Insulating film-coated conductor, method for manufacturing insulating film-coated conductor, and gas opening / closing device

Abstract

Provided is an insulating film-coated conductor (101) comprising a metal conductor (1) and an insulating film (10) formed so as to cover the metal conductor (1), wherein: the insulating film (10) has a plurality of layers; a first heat-shrinkable tube (2) disposed by being subjected to heat-shrinking on the outer periphery of the metal conductor (1), an insulating tape (3) disposed by being wound around the outer periphery of the first heat-shrinkable tube (2) and including a resin cured product (5) obtained by vacuum-impregnating and curing a liquid resin, and a second heat-shrinkable tube (4) disposed by being subjected to heat-shrinking on the outer periphery of the insulating tape (3), are formed in order from the metal conductor (1) side; and the elastic modulus of the first heat-shrinkable tube (2) is lower than the elastic modulus of the insulating tape (3) that includes the resin cured product (5).

Description

Insulating film coated conductor, method for manufacturing insulating film coated conductor, and gas switchgear

[0001] The present disclosure relates to an insulating film-coated conductor, a method for manufacturing an insulating film-coated conductor, and a gas switchgear.

[0002] In conventional gas switchgear, circuit breakers, disconnecting switches, busbars, lightning arresters, and instrument transformers are housed in a grounded metal tank. The metal tank is filled with insulating gas SF6. However, SF6 has a greenhouse effect that is said to be more than 20,000 times that of CO2, and has a very high global warming potential. For this reason, there has been a trend toward restricting its use in recent years. To reduce environmental impact, gas switchgear that does not use SF6 insulating gas is being developed and studied for practical application. For example, if dry air is used instead of SF6 insulating gas, the global warming potential would be zero, and this has attracted attention for practical application.

[0003] However, dry air has only one-third the dielectric strength of SF6 insulating gas. Therefore, to achieve the same level of insulation performance, a large insulation distance is required, resulting in a larger device. To address this issue, hybrid insulation methods that combine solid insulation and gas insulation are increasingly being adopted. In these cases, solid insulation is achieved by providing an insulating layer directly on the surface of the metal conductor. Covering the surface of a metal conductor with a solid insulator can improve insulation performance by: first, suppressing the supply of electrons from the surface of the metal conductor, thereby suppressing the sustained growth of discharge; and second, lowering the maximum electric field in the air. Regarding the second feature, a thin insulator is less effective; therefore, a thick insulating film is desirable to ensure sufficient insulation strength.

[0004] Conventionally, mica tape is wound to a predetermined thickness on the surface of the coil metal conductor to form a main insulating substrate layer, and a finishing tape made by bonding heat-shrinkable cloth tape and heat-shrinkable film tape is wound around the outside of the main insulating substrate layer in the coil end portion. Vacuum resin impregnation and heat treatment are then performed, and the finishing tape heat shrinks during the heat-hardening treatment, preventing leakage of the resin impregnated in the heat-shrinkable tape at the coil end portion, suppressing the generation of voids in the insulating material and increasing pressure resistance (see, for example, Patent Document 1).

[0005] Japanese Patent Application Publication No. 5-30626

[0006] Conventionally, leakage of liquid resin from gaps in the mica tape was prevented, preventing the formation of voids on the surface of the coil insulation material, which could lead to insulation defects. On the other hand, insulated switchgears that do not use SF6 insulating gas, the insulating layer covering the metal conductor must be thickened. However, thickening the insulating layer can cause significant thermal stress near the interface between the metal conductor and the insulating layer due to differences in thermal contraction rates. Depending on the operating environment, the thermal stress can cause separation at the contact interface between the two or cracks in the insulating layer, resulting in discharge and a decrease in dielectric strength.

[0007] Furthermore, if the surface of the metal conductor is rough, when a thick insulating film is applied, it is not possible to fit the insulating film to the minute protrusions on the surface of the metal conductor, which may result in the formation of minute gaps near the minute protrusions on the surface of the metal conductor.As a result, discharges may occur in these minute gaps, resulting in a problem of reduced dielectric strength.

