Thick insulating film-coated conductor, method of manufacturing same, and insulated switchgear

Abstract

This thick insulating film-coated conductor (1) comprises: a metal conductor (11); one or more first photocurable resin layers (12) that are in close contact with the metal conductor (11); and one or more second photocurable resin layers (13) that are in close contact with the first photocurable resin layers (12). The first photocurable resin layers (12) have a silicone polymer having an acrylic group. The second photocurable resin layers (13) have a silicone polymer having a vinyl group or a silicone polymer having an H group.

Description

Thick-walled insulating film coated conductor, method for manufacturing the same, and insulated switchgear

[0001] This disclosure relates to a thick insulating film coated conductor having an insulating layer on the surface of a metal conductor, a method for manufacturing the same, and an insulated switchgear.

[0002] In gas-fired switchgear, circuit breakers, disconnectors, busbars, surge arresters, instrument transformers, etc., are housed in a grounded metal tank. The metal tank is filled with SF6, an insulating gas. However, SF6 gas has a greenhouse effect more than 20,000 times that of CO2, and has a very high global warming potential. For this reason, there has been a trend towards restricting its use in recent years. To reduce the environmental impact, the development and practical application of gas-fired switchgear that does not use SF6 gas is being considered. For example, a method that does not use SF6 gas and uses dry air is attracting attention for its practical application because it has a global warming potential of zero. However, dry air has only one-third the dielectric strength of SF6 gas, so in order to achieve equivalent insulation performance, a large insulation distance is required, making the device larger. Therefore, insulated switchgear using a hybrid insulation method that combines solid insulation and gas insulation is increasingly being used. In this case, solid insulation is achieved by directly applying an insulating layer to the surface of the metal conductor. Coating a metal conductor surface with a solid insulator can improve insulation performance through the following effects: (A) suppression of sustained discharge growth by inhibiting electron supply from the metal conductor surface, and (B) reduction of the maximum electric field in the air. Of these, (B) is less effective if the insulator is thin, so a thick insulating film is desirable to achieve sufficient insulating strength.

[0003] Patent Document 1 discloses a technique for forming an insulating layer on the surface of a coil conductor in a large rotating electrical machine. In the technique described in Patent Document 1, a mica tape is wound around the surface of the coil conductor to a predetermined thickness to form a main insulation base material layer. Then, a finishing tape obtained by laminating a heat-shrinkable cross tape and a heat-shrinkable film tape is wound around the outside of the main insulation base material layer at the coil end portion. Then, vacuum impregnation and heat treatment of the resin are performed to heat-cure the resin. During heat curing, the finishing tape thermally shrinks, preventing leakage of the resin impregnated by the thermally shrunk finishing tape at the coil end portion and suppressing the generation of voids in the main insulation base material layer.

[0004] Patent Document 2 discloses a multilayer coating composed of a plurality of photocurable resin cured layers, in which the Young's modulus of the first layer is 5 MPa or more and 100 MPa or less, and the Young's modulus of the second layer is 50 MPa or more and 1000 MPa or less for a wire multilayer coating. In the technique described in Patent Document 2, a wire coating layer excellent in strength is easily and uniformly formed by irradiation with radiation such as ultraviolet rays, and the wire coating layer can be peeled off by a simple operation. Therefore, the wiring operation is easy, and the conductor itself is not damaged during the wiring operation.

[0005] Japanese Patent Application Laid-Open No. 2003-230259 Japanese Patent Application Laid-Open No. 2009-164076

[0006] As described above, in an insulating switchgear that does not use SF6 gas, it is necessary to thicken the insulating layer covering the metal conductor. However, when the insulating layer is thickened, there is a possibility that large thermal stress may be generated near the interface between the two due to the difference in the thermal shrinkage rate between the metal conductor and the insulating layer. Depending on the use environment, there is a problem that the contact interface between the two may peel off due to the generated thermal stress, or cracks may occur in the insulating layer, resulting in discharge and a decrease in the insulation withstand voltage. Also, when applying a thick insulating film to a rough metal conductor on the surface of the insulating switchgear, the thick insulating film may not follow the minute protrusions on the conductor surface, forming minute gaps near the minute protrusions on the conductor surface. As a result, there is also a problem that discharge occurs in these minute gaps, leading to a decrease in the insulation withstand voltage.

