JP2023022688A - gas circuit breaker - Google Patents

Abstract

To provide a gas circuit breaker capable of preventing or suppressing an increase in sliding friction force of movable contacts.SOLUTION: A gas circuit breaker (1) includes a fixed contact (13), a movable contact (17), a boost chamber (R) which serves as a thermal puffer chamber, and a conductive cylindrical guide (18) into which the movable contact (17) is inserted and which guides a linear motion of the movable contact (17). The cylindrical guide (18) has a small diameter part (18a) located on an edge side of the fixed contact (13) and a large diameter part (18b) with an inner diameter larger than the small diameter part (18a). The movable contact (17) has a thin shaft part (17c) guided by the small diameter part (18a) and a thick shaft part (17d) with an outer diameter larger than the thin shaft part (17c) and guided by the large diameter part (18b). An inner peripheral surface of the large diameter part (18b) and an outer peripheral surface of the thick shaft part (17d) make sliding contact to conduct the movable contact (17) and the cylindrical guide (18).SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a thermal puffer arc extinguishing type gas circuit breaker that is used to interrupt a fault current in an electric power system and interrupts an arc generated between contacts by blowing gas onto the arc.

Conventionally, the gas circuit breaker disclosed in Patent Document 1, for example, is known as the gas circuit breaker described above.

In the gas circuit breaker disclosed in Patent Literature 1, a fixed contact is arranged in a pressurized chamber provided in an upper electrode. The movable contact enters the pressurizing chamber through a nozzle positioned at the bottom of the pressurizing chamber and contacts the stationary contact. The movable contact is inserted through an opening provided in the center of the lower electrode, and a sliding contact is provided on the inner circumference of the opening. The movable contact is arranged in sliding contact with the sliding contact.

When the current (fault current) is interrupted, the movable contact moves downward. When the tip of the movable contact comes off the nozzle as it moves, the high-temperature gas accumulated in the pressurizing chamber is released from the nozzle to the outside of the pressurizing chamber. The released gas is blown against the arc, and arc extinguishing action occurs due to the heat puffer effect.

JP-A-11-25819

However, in the gas circuit breaker disclosed in the conventional patent document 1, since the gas discharged from the nozzle is blown toward the movable contact, the decomposition products generated by the arc and the arc Grease that has been seized by heat adheres. If these deposits adhere to the movable contact, the sliding frictional force between the movable contact and the sliding contact may increase.

SUMMARY OF THE INVENTION One aspect of the present invention has been made in view of the conventional problems described above, and an object thereof is to provide a gas circuit breaker capable of preventing or suppressing an increase in sliding friction force of a movable contact.

In order to solve the above problems, a gas circuit breaker according to an aspect of the present invention includes a fixed contact, a rod-shaped movable contact that moves in and out of contact with the fixed contact by linear movement, and the fixed contact. a heat puffer chamber located inside for accumulating gas expanded by an arc generated between the fixed contact and the movable contact; a conductive guide cylinder for guiding the linear motion of the contact, the guide cylinder having a first inner diameter portion located on the end portion side of the fixed contactor and having an inner diameter larger than the first inner diameter portion. The movable contact has a second inner diameter portion, and the movable contact has a first shaft portion guided by the first inner diameter portion, and a larger outer diameter than the first shaft portion and guided by the second inner diameter portion. wherein the inner peripheral surface of the second inner diameter portion and the outer peripheral surface of the second inner diameter portion are in sliding contact with each other so that the movable contactor and the guide cylinder are electrically connected. Characterized by

According to the above configuration, the second inner diameter portion, which is not directly exposed to the high-temperature gas flow that causes the arc-extinguishing action due to the heat puffer effect, is less prone to deposits such as decomposition products due to the arc. Therefore, by sliding the movable contact and establishing conduction between the movable contact and the guide tube in this portion, it is possible to prevent or suppress an increase in the sliding friction force of the movable contact. Also, by providing the guide tube, the linear motion of the movable contact can be stabilized.

In the gas circuit breaker according to one aspect of the present invention, the inner peripheral surface of the second inner diameter portion and the first inner diameter portion are further provided near the boundary between the second shaft portion or the second inner diameter portion and the first inner diameter portion. A configuration may be employed in which a vent hole is provided to allow gas to flow into the space defined by the two shafts.

