Gas-insulated switchgear

Abstract

To improve a withstand voltage while facilitating manufacture.SOLUTION: A gas-insulated switchgear (1) comprises a conductor (4) held by an insulating spacer (3) in a sealed container (2) filled with an insulating gas. An insulating layer (20) is provided on the surface of the curved conductor in the conductor. The insulating layer is formed by laminating an insulating material on the surface of the curved conductor by a thermal spraying method or an aerosol deposition method. Ceramic particles (21) are used as the insulating material. The insulating layer is impregnated with an insulating resin (22).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gas-insulated switchgear in which a conductor is disposed within a container. [Background technology]

[0002] Patent Document 1 discloses a gas-insulated busbar to which a high voltage is applied by a conductor placed in a metal container filled with insulating gas. In Patent Document 1, a dielectric coating layer is formed on the surface of the conductor using epoxy resin to a thickness equal to or greater than the surface roughness, and the irregularities of the micro-projections formed on the surface of the conductor are coated with a dielectric to suppress field emission electrons from the micro-projections and improve the withstand voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-224120 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the conductor is formed by casting or the like, the roughness of the conductor surface increases, making it difficult to cover the tips of the micro-projections with a coating of a certain thickness, which results in problems such as insufficient suppression of field emission electrons and a decrease in withstand voltage.Furthermore, there is also the problem that repeated coating is required to increase the thickness of the coating, which increases the number of steps.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a gas-insulated switchgear that can be easily manufactured and has an improved withstand voltage. [Means for solving the problem]

[0006] The gas-insulated switchgear of the present invention is a gas-insulated switchgear having a conductor held by an insulating spacer in a container filled with an insulating gas, characterized in that an insulating layer is provided on the surface of the conductor, and the insulating layer is formed by layering an insulating material on the surface of the conductor by a thermal spraying method or an aerosol deposition method. [Effects of the Invention]

[0007] According to the present invention, the insulating layer is formed by laminating layers using a thermal spraying method or an aerosol deposition method, so that the insulating layer can be formed thickly with a small number of steps. This not only simplifies manufacturing, but also, even if the conductor has a high surface roughness, it is possible to cover the minute protrusions on the surface and prevent electron emission into the insulating gas, thereby improving the withstand voltage. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a gas-insulated switchgear according to an embodiment. [Figure 2] FIG. 2 is a partially enlarged cross-sectional view of the front surface side of the curved conductor. [Figure 3] FIG. 3 is a further enlarged cross-sectional view of a part of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a gas-insulated switchgear according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following embodiment, and can be implemented by appropriate modifications within the scope of the present invention. For the sake of convenience, some components may be omitted in the following drawings.

[0010] Fig. 1 is a cross-sectional view of a gas-insulated switchgear according to an embodiment. As shown in Fig. 1, the gas-insulated switchgear 1 includes a sealed container 2 (container), an insulating spacer 3 fixed inside the sealed container 2, and a conductor 4 held by the insulating spacer 3 inside the sealed container 2.

[0011] In this embodiment, the sealed container 2 is formed into a shape that allows the axial direction of the cylindrical member to be changed as needed, and in the portion shown in Figure 1, the axis changes direction by 90° while curving in an arc. The inside of the sealed container 2 is filled with an insulating gas. Examples of insulating gases include dry air, which is a naturally occurring gas, a synthetic gas of N2 and O2, and a synthetic gas of CO2 and O2, and are sealed at a pressure of 0.1 MPa-abs or more.

[0012] A flange 6 is provided on the outer periphery of the insulating spacer 3, and the flange 6 is made of, for example, metal. The flange 6 is sandwiched between a connecting flange 7 of the sealed container 2 and fastened with bolts 8 and nuts 9, thereby fixing the insulating spacer 3 to the sealed container 2.

[0013] The insulating spacer 3 includes an axially shaped central conductor 11 and a spacer body 12 that supports the central conductor 11 and is disposed around the central conductor 11. In this embodiment, the spacer body 12 is formed in a cone shape with one surface along the axial direction of the central conductor 11 being convex and the other surface being concave. In the insulating spacer 3, the spacer body 12 supports the central conductor 11 at the center position of the sealed container 2. Note that the shape of the spacer body 12 is not limited to a cone shape, and may be other shapes such as a disk shape with both surfaces in the thickness direction being approximately smooth.

[0014] The central conductor 11 is formed in a roughly cylindrical shape, and the ends of the conductors 4 are connected to both the left and right ends in Fig. 1 via a screw structure or the like. The conductors 4 are held by the insulating spacers 3 via this connection.

[0015] The conductor 4 is formed by processing a metal such as aluminum, copper, or iron. The conductor 4 of this embodiment includes three linear conductors 14 extending in a straight line and one curved conductor 15 having a portion where its axis turns 90° and extends in a curved direction. The linear conductors 14 are formed by, for example, drawing or cutting, and in FIG. 1 , they have portions extending in the left and right directions from both the left and right sides of the central conductor 11 and a portion extending in the up and down direction away from the insulating spacer 3. The curved conductor 15 is formed by, for example, casting, and connects the linear conductor 14 extending from the right side of the central conductor 11 with the linear conductor 14 extending in the up and down direction.

[0016] Here, an insulating layer 20 is provided on the surface of the curved conductor 15 of the conductor 4 by plasma spraying (thermal spraying).

[0017] 2 is a partially enlarged cross-sectional view of the surface side of the curved conductor 15, and is an explanatory diagram of a method for forming the insulating layer 20. As shown in FIG. 2, the insulating layer 20 is formed by layering an insulating material, for example, ceramic particles 21, on the surface of the curved conductor 15 by a plasma spraying method. In this plasma spraying method, the ceramic particles 21 are melted into a liquid state by high-temperature plasma and ejected at high speed from a nozzle N, and the ceramic particles 21 are sprayed onto the surface of the curved conductor 15. As a result of this spraying, the melted ceramic particles 21 collide with the surface of the curved conductor 15 at high speed and are instantly cooled and fixed upon collision, thereby forming the insulating layer 20 in a layer or film shape.

[0018] By forming the insulating layer 20 by plasma spraying in this way, it is possible to form the insulating layer 20 to a predetermined thickness in a single continuous process without repeating lamination or painting processes multiple times. For example, it is possible to form the insulating layer 20 to a thickness of about 100 μm to 3 mm in a single spraying process. In other words, in this embodiment, the insulating layer 20 can be formed thicker with fewer steps than painting.

[0019] The surface of the linear conductor 14 is formed by drawing or cutting, and is formed to include protrusions and irregularities with a maximum height Ry of, for example, 1 to 20 μm, resulting in a relatively small surface roughness. On the other hand, the surface of the curved conductor 15 may include protrusions and irregularities with a maximum height Ry exceeding 20 μm, resulting in a larger surface roughness than the surface of the linear conductor 14, and may form small protrusions that are more likely to emit electrons. Even in such cases, as shown in Figure 2, a sufficiently thick insulating layer 20 can be formed on the tips of the small protrusions by plasma spraying. The maximum height Ry is an index defined in JIS B0601.

[0020] Therefore, the insulating layer 20 of this embodiment can be formed with a small number of steps by thermal spraying so as to cover the tips of the microprotrusions on the surface of the curved conductor 15 with a sufficient thickness. This reduces the number of steps compared to forming an insulating coating by painting to have the same thickness as the insulating layer 20, and ultimately simplifies manufacturing. Moreover, because the insulating layer 20 is formed with a sufficient thickness even at the tips of the microprotrusions on the surface of the curved conductor 15, it is possible to suppress the emission of electrons that are the starting point for dielectric breakdown, and improve the withstand voltage.

[0021] As the thermal spraying method, plasma spraying is usually used, but high-velocity flame spraying, gas flame spraying, arc spraying, etc. can also be used. For example, high-velocity flame spraying creates a supersonic jet of combustion gas, melts and accelerates the ceramic particles 21, causing them to collide with the surface of the curved conductor 15, solidifying and depositing the ceramic particles 21 to form a laminate, thereby forming the insulating layer 20.

[0022] The ceramic particles 21 used in the thermal spraying method can be one or more selected from alumina particles, silica, boron nitride, titanium oxide, strontium titanate, and barium titanate. By using these, it is possible to better suppress the emission of electrons that cause dielectric breakdown.

[0023] In forming the insulating layer 20, an aerosol deposition method may be used instead of the thermal spraying method.

[0024] In the aerosol deposition method, ceramic particles 21 are mixed with gas to form an aerosol, which is then sprayed onto a target through a nozzle (not shown) to form (deposit) an insulating layer 20. Helium or air is used as the gas. In the aerosol deposition method, an apparatus (not shown) consisting of an aerosolization chamber and a deposition chamber is used. The deposition chamber is depressurized to 50 Pa to 1 kPa using a vacuum pump. The ceramic particles 21 are aerosolized in a dry state by being stirred and mixed with gas in the aerosolization chamber. The aerosolized ceramic particles 21 are then transported to the deposition chamber by a gas flow caused by the pressure difference between the aerosolization chamber and the deposition chamber. They are then accelerated as they pass through the nozzle. The gas-transported ceramic particles 21 are accelerated to several hundred meters per second as they pass through the nozzle in the depressurized deposition chamber and are sprayed onto the surface of the curved conductor 15.

[0025] The ceramic particles 21 are mechanically pulverized to a particle size of approximately 5 nm to 1 μm. The film formation speed and density of the insulating layer 20 depend greatly on the particle size, agglomeration state, dryness, etc. of the ceramic particles 21 used. For this reason, a particle disintegrator and classifier are installed between the aerosolization chamber and the film formation chamber to maintain a predetermined agglomeration state and dryness.

[0026] Ceramic particles 21 sprayed from the nozzle collide with the surface of the curved conductor 15 at high speed and deposit, forming an insulating layer 20 that will become a ceramic layer. Ceramic particles 21 with a particle size of up to about several tens of nanometers are crushed and deformed to sizes of about 0.5 nm to 20 nm by the impact of the collision, and the crushed pieces with activated surfaces bond together to form an insulating layer 20 that will become a dense ceramic layer. The aerosol deposition method can be performed at room temperature.

[0027] Figure 3 is a further enlarged cross-sectional view of a portion of Figure 2. As shown in Figure 3, the insulating layer 20 is made by melting ceramic particles 21 and depositing them at high speed, which can leave microscopic gaps S at the interface between the particles. To eliminate such gaps S and further improve insulation, the insulating layer 20 is impregnated with insulating resin 22.

[0028] The insulating layer 20 can be impregnated with the insulating resin 22 by immersing the curved conductor 15 on which the insulating layer 20 is formed in a storage tank (not shown) that stores liquid insulating resin 22, or by brushing the insulating resin 22 onto the curved conductor 15, thereby impregnating the insulating resin 22 into the gap S. When immersing the curved conductor 15 in a storage tank that stores insulating resin 22, the impregnation can be improved by placing the entire tank in a vacuum container and reducing the pressure.

[0029] Specifically, the insulating resin 22 to be impregnated may be a thermosetting resin, such as an epoxy resin, a maleimide resin, a cyanate resin, or a mixture thereof. The thermosetting resin is preferably an epoxy resin. The epoxy resin preferably contains an epoxy resin base, a curing agent, and, optionally, a curing accelerator. The epoxy resin base may be an aliphatic epoxy, an alicyclic epoxy, or a mixture thereof. Examples of aliphatic epoxy resins include, but are not limited to, bisphenol A epoxy, bisphenol F epoxy, bisphenol AD ​​epoxy, biphenyl epoxy, cresol novolac epoxy, and trifunctional or higher polyfunctional epoxy. These may be used alone or in combination. Examples of alicyclic epoxy resins include, but are not limited to, monofunctional epoxy, bifunctional epoxy, and trifunctional or higher polyfunctional epoxy. The alicyclic epoxy resin may also be used alone or in combination.

[0030] The curing agent for the thermosetting resin is not particularly limited as long as it can react with the epoxy resin base and cure. Examples include aromatic acid anhydrides, specifically phthalic anhydride, pyromellitic anhydride, trimellitic anhydride, etc. Alternatively, alicyclic acid anhydrides, specifically tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, etc., or aliphatic acid anhydrides, specifically succinic anhydride, polyadipic anhydride, polysebacic anhydride, polyazelaic anhydride, etc., can be used, but are not particularly limited. Furthermore, curing accelerators that can be used include imidazole or its derivatives, tertiary amines, boric acid esters, Lewis acids, organometallic compounds, organic acid metal salts, etc., but are not particularly limited.

[0031] Furthermore, the insulating properties can be further improved by adding (filling) nanofiller particles to the insulating resin 22 to be impregnated. The nanofiller particles added to the insulating resin 22 can be one or more selected from alumina particles with a diameter of 500 nm or less, silica, boron nitride, titanium oxide, strontium titanate, and barium titanate. By using these, it is possible to better suppress the emission of electrons that are the starting point for dielectric breakdown. By adding nanofillers, the emission of electrons that are the starting point for dielectric breakdown is suppressed, thereby improving the deterioration of insulating properties.

[0032] In the gas-insulated switchgear 1, for example, SF6 gas can be used as the insulating gas. However, in recent years, SF6 gas has a global warming potential more than 20,000 times that of CO2, so alternative gases have been promoted, and among these, the adoption of naturally occurring gases such as dry air, synthetic gas of N2 and O2, and synthetic gas of CO2 and O2 has been promoted. However, the breakdown voltage of the above naturally occurring gases is about one-third that of SF6 gas, resulting in reduced insulation performance.

[0033] If an insulating layer were to be formed on the surface of the curved conductor 15 by painting instead of the insulating layer 20, it would be difficult to coat the tips of the microprotrusions on the surface with a consistent thickness. Therefore, if a naturally occurring gas with a low breakdown voltage were used as the insulating gas, electrons would be emitted from the microprotrusions into the insulating gas, triggering a discharge and reducing the withstand voltage. A low withstand voltage would require a long insulation distance between the curved conductor 15 and the wall of the sealed container, as well as between the conductors, which would result in an increase in the size of the entire gas-insulated switchgear, including the sealed container.

[0034] In this regard, in the present embodiment, the insulating layer 20 is formed on the surface of the curved conductor 15 by the above-mentioned thermal spraying method or the like, and the tips of the minute protrusions can be covered with the insulating layer 20 having a thickness of about 100 μm to 3 mm in one continuous process. This not only makes it possible to form a thick insulating layer 20 with fewer steps than painting, but also makes it possible to suppress electron emission from the minute protrusions, avoiding a decrease in withstand voltage, and suppressing an increase in the size of the entire gas-insulated switchgear 1 including the sealed container 2.

[0035] An insulating layer 14a is also formed on the surface of the straight conductor 14 of the conductor 4. The insulating layer 14a formed on the straight conductor 14 may be formed by painting or by a thermal spraying method or the like, as with the insulating layer 20, as long as it can exhibit insulating performance similar to that of the insulating layer 20 formed on the curved conductor 15. Since the straight conductor 14 has a smaller maximum height Ry than the curved conductor 15, the method for forming the insulating layer 14a can be selected taking into consideration manufacturing costs and insulating performance.

[0036] The present invention is not limited to the above-described embodiment, and various modifications can be made to the embodiment. In the above-described embodiment, the size, shape, orientation, etc. shown in the accompanying drawings are not limited to these, and can be modified as appropriate within the scope of the effects of the present invention. In addition, the present invention can be modified as appropriate without departing from the scope of the object of the present invention.

[0037] For example, the conductor on which the insulating layer 20 is formed in the gas-insulated switchgear 1 is not limited to a cast conductor, but may be a conductor whose surface roughness is increased by a molding method other than casting, or a conductor whose surface roughness is smaller than that of a cast conductor.

[0038] Furthermore, the insulating material used to laminate the insulating layer 20 may be particles other than the ceramic particles 21, as long as it exhibits insulating properties similar to those of the ceramic particles 21 and can be laminated by thermal spraying or aerosol deposition.

[0039] Furthermore, if the gap S (see Figure 3) can be made extremely small by stacking the insulating layer 20 using the thermal spraying method or the aerosol deposition method, and insulating performance can be achieved, the impregnation of the insulating resin 22 or the addition of nanofiller particles to the insulating resin 22 may be omitted.

[0040] Furthermore, the number of conductors 4 and central conductors 11 is not limited to one each, and may be changed to a plurality (for example, three). [Explanation of symbols]

[0041] 1: Gas insulated switchgear 2: Sealed container (container) 3: Insulating spacer 4: conductor 20: Insulating layer 21: Ceramic particles 22: Insulating resin

Claims

1. 1. A gas-insulated switchgear comprising a conductor held by an insulating spacer in a container filled with an insulating gas, a gas-insulated switchgear, characterized in that an insulating layer is provided on the surface of the conductor, and the insulating layer is formed by laminating an insulating material on the surface of the conductor by a thermal spraying method or an aerosol deposition method.

2. 2. The gas-insulated switchgear according to claim 1, wherein the insulating material is made of ceramic particles.

3. 3. The gas-insulated switchgear according to claim 2, wherein the ceramic particles are made of one or more kinds selected from the group consisting of alumina particles, silica, boron nitride, titanium oxide, strontium titanate, and barium titanate.

4. 4. The gas-insulated switchgear according to claim 1, wherein the insulating layer is impregnated with an insulating resin.

5. 5. The gas-insulated switchgear according to claim 4, wherein nano-filler particles are added to the insulating resin.

6. 6. The gas-insulated switchgear according to claim 5, wherein the nano-filler particles are one or more selected from the group consisting of alumina particles, silica, boron nitride, titanium oxide, strontium titanate, and barium titanate.

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