[0008] Patent Document 1 only discloses a technique for wrapping a mica tape as a main insulating layer around the outside of a coil (insulating film coated conductor) that has been insulated by a thermosetting treatment after impregnation with a thermosetting resin, and wrapping a finishing tape around the end of the coil to prevent leakage of the resin during the impregnation treatment, but it has the problem of not being able to meet the demand for a thicker insulating layer.

[0009] Another problem was that there was no technology provided to prevent thermal stress, resulting from the difference in thermal shrinkage rate between the mica tape of the main insulating layer and the coil, which is a metal conductor, and thus interfacial peeling and cracking.There was also a problem in that there was no technology provided to allow the insulating film to conform to the protrusion shape of the metal conductor surface and adhere tightly without gaps.

[0010] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an insulating film-coated conductor, a method for manufacturing an insulating film-coated conductor, and a gas opening and closing device that can improve adhesion between a metal conductor and an insulating film and prevent interfacial peeling, cracks, and voids.

[0011] The insulating film coated conductor of the present disclosure is an insulating film coated conductor comprising a metal conductor and an insulating film formed to cover the metal conductor, wherein the insulating film has a plurality of layers, and comprises, in order from the metal conductor side, a first heat-shrinkable tube heat-shrunk and arranged around the outer periphery of the metal conductor, an insulating tape wound around the outer periphery of the first heat-shrinkable tube and containing a cured resin product formed by vacuum impregnation and curing of a liquid resin, and a second heat-shrinkable tube heat-shrunk and arranged around the outer periphery of the insulating tape, and the elastic modulus of the first heat-shrinkable tube is lower than the elastic modulus of the insulating tape containing the cured resin product. Furthermore, a method for manufacturing an insulating film-coated conductor according to the present disclosure includes the steps of: arranging the first heat-shrinkable tube around the outer periphery of the metal conductor; heat-shrinking the first heat-shrinkable tube; winding the insulating tape around the outer periphery of the first heat-shrinkable tube; arranging a second heat-shrinkable tube around the outer periphery of the insulating tape; heat-shrinking the second heat-shrinkable tube; vacuum-impregnating the insulating tape with a liquid resin; and heat-curing the liquid resin to form the cured resin in the insulating tape. Further, a gas switchgear according to the present disclosure uses the insulating film-coated conductor described above for a bus bar connecting components constituting the gas switchgear.

[0012] The insulating film-coated conductor, the method for manufacturing the insulating film-coated conductor, and the gas switchgear of the present disclosure can improve the adhesion between the metal conductor and the insulating film, and prevent interfacial peeling, cracks, and voids in the insulating film-coated conductor.

[0013] Fig. 1A is a cross-sectional view showing the configuration of an insulating film-coated conductor according to embodiment 1. Fig. 1B is a cross-sectional view showing a cross section of the insulating film-coated conductor shown in Fig. 1A taken along line Y-Y. Fig. 1B is a flowchart showing a method for manufacturing the insulating film-coated conductor shown in Fig. 1. Fig. 1 is a diagram showing an example of a comparison of the insulating strength performance between the insulating film-coated conductor shown in Fig. 1 and a comparative example. Fig. 1B is a cross-sectional view showing an example of a longitudinal configuration of the insulating film-coated conductor shown in Fig. 1A. Fig. 1B is a diagram showing the configuration of a gas switchgear using the insulating film-coated conductor shown in Fig. 1.

[0014] Embodiment 1. Fig. 1A is a cross-sectional view showing the configuration of an insulating film-coated conductor according to embodiment 1. Fig. 1B is a cross-sectional view showing a cross section of the insulating film-coated conductor shown in Fig. 1A taken along line Y-Y. Fig. 2 is a flowchart showing a method for manufacturing the insulating film-coated conductor shown in Fig. 1. Fig. 3 is a diagram showing an example comparing the insulating strength performance of the insulating film-coated conductor shown in Fig. 1 with that of a comparative example. Fig. 4 is a cross-sectional view showing an example of the longitudinal configuration of the insulating film-coated conductor shown in Fig. 1A. Fig. 5 is a diagram showing the configuration of a gas switchgear using the insulating film-coated conductor shown in Fig. 1. In the following description, the longitudinal direction of the insulating film-coated conductor 101 will be described as longitudinal direction X.

