JP2020087606A - Insulation member and production method thereof - Google Patents

Abstract

To suppress occurrence and progress of a tree on an insulation member.SOLUTION: Compression stress is applied to an insulation member 10 for covering an insulation object 1 for electrically insulating the same from outside, in a thickness direction, on a part opposite to a side contacting the insulation member 10 in the thickness direction. The stress on a part contacting the insulation member 10 may be smaller than that on the opposite part. In addition, the compression stress in the thickness direction may be monotonously reduced from outside to inside.SELECTED DRAWING: Figure 1

Description

The present invention relates to an insulating member and a method for manufacturing the insulating member.

It is known that, in an electric device used for a long period of time, a dendritic fine tube progresses from the voltage applying section toward the grounding section inside the insulator to cause dielectric breakdown. This fine tube is called a tree, and the phenomenon in which the tree develops is called treeing. This treeing almost determines the insulation life of electrical equipment. Therefore, suppressing the treeing can extend the life of the electric device.

As a method for suppressing the treeing, a method of suppressing the progress by adding a filler to the insulating material to hinder the tree's progress path and increasing the tree branches (see Patent Document 1) and the orientation of the polymer insulating material There is known a method of controlling the tree growth direction by control (see Patent Document 2).

The origin (source) of the tree is known to be projections on the electrode surface, foreign matter in the solid, erosion of the solid due to void discharge, etc., and all are parts where the electric field becomes high. In particular, if stress is present near the interface between the conductor and the insulating layer formed around it, peeling between the conductor and the insulating layer or minute cracks in the insulator near the interface will occur. It is known that such a defect as a starting point causes a tree to easily occur (see Patent Document 1).

JP, 2008-75069, A JP, 2002-93258, A

As described above, basic knowledge is being obtained regarding the occurrence and progress of trees, but a concrete form has not yet been established.

Then, this invention aims at suppressing generation|occurrence|production of a tree in an insulating member, and progress.

In order to achieve the above-mentioned object, the insulating member according to the present invention is an insulating member for covering an object to be insulated and electrically insulating it from the outside, and at a portion on the opposite side to the side in contact with the insulating member in the thickness direction. A compressive stress is applied in the thickness direction.

Further, the method for manufacturing an insulating member according to the present invention is a method for manufacturing an insulating member for covering an insulating target and electrically insulating it from the outside, in which a thermosetting resin is injected into a heating container, A filling step of filling the periphery of the thermosetting resin, a heating step of heating the thermosetting resin filled in the filling step, and a cooling step of cooling the thermosetting resin after the heating step. After the step is completed, the thermosetting resin is characterized in that an insulating member having a larger compressive stress in the thickness direction is formed in the outer portion in the thickness direction than in the inner portion in contact with the insulating object.

According to the present invention, it is possible to suppress the generation and development of trees in the insulating member.

It is a cross-sectional view showing a configuration of an insulating member according to the first embodiment. It is a flowchart which shows the procedure of the manufacturing method of the insulating member which concerns on 1st Embodiment. It is a perspective view showing a system in a manufacturing method of an insulating member concerning a 1st embodiment. FIG. 5 is a perspective view showing a state after the thermosetting resin is injected in the method for manufacturing the insulating member according to the first embodiment. It is a perspective view showing the state after formation of the insulating member in the manufacturing method of the insulating member concerning a 1st embodiment. It is a perspective view of a testing device for explaining an effect of an insulating member concerning a 1st embodiment. It is a longitudinal cross-sectional view showing the case of the first insulating member for explaining the effect of the insulating member according to the first embodiment. It is a longitudinal cross-sectional view showing the case of the 2nd insulating member for demonstrating the effect of the insulating member which concerns on 1st Embodiment. It is a flow figure showing a procedure of a manufacturing method of an insulating member concerning a 2nd embodiment. It is a perspective view which shows the system at the time of heating in the manufacturing method of the insulating member which concerns on 2nd Embodiment. It is a perspective view showing the state after filling up with a thermosetting resin in the manufacturing method of the insulating member concerning a 2nd embodiment. It is a perspective view which shows the system at the time of cooling of the outer surface side of the thermosetting resin in the manufacturing method of the insulating member which concerns on 2nd Embodiment. It is a flowchart which shows the procedure of the manufacturing method of the insulating member which concerns on 3rd Embodiment. It is a cross-sectional view which shows the state of the system at the stage which installed the partition cylinder in the manufacturing method of the insulating member which concerns on 3rd Embodiment. It is a cross-sectional view showing a state at the stage of injecting a thermosetting resin in the method for manufacturing an insulating member according to the third embodiment. It is a cross-sectional view showing the state at the stage when heating and cooling are completed in the method for manufacturing an insulating member according to the third embodiment. It is a flowchart which shows the procedure of the manufacturing method of the insulating member which concerns on 4th Embodiment. It is a transverse cross-sectional view showing a state at the stage of injecting a thermosetting resin into the first heating container in the method for manufacturing an insulating member according to the fourth embodiment. It is a cross-sectional view showing the state at the stage when heating and cooling by the first heating container are completed in the method for manufacturing an insulating member according to the fourth embodiment. It is a cross-sectional view showing a state at the stage of injecting a thermosetting resin into a second heating container in the method for manufacturing an insulating member according to the fourth embodiment. It is a cross-sectional view showing the state at the stage when heating and cooling by the second heating container are completed in the method for manufacturing an insulating member according to the fourth embodiment.