[0007] However, the technology described in Patent Document 1 only involves wrapping a mica tape as the main insulating base material layer around the outside of the coil and wrapping a finishing tape around the coil end to prevent resin leakage during heat curing, and therefore cannot solve the problems of the insulated switchgear described above. Specifically, the technology described in Patent Document 1 has the problem that it cannot meet the requirement for a thicker insulating layer in an insulated switchgear. Furthermore, the technology described in Patent Document 1 does not provide a technology to suppress thermal stress caused by the difference in thermal shrinkage rates between the mica tape of the main insulating base material layer and the coil conductor, which is a metal conductor, and consequently the occurrence of interfacial delamination and cracks. In addition, the technology described in Patent Document 1 has the problem that it is difficult to make the main insulating base material layer conform to the shape of the protrusions on the surface of the metal conductor and to adhere to it without gaps.

[0008] The technology described in Patent Document 2 is for wire coating and has the problem of not being able to meet the requirement for thicker insulating layers in insulated switchgear. Furthermore, with the technology described in Patent Document 2, instantaneous curing of the first and second layers is difficult. For this reason, when the technology described in Patent Document 2 is applied to the formation of thick insulating films in insulated switchgear and multiple layers are formed, the time required for forming the coating layers becomes long, resulting in a decrease in efficiency.

[0009] This disclosure has been made in view of the above, and aims to provide a thick insulating film coated conductor that can reduce the environmental impact of gas switchgear and suppress a decrease in dielectric strength while increasing the thickness of the insulating layer.

[0010] To solve the above-mentioned problems and achieve the objective, the thick insulating film coated conductor according to this disclosure comprises a metal conductor, one or more first photocurable resin layers in close contact with the metal conductor, and one or more second photocurable resin layers in close contact with the first photocurable resin layer. The first photocurable resin layer has a silicone polymer having acrylic groups. The second photocurable resin layer has a silicone polymer having vinyl groups or a silicone polymer having H groups.

[0011] According to this disclosure, the environmental impact of gas switchgear can be reduced, and the reduction in dielectric strength can be suppressed while increasing the thickness of the insulating layer.

[0012] A schematic cross-sectional view showing an example of the configuration of a thick insulating film coated conductor according to Embodiment 1. A schematic cross-sectional view showing an example of the configuration of a thick insulating film coated conductor according to Embodiment 2. A schematic cross-sectional view showing an example of the structure of a hollow glass ball used as a filler in the thick insulating film coated conductor according to Embodiment 2. A schematic cross-sectional view showing an example of the configuration of an insulated switchgear according to Embodiment 3.

[0013] The following describes in detail, with reference to the drawings, a thick insulating film coated conductor, a method for manufacturing the same, and an insulated switchgear according to embodiments of the present disclosure.

[0014] Embodiment 1. Figure 1 is a schematic cross-sectional view showing an example of the configuration of a thick-walled insulating film coated conductor according to Embodiment 1. The thick-walled insulating film coated conductor 1 comprises a metal conductor 11, one or more first photocurable resin layers 12 in close contact with the metal conductor 11, and one or more second photocurable resin layers 13 in close contact with the first photocurable resin layer 12. In one example, the metal conductor 11 has a linear structure extending in one direction, but the shape of the metal conductor 11 is not limited to this. The first photocurable resin layer 12 is formed to cover the side surface of the linear metal conductor 11. The second photocurable resin layer 13 is formed to cover the side surface of the metal conductor 11 on which the first photocurable resin layer 12 is formed. In other words, as shown in Figure 1, in a cross-section perpendicular to the extending direction of the metal conductor 11, the thick-walled insulating film coated conductor 1 has a structure in which the first photocurable resin layer 12 and the second photocurable resin layer 13 are sequentially laminated on the surface of the metal conductor 11. The resin compositions used in the first photocurable resin layer 12 and the second photocurable resin layer 13 are described below.

[0015] The first photocurable resin layer 12 is a radical-polymerized silicone, a silicone polymer having an acrylic group in its molecular structure as shown in formula (1). Here, the composition of the silicone having an acrylic group is not particularly limited.

[0016]

[0017] A silicone containing acrylic groups hardens under a photopolymerization initiator by a radical polymerization reaction of the acrylic groups. Because it hardens immediately after light irradiation, the cycle time can be shortened. In particular, when trying to increase the thickness of the insulating layer on the surface of a metal conductor 11, there is a limit to the thickness of the resin that can be achieved in a single application, so it is necessary to repeat the application and curing of the first photocurable resin layer 12 multiple times. The thicker the required thickness of the first photocurable resin layer 12, the longer the work time. Furthermore, in order to obtain even higher insulating strength, it is desirable that the thickness of the first photocurable resin layer 12 be 2 mm or more. By using a silicone polymer containing acrylic groups as the first photocurable resin layer 12, the curing time for a single application can be shortened, thus reducing the overall work time and increasing productivity.