According to the above configuration, it is possible to allow gas to flow into the space surrounded by the inner peripheral surface of the guide tube and the second shaft portion of the movable contact, thereby avoiding the load during operation of the movable contact.

In the gas circuit breaker according to one aspect of the present invention, the gap between the first inner diameter portion and the first shaft portion may be larger than the gap between the second inner diameter portion and the second shaft portion. good.

According to the above configuration, it is possible to prevent or suppress an increase in the sliding frictional force of the movable contact due to the above-described decomposition products and the like adhering to the first shaft portion of the movable contact.

The gas circuit breaker according to one aspect of the present invention may further have a configuration in which a piston ring is provided on the inner peripheral surface of the first inner diameter portion.

According to the above configuration, not only is the slidability between the first inner diameter portion and the first shaft portion improved, but also high-temperature gas containing decomposition products and the like is effectively prevented from entering the guide cylinder. be able to. As a result, it is possible to more effectively prevent an increase in the sliding friction force of the movable contact.

In the gas circuit breaker according to one aspect of the present invention, a groove is formed in the inner peripheral surface of the second inner diameter portion or the outer peripheral surface of the second shaft portion, and a sliding contact is attached to the groove. may be configured.

According to the above configuration, sliding contact between the inner peripheral surface of the second inner diameter portion and the outer peripheral surface of the second shaft portion can be easily achieved.

According to one aspect of the present invention, it is possible to prevent or suppress an increase in the sliding friction force of the movable contact.

It is a sectional view showing composition of a gas circuit breaker of a 1st embodiment, and shows a closed state. 2 is an enlarged view of a region B1 shown in FIG. 1; FIG. It is a sectional view showing composition of a gas circuit breaker in a 1st embodiment, and shows a state under current interruption. It is a sectional view showing composition of a gas circuit breaker of a 1st embodiment, and shows an opening state. It is sectional drawing which shows the structure of the gas circuit breaker of 2nd Embodiment, and shows a closed state. It is sectional drawing which shows the structure of the gas circuit breaker of the modification of 2nd Embodiment, and shows a closed state. It is a sectional view showing composition of a gas circuit breaker of a modification of a 1st embodiment, and shows a closed state.

[Embodiment 1]
An embodiment of the present invention will be described in detail below. The gas circuit breaker of the present embodiment is, for example, a thermal puffer arc-extinguishing type gas circuit breaker that is used to interrupt a fault current in an electric power system and interrupts an arc generated between contacts by blowing gas onto it. Gas circuit breakers are suitable for use in insulated switchgear (GIS) and housed in a container containing an arc-extinguishing gas.

(1. Configuration of gas circuit breaker)
The configuration of the gas circuit breaker 1 of this embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view showing the configuration of a gas circuit breaker 1 according to this embodiment. For convenience of explanation, it is assumed that the gas circuit breaker 1 is arranged in the vertical direction, and the movable contactor 17, which will be described later, moves in the vertical direction.

As shown in FIG. 1, the gas circuit breaker 1 is installed in a case (not shown) filled with an arc-extinguishing gas (hereinafter simply referred to as gas) G, and the gas circuit breaker 1 is surrounded by gas. There is a G. Gas G is, for example, SF ₆ , Dry Air, N ₂ , CO ₂ , O ₂ , CF ₄ , fluoronitriles, fluoroketones and mixed gases thereof.

The gas circuit breaker 1 includes an upper conductor 11, a lower conductor 12, a fixed contact 13, a drive coil 14, an arc runner 15, an insulating nozzle 16, a movable contact 17, a cylindrical guide (guide tube) 18, a sliding contact 19, It has a piston ring 20, an operating rod 21, and the like.

The upper conductor 11 and the lower conductor 12 are arranged apart from each other in the vertical direction. Each of the upper conductor 11 and the lower conductor 12 is supported and insulated by a supporting member (not shown).

The insulating nozzle 16 is attached to the lower surface side of the upper conductor 11 . The insulating nozzle 16 is a cup-shaped member whose lower surface is recessed inward in the shape of a mortar. The center of the lower surface of the insulating nozzle 16, which serves as a mortar-shaped bottom, is opened to form a through hole 16a. A space surrounded by the upper conductor 11 and the insulating nozzle 16 is a boosting chamber R, which is a heat puffer chamber. The pressurizing chamber R is filled with a gas G, and the pressurizing chamber R accumulates gas expanded by an arc A (see FIG. 3) generated between the fixed contact 13 and the movable contact 17 .

