JPH10210614A - Gas insulation electric apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas insulation electric apparatus which can omit equipartitioning conversion flange, when an insulation spacer which gas-divides two vessels is connected with one of the vessels by using a pressing board. SOLUTION: A surface of the fixing part 601a of an insulation spacer 6 is made to abut against a fixing board 4 installed in a first vessel 1. A surface of a pressing board 7 is made to abut against the other surface of the fixing part 601a. A flange 2a of a second vessel 2 is made to abut against the other surface of the pressing board 7. A stud bolt, which penetrates the flange 2a, the pressing board 7 and the fixing part 601a, is screwed in a threaded hole 401 formed in the fixing board 4. The pressing board 7 is fastened to the fixing board 4 by a first nut 21 screwed to the stud bolt 20. The flange 2a is fastened to the pressing board 7, by using a nut 22 screwed to the stud bolt 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas-insulated electric device such as a gas-insulated switchgear.

[0002]

2. Description of the Related Art In gas-insulated electrical equipment, components of the electrical equipment may be housed in a plurality of containers, and the plurality of containers may be connected in a gas-separated state via insulating spacers. Many.

FIGS. 4 and 5 show an example of a connection structure of a container, which is employed in a conventional gas insulated switchgear, in a connection portion between a gas insulated VT container and another container of the gas insulated switchgear. In these figures, reference numeral 1 denotes a first container containing a gas-insulated VT transformer main body, and reference numeral 2 denotes a component of a switching circuit of a portion to which the VT is connected. This is a second container. FIG.
As shown in FIG. 1, the first container 1 has an opening provided with a flange 1a, and a packing 3 is provided on the flange 1a of the opening.
The ring-shaped mounting plate 4 is in contact with the base plate through the base plate. The mounting plate 4 is fastened to the flange 1 a by bolts 5 and is airtightly connected to the first container 1. The mounting plate 4 is provided with a plurality of screw holes 401 at equal intervals in the circumferential direction of the mounting plate.

[0004] An insulating spacer 6 is connected to the mounting plate 4. The insulating spacer 6 is made of an insulating material, has a flange-shaped mounting portion 601a at a portion near the outer periphery, and has one conductor supporting portion 601b formed in a cone shape at a portion inside the mounting portion 601a. Or four spacer main bodies 601 and conductor supporting portions 6 of the spacer main body 601.
Embedded conductor 6 of each phase provided in a state penetrating through
02. The mounting portion 601a has a plurality of mounting holes 603 that penetrate the mounting portion 601a in the axial direction.
The holes are formed at equal intervals in the circumferential direction so as to be aligned with the screw holes 401 of the mounting plate 4 respectively.

[0005] The insulating spacer 6 is arranged with the conical conductor supporting portion 601 b protruding outside the container 1, and one axial end face 601 a 1 of the mounting portion 601 a contacts the mounting plate 4. Touched.

[0006] One axial end face 7a of an annular holding plate 7 is in contact with the other axial end face 601a2 of the mounting portion 601a of the insulating spacer 6. As can be seen in FIG. 4, the holding plate 7 is
A plurality of mounting holes 701 aligned with the plurality of mounting holes 603 provided in 1a, and a screw hole 702 between the plurality of mounting holes 701 and opened only on the other axial end face 7b side of the holding plate 7. Have.

[0007] The holding plate 7 is attached to the mounting plate 4 by bolts 8 screwed into the screw holes 401 of the mounting plate 4 through a plurality of mounting holes 701 provided in the holding plate and the mounting holes 603 of the insulating spacer. Has been concluded. Mounting hole 701 of holding plate 7
A recess for accommodating the head 8a of the bolt 8 is formed in the opening, so that the head of the bolt does not project outside when the holding plate 7 is fastened by the bolt 8. I have.

On the other axial end face 7b of the holding plate 7,
A flange 2 a provided at the opening of the second container 2 is in contact with an equi-distribution conversion flange 9 formed in an annular shape. As shown in FIG. 4, the equally-distributed conversion flange 9 includes a plurality of mounting holes 901 respectively corresponding to the plurality of screw holes 702 of the holding plate 7, and is located between the mounting holes 901 and on the second container 2 side. And a plurality of screw holes 902 that are opened only through the mounting holes 901 so that the screw holes 7
It is fastened to the holding plate 7 by a bolt 10 (see FIG. 4) screwed into the cover 02. At the opening of the mounting hole 901, a recess for accommodating the head of the bolt 10 so as not to protrude is formed.

