the fixed-side supporting insulator 29 so as to protrude outward in the axial direction Z.

[0020] The above-mentioned operating unit 17 is provided on the movable side Z+ of the vacuum circuit breaker 20. The operating unit 17 is indirectly connected to the insulating rod 22, for example, via a link portion R and a connecting portion 20S. As the operating unit 17 moves, the movable electrode rod 25A of the vacuum interrupter 20B moves via the insulating rod 22.

[0021] The fixed-side connecting conductor 28 and the fixed-side supporting insulator 29 of the vacuum circuit breaker 20 are connected by a full-threaded screw 40B, which allows the position of the fixed-side supporting insulator 29 in the Z direction to be adjusted. Furthermore, the above-mentioned full-threaded screw 40A is attached to the top of the fixed-side supporting insulator 29.

[0022] 2, 3, and 4, a fixing plate 30 is installed on the top of the cylindrical tank 10 to fix the fixed side Z- ends of the three-phase vacuum circuit breakers 20 to the cylindrical tank 10. The fixing plate 30 is fixed with bolts 50 to a fixing portion 10K extending radially inward from the inner surface of the cylindrical tank 10. The fixing plate 30 is fixed perpendicular to the axial direction Z of the cylindrical tank 10. The fixing plate 30 may be formed as a separate part. The fixing plate 30 has three through holes 30H (first through holes) that penetrate in the Z direction. Connecting the centers of the three through holes 30H forms a roughly equilateral triangle.

[0023] Next, a method for fixing the three vacuum circuit breakers 20, which have been temporarily placed in the cylindrical tank 10 by fitting the end of the movable side Z+ into the second lid 12, in the cylindrical tank 10 will be described. After the three vacuum circuit breakers 20 are temporarily placed inside the cylindrical tank 10, the fixing plate 30 is fixed to the fixing portion 10K of the cylindrical tank 10 with bolts 50. Next, a fully threaded screw 40A is passed through a through hole 30H provided in the fixing plate 30 so as to penetrate in the Z direction. After the fully threaded screw 40A is passed through the through hole 30H, the members for fixing the vacuum circuit breakers 20 to the fixing plate 30 are attached in the following order from the end of the fully threaded screw 40A on the Z+ side. First, the washer W1 shown in FIG. 4 is passed through. Next, the nut N1 is screwed onto the fully threaded screw 40A from the end on the Z+ side. Next, the nut N2 is screwed in the same way. Next, the washer W2 is passed through.

[0024] Next, the fully threaded screw 40A is screwed into the fixing hole 29H provided in the fixed-side support insulator 29. Next, the nut N2 is tightened to securely fix the fully threaded screw 40A in the fixing hole 29H. Next, the nut N1 is rotated to align the washer W1 with the position where it just abuts against the fixed plate 30. This completes the installation of the fixture to be placed on the inside of the fixed plate 30 in the axial direction Z.

[0025] Next, a washer W3 is passed through the complete screw 40A protruding in the Z direction from the through-hole 30H of the fixing plate 30, and a nut N3 is screwed onto the complete screw 40A. 4, the inner diameter R1 of the through hole 30H of the fixing plate 30 is larger than the outer diameter R2 of the fully threaded thread 40A. Therefore, a gap S exists between the inner peripheral surface of the through hole 30H and the outer peripheral surface of the fully threaded thread 40A.

[0026] Additionally, the outer diameter R3 of the washers W1 and W3 is larger than the inner diameter R1 of the through-hole 30H. This allows fine adjustment of the position of the vacuum circuit breaker 20 in the direction perpendicular to the axial direction Z before tightening the nuts N3 to completely secure the vacuum circuit breaker 20 to the cylindrical tank 10. Thereafter, by tightening the nuts N3, the vacuum circuit breaker 20 can be finally secured to the fixing plate 30 from both sides in the axial direction Z by the nuts N1 and N3.

[0027] By repeating the above steps, three phases of vacuum circuit breakers 20 can be fixed in the cylindrical tank 10 via the fixing plates 30. The positioning of the Z+ side of the vacuum circuit breaker 20 is determined by the through-hole 13H of the inner flange 13 and the through-hole 12H of the second lid 12. Each of the nut and washer sets may be a countersunk nut in which the nut and washer are integrated. Furthermore, although the tank has been described as a cylindrical tank 10, a rectangular parallelepiped tank may also be used.