[0015] 1, the insulating film-coated conductor 101 is composed of a metal conductor 1 and an insulating film 10 formed to cover the metal conductor 1. The insulating film 10 is formed with a large thickness and has multiple layers, and is configured by sequentially arranging, from the metal conductor 1 side, a first heat-shrinkable tube 2, an insulating tape 3, a cured resin 5, and a second heat-shrinkable tube 4. The first heat-shrinkable tube 2 is configured with two layers: an inner layer 21 on the metal conductor 1 side and an outer layer 22 on the insulating tape 3 side. The cured resin 5 is formed by vacuum-impregnating the insulating tape 3 with a liquid resin and then heat-curing it; the cured resin 5 after vacuum impregnation and heat-curing and the insulating tape 3 cannot be distinguished in FIG. 1, so the same part is shown.

[0016] More specifically, during the heat shrinking process of the first heat shrinkable tube 2, the inner layer 21 melts and adheres tightly to the metal conductor 1, and the outer layer 22 shrinks due to the heat, enveloping and holding the inner layer 21. The inner layer 21 conforms to the protrusions on the surface of the metal conductor 1 and adheres tightly without any gaps, and also adheres tightly to the outer layer 22, so that it is held by the outer layer 22 without being blown away by the shrinkage force generated by the heat shrinkage of the outer layer 22.

[0017] A hot melt adhesive can be used for the inner layer 21 of the first heat shrinkable tube 2. For example, olefin-based, polyamide-based, polyester-based, rubber-based, or polyurethane-based hot melt materials can be used. The thickness after shrinkage is preferably in the range of 0.1 mm to 1 mm. This is because if the thickness after shrinkage is 1 mm or more, the inner layer 21 may melt and flow along the surface of the metal conductor 1 when the first heat shrinkable tube 2 is heat-shrunk. Furthermore, if the thickness after shrinkage is 0.1 mm or less, the inner layer 21 may melt and not be able to follow the small protrusions on the surface of the metal conductor 1 when the first heat shrinkable tube 2 is heat-shrunk.

[0018] On the other hand, the outer layer 22 of the first heat-shrinkable tube 2 can be made of radiation-modified polyolefin, ethylene propylene rubber, polyolefin-based elastomer, silicone rubber, fluoropolymer, electron beam cross-linked soft polyolefin, or soft polyvinyl chloride tube. The inner diameter of the first heat-shrinkable tube 2 is appropriately selected depending on the outer diameter of the metal conductor 1. For example, if the outer diameter of the metal conductor 1 is φK, the first heat-shrinkable tube 2 is selected so that the inner diameter before shrinking is larger than φK and the inner diameter after shrinking is smaller than φK.

[0019] Furthermore, when the outer diameter φK of the metal conductor 1 is not constant, it is desirable to use a high-shrink type first heat-shrink tube 2. For example, when the minimum outer diameter of the metal conductor 1 is φK1 and the maximum outer diameter is φK2, the first heat-shrink tube 2 is selected so that the inner diameter of the first heat-shrink tube 2 before shrinkage is φK2 or more and the inner diameter of the first heat-shrink tube 2 after shrinkage is φK1 or less.

[0020] The shrinkage start temperature of the first heat-shrinkable tube 2 is preferably in the range of 50° C. to 200° C. This is because if the heat-shrinkage temperature is lower than 50° C., shrinkage may begin at around room temperature, making it difficult to ensure storage and dimensional stability. If the heat-shrinkage temperature is higher than 200° C., the properties of the material may change due to heat.

[0021] The insulating tape 3 is wound around the outer periphery of the first heat-shrinkable tube 2. The insulating tape 3 plays an important role in determining the insulating strength of the insulating film-coated conductor 101. While the number of layers of the insulating tape 3 is not shown in the figure, at least one layer must be wound, and multiple layers can be wound depending on the required insulating strength of the insulating film-coated conductor 101. Furthermore, by appropriately adjusting the thickness of the insulating tape 3, the thickness of the insulating film 10 of the insulating film-coated conductor 101 can be adjusted as desired depending on the outer diameter of the metal conductor 1. The insulating tape 3 can be made of glass cloth, mica, film, nonwoven fabric, insulating paper, cloth substrate, or the like. Among these, glass cloth and mica are preferred due to their high mechanical strength.