Hereinafter, an insulating member and a method for manufacturing an insulating member according to the present invention will be described with reference to the drawings. Here, parts that are the same or similar to each other are designated by common reference numerals, and duplicate description will be omitted.

[First Embodiment]
FIG. 1 is a cross-sectional view showing the structure of the insulating member according to the first embodiment.

The insulating member 10 is arranged outside the insulation target 1 such as a metal conductor. Here, the insulation target 1 is assumed to have various shapes, but in the following description, assuming a metal conductor, a case of a cylindrical shape extending in the axial direction is shown. Even if the object to be insulated 1 has another shape, the basic concept of the structure of the insulating member and the method of manufacturing the insulating member described below is the same.

The insulating member 10 that covers the insulation target 1 and electrically insulates it from the outside will be described here as being disposed on the radial outside of the insulation target 1 while being in close contact with the radial outside surface of the insulation target 1.

The insulating member 10 is made by thermosetting a thermosetting resin. As the thermosetting resin, unsaturated polyester resin, epoxy resin, phenol resin, unsaturated polyester resin or the like can be used.

The insulating member 10 has a first insulating layer 11, a second insulating layer 12, a third insulating layer 13, and a fourth insulating layer 14, which are arranged in layers in order from the outside to the inside in the radial direction, that is, the thickness direction thereof. Here, the first insulating layer 11, the second insulating layer 12, the third insulating layer 13, and the fourth insulating layer 14 have different internal stress states, and at least the first insulating layer 11 which is the outermost layer. In, the compressive stress is working.

Although the present embodiment is described as having four layers having different stress states, the stress state does not change stepwise in the thickness direction. That is, what is continuously changing in the thickness direction is divided into four layers for convenience of explanation. In this embodiment, the compressive stress is highest on the outer surface of the first insulating layer 11. On the other hand, the stress is small in the inner portion of the fourth insulating layer 14, that is, near the boundary between the fourth insulating layer 14 and the insulation target 1. In addition, the compressive stress gradually decreases from the first insulating layer 11 to the fourth insulating layer 14.

FIG. 2 is a flowchart showing the procedure of the method for manufacturing an insulating member according to the first embodiment.

FIG. 3 is a perspective view showing a system in the method of manufacturing the insulating member according to the first embodiment. First, the insulation target 1 is installed inside the heating container 3 (step S11).

The heating container 3 is housed in the pressure resistant container 5. The heating container 3 and the pressure resistant container 5 are installed with their central axes in the vertical direction. At this stage (step S01), the upper plate 5u is removed.

Here, the heating container 3 has a cylindrical side portion and a bottom portion corresponding to the shape of the cylindrical insulation target 1. The heating container 3 can heat an object housed therein from the outside. In order to enhance the cooling efficiency of the thermosetting resin, which will be described later, after heating, for example, the heating container 3 can be divided so that a space is formed between the thermosetting resin and the thermosetting resin. It may be configured.

The insulation target 1 is installed so that its axis is substantially in the radial center of the heating container 3. An annular internal space 3 a is formed on the outer side in the radial direction of the insulation target 1 inside the heating container 3.

