JP5330192B2 - Gas insulated electrical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas-insulated electric apparatus which reduces a gas pressure in a pressure tank while securing insulation performance in the pressure tank. <P>SOLUTION: The gas-insulated electric apparatus is equipped with: the pressure tank 2 in which an insulative gas and the electric apparatus are tightly accommodated, and an opening which corresponds to a terminal arranged in the electric apparatus is formed; a porcelain tube 20 which is arranged so as to protrude to the pressure tank, fixed to the opening in its base, and has a terminal conductor at its end; and draw-out conductors 11a, 11b which are arranged so as to penetrate the center of the porcelain tube while one-side ends are electrically connected to the terminal and the other ends are connected to the terminal conductor of the porcelain tube. The gas-insulated electric apparatus is also equipped with: bushing conductors 22a, 32a which are arranged in series so as to be interposed between the one-side ends of the draw-out conductors and the terminal; insulated bodies 21, 31 which co-axially surround axial centers of the bushing conductors; and intermediate bushings 210, 310 composed of grounding layers 23, 33 formed in axial centers of external peripheral faces of the insulated bodies. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a gas-insulated electrical apparatus that can be preferably used as, for example, a switch for power transmission / distribution and power distribution facilities.

As a switchgear that is a conventional gas-insulated electrical device, an insulator such as epoxy resin is used as a conductor to electrically insulate between a pressure tank filled with an insulating gas such as dry air and a conductor to which a high voltage is applied. There is one in which insulation is ensured by covering it (see, for example, Patent Document 1). In such a gas insulated switchgear, dry air is sealed at a high gas pressure of about 0.4 to 0.5 MPa-g.
In addition, it is equipped with a vacuum valve (vacuum interrupter) installed in the pressure tank and fitted with a bellows at one end. The gas pressure in the peripheral area outside the bellows and the gas pressure in the pressure tank are hermetically separated to There is one in which the pressure difference between the inside and outside of the bellows is reduced by maintaining the atmospheric pressure to prevent the bellows from being damaged, and insulation between the vacuum valve and the pressure tank is ensured (for example, see Patent Document 2).

Japanese Unexamined Patent Publication No. 2003-319515 (first page, FIG. 1) JP 2007-306701 A (first page, FIG. 1)

In the conventional gas-insulated electrical equipment as described above, since a high gas pressure of about 0.4 to 0.5 MPa-g is applied to the pressure tank, it is necessary to increase the thickness of the pressure tank. It has been difficult to reduce weight and cost. Further, since the dielectric strength of dry air is about 1/3 of SF ₆ gas, there is a problem that it is difficult to ensure the insulation performance in the pressure tank when the gas pressure in the pressure tank is lowered. In particular, the insulation part of the installation part of the soot pipe which draws electric power from the outside, and the location where the current transformer is installed has a short insulation distance, and it is difficult to insulate only with dry air.

  The present invention has been made to solve the above-described problems of the prior art, and provides a gas-insulated electrical apparatus capable of reducing the gas pressure in the pressure tank while ensuring the insulation performance in the pressure tank. The purpose is that.

  A gas-insulated electrical apparatus according to the present invention includes a pressure tank in which an insulating gas and an electrical device are hermetically accommodated and provided with an opening corresponding to a terminal portion provided in the electrical device, and the gas tank projects from the pressure tank. Arranged so that the base is fixed to the opening, and a terminal conductor is provided at the tip, and one end is electrically connected to the terminal. A bushing conductor provided in series so as to be interposed between one end of the lead conductor and the terminal portion in a gas-insulated electric apparatus having a lead conductor having the other end connected to the terminal conductor of the steel pipe In addition, an intermediate bushing comprising an insulator coaxially surrounding the axial central portion of the bushing conductor and a grounding layer provided in the axial central portion of the outer peripheral surface of the insulator is provided.

  In the present invention, the intermediate portion between the lead conductor and the terminal portion of the electric device is constituted by the intermediate bushing having the outer peripheral surface provided with the ground layer, so that the pressure tank is secured while ensuring the insulation performance in the pressure tank. The gas pressure inside can be reduced. Therefore, it is possible to reduce the weight and cost of the device.

