Insulating spacer
The cone-shaped insulating spacer with graded permittivity addresses electric field concentration at the triple point, improving insulation reliability and enabling compact gas-insulated switchgear design.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- FUJI ELECTRIC CO LTD
- Filing Date
- 2024-12-26
- Publication Date
- 2026-07-08
AI Technical Summary
Conventional insulating spacers face challenges in reducing electric field strength near the triple point, hindering insulation reliability and compactness, especially with the transition from SF6 to lower-insulating gases like dry air.
The insulating spacer features a cone-shaped design with varying relative permittivity in its concave and convex surfaces, gradually decreasing or maintaining constant permittivity to reduce electric field concentration at the triple point.
This design effectively reduces electric field strength, enhancing insulation reliability and enabling compact gas-insulated switchgear without increasing size.
Smart Images
Figure 2026113958000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an insulating spacer.
Background Art
[0002] Patent Document 1 discloses a conical insulating spacer that is fixed inside a grounded tank filled with an insulating gas and partitions the inside of the grounded tank. The insulating spacer of Patent Document 1 consists of a through-conductor and an insulator. Since such an insulating spacer is required to have high withstand voltage characteristics, mitigation of electric field concentration in the vicinity of the triple point between the insulator, the insulating gas, and the through-conductor or the grounded tank is required.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In Patent Document 1, the insulator of the insulating spacer consists of a plurality of layers having different dielectric constants. The plurality of layers having different dielectric constants are sequentially laminated in descending order of dielectric constant from the through-conductor toward the grounded tank, aiming to maintain insulation reliability while achieving compactness of the gas-insulated equipment. However, in the insulating spacer, there was room for improvement in reducing the electric field strength in the vicinity of the above-described triple point in order to maintain good insulation reliability.
[0005] The present invention has been made in view of such circumstances, and an object thereof is to provide an insulating spacer capable of maintaining good insulation reliability.
Means for Solving the Problems
[0006] An insulating spacer according to one aspect of the present invention is an insulating spacer comprising a cone-shaped spacer body that supports a central conductor and is provided around the central conductor, and whose axial direction is the same as that of the central conductor, wherein the spacer body comprises a concave side forming portion that forms a concave surface of the cone shape and a convex side forming portion that forms a convex surface of the cone shape, wherein the relative permittivity of the concave side forming portion is set to gradually decrease from the central conductor side toward the middle portion in the inclination direction of the cone shape, and the relative permittivity is kept constant from the middle portion toward the outer edge, and the relative permittivity of the convex side forming portion is kept constant from the central conductor side toward the middle portion, and the relative permittivity is set to gradually increase from the middle portion toward the outer edge. [Effects of the Invention]
[0007] According to the present invention, it is possible to reduce the electric field strength near the triple point between the spacer body, the insulating gas, and the central conductor, and to maintain good insulation reliability. [Brief explanation of the drawing]
[0008] [Figure 1] This is a cross-sectional view of an opening / closing device according to an embodiment. [Figure 2] This diagram shows a conceptual model of the area around the insulating spacer. [Figure 3] Figure 3A is an explanatory diagram of the change in relative permittivity in the insulating spacer of Example 1, and Figure 3B is an explanatory diagram of the change in relative permittivity in the insulating spacer of Example 2. [Figure 4] Figure 4A is an explanatory diagram of the relative permittivity in the insulating spacer of Comparative Example 1, and Figure 4B is an explanatory diagram of the change in relative permittivity in the insulating spacer of Comparative Example 2. [Figure 5] This graph shows the analysis results of the electric field strength for each example and comparative example. [Modes for carrying out the invention]
[0009] Before describing embodiments of the present invention, the background leading to these embodiments will be explained. Conventional gas-insulated switchgear is known to have a structure in which a high-voltage conductor is placed inside a sealed metal container. In such gas-insulated switchgear, a solid insulator called an insulating spacer is used to fix the high-voltage conductor in a predetermined position within the sealed container.