A plurality of mounting holes 201 are formed in the flange 2a of the second container 2 so as to be aligned with the plurality of screw holes 902 of the equally-distributed conversion flange 9, respectively.
Through the screw holes 90 of the equally-distributed conversion flange 9.
The flange 2 a is fastened to the equally-distributed conversion flange 9 by a bolt 11 screwed into the flange 2.

[0010] Between the mounting portion 601a of the insulating spacer 2 and the mounting plate 4, between the holding plate 7 and the mounting portion 601a of the insulating spacer 2.
, Between the equally-distributed conversion flange 9 and the holding plate 7, and between the flange 2a of the second container 2 and the equally-distributed conversion flange 9, respectively. The airtightness of these joints is maintained.

An end of each buried conductor 602 provided in the insulating spacer 6 in the container 1 is connected to a connection conductor 13 connected to the primary side of the VT main body. First container 1
The SF ₆ gas is sealed in the second container 2 at a predetermined pressure.

In the gas-insulated electrical equipment shown in FIGS. 4 and 5, when inspecting the equipment in the second container 2, the gas in the container 2 is first recovered, and then the bolt 11 is removed. Remove the container 2. At this time, the insulating spacer 6
Is kept attached to the container 1 side of the second container 2 without collecting the gas in the first container 1.
Inside can be checked.

As described above, the insulating spacer 6 is fixed to the holding plate 7.
In the case of mounting using an insulating spacer, the mounting hole 603 provided in the insulating spacer 6 is used for fixing the insulating spacer 6 to the first container 1 by the holding plate 7. Therefore, in order to connect the second container 2, it is necessary to provide the screw hole 702 in the holding plate 7. However, the flange of the second container 2 is directly fastened to the screw hole 702 provided in the holding plate 7. Then, the mounting holes 201 provided in the flange 2 a of the second container 2 are arranged in the mounting holes 603 provided in the insulating spacer 6.
It must be different from the arrangement. It is not preferable that the arrangement of the mounting holes at a specific location is different from that at other locations, because a misunderstanding occurs when assembling the apparatus.
Therefore, in the above example, the arrangement of the mounting holes 201 provided in the flange 2a of the second container 2 is changed by changing the arrangement of the mounting holes by using the equally-distributed conversion flanges 9 so that the other containers of the gas insulated switchgear are used. And the arrangement of the mounting holes provided at the connection points.

FIGS. 6 and 7 show another connection structure employed when a gas-insulated VT is connected to a predetermined portion of a conventional gas-insulated switchgear. In this example, the mounting plate 4 attached to the opening of the first container 1 is formed sufficiently thick.
A plurality of screw holes 401 opened only inside the container 1 and a plurality of screw holes 402 opened only outside the container 1 are provided. The insulating spacer 6 is disposed in the container 1, and its mounting portion 601 a is in contact with the mounting plate 4, and the mounting portion 601 a
The insulating spacer 6 is fastened to the mounting plate 4 by screwing the bolt 8 having passed through the mounting hole 603 provided in the mounting plate 4 into the screw hole 401 of the mounting plate 4. The flange 2 a of the second container 2 is in contact with an end surface of the mounting plate 4 located outside the container 1, and is fastened to the mounting plate 4 by bolts 11.

FIGS. 8 and 9 show still another connection structure employed in the conventional gas insulated switchgear when a gas insulated VT is connected to a predetermined portion of the switchgear. In this example, FIG. One end of the short pipe 14 is welded to the inner periphery of the mounting plate 4 attached to the opening of the first container 1, and a flange plate 15 is welded to the other end of the short pipe 14. And
One end of the mounting portion 601 a of the insulating spacer 6 in the axial direction is brought into contact with the flange plate 15, and the mounting portion 601 a
a on the other axial end face of the second container 2
The nut 17 is inserted into the stud bolt 16 through which the mounting hole 201 provided in the flange 2a, the mounting hole 603 provided in the mounting portion 601a, and the hole provided in the flange plate 15 penetrate.
And 18, the insulating spacer 6 is connected to the containers 1 and 2.