[0028] According to the opening and closing device 100 according to the first embodiment, a tank filled with gas; a three-phase vacuum circuit breaker including a vacuum valve provided inside the tank, a fixed-side connecting conductor connected to the vacuum valve, and a fixed-side supporting insulator that electrically insulates the fixed-side connecting conductor from the tank; a fixing plate that is fixed to the tank perpendicular to an axial direction of the tank and that fixes fixed side ends of the three-phase vacuum circuit breakers, the fixed-side support insulator has a threaded rod fixed to the fixed-side support insulator and protruding outward in the axial direction, the fixing plate has three first through holes each having an inner diameter larger than an outer diameter of the threaded rod; The three-phase vacuum circuit breakers are fixed to the fixing plate by nuts that are threaded onto the threaded rods that are passed through the first through holes, The vacuum circuit breaker 20 and the fixed plate 30 are fixed to each other using a full screw 40A that is fixed to the fixed side support insulator 29 and protrudes in the axial direction Z, and a nut N, so that the tolerance in the axial direction Z of the vacuum circuit breaker 20 that occurs when assembling the vacuum circuit breaker 20 can be absorbed. Furthermore, because there is a gap S between the inner peripheral surface of the through-hole 30H in the fixing plate 30 and the outer peripheral surface of the fully threaded screw 40A, the position of the vacuum circuit breaker 20 can also be adjusted in the direction perpendicular to the axial direction Z of the fully threaded screw 40A, thereby absorbing horizontal tolerances that occur when assembling the vacuum circuit breaker 20. With this configuration, the three-phase vacuum circuit breakers 20 can be fixed accurately within the cylindrical tank 10 regardless of the assembly tolerances of the vacuum circuit breakers 20.

[0029] Also, The three-phase vacuum circuit breakers are each fixed to the fixing plate from both sides in the axial direction by a pair of nuts that are screwed onto the threaded rods that are passed through the first through holes, The vacuum circuit breaker can be securely fixed to the tank.

[0030] The nut is a countersunk nut with an outer diameter larger than the inner diameter of the first through hole, The number of parts can be reduced.

[0031] Also, A washer having an outer diameter larger than the inner diameter of the first through hole is provided between the nut and the fixing plate, so that the gap S can be used effectively.

[0032] Embodiment 2 The opening and closing device according to the second embodiment will be described below, focusing on the differences from the first embodiment. FIG. 5 corresponds to FIG. 2 of the first embodiment, and is a view of the end fixing portion of the vacuum circuit breaker 20 as viewed from the outside in the axial direction Z. FIG. 6 is an enlarged view of the main part of FIG. FIG. 7 is a further enlarged view of the area enclosed by the dashed line in FIG. Description will be omitted for configurations similar to those of embodiment 1. A switchgear 200 according to embodiment 2 differs from the switchgear 100 described in embodiment 1 in the method of connecting the fixing plate 230 and the vacuum circuit breaker 20.

[0033] In the second embodiment, only the washer W2 and nut N2 that secure the fully threaded screw 40A to the fixed-side support insulator 29 are located inside the fixed plate 230 in the axial direction Z; the washer W1 and nut N1 used in the first embodiment are not used. On the other hand, a flat nut N4 having an outer diameter R4 larger than the inner diameter R1 of the through hole 230H (first through hole) is screwed onto the fully threaded screw 40A on the outer side of the fixed plate 230 in the axial direction Z. A presser plate 33 having a through hole 33H (second through hole) with an inner diameter R5 larger than the outer diameter R2 of the fully threaded screw 40A is provided on the flat nut N4. The presser plate 33 is fixed to the fixed plate 230 with four screws SC. Therefore, a gap S2 exists between the inner circumferential surface of the through hole 33H and the outer circumferential surface of the fully threaded screw 40A.