[0018] However, silicone polymers with radical polymerization-type acrylic groups react with oxygen in the air when irradiated with light in the air, resulting in oxygen inhibition. Therefore, the resin surface cannot be completely cured. While oxygen inhibition can occur in the first layer or subsequent layers, the subsequent layers can be cured by light curing. However, if oxygen inhibition occurs in the final layer, the resin cannot be completely cured, leaving a sticky residue on the resin surface and preventing tack-free application.

[0019] To solve this problem, there is a method of curing by light irradiation in an inert gas atmosphere. An example of an inert gas is nitrogen. When using an inert gas, it is necessary to prepare equipment that can shield from oxygen and perform light irradiation. As a result, in addition to the inert gas, initial equipment investment is required, and the operating and maintenance costs of the equipment add up, creating a new problem of rising overall production costs. Therefore, in Embodiment 1, one or more oxygen-free second photocurable resin layers 13 are provided around the first photocurable resin layer 12.

[0020] The second photocurable resin layer 13 is a UV (UltraViolet)-added silicone. The molecular structure of this UV-added silicone is shown in equation (2).

[0021]

[0022] As shown in equation (2), the second photocurable resin layer 13 is a silicone polymer having vinyl groups or a silicone polymer having H groups. The silicone polymer having vinyl groups or the silicone polymer having H groups hardens by a hydrosilylation reaction under a photoactivating catalyst. Since oxygen inhibition does not occur with this UV-added silicone, it hardens completely even when irradiated with light in air. As a result, tack-free surface can be achieved without any stickiness remaining on the resin surface. However, unlike the first photocurable resin layer 12, the second photocurable resin layer 13 hardens gradually after light irradiation begins, and it takes some time to fully harden. For this reason, if multiple layers of the second photocurable resin layer 13 are provided when increasing the thickness, the work time increases and production efficiency deteriorates. Therefore, one or more layers of the second photocurable resin layer 13 may be provided to achieve a tack-free surface on the resin, but even forming just one layer on the outermost layer of the first photocurable resin layer 12 is effective. The thickness of the second photocurable resin layer 13 is not particularly limited, but it is desirable to have a thickness of 10 μm or more in order to achieve tack-free resin surface.

[0023] In Embodiment 1, the elastic modulus of the first photocurable resin layer 12 after curing is set to 500 MPa or less. If the elastic modulus of the first photocurable resin layer 12 after curing is higher than 500 MPa, cracks may occur due to thermal stress in operating environments with heat cycles or large temperature fluctuations. By setting the elastic modulus of the first photocurable resin layer 12 after curing to 500 MPa or less, it is possible to suppress delamination of the contact interface between the metal conductor 11 and the first photocurable resin layer 12 due to thermal stress generated by operating environments such as heat cycles, or the occurrence of cracks within the first photocurable resin layer 12. As a result, it is possible to suppress the occurrence of discharge and prevent a decrease in dielectric strength.

[0024] Furthermore, in Embodiment 1, an adhesive layer may be provided between the metal conductor 11 and the first photocurable resin layer 12 to bond the metal conductor 11 and the first photocurable resin layer 12. Normally, the metal conductor 11 and the first photocurable resin layer 12 become tightly bonded during the photocuring process, but there is a possibility of delamination after the heat cycle. For this reason, it is desirable to provide an adhesive layer to further improve adhesion. A silane coupling agent can be used as the adhesive layer. In this case, by having a vinyl group or an acryloyl group as part of the structure of the silane coupling agent, that is, by using a silane coupling agent having a vinyl group or an acryloyl group, the adhesion between the metal conductor 11 and the first photocurable resin layer 12 can be improved, and the adhesive effect can be further enhanced. As described above, by providing an adhesive layer, the adhesion between the metal conductor 11 and the first photocurable resin layer 12 can be improved, and discharge can be suppressed.

[0025] Next, a method for manufacturing the thick-walled insulating film coated conductor 1 according to Embodiment 1 will be described. The method for manufacturing the thick-walled insulating film coated conductor 1 includes a first coating step, a first photocuring step, a second coating step, and a second photocuring step. Each step will be described below.