The pressure-resistant container 5 is, for example, a closed container having a cylindrical side surface as shown in FIG. In FIG. 3, the inside of the pressure-resistant container 5 is shown so that it can be seen through, but the pressure-resistant container 5 need not be transparent. Further, the upper plate 5u of the pressure resistant container 5 is formed so as to be removable, and the upper side of the pressure resistant container 5 is opened when the upper plate 5u is removed.

A pressure pipe 5a, a cooling gas injection pipe 5b, and an exhaust pipe 5c are connected to the upper plate 5u of the pressure-resistant container 5. The pressurizing pipe 5a is connected to a pressurizing source such as a compressor or a gas cylinder via a stop valve and a pressure reducing valve (not shown) that can be opened and closed. The cooling gas injection pipe 5b is connected to a cooling source such as a cooler via a stop valve (not shown) that can be opened and closed, and guides a cooling gas such as air into the pressure resistant container 5. The exhaust pipe 5c communicates with the outside air through a stop valve (not shown) that can be opened and closed, and discharges the gas inside the pressure resistant container 5 to the outside of the pressure resistant container 5.

A cooling member 4 is attached to the insulation target 1. The cooling member 4 is thermally connected to a cooling source (not shown), and cools the insulation target 1 as necessary. The cooling member 4 is mechanically connected to a cooling source, for example, and the heat removed from the insulation target 1 is removed by heat conduction. Alternatively, the cooling member 4 may be a heat exchanger or a heat pipe. The penetrating portion of the pressure resistant container 5 at the connecting portion between the cooling member 4 and the outside is hermetically treated.

Next, the thermosetting resin 110 (FIG. 4) is injected into the inside of the heating container 3 and filled around the insulation target 1 (step S12). FIG. 4 is a perspective view showing a state after the thermosetting resin is injected. As shown in FIG. 4, the thermosetting resin 110 is injected into the internal space 3a shown in FIG. 3 to fill the internal space 3a with the thermosetting resin 110.

Next, the heating container 3 is heated to a high temperature to heat the outer periphery of the thermosetting resin 110 and cool the insulation target 1 (step S13). Specifically, the thermosetting resin 110 is heated from the outside in the radial direction by the heating container 3, and the insulation target 1 is cooled by the cooling member 4.

By heating from the outside in the radial direction, the surface temperature of the thermosetting resin 110 is set to be equal to or higher than the glass transition temperature of the thermosetting resin 110. Further, by cooling the insulation target 1, the temperature of the portion of the thermosetting resin 110 that contacts the insulation target 1 is set to about room temperature. As a result, the internal temperature of the thermosetting resin 110 has a temperature gradient in the thickness direction from about room temperature to about the glass transition temperature from the portion in contact with the insulation target 1 to the surface of the thermosetting resin 110. A temperature distribution state is set. Here, the room temperature or so means the temperature or so in the area where the work of forming the insulating member 10 on the outside of the insulation target 1 is performed.

Next, the thermosetting resin is pressed with a temperature gradient in the thickness direction (step S14). Specifically, first, the upper plate 5u of the pressure resistant container 5 is attached, and the pressure resistant container 5 is sealed. Then, while maintaining the heating of the thermosetting resin 110 from the outside by the heating container 3 and the cooling state of the insulation target 1 by the cooling member 4, the inside of the pressure resistant container 5 is heated via the pressurizing pipe 5a. A high pressure gas is introduced into the pressure resistant container 5 by communicating with the pressure source.

Most of the thermosetting resin 110 shrinks during thermosetting. Therefore, a clearance is generated between the heated thermosetting resin 110 and the heating container 3. By introducing a high-pressure gas into the pressure-resistant container 5, the thermosetting resin 110 is uniformly pressed from the outside.

In addition, when the thermosetting resin 110 has little shrinkage during thermosetting or expands conversely, the heating container 3 is divided into the heating container 3 before the upper plate 5u of the pressure resistant container 5 is closed. By heating up to that time, a gap is formed between the thermosetting resin 110 and the thermosetting resin 110 which is being cured.

Next, heating is completed, and the inside of the pressure resistant container 5 is cooled to room temperature while maintaining the pressurized state (step S15). Specifically, in FIG. 3, only the pressurizing tube 5a may be electrically connected to the inside of the pressure resistant container 5 and left to stand for natural cooling. Alternatively, the cooling gas may be injected into the pressure resistant container 5 via the cooling gas injection pipe 5b. At this time, in order to maintain the internal pressure of the pressure resistant container 5 within a predetermined range, the gas in the pressure resistant container 5 is discharged to the outside from the exhaust pipe 5c in parallel with the injection of the cooling gas.