The stationary contact 13, the drive coil 14, and the arc runner 15 are arranged inside the boost chamber R. As shown in FIG. The fixed contact 13 is a cylindrical contact provided on the lower surface of the upper conductor 11 . The fixed contact 13 is integrated with the upper conductor 11 or supported by the upper conductor 11 and electrically connected to the upper conductor 11 .

The movable contactor 17 is a rod-shaped contactor arranged below the fixed contactor 13 and is provided so as to be separable from the fixed contactor 13 . The movable contact 17 is inserted (stored) inside the cylindrical guide 18 . The movable contactor 17 moves linearly along the cylindrical guide 18 in the vertical direction, which is its axial direction, to separate and contact the fixed contactor 13 .

When the movable contact 17 is driven upward, the tip 17a side enters the pressurizing chamber R, is inserted into the fixed contact 13, and comes into contact with the fixed contact 13. As shown in FIG. Further, when the movable contact 17 is driven downward, the tip 17a side is pulled out from the inside of the fixed contact 13 and is out of contact with the fixed contact 13 . An operating rod 21 is attached to the rear end 17b of the movable contact 17 opposite to the tip 17a.

The cylindrical guide 18 has a cylindrical shape, the movable contactor 17 is inserted therein, and guides the linear motion of the movable contactor 17 . The cylindrical guide 18 is conductive, supported by the lower conductor 12 and electrically connected to the lower conductor 12 . The movable contact 17 is in sliding contact with the inner peripheral surface of the cylindrical guide 18 on the rear end 17b side. In this embodiment, a sliding contact 19 is provided, and the inner peripheral surface of the cylindrical guide 18 and the movable contact 17 are brought into sliding contact with each other via the sliding contact 19 . Movable contact 17 is electrically connected to lower conductor 12 via conductive cylindrical guide 18 and sliding contact 19 .

(2. Movable Contactor 17 and Cylindrical Guide 18)
Here, the movable contactor 17 and the cylindrical guide 18 will be described in more detail with reference to FIG. FIG. 2 is an enlarged view of area B1 shown in FIG. As shown in FIG. 2, the cylindrical guide 18 has different inner diameters in the axial direction. ) 18b. The small-diameter portion 18a is positioned at the upper portion, which is the end portion side on the fixed contact 13 side.

Corresponding to the cylindrical guide 18 having such a shape, the outer diameter of the movable contactor 17 is also different in the axial direction. and a (second shaft portion) 17d having a large outer diameter.

The small diameter portion 18a of the cylindrical guide 18 and the thin shaft portion 17c of the movable contactor 17 correspond to each other, and when the movable contactor 17 moves, the thin shaft portion 17c is guided by the small diameter portion 18a. Similarly, the large diameter portion 18b of the cylindrical guide 18 corresponds to the thick shaft portion 17d of the movable contactor 17, and when the movable contactor 17 moves, the thick shaft portion 17d is guided by the large diameter portion 18b. . An annular groove 17e is formed in the outer peripheral surface of the thick shaft portion 17d, and a sliding contact 19 is attached to the groove 17e.

The gap between the thick shaft portion 17d and the large diameter portion 18b is set smaller than the gap between the small diameter portion 18a and the thin shaft portion 17c. In other words, the gap between the small diameter portion 18a and the thin shaft portion 17c is set larger than the gap between the thick shaft portion 17d and the large diameter portion 18b.

That is, the thick shaft portion 17d and the large diameter portion 18b are tightly fitted. This is to ensure that the sliding contact 19 located on the outer peripheral surface of the thick shaft portion 17d slides against the inner peripheral surface of the large diameter portion 18b. On the other hand, the fitting between the thin shaft portion 17c and the small diameter portion 18a is looser fitting (fitting with a larger gap) than the fitting between the thick shaft portion 17d and the large diameter portion 18b. Since it does not function as a sliding contact, the fit between the thin shaft portion 17c and the small diameter portion 18a may be a fit that guides the movement of the thin shaft portion 17c.

