Vacuum circuit breaker and method for manufacturing vacuum circuit breaker

Abstract

A fixed-side contact (5a) and a movable-side contact (5b) are installed inside a vacuum valve (5), and the movable-side contact (5b) is connected to a movable electrode shaft (5c). The movable electrode shaft (5c) is connected to a bellows (5d) and is supported by a bearing (5h). The bearing (5h) is fixed to a bearing attachment part (5g) by a bolt, a fixing airtight part (5j) for hermetically sealing a surface of the bearing (5h) fixed to the bearing attachment part (5g) is provided, and an airtight sliding part (5k) for sealing the sliding surface with the movable electrode shaft (5c) is provided in the bearing (5h).

Description

Vacuum circuit breaker and method for manufacturing the same

[0001] The present disclosure relates to a vacuum interrupter and a method for manufacturing a vacuum interrupter.

[0002] A gas-insulated switchgear consists of a main circuit section to which high voltage is applied, an operating mechanism section that drives the switches in the main circuit section, and a control circuit section. The main circuit section of a gas-insulated switchgear is placed in a container where a gas with high insulating properties is pressurized and sealed. Increasing the pressure of the insulating gas improves the insulating performance and enables the overall switchgear to be made more compact. SF6 gas, which has high insulating properties, is generally used as the insulating gas. However, because SF6 gas has a high global warming potential, gas-insulated switchgears that use pressurized and sealed dry air, which has no impact on the environment, have recently been commercialized.

[0003] Furthermore, among the main circuit switches, circuit breakers capable of interrupting large currents include gas circuit breakers that use gases with excellent arc extinguishing performance, such as SF6 gas, and vacuum circuit breakers that use a vacuum valve in the arc extinguishing chamber. Vacuum circuit breakers were first applied to low voltage classes, but with increasing environmental awareness in recent years, there has been a growing need for vacuum circuit breakers that have no impact on the environment, rather than gas circuit breakers that use SF6 gas, which has a high global warming potential, and vacuum circuit breakers are gradually being applied to higher voltage classes as well.

[0004] In this way, gas-insulated switchgear equipped with vacuum circuit breakers are beginning to be applied to high voltage classes. The vacuum valve, which is the arc extinguishing chamber of a vacuum circuit breaker, is made of metal such as stainless steel or copper and an insulating material such as ceramic brazed together and sealed, and the inside of the container is maintained in a high vacuum. Inside the vacuum valve are contacts that switch high voltages and large currents, one contact is fixed to the vacuum valve container and the other contact is movable for opening and closing.

[0005] The moving parts of a vacuum valve use metal bellows, which have a cylindrical, bellows-like structure that allows them to open and close the contacts while maintaining a high vacuum inside the valve. However, the bellows of a vacuum valve is constantly subjected to stress due to the pressure difference between the surrounding pressure and the vacuum inside the valve. For example, when a vacuum valve is used at atmospheric pressure, a pressure difference of 1 atmosphere, which is the pressure difference between atmospheric pressure and the vacuum, is constantly present in the bellows. In addition, the bellows expands and contracts when the contacts of the vacuum valve are opened and closed, so stress is also generated in the bellows due to the expansion and contraction of the contacts. For this reason, the bellows is one of the vacuum valve's mechanical weak points.

[0006] Furthermore, in gas-insulated switchgear, increasing the gas pressure inside the container of the gas-insulated switchgear improves insulation performance and allows the device itself to be made more compact, so the pressure inside the container of high-voltage gas-insulated switchgear increases.When a vacuum valve is used in a high-voltage gas-insulated switchgear, stress is generated in the bellows of the vacuum valve due to the pressure difference between the high pressure inside the container of the gas-insulated switchgear and the vacuum inside the vacuum valve.Compared to when the vacuum valve is used at atmospheric pressure, the stress on the bellows due to the pressure difference is greater, posing a problem of shortening the lifespan of the bellows relative to the number of times it is opened and closed.