[0010] Conventionally, in commonly used disc-shaped insulating spacers, a high-voltage conductor is provided in the center, and the insulating spacer is provided to support the high-voltage conductor. A metal flange is attached around the insulating spacer, and the metal flange allows it to be sandwiched between the connecting flanges of the sealed container and fixed to the sealed container.
[0011] In recent years, with increasing demands for economic efficiency, there has been a desire for more compact gas-insulated switchgear. In conventional insulating spacers, the difference in dielectric constant between the insulating gas (primarily SF6) and the solid insulator hinders miniaturization due to electric field concentration in the gas space. Therefore, to achieve miniaturization, studies are being conducted to reduce the creepage electric field component on the surface of a cone-shaped insulating spacer by changing its dielectric constant in the axial direction. However, because SF6 has a very high global warming potential (GWP) of 25300, it is now beginning to be replaced by compressed air (dry air, synthetic air) that does not contain any SF6. In this case, the insulating properties are about 30% lower than those of SF6, which actually makes the equipment larger, so there is a need to prevent such an increase in size.
[0012] In such cone-shaped insulating spacers, an insulator is used whose dielectric constant is graded so that it decreases from the part in contact with the high-voltage conductor toward the ground side. Such insulating spacers also need to be made more compact, and further improvements are required to reduce the electric field strength at the interface between the insulator and the insulating gas.
[0013] Hereinafter, a gas-insulated switchgear (hereinafter simply referred to as "switchgear") using an insulating spacer according to an embodiment of the present invention will be described in detail 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 implemented with appropriate modifications without changing its essence. In the following figures, some components may be omitted for the sake of clarity.
[0014] Figure 1 is a cross-sectional view of a switchgear according to an embodiment. As shown in Figure 1, the switchgear 1 comprises a sealed container 2, an insulating spacer 3 fixed inside the sealed container 2, and high-voltage conductors 4 (shown by dashed lines) arranged on both sides of the center of the insulating spacer 3. The sealed container 2 is filled with an insulating gas G, such as dry air or SF6 gas.
[0015] A metal flange 6 is attached to the outer edge of the insulating spacer 3, and the insulating spacer 3 is fixed to the sealed container 2 by being sandwiched between the metal flange 6 and the connecting flange 7 of the sealed container 2.
[0016] The insulating spacer 3 comprises a central conductor 11 formed in an axial shape and a spacer body 12 that supports the central conductor 11 and is provided around the central conductor 11. The spacer body 12 is formed in a cone shape (conical shape) with the same axis A direction as the central conductor 11. Axis A is defined as the central axis position of the central conductor 11 and the spacer body 12, and the extension direction of the central axis and the axis A direction are synonymous. In Figure 1, a cross-sectional view is shown with a plane parallel to axis A and through which axis A passes.
[0017] The spacer body 12 is formed in a cone shape, so that one surface is a convex surface C and the other surface is a concave surface R in the direction of axis A. The spacer body 12 has tapered surfaces on the concave surface R and the convex surface C. In this specification and the claims, "inclination direction" means the direction of extension between the central conductor 11 side and the outer peripheral edge 12a side of the tapered surface of the spacer body 12 when viewed in cross-section as shown in Figure 1.
[0018] Note that the shapes of the illustrated central conductor 11 and spacer body 12 are merely schematically illustrated for ease of understanding, and dimensions such as those in the axial A direction, radial direction, inclination direction, and thickness may be appropriately changed. Further, although the insulating spacer 3 has been illustrated with a single-phase configuration, the configuration of the present embodiment can be applied to a three-phase integrated insulating spacer. In a three-phase integrated insulating spacer, the central conductor 11 is changed to three, and the through portions of each of the three central conductors 11 in the spacer body 12 are formed in a conical shape.
[0019] The spacer body 12 includes a concave-side forming portion 13 that forms a conical concave surface R and a convex-side forming portion 14 that forms a conical convex surface C. The concave-side forming portion 13 forms a predetermined thickness range from the concave surface R toward the convex surface C while including the concave surface R in the spacer body 12. The convex-side forming portion 14 forms a predetermined thickness range from the convex surface C toward the concave surface R while including the convex surface C in the spacer body 12. The concave-side forming portion 13 and the convex-side forming portion 14 may be adjacent within the thickness of the spacer body 12, or at least one intermediate forming portion or the like may be provided between them and they may be spaced apart.