[0034] As in the first embodiment, the inner diameter R1 of the through-hole 230H of the fixing plate 230 is larger than the outer diameter R2 of the fully threaded portion 40A. Therefore, a gap S exists between the inner peripheral surface of the through-hole 230H and the outer peripheral surface of the fully threaded portion 40A.

[0035] Next, a method for fixing the vacuum circuit breaker 20, which has been temporarily placed in the cylindrical tank 10 by fitting the end of the movable side Z+ in the axial direction Z into the second lid 12, in the cylindrical tank 10 will be described. Once the three vacuum circuit breakers 20 have been temporarily placed inside the cylindrical tank 10, the fixing plate 230 is fixed to the fixing portion 10K of the cylindrical tank 10 with bolts 50. Next, the fully threaded screw 40A is passed through the through hole 230H provided in the fixing plate 230 so as to penetrate in the axial direction Z. After the fully threaded screw 40A has been passed through the through hole 230H, the fixing members are attached from the inside of the fully threaded screw 40A in the axial direction Z in the following order: First, the nut N2 is screwed into the end of the fully threaded screw 40A on the inside in the Z direction. Next, the washer W2 is passed through.

[0036] Next, the fully threaded screw 40A is screwed into the fixing hole 29H provided in the fixed-side support insulator 29. Next, the nut N2 is tightened to fix the fully threaded screw 40A into the fixing hole 29H. Next, the flat nut N4 is screwed onto the fully threaded screw 40A from the outside in the Z direction of the fixed plate 230. Once the flat nut N4 abuts against the outer surface of the fixed plate 230 in the Z direction, the pressing plate 33 is placed over the flat nut N4, sandwiching it between the fixing plate 230 and the flat nut N4, and the pressing plate 33 is fixed to the fixed plate 230 with four screws SC.

[0037] Furthermore, if necessary, the vacuum circuit breaker 20 can be more firmly fixed to the fixing plate 230 by screwing the nut N3 (second nut) onto the fully threaded portion 40A and tightening it. In this case, the inner diameter R5 of the through hole 33H of the holding plate 33 needs to be larger than the outer diameter R6 of the nut N3.

[0038] According to the opening and closing device according to the second embodiment, The nut is a flat nut having an outer diameter larger than an inner diameter of the first through hole, a presser plate that sandwiches and fixes the flat nut between the presser plate and the fixing plate from the outside in the axial direction, The presser plate has a second through hole having an inner diameter larger than an outer diameter of the threaded rod, As in embodiment 1, the vacuum circuit breaker 20 and the fixed plate 230 are fixed to each other using a full-threaded screw 40A that is fixed to the fixed side support insulator 29 and protrudes in the axial direction Z, thereby absorbing the tolerance in the axial direction Z of the vacuum circuit breaker 20 that occurs when assembling the vacuum circuit breaker 20.

[0039] Furthermore, the position of the vacuum circuit breaker 20 perpendicular to the axial direction can be adjusted by utilizing the gap S formed between the inner surface of the through hole 230H of the fixing plate 230 and the outer surface of the fully threaded thread 40A, and the gap S2 formed between the inner surface of the through hole 33H of the pressure plate 33 and the outer surface of the fully threaded thread 40A, and then the vacuum circuit breaker 20 can be fixed by the pressure plate 33, so that the vacuum circuit breaker 20 can be fixed in the desired position regardless of the tolerance of the vacuum circuit breaker 20.

[0040] Furthermore, in embodiment 1, it was necessary to rotate nut N2 to position it in the axial direction Z before tightening nut N3, but in this embodiment, the positioning and fixing of the vacuum circuit breaker 20 can be performed from outside the axial direction Z of the fixing plate 230, so that work can be done efficiently even when the gap between the vacuum circuit breaker 20 and the fixing plate 230 is narrow, and the overall length of the switching device in the axial direction Z can be reduced.

[0041] Also, Since a second nut is provided that is screwed onto the threaded rod and presses the nut against the fixing plate, the vacuum circuit breaker (20) can be reliably fixed to the tank via the fixing plate (30).