[0007] In the configuration shown in Figure 4 of Patent Document 1, an intermediate chamber is formed by airtightly sealing the movable side of the vacuum valve with an insulating cylinder, and the pressure in this intermediate chamber is set to a pressure intermediate between atmospheric pressure and vacuum, thereby reducing the pressure difference and stress on the bellows of the vacuum valve. Also, in the configuration shown in Figure 1 of Patent Document 1, two bellows, a first bellows and a second bellows, are used in the intermediate chamber, and the pressure in the intermediate chamber is set to a pressure intermediate between high pressure and vacuum. In this case, stress is generated in the second bellows due to the pressure difference between the high pressure and the intermediate pressure, and in the other first bellows due to the pressure difference between the high pressure and the intermediate pressure.

[0008] JP 2004-236455

[0009] In the configuration shown in Fig. 4 of Patent Document 1, a high voltage is also applied to the movable rod portion in the intermediate chamber, and the pressure in the intermediate chamber is low, between atmospheric pressure and vacuum, so the insulation performance in the gas is low. Therefore, in order to withstand high voltage insulation, the insulation distance needs to be increased, making it difficult to miniaturize the product.

[0010] Furthermore, in the configuration shown in FIG. 1 of Patent Document 1, two bellows are used, which increases the size of the vacuum valve itself. In addition, the stress on the bellows due to the pressure difference is greater than in the configuration shown in FIG. 4 of Patent Document 1, which poses the problem of shortening the mechanical life of the bellows.

[0011] The present disclosure discloses technology for solving the above-mentioned problems, and aims to provide a vacuum circuit breaker that can insulate parts other than the vacuum valve with high-pressure insulating gas and that enables the entire gas-insulated switchgear to be miniaturized.

[0012] a fixed airtight part for sealing the surface where the bearing is fixed to the bearing mount part, and an airtight sliding part for airtightly sealing the sliding surface with the movable electrode shaft. A method for manufacturing a vacuum circuit breaker according to the present disclosure includes the steps of: preparing a bearing having a first seal part mounted in a groove of the fixed airtight part and a second seal part mounted in a groove of the airtight sliding part; and mounting the bearing on the movable electrode shaft with the fixed contact and the movable contact in contact with each other in air, and fixing the bearing with bearing fixing bolts to seal the air in the space inside the bellows.

[0013] According to the vacuum circuit breaker and the method for manufacturing the vacuum circuit breaker of the present disclosure, the portions other than the vacuum valve can be insulated by high-pressure insulating gas, and the entire gas-insulated switchgear can be made smaller.

[0014] Fig. 1 is a side cross-sectional view showing a gas-insulated switchgear according to embodiment 1. Fig. 2 is a schematic diagram showing a vacuum circuit breaker section of a gas-insulated switchgear that is a comparative example. Fig. 3 is a schematic diagram showing a vacuum circuit breaker section of a gas-insulated switchgear according to embodiment 1. Fig. 4 is an enlarged view showing a peripheral portion of a bearing of a movable electrode shaft of a vacuum interrupter according to embodiment 1. Fig. 5 is a schematic diagram showing a vacuum circuit breaker section of a gas-insulated switchgear according to embodiment 1. Fig. 6 is an enlarged view showing a peripheral portion of a bearing of a movable electrode shaft of a vacuum interrupter according to embodiment 2. Fig. 7 is an enlarged view showing a peripheral portion of a bearing of a movable electrode shaft of a vacuum interrupter according to embodiment 3.

[0015] Embodiment 1. This embodiment relates to a vacuum circuit breaker, and in particular to the structure of a vacuum valve of a vacuum circuit breaker. The contents described in this embodiment can be used for the vacuum circuit breaker of a gas-insulated switchgear. FIG. 1 is a side cross-sectional view of a gas-insulated switchgear having a vacuum circuit breaker. The gas-insulated switchgear 1 includes a vacuum circuit breaker 2, a disconnecting switch and earthing switch 6, a bus 7, a power cable 9, etc., mounted in a sealed container 8, which is filled with an insulating gas such as dry air. The vacuum circuit breaker 2 is composed of a vacuum circuit breaker operating mechanism 3 located outside the sealed container 8 and a vacuum circuit breaker main circuit unit 4 located inside the sealed container 8. The vacuum circuit breaker main circuit unit 4 includes a vacuum circuit breaker vacuum valve 5. FIG. 2 is a schematic diagram showing the vacuum circuit breaker unit of a gas-insulated switchgear as a comparative example of this embodiment. A space 8a within the sealed container 8 is filled with high-pressure insulating gas. A fixed contact 5a and a movable contact 5b are located inside the vacuum valve 5, and the movable contact 5b is connected to a movable electrode shaft 5c.

[0016] The movable electrode shaft 5c is connected to a bellows 5d, and the inside of the vacuum valve 5 is maintained at a vacuum. The other end of the bellows 5d is attached to a container 5w that constitutes the vacuum valve 5. The movable electrode shaft 5c passes through an inner space 5f of the bellows 5d and protrudes outside the vacuum valve 5. The movable electrode shaft 5c is supported by a movable electrode shaft bearing 5e, which is fixed to a bearing mounting portion 5g with a bolt. The movable electrode shaft bearing 5e is made of thermoplastic or thermosetting resin. The reason for this is that the large current that flows through the vacuum circuit breaker flows via the fixed contact 5a, movable contact 5b, and movable electrode shaft 5c, but if the movable electrode shaft bearing 5e were made of metal, a current path would be created that passes through the fixed contact 5a, movable contact 5b, movable electrode shaft 5c, bellows 5d, bearing mount 5g, movable electrode shaft bearing 5e, and movable electrode shaft 5c, and current would also flow through this current path, causing damage to the bellows 5d. Therefore, by making the bearing 5e from a thermoplastic or thermosetting resin, current is prevented from flowing through the bellows 5d.

[0017] The movable electrode shaft 5c that protrudes outside the vacuum interrupter 5 is connected to an insulating operating rod 10, which is connected to an operating shaft 12 of the vacuum circuit breaker. The operating shaft 12 of the vacuum circuit breaker protrudes outside the sealed container 8 through an airtight sliding part 11 and is connected to a vacuum circuit breaker operating mechanism 3 (see Figure 1) not shown in Figure 2. The bearing 5e of the movable electrode shaft only mechanically supports the movable electrode shaft 5c and does not shield it airtight. Therefore, the inner space 5f of the bellows 5d contains the same high-pressure insulating gas as the space 8a inside the sealed container 8.

[0018] Figure 3 is a schematic diagram showing the vacuum circuit breaker section of a gas-insulated switchgear according to embodiment 1. The difference between Figure 2 and Figure 3 is that the movable electrode shaft bearing 5e shown in Figure 2 is replaced in Figure 3 with the movable electrode shaft bearing 5h of the vacuum interrupter according to embodiment 1; otherwise, Figure 3 is the same as Figure 2. Note that Figure 3 shows the circuit breaker contacts in an open state. Furthermore, the movable electrode shaft bearing 5h is made of thermoplastic or thermosetting resin for the same reasons as those described for the bearing 5e in Figure 2.

[0019] Figure 4 is an enlarged view of the area surrounding the bearing 5h of the movable electrode shaft of the vacuum interrupter shown in Figure 3. The movable electrode shaft bearing 5h of the vacuum interrupter according to embodiment 1 has a groove for the fixed airtight portion 5j for hermetically sealing the surface fixed to the bearing mounting portion 5g. This groove accommodates a sealing component such as an O-ring or packing. The movable electrode shaft bearing 5h also has a groove for the airtight sliding portion 5k for hermetically sealing the sliding surface with the movable electrode shaft 5c. This groove accommodates a sealing component such as a T-ring, X-ring, or a sealing component combining resin and a spring. This allows for airtight sliding during operation of the movable electrode shaft 5c. A T-ring has a T-shaped cross section, and Figure 4 shows the case where a T-ring is used. An X-ring refers to a ring packing with a nearly rectangular X-shaped cross section. The sealing component combining resin and a spring is assumed to be Balseal (registered trademark) manufactured by Valseal. Regarding vacuum interrupters used in vacuum interrupters, a high vacuum cannot generally be maintained without the use of a bellows. The bellows 5d is essential for driving the movable electrode shaft 5c while maintaining a high vacuum. The airtight sliding portion 5k is made of a rubber T-ring, which allows it to slide airtight, but this is only intended to ensure gas tightness. A rubber T-ring or the like can achieve gas tightness and can maintain a low vacuum for a short period of time, but a rubber T-ring or the like cannot maintain a high vacuum.

[0020] Figure 5 is a schematic diagram showing a vacuum circuit breaker section of a gas-insulated switchgear according to embodiment 1. While Figure 3 shows the circuit breaker contacts in an open state, Figure 5 shows the circuit breaker contacts in a closed state. The difference between Figure 3 and Figure 5 is that, while the contacts are open in Figure 3, in Figure 5, the movable contact 5b moves toward the fixed contact 5a to close the contacts, and the movable electrode shaft 5c, insulated operating rod 10, and vacuum circuit breaker operating shaft 12, which are connected to the movable contact 5b, also move toward the fixed contact 5a. Furthermore, as the movable electrode shaft 5c moves, the bellows 5d expands, increasing the space 5f inside the bellows.

[0021] During the manufacturing process of the vacuum valve, the contacts of the vacuum valve 5 are closed, as shown in Figure 5. This is because the vacuum valve's internal space 5m is a vacuum, while the bellows' inner space 5f is at atmospheric pressure, pushing the movable contact 5b due to the pressure difference. Next, we will explain how to attach the movable electrode shaft bearing 5h to the vacuum valve 5 to create a sealed space in the bellows' inner space 5f. To seal the bellows' inner space 5f to normal air, a sealing component (first sealing component) such as an O-ring or packing is attached to the groove of the fixed airtight portion 5j of the movable electrode shaft bearing 5h. Furthermore, a sealing component (second sealing component) such as a T-ring, X-ring, or a sealing component combining resin and a spring is attached to the groove of the airtight sliding portion 5k. Then, with the vacuum valve's contacts closed in air, the movable electrode shaft bearing 5h is attached and secured with the bearing-fixing bolts 5i.

[0022] When dry air or inert gas is sealed in the inner space 5f of the bellows, the vacuum valve and the bearing 5h for the movable electrode shaft are prepared in the sealed space for assembly, and after filling the sealed space for assembly with dry air or inert gas, the bearing 5h is installed in the sealed space for assembly and secured with the bearing securing bolts 5i. That is, in this case, the bearing 5h is prepared with the first seal component attached to the groove of the fixed airtight portion 5j and the second seal component attached to the groove of the airtight sliding portion 5k. Then, in the sealed space for assembly filled with dry air or inert gas, the bearing 5h is attached to the movable electrode shaft 5c with the fixed contact 5a and the movable contact 5b in contact, and secured with the bearing securing bolts 5i, thereby sealing the dry air or inert gas in the inner space 5f of the bellows 5d. Note that no insulating gas is present in the sealed container 8 during the manufacture of the vacuum valve 5. After the vacuum valve 5 is manufactured, the vacuum valve 5 and other components are assembled in the sealed container 8, the sealed container 8 is closed with a lid, and finally, the space 8a within the sealed container 8 is filled with insulating gas.

[0023] 3 to 5 , the bellows inner space 5f is at atmospheric pressure when the contacts of the vacuum valve 5 are closed. If the volume of the bellows inner space 5f when the contacts of the vacuum valve 5 are closed (FIG. 5) is V, the pressure is P, and the volume of the bellows inner space 5f when the contacts of the vacuum valve 5 are open is V1, then the pressure in the bellows inner space 5f when the contacts of the vacuum valve 5 are open is V / V1×P. Since V1<V, the pressure in the bellows inner space 5f is slightly higher than atmospheric pressure by the volume ratio. However, because the high pressure of the insulating gas in space 8a within the sealed container 8 is not applied to the bellows inner space 5f, stress on the bellows 5d due to the pressure difference can be reduced.

[0024] Furthermore, by setting the volume of the space 5f on the inner periphery of the bellows to be large and setting the difference between volumes V and V1 to be small, it is possible to reduce pressure fluctuations in the space 5f on the inner periphery of the bellows and extend the mechanical life of the bellows 5d. Meanwhile, since high-pressure insulating gas is sealed in the space 8a within the sealed container 8, areas other than the vacuum valve, such as around the insulating operating rod 10, can be insulated by the high-pressure insulating gas, making it possible to miniaturize the entire device.

[0025] With the above configuration, the size of the vacuum valve 5 can be kept to the same external dimensions as conventional products. The pressure inside the bellows ranges from atmospheric pressure to a pressure slightly higher than atmospheric pressure, and the bellows 5d is only subjected to stress due to the pressure difference between this pressure and the vacuum. Even when this vacuum valve 5 is installed in a gas-insulated switchgear 1 insulated with high-pressure insulating gas, the pressure inside the vacuum valve 5 remains at a pressure slightly higher than atmospheric pressure, and is not affected by the high pressure of the insulating gas around the vacuum valve 5. Furthermore, because the movable electrode shaft 5c and the insulated operating rod 10 of the vacuum valve 5 are insulated with high-pressure insulating gas, the gas-insulated switchgear 1 can be made more compact. Note that the gas compartment inside the bellows is a space surrounded by the metal bellows 5d and the movable electrode shaft bearing 5h, and almost no electric field is generated inside. Therefore, there is no need to consider the insulation performance of the gas compartment inside the bellows. In other words, although an electric field is generated by a potential difference (voltage difference), no electric field is generated because there is no potential difference inside the metal bellows 5d. By sealing in dry air, it is possible to prevent condensation, and by sealing in an inert gas, it is possible to eliminate oxygen and prevent deterioration due to oxidation.

[0026] Embodiment 2. Figure 6 is an enlarged view showing the area around the bearing of the movable electrode shaft of a vacuum interrupter according to embodiment 2. The difference from FIG. 4 in embodiment 1 is that FIG. 6 includes a hole for a gas supply port 5p in the bearing. All other aspects are the same as those in FIG. 4. In embodiment 1, atmospheric air, dry air, or an inert gas is sealed in the inner space 5f of the bellows when the contacts of the vacuum interrupter are closed. In embodiment 2, a hole for a gas supply port 5p is provided in the bearing 5n. After the bearing 5n is attached to the movable electrode shaft 5c, the air in the inner space 5f of the bellows is evacuated through the gas supply port 5p, and any gas, for example, an inert gas (a rare gas such as helium, neon, or argon, or nitrogen gas) is sealed in at any pressure through the gas supply port 5p.

[0027] Since the gas supply port 5p is only used when charging the gas, the hole of the gas supply port 5p is closed after charging the gas. As a specific example, when charging an arbitrary gas at atmospheric pressure into the inner peripheral space 5f of the bellows, the gas supply port 5p is made into a threaded hole, a pipe is attached to the threaded hole, the air in the inner peripheral space 5f of the bellows is evacuated, and the arbitrary gas is charged to atmospheric pressure. Even if the pipe is then removed, the inner peripheral space 5f of the bellows and its surroundings are both at atmospheric pressure, so there is almost no leakage of gas. Thereafter, the threaded hole that is the gas supply port 5p is gas-sealed with a seal bolt or a bolt with a gas seal material such as an O-ring, thereby making the inner peripheral space 5f of the bellows an airtight space.

[0028] Furthermore, when sealing any gas at or above atmospheric pressure in the bellows inner space 5f, the gas supply port 5p can be in the form of a pipe rather than a hole (threaded hole). That is, the pipe can be attached by welding, for example. Then, the bellows inner space 5f can be evacuated using the pipe and the gas can be sealed in. After the gas is sealed in, the base of the pipe attached to the gas supply port 5p can be completely sealed, making the bellows inner space 5f a sealed space. That is, the pipe can be cut in an airtight manner by crushing the end of the pipe. This leaves the bellows inner space 5f almost oxygen-free, preventing oxidation of the bellows 5d and the movable electrode shaft 5c and maintaining their long-term integrity.

[0029] Embodiment 3. Figure 7 is an enlarged view showing the bearing and surrounding area of ​​the movable electrode shaft of a vacuum interrupter according to embodiment 3. The difference from Figure 4 of embodiment 1 is that in Figure 7, an insulating sheet 5r is sandwiched between the bearing mounting portion 5g and the bearing 5q. The insulating sheet here is made of rubber, nylon, PTFE (POLYTETRAFLUOROETHYLENE), or the like. Also, in Figure 4 of embodiment 1, the bearing 5h is made of resin, and the bearing fixing bolt 5i is made of metal. In contrast, in Figure 7 of embodiment 3, the bearing 5q is made of metal, and the bearing fixing bolt 5s is made of an insulating material. The metal used is a non-magnetic metal such as aluminum, copper, brass, or stainless steel. The insulating material may be a thermoplastic resin such as PET (Poly Ethylene Terephthalate) or PBT (Poly Butylene Terephthalate), or a thermosetting resin such as epoxy. Other points are the same as in the case of FIG.

[0030] By making the bearing 5q a machined metal part, the dimensional accuracy is improved compared to a resin product, and the mechanical performance as a bearing and the airtightness are improved. Furthermore, even if the bearing 5q is made of metal, by sandwiching the insulating sheet 5r and further making the bearing fixing bolt 5s out of an insulating material, there is no path for current to flow in the bellows 5d, so there is no impact on the life of the bellows 5d due to current flowing in the bellows 5d.

[0031] Although the first to third embodiments have been described with reference to the case where dry air is used as the insulating gas, other insulating gases such as SF6 gas may also be used.

[0032] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0033] 1 Gas insulated switchgear, 2 Vacuum circuit breaker, 4 Main circuit section, 5 Vacuum valve, 5a Fixed side contact, 5b Movable side contact, 5c Movable electrode shaft, 5d Bellows, 5f Inner circumferential space, 5g Bearing mounting section, 5h Bearing, 5j Fixed airtight section, 5k Airtight sliding section, 5n Bearing, 5p Gas supply port, 5q Bearing, 5r Insulating sheet, 8 Sealed container.

Claims

1. A vacuum circuit breaker in which a vacuum valve is mounted inside a sealed container and a high-pressure insulating gas is sealed in the space inside the sealed container, wherein a fixed contact and a movable contact are installed inside the vacuum valve and the movable contact is connected to a movable electrode shaft, the movable electrode shaft is connected to a bellows and is supported by a bearing, the bearing is fixed to a bearing mounting part with a bolt, a fixed airtight part is provided to airtightly seal the surface where the bearing is fixed to the bearing mounting part, and the bearing is provided with an airtight sliding part to airtightly seal the sliding surface with the movable electrode shaft.

2. A vacuum circuit breaker as claimed in claim 1, wherein the pressure in the space inside the bellows is atmospheric pressure when the contacts of the vacuum valve are closed, and the pressure in the space inside the bellows increases above atmospheric pressure by the amount that the volume of the space inside the bellows decreases when the contacts of the vacuum valve are open.

3. A vacuum circuit breaker according to claim 2, wherein the inner peripheral space of the bellows is filled with air, dry air or an inert gas.

4. A vacuum circuit breaker according to any one of claims 1 to 3, wherein the bearing is made of a thermoplastic or thermosetting resin.

5. A vacuum circuit breaker according to any one of claims 1 to 3, wherein the bearing is made of metal and an insulating sheet is sandwiched between the bearing mounting portion and the bearing.

6. A method for manufacturing a vacuum circuit breaker as claimed in claim 1 or claim 2, comprising the steps of: preparing the bearing by attaching a first seal part to the groove of the fixed airtight part and attaching a second seal part to the groove of the airtight sliding part; and attaching the bearing to the movable electrode shaft with the fixed contact and the movable contact in contact in air, and fixing the bearing with a bearing fixing bolt, thereby sealing air in the inner space of the bellows.

7. A method for manufacturing a vacuum circuit breaker as claimed in claim 3, comprising the steps of: preparing the bearing with a first seal part attached to the groove of the fixed airtight part and a second seal part attached to the groove of the airtight sliding part; and attaching the bearing to the movable electrode shaft with the fixed contact and the movable contact in contact within an enclosed assembly space filled with dry air or inert gas, and fixing the bearing with bearing fixing bolts, thereby sealing dry air or inert gas in the inner space of the bellows.

8. A method for manufacturing a vacuum circuit breaker as claimed in claim 1, comprising the steps of: providing a gas supply port hole in the bearing; attaching the bearing to the movable electrode shaft; evacuating the air in the inner space of the bellows through the gas supply port; and sealing gas into the inner space through the gas supply port.

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