FIG. 5 is a perspective view showing a state after the insulating member is formed. The insulating member 10 is formed on the outside in the radial direction of the insulation target 1 by the procedure of the method for manufacturing the insulating member as described above. In the insulating member 10, as described with reference to FIG. 1, the compressive stress is small in the vicinity of contact with the object to be insulated 1, while it is large on the surface opposite to the thickness direction, that is, at the outermost portion in the thickness direction. The compressive stress is applied.

FIG. 6 is a perspective view of a test device for explaining the effect of the insulating member according to the first embodiment. FIG. 7 is a longitudinal sectional view showing the case of the first insulating member, and FIG. 8 is a longitudinal sectional view showing the case of the second insulating member. Hereinafter, the contents of the test performed and the operation and effect of the insulating member according to the first embodiment will be described with reference to FIGS. 6 to 8.

As shown in FIG. 6, in order to observe the state of tree growth, a device was constructed in which a needle electrode 2 and a cubic transparent epoxy resin insulator 201 were arranged around the needle electrode 2. The length L of one side of the insulator 201 is about 15 mm, and the distance D from the tip of the needle electrode 2 to the surface of the opposite insulator 201 (the lower surface in FIG. 6) is about 3 mm. 7 and 8 show cases where the insulators 201a and 201b are in different stress states.

The distribution of compressive stress is observed by the photoelastic method. Here, the photoelastic method utilizes the fact that birefringence occurs when a load is applied to a transparent, non-anisotropic object, or when stress remains in the object, and interference fringes that reflect the stress distribution are generated. It is a method to generate and visualize the distribution.

In the first insulator 201a shown in FIG. 7, the compressed portion 202 corresponding to the interference fringe has one layer, and in the case shown in FIG. 8, the compressed portion 204 corresponding to the interference fringe has four layers. In any case, the compressive stress remains in a range beyond about 1.5 mm from the tip of the needle electrode 2.

However, the stress applied to the first insulator 201a shown in FIG. 7 is smaller than the stress applied to the second insulator 201b shown in FIG. In this state, in each system, the lower surface of each of the first insulator 201a and the second insulator 201b made of epoxy resin is grounded, and a high voltage of 12 kVrms, 50 Hz AC waveform is applied to the needle electrode 2. did.

As a result, the tree continued to develop in the absence of compressive stress. Further, in the case where the compressive stress remains in the region, it penetrates into the region and progresses in the same manner up to about 2.0 to 2.5 mm, but beyond that, the progress of the tree is suppressed. Became.

In the case shown in FIG. 8, the dielectric breakdown time leading to dielectric breakdown was longer than that in the case shown in FIG. 7, and the dielectric breakdown time was 410 hours. When the inside of a part of the samples was observed during voltage application, trees 203 and 205 were observed as shown in FIGS. 7 and 8, respectively. As described above, it was confirmed that the tree growth was suppressed in the region where the compressive stress was large.

In the electric device using the insulating member 10 according to the present embodiment, that is, in the electric device provided with the insulating target 1 such as a metal conductor and the insulating member 10 covering the insulating target 1, the insulating target 1 and the insulating member 10 are provided. The compressive stress at the interface is small, and a large compressive stress is applied to the outer surface of the insulating member 10 (the low voltage side of the insulating member 10).

In this state, a high potential is applied to the insulation target 1, and a ground potential is applied to the outer surface of the insulating member 10. At the interface with the object to be insulated 1, the stress applied to the insulating member 10 is small, so that peeling or cracking that is the starting point of the tree is unlikely to occur. Further, if a tree starts from this interface starting from an initial defect or the like, the tree advances toward the outer side in the thickness direction of the insulating member 10. As the tree progresses and approaches the outer surface of the insulating member 10, the compressive stress increases and the progress of the tree is suppressed.

[Second Embodiment]
FIG. 9 is a flowchart showing the procedure of the method for manufacturing an insulating member according to the second embodiment. The second embodiment is a modification of the first embodiment.