[0022] The second heat-shrinkable tube 4 is placed around the insulating tape 3 and compresses the insulating tape 3 by heat shrinking. The wrapped insulating tape 3 has gaps, which contain air, but these gaps are easily compressed by the shrinking force of the second heat-shrinkable tube 4. This has the effect of preventing voids from forming when the liquid resin is later impregnated. Furthermore, the second heat-shrinkable tube 4 also functions as a decorative layer that smoothes the surface of the insulating film-coated conductor 101. The second heat-shrinkable tube 4 maintains the smoothness of the surface of the insulating film-coated conductor 101 without post-processing, thereby suppressing electric field enhancement and increasing the withstand voltage.

[0023] The second heat-shrinkable tube 4 may be made of radiation-modified polyolefin, ethylene propylene rubber, polyolefin elastomer, silicone rubber, fluoropolymer, electron beam cross-linked soft polyolefin, or soft polyvinyl chloride. The second heat-shrinkable tube 4 may be made of the same material as the outer layer 22 of the first heat-shrinkable tube 2.

[0024] The inner diameter of the second heat-shrinkable tube 4 is determined by the outer diameter of the insulating tape 3 wrapped around the outer periphery of the first heat-shrinkable tube 2. The method for determining the inner diameter of the second heat-shrinkable tube 4 may be the same as that for the first heat-shrinkable tube 2. The shrinkage initiation temperature of the second heat-shrinkable tube 4 is preferably in the range of 50°C to 200°C. This is because if the heat-shrinkable temperature is lower than 50°C, shrinkage may begin near room temperature, making it difficult to ensure storage and dimensional stability. Furthermore, if the heat-shrinkable temperature is higher than 200°C, the properties of the material may change due to heat.

[0025] The cured resin 5 is obtained by vacuum impregnating the insulating tape 3 with a liquid resin and then heat-curing it. The vacuum impregnation and heat-curing processes are performed after the first heat-shrinkable tube 2 is heat-shrunk around the outer periphery of the metal conductor 1, the insulating tape 3 is wrapped around the outer periphery of the first heat-shrinkable tube, and the second heat-shrinkable tube 4 is placed around the outer periphery of the insulating tape 3 and heat-shrunk. The elastic modulus of the first heat-shrinkable tube 2 is set to be lower than the elastic modulus of the insulating tape 3 containing the cured resin 5.

[0026] With the insulating tape 3 compressed by the thermal shrinkage of the second heat-shrinkable tube 4, the insulating tape 3 is impregnated with liquid resin in a reduced pressure atmosphere. After the liquid resin is impregnated, pressure is applied with air, nitrogen, or other gas, and the liquid thermosetting resin is impregnated into the gaps in the insulating tape 3, preventing the occurrence of voids that can cause insulation defects. When the insulating tape 3 impregnated with the liquid resin is heated, the curing reaction of the liquid resin progresses, and the insulating tape and resin harden together to form a composite.

[0027] From the viewpoint of preventing the occurrence of voids, it is preferable for the liquid resin to be solvent-free. Resins that can be used include epoxy resin, silicone resin, unsaturated polyester resin, and alkyd resin. Furthermore, since the lower the viscosity, the higher the impregnation ability, a reactive diluent can be added to these resins. Examples of reactive diluents include acrylate monomers, methacrylate monomers, styrene, vinyl toluene, diallyl phthalate, and monoepoxides. Vacuum impregnation of the insulating tape 3 has the effect of eliminating voids in the insulating film 10, thereby increasing the insulating strength.

[0028] Next, a method for manufacturing an insulating film-coated conductor according to the first embodiment will be described with reference to FIG. 2 . First, a first heat-shrinkable tube 2 is placed around the metal conductor 1 (step S201 in FIG. 2 ). Next, the first heat-shrinkable tube 2 is heat-shrunk (step S202 in FIG. 2 ). During this heat-shrinking process, the inner layer 21 of the first heat-shrinkable tube 2 melts and adheres closely to the metal conductor 1, and the outer layer 22 of the first heat-shrinkable tube 2 shrinks due to the heat, enveloping and holding the inner layer 21. The inner layer 21 conforms to the protrusions on the surface of the metal conductor 1, adhering tightly to the metal conductor 1, and also adheres tightly to the outer layer 22. The inner layer 21 is held by the outer layer 22 without being displaced by the shrinkage force generated by the heat shrinkage of the outer layer 22.