[0020] Here, the spacer body 12 has a relative permittivity that gives a predetermined electric field strength distribution in the concave-side forming portion 13 and the convex-side forming portion 14. In setting such a relative permittivity, modeling was performed as shown in FIG. 2 and analysis was carried out.
[0021] FIG. 2 is a diagram showing a conceptual model around the insulating spacer. In the model of FIG. 2, a cross section of a half region from the axis A around the insulating spacer 3 is illustrated, and the outline of the portion corresponding to the conical spacer body 12 is represented by a solid line. The left end of the spacer body 12 in FIG. 2 extends linearly in the vertical direction, and the region to the left of the left end is a high-voltage region HV to which a predetermined voltage is applied corresponding to the central conductor 11 and the high-voltage conductor 4. The outer peripheral edge 12a (right end in FIG. 2) of the spacer body 12 also extends linearly in the vertical direction, and the region to the right of the outer peripheral edge 12a is a ground potential region GND that is set to a ground potential corresponding to the sealed container 2.
[0022] Furthermore, the spacer body 12 is divided in the cross-section through which the central axis (axis A) of the cone shape in Figure 2 passes by a virtual inclination direction boundary S located midway in the inclination direction, and a virtual thickness direction boundary T located midway between the concave surface R and the convex surface C. More specifically, the spacer body 12 is formed including first to fourth regions 21 to 24, which are divided by the virtual inclination direction boundary S and the virtual thickness direction boundary T.
[0023] In the direction of axis A, the ratio of the distance from the virtual thickness direction boundary T to the concave surface R of the spacer body 12 and the distance from the virtual thickness direction boundary T to the convex surface C is set to h1:h2. While the h1:h2 ratio is exemplified by being set to 1:1 at the position shown in Figure 2, various changes are possible, such as setting it to 4:1.
[0024] Furthermore, at the position of the virtual inclination direction boundary S shown in Figure 2, it is set at the midpoint between the interface between the spacer body 12 and the central conductor 11 and the outer edge 12a in the inclination direction. Therefore, in the left-right direction in Figure 2 (radial direction of the spacer body 12), the ratio r1:r2, which is the distance from the virtual inclination direction boundary S to the outer surface of the high-voltage conductor 4 and the distance from the virtual inclination direction boundary S to the inner surface of the sealed container 2, is set to 1:1. However, the virtual inclination direction boundary S can be shifted towards the central conductor 11 side or the outer edge 12a side. Note that the virtual inclination direction boundary S and the virtual thickness direction boundary T are virtual positions for specifying the range in which the relative permittivity is set, as will be described later, and the formation of an interface is not necessarily required.
[0025] The first region 21 forms the concave R side in the direction of axis A and the central conductor 11 side in the direction of inclination, within the region divided by each boundary S and T. The second region 22 forms the concave R side in the direction of axis A and the outer edge 12a side in the direction of inclination, within the region divided by each boundary S and T. The third region 23 forms the convex C side in the direction of axis A and the outer edge 12a side in the direction of inclination, within the region divided by each boundary S and T. The fourth region 24 forms the convex C side in the direction of axis A and the central conductor 11 side in the direction of inclination, within the region divided by each boundary S and T.
[0026] The first region 21 and the third region 23 of the spacer body 12 are configured such that the relative permittivity changes (tilts) in the direction of inclination. In Figure 2 and Figures 3 and 4 described later, the relative change in relative permittivity is represented by shades of gray for ease of understanding, indicating that the relative permittivity is higher in the darker regions compared to the lighter regions.
[0027] In the first region 21, the relative permittivity is higher in the region closer to the central conductor 11, which is represented in a darker color, compared to the region closer to the virtual slope direction boundary S, which is represented in a lighter color. Therefore, the first region 21 is configured such that the relative permittivity is gradually set lower from the central conductor 11 (high voltage region HV) side toward the virtual slope direction boundary S.