It is sectional drawing which shows the tank type vacuum circuit breaker which is a gas insulated electrical apparatus which concerns on Embodiment 1 of this invention. It is an expanded sectional view which shows the other structural example of the grounding shield shown by FIG. It is sectional drawing which shows the modification of Embodiment 1 which changed the support system of the vacuum valve shown by FIG. It is sectional drawing which shows the tank type vacuum circuit breaker which is a gas insulated electrical apparatus which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
Hereinafter, a tank-type vacuum circuit breaker that is a gas-insulated electric apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. In FIG. 1, an electrically grounded pressure tank 2 constituting a tank type vacuum circuit breaker 1 is installed with a body portion 2 a horizontally, and a pair of cylindrical openings above the pressure tank 2. 2b and 2c, cylindrical current transformer installation portions 2d and 2e, which are coaxial with the openings 2b and 2c and have a smaller diameter than the openings 2b and 2c, and the current transformers and the current transformers 2b and 2c. It is comprised from the ring-shaped flange member F provided in the connection location of the installation parts 2d and 2e. A current transformer 7 for measuring current is installed on the outer periphery of the current transformer installation parts 2d and 2e. In this example, the openings 2b and 2c and the current transformer installation portions 2d and 2e are connected via a flange member F by welding.

  A vacuum valve 4 as an electric device is installed in the pressure tank 2 through a gap with the body 2a. The vacuum valve 4 includes a cylindrical vacuum vessel 41 made of an insulating material such as ceramic, and an end plate 42 that is housed in the vacuum vessel 41 and that has one end hermetically sealing the fixed side end 41a of the vacuum vessel 41. A fixed conductor 43 joined, and a movable conductor 45 provided outside the vacuum container 41 via a bellows 44 provided at the other end 41b of the vacuum container 41 so as to be able to contact and separate from the fixed conductor 43. It consists of A fixed contact 43a and a movable contact 45a are formed at portions where the fixed conductor 43 and the movable conductor 45 are in contact with each other. Note that the end plate 42, the fixed conductor 43, and the movable conductor 45 are made of a conductive material such as a copper alloy or an aluminum alloy, and the vacuum valve 4 is kept airtight in a vacuum.

  On the outside of the pressure tank 2 is provided an opening / closing means 3 for contacting and separating the fixed contact 43a and the movable contact 45a. The opening / closing means 3 opens and closes the fixed contact 43a and the movable contact 45a by moving the movable conductor 45 in the horizontal direction via the operation rod 5 and the insulating rod 6. At this time, since the bellows 44 follows the movement of the movable conductor 45, the vacuum in the vacuum valve 4 is maintained. The insulating rod 6 is connected while ensuring an insulating distance capable of electrically insulating the movable conductor 45 and the operating rod 5.

  A fixed shield 51 and a movable shield 52 are provided at both ends of the vacuum valve 4. The fixed-side shield 51 is disposed so as to cover the fixed-side end portion 41 a of the vacuum valve 4, and is connected to the fixed-side end plate 42. The movable shield 52 is disposed so as to cover the movable end 41 b of the vacuum valve 4 and the end of the movable conductor 45, and is connected to the movable end plate 46 of the vacuum valve 4. The fixed-side shield 51 and the movable-side shield 52 are made of a conductive material such as an aluminum alloy or a copper alloy, and the surfaces are formed as smooth surfaces without edges.

  In addition, as for the surface roughness of the said smooth surface, it is desirable that the average height Ra prescribed | regulated to JIS, for example is about 12 micrometers or less. Further, an insulating coating may be formed on the surfaces of the fixed side shield 51 and the movable side shield 52 by, for example, an insulating rubber, a resin such as epoxy, alumite treatment or powder insulation coating. In that case, the preferable film thickness of the insulating coating of the fixed shield 51 and the movable shield 52 is about 10 μm to 5 mm.