[0029] Next, insulating tape 3 is wound around the outer periphery of the first heat-shrinkable tube (step S203 in FIG. 2). Next, second heat-shrinkable tube 4 is placed on the outside of insulating tape 3 (step S204 in FIG. 2). Next, second heat-shrinkable tube 4 is heat-shrunk (step S205 in FIG. 2). Next, liquid resin is vacuum-impregnated into insulating tape 3 (step S206 in FIG. 2). Next, the liquid resin impregnated into insulating tape 3 is heat-cured to form cured resin 5 within insulating tape 3 (step S207 in FIG. 2). Through the above steps, insulating film-coated conductor 101 according to embodiment 1 is manufactured.

[0030] Next, an example of the insulation strength of the insulating film-coated conductor manufactured as described above will be described with reference to FIG. 3 . The method for measuring the insulation strength is as follows. First, the insulating film-coated conductor 101 or a comparative example is coaxially arranged in a cylindrical metal container filled with dry air. Then, a measurement voltage is applied between the metal conductor and the cylindrical metal container to measure the breakdown voltage. The "breakdown voltage" measured in this manner is shown on the vertical axis. On the horizontal axis, S1 and S2 represent the "insulating film-coated conductor without the first heat-shrinkable tube 2" as a comparative example, and G1 and G2 represent the "insulating film-coated conductor 101 with the first heat-shrinkable tube 2" similar to the first embodiment.

[0031] In order to compare these, the insulating film of the comparative example needs to have the same thickness as the insulating film 10 of the insulating film-coated conductor 101 of embodiment 1. Therefore, in the example of the "comparative example without the first heat-shrinkable tube 2," the thickness of the insulating tape 3 (and the cured resin 5) is made thicker by the thickness corresponding to the absence of the first heat-shrinkable tube 2. Furthermore, S1 and G1 show the results before the heat cycle test, and S2 and G2 show the results after the heat cycle test.

[0032] The conditions for the heat cycle test conducted here were a low-temperature condition of −25° C. for 30 minutes, and a high-temperature condition of 120° C. for 30 minutes, with a temperature increase or decrease time of 60 minutes, for 10 cycles. As shown in Fig. 3, a comparison of the breakdown voltages G1 before the heat cycle test for the insulating film-coated conductor 101 using the first heat-shrinkable tube 2 and S1 before the heat cycle test for the comparative example in which the first heat-shrinkable tube 2 was not used clearly shows that the insulation strength of the insulating film-coated conductor 101 using the first heat-shrinkable tube 2 was approximately 25% greater than the insulation strength of the comparative example in which the first heat-shrinkable tube 2 was not used.

[0033] Furthermore, in the case of the insulating film-coated conductor 101 using the first heat-shrinkable tube 2, a comparison of the breakdown voltages G2 after the heat cycle test and G1 before the heat cycle test makes it clear that the breakdown voltage of the insulating film-coated conductor 101 using the first heat-shrinkable tube 2 does not change significantly before and after the heat cycle test. In contrast, in the case of the comparative example not using the first heat-shrinkable tube 2, a comparison of the breakdown voltages S1 of the comparative example before the heat cycle test and S2 of the comparative example after the heat cycle test makes it clear that the breakdown voltage of the comparative example not using the first heat-shrinkable tube 2 decreased by about 30% before and after the heat cycle test.

[0034] As described above, according to the first embodiment of the present disclosure, there is provided an insulating film-coated conductor 101 including a metal conductor 1, a first heat-shrinkable tube 2 having a two-layer structure that is disposed around the metal conductor 1 and heat-shrunk, an insulating tape 3 wrapped around the first heat-shrinkable tube 2, and a second heat-shrinkable tube 4 that is disposed around the insulating tape 3 and heat-shrunk, and including a cured resin 5 that is vacuum-impregnated with a liquid thermosetting resin and then heat-cured, wherein the first heat-shrinkable tube 2 has an inner layer 21 that melts during heat shrinkage and adheres to the surface of the metal conductor 1, and an outer layer 22 that heat-shrinks to hold the inner layer 21, but has a lower elastic modulus than the insulating tape 3 that includes the cured resin 5 that is vacuum-impregnated and heat-cured. The low elastic modulus of the first heat-shrinkable tube 2 thus enhances adhesion between the metal conductor 1 and the insulating film 10, prevents interfacial peeling and cracking, and increases insulation strength.