First. The insulation target 1 is installed in the heating container 3 (step S21). FIG. 10: is a perspective view which shows the system at the time of heating in the manufacturing method of the insulating member which concerns on 2nd Embodiment. As shown in FIG. 10, a heater 8 is connected to the insulation target 1. The heater 8 is, for example, a heater having a heat generating portion (not shown), or heat is transferred from the heat generating portion by heat conduction or radiation.

Next, similarly to the first embodiment, the thermosetting resin 110 is injected into the internal space 3a of the heating container 3 (step S12). FIG. 11 is a perspective view showing a state after filling the thermosetting resin.

After filling the thermosetting resin 110 in step S12, the heating container 3 is heated to a high temperature to heat the thermosetting resin 110 (step S23). In addition, in order to simultaneously heat the thermosetting resin 110 from the outer side and the inner side in the radial direction, the insulation target 1 is heated by the heater 8. In this way, the entire thermosetting resin 110 is raised above the glass transition temperature almost at the same time.

Next, the heating is finished, and the thermosetting resin 110 is cooled by making the cooling rate on the outer surface side faster than the cooling rate on the inner surface side (step S24).

FIG. 12 is a perspective view showing a system at the time of cooling the outer surface side of the thermosetting resin. The insulating object 1 and the thermosetting resin 110 arranged around it are taken out from the heating container 3, and a cooler 7 is arranged outside the thermosetting resin 110 in the radial direction. The cooler 7 is connected to a cooling gas supply source (not shown), and blows a cooling gas such as cooled air to the radially outer side of the thermosetting resin 110.

On the other hand, the insulation target 1 is supplied with heat from the heater 8 according to a predetermined cooling rate so that the cooling rate does not become too fast, and transfers the heat to the contact surface on the radially inner side of the thermosetting resin 110. To do.

In this way, the outer surface side of the thermosetting resin 110 is cooled by the cooler 7 on the cooling side of, for example, about 30° C./Hr, and the inner surface side of the thermosetting resin 110 is suppressed by the heater 8. For example, it is cooled at a cooling rate of about 10° C./Hr.

Note that, in FIG. 12, the case where the cooling gas is blown to the outer surface side of the thermosetting resin 110 by the cooler 7 to secure the cooling rate is shown as an example, but the present invention is not limited to this. For example, the outside of the thermosetting resin 110 may be filled with a liquid and the temperature of the liquid may be controlled.

As described above, the temperature of the peripheral portion of the thermosetting resin 110 around the insulation target 1, that is, the inside portion of the thermosetting resin 110 is gradually cooled so as not to be different from the temperature of the insulation target 1, so that the thermosetting resin 110 is thermoset. It is possible to reduce the stress of the peripheral portion of the insulating object 1 of the conductive resin 110. Further, by cooling the outside of the thermosetting resin 110 at a high speed, a large compressive stress can be applied to the outside portion of the thermosetting resin 110.

[Third Embodiment]
FIG. 13 is a flowchart showing the procedure of the method for manufacturing an insulating member according to the third embodiment. This embodiment is a modification of the first embodiment.

First, the insulation target 1 is installed in the heating container 3 (step S31).

Next, a partition cylinder is installed in the annular space sandwiched between the heating container 3 and the insulation target 1 (step S32).

FIG. 14 is a cross-sectional view showing a state of a system at a stage where a partition cylinder is installed in the method for manufacturing an insulating member according to the third embodiment. The annular space sandwiched between the heating container 3 and the insulation target 1 is radially divided by the partitioning cylinder 6 into an outer space 3b and an inner space 3c. Here, as the partition tube 6, a thermosetting resin thermoset is used. Further, as the thermosetting resin, either the resin 31 for high linear expansion coefficient insulating material or the resin 32 for low linear expansion coefficient insulating material described later is used.

Next, the outer space 3b and the inner space 3c shown in FIG. 14 are filled with thermosetting resin (step S33).

FIG. 15 is a cross-sectional view showing a state at the stage of injecting a thermosetting resin in the method for manufacturing an insulating member according to the third embodiment. The outer space 3b is filled with a resin 31 for high linear expansion coefficient insulating material, and the inner space 3c is filled with a resin 32 for low linear expansion coefficient insulating material.