[0026] In the first coating step, a liquid, i.e., liquid first photocurable resin is uniformly applied to the surface of a metal conductor 11 that is rotating around its center of rotation as the axis of rotation, by dripping it onto the surface. In one example, the metal conductor 11 is an amorphous conductor. The first photocurable resin is a radical polymerization type silicone and comprises a silicone polymer having an acrylic group as shown in formula (1) in its molecular structure, and a photopolymerization initiator.

[0027] In the first photocuring step, a liquid first photocurable resin uniformly applied to the surface of the metal conductor 11 is cured while being irradiated with light. At this time, the silicone having acrylic groups hardens immediately after light irradiation by a radical polymerization reaction of the acrylic groups under the photopolymerization initiator. This forms the first photocurable resin layer 12. The thickness of the first photocurable resin layer 12 formed at this time is determined by the viscosity of the liquid first photocurable resin.

[0028] If the thickness of the initial layer is smaller than the desired thickness, it is necessary to form a further first photocurable resin layer 12. When forming two or more first photocurable resin layers 12, the first coating step and the first photocuring step are repeated in the same manner as for the initial layer to form multiple first photocurable resin layers 12. This allows for obtaining one or more first photocurable resin layers 12 of the desired thickness.

[0029] After the first photocurable resin layer 12 is formed, in the second coating step, a liquid second photocurable resin is uniformly applied to the surface of the first photocurable resin layer 12 formed on the surface of the metal conductor 11 by dripping it. The second photocurable resin includes a silicone polymer having vinyl groups or a silicone polymer having H groups, which is a UV-added silicone, and a photoactivating catalyst.

[0030] In the second photocuring step, a liquid second photocurable resin, uniformly applied to the surface of the first photocurable resin layer 12, is cured while being irradiated with light. At this time, the silicone polymer having vinyl groups or the silicone polymer having H groups is cured by a hydrosilylation reaction under a photoactivating catalyst, so that UV-added silicone does not experience oxygen inhibition and is completely cured in air. This forms the first layer of the second photocurable resin layer 13. The thickness of the first layer of the second photocurable resin layer 13 formed at this time is determined by the viscosity of the liquid second photocurable resin layer 13.

[0031] If the thickness of the first layer is smaller than the desired thickness, it is necessary to form a further second photocurable resin layer 13. When forming two or more second photocurable resin layers 13, the second coating step and the second photocuring step are repeated in the same manner as for the first layer to form multiple second photocurable resin layers 13. This allows for the formation of one or more second photocurable resin layers 13 of the desired thickness. As a result, a thick insulating film coated conductor 1 is obtained in which the first photocurable resin layer 12 and the second photocurable resin layer 13 are sequentially laminated on the surface of the metal conductor 11.

[0032] In Embodiment 1, the viscosity of the liquid first photocurable resin and the liquid second photocurable resin, i.e., the viscosity of the liquid resin before curing of the first photocurable resin layer 12 and the second photocurable resin layer 13, is set to 0.5 Pa·s or more and 20 Pa·s or less. If the viscosity of the liquid resin before curing is lower than 0.5 Pa·s, degassing before curing by light irradiation is easy, and voids in the resin can be removed before curing, but the thickness of the resin layer that can be cured in one application will be thinner, and the number of applications required to achieve the desired thickness will increase. In other words, the time required to obtain the first photocurable resin layer 12 and the second photocurable resin layer 13 of the desired thickness will be longer. On the other hand, if the viscosity of the liquid resin is higher than 20 Pa·s, the thickness of the resin layer that can be cured in one application can be increased, but degassing before curing by light irradiation becomes difficult. If voids remain, the pressure resistance of the insulating layers, the first photocurable resin layer 12 and the second photocurable resin layer 13, will deteriorate. Therefore, by setting the viscosity of the liquid resin before curing of the first photocurable resin layer 12 and the second photocurable resin layer 13 to 0.5 Pa·s or more and 20 Pa·s or less, degassing is easy, and voids inside the first photocurable resin layer 12 and the second photocurable resin layer 13 can be removed before curing. In addition, because it has a constant viscosity, the resin thickness can be increased when applied to the metal conductor 11. In other words, the thickness of the first photocurable resin layer 12 and the second photocurable resin layer 13 that can be formed in a single application can be increased. As a result, a thick-walled insulating film coated conductor 1 that achieves both void-free and thick-walled properties can be obtained.