[0035] Furthermore, the insulating tape 3 of the first embodiment of the present disclosure can achieve even higher insulating strength by forming multiple layers with a thickness of 2 mm or more. The thickness of the insulating film 10 is preferably in the range of 0.1 to 5 times the outer diameter of the metal conductor 1. If it is 0.1 times or less, the thickness is insufficient and the effect of reducing the maximum electric field in the air is small. If it is 5 times or more, heat dissipation, mechanical properties, manufacturability, etc. may be impaired. Therefore, the thickness of the insulating film 10 can be easily adjusted by adjusting the number of layers (number of windings) of the insulating tape 3, etc.

[0036] Although not shown in detail in the first embodiment, a case will be described in which the thickness or number of layers of the insulating tape 3 to be wound is changed depending on the difference in the outer diameter of the metal conductor 1 in the longitudinal direction X of the metal conductor 1. Details of this case will be explained below with reference to Fig. 4. In Fig. 4, the same parts as in Fig. 1 are given the same reference numerals, and their explanation will be omitted. Note that Fig. 4 has the same configuration as Fig. 1, but for convenience, only four parts in Fig. 1 are shown: the metal conductor 1, the first heat-shrinkable tube 2, the insulating tape 3, and the second heat-shrinkable tube 4.

[0037] In the figure, the center line ML of the longitudinal direction X of the metal conductor 1 is taken as the center line. Points A and B are any two points on the center line ML. φA and φB indicate the outer diameter of the metal conductor 1 at points A and B. TA1 and TB1 indicate the thickness of the first heat-shrinkable tube 2 after heat shrinkage at points A and B. TA2 and TB2 indicate the thickness of the insulating tape 3 at points A and B. TA3 and B3 indicate the thickness of the second heat-shrinkable tube 4 at points A and B. Although not shown, the outer diameter of the first heat-shrinkable tube 2 before heat shrinkage is indicated as φC.

[0038] As shown in FIG. 4, it is assumed that the relationship between the diameters φA and φB is expressed by the following formula (1): φB>φA (1)

[0039] Then, the shrinkage rates αA and αB of the first heat-shrinkable tube 2 at points A and B during heat shrinkage are calculated according to the following formulas (2) and (3): αA=(φC−φA) / φC (2) αB=(φC−φB) / φC (3)

[0040] The following relationship can be obtained from the relationships between the above-mentioned formulas (1), (2) and (3): αB<αA (4)

[0041] From the relationship of formula (4), the following relationship can be obtained for the thickness of the first heat-shrinkable tube 2 at points A and B: TB1<TA1 (5)

[0042] The above describes the relationship between the thickness of the first heat-shrinkable tube 2 after heat shrinkage and the outer diameter of the metal conductor 1. A similar relationship exists for the second heat-shrinkable tube 4. That is, where the outer diameter of the metal conductor 1 in the longitudinal direction X is large, the heat shrinkage rates of the first heat-shrinkable tube 2 and the second heat-shrinkable tube 4 after heat shrinkage are small, and their respective thicknesses are small. Therefore, in order to maintain a constant insulating strength in the longitudinal direction X of the metal conductor 1, it is desirable to maintain a constant thickness of the insulating film 10, including the first heat-shrinkable tube 2, the insulating tape 3, the cured resin 5, and the second heat-shrinkable tube 4, in the longitudinal direction X of the insulating film-coated conductor 101. While it is usually difficult to achieve this by changing the thickness of the material of the first heat-shrinkable tube 2 and the second heat-shrinkable tube 4 itself in the longitudinal direction X, this can be easily achieved by adjusting the number of layers (number of windings) of the insulating tape 3.