In this embodiment, a piston ring 20 is attached to the inner peripheral surface of the small diameter portion 18a. The piston ring 20 is fitted into an annular groove 17f formed in the inner peripheral surface of the small diameter portion 18a. In this embodiment, the piston rings 20 are fitted in two locations in the vertical direction. Further, in the present embodiment, a ventilation hole 25 is formed through the thick shaft portion 17d in the axial direction. Ventilation hole 25 allows gas, that is, gas G, to flow into space S defined by the inner peripheral surface of large diameter portion 18b and thick shaft portion 17d.

(3. Operation of gas circuit breaker)
The operation of the gas circuit breaker 1 of this embodiment will be described with reference to FIGS. 1, 2, 3 and 4. FIG. 3 and 4 are cross-sectional views showing the configuration of the gas circuit breaker 1 according to this embodiment, similar to FIG. However, FIG. 1 shows the closed state, FIG. 3 shows the state during current interruption, and FIG. 4 shows the open state. The closed state is a state in which the movable contact 17 is in the upper closed position and the upper conductor 11 and the lower conductor 12 are electrically connected. The open state is a state in which the movable contact 17 is in the lower open position and the upper conductor 11 and the lower conductor 12 are not electrically connected. The state in which the current is interrupted is a state in which the movable contact 17 is in the middle of the closing position and the opening position and an arc A is being generated.

As shown in FIG. 1, when the movable contact 17 is driven upward, the tip 17a side of the movable contact 17 passes through the through-hole 16a of the insulating nozzle 16 and enters the pressurizing chamber R, and the inside of the fixed contact 13. is inserted into and comes into contact with the fixed contact 13 . As a result, the closed state is established, and the upper conductor 11 and the lower conductor 12 are electrically connected via the fixed contact 13 , movable contact 17 , sliding contact 19 and cylindrical guide 18 .

When the movable contact 17 is rapidly moved downward from the closed state of FIG. 1 to separate the movable contact 17 from the fixed contact 13, as shown in FIG. Arc A is generated between

Arc A moves from fixed contact 13 to arc runner 15 provided in drive coil 14 . Then, current flows through the drive coil 14 and the arc A is magnetically driven. As a result, the arc A rotates at high speed in the gas atmosphere, and the gas G is relatively blown onto the arc A, thereby extinguishing the arc A due to the magnetic driving effect.

Also, the arc A rotates at high speed in the pressurizing chamber R, thereby causing the surrounding gas G to expand due to heat. Since the through-hole 16a of the insulating nozzle 16 is blocked by the movable contact 17, the pressure of the expanded gas G is accumulated in the pressurizing chamber R. As shown in FIG. The pressure-accumulated high-temperature gas G is released from the through hole 16a of the insulating nozzle 16 at the tip 17a side end of the movable contact 17, becomes a high-temperature gas flow G1, and flows from the pressurizing chamber R through the through hole 16a. It is ejected to the outside. Since the high-temperature gas flow G1 is blown against the arc A, an arc-extinguishing action of the arc occurs due to the heat puffer effect.

As shown in FIG. 4, in the closed state in which the movable contact 17 is driven downward, the movable contact 17 is sufficiently separated from the fixed contact 13, and the upper conductor 11 and the lower conductor 12 are disconnected.

1, the space S surrounded by the inner peripheral surface of the cylindrical guide 18 and the thick shaft portion 17d of the movable contact 17 is the piston. Because it is a structure, a load is applied. In the above configuration, since the vent hole 25 is provided in the thick shaft portion 17d, the gas G is drawn into the space S from the outside through the vent hole 25, and the load due to the piston structure can be avoided. Further, in the operation of moving the movable contactor 17 upward, the gas G in the space S is released to the outside through the ventilation hole 25, thereby avoiding the above load.

(4. Effect)
The high-temperature gas flow G1 that brings about the arc-extinguishing action by the heat puffer effect contains decomposition products generated by the arc. As shown in FIG. 3, since such a high-temperature gas flow G1 is blown toward the movable contact 17, decomposition products adhere to the surface of the portion of the movable contact 17 protruding from the cylindrical guide 18. do. In addition, grease baked by arc heat also adheres to this portion. Furthermore, when the high-temperature gas G containing decomposition products enters the cylindrical guide 18 , the decomposition products also adhere to the inner peripheral surface of the cylindrical guide 18 .

When such deposits (decomposition products and seized grease) adhere to the inner peripheral surface of the cylindrical guide 18 on which the sliding contact 19 slides, the sliding contact 19 and the movable contact 17 are separated from each other. , that is, the sliding friction force between the movable contact 17 and the cylindrical guide 18 increases. If the sliding friction force increases, the movable contactor 17 cannot operate at an appropriate speed, and the operating characteristics change before and after interrupting the large current.