  The fixed-side shield 51 is fastened to the insulating support rod 9 attached to the base plate 8 via the adapter 10, and insulates and supports all the components for one phase from the fixed-side shield 51 to the operation rod 5. The rod 9 is supporting. The insulating support rod 9 has a strength and shape that can withstand the weight of the component parts and the impact during the opening / closing operation. Insertion portions 51a and 52a into which one ends of the bushing conductors 22a and 32a disposed at the center of the intermediate bushings 210 and 310 are inserted are provided above the fixed side shield 51 and the movable side shield 52. In this example, the insertion portions 51a and 52a have a function of a terminal portion of the vacuum valve 4 which is an electric device. The openings 2b and 2c are provided corresponding to the insertion portions 51a and 52a which are terminal portions.

  Electric field concentration at the fixed side end 41a and the movable side end 41b of the vacuum valve 4 by forming the fixed side shield 51 and the movable side shield 52 so as to cover the fixed side end 41a and the movable side end 41b. Can be relaxed. Further, by taking the support configuration by the insulating support rod 9, the assembly to the base plate 8 and the assembly to the pressure tank 2 can be integrated. A conductive coil 53 is provided between the movable conductor 45 and the movable shield 52 to electrically connect both of them. The conductive coil 53 has a circular shape as a whole by forming a copper alloy wire into a coil spring shape. Since the conductive coil 53 occupies a smaller volume than a commonly used flexible conductor formed by stacking thin copper plates, the shape of the movable shield 52 can be simplified and reduced.

  The intermediate bushings 210 and 310 in which the lower ends of the bushing conductors 22a and 32a are connected to the insertion portions 51a and 52a above the fixed-side shield 51 and the movable-side shield 52 have openings 2b and 2c and a current transformer installation portion 2d, 2e is arranged so as to penetrate through the space 2e and enter the lower part of the inside of the tub tube 20. And in the outer peripheral part of the intermediate bushings 210 and 310, the flange-shaped attachment parts 26 and 36 integrally formed with the insulators 21 and 31 are provided in the vicinity of the connecting part between the soot tube 20 and the current transformer installation parts 2d and 2e. The mounting portions 26 and 36 are supported and fixed so as to be sandwiched between the connecting portions of the soot tube 20 and the current transformer installation portions 2d and 2e.

  The intermediate bushings 210 and 310 are made of hollow bushing conductors 22a and 32a, and an insulator 21 indicated by hatching in the figure made of a thermosetting resin such as an epoxy resin casted coaxially therearound. , 31 and grounding layers 23, 33, which will be described later, provided in the axial center of the insulators 21, 31. Protruding portions 22b, 22c, 32b, and 32c having a large outer diameter are provided at locations immediately before the bushing conductors 22a and 32a are exposed from the insulators 21 and 31 in the vicinity of both ends. And in the triple junction part comprised from an insulator, a bushing conductor, and insulating gas, the hollow parts 24a and 24b formed so that the radial direction center side of the insulators 21 and 31 might be dented smoothly in an axial direction. , 34a, 34b are provided around.

  Further, for example, the grounding layers 23 and 33 formed of conductive rubber, conductive paint, etc. have the outer peripheral surfaces of the insulators 21 and 31 grounded such as the mounting portion of the vertical tube 20 and the current transformer mounting portions 2d and 2e. The member and the bushing conductors 22a and 32a are provided in the vicinity of each other. The ground layers 23 and 33 are provided to extend to the flange-like attachment portions 26 and 36 with the central portion in the axial direction of the intermediate bushings 210 and 310 as the center. The mounting portions 26, 36 are fastened to the ground potential by being fastened by bolts or the like (not shown) to the flange portions provided on the upper ends of the current transformer installation portions 2d, 2e or the mounting portions of the vertical tube 20. It has become.

  Also, the insulators 21 and 31 are larger in diameter at the lower end of the figure located in the openings 2b and 2c of the pressure tank 2 than in the central portion that penetrates the current transformer installation portions 2d and 2e. It is configured as a diameter portion A. Similarly, a large-diameter portion B having a diameter that is thicker than a portion passing through the attachment portion of the tub tube 20 or a central portion is also formed at an end portion on the upper side of the drawing from the attachment portion of the tub tube 20.