[0033] Furthermore, the first photocurable resin layer 12 and the second photocurable resin layer 13 of Embodiment 1 are cured by light irradiation, and infrared rays, visible light, ultraviolet rays, X-rays, electron beams, alpha rays, beta rays, gamma rays, etc., can be used as the irradiated light. Needless to say, the necessary light rays are selected according to the resin material used.

[0034] As described above, the thick insulating film coated conductor 1 according to Embodiment 1 comprises a metal conductor 11, one or more first photocurable resin layers 12 in close contact with the metal conductor 11, and one or more second photocurable resin layers 13 in close contact with the first photocurable resin layers 12. One or more first photocurable resin layers 12 made of a silicone polymer having acrylic groups are used on the outer periphery of the metal conductor 11. In addition, one or more second photocurable resin layers 13 made of a silicone polymer having vinyl groups or a silicone polymer having H groups are used on the outer periphery of the first photocurable resin layers 12. By using the thick insulating film coated conductor 1 as a conductor in an insulated switchgear that uses a hybrid insulation method that combines solid insulation and gas insulation, the environmental burden on the insulated switchgear can be reduced, and the decrease in dielectric strength can be suppressed while increasing the thickness of the insulating layer.

[0035] Furthermore, even if minute protrusions exist on the surface of the metal conductor 11, the first photocurable resin layer 12 can be formed along these minute protrusions. As a result, minute gaps are not formed near the minute protrusions on the surface of the metal conductor 11. In other words, since minute gaps are not formed, the occurrence of discharge in these minute gaps is suppressed, and the decrease in dielectric strength is also suppressed.

[0036] Furthermore, the method for manufacturing the thick insulating film coated conductor 1 according to Embodiment 1 includes: a first coating step of dripping a liquid first photocurable resin onto the surface of a metal conductor 11 rotating with the rotation center as the axis of rotation; a first photocuring step of curing the first photocurable resin applied to the metal conductor 11 by light irradiation to form a first photocurable resin layer 12; a second coating step of dripping a liquid second photocurable resin onto the surface of the first photocurable resin layer 12 while rotating the metal conductor 11 on which the first photocurable resin layer 12 is formed; and a second photocuring step of curing the second photocurable resin applied to the first photocurable resin layer 12 by light irradiation to form a second photocurable resin layer 13. Here, the first photocurable resin is a silicone polymer having acrylic groups. As a result, the first photocurable resin layer 12, which is the layer formed on the inside, solidifies instantaneously when irradiated with light due to the high reactivity of the acrylic groups. As a result, the thickness of the first photocurable resin layer 12 can be increased, and the time required to form one layer of the first photocurable resin layer 12 can be shortened. In other words, the time required for each coating can be reduced, thereby increasing the productivity of the coating work. Furthermore, the second photocurable resin is made of a silicone polymer having vinyl groups or a silicone polymer having H groups. This makes it possible to achieve tack-free surface on the cured second photocurable resin layer 13 without oxygen inhibition. In addition, since it is not necessary to cure by light irradiation in an inert gas atmosphere, there is no need to prepare equipment that can perform light irradiation while shielding from oxygen. Furthermore, no mold is required, and it can be applied to various shapes of metal conductors 11. For this reason, the manufacturing cost of the thick insulating film coated conductor 1 can be reduced.

[0037] Furthermore, the technology described in Patent Document 2 does not mention the use of a resin having acrylic groups and Si-H groups, i.e., a silicone polymer having acrylic groups, in the first layer. Therefore, even if the technology described in Patent Document 2 is applied to the formation of the thick insulating film coated conductor 1, the instantaneous effect of the first layer corresponding to the first photocurable resin layer 12 is difficult. For this reason, when forming multiple layers to increase thickness, the time required to form the first layer becomes longer, resulting in lower efficiency. In contrast, in Embodiment 1, by using a silicone polymer having acrylic groups in the first photocurable resin layer 12, the instantaneous effect of the first photocurable resin layer 12 is facilitated, and the time required to form the first photocurable resin layer 12 can be shortened compared to when the technology described in Patent Document 2 is applied.

[0038] Embodiment 2. Figure 2 is a schematic cross-sectional view showing an example of the configuration of a thick-walled insulating film coated conductor according to Embodiment 2. In Figure 2, the same reference numerals are used for components identical to those in Figure 1 of Embodiment 1, and their descriptions are omitted. The thick-walled insulating film coated conductor 1A according to Embodiment 2 further comprises a flake-shaped filler 14 as a filler. The properties and functions of the flake-shaped filler 14 will be described below.

