JP2010232016A - Insulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulator excellent in resistance to heat, an ultraviolet ray, chemicals, and the like, and having a high isolation voltage. <P>SOLUTION: The insulator 1 includes a dielectric part formed mainly of two ceramics with different dielectric constants, wherein a part of the dielectric part having a low dielectric constant lower than 15 is a low dielectric part 2, a part of the dielectric part having a high dielectric constant no less than 15 is a high dielectric part 3, and the low dielectric part 2 and the high dielectric part 3 are unified by sintering. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an insulator mainly composed of ceramics, which is used as an insulating support of a gas insulating device, an insulating member of a cable connection portion, or the like.

  The downsizing of high-voltage equipment, which has been strongly demanded in recent years, has a problem that an electric field rises inside the equipment, and an insulator used in the high-voltage equipment is exposed to a high electric field. In particular, the triple junction is a portion where three substances having different dielectric constants, an insulator, a conductor, and an insulating medium intersect, and an electric field concentrates when a sharp portion is formed in shape. Due to this electric field concentration, the withstand voltage performance of a high-voltage device may be significantly reduced, and sometimes a functional failure such as dielectric breakdown may occur.

  In order to alleviate electric field concentration at a triple junction or the like, conventionally, three types of insulators or insulation devices described below have been considered.

  First, there is an insulating device in which an electric field relaxation electrode is arranged in order to reduce electric field concentration. The electric field relaxation electrode is also called a shield or a buried electrode. In the insulating device in which the electric field relaxation electrode is arranged, the distance between the phases and the ground is widened, and there is a demerit that the high voltage device using this insulating device is enlarged.

  Second, there is an insulator with a low dielectric constant. In general, an insulator having a low dielectric constant is made of an organic insulating material made of an epoxy resin having a low dielectric constant, as shown in Patent Documents 1 and 2. In the insulating device provided with the insulator having a low dielectric constant, the size of the device can be prevented from being increased.

  Thirdly, in order to alleviate electric field concentration, there is an insulator in which insulating members having different dielectric constants are arranged at appropriate locations according to the generated electric field and these are joined. In Patent Document 3, in an insulating fixture that supports a high-voltage charging unit, an insulating part having a high dielectric constant mainly composed of epoxy disposed around a buried metal and disposed at a specific position around the insulating part. Also disclosed is a solid insulator composed of an insulating portion mainly composed of epoxy and having a low dielectric constant. Patent Document 4 discloses an insulating spacer used for a gas insulating device, in which an epoxy resin including a high dielectric constant member such as glass, carbon, or aramid is disposed and exposed to an insulating medium such as a gas. An arrangement in which an insulating portion made of an epoxy resin and having a low dielectric constant is disposed. With these insulating fixtures and insulating spacers, the withstand voltage drop due to electric field distortion and imbalance is prevented, and the electric field relaxation performance and withstand voltage performance are satisfactorily exhibited without increasing the size of the insulator.

  Furthermore, the insulating member made of an epoxy resin, which is also used in the insulators of Patent Documents 1 to 4, is excellent in moldability and easy to adjust the dielectric constant by mixing with an inorganic filler.

Japanese Patent Laid-Open No. 4-130126 Japanese Patent Laid-Open No. 5-198208 JP-A-6-84419 JP-A-11-262143

  However, the organic insulating materials made of epoxy or the like disclosed in Patent Documents 1 to 4 have a drawback in that they are likely to be modified or deformed by heat, ultraviolet rays, chemicals, or the like.

  In addition, the organic insulating material has a disadvantage that the ideal breakdown electric field strength is small and the withstand voltage is low as compared with inorganic insulating materials such as ceramics. Because of these difficulties in the ideal breakdown electric field strength and dielectric strength, organic insulating materials are also used for each insulating member when the insulating members having different dielectric constants are joined to reduce the electric field as shown in Patent Documents 3 and 4. The selection range of the dielectric constant and the arrangement becomes narrow. Specifically, in organic insulating materials, from the viewpoint of ideal breakdown electric field strength and withstand voltage, since it is limited to reduce the dielectric constant ratio between the two insulating members, a large electric field relaxation effect, that is, high It is difficult to obtain withstand voltage performance.

  In view of the above problems, an object of the present invention is to provide an insulator having a simple shape and a high withstand voltage without increasing the size, and further, resistance to heat, ultraviolet rays, chemicals, and the like. It is to provide an excellent insulator.