[0043] That is, where the outer diameter of the metal conductor 1 in the longitudinal direction X is large, the thickness of the first heat-shrinkable tube 2 and the second heat-shrinkable tube 4 after heat shrinking will be smaller than where the outer diameter is small, so the number of layers of insulating tape 3 should be increased. Conversely, where the outer diameter of the metal conductor 1 is small, the number of layers of insulating tape 3 should be fewer than where the outer diameter is large. This relationship can be expressed by the following equation: TB2>TA2 (6)

[0044] It is desirable to change the number of layers of the insulating tape 3 so as to satisfy the following relationship: TA1+TA2+TA3=TB1+TB2+TB3 (7)

[0045] As described above, even if the outer diameter of the metal conductor 1 changes in the longitudinal direction X, by appropriately changing the thickness of the insulating tape 3 depending on the thickness of the first heat-shrinkable tube 2 and the second heat-shrinkable tube 4 after heat shrinkage, the total thickness of the insulating film 10, which is the first heat-shrinkable tube 2, the second heat-shrinkable tube 4, and the insulating tape 3, becomes constant in the longitudinal direction X of the insulating film-coated conductor 101. This makes it possible to make uniform and increase the insulation strength of the insulating film-coated conductor 101 in the longitudinal direction X.

[0046] Next, a gas switchgear 100 using the insulating film-coated conductor 101 of the first embodiment described above will be described with reference to Fig. 5. As shown in Fig. 5, the gas switchgear 100 includes various components, such as a circuit breaker 110, disconnectors 120 and 130, a current transformer 140, and a voltage transformer 150. It also includes bus bars 160 and 170 that connect these components. The gas switchgear 100 also includes other components, such as a lightning arrester, a bushing, and a cable head, which are not shown.

[0047] In the gas switchgear 100, the bus bars 160 (horizontal portion) and 170 (vertical portion) are formed using the insulating film-coated conductor 101 of the first embodiment described above. This increases the dielectric strength of the gas switchgear 100, reduces the need for insulating gas SF6, and reduces the size. Furthermore, the insulation reliability of the gas switchgear 100 can be improved.

[0048] According to the insulating film-coated conductor of embodiment 1 configured as described above, in the insulating film-coated conductor including a metal conductor and an insulating film formed to cover the metal conductor, the insulating film has a plurality of layers, and the layers are formed, in order from the metal conductor side, with: a first heat-shrinkable tube heat-shrunk and arranged around the outer periphery of the metal conductor; an insulating tape wound around the outer periphery of the first heat-shrinkable tube and containing a cured resin product formed by vacuum impregnation and curing of a liquid resin; and a second heat-shrinkable tube heat-shrunk and arranged around the outer periphery of the insulating tape, and the modulus of elasticity of the first heat-shrinkable tube is lower than the modulus of elasticity of the insulating tape containing the cured resin product, thereby improving adhesion between the metal conductor and the insulating film, and preventing interfacial peeling, cracks, and voids in the insulating film-coated conductor, and increasing insulation strength.

[0049] Furthermore, according to the insulating film-coated conductor of the first embodiment configured as described above, the first heat-shrinkable tube is formed of two layers, an inner layer on the metal conductor side and an outer layer on the outside of the inner layer, the inner layer is formed by melting and adhering to the outer periphery of the metal conductor, and the outer layer is formed by heat-shrinking to hold the inner layer. Therefore, by making the first heat-shrinkable tube placed on the outer periphery of the metal conductor have a two-layer structure of an inner layer and an outer layer, the inner layer can be melted and adhered to the surface of the metal conductor during heat-shrinkage, while the outer layer can be heat-shrunk to hold the inner layer. In addition, the elastic modulus of the first heat-shrinkable tube 2 can be made lower than the elastic modulus of an insulating tape having a vacuum-impregnated and cured resin cured product.

[0050] Furthermore, according to the insulating film-coated conductor of embodiment 1 configured as described above, the insulating tape is formed in multiple layers, and the thickness of the portion where the insulating tape is formed in the multiple layers is 2 mm or more, thereby increasing the insulating strength.

[0051] Furthermore, in the insulating film-coated conductor of the first embodiment configured as described above, the metal conductor has portions in its longitudinal direction where the outer diameter is different, and the thickness of the wound insulating tape is preset so that the portion in the longitudinal direction of the metal conductor where the outer diameter is larger is thicker than the portion in the longitudinal direction of the metal conductor where the outer diameter is smaller, thereby making it possible to make the thickness of the insulating film uniform, thereby increasing the insulating strength of the insulating film-coated conductor.