[0028] In the third region 23, the relative permittivity is higher in the region closer to the outer edge 12a of the spacer body 12, which is shown in a dark color, compared to the region closer to the virtual slope direction boundary S, which is shown in a light color. Therefore, the third region 23 is configured such that the relative permittivity is gradually set lower from the outer edge 12a (ground potential region GND) towards the virtual slope direction boundary S.
[0029] The second region 22 and the fourth region 24 are configured to be white (the color of the paper) with no change in shade in Figure 2, and their relative permittivity remains constant. The relative permittivity of the second region 22 is set to be constant, equal to the relative permittivity of the virtual slope direction boundary S in the first region 21. The relative permittivity of the fourth region 24 is set to be constant, equal to the relative permittivity of the virtual slope direction boundary S in the third region 23.
[0030] By setting the relative permittivity of the first to fourth regions 21-24 as described above, the relative permittivity of the concave R side of the spacer body 12 is relatively higher than that of the convex C side, on the side of the central conductor 11. Furthermore, the relative permittivity of the convex C side of the outer edge 12a of the spacer body 12 is relatively higher than that of the concave R side.
[0031] In the model of the insulating spacer 3 shown in Figure 2, the concave side forming portion 13 can be formed by the first region 21 and the second region 22, and the convex side forming portion 14 can be formed by the third region 23 and the fourth region 24. Therefore, in the spacer body 12, the relative permittivity of the concave side forming portion 13 is set to gradually decrease from the central conductor 11 side toward the virtual slope direction boundary S, which is the intermediate part in the slope direction, and the relative permittivity is kept constant from the virtual slope direction boundary S toward the outer edge. Similarly, the relative permittivity of the convex side forming portion 14 is kept constant from the central conductor 11 side toward the virtual slope direction boundary S, which is the intermediate part in the slope direction, and the relative permittivity is set to gradually increase from the virtual slope direction boundary S toward the outer edge 12a.
[0032] Here, with respect to the model in Figure 2, it can be illustrated that, in the configuration of the insulating spacer 3 in Figure 1, the positions indicated by the dashed lines on the spacer body 12 are the virtual slope direction boundary S and the virtual thickness direction boundary T. The spacer body 12 can then be formed to include the first to fourth regions 21 to 24, which are separated by the virtual slope direction boundary S and the virtual thickness direction boundary T. Therefore, in the spacer body 12 of Figure 1, the first region 21 and the second region 22 can form the concave side forming portion 13, and the third region 23 and the fourth region 24 can form the convex side forming portion 14.
[0033] As an example of a method for manufacturing the insulating spacer 3, the manufacturing method disclosed in Japanese Patent Application Publication No. 2024-31901 can be cited. In this manufacturing method, the spacer body 12 is formed comprising a grid portion formed in a three-dimensional mesh shape and a solid portion disposed in a solid state within the internal space of the grid portion. The solid portion is formed by injecting insulating resin into the internal space of the grid portion, and the relative permittivity of the solid portion is considerably lower than that of the grid portion. Therefore, by changing the ratio of the grid portion and the solid portion per unit volume in the spacer body 12, the relative permittivity of the concave side forming portion 13 and the convex side forming portion 14 can be changed as described above.
[0034] Another example of a method for manufacturing the insulating spacer 3 is the manufacturing method disclosed in Japanese Patent Application Publication No. 2024-31261. In this manufacturing method, a cone-shaped spacer body 12 is formed by winding a tape-shaped prepreg around a central conductor 11. The prepreg before winding is formed by coating and impregnating the nonwoven fabric with an insulating resin containing a filler using a coater or the like. The insulating resin is in a fluid or semi-cured state when wound and can be composed of a thermosetting resin containing a filler.
[0035] Furthermore, the composition and amount of the filler contained in the thermosetting resin are adjusted so that the tape-shaped prepreg before winding forms a region in which the relative permittivity of the spacer body 12 increases, decreases or becomes constant as described above. In the spacer body 12 formed into a cone shape by winding such prepreg, the relative permittivity of the concave side forming portion 13 and the convex side forming portion 14 can be changed as described above.