1) Therefore, in the gas circuit breaker 1, as described above, the cylindrical guide 18 has a small-diameter portion 18a on the side of the fixed contact 13, and a large-diameter portion 18b on the opposite side. A thin shaft portion 17c guided by the small diameter portion 18a and a thick shaft portion 17d guided by the large diameter portion 18b are provided, and the sliding contact 19 is arranged on the thick shaft portion 17d. By adopting such a configuration, the following effects can be obtained.

- The inner peripheral surface of the large-diameter portion 18b is a portion that is not directly exposed to the high-temperature gas flow G1. Therefore, the deposits are less likely to adhere to the inner peripheral surface of the large-diameter portion 18b. Therefore, by arranging the sliding contact 19 in this portion, it is possible to more effectively prevent an increase in sliding frictional force between the movable contact 17 and the cylindrical guide 18 .

- The area of the inner peripheral surface of the large diameter portion 18b is larger than the area of the inner peripheral surface of the small diameter portion 18a. The "area of the inner peripheral surface" referred to here is not the axial cross-sectional area of the inner peripheral surface, but the area of the inner wall surface. Therefore, even if the high-temperature gas G enters the large-diameter portion 18b through the gap between the small-diameter portion 18a and the thin shaft portion 17c, the large-diameter portion 18b has a large inner peripheral surface area. The area that adheres to the peripheral surface is limited to a small portion of the entire inner peripheral surface. So no problem.

- Deposits adhere to the surface of the thin shaft portion 17c of the movable contactor 17, particularly the portion protruding from the cylindrical guide 18. However, the fitting between the small-diameter portion 18a and the thin shaft portion 17c may be such that it guides the vertical movement (axial movement) of the thin shaft portion 17c. Therefore, the gap between the small diameter portion 18a and the thin shaft portion 17c can be made larger than the gap between the large diameter portion 18b where the sliding contact 19 is located and the thick shaft portion 17d. Therefore, the increase in the sliding frictional force caused by the deposits adhering to the thin shaft portion 17c does not pose a problem.

2) In addition, in the gas circuit breaker 1, the piston ring 20 is attached to the inner peripheral surface of the small diameter portion 18a. The provision of the piston ring 20 not only improves the slidability between the small diameter portion 18a and the thin shaft portion 17c, but also prevents the high temperature gas G containing decomposition products from entering the cylindrical guide 18. can be effectively prevented. As a result, an increase in the sliding friction force between the movable contact 17 and the cylindrical guide 18 can be prevented more effectively.

3) A space S surrounded by the inner peripheral surface of the cylindrical guide 18 and the thick shaft portion 17d of the movable contactor 17 has a piston structure, and thus can become a load when the movable contactor 17 operates. However, in the gas circuit breaker 1, since the ventilation hole 25 is provided in the thick shaft portion 17d, such a load can be avoided.

4) Since the cylindrical guide 18 is provided, the linear motion of the movable contactor 17 is stabilized as compared with a configuration in which the cylindrical guide 18 is not provided. As a result, the movable contact 17 can be slid along the sliding axis without being displaced.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIGS. 5 and 6. FIG. The configuration other than that described in this embodiment is the same as that of the first embodiment. Also, for convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are denoted by the same reference numerals, and their explanations are omitted.

In the gas circuit breaker 1 of Embodiment 1, the sliding contact 19 is attached to the outer peripheral surface of the thick shaft portion 17 d of the movable contact 17 . On the other hand, in the gas circuit breaker 1A of this embodiment, the sliding contact 19 is attached to the inner peripheral surface of the large diameter portion 18b of the cylindrical guide 18. As shown in FIG. This point is different from the gas circuit breaker 1 .

FIG. 5 is a cross-sectional view showing the configuration of the gas circuit breaker 1A in this embodiment, showing the closed state. As shown in FIG. 5, in the gas circuit breaker 1A, an annular groove 18c is formed in the inner peripheral surface of the large diameter portion 18b of the cylindrical guide 18, and the sliding contact 19 is attached to the groove 18c. It is A plurality of grooves 18c are formed along the axial direction. In the example of FIG. 5, four grooves 18c are formed and a total of four sliding contacts 19 are arranged. When the movable contactor 17 moves vertically, the thick shaft portion 17d is always in contact with one of the plurality of sliding contactors 19 arranged in the axial direction.