  Between the large-diameter portion A of the insulators 21 and 31 and the ground layers 23 and 33, ground shields 25 and 35 made of a metal such as aluminum or brass or a conductive resin are provided, for example. In FIG. 1, the ground shields 25 and 35 are provided only on the pressure tank 2 side, but may be provided on the side of the soot tube 20. The ground shields 25 and 35 and the ground layers 23 and 33 can be easily formed by, for example, applying conductive rubber constituting the ground layers 23 and 33 to the exposed portions of the ground shields 25 and 35. Can be articulated. Further, the ground shields 25 and 35 are provided with a recess 55 around the step formed at the boundary between the axial center portion of the insulators 21 and 31 and the large diameter portion A as shown in FIG. Alternatively, the end of the ground layer 23 (33) may be inserted into the ground and formed into the same shape as the ground shields 25 and 35.

  In general, a triple junction portion where three kinds of different materials of metal / insulator / insulating gas are in contact with each other tends to cause local electric field concentration to deteriorate the insulation performance. However, as in the first embodiment, the bushing conductor 22a , 32a is provided with protrusions 22b, 22c, 32b, 32c, while the insulators 21, 31 at the boundaries between the protrusions 22b, 22c, 32b, 32c are provided with recesses 24a, 24b, 34a, 34b. Since the equipotential lines are smoothly spread and the electric field of the triple junction portion is relaxed, it is difficult to generate discharge. Further, by providing the ground layers 23 and 33, the space between the current transformer installation portions 2d and 2e facing the outside of the ground layers 23 and 23 can be minimized, so that the current transformer installation portion of the pressure tank 2 2d and 2e can be reduced. At the same time, by reducing the mounting portion of the soot tube 20, a thin soot tube can be adopted, and the cost can be further reduced.

  In addition, since the large diameter portions A and B are formed at both ends in the axial direction of the insulators 21 and 31, respectively, the space electric field on the insulator creepage surface and around the insulator can be reduced. The effect of attaching the ground shields 25 and 35 is the same. The end surface of the rod tube 20 on the side opposite to the tube mounting portion (the upper end portion side in the figure) is hermetically sealed by the terminal conductors 12a and 12b. The lead conductors 11a and 11b whose other ends (upper side in the figure) are connected to the terminal conductors 12a and 12b are formed hollow, and the bushing conductor is formed by contact portions 13a and 13b provided at one end (lower side). 22a and 32a are slidably connected to the upper end of the figure. In the vicinity of the pressure tank 2 side end of the bushing conductors 22a and 32a and the vicinity of the terminal conductors 12a and 12b of the lead conductors 11a and 11b, through holes 14a to 14d penetrating the inside and outside of the hollow conductor are spaced apart in the circumferential direction. A plurality are provided.

  Further, the flange-like attachment portions 26 and 36 of the intermediate bushings 210 and 310 are provided with through holes 26a and 36a for partially communicating the space of the current transformer installation portions 2d and 2e and the space inside the vertical tube 20, respectively. It has been. And inside the pressure tank 2 and the soot pipe 20, the dry air whose water content is 10 ppm or less is enclosed as insulating gas. In the first embodiment, the maximum operating gas pressure is less than 0.2 MPa-g, but is not limited to this value. Further, since the bushing conductors 22a and 32a and the lead conductors 11a and 11b have a hollow structure and are provided with through holes as described above, there is only one gas space inside the tank type vacuum circuit breaker 1. Further, the seal location is only the connection location between the soot tube 20 and the current transformer installation portions 2d and 2e.

  In addition, the support system of the vacuum valve 4 with respect to the pressure tank 2 is not limited to what was illustrated in the said FIG. 1, For example, it can also be set as the system shown in FIG. That is, in FIG. 3, the vacuum valve 4 is supported by the support frame 16, the insulating support member 15, and the fixed-side shield 54 attached in the vicinity of the flange 2 f of the pressure tank 2. In this structure, it is not necessary for the fixed-side shield 54 to fasten the insulating support rod 9 (FIG. 1), so that the external dimensions of the fixed-side shield 54 can be reduced. In addition, the number of parts can be reduced as compared with the support by the insulating support rod 9.