[0052] Furthermore, the method for manufacturing the insulating film-coated conductor of embodiment 1 configured as described above includes the steps of: arranging the first heat-shrinkable tube around the outer periphery of the metal conductor; heat-shrinking the first heat-shrinkable tube; winding the insulating tape around the outer periphery of the first heat-shrinkable tube; arranging a second heat-shrinkable tube around the outer periphery of the insulating tape; heat-shrinking the second heat-shrinkable tube; vacuum-impregnating the insulating tape with a liquid resin; and heat-curing the liquid resin to form the cured resin in the insulating tape. This makes it possible to improve adhesion between the metal conductor and the insulating film, prevent interfacial peeling, cracks, and voids in the insulating film-coated conductor, and increase insulation strength.

[0053] Furthermore, according to the gas switchgear of embodiment 1 configured as described above, the above-described insulating film-coated conductor is used for the busbar connecting each component constituting the gas switchgear, so that the gas switchgear is SF6-free, thereby reducing the environmental load and realizing miniaturization.

[0054] Although exemplary embodiments are described in this disclosure, the various features, aspects, and functions described in the embodiments are not limited to specific embodiments, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are anticipated within the scope of the technology disclosed in this specification. For example, variations in, addition to, or omission of at least one component are included.

[0055] REFERENCE SIGNS LIST 1 Metal conductor, 100 Gas switchgear, 101 Insulating film coated conductor, 110 Circuit breaker, 120 Disconnector, 130 Disconnector, 140 Current transformer, 150 Potential transformer, 160 Bus bar, 170 Bus bar, 2 First heat shrinkable tube, 21 Inner layer, 22 Outer layer, 3 Insulating tape, 4 Second heat shrinkable tube, 5 Resin cured product.

Claims

1. An insulating film-coated conductor comprising a metal conductor and an insulating film formed to cover the metal conductor, wherein the insulating film has a plurality of layers, and the insulating film comprises, in order from the metal conductor side, a first heat-shrinkable tube heat-shrunk and arranged around the outer periphery of the metal conductor, an insulating tape wound around the outer periphery of the first heat-shrinkable tube and containing a cured resin formed by vacuum impregnation and curing of a liquid resin, and a second heat-shrinkable tube heat-shrunk and arranged around the outer periphery of the insulating tape, and the elastic modulus of the first heat-shrinkable tube is lower than the elastic modulus of the insulating tape containing the cured resin.

2. The insulating film coated conductor according to claim 1, wherein the first heat-shrinkable tube is formed of two layers: an inner layer on the metal conductor side and an outer layer on the outside of the inner layer, the inner layer being formed by melting and adhering to the outer periphery of the metal conductor, and the outer layer being formed by heat shrinking to hold the inner layer.

3. An insulating film coated conductor according to claim 1 or claim 2, wherein the insulating tape is formed in multiple layers, and the thickness of the insulating tape at the location where the multiple layers are formed is 2 mm or more.

4. An insulating film coated conductor according to any one of claims 1 to 3, wherein the metal conductor has portions in its longitudinal direction where the outer diameter is different, and the thickness of the wound insulating tape is preset so that the thickness is thicker in the longitudinal direction of the metal conductor at portions where the outer diameter of the metal conductor is larger than at portions where the outer diameter of the metal conductor is smaller.

5. A method for manufacturing an insulating film-coated conductor according to any one of claims 1 to 4, comprising the steps of: arranging the first heat-shrinkable tube around the outer periphery of the metal conductor; heat-shrinking the first heat-shrinkable tube; winding the insulating tape around the outer periphery of the first heat-shrinkable tube; arranging a second heat-shrinkable tube around the outer periphery of the insulating tape; heat-shrinking the second heat-shrinkable tube; vacuum-impregnating the insulating tape with a liquid resin; and heat-curing the liquid resin to form the cured resin in the insulating tape.

6. A gas switchgear, in which the insulating film-coated conductor according to any one of claims 1 to 4 is used for a bus bar connecting each component constituting the gas switchgear.

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