[0036] Another example of a manufacturing method for the insulating spacer 3 is a manufacturing method in which the spacer body 12 is fabricated using a three-dimensional molding device. A three-dimensional molding device is a device also called a 3D printer, which fabricates a three-dimensional object by stacking cross-sectional shapes based on 3D data. The fabrication method of the three-dimensional molding device may be any of the following methods: fused deposition modeling, which fabricates by injecting resin material from a nozzle and stacking it; or stereolithography, which hardens liquid resin with ultraviolet light. By adjusting the data structure of the 3D data, the relative permittivity of the concave side forming portion 13 and the convex side forming portion 14 of the spacer body 12 can be changed as described above. [Examples]
[0037] Next, Examples 1 and 2, in which various conditions of the configuration in the above embodiment were set and electric field analysis was performed, and Comparative Examples 1 and 2 for comparison, will be described below with reference to Figures 3 and 4.
[0038] Figure 3A is an explanatory diagram of the change in relative permittivity in the insulating spacer of Example 1, and Figure 3B is an explanatory diagram of the change in relative permittivity in the insulating spacer of Example 2. Figure 4A is an explanatory diagram of the relative permittivity in the insulating spacer of Comparative Example 1, and Figure 4B is an explanatory diagram of the change in relative permittivity in the insulating spacer of Comparative Example 2. In Figures 3A, 3B, 4A, and 4B, the spacer body 12, modeled in the same manner as in Figure 2, is shown, and below it, a graph showing the relationship between the position of the spacer body 12 in the tilt direction and the relative permittivity is shown. In the graphs in each figure, the horizontal axis is the position of the spacer body 12 in the tilt direction, and the vertical axis is the relative permittivity ε r In addition, in the models of Comparative Examples 1 and 2 in Figures 4A and 4B, the same reference numerals are used for the components corresponding to each embodiment.
[0039] [Example 1] In the first embodiment shown in Figure 3A, the spacer body 12 has a relative permittivity that is varied (graded) in the first region 21 and the third region 23, similar to the configuration shown in Figure 2 in the above embodiment. The maximum value of this relative permittivity was set to 12 and the minimum value to 4. In the second region 22 and the fourth region 24, the relative permittivity was kept constant at 4.
[0040] In Example 1, the distance r from the outer surface of the high-voltage conductor 4 of the spacer body 12 to the inner surface of the sealed container 2 was set to 65 mm, and the position of the virtual slope direction boundary S was set so that r1:r2 was 1:1. In addition, the thickness t of the spacer body 12 in the axis A direction was set to 65 mm, 85 mm, and 105 mm, and the position of the virtual thickness direction boundary T was set so that h1:h2 was 1:1. 100 kV was applied between the high-voltage region HV and the ground potential region GND.
[0041] Since the electric field strength is particularly high in the elliptical area represented by the dashed line in Figure 2, the analysis points P1 and P2 shown in Figure 2 were chosen to perform the electric field strength analysis. More specifically, analysis point P1 is located at a distance d in the direction of axis A from the triple point where the concave surface R of the spacer body 12, the insulating gas G, and the high-voltage region HV overlap, while the concave surface R of the spacer body 12 forms an acute angle with the high-voltage region HV. Analysis point P2 is located at a distance d in the direction of axis A from the triple point where the convex surface C of the spacer body 12, the insulating gas G, and the ground potential region GND overlap, while the convex surface C of the spacer body 12 forms an acute angle with the ground potential region GND. At each analysis point P1 and P2, the distance d was set to 1 mm while approaching the triple point where the electric field strength is maximum, in order to obtain stable analysis results.
[0042] Under the above conditions, a general three-dimensional electric field analysis was performed using the finite element method (FEM) as an example to determine the electric field relaxation effect. The electric field analysis using the finite element method can be performed, for example, using commercially available simulation software. Figure 5 shows the analysis results of the electric field strength at each analysis point P1 and P2 when the thickness t is set to 65 mm, 85 mm, and 105 mm.