Moreover, FIG. 6 is sectional drawing which shows the structure of the gas circuit breaker 1B of the modification of this embodiment, and shows a closed state. As shown in FIG. 6, in the gas circuit breaker 1B, the thick shaft portion 17d of the movable contact 17 is a thick shaft portion 17d' elongated in the axial direction. The sliding contact 19 is positioned at the highest position (closed position) even when the thick shaft portion 17d′ on the inner peripheral surface of the large diameter portion 18b of the cylindrical guide 18 is at the lowest position (opened position). ) is also provided at a position in contact with the thick shaft portion 17d′. When the movable contact 17 moves vertically, the thick shaft portion 17 d ′ is always in contact with the sliding contact 19 .

<Modification>
In the gas circuit breakers 1, 1A, and 1B described above, the ventilation holes 25 are provided in the thick shaft portions 17d and 17d', but as shown in FIG. It may be provided in the vicinity of the boundary with When provided in the large diameter portion 18b, it may be provided in a portion positioned above the upper surface of the thick shaft portion 17d in the closed state. FIG. 7 is a cross-sectional view showing the configuration of a gas circuit breaker 1C of a modified example of the first embodiment, showing a closed state.

Further, in the gas circuit breakers 1, 1A, and 1B, grooves 17e and 18c are formed in the outer peripheral surface of the thick shaft portion 17d or the inner peripheral surface of the large diameter portion 18b to attach the sliding contactor 19 thereto. However, the outer peripheral surface of the thick shaft portion 17d or the inner peripheral surface of the large diameter portion 18b may be processed into a shape that functions as the sliding contactor 19. FIG. Further, as described above, the outer peripheral surface of the thick shaft portion 17d and the inner peripheral surface of the large diameter portion 18b may slide against each other without using the sliding contactor 19 made of a separate member.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

1, 1A, 1B gas circuit breaker 11 upper conductor 12 lower conductor 13 fixed contact 17 movable contact 17c thin shaft portion (first shaft portion)
17d, 17d' thick shaft portion (second shaft portion)
18 Cylindrical guide (guide tube)
18a small diameter portion (first inner diameter portion)
18b large diameter portion (second inner diameter portion)
17e, 18c Groove 19 Sliding contact 20 Piston ring 25 Air vent A Arc G Arc-extinguishing gas G1 High-temperature gas flow R Pressurization chamber (thermal puffer chamber)

Claims (5)

a stationary contact;
a rod-shaped movable contact that moves in and out of contact with the fixed contact by linear motion;
a heat puffer chamber in which the fixed contact is located and which accumulates gas expanded by an arc generated between the fixed contact and the movable contact;
a conductive guide cylinder having a cylindrical shape, through which the movable contact is inserted, and which guides the linear movement of the movable contact;
The guide tube has a first inner diameter portion located on the end portion side of the fixed contact, and a second inner diameter portion having an inner diameter larger than that of the first inner diameter portion,
The movable contact has a first shaft portion guided by the first inner diameter portion and a second shaft portion having an outer diameter larger than that of the first shaft portion and guided by the second inner diameter portion. death,
A gas circuit breaker, wherein an inner peripheral surface of the second inner diameter portion and an outer peripheral surface of the second shaft portion are brought into sliding contact with each other so that the movable contactor and the guide cylinder are electrically connected. Flow of gas into a space defined by the second shaft portion and the inner peripheral surface of the second inner diameter portion near the boundary between the second inner diameter portion and the first inner diameter portion of the second inner diameter portion. 2. The gas circuit breaker according to claim 1, wherein a ventilation hole is provided to allow the 3. The gas circuit breaker according to claim 1, wherein a gap between said first inner diameter portion and said first shaft portion is larger than a gap between said second inner diameter portion and said second shaft portion. The gas circuit breaker according to any one of claims 1 to 3, wherein a piston ring is provided on the inner peripheral surface of the first inner diameter portion. 5. Any one of claims 1 to 4, wherein a groove is formed in the inner peripheral surface of the second inner diameter portion or the outer peripheral surface of the second shaft portion, and a sliding contact is attached to the groove. A gas circuit breaker according to the paragraph.

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