Here, as the resin 32 for a low linear expansion coefficient insulating material, a resin whose linear expansion coefficient after thermosetting is substantially the same as the linear expansion coefficient of the insulation target 1 is selected. Here, when the resin 32 for low linear expansion coefficient insulating material has a larger linear expansion coefficient than the insulation target 1, the term “substantially the same degree” means that the resin 32 for low linear expansion coefficient insulating material and the insulation target 1 are When the linear expansion coefficient of the low linear expansion coefficient insulating material resin 32 is smaller than that of the insulation target 1, the low linear expansion coefficient insulating resin resin is used. It means that the difference in linear expansion coefficient is such that stress such as cracking in 32 is not generated. Further, as the resin 31 for high linear expansion coefficient insulating material, a resin having a larger linear expansion coefficient after thermosetting than the resin 32 for low linear expansion coefficient insulating material is selected.

For example, when the linear expansion coefficient of the insulation target 1 is aluminum, the low linear expansion coefficient insulating member 32a (FIG. 16) formed by thermosetting the low linear expansion coefficient insulating material resin 32 is, for example, 24, which is similar to that of aluminum. A resin having a linear expansion coefficient of about 10 ⁻⁶ /° C. is selected. Further, the high linear expansion coefficient insulating member 31a (FIG. 16) formed by thermosetting the resin 31 for high linear expansion coefficient insulating material is, for example, an epoxy having a linear expansion coefficient of about 45×10 ^{−6 to} 65×10 ⁻⁶ /° C. Select resin.

Next, the heating container 3 is heated to a high temperature to heat the insulation target 1 (step S34). That is, the temperatures of the resin 31 for high linear expansion coefficient insulating material and the resin 32 for low linear expansion coefficient insulating material are raised to temperatures equal to or higher than the glass transition temperature.

Next, heating is completed and the heating container 3 is removed (step S35). FIG. 16 is a cross-sectional view showing a state at the stage when heating and cooling are completed in the method for manufacturing an insulating member according to the third embodiment. The resin 31 for high linear expansion coefficient insulating material filled in the outer space 3b serves as the high linear expansion coefficient insulating member 31a, and the resin 32 for low linear expansion coefficient insulating material filled in the inner space 3c serves as the low linear expansion coefficient insulating member 32a. ing. Instead of removing the heating container 3, the insulation target 1 and the low linear expansion coefficient insulating member 32 a and the high linear expansion coefficient insulating member 31 a formed around the insulation target 1 may be taken out from the heating container 3.

Although FIGS. 14 to 16 show the case where two types of layers are formed in the radial direction as an example, three or more types of layers may be formed in the radial direction. In this case, a required number of partition cylinders are installed according to the number of layers. Further, a thermosetting resin is selected such that the innermost layer has a linear expansion coefficient similar to that of the insulation target 1 after the thermal curing, and the outermost layer has a high linear expansion coefficient after the thermal curing, for example. A thermosetting resin similar to the material resin 31 is selected. Further, for the region sandwiched between these, a thermosetting resin is selected so that the linear expansion coefficient monotonically decreases from the outer side to the inner side in the thickness direction after heat curing.

As a method of providing a gradient to the linear expansion coefficient, only a mixed liquid of an epoxy resin and a curing agent is used for the outermost layer. The linear expansion coefficient of the epoxy resin is about 45×10 ^{−6 to} 65×10 ⁻⁶ /° C. as described above. For the inner layer, a mixed liquid of an epoxy resin and a curing agent is further prepared by using a mixed liquid of inorganic particles such as silica or alumina having a small linear expansion coefficient. In this case, the coefficient of linear expansion is, for example, about 20×10 ⁻⁶ /°C. The concentration of the inorganic particles is increased toward the inner side. As the innermost layer, one that is adjusted so that the linear expansion coefficient after thermosetting is approximately the same as the linear expansion coefficient of the insulation target 1 is used. As the inorganic particles to be mixed, one having a particle size in the range of nanometer to micrometer is used alone, or a plurality of kinds thereof are mixed at the same time.

As described above, in the method for manufacturing the insulating member according to the present embodiment, the linear expansion coefficient of each layer can be set to a desired value.

In the present embodiment, the case where the partition cylinder is used has been shown as an example, but instead of this, after the inner layer is heat-cured, a thermosetting resin is placed on the outer side and then heat-cured. Alternatively, a multilayer insulating member may be formed by sequentially performing the procedure.

By forming as described above, the insulating member produced by curing the thermosetting resin has a large linear expansion coefficient in the outer portion having a large linear expansion coefficient. Swelling increases. Therefore, an insulating member having a larger compressive stress on the outer side in the thickness direction can be obtained.

[Fourth Embodiment]
FIG. 17 is a flowchart showing the procedure of the method for manufacturing an insulating member according to the fourth embodiment. This embodiment is a modification of the third embodiment. Also in this embodiment, two types of thermosetting resins having different characteristics are used, but the thermosetting resin used for injection is different from that of the third embodiment. The manufacturing method is also different from that of the third embodiment. Specifically, two types of heating containers are used. Other than these, it is basically similar to the third embodiment.

FIG. 18 is a cross-sectional view showing a state in which a thermosetting resin has been injected into the first heating container.

First, the insulation target 1 is installed in the first heating container 43a (step S41).

Next, the thermosetting resin is injected into the annular space sandwiched between the first heating container 43a and the insulation target 1 (step S42). The thermosetting resin to be injected at this time is a low curing shrinkage resin 42 having a small shrinkage during heat curing, that is, a small curing shrinkage.

Next, after heating the low cure shrinkage resin 42 in the first heating container 43a, the low cure shrinkage resin 42 is cooled (step S43). FIG. 19 is a cross-sectional view showing a state at the stage where heating and cooling by the first heating container are completed. The low curing shrinkage resin 42 serves as the second insulating member 42a.

Next, the insulation target 1 around which the second insulating member 42a is arranged is installed in the second heating container 43b (step S44). That is, the insulation target 1 around which the second insulating member 42a is arranged is moved from the inside of the first heating container 43a to the inside of the second heating container 43b having a diameter larger than that of the first heating container 43a.

Next, the thermosetting resin is injected into the annular space sandwiched between the second heating container 43b and the second insulating member 42a (step S45). FIG. 20 is a transverse cross-sectional view showing a state in which the thermosetting resin has been injected into the second heating container. The thermosetting resin injected at this time is the high cure shrinkage resin 41 having a higher cure shrinkage than the low cure shrinkage resin 42.

Next, after heating the high cure shrinkage resin 41 by the second heating container 43b, the high cure shrinkage resin 41 is cooled (step S46). FIG. 21 is a cross-sectional view showing a state at the stage where heating and cooling by the second heating container are completed. The high cure shrinkage resin 41 serves as the first insulating member 41a.

In addition, in this embodiment, the point that a plurality of layers may be formed is the same as that described in the third embodiment.

By forming as described above, since the thermosetting resin has a large curing shrinkage rate at the outer portion, when the thermosetting resin is heated and thermally cured, the thermosetting resin shrinks toward the outer side in the thickness direction. As a result, tensile stress acts on the cured thermosetting resin in the circumferential direction, but compressive stress acts in the radial direction.

When a voltage is applied between the insulation target 1 and the outer surface of the first insulating member 41a, the potential gradient is formed in the radial direction, that is, the thickness direction of the first insulating member 41a. Therefore, the tree is propagated in the radial direction (thickness direction). In this embodiment, since the compressive stress is formed in the radial direction, it has an effect of suppressing the development of the tree.

Further, by disposing the high curing shrinkage rate resin 41 having a large curing shrinkage rate around the second insulating member 42a where the low curing shrinkage rate resin 42 is thermally cured, and disposing the first insulating member 41a thermally cured. A large compressive stress is generated in the first insulating member 41a in the radial direction. Further, the inner second insulating member 42a generates compressive stress due to the rattling force of the first insulating member 41a, but this range remains near the surface of the second insulating member 42a. The radially inner region in the second insulating member 42a is in a state of low stress, which is almost the same as the state shown in FIG. 19 in step S43.

As described above, also in the fourth embodiment, the compressive stress is formed in the gradient direction of the potential, and the generation and development of trees in the insulating member can be suppressed.

[Other Embodiments]
Although the embodiments of the present invention have been described above, the embodiments are presented as examples and are not intended to limit the scope of the invention. For example, in the embodiment, the case where the insulation target 1 has a cylindrical shape has been described as an example, but the insulation target 1 is not limited to the cylindrical shape. The insulation target 1 may be, for example, one having a polygonal or curved cross section, a columnar shape, a spherical shape, an ellipsoidal shape, a rectangular parallelepiped shape, a plate shape or a thin curved surface, or a combination thereof. .. In these cases, the shape of the heating container 3 and the partition tube 6 in the third and fourth embodiments may be set to an appropriate shape according to the shape of the insulation target 1.