[0016]

The connection structure shown in FIGS. 4 and 5 requires an equal distribution conversion flange 9 in addition to the holding plate 7, so that the number of parts is increased and the structure of the connection portion is complicated. And the need to maintain airtightness increases,
There was a problem that the cost was high. In addition, since the number of parts is large and the structure is complicated, there is also a problem that the connecting portion becomes large and its weight increases.

In the connection structure shown in FIGS. 6 and 7, it is necessary to increase the thickness of the mounting plate 4, so that the weight increases and the cost cannot be avoided. Also, screw holes 401 and 40 are provided at the same position of the mounting plate 4 from both sides thereof.
Since it is necessary to perform the processing of providing 2, the screw holes 401 and 402 may penetrate, which is not preferable.

Further, in the connection structure shown in FIGS. 8 and 9,
Since a short pipe 14 and a flange 15 are required in addition to the mounting plate 4, not only the number of parts is increased and the cost is increased, but also a large-sized bolt 5 is expensive as a bolt 5 in calculating the strength of the pressure vessel. There was a problem that it was necessary to use something.

An object of the present invention is to make it possible to connect the two containers via an insulating spacer with the same arrangement of the mounting holes of the first container and the second container, without using an equal distribution conversion flange. To provide a gas-insulated electrical device.

[0020]

According to the present invention, there is provided a first container having an annular mounting plate in an opening, and a flange plate-like mounting portion on an outer peripheral side, wherein one of the mounting portions is provided. An insulating spacer arranged with its axial end face in contact with the mounting plate, and an annular presser arranged with one axial end face in contact with the other axial end face of the mounting portion of the insulating spacer. A second container having a plate, an opening having a flange, the flange being in contact with the other axial end face of the holding plate, and a first fastening for fastening the holding plate to a mounting plate of the first container. Means, and second fastening means for fastening the flange of the second container to the holding plate, wherein the first container and the second container contain the components of the electric device and are filled with an insulating gas. Related to gas insulated electrical equipment.

In the present invention, one end is provided at a predetermined interval in the circumferential direction of the mounting portion of the insulating spacer so as to penetrate the mounting portion of the insulating spacer, the holding plate, and the flange of the second container. A plurality of stud bolts which are screwed into screw holes provided in the mounting plate of the first container and which are screwed to the respective stud bolts so that the head does not project to the flange side of the second container. A first nut whose head is housed in a recess provided in the holding plate and tightens the holding plate against a mounting plate provided in the first container; And a second nut for fastening the flange of the container to the holding plate. The stud bolt and the first nut constitute first fastening means, and the stud bolt and the second nut constitute second fastening means.

With the above construction, the mounting plate of the first container and the flange of the second container can be connected to each other through the insulating spacer by using only the holding plate without using the equal conversion flange. Therefore, the structure of the connecting portion of the container can be simplified. Also, the mounting plate provided at the opening of the first container only needs to be provided with a screw hole that opens on one side, so that the mounting plate can be prevented from becoming thick.

In the above configuration, in order to separate the second container from the insulating spacer, it is preferable that when the second nut is loosened, the stud bolts do not turn together and become loose. . For this purpose, for example, the outer diameter of the portion of the stud bolt that is screwed into the screw hole of the mounting plate is set to be larger than the outer diameter of the portion that is screwed into the second nut, and the stud bolt is inserted into the mounting hole. It is preferable that the tightening torque at the time of screwing into the screw hole is set to be larger than the tightening torque at the time of screwing the second nut to the stud bolt.

Also, the screw hole of the stud bolt mounting plate is set so that the friction coefficient of the portion screwed into the screw hole of the mounting plate is larger than the friction coefficient of the portion screwed into the second nut. By applying different surface treatments to the portion screwed to the second nut and the portion screwed to the second nut, the tightening torque for screwing the stud bolt into the screw hole of the mounting plate can be reduced. Can be made larger than the tightening torque at the time of screwing.

In order to prevent the stud bolt from rotating and loosening when the second nut is loosened in order to separate the second container from the insulating spacer, the stud bolt is screwed to the mounting plate. The difference between the tightening torque when screwing the second nut into the hole and the tightening torque when screwing the second nut into the stud bolt is 20% of the tightening torque when screwing the second nut into the stud bolt. It is preferable to set the above.

[0026]

1 and 2 show an embodiment of the present invention. In these figures, reference numeral 1 denotes a first container containing a main body of a gas-insulated VT, and 2 denotes a first container. This is a second container connected to the container 1 via an insulating spacer 6.

A flange 1a is provided at an opening of the first container 1, and an annular mounting plate 4 is in contact with the flange 1a via a packing 3. The mounting plate 4 is fastened to the flange 1 a by bolts 5. The mounting plate 4 is provided with a plurality of screw holes 401 at equal intervals in the circumferential direction.

The insulating spacer 6 has a flange-shaped mounting portion 601a on the outer peripheral portion, and one to four (four in the illustrated example) cone-shaped conductor supporting portions on the inner side of the mounting portion. A spacer main body 601 having a conductive body 601b and an embedded conductor 60 provided so as to penetrate each conductor supporting portion 601b
And 2. The mounting portion 601a of the insulating spacer 6 is equally spaced in the circumferential direction so that a plurality of mounting holes 603 passing through the mounting portion in the axial direction can be aligned with the plurality of screw holes 401 of the mounting plate 4, respectively. It is provided.

The insulating spacer 6 is disposed in a state where one axial end face 601a1 of the mounting portion 601a is in contact with the mounting plate 4 and the mounting hole 603 is aligned with the screw hole 401. An annular holding plate 7 is formed on the other axial end face 601a2 of the spacer mounting portion 601a.
Is in contact with one of the axial end faces 7a.

The holding plate 7 is provided with a plurality of mounting holes 701 respectively aligned with the plurality of mounting holes 603 of the insulating spacer, and the opening of each of the mounting holes 701 opened on the other axial end face 7 b side of the holding plate 7. By expanding the inside diameter of the part,
A recess 701a for accommodating the bolt head is formed.

The second container 2 has a flange 2 at its opening.
a, and the flange 2 a is in contact with the other axial end face 7 b of the holding plate 7. On the flange 2a,
A plurality of mounting holes 201 respectively corresponding to the plurality of mounting holes 701 of the holding plate 7 are provided, and the mounting holes 2 of the flange 2a are provided.
01, each mounting hole 701 of the holding plate 7, and each mounting hole 603 of the insulating spacer are passed through the stud bolt 2
0 is provided. The stud bolt 20 has a screw over its entire length, and one end of the stud bolt 20 is screwed into a screw hole 401 of the mounting plate 4.

A first nut 21 for fastening the holding plate 7 to the mounting plate 4 and a second nut 22 for fastening the flange 2 a of the second container 2 to the holding plate 7 are screwed to the stud bolt 20. Have been. The first nut 21 is housed in a recess 701a provided in the holding plate 7 so as not to protrude toward the flange 2a side of the second container 2, and holds the holding plate 7 to the first container 1.
To the mounting plate 4 provided in the above. Recess 701
“a” is formed in such a size that a tool for tightening the first nut 21 can be inserted.

The VT main body is housed in the first container 1, and the primary side of the VT main body is connected to the embedded conductor 602 provided on the insulating spacer 6 via the connection conductor 13. In the container 2, components of the gas insulated switchgear such as various switchgear and connection conductors are housed, and the embedded conductor in which the device in the container 2 and the VT in the container 1 are provided on the insulating spacer 6. Interconnected through 602. SF ₆ gas is sealed in the container 1 and the container 2 at a predetermined pressure.

In FIG. 1, reference numeral 25 denotes a support fitting for supporting the first container 1 on a support frame (not shown).
Reference numeral 6 denotes a terminal box attached to the bottom of the container 1 for storing a terminal drawn from the secondary side of the VT stored in the container 1.

As described above, the mounting hole 6 of the insulating spacer 6
03, the stud bolt 20 penetrating the mounting hole 701 of the holding plate 7 and the mounting hole 201 of the flange of the second container 2 is screwed into the screw hole 401 of the mounting plate 4 of the first container 1,
The holding plate 7 is fastened to the mounting plate by screwing the first nut 21 to the stud bolt, and the second container 2 is screwed to the second nut 22 by the stud bolt.
When the flange 2a is fastened to the holding plate 7, the arrangement of the mounting holes 401 on the first container 1 side and the arrangement of the mounting holes 201 on the second container side can be achieved without using an equal distribution conversion flange. In the same way, both containers can be connected via insulating spacers. Therefore, by reducing the number of parts,
The structure of the connecting portion of the containers 1 and 2 can be simplified,
The cost can be reduced, and the connecting portion can be reduced in size and weight.