  In the first embodiment configured as described above, the pressure in the pressure tank can be lowered by insulating the short insulation distance portions such as the soot tube mounting portion and the current transformer installation portion with the intermediate bushing. As a result, it is possible to reduce the cost such as reducing the thickness of the pressure tank. Further, by providing a ground layer at a place where the insulation distance is short, the pressure tank can be reduced and the current transformer can be reduced. Further, by providing large diameter portions A and B whose diameters are thicker than the portions where the grounding layer is provided at the axial ends of the insulators 21 and 31 constituting the intermediate bushings 210 and 310, creeping insulator creepage The space electric field at the top and the periphery can be reduced, and insulation is possible even with low-pressure dry air.

  Further, at both ends of the insulators 21 and 31 of the intermediate bushing, the installation shields 25 and 35 in contact with the ground layers 23 and 33 are provided at the ends of the ground layers 23 and 33, so that the intermediate Spatial electric fields on and around the insulators 21 and 31 of the bushings 210 and 310 can be reduced, and insulation is possible even with low-pressure dry air. Further, by providing a recess 55 as shown in FIG. 2 at one or both ends of the insulators 21 and 31, and providing the ground layers 23 and 33 in the recess 55, the installation shields 25 and 35 In addition to obtaining the same effect, the components of the installation shields 25 and 35 are not necessary, so that the cost can be reduced.

  Moreover, since the triple junction part was formed using the hollow parts 24a, 24b, 34a, and 34b, the electric field around the triple junction can be reduced, and the generation of discharge can be suppressed even with low-pressure dry air. Further, the protrusions 22b, 22c, 32b, and 32c having a large diameter are provided in front of the bushing conductors 22a and 32a that project from the insulators 21 and 31 (the nearest part), thereby reducing the variation of the triple junction. It can be configured in a stable shape. Further, as the bushing conductors 22a and 32a and the lead conductors 11a and 11b, since the hollow gas is used, the insulating gas can pass therethrough so that the insulating gas inside the pressure tank 2 and the inside of the vertical pipe 20 can be circulated. The heat dissipation effect of the conductor can be promoted.

  In addition, through holes are provided in the flange-like attachment portions 26 and 36 of the intermediate bushings 210 and 310 so that the inside of the soot tube 20 and the inside of the pressure tank 2 are communicated with each other. Can further increase the heat dissipation effect of the conductor.

  Moreover, since the dry air pressure in the pressure tank 2 is less than 0.2 MPa-g, the strength of the pressure tank 2 can be reduced, and the thickness of the pressure tank 2 can be reduced, or the reinforcement member of the pressure tank 2 can be reduced or simplified. Therefore, the weight and cost of the apparatus can be reduced. Furthermore, since the gas pressure in the pressure tank 2 is set to less than 0.2 MPa-g, it is not necessary to undergo the second type pressure vessel test. Moreover, since the pressure difference between the inside and outside of the bellows 44 in the vacuum valve 4 can be reduced by reducing the gas pressure in the pressure tank 2, it is not necessary to reinforce the bellows, and a general-purpose structure can be used.

  Moreover, in the conventional tank type vacuum circuit breaker as shown in Patent Document 1, the gas pressure in the peripheral region outside the bellows and the gas pressure in the pressure tank are hermetically separated, and the gas pressure outside the bellows is set to atmospheric pressure. In order to maintain the seal member, the seal member is provided in contact with the conductor whose temperature rises up to 115 ° C., and it is necessary to use an expensive seal member with high heat resistance. In the vacuum circuit breaker 1, the pressure tank 2 has one gas space, and there is no need to provide a seal member in contact with the conductor as in the prior art, so that it is not necessary to use an expensive seal member.

  Further, in the conventional switch, since the seal member is provided in contact with the movable member in order to keep the gas pressure outside the bellows at atmospheric pressure, the contact between the fixed contact and the movable contact in the vacuum valve is separated. The operation energy required for opening and closing is large, and it is necessary to increase the size of the operation mechanism as the opening and closing means. However, in the tank type vacuum circuit breaker 1 of the present embodiment, the fixed contact 43a and the movable contact 45a in the vacuum valve 4 are used. Since the operation energy required for opening / closing the door can be reduced, the opening / closing means 3 can be downsized.

In the first embodiment, dry air is used as the insulating gas. However, the insulating gas is not limited to dry air, and nitrogen, carbon dioxide, or the like can be used. Moreover, the gas pressure of the pressure tank 2 can be further reduced by using SF ₆ gas having high insulation performance as the insulating gas.

Embodiment 2. FIG.
Next, a tank type vacuum circuit breaker as a gas-insulated electric apparatus according to Embodiment 2 of the present invention will be described with reference to a cross-sectional view of FIG. Note that the same reference numerals denote the same or corresponding parts throughout the drawings. In the figure, the support structure around the vacuum valve 4 is the same as that of the first embodiment shown in FIG. On the other hand, the pressure tank 2 is constituted by the lower part of the drawing from the openings 2b and 2c, and the cylindrical current transformer mounting tanks 17a and 17b are prepared as separate parts. Accordingly, the current transformer mounting tanks 17a and 17b are provided with, for example, flanges at the upper ends of the openings 2b and 2c. Attached to.

  Further, the intermediate bushings 210 and 310 have flange-like attachment portions 26 and 36 integrally formed with the insulators 21 and 31 in the large-diameter portion A on the lower side of the figure, and the attachment portions 26 and 36 It is attached to the lower flanges of the current transformer mounting tanks 17a, 17b. The ground layers 23 and 33, the ground shields 25 and 35, the protruding portions 22b, 22c, 32b and 32c of the conductors, the recesses 24a, 24b, 34a and 34b, and the insulators 21 and 31 in the axial direction, which are other components The points formed in the large diameter portions A and B at the end portions, the through holes 26a and 36a provided in the mounting portions 26 and 36, and the like are the same as in the first embodiment.

  In the second embodiment configured as described above, in the pressure tank 2, the current transformer installation portions 2d and 2e of the first embodiment are configured as separate parts as current transformer mounting tanks 17a and 17b. Thereby, the external shape as the pressure tank 2 is small. Moreover, in Embodiment 1, when joining the current transformer installation parts 2d and 2e, it was necessary to weld while adjusting the coaxiality with the openings 2b and 2c, but in this example, this is not necessary, The pressure tank 2 can be easily manufactured and the manufacturing time can be shortened. Although the current transformer mounting tanks 17a and 17b are separate parts, since the shape is simple, the current transformer mounting tanks 17a and 17b can be manufactured inexpensively when compared with the manufacturing cost combined with the pressure tank 2.

  In the second embodiment, the distance from the attachment portions 26, 36 of the intermediate bushings 210, 310 to the fixed shield insertion portion 51a or the movable shield insertion portion 52a is shorter than that of the first embodiment, so that the pressure tank 2 can reduce the displacement of the bushing conductors 22a and 32a due to the deformation when the insulating gas is sealed. Further, when assembling, it is possible to assemble the soot tube 20, the current transformer mounting tanks 17a and 17b, and the intermediate bushings 210 and 310 as separate units, so that the assembling time can be shortened.

  In the first and second embodiments, the case where the electric device is the vacuum valve 4 has been described. However, the present invention is not limited to this. Moreover, it is not limited to a switch.

