JP5146247B2 - Solid cable intermediate connection structure - Google Patents

Description

  The present invention relates to an intermediate connection structure for connecting solid cables having an insulating layer impregnated with insulating oil. In particular, the present invention relates to an intermediate connection structure for a solid cable that can prevent the insulating oil from escaping from the connection portion insulating layer.

  As a long-distance, large-capacity DC power cable, a solid cable having an insulating layer in which kraft paper is wound around the outer periphery of a conductor and impregnated with high-viscosity insulating oil is used. In addition, as a solid cable capable of further increasing the operating temperature and capacity, a composite tape of polypropylene and kraft paper is wound and an insulating layer impregnated with medium viscosity insulating oil is provided. A solid cable has been proposed (Patent Document 1).

  In the case of forming a long-distance power line, an intermediate connection portion for connecting the solid cables is provided. This intermediate connection portion includes a connection portion called FJ (Factory joint) that is assembled in advance in a factory. The specific assembly procedure for FJ is as follows (see Fig. 1). (1) At the end of the cable core 1c of the solid cable 1, a part of the tape-like insulating material constituting the cable oil immersion insulating layer 11 is removed or unwound to expose the end of the conductor 10 → (2 ) Connect the exposed conductors 10 by welding, etc. → (3) Cable tape 1c is wound with another tape-like insulating material so as to fill the portion where the insulating material has been removed in the cable oil immersion insulating layer 11. The end portion of the conductor and the outer periphery of the conductor connecting portion 20 are covered, and the insulating material of the cable oil-insulated insulating layer 11 is rewound to form the connecting portion insulