Switching device

Abstract

The objective of the present invention is to provide a shielded conductor with an improved insulation property and an opening / closing device using the same. An aspect of the present invention is a shielded conductor (5) serving for electric field relaxation, characterized in that the surface of the shielded conductor is covered with a resin (10) containing a nano-filler. In addition, an opening / closing device (1) according to an aspect of the present invention is characterized by comprising: a hermetic container (2); an insulating spacer (3) fixed inside the hermetic container; high-pressure conductors (4) disposed on both sides of the center of the insulating spacer; and the shielded conductors (5) attached to the high-pressure conductors on both sides and having a diameter greater than that of the high-pressure conductor, the surface of the shielded conductors being covered with the resin (10) containing the nano-filler.

Description

Technical Field

[0001] The present invention relates to a shield conductor and a switching device using the same.

Background Art

[0002] As shown in the following patent documents, a gas-insulated switching device has a structure in which a high-voltage conductor is disposed in a metal sealed container. In such a gas-insulated switching device, a solid insulator called an insulating spacer for fixing the high-voltage conductor at a predetermined position in the sealed container is used. Conventionally, the sealed container is filled with SF6 gas. A high-voltage conductor is provided at the center of the insulating spacer and supported by the insulating spacer.

[0003] And, in order to mitigate the electric field concentration at the triple junction (triple junction) of the insulating spacer, the high-voltage conductor, and the SF6 gas, shield conductors larger in diameter than the high-voltage conductor are attached to the high-voltage conductors on both sides of the insulating spacer.

Prior Art Documents

Patent Documents

[0004] [[ID=Twenty-five]] [[ID=Twenty-six]]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, since the global warming potential of SF6 gas is more than 20,000 times that of CO2, the replacement with alternative gases is being promoted. Therefore, the adoption of dry air is being promoted as one of the alternative gases.

[0006] However, the insulating properties of dry air are only about one-third of those of SF6, and the electric field strength on the surface of the shield conductor protruding from the outer surface of the high-voltage conductor became too high, becoming the starting point for dielectric breakdown.

[0007] Furthermore, as cost-effectiveness becomes more important, there is a demand for more compact switchgear. However, promoting miniaturization leads to an increasing electric field strength on the surface of the shield conductor, creating an insulating weakness.

[0008] Therefore, in view of the problems of the above-mentioned prior art, the present invention aims to provide a shield conductor with improved insulation properties and a switchgear using the same. [Means for solving the problem]

[0010] One aspect of the present invention is an opening and closing device, Filled with dry air It comprises a sealed container, an insulating spacer fixed inside the sealed container, high-voltage conductors positioned on both sides of the center of the insulating spacer, and shielding conductors attached to the high-voltage conductors on both sides, having a larger diameter than the high-voltage conductors. The shield conductor has a first side surface on the side closer to the insulating spacer, a second side surface on the side further from the insulating spacer, and an outer peripheral surface connecting the first side surface and the second side surface, the space between the first side surface and the outer peripheral surface is formed as a convex curved surface, and a gap is provided between the first side surface of the shield conductor and the insulating spacer. The shield conductor From the first side surface to the convex curved surface and the second side surface The surface is characterized by being coated with a resin containing nanofillers. [Effects of the Invention]

[0011] According to the present invention, a shield conductor with excellent insulating properties can be made. In the present invention, the shield conductor can be preferably used in a switchgear that uses dry air, and the miniaturization of the switchgear can be promoted. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view of the opening / closing device according to this embodiment. [Figure 2] This is a cross-sectional view of a conventional opening and closing device. [Modes for carrying out the invention]

[0013] The opening and closing device according to this embodiment will be described in detail below with reference to the attached drawings. It should be noted that the present invention is not limited to the embodiments described below, and can be modified as appropriate without altering its essence.

[0014] <Overview of the Opening / Closing Device 1> Figure 1 is a cross-sectional view of a switchgear 1 according to an embodiment of the present invention. As shown in Figure 1, the switchgear 1 comprises a sealed container 2, an insulating spacer 3 fixed inside the sealed container 2, high-voltage conductors 4 arranged on both sides of the center of the insulating spacer 3, and a shielding conductor 5 having a larger diameter than the high-voltage conductors 4.

[0015] [Insulating Spacer 3] The insulating spacer 3 is a solid insulator used to fix the high-voltage conductor 4 in a predetermined position within the sealed container 2, and is, for example, a cone shape as shown in Figure 1. However, the shape of the insulating spacer 3 is not limited and can be applied to various shapes, such as a disc shape, a configuration with axially symmetrical protrusions and recesses, or a configuration through which multiple (for example, three) high-voltage conductors 4 pass.

[0016] As shown in Figure 1, a metal flange 6 is attached to the outer edge of the insulating spacer 3. The metal flange 6 is sandwiched between the connecting flange 7 of the sealed container 2, and the insulating spacer 3 is fixed to the sealed container 2 by bolts 8.

[0017] The material of the insulating spacer 3 is not limited, but it is constructed by mixing an inorganic filler into a thermosetting resin. Epoxy resin is preferably used as the thermosetting resin. Furthermore, it is preferable to add at least one of the following as the inorganic filler: alumina, silica, dolomite, titanium oxide, barium titanate, and strontium titanate.

[0018] [conductor] As shown in Fig. 1, a conductor for conducting high-voltage current is attached to the central axis A of the insulating spacer 3. The conductor consists of an insulating spacer inner shield conductor 9 embedded inside the insulating spacer 3, a high-voltage conductor 4 that is integrated with the insulating spacer inner shield conductor 9 and extends and is arranged on both sides of the insulating spacer 3, and a shield conductor 5 that is arranged on both sides of the insulating spacer 3 at an intermediate position of the high-voltage conductor 4 and has a diameter d2 larger than the diameter d1 of the high-voltage conductor 4. Therefore, the shield conductor 5 protrudes in a ring shape from the outer peripheral surface of the high-voltage conductor 4. Although the protruding height of the shield conductor 5 from the outer peripheral surface of the high-voltage conductor 4 is not limited, it is about 5 mm to 30 mm. As shown in Fig. 1, the diameter d3 of the insulating spacer inner shield conductor 9 is also larger than the diameter d1 of the high-voltage conductor 4.

[0019] For example, the high-voltage conductor 4 has a first high-voltage conductor 4a located between the insulating spacer inner shield conductor 9 and the shield conductor 5, and a second high-voltage conductor 4b arranged outside the shield conductor 5 and extending in a direction away from the insulating spacer 3. The insulating spacer inner shield conductor 9 and the first high-voltage conductor 4a are integrally formed and embedded in the insulating spacer 3, and the shield conductor 5 and the second high-voltage conductor 4b can be incorporated into the first high-voltage conductor 4a, for example, by concave-convex fitting. The shield conductor 5 and the second high-voltage conductor 4b may be integrally formed or separately formed and assembled.

[0020] The materials of the insulating spacer inner shield conductor 9, the high-voltage conductor 4, and the shield conductor 5 are not limited, but for example, they are formed of aluminum (Al) or an aluminum alloy. All of the conductors can be formed of the same metal, or they can be formed of different metals according to the location and member.

[0021] The shield conductor 5 is composed of an inner surface (first surface) 5a on the side closer to the insulating spacer 3, an outer surface (second surface) 5b on the side further from the insulating spacer 3, and an outer surface 5c connecting the inner surface 5a and the outer surface 5b. The space between the inner surface 5a and the outer surface 5c is formed by a convex curved surface B1, and the space between the outer surface 5b and the outer surface 5c is formed by a convex curved surface B2. In this way, the spaces between the inner surface 5a and the outer surface 5b and the outer surface 5c are curved in a convex shape and are not sharp, thus mitigating electric field concentration.

[0022] As shown in Figure 1, a gap T1 is provided between the inner surface 5a of the shield conductor 5 and the insulating spacer 3. Although not limited to this, the gap T1 is approximately 5 mm to 30 mm in size. By setting the distance to this size, the electric field strength can be appropriately mitigated. As shown in Figure 1, in this embodiment, the surface of the shield conductor 5 is coated with a resin 10 containing nanofillers.

[0023] <Challenges of the prior art and the process leading to this embodiment> In contrast, in the conventional example shown in Figure 2, the surface of the shield conductor 5 is not coated with the resin 10 containing nanofillers, and the conductive surface of the shield conductor 5 is exposed. Note that in Figure 2, the same reference numerals as in Figure 1 indicate the same components.

[0024] In the conventional example shown in Figure 2, the sealed container 2 was filled with highly insulating SF6 gas 11. The shield conductors 5, positioned on both sides in the direction of the central axis A of the insulating spacer 3, are provided to mitigate the electric field concentration at the triple junction C where the insulating spacer 3, the high-voltage conductor 4, and the SF6 gas 11 come into contact.

[0025] Incidentally, because SF6 gas-11 has a global warming potential more than 20,000 times higher than CO2, the adoption of dry air as a substitute for SF6 gas-11 is being promoted.

[0026] However, the insulating properties of dry air are low, about one-third that of SF6 gas. As a result, the electric field strength becomes high on the surface of the shield conductor 5 shown in Figure 2, particularly on the convex curved surface B1 near the triple point C, making dielectric breakdown more likely to occur starting from this point.

[0027] Thus, the insulating properties of dry air are about one-third or less of those of SF6 gas, so it was necessary to increase the insulation distance to maintain the same level of insulation as SF6 gas. However, in recent years, there has been a demand for greater economic efficiency, and the miniaturization of switchgear has been desired, making it difficult to increase the size. Therefore, as miniaturization is promoted, the electric field strength on the convex curved surface B1 of the shield conductor 5 increases, becoming an insulating weakness.

[0028] Therefore, after diligent research, the inventors coated the surface of the shield conductor 5 with a resin 10 containing nanofillers, as shown in Figure 1. This suppressed electron emission from the convex curved surface B1 of the shield conductor 5, thereby improving the insulation properties of the shield conductor 5.

[0029] <Resin containing nanofillers 10> As shown in Figure 1, the nanofiller-containing resin 10 of this embodiment only needs to be coated on the surface of the shield conductor 5, that is, it is not necessary to coat the surface of the high-voltage conductor 4. This makes installation relatively easy. Furthermore, rather than coating only the convex curved surface B1 of the shield conductor 5 where the electric field strength is particularly high with the nanofiller-containing resin 10, coating the entire surface of the exposed shield conductor 5 with the resin 10 effectively improves the insulation of the shield conductor 5 and also offers excellent workability. For example, the shield conductor 5 can be provided separately from the high-voltage conductor 4, and the shield conductor 5 coated with the nanofiller-containing resin 10 can be incorporated into the high-voltage conductor 4. The method of application of the resin 10 is not limited, but spray painting, brush painting, or fluid immersion can be suggested.

[0030] The resin material used in the resin 10 containing nanofillers is a fluid insulating resin. The insulating resin is preferably a thermosetting resin. For example, thermosetting resins include epoxy resins, maleimide resins, cyanate resins, or mixtures thereof. Of these, epoxy resin is preferred as the thermosetting resin.

[0031] The epoxy resin preferably comprises an epoxy resin main component, a curing agent, and a curing accelerator. Of these, the curing accelerator can be arbitrarily selected. As the epoxy resin main component, an aliphatic epoxy resin, an alicyclic epoxy resin, or a mixture thereof can be used. Examples of aliphatic epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, biphenyl type epoxy resin, cresol novolac type epoxy resin, and polyfunctional epoxy resins with three or more functions, but the material is not limited to these. One of these can be used alone, or two or more can be used in mixture form.

[0032] Examples of alicyclic epoxy resins include monofunctional epoxy resins, bifunctional epoxy resins, and polyfunctional epoxy resins with three or more functions, but are not limited to these. One of these can be used alone, or two or more can be used in combination.

[0033] The curing agent for thermosetting resins is not particularly limited as long as it can react with the epoxy resin main component and cure. For example, the curing agent for thermosetting resins is an aromatic acid anhydride, specifically phthalic anhydride, pyromellitic anhydride, trimellitic anhydride, etc. Alternatively, the curing agent for thermosetting resins is a cyclic aliphatic acid anhydride, specifically tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, etc. Alternatively, the curing agent for thermosetting resins is an aliphatic acid anhydride, specifically succinic anhydride, polyadipic anhydride, polysebacic anhydride, polyazelaic anhydride, etc. Other curing agents for thermosetting resins may also be used. Furthermore, as curing accelerators, imidazole or its derivatives, tertiary amines, borate esters, Lewis acids, organometallic compounds, organic acid metal salts, etc., can be used as appropriate, but are not limited to these.

[0034] The nanofillers used in this embodiment will now be described. The nanofillers dispersed in the resin 10 may be selected in size and material to exhibit the effects of this embodiment, namely, the effect of promoting electron emission suppression and improving the insulation of the shield conductor 5. Specifically, the particle size of the nanofillers is preferably 100 nm or less, but even if it exceeds 100 nm, it will still be considered a nanofiller in this embodiment if the same effect as in this embodiment can be obtained. However, the particle size of the nanofillers is preferably 100 nm or less, more preferably 90 nm or less, and even more preferably 80 nm or less.

[0035] While not limited to this method, for example, the particle size of nanofillers can be measured by averaging the particle sizes of multiple nanofillers (preferably 10 or more) using a scanning electron microscope (SEM). In this measurement method, the particle size of a nanofiller is defined as the average of its maximum and minimum lengths. Alternatively, measurement data listed in the material manufacturer's catalog or similar document may be used. Furthermore, existing methods such as dynamic light scattering, laser diffraction, centrifugal sedimentation, FFF (Flash Fibre) method, and electrical detection methods can be applied to measure the particle size of nanofillers.

[0036] The nanofiller may have a cross-section other than circular, for example, elliptical or other irregular shapes. In any case, the particle size of the nanofiller shall be measured according to the above procedure.

[0037] Nanofillers are inorganic fillers, and specifically, one or more of the following can be selected: silica (SiO2), alumina (Al2O3), boron nitride (BN), titanium dioxide (TiO2), strontium titanate (SrTiO3), and barium titanate (BaTiO3). Of these, silica, alumina, titanium dioxide, or barium titanate are preferably selected as nanofillers.

[0038] While not limited to this, the nanofiller is mixed into the resin 10 at a volume percentage of approximately 5% or less. More specifically, it is mixed at a volume percentage of approximately 0.05% to 3%. This allows the nanofiller to be appropriately dispersed in the resin 10 and to exhibit high insulating properties.

[0039] Furthermore, the resin 10 may contain not only nanofillers, but also sub-micro (sometimes called "semi-micro") fillers with a larger particle size than nanofillers, and microfillers with a larger particle size than sub-microfillers, taking into consideration workability during coating and mechanical properties. The particle size of the sub-microfillers is 100 nm to 1 μm, preferably 200 nm to less than 1 μm. The particle size of the microfillers is 1 μm or larger. It is preferable to adjust the total amount of nanofillers, sub-microfillers, and microfillers to 50% by volume or less.

[0040] In this embodiment, the composition of the coating resin 10 can be appropriately determined by the operator, using the above-mentioned thermosetting resin main agent, curing agent, curing accelerator, and inorganic filler such as nanofiller, so that the physical properties such as dielectric constant and heat resistance achieve the desired values.

[0041] While not limited to this, the thickness of the resin 10 is approximately several tens of micrometers to 100 micrometers. By forming the resin 10 within this thickness range, both workability and insulation properties can be improved.

[0042] <Shielded conductor 5 coated with resin 10 containing nanofillers> The shield conductor 5 of this embodiment is applied, for example, to a switchgear 1 shown in Figure 1, and is used for electric field mitigation. As shown in Figure 1, in the switchgear 1, an insulating spacer 3 is fixedly supported inside a sealed container 2, and a high-voltage conductor 4 is attached to the center of the insulating spacer 3. Then, a shield conductor 5 with a larger diameter than the high-voltage conductor 4 is provided on each of the high-voltage conductors 4 located on both sides of the insulating spacer 3. In this configuration of use, the electric field strength becomes high on the convex curved surface B1 of the shield conductor 5 that protrudes from the outer surface of the high-voltage conductor 4 and is close to the insulating spacer 3, making it prone to becoming the starting point for dielectric breakdown.

[0043] Therefore, in this embodiment, the surface of the shield conductor 5 is coated with a resin 10 containing nanofillers. This suppresses electron emission at the convex curved surface B1, which is the starting point of dielectric breakdown, and allows for high insulation performance.

[0044] <Flashover test> Incidentally, the present inventors verified the flashover characteristics using a reference example in which nanofillers and microfillers were added to the insulating spacer 3, and a comparative example in which microfillers were added but no nanofillers were added. They found that the flashover characteristics could be improved in the reference example with nanofillers added compared to the comparative example. The nanofillers used in the experiment are shown in Table 1 below.

[0045] [Table 1]

[0046] In both the reference example and the comparative example, 47% by volume of a microfiller consisting of SiO2 was added. In the reference example, an additional 1% by volume of the nanofiller shown in Table 1 was added relative to the microfiller. The average particle size of the SiO2 nanofillers shown in Table 1 was 50 nm. The average particle size of the TiO2 nanofillers shown in Table 1 was 40 nm. The average particle size of the SrTiO3 nanofillers shown in Table 1 was 70 nm. The average particle size of the SiO2 microfillers was 1.5 μm.

[0047] The test method is as described in "Surface Flashover Characteristics of Gas Insulated Switchgear Spacer Model Using Novel Functional Insulating Materials" (IEEJ Dielectric Insulating Materials Research Group Manuscript: Paper No. DEI-19-116). The experimental results of the flashover characteristics using a single-shot application method are shown in Table 2 below.

[0048] [Table 2]

[0049] Table 2 shows "V" 63.2 " is the value at which the probability of FOV occurrence is 63.2%, determined from the Weibull distribution of the flashover instantaneous voltage measured as FOV in an experiment using a single-shot application method.

[0050] The parentheses in Table 2 indicate the V of the comparative example. 63.2 This shows the rate of increase. As shown in Table 2, an improvement in FOV was observed in all reference examples compared to the comparative examples.

[0051] The improvement in field of view (FOV) achieved by including nanofillers is predicted to be based on the formation of deep trap levels due to the addition of nanoparticles, as determined by quantum chemical calculations.

[0052] In this embodiment, a shield conductor 5 is provided, which increases the electric field strength of the convex curved surface of the shield conductor. For this reason, the inventors coated the surface of the shield conductor 5 with a resin 10 containing nanofillers so that an electron emission suppression effect based on deep electron trapping due to the addition of nanoparticles can be obtained on the surface of the shield conductor.

[0053] In this embodiment, in order to further enhance the electron emission suppression effect, it is preferable to coat the surface of the shield conductor with a resin containing nanofillers and to also add nanofillers to the insulating spacer 3.

[0054] <Switching device 1 having a shield conductor 5 coated with resin 10> In this embodiment, the opening / closing device 1 is preferably configured such that the sealed container 2 is filled with dry air 12, and gases with a high global warming potential, such as SF6 gas, are not used.

[0055] In this embodiment, even with a configuration using dry air 12, coating the surface of the shield conductor 5 with a resin 10 containing nanofillers suppresses electron emission at the convex curved surface B1, which is the starting point of dielectric breakdown, thereby improving the reduction in insulation performance. In addition, even if the switchgear 1 is made more compact, the reduction in dielectric breakdown voltage due to the compactness can be improved.

[0056] As described above, in the switchgear 1 of this embodiment, the insulating properties of the shield conductor 5 can be improved even when using dry air and by miniaturizing the device, and a switchgear 1 that can be made more compact can be provided without using gases with a high global warming potential such as SF6 gas.

[0057] This application is based on Japanese Patent Application No. 2022-141863, filed on September 7, 2022. All of its contents are included here. [Industrial applicability]

[0058] The shield conductor of the present invention can improve insulation and can be effectively applied to applications that provide electric field mitigation. By applying the shield conductor to a switchgear, a compact switchgear that uses dry air can be realized. [Explanation of symbols]

[0059] 1: Switching device 2: Sealed container 3: Insulating spacer 4: High-voltage conductor 4a: First high-voltage conductor 4b: Second high-voltage conductor 5: Shield conductor 5a: Inside surface 5b: Outer surface 5c: Outer surface 6: Metal flange 7: Connecting flange 8: Bolt 9: Shield conductor inside insulating spacer 11: SF6 gas 12: Dry air A: Central axis B1, B2: Convex curved surface T1: Gap

Claims

1. A sealed container filled with dry air, An insulating spacer fixed inside the sealed container, The high-voltage conductors are arranged on both sides of the center of the insulating spacer, It is configured to have a shield conductor attached to both sides of the high-voltage conductor and having a larger diameter than the high-voltage conductor, The shield conductor has a first side surface on the side closer to the insulating spacer, a second side surface on the side further from the insulating spacer, and an outer peripheral surface connecting the first side surface and the second side surface, and the space between the first side surface, the second side surface and the outer peripheral surface is formed as a convex curved surface. A gap is provided between the first side surface of the shield conductor and the insulating spacer. A switching device characterized in that the surface of the shield conductor, from the first side surface to the convex curved surface and the second side surface, is coated with a resin containing nanofillers.

2. The opening and closing device according to claim 1, characterized in that the nanofiller is selected from one or more of silica, alumina, boron nitride, titanium oxide, strontium titanate, and barium titanate.

3. The switchgear according to claim 1 or 2, characterized in that the surface of the shield conductor is coated with the resin containing nanofillers having an average particle size of 100 nm or less and microfillers having an average particle size of 1 μm or more.

Images