[0039] In the example shown in Figure 2, the flake-shaped filler 14 is added to the first photocurable resin layer 12, that is, the flake-shaped filler 14 is dispersed in the first photocurable resin layer 12. However, the flake-shaped filler 14 only needs to be dispersed in at least one of the first photocurable resin layer 12 and the second photocurable resin layer 13.

[0040] Examples of flake-shaped fillers 14 include silica, mica, glass, alumina, and boron nitride, but are not limited to these. The aspect ratio of the flake-shaped filler 14 is preferably in the range of 10 to 1000. If the aspect ratio is less than 10, the effect of improving the voltage resistance will be reduced. If the aspect ratio is greater than 1000, the diameter of the filler will be larger, potentially blocking the light rays during the curing process by light irradiation, resulting in insufficient curing. Therefore, by setting the aspect ratio of the flake-shaped filler 14 to the range of 10 to 1000, a thick-walled insulating film coated conductor 1A with improved voltage resistance can be obtained without blocking the light rays during light irradiation. Here, the aspect ratio is the value obtained by dividing the average particle size of the flake-shaped filler 14 by its average thickness. Furthermore, it is desirable that the flake-shaped filler 14 be oriented along the surface of the metal conductor 11, that is, that the surface with the largest area of ​​the flake-shaped filler 14 is oriented along the surface of the metal conductor 11. By oriented the flake-shaped filler 14 having the above aspect ratio along the surface of the metal conductor 11, the effect of improving the dielectric strength is enhanced compared to when the flake-shaped filler 14 is not oriented along the surface of the metal conductor 11.

[0041] The amount of flake-shaped filler 14 to be filled is preferably 5 vol% or more and 50 vol% or less. This is because if the amount of filling is too low, the effect of improving pressure resistance cannot be obtained. Also, if the amount of filling is too high, the viscosity will be too high, making degassing impossible. Here, the amount of filling is the amount of flake-shaped filler 14 to be added to at least one of the layers, namely the first photocurable resin layer 12 and the second photocurable resin layer 13.

[0042] The thick insulating film coated conductor 1A according to Embodiment 2 is basically manufactured using the same procedure as the manufacturing method for the thick insulating film coated conductor 1 described in Embodiment 1. However, when applying the first photocurable resin layer 12 or the second photocurable resin layer 13, the flake-shaped filler 14 is uniformly added to the liquid first photocurable resin or the liquid second photocurable resin. Specifically, in the first coating step, the liquid first photocurable resin layer 12 with the flake-shaped filler 14 uniformly added is applied by dripping around the metal conductor 11, or in the second coating step, the liquid second photocurable resin with the flake-shaped filler 14 uniformly added is applied by dripping around the first photocurable resin layer 12 formed around the metal conductor 11. At this time, since the flake-shaped filler 14 is originally in the form of thin flakes, it is naturally oriented along the surface of the metal conductor 11 or along the surface of the first photocurable resin layer 12 or the second photocurable resin layer 13 after curing. One reason for this is the shape of the flake-shaped filler 14 as described above, and another reason is that liquid resins usually have high surface tension, and this surface tension acts to cause the surface with the largest area of ​​the flake-shaped filler 14 to align with the cutting direction of the surface of the metal conductor 11 or the surface of the first photocurable resin layer 12 or the second photocurable resin layer 13 after curing. The flake-shaped filler 14 oriented in this manner can increase the dielectric strength of the first photocurable resin layer 12 or the second photocurable resin layer 13.

[0043] Also, in FIG. 2, the flaky filler 14 is used as the filler, but the hollow glass ball 15 may be used instead of the flaky filler 14. The same effect can be obtained by this. FIG. 3 is a cross-sectional view schematically showing an example of the structure of the hollow glass ball used as the filler in the thick insulating film-coated conductor according to the second embodiment. As shown in FIG. 3, the hollow glass ball 15 has a hollow inside the glass ball. Generally, the lower the dielectric constant of the insulating layer, the higher the partial discharge initiation voltage and the better the insulation withstand voltage. By making the glass ball hollow, the dielectric constant becomes lower than that of the solid glass ball. By adding and dispersing such a hollow glass ball 15 in at least one of the first photocurable resin layer 12 and the second photocurable resin layer 13, the dielectric constant of the first photocurable resin layer 12 or the second photocurable resin layer 13 can be lowered. As a result, the partial discharge initiation voltage when a voltage is applied to the metal conductor 11 can be increased. As a result, discharge can be suppressed and the insulation life can be prolonged.

[0044] It is desirable that the particle size of the hollow glass ball 15 be 100 μm or less. If the particle size of the hollow glass ball 15 is larger than 100 μm, there is a possibility that discharge will occur inside the hollow glass ball 15. The reason for this is as follows: When a high voltage is applied to the first photocurable resin layer 12 and the second photocurable resin layer 13, which are insulating layers containing voids, partial discharge occurs if the electric field applied to the void is higher than the breakdown voltage of the gas inside the void. This partial discharge initiation voltage is affected by the size of the void, atmospheric pressure, etc. Generally, when the void is very small, the influence of the void on the partial discharge initiation voltage is small, but when the void becomes somewhat large, the influence becomes large. In Embodiment 1, when coating the first photocurable resin layer 12 and the second photocurable resin layer 13, it is not possible to control the size of the voids, so it is necessary to make them as void-free as possible. Here, when hollow glass balls 15 are added to the liquid first photocurable resin or the liquid second photocurable resin to lower the dielectric constant, the problem of discharge within the hollow glass balls 15 can be suppressed by controlling the particle size of the hollow glass balls 15. By using hollow glass balls 15 with a diameter of 100 μm or less, the dielectric constant of the first photocurable resin layer 12 and the second photocurable resin layer 13 can be lowered, and partial discharge can be suppressed.

[0045] The amount of hollow glass balls 15 to fill is preferably 5 vol% or more and 50 vol% or less. This is because if the amount of filling is too low compared to 5 vol%, the effect of improving pressure resistance will not be obtained, and if the amount of filling is too high compared to 50 vol%, the viscosity will become too high, making degassing impossible. Here, the amount of filling is the amount of filling in at least one of the layers to which the hollow glass balls 15 are added, namely the first photocurable resin layer 12 and the second photocurable resin layer 13.

[0046] As described above, the thick-insulating-film-coated conductor 1A according to Embodiment 2 contains the scaly filler 14 dispersed in at least one of the first photocurable resin layer 12 and the second photocurable resin layer 13, and the scaly filler 14 is oriented along the surface of the metal conductor 11 or the surface of the first photocurable resin layer 12 or the second photocurable resin layer 13 after curing. Thereby, the withstand voltage property of the thick-insulating-film-coated conductor 1A, that is, the insulation breakdown voltage can be further increased, and thus the miniaturization of the device to which the thick-insulating-film-coated conductor 1A is applied can be realized. Further, when forming the first photocurable resin layer 12 and the second photocurable resin layer 13, the dripping method of dripping the liquid first photocurable resin and the liquid second photocurable resin onto the surface of the amorphous conductor while rotating the metal conductor 11 with the rotation center as the rotation axis is adopted. Therefore, the scaly filler 14 is oriented such that the surface with the largest area conforms to the surface shape of the metal conductor 11. As a result, the withstand voltage property is increased.

[0047] Further, the thick-insulating-film-coated conductor 1A according to Embodiment 2 contains hollow glass balls 15 dispersed in at least one of the first photocurable resin layer 12 and the second photocurable resin layer 13. Thereby, the dielectric constant of the first photocurable resin layer 12 and the second photocurable resin layer 13 can be decreased, and partial discharge can be suppressed.

[0048] In the technique described in Patent Document 2, since there is no filler in the coating layer, there is a problem that the withstand voltage property is low. However, in Embodiment 2, the scaly filler 14 or the hollow glass balls 15 are added as the filler to at least one of the first photocurable resin layer 12 and the second photocurable resin layer 13. Thereby, the withstand voltage property of the thick-insulating-film-coated conductor 1A can be increased.

[0049] As described above, the insulation breakdown voltage of the thick-insulating-film-coated conductor 1A according to Embodiment 2 can be further increased, and thus the miniaturization of the device to which the thick-insulating-film-coated conductor 1A is applied can be realized.

[0050] Embodiment 3. Figure 4 is a schematic cross-sectional view showing an example of the configuration of an insulated switchgear according to Embodiment 3. As shown in Figure 4, the insulated switchgear 100 according to Embodiment 3 includes a circuit breaker 110, disconnectors 120, 130, a current transformer 140, an instrument transformer 150, and conductors 160, 170 connecting these parts. The insulated switchgear 100 also includes, but is not shown, a surge arrester, bushings, and cable heads. In the insulated switchgear 100 according to Embodiment 3, a thick insulating film coated conductor 1, 1A described in Embodiment 1 or 2 is provided on the outer circumference of the conductor 160 or conductor 170. That is, a thick insulating film coated conductor 1 is formed by sequentially laminating the first photocurable resin layer 12 and the second photocurable resin layer 13 described in Embodiment 1 onto the conductor 160 or conductor 170. Alternatively, the first photocurable resin layer 12 and the second photocurable resin layer 13 described in Embodiment 1 are sequentially laminated onto the conductor 160 or conductor 170, and the flake-shaped filler 14 or hollow glass ball 15 described in Embodiment 2 is added to at least one of the first photocurable resin layer 12 and the second photocurable resin layer 13 to form a thick insulating film coated conductor 1A. This increases the dielectric strength of the insulated switchgear 100, enabling miniaturization of the insulated switchgear 100 when SF6 gas is not used, as well as eliminating the need for SF6. It also improves the insulation reliability of the insulated switchgear 100.

[0051] As described above, according to Embodiment 3, the thick insulating film coated conductors 1 and 1A of Embodiment 1 or Embodiment 2 are used as high-voltage conductors for the insulated switchgear 100. This makes it possible to make the insulated switchgear 100 SF6-free and miniaturized. Furthermore, the insulation reliability of the insulated switchgear 100 can be improved.

[0052] The configurations shown in the above embodiments are examples only, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0053] 1, 1A Thick insulating film coated conductor, 11 Metal conductor, 12 First photocurable resin layer, 13 Second photocurable resin layer, 14 Scale-like filler, 15 Hollow glass ball, 100 Insulated switchgear, 110 Circuit breaker, 120, 130 Disconnector, 140 Current transformer, 150 Instrument transformer, 160, 170 Conductor.

Claims

1. A thick insulating film coated conductor comprising: a metal conductor; one or more first photocurable resin layers in close contact with the metal conductor; and one or more second photocurable resin layers in close contact with the first photocurable resin layer, wherein the first photocurable resin layer has a silicone polymer having acrylic groups, and the second photocurable resin layer has a silicone polymer having vinyl groups or a silicone polymer having H groups.

2. The thick insulating film coated conductor according to claim 1, further comprising flake-shaped fillers dispersed in at least one of the first photocurable resin layer and the second photocurable resin layer, wherein the flake-shaped fillers are oriented along the surface of the metal conductor.

3. The thick insulating film coated conductor according to claim 1, further comprising hollow glass balls dispersed in at least one of the first photocurable resin layer and the second photocurable resin layer.

4. The thick insulating film coated conductor according to any one of claims 1 to 3, characterized in that the elastic modulus of the first photocurable resin layer is 500 MPa or less.

5. The thick insulating film coated conductor according to any one of claims 1 to 4, further comprising an adhesive layer between the metal conductor and the first photocurable resin layer for bonding the metal conductor and the first photocurable resin layer.

6. The thick insulating film coated conductor according to claim 5, characterized in that the adhesive layer contains a silane coupling agent having vinyl groups or acryloyl groups in part of its structure.

7. An insulated switchgear characterized in that a thick insulating film coated conductor according to any one of claims 1 to 6 is used as a high-voltage conductor.

8. A method for manufacturing a thick insulating film coated conductor, comprising: a first coating step of dripping a liquid first photocurable resin onto the surface of a metal conductor rotating with a rotation center as the axis of rotation; a first photocuring step of curing the first photocurable resin applied to the metal conductor by light irradiation to form a first photocurable resin layer; a second coating step of dripping a liquid second photocurable resin onto the surface of the first photocurable resin layer while rotating the metal conductor on which the first photocurable resin layer has been formed; and a second photocuring step of curing the second photocurable resin applied to the first photocurable resin layer by light irradiation to form a second photocurable resin layer, wherein the first photocurable resin has a silicone polymer having an acrylic group, and the second photocurable resin has a silicone polymer having a vinyl group or a silicone polymer having an H group.

9. The method for manufacturing a thick insulating film coated conductor according to claim 8, characterized in that the viscosity of the liquid first photocurable resin and the liquid second photocurable resin before curing is 0.5 Pa·s or more and 20 Pa·s or less.

Images