[0042] Embodiment 3 The opening and closing device 300 according to the third embodiment will be described below, focusing on the differences from the first embodiment. 8 corresponds to FIG. 2 of the first embodiment, and is a view of the end fixing portion of the vacuum circuit breaker 20 as seen from the outside in the axial direction Z. The configuration for fixing the vacuum circuit breaker 20 is the same as that of the first embodiment.

[0043] The difference between the third embodiment and the first embodiment is the shape of the fixing plate 330. As shown in Fig. 8, the three vacuum circuit breakers 20 are arranged in a cylindrical tank 10 having a circular cross section so that, when viewed from the outside in the axial direction Z, a line connecting their centers forms a roughly equilateral triangle. Therefore, a U-shaped fixing plate 330 is used, in which a portion not necessary for fixing the cylindrical tank 10 is cut out. The notch 330K is provided between the two through holes 30H. Providing the notch 330K ensures a wide working space from the outside in the axial direction Z of the cylindrical tank 10, thereby improving the workability of assembling the switchgear 300.

[0044] 9 corresponds to the fixing method of the second embodiment and is a view of the end fixing portion of the vacuum circuit breaker 20 as seen from the outside in the axial direction Z. The configuration for fixing the vacuum circuit breaker 20 is the same as that of the second embodiment. As shown in FIG. 9, even in the case of the fixing plate 330 using the fixing structure described in the second embodiment, the workability of assembling the switchgear 300 can be improved by providing a notch 330K between the two through holes 230H.

[0045] According to the opening and closing device of the third embodiment, The fixing plate has a notch between the two first through holes, A wide working space can be secured from the outside of the cylindrical tank 10 in the axial direction Z, and the workability of assembling the opening and closing device 300 can be improved.

[0046] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not exemplified are conceivable within the scope of the technology disclosed in this specification, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with components of another embodiment. [Explanation of symbols]

[0047] 100, 200, 300 Switchgear, 10 Cylindrical tank, 10K Fixed part, 11 First cover, 12 Second cover, 12H Through hole, 13 Inner flange, 13H Through hole, 17 Operating part, 20 Vacuum circuit breaker, 20B Vacuum valve, 20S Connection part, 21 Movable side fixed insulating tube, 22 Insulating rod, 23 Movable side cylinder conductor, 24 Contact, 25A Movable electrode rod, 25B Fixed electrode rod, 27 Bellows, 28 Fixed side connecting conductor, 29 Fixed side support insulating part, 29H Fixing hole, 30, 230, 330 Fixing plate, 230H Through hole, 30H Through hole, 33 Pressing plate, 330K Notch, 33H Through hole, 4 Movable side busbar conductor, 40A, 40B Fully threaded, 5 Fixed side busbar conductor, 50 Bolt, N, N1, N2, N3 nut, N4 flat nut, R link part, R1, R5 inner diameter, R2, R3, R4, R6 outer diameter, S, S2 gap, SC screw, W1, W2, W3 washer, Z axis direction, Z+ movable side, Z- fixed side.

Claims

1. a tank filled with gas; a three-phase vacuum circuit breaker including a vacuum valve provided inside the tank, a fixed-side connecting conductor connected to the vacuum valve, and a fixed-side supporting insulator that electrically insulates the fixed-side connecting conductor from the tank; a fixing plate that is fixed to the tank perpendicular to an axial direction of the tank and that fixes fixed side ends of the vacuum circuit breakers for the three phases, the fixed-side support insulator has a threaded rod fixed to the fixed-side support insulator and protruding outward in the axial direction, the fixing plate has three first through holes each having an inner diameter larger than an outer diameter of the threaded rod; the vacuum circuit breakers for three phases are fixed to the fixing plate by nuts threaded onto the threaded rods passed through the first through holes, the nut is a flat nut having an outer diameter larger than an inner diameter of the first through hole, a presser plate that sandwiches and fixes the flat nut between the presser plate and the fixing plate from the outside in the axial direction, The pressing plate has a second through hole having an inner diameter larger than the outer diameter of the threaded rod.

2. The opening and closing device according to claim 1 , further comprising a second nut that is threaded onto the threaded rod and presses the flat nut against the fixed plate.

3. The opening and closing device according to claim 1 or 2, wherein the fixing plate has a notch between the two first through holes.

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