Further, the features of the respective embodiments may be combined. Furthermore, the embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. The embodiments and the modifications thereof are included in the invention described in the claims and equivalents thereof, as well as included in the scope and the gist of the invention.

DESCRIPTION OF SYMBOLS 1... Insulation object, 2... Needle electrode, 3... Heating container, 3a... Inner space, 3b... Outer space, 3c... Inner space, 4... Cooling member, 5... Pressure resistant container, 5a... Pressurizing tube, 5b... For cooling Gas injection pipe, 5c... Exhaust pipe plate, 5u... Upper plate, 6... Partition cylinder, 7... Cooler, 8... Heater, 10... Insulating member, 11... First insulating layer, 12... Second insulating layer, 13 ... third insulating layer, 14... fourth insulating layer, 31... resin for high linear expansion coefficient insulating material, 31a... high linear expansion coefficient insulating member, 32... resin for low linear expansion coefficient insulating material, 32a... low linear expansion coefficient Insulating member, 41... High curing shrinkage resin, 41a... First insulating member, 42... Low curing shrinkage resin, 42a... Second insulating member, 43a... First heating container, 43b... Second heating container, 110 ... thermosetting resin, 201... insulator, 201a... first insulator, 201b... second insulator, 202... compressed part, 203... tree, 204... compressed part, 205... tree

Claims (10)

An insulating member for covering an insulating object and electrically insulating it from the outside,
An insulating member, wherein a compressive stress is applied in the thickness direction at a portion opposite to a side in contact with the insulating member in the thickness direction. The insulating member according to claim 1, wherein the stress at the portion in contact with the insulating member is smaller than the stress at the portion on the opposite side. 3. The insulating member according to claim 1, wherein the compressive stress in the thickness direction monotonously decreases from the outer side to the inner side in the thickness direction. The insulating member according to claim 1, wherein a linear expansion coefficient of a portion in contact with the insulation target is substantially the same as a linear expansion coefficient of the insulation target. A method of manufacturing an insulating member for covering an insulating object to electrically insulate the outside,
A filling step of injecting a thermosetting resin into the heating container and filling the periphery of the insulating object,
A heating step of heating the thermosetting resin filled in the filling step,
A cooling step of cooling the thermosetting resin after the heating step,
Have
After the cooling step, the thermosetting resin is characterized in that an insulating member having a larger compressive stress in the thickness direction is formed in the outer portion of the thermosetting resin than in the inner portion in contact with the insulating object in the thickness direction. A method for manufacturing an insulating member. In the heating step, the inner portion is maintained at about room temperature, while the surface of the outer portion in the thickness direction of the thermosetting resin is heated so as to have a temperature distribution state that is equal to or higher than the glass transition temperature. ,
In the cooling step, in the temperature distribution state, a compressive stress is applied to the thermosetting resin in the thickness direction, and the thermosetting resin is cooled in a state where the compressive stress is applied.
The method for manufacturing an insulating member according to claim 5, wherein. In the heating step, the thermosetting resin is heated to a glass transition temperature or higher,
The method for manufacturing an insulating member according to claim 5, wherein, in the cooling step, a cooling rate of the outer portion of the thermosetting resin is higher than a cooling rate of the inner portion. In the thickness direction of the thermosetting resin, a first thermosetting resin is used for the outer portion, a second thermosetting resin is used for the inner portion, and heat of the first thermosetting resin is used. The method for manufacturing an insulating member according to claim 5, wherein the linear expansion coefficient after curing is higher than the linear expansion coefficient after thermal curing of the second thermosetting resin. The method for manufacturing an insulating member according to claim 8, wherein a linear expansion coefficient of the second thermosetting resin after the thermosetting is approximately the same as the linear expansion coefficient of the insulation target. In the thickness direction of the thermosetting resin, a third thermosetting resin is used for the outer portion, a fourth thermosetting resin is used for the inner portion, and the third thermosetting resin is cured. The method of manufacturing an insulating member according to claim 5, wherein the shrinkage rate is higher than the cure shrinkage rate of the fourth thermosetting resin.

Images