  DESCRIPTION OF SYMBOLS 1 Tank type vacuum circuit breaker, 2 Pressure tank, 2a Body part, 2b, 2c Opening part, 2d, 2e Current transformer installation part, 3 Opening-closing means, 4 Vacuum valve (electrical device), 7 Current transformer, 11a, 11b Lead conductor, 12a, 12b Terminal conductor, 13a, 13b Contact part, 14a-14d Through hole, 17a, 17b Current transformer mounting tank, 20 Steel pipe, 21, 31 Insulator, 22a, 32a Bushing conductor, 22b, 22c, 32b , 32c Protruding part, 23, 33 Ground layer, 24a, 24b, 34a, 34b Recessed part, 25, 35 Ground shield, 26, 36 Mounting part, 26a, 36a Through hole, 43 Fixed conductor, 43a Fixed contact, 44 Bellows, 45 movable conductor, 45a movable contact, 51, 54 fixed shield, 52 movable sheath De, 51a, 52a insertion portion (terminal portion), 55 recess, 210, 310 intermediate bushing, F flange member.

Claims (13)

  A pressure tank in which an insulating gas and an electric device are hermetically accommodated and an opening corresponding to a terminal portion provided in the electric device is provided, and a base portion is disposed so as to protrude from the pressure tank, and the base portion is opened A tube with a terminal conductor provided at the tip, and one end electrically connected to the terminal portion and the other end connected to the terminal conductor of the tube In a gas-insulated electrical apparatus including a connected lead conductor, a bushing conductor provided in series so as to be interposed between one end of the lead conductor and the terminal portion, and an axially central portion of the bushing conductor A gas-insulated electrical apparatus comprising an intermediate bushing comprising an insulator coaxially surrounding the periphery and a grounding layer provided at an axially central portion of the outer peripheral surface of the insulator.   The pressure tank includes a current transformer installation portion having a diameter smaller than that of the opening provided coaxially with the opening, and a base portion of the soot tube is connected to the current transformer installation portion. The gas-insulated electrical apparatus according to claim 1, wherein:   The intermediate bushing has a flange-shaped attachment portion formed integrally with the insulator in the vicinity of a connection portion between the base portion of the soot tube and the current transformer installation portion, and the attachment portion is connected to the soot tube and the current transformer. The gas-insulated electrical apparatus according to claim 2, wherein the gas-insulated electrical apparatus is fixed to a connecting portion of the vessel installation portion.   The gas-insulated electrical device according to claim 1, wherein a cylindrical current transformer mounting tank having a smaller diameter than the opening is interposed between the opening and the base of the soot tube.   The intermediate bushing has a flange-like attachment portion formed integrally with the insulator in the vicinity of the connection portion between the opening portion and the current transformer attachment tank, and the attachment portion is connected to the opening portion and the current transformer. The gas-insulated electrical device according to claim 4, wherein the gas-insulated electrical device is fixed to a connecting portion of the container mounting tank.   The through hole which connects the axial space divided by the said attachment part is provided in the flange-like attachment part of the said intermediate bushing, The Claim 3 to 5 characterized by the above-mentioned. Gas-insulated electrical equipment.   7. The gas-insulated electricity according to claim 1, wherein an electric field relaxation shield in contact with the ground layer is provided at an axial end of the ground layer around the insulator. machine.   8. A large-diameter portion having a diameter larger than that of a central portion where the grounding layer is provided at both axial ends of the insulator. Gas-insulated electrical equipment.   A step is provided in which one or both step portions of the large-diameter portion of the insulator are provided with a recess whose axial center is recessed in the axial direction, and the grounding layer is provided in the recess. Item 9. A gas-insulated electrical apparatus according to Item 8.   In the triple junction portion with the insulating gas formed in the portion where the bushing conductor is led out from the insulating portion, the surface on the radial center side of the axial end of the insulating portion is along the surface of the bushing conductor. The gas-insulated electrical device according to claim 1, wherein the gas-insulated electrical device is formed by a recess portion provided so as to be recessed in the axial direction.   11. The gas insulation according to claim 1, wherein the bushing conductor is provided with a projecting portion having a thickened diameter of the bushing conductor before projecting from the insulator. Electrical equipment.   The gas-insulated electrical apparatus according to any one of claims 1 to 11, wherein the inside of the bushing conductor is hollow.   The gas-insulated electric apparatus according to any one of claims 1 to 12, wherein the electric device is a vacuum valve.

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