[0043] [Example 2] In Example 2, shown in Figure 3B, the spacer body 12 is modified from Example 1 by changing the position of the virtual thickness direction boundary T, so that h1:h2 is set to 4:1, while all other conditions are the same as in Example 1. Figure 5 shows the results of the electric field strength analysis in graph form.
[0044] [Comparative Example 1] Comparative Example 1, shown in Figure 4A, differs from Example 1 in that the relative permittivity of the spacer body 12 is changed. In Comparative Example 1, the relative permittivity is kept constant at 4 in all of the first to fourth regions 21-24, and all other conditions are the same as in Example 1. Figure 5 shows the results of the electric field strength analysis in a graph.
[0045] [Comparative Example 2] Comparative Example 2, shown in Figure 4B, differs from Example 1 in that the relative permittivity of the second region 22 and the fourth region 24 in the spacer body 12 is varied (graded). In Comparative Example 2, the relative permittivity of the second region 22 is set to gradually decrease toward the virtual gradation direction boundary S, similar to the third region 23. In Comparative Example 2, the relative permittivity of the fourth region 24 is set to gradually decrease toward the virtual gradation direction boundary S, similar to the first region 21. In both the second region 22 and the fourth region 24 of Comparative Example 2, the maximum value of the relative permittivity was set to 12 and the minimum value to 4. All other conditions were the same as in Example 1. Figure 5 shows the analysis results of the electric field strength in a graph.
[0046] Figure 5 is a graph showing the analysis results of the electric field strength for each example and comparative example. As shown in the graph in Figure 5, it was confirmed that Example 1, compared to Comparative Example 1, provides an electric field relaxation effect of approximately 8.3% at analysis point P1 (thickness t: 105 mm) and approximately 4.0% at analysis point P2 (thickness t: 65 mm). Furthermore, it was confirmed that Example 1, compared to Comparative Example 1, provides an electric field relaxation effect of approximately 11.9% at analysis point P2 (thickness t: 105 mm) and approximately 3.6% at analysis point P2 (thickness t: 65 mm).
[0047] In Example 1, compared to Comparative Example 2, it was confirmed that a maximum electric field relaxation effect of approximately 7.2% (thickness t: 105 mm) and a minimum of approximately 0.5% (thickness t: 65 mm) could be obtained at analysis point P1. Furthermore, in Example 1, compared to Comparative Example 2, it was confirmed that a maximum electric field relaxation effect of approximately 15.2% (thickness t: 105 mm) and a minimum of approximately 4.3% (thickness t: 65 mm) could be obtained at analysis point P2.
[0048] From the analysis results above, it was found that by setting the relative permittivity of the spacer body 12 as in Example 1, it is possible to exhibit dielectric breakdown resistance in an insulating gas and maintain good insulation reliability compared to each comparative example. In particular, it was confirmed that a better electric field relaxation effect can be obtained as the thickness t of the spacer body 12 increases.
[0049] In Example 2, at analysis point P1, compared to Comparative Example 1, a maximum electric field relaxation effect of approximately 16.4% (thickness t: 105 mm) and a minimum of approximately 13.3% (thickness t: 65 mm) was obtained, and compared to Comparative Example 2, a maximum electric field relaxation effect of approximately 15.4% (thickness t: 105 mm) and a minimum of approximately 10.1% (thickness t: 65 mm) was obtained.
[0050] On the other hand, in Example 2, at analysis point P2, the electric field strength increased by approximately 8.4% to 11.6% compared to Comparative Example 1, and by approximately 4.5% to 10.7% compared to Comparative Example 2.