  In order to solve the above-mentioned problems, the present inventors have made extensive studies on various insulator materials, and as a result, two or more members mainly composed of ceramics having different dielectric constants are integrated by sintering. An insulator was found and the present invention was completed. That is, according to the present invention, the following insulator is provided.

[1] A dielectric part mainly composed of two ceramics having different dielectric constants, and among the dielectric parts, those having a low dielectric constant less than a dielectric constant of 15 are defined as low dielectric parts, and have a dielectric constant of 15 or more. An insulator having a high dielectric constant as a high dielectric portion, wherein the low dielectric portion and the high dielectric portion are integrated by sintering.

[2] The insulator according to [1], wherein a dielectric constant of the high dielectric portion is 3 to 20 times that of the low dielectric portion.

[3] The [1] or [1], wherein the high dielectric portion includes at least one selected from the group consisting of barium titanate, lead titanate, copper oxide, tin oxide, silicon carbide, lithium niobate, and lead niobate. The insulator according to [2].

[4] A conductor contact surface that contacts a conductor to which a high voltage is applied, a ground contact surface that contacts a ground portion, and an insulating medium contact surface that contacts an insulating medium, and the low dielectric portion includes: An insulating medium contact surface is formed, and the high dielectric portion is arranged such that a boundary between the high dielectric portion and the low dielectric portion is along the insulating medium contact surface. The insulator according to crab.

  In the insulator of the present invention, by using an inorganic insulating material such as ceramics for two different insulating materials, it is possible to obtain a large dielectric constant ratio which has been difficult with an organic insulating material. Furthermore, in the insulator of the present invention, the likelihood that a high-dielectric constant member can be placed inside an insulator made of a low-dielectric constant member has been expanded, thereby reducing the concentration of the electric field and reducing the electric field strength at the triple junction. Therefore, the withstand voltage performance can be improved, or the device including the insulator can be downsized. In addition, since the insulator of the present invention is an inorganic insulating material, it can be provided with excellent resistance to heat, ultraviolet rays, chemicals, and the like.

It is a perspective view of the insulator which is one Embodiment of this invention, and is a figure which showed the boundary of the low dielectric part and the high dielectric part transparently, and showed with the broken line. FIG. 2 is a perspective view schematically illustrating a state in which the insulator of FIG. 1 is provided between a conductor and a grounding portion. FIG. 3 is a partial cross-sectional view of the A-A ′ cross section shown in FIG. 2, and is a view showing a state in which a conductor and a grounding portion are connected to a conductor contact surface and a ground contact surface, respectively. It is a figure for demonstrating the relationship between the thickness Z of the high dielectric part along the direction from a conductor to a grounding part, and the electric field strength in a triple junction part. It is a figure for demonstrating the relationship between the distance r of a triple junction part and a high dielectric part, and the electric field strength in a triple junction part. It is a figure for demonstrating the relationship between the width | variety D of the high dielectric part in the direction parallel to a conductor contact surface, and the electric field strength in a triple junction part. It is a perspective view of the insulator which is one Embodiment of this invention, and is a figure which showed the boundary of the low dielectric part and the high dielectric part transparently, and showed with the broken line. FIG. 8 is a partial cross-sectional view of the A-A ′ cross section shown in FIG. 7, showing the conductor contact surface and the ground contact surface connected to the conductor and the ground portion, respectively. 5 is a perspective view of an insulator having a uniform dielectric constant in Comparative Example 1. FIG. FIG. 10 is a partial cross-sectional view of the A-A ′ cross section shown in FIG. 9, showing the conductor contact surface and the ground contact surface connected to the conductor and the ground portion, respectively. 6 is a diagram illustrating a potential distribution in an insulator according to Example 1. FIG. 6 is a diagram illustrating an electric field distribution in the insulator of Example 1. FIG. 6 is a diagram illustrating a potential distribution in an insulator of Comparative Example 1. FIG. 6 is a diagram illustrating an electric field distribution in an insulator of Comparative Example 1. FIG. 6 is a diagram illustrating a potential distribution in an insulator of Comparative Example 2. FIG. 6 is a diagram illustrating an electric field distribution in an insulator of Comparative Example 2. FIG. 10 is a diagram illustrating a potential distribution in an insulator of Comparative Example 3. FIG. It is a figure showing the electric field distribution in the insulator of the comparative example 3. It is a graph which compares the intensity | strength of the electric field in the triple junction part about the insulator of Example 1 and Comparative Examples 1-3. It is a graph showing the intensity | strength of the electric field on the insulating-medium contact surface in each position along the direction from a conductor to a grounding part about the insulator of Example 1 and Comparative Examples 1-3. 6 is a diagram illustrating a potential distribution in an insulator of Example 2. FIG. 6 is a diagram illustrating an electric field distribution in an insulator of Example 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the present invention.

1. Insulator:
1-1. Basic embodiment of the insulator of the present invention:
FIG. 1 is a perspective view of an insulator 1 belonging to the technical scope of the present invention. The insulator 1 of the present invention is composed of a low dielectric portion 2 and a high dielectric portion 3 which are made of ceramics as main components and have different dielectric constants by sintering. The high dielectric portion 3 has a dielectric constant of 15 or more, and the low dielectric portion 2 has a dielectric constant of less than 15. In this specification, the dielectric constants of the low dielectric part 2 and the high dielectric part 3 are described as being high or low. This is because the dielectric constant of the low dielectric part 2 and the dielectric constant of the high dielectric part 3 are Note that this is a relative evaluation when comparing.

  The term “integrated by sintering” as used herein refers to ceramic powder that is a raw material of ceramics that is a main component of the low dielectric part 2 at the boundary 21 where the low dielectric part 2 and the high dielectric part 3 are in contact with each other; It means that the ceramic powder, which is the raw material of the ceramic, which is the main component of the high dielectric part 3, is bonded by sintering, and the bond between the low dielectric part 2 and the high dielectric part 2 is maintained.

  In addition, the low dielectric portion 2 and the high dielectric portion 3 are bonded to such a degree that the low dielectric portion 2 and the high dielectric portion 2 can be sufficiently bonded to be used as the insulator 1 by such sintering. The inclusion of ceramics is used as a criterion of “mainly ceramics”.

  The insulator 1 according to the present invention has both a low dielectric portion 2 and a high dielectric portion 3 constituting the same as ceramics as a main component. Therefore, compared with the insulator 1 made of an organic material typified by epoxy resin, There is little deterioration by UV, chemicals and chemicals.

  Due to the integration by sintering, the low dielectric portion 2 and the high dielectric portion 3 of the insulator 1 of the present invention are directly coupled. Therefore, in the insulator 1 of the present invention, other members that can affect the electric field, such as an adhesive, can be excluded from the connection between the low dielectric portion 2 and the high dielectric portion 3. Therefore, in the insulator 1 of the present invention, when designing the electric field, the dielectric constants of the low dielectric portion 2 and the high dielectric portion 3 may be simply taken into account, and those skilled in the art can easily design the electric field by simulation. Applicable to. In addition, about a simulation, one specific example is described in detail in an Example.

  The insulator 1 shown in FIG. 1 has a form in which the high dielectric portion 3 is embedded in the low dielectric portion 2. However, in the insulator 1 according to the present invention, the insulating medium contact is performed according to the specifications of the insulator 1. A part of the surface 13 may be formed from the high dielectric portion 3. Even in such a form, the optimal arrangement of the low dielectric portion 2 and the high dielectric portion 3 can be found by simulation.

  As long as the insulator 1 of the present invention includes the above-described basic embodiment, the shape, size, and the like can be freely designed according to the application. Next, a preferred embodiment of the insulator 1 of the present invention will be described while explaining specific forms regarding the dielectric constant, components, and the like.

1-2. Permittivity ratio between low and high dielectric parts:
In the insulator 1 of the present invention, the dielectric constant of the high dielectric portion 3 is preferably 3 to 20 times that of the low dielectric portion. Since the effect of alleviating the concentration of the electric field is increased by increasing the ratio of the dielectric constant, the insulator 1 of the present invention has the uniform and low dielectric constant shown in Patent Documents 1 and 2 in the triple junction portion 61 and the like. An electric field relaxation effect superior to that of an insulating material can be realized.

1-3. Low dielectric component:
The ceramic that is the main component of the low dielectric part 2 may be any ceramic as long as the dielectric constant of the low dielectric part 2 is less than 15 and the low dielectric part 2 and the high dielectric part 3 are integrated by sintering.

  Examples of the ceramic as the main component of the low dielectric portion 2 include various glasses, alumina, mullite, zirconia, aluminum nitride, silicon nitride, silicon carbide, cordierite, and the like. Further, the low dielectric portion 2 may include a plurality of ceramics listed here.

1-4. Components of high dielectric part:
The ceramic that is the main component of the high dielectric part 3 may be any ceramic that achieves integration by sintering the low dielectric part 2 and the high dielectric part 3 with a dielectric constant of the high dielectric part 3 of 15 or more.

  Examples of the ceramic that is the main component of the high dielectric portion 3 include various glasses, alumina, mullite, zirconia, aluminum nitride, silicon nitride, silicon carbide, cordierite, and the like. The high dielectric portion 3 may include a plurality of ceramics listed here.

  Further, the high dielectric portion 3 includes at least one selected from the group consisting of barium titanate, lead titanate, copper oxide, tin oxide, silicon carbide, lithium niobate, and lead niobate in order to increase the dielectric constant. It is preferable. The selection and amount of the components listed here can be set in accordance with the dielectric constant of the high dielectric portion 3 and the type of ceramic as the main component.

1-5. Embodiment as insulator provided between conductor and ground:
FIG. 2 schematically shows a state where the insulator 1 of the present invention shown in FIG. 1 is provided between a conductor 31 to which a high voltage is applied and a grounding portion 32. Thus, the insulator 1 of the present invention can be used as an insulating support that supports the space between the conductor 31 and the grounding portion 32. The insulating support is also called an insulator, a spacer, a bushing or the like.

  When the insulator 1 of the present invention is used as an insulating support as shown in FIG. 2, the following surface is defined for the surface of the insulator 1.

  Referring to FIG. 1 and FIG. 2, among the surfaces of the insulator 1 of the present invention, the surface that contacts the conductor 31 is the conductor contact surface 11, the surface that contacts the grounding portion 32 is the ground contact surface 12, and is insulated. The surface in contact with the medium is an insulating medium contact surface 13.

  Of the surface of the insulator 1 according to the present invention, the intersection of the conductor contact surface 11 and the insulating medium contact surface 13 is defined as an intersection 14.

  FIG. 3 shows a part of the A-A ′ cross section shown in FIG. 2. When the insulator 1 is connected to the conductor 31 and the ground part 32, the intersection part 14 corresponds to a so-called triple junction part 61 where three substances having different dielectric constants, the insulator 1, the conductor 31, and the insulating medium 33 intersect. . In the triple junction 61, as shown in FIG. 3, the electric field concentrates when the insulator 1 and the conductor 31 form an acute angle with the insulating medium 33 interposed therebetween.

  In the insulator 1 of the present invention, it is preferable that the low dielectric portion 2 forms the insulating medium contact surface 13. At this time, it is preferable that the high dielectric portion 3 is provided in a shape and an arrangement so as to alleviate electric field concentration on the insulating medium contact surface 13, particularly the triple junction portion 61.

1-6. Advantages of the insulator of the present invention:
Although the breakdown voltage of an insulating medium is difficult to compare unambiguously due to various factors, the ideal breakdown electric field of an inorganic insulating material such as alumina is generally said to be 1000 kV / mm. The ideal breakdown electric field of the organic insulating material is said to be 100 kV / mm. Since the insulator 1 of the present invention is composed only of an inorganic insulating material mainly composed of ceramic, it is considered to be difficult with an organic insulating material, and is large between the low dielectric portion 2 and the high dielectric portion 3. The setting of the dielectric constant ratio and the special arrangement in which the high dielectric portion 3 is placed close to the triple junction portion 61 are possible. The advantages of the insulator 1 of the present invention resulting from the inorganic insulating material will be described in detail using simulations in the examples.

2. Insulator manufacturing method:
As the method for manufacturing the insulator 1 of the present invention, various conventionally known methods can be adopted. Examples include injection molding, slip casting, cold isostatic pressing, slurry dip, doctor blade method, and gel casting method.

  In the gel casting method, a molded body is formed by preparing a slurry containing at least a ceramic powder, a dispersion medium, and a gelling agent, and then casting the slurry into a molding space inside the molding die to cause gelation. Further, this is a method for producing a ceramic product by firing the compact. The gel cast method can cope with a combination of the low dielectric portion 2 and the high dielectric portion 3 in a complicated shape, and a defect occurs at the boundary 21 between the integrated low dielectric portion 2 and the high dielectric portion 3. There are also difficult advantages. For example, the gel casting method is described in detail in JP-A No. 2001-335371.

  For example, the insulator 1 of the present invention can be manufactured by a manufacturing method using a gel casting method described below.

2-1. Overview of gel casting and firing:
In one embodiment of the method of manufacturing an insulator using the gel cast method, a molding die that can take a mold of the low dielectric portion 2 and a molding die that can take a die having a shape in which the low dielectric portion 2 and the high dielectric portion 3 are integrated. prepare.

  First, the slurry for the low dielectric part 2 is cast and gelled in the molding space of the molding die where the mold of the low dielectric part 2 can be taken to produce a molded body that is the basis of the low dielectric part 2.

  Next, a molded body that is the basis of the previously formed low dielectric portion 2 is placed in a predetermined place in the molding space of the molding die in which the die having the shape in which the low dielectric portion 2 and the high dielectric portion 3 are integrated can be obtained. Then, a slurry for the high dielectric portion 3 is cast and gelled in the remaining molding space, so that a molded body for the insulator 1 including the low dielectric portion 2 and the high dielectric portion 3 is produced.

  Subsequently, by firing this molded body, a ceramic powder that is a raw material of ceramics that is a main component of the low dielectric portion 2 and a ceramic powder that is a raw material of ceramics that is the main component of the high dielectric portion 3 are bounded 21. In this case, the low dielectric portion 2 and the high dielectric portion 3 are integrated by sintering.

  When the low dielectric part 2 and the high dielectric part 3 are joined with a complex shape boundary 21, two or more molding dies are prepared, and the molded bodies of the low dielectric part 2 and the high dielectric part 3 are prepared. A method of forming a molded body for the insulator 1 including the low dielectric portion 2 and the high dielectric portion 3 by partially forming and performing the partial molding stepwise can be employed.

  When the high dielectric portion 3 is formed from a plurality of regions 41 having different dielectric constants, the same method as the molding of the low dielectric portion 2 and the high dielectric portion 3 described above may be applied. That is, a slurry corresponding to the dielectric constant of each region 41 is prepared, and a molding die that can take the shape of each region 41 is prepared and molded in stages.

2-2. slurry:
The slurry for forming the low dielectric part 2 and the high dielectric part 3 is prepared by mixing ceramic powder, a dispersant, a binder and the like.

  The slurry for forming the low dielectric part 2 and the high dielectric part 3 is prepared from ceramic powder, a dispersant, a gelling agent, etc., and the dielectric constant is adjusted by adding an inorganic filler as appropriate. While doing.

  In the gel casting method as described above, since a molding die is used, the dimensional error of each part can be reduced. Further, since the low dielectric portion 2 and the high dielectric portion 3 are integrated in a desired shape and arrangement at the time of the molded body, the low dielectric portion 2 and the high dielectric portion 3 are surely integrated by sintering. Turn into.

  In this method of manufacturing the insulator 1, after firing, the low dielectric portion 2 or the high dielectric portion 3 can be trimmed to a shape suitable for alleviating electric field concentration.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

3-1. Study of relaxation of electric field concentration at triple junction by simulation:
Here, an example of simulation assuming the truncated cone-shaped insulator 1 shown in FIG. 1 will be described. The high dielectric portion 3 has a cylindrical shape in which both ends of a perfect circular cross section are open, and both ends along the cylindrical axis 19 of the high dielectric portion 3 are parallel to each other. Such a high dielectric portion 3 is embedded in the low dielectric portion 2 with the cylindrical shaft 19 of the high dielectric portion 3 aligned with the frustoconical shaft 20 of the insulator 1, and one end of the high dielectric portion 3 is embedded. The part appears on the conductor contact surface 11. Therefore, the conductor contact surface 11 of the insulator 1 is concentrically formed around the shafts 19 and 20, and has a low dielectric portion 2 at the center, a high dielectric portion 3 at the middle, and a low dielectric portion 2 at the outer periphery.

  FIG. 3 is a cross section of the insulator 1 connected to the conductor 31 and the grounding portion 32, which represents a part of the AA ′ cross section in FIGS. 1 and 2, and is cut to include the shafts 19 and 20. ing. In this truncated cone-shaped insulator 1, since the conductor contact surface 11 is small and the ground contact surface 32 is large, the conductor 31 and the insulating medium contact surface 13 have an acute angle. Therefore, in the insulator 1 shown in this figure, the intersection portion 14 where the conductor contact surface 11 and the insulating medium contact surface 13 intersect is the triple junction portion 61 where the three elements (electrode) conductor-insulator creepage-insulating medium contact. In this case, when a high voltage is applied to the conductor 31, the electric field tends to concentrate.

  Of the end portions of the high dielectric portion 3, the end portion closest to the triple junction portion 61, in other words, the end portion closest to the intersection portion 14 is defined as an intersection side end portion 30. In the insulator 1 shown in FIG. 3, the intersection-side end 30 is on the conductor contact surface 11.

  In summary, in the insulator 1 shown in FIGS. 1 to 3, the low dielectric portion 2 forms the insulating medium contact surface 13. Further, the high dielectric part 3 is arranged so that the boundary 21 between the low dielectric part 2 and the high dielectric part 3 is along the insulating medium contact surface 13. More specifically, the high dielectric portion 3 is arranged in the vicinity of the intersection portion 14, that is, in the vicinity of the triple junction portion 61, at the boundary 21 a formed from the intersection side end 30 of the high dielectric portion 3 toward the ground portion 32. Along the insulating medium contact surface 13.

  In the insulator 1 of the above-described form, the simulation result when the dielectric constant ratio between the low dielectric portion 2 and the high dielectric portion 3 is 10 and the insulating medium is evacuated is shown as 3 in the shape and arrangement of the high dielectric portion 3. Focusing on one parameter, explanation will be made with reference to the cross-sectional view of FIG. 3 and the data shown in FIGS.

  The first parameter is the thickness Z of the high dielectric portion 3. Referring to FIG. 3, the thickness Z of the high dielectric portion 3 is a length from one end portion of the high dielectric portion 3 appearing on the conductor contact surface 11 to the other end portion. The thickness Z of the high dielectric portion 3 is also proportional to the length of the boundary 21 a formed from the intersection side end portion 30 toward the grounding portion 32 along the insulating medium contact surface 13.

  In the graph of FIG. 4, the result of having calculated the relationship between the thickness Z of the high dielectric part 3 and the electric field strength in the triple junction part 61 by simulation is shown. In the case of the shape and arrangement of the low dielectric portion 2 and the high dielectric portion 3 shown in FIGS. 1 to 3, when the thickness Z of the high dielectric portion 3 is 2.6 mm or more, the electric field strength of the triple junction portion 61 is sufficiently small. That is, the electric field concentration in the triple junction 61 is alleviated. The numerical value that the thickness Z of the high dielectric portion 3 is 2.6 mm or more is the width D of the high dielectric portion 3 described later, the distance r between the intersection side end portion 30 and the triple junction portion 61, voltage, insulation with the conductor 31. It has been found by simulation that it does not depend on the angle θ with the medium contact surface 13. Further, when the thickness Z of the high dielectric part 3 is 2.6 mm or more, the internal electric field concentration generated at the boundary 21 b on the ground part 32 side does not affect the triple junction part 61.

  The second parameter is the distance r between the intersection-side end 30 of the high dielectric portion 3 and the intersection 14 (triple junction 61).

  The graph of FIG. 5 shows the result of calculating the relationship between the distance r and the electric field strength at the triple junction 61 by simulation. In the simulation of the graph of FIG. 5, the thickness Z of the high dielectric portion 3 is set to 2.6 mm. From the graph of FIG. 5, it can be seen that the smaller the distance r, the smaller the electric field strength at the triple junction 61, that is, the electric field concentration at the triple junction 61 is reduced. When the distance r is 0 mm, that is, when the intersection-side end 30 of the high dielectric portion 3 coincides with the intersection 14 (triple junction portion 61), the electric field strength at the triple junction portion 61 is the smallest.

  The third parameter is the width D of the high dielectric portion 3. Referring to FIG. 3, the width D of the high dielectric portion 3 is the length of the high dielectric portion 3 measured in the direction from the intersection side end portion 30 toward the axis 20 of the insulator 1 in parallel to the conductor 31. It is.

  The graph of FIG. 6 shows the result of calculating the relationship between the width D of the high dielectric portion 3 and the electric field strength at the triple junction portion 61 by simulation. From the graph of FIG. 6, in the case of the shape and arrangement of the low dielectric portion 2 and the high dielectric portion 3 shown in FIGS. 1 to 3, the electric field strength at the triple junction portion 61 when the width D of the high dielectric portion 3 is 3 mm or more. Is sufficiently small, that is, the electric field concentration at the triple junction 61 is reduced. This is because if the width D of the high dielectric portion 3 is 3 mm or more, the effect of drawing the potential along the entire boundary 21a appears sufficiently, and as a result, the electric field in the vicinity of the triple junction portion 61 is weakened.

  From the results of the above simulation, in the case of the shape and arrangement of the low dielectric portion 2 and the high dielectric portion 3 shown in FIGS. 1 to 3, the thickness Z of the high dielectric portion 3 is 2.6 mm or more and the intersection side of the high dielectric portion 30 When the distance r between the end 30 and the intersection 14 (triple junction 61) is 0 mm and the width D of the high dielectric part 3 is 3 mm or more, the electric field concentration at the triple junction 61 is sufficiently relaxed. did. Next, a simulation result will be described by paying attention to the relationship between the dielectric constant ratio between the low dielectric portion 2 and the high dielectric portion 3 and the material in the insulator 1 having the shape and arrangement of the high dielectric portion 3 described above. .

3-2. Examination of dielectric constant ratio between low dielectric part and high dielectric part:
3-2-1. Insulator configuration:
A simulation was performed for the truncated cone-shaped insulator 1 shown in FIGS. 1, 7, and 9. The insulator 1 of Example 1 and Comparative Examples 1 to 3 described below has a truncated cone shape with a diameter of 20 mm of the conductor contact surface 11, a diameter of 40 mm of the ground contact surface 12, and a height of 10 mm, and the conductor contact surface 11 of the insulator 1. Is connected to a conductor 31 to which a voltage of 100 kV is applied, and the insulating medium 33 is evacuated. The material and dielectric constant ratio of the insulator 1 were set as described below.

Example 1
It is the same as the shape and arrangement of the low dielectric portion 2 and the high dielectric portion 3 shown in FIGS. 1 to 3 described above, and is a form in which sufficient relaxation of the electric field concentration in the triple junction portion 61 is shown in the above simulation. The thickness Z of the high dielectric portion 3 is 2.6 mm, the distance r between the intersection side end portion 30 of the high dielectric portion 30 and the intersection portion 14 (triple junction portion 61) is 0 mm, and the width D of the high dielectric portion 3 is 3 mm. Was set to be. The low dielectric part 2 and the high dielectric part 3 are both made of an inorganic insulating material mainly composed of ceramics. The dielectric constant of the low dielectric part 2 is 8 and the dielectric constant of the high dielectric part 3 is 80.

(Example 2)
FIG. 7 is a perspective view of the insulator 1 according to the second embodiment. FIG. 8 is a partial cross-sectional view taken along the line AA ′ in FIG. 7 and shows a state in which the conductor 31 and the ground portion 32 are connected to the conductor contact surface 11 and the ground contact surface 12, respectively. The high dielectric portion 3 was arranged at the center of the insulator 1 as a cylindrical shape having a diameter of 20 mm and a height of 10 mm. In the insulator 1 according to the second embodiment, the intersection side end portion 30 coincides with the intersection portion 14 (triple junction portion 61), and the boundary 21a extends from the intersection side end portion 30 along the insulating medium contact surface 13 to the ground contact surface. Up to twelve are formed.

(Comparative Example 1)
The insulating body 1 is made of an epoxy resin organic insulating material and has a uniform dielectric constant 5 with a dielectric constant 5 shown in the perspective view of FIG. 9 and the cross-sectional view of FIG.

(Comparative Example 2)
The low dielectric part 2 and the high dielectric part 3 are both organic insulating materials made of epoxy resin, and the same as Example 1 except that the dielectric constant of the low dielectric part 2 is 5 and the dielectric constant of the high dielectric part 3 is 9. It was.

(Comparative Example 3)
The low dielectric part 2 and the high dielectric part 3 are both organic insulating materials made of epoxy resin, and the same as in Example 1 except that the low dielectric part 2 has a dielectric constant of 5 and the high dielectric part 3 has a dielectric constant of 50. It was.

3-2-2. Simulation results and evaluation:
The potential distribution obtained by the simulation is shown in FIG. 11A for Example 1, 12A for Comparative Example 1, FIG. 13A for Comparative Example 2, and FIG. 14A for Comparative Example 3. As for the electric field distribution obtained by the simulation, Example 1 is shown in FIG. 11B, Comparative Example 1 is shown in 12B, Comparative Example 2 is shown in FIG. 13B, and Comparative Example 3 is shown in FIG. 14B. Furthermore, the electric field strength in the triple junction part 61 is shown in the graph of FIG. 15 about the insulator 1 of Example 1 and Comparative Examples 1-3. In addition, the electric field strength in the triple junction part 61 shown in the graph of FIG. 15 is represented by the relative value which set the electric field strength in the triple junction part 61 in the comparative example 1 to 100.

  Compared to the insulator 1 of the comparative example 1 having a uniform dielectric constant of 5, the insulator 1 of the example 1, the comparative example 2 and the comparative example 3 having the low dielectric part 2 and the high dielectric part 3 are triple junctions. It was found that the electric field strength at the portion 61 was small. Further, even in the insulator 1 composed of the dielectric part 2 and the high dielectric part 3, the insulators 1 of Example 1 and Comparative Example 3 in which the dielectric constant ratio between the low dielectric part 2 and the high dielectric part 3 is large are compared. It was found that the electric field strength at the triple junction 61 was smaller than that of the insulator 1 of Example 2.

  11B and 14B, in the insulator 1 of Example 1 and Comparative Example 3, internal electric field concentration may occur at the boundary 21 between the low dielectric portion 2 and the high dielectric portion 3. found. The degree of this internal electric field does not cause internal dielectric breakdown in the insulator 1 of Example 1 made of an inorganic insulating material mainly composed of ceramics, but the insulator 1 of Comparative Example 3 made of an organic insulating material of epoxy resin. Then, internal breakdown was expected to occur.

  The graph of FIG. 16 shows the electric field strength at each position on the insulating medium contact surface 13 along the direction from the conductor contact surface 11 to the ground contact surface 12 for the insulator 1 of Example 1 and Comparative Examples 1 to 3. Show. The upper limit (Z = 10 mm) of the vertical axis of the graph of FIG. 16 corresponds to the triple junction unit 61. In the insulator 1 of the comparative example 1, the electric field strength in the triple junction part 61 is remarkably large. In the insulator 1 of the comparative example 2, the increase in the electric field strength in the triple junction 61 was slightly less than that of the comparative example 1. In the insulator 1 of Example 1 and Comparative Example 3, the electric field strength at the triple junction 61 is small, but rather the electric field strength on the insulating medium contact surface 13 at a position intermediate between the conductor contact surface 11 and the ground contact surface 12. Turned out to be great.

  17A and 17B show the potential distribution and electric field distribution in the insulator 1 of Example 2, respectively. Even in a form in which the boundary 21 a between the low dielectric part 2 and the high dielectric part 3 is formed from the intersection side end 30 to the ground contact surface 12 along the insulating medium contact surface 13, the electric field concentration in the triple junction portion 61. It was found that there was no relaxation.

  INDUSTRIAL APPLICATION This invention can be utilized as an insulator which has ceramics as a main component and is used as an insulation support body of a gas insulation apparatus, an insulation member of a cable connection part, etc.

1: insulator, 2: insulating medium contact part, 3: high dielectric constant part, 11: conductor contact surface, 12: ground contact surface, 13: insulating medium contact surface, 14: intersection point, 19: cylindrical shaft, 20: frustoconical axis, 21: boundary, 21a: boundary, 21b: boundary, 31: conductor, 32: grounding part, 33: insulating medium, 61: triple junction part.

Claims (4)

It has a dielectric part composed mainly of two ceramics with different dielectric constants,
Among the dielectric parts, those having a low dielectric constant of less than 15 are defined as low dielectric parts, and those having a high dielectric constant of 15 or more are designated as high dielectric parts,
An insulator in which the low dielectric part and the high dielectric part are integrated by sintering.   The insulator according to claim 1, wherein a dielectric constant of the high dielectric portion is 3 to 20 times that of the low dielectric portion.   The high dielectric portion includes at least one selected from the group consisting of barium titanate, lead titanate, copper oxide, tin oxide, silicon carbide, lithium niobate, and lead niobate. Insulator. A conductor contact surface that contacts a conductor to which a high voltage is applied, a ground contact surface that contacts a ground portion, and an insulating medium contact surface that contacts an insulating medium;
The low dielectric part forms the insulating medium contact surface;
The insulator according to any one of claims 1 to 3, wherein the high dielectric portion is disposed such that a boundary between the high dielectric portion and the low dielectric portion is along the insulating medium contact surface.

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