Further, with the above configuration, when the mounting structure of the insulating spacer on the first container 1 side is changed to a system that does not use the holding plate 7 (when the gas insulation VT is changed in model). However, the mounting hole 20 on the second container 2 side
The arrangement of 1 does not need to be changed.

In the case of the above configuration, the second container 2
To separate the second nut 2 from the insulating spacer 6.
It is preferable to prevent the stud bolts 20 from rotating together when the bolts 2 are loosened. For this purpose, for example, as shown in FIG. 3, a stud bolt having a large-diameter portion 20a and a small-diameter portion 20b is used as the stud bolt 20, and the stud bolt 20 has a screw hole 4 in the mounting plate.
When the stud bolt 20 is screwed into the screw hole 401 of the mounting plate 4 by setting the outer diameter r1 of the portion screwed to the first nut 01 larger than the outer diameter r2 of the portion screwed to the second nut 22. It is preferable that the tightening torque τ1 is set to be larger than the tightening torque τ2 when the second nut 22 is screwed to the stud bolt 20.

Also, the stud bolt 20 has a coefficient of friction at a portion screwed into the screw hole 401 of the mounting plate 4 larger than a coefficient of friction at a portion screwed into the second nut 22. By applying different surface treatments to the portion screwed into the screw hole 401 of the mounting plate 4 and the portion screwed into the second nut 22, the stud bolt 20
Can be made greater than the tightening torque τ2 when screwing the second nut 22 to the stud bolt 20 when screwing the second nut 22 into the screw hole 401 of the mounting plate.

When a different surface treatment is applied to the stud bolt 20 as described above, the stud bolt 20 may have the same outer diameter over its entire length. May be used.

According to an experiment, the difference between the tightening torque τ1 for screwing the stud bolt 20 into the screw hole of the mounting plate and the tightening torque τ2 for screwing the second nut 22 to the stud bolt (τ1− τ2) with the stud bolt 2
Tightening torque τ when screwing the second nut 22 to 0
2 (τ1−τ2 ≧ 0.2τ2), when the second nut 22 is loosened to separate the second container 2 from the insulating spacer 6, the stud bolt 20 and the screw hole 401 It has been found that loosening of the threaded portion can be reliably prevented.

As described above, when a stepped bolt is used as the stud bolt 20, the first nut 21
The stud bolt may be screwed to either the large-diameter portion 20a or the small-diameter portion 20b. However, when the second nut 22 is loosened, the first nut 21 Is preferably screwed into the large diameter portion 20a.

Similarly, the mounting plate 4 of the stud bolt 20
The screw portion of the mounting plate 4 of the stud bolt 20 is screwed so that the friction coefficient of the screw portion of the stud bolt 20 is larger than the friction coefficient of the screw portion of the stud bolt 20. When a different surface treatment is applied to a portion to be screwed to the second nut 22, it is preferable that the first nut 21 is screwed to a portion where the friction coefficient of the stud bolt 20 is large.

In the above example, the portion for connecting the gas insulated VT in the gas insulated switchgear is taken as an example. However, it is necessary to connect the insulating spacer to one container (the first container) using a holding plate. Of course, the present invention can be applied to other connection points. Of course, the present invention can be applied to other gas-insulated electric devices other than the gas-insulated switchgear.

[0044]

As described above, according to the present invention, the stud bolt having the mounting hole of the insulating spacer, the mounting hole of the holding plate, and the mounting hole of the flange of the second container penetrates the first container. The first nut is screwed into the screw hole of the mounting plate, the first nut is screwed into the stud bolt, the holding plate is fastened to the mounting plate, and the second nut is screwed into the stud bolt. When the flange of the container is fastened to the holding plate, the arrangement of the mounting holes on the first container side and the arrangement of the mounting holes on the second container side are made the same without using the equal distribution conversion flange. The two containers can be connected via an insulating spacer. Therefore, there is an advantage that the structure of the connecting portion of the first and second containers can be simplified by reducing the number of components, and the cost can be reduced, and the connecting portion can be reduced in size and weight. is there.

In the present invention, the stud bolt
An outer diameter of a portion to be screwed into the screw hole of the mounting plate is set to be larger than an outer diameter of a portion to be screwed to the second nut, and a tightening torque for screwing the stud bolt into the screw hole of the mounting plate. Is set to be larger than the tightening torque when screwing the second nut to the stud bolt,
When the second nut is loosened to separate the second container from the insulating spacer, it is possible to prevent the stud bolt from rotating together and loosening. The stud bolt is screwed into the screw hole of the mounting plate of the stud bolt so that the friction coefficient of the portion screwed into the screw hole of the mounting plate is larger than the friction coefficient of the portion screwed to the second nut. The same effect can be obtained when different surface treatments are applied to the portion to be screwed and the portion to be screwed to the second nut.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration of a main part of an embodiment of the present invention, with a part thereof being stepped.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a perspective view showing a stud bolt suitable for use in the present invention.

FIG. 4 is an exploded perspective view showing a structure of a connection portion of a container adopted in a conventional gas insulated switchgear.

FIG. 5 is an enlarged cross-sectional view illustrating a structure of a main part of a connection unit illustrated in FIG. 4;

FIG. 6 is an exploded perspective view showing a structure of a connection portion of a container used in another conventional gas insulated switchgear.

FIG. 7 is an enlarged cross-sectional view illustrating a structure of a main part of a connection unit illustrated in FIG. 6;

FIG. 8 is an exploded perspective view showing a structure of a connection portion of a container employed in still another conventional gas insulated switchgear.

FIG. 9 is an enlarged cross-sectional view illustrating a structure of a main part of a connection unit illustrated in FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st container 2 2nd container 2a Flange 4 Mounting plate 6 Insulating spacer 603 Mounting hole 601a Mounting part 7 Holding plate 701 Mounting hole 701a Depression 20 Stud bolt 21 First nut 22 Second nut

Claims (4)

[Claims] 1. A first container having an annular mounting plate in an opening and a flange-shaped mounting portion on an outer peripheral side, and one axial end face of the mounting portion is attached to the mounting plate. It has an insulating spacer arranged in a contact state, an annular pressing plate arranged in a state where one axial end face is in contact with the other axial end face of the mounting portion of the insulating spacer, and a flange. A second container having an opening, the flange being in contact with the other axial end face of the holding plate, a first fastening means for fastening the holding plate to a mounting plate of the first container, A second fastening means for fastening a flange of the second container to the holding plate, wherein components of an electric device are housed in the first container and the second container and an insulating gas is sealed therein. In the gas-insulated electrical equipment, the circumferential direction of the mounting portion of the insulating spacer A screw hole provided at a predetermined interval and passing through the mounting portion of the insulating spacer, the holding plate, and the flange of the second container, and having one end provided in the mounting plate of the first container; A plurality of stud bolts which are screwed into and fixed to the stud bolts, and which are housed in recesses provided in the holding plate so as not to protrude to the flange side of the second container. A first nut for fastening the holding plate to an attachment plate provided on the first container; and a second nut screwed to each stud bolt and fastening the flange of the second container to the holding plate. A nut, wherein the stud bolt and the first nut constitute the first fastening means, and the stud bolt and the second nut constitute the second fastening means. Toss Gas-insulated electrical equipment. 2. An outer diameter of a portion of the stud bolt screwed into a screw hole of the mounting plate is set to be larger than an outer diameter of a portion screwed by a second nut, and the stud bolt is mounted. 2. The gas insulation according to claim 1, wherein a tightening torque at the time of screwing into the screw hole of the plate is set to be larger than a tightening torque at the time of screwing the second nut to the stud bolt. Electrical equipment. 3. A mounting plate for the stud bolt so that a friction coefficient of a portion of the stud bolt screwed into the screw hole of the mounting plate is larger than a friction coefficient of a portion screwed to the second nut. 3. A gas-insulated electric device according to claim 1, wherein a portion to be screwed into the screw hole and a portion to be screwed into the second nut have different surface treatments. 4. The difference between the tightening torque at the time of screwing the stud bolt into the screw hole of the mounting plate and the tightening torque at the time of screwing the second nut onto the stud bolt is the second torque. The gas-insulated electric device according to any one of claims 1, 2, and 3, wherein the torque is set to 20% or more of a tightening torque when the nut is screwed.