[0051] From the analysis results above, by setting the relative permittivity of the spacer body 12 as in Example 2, it is possible to exhibit dielectric breakdown resistance in the insulating gas at analysis point P1 and maintain good insulation reliability compared to each of the comparative examples. At analysis point P2, the electric field strength is lower in each of the comparative examples than in Example 2. However, in Example 2, the electric field strength at analysis point P1 can be significantly reduced compared to each of the comparative examples, and when the potential applied to the central conductor 11 is the same, the electric field at analysis point P1 is generally higher than at analysis point P2. Therefore, the need to lower the electric field at analysis point P1, which is on the high voltage (HV) side, is greater than at analysis point P2, which is on the ground potential (GND) side. Thus, in an overall evaluation, Example 2 is able to exhibit dielectric breakdown resistance in the insulating gas and maintain good insulation reliability compared to each of the comparative examples.
[0052] It should be noted that the present invention is not limited to the above embodiments and examples, and can be implemented with various modifications. In the above embodiments, the size, shape, orientation, etc., shown in the accompanying drawings are not limited, and can be appropriately modified within the scope that allows the present invention to exert its effects. Furthermore, it can be implemented with appropriate modifications as long as it does not deviate from the scope of the objectives of the present invention.
[0053] In the above embodiment, the case in which the electric field analysis is performed using the finite element method was described. However, the analysis method is not limited to a specific method, and for example, the electric field analysis may be performed using methods such as the difference method or the surface charge method.
[0054] Furthermore, the relative permittivity ε of Examples 1 and 2 r The above-mentioned values for thickness t and distance r are merely examples and may be changed as appropriate depending on various conditions. [Explanation of Symbols]
[0055] 3: Insulating spacer 11: Central conductor 12: Spacer body 12a: Outer edge 13: Concave side forming part 14: Convex side forming part 21:First area 22:Second area 23:Third area 24: 4th area A: Axis C: Convex R: Concave S: Virtual slope direction boundary T: Virtual thickness direction boundary
Claims
1. An insulating spacer comprising a cone-shaped spacer body that supports a central conductor and is provided around the central conductor, with the axial direction being the same as that of the central conductor, The spacer body comprises a concave side forming portion that forms the cone-shaped concave surface and a convex side forming portion that forms the cone-shaped convex surface. The aforementioned concave side forming portion has a relative permittivity that gradually decreases from the central conductor side toward the intermediate portion in the inclination direction of the cone shape, and the relative permittivity remains constant from the intermediate portion toward the outer edge. The aforementioned convex side forming portion is characterized in that the relative permittivity is constant from the central conductor side to the intermediate portion, and the relative permittivity is gradually set to increase from the intermediate portion toward the outer peripheral edge side.
2. In the spacer body, the central conductor side has a relatively higher relative permittivity on the concave side than on the convex side. The insulating spacer according to claim 1, characterized in that the outer peripheral edge of the spacer body has a relatively higher relative permittivity on the convex side than on the concave side.
3. The spacer body is formed to include first to fourth regions, which are divided in a cross-section through which the central axis of the cone shape passes by a virtual inclination direction boundary located midway in the inclination direction and a virtual thickness direction boundary located midway between the concave surface and the convex surface. The first region is formed with the concave side in the axial direction and the central conductor side in the inclination direction, and the relative permittivity is set to gradually decrease from the central conductor side toward the virtual inclination direction boundary. The second region forms the concave side in the axial direction and the outer peripheral edge side in the inclination direction, and its relative permittivity is constant at the relative permittivity of the virtual inclination direction boundary in the first region. The third region has a convex side in the axial direction and an outer peripheral edge side in the inclination direction, and the relative permittivity is set to gradually decrease from the outer peripheral edge side toward the virtual inclination direction boundary. The insulating spacer according to claim 1 or 2, characterized in that the fourth region forms the convex side in the axial direction and the central conductor side in the inclination direction, and the relative permittivity is constant at the relative permittivity of the virtual inclination direction boundary in the third region.
4. The insulating spacer according to claim 3, characterized in that the ratio of the distance from the virtual thickness direction boundary to the concave surface and the distance from the virtual thickness direction boundary to the convex surface is set to 4:1 in the axial direction.
5. The insulating spacer according to claim 3, characterized in that the ratio of the distance from the virtual thickness direction boundary to the concave surface and the distance from the virtual thickness direction boundary to the convex surface is set to 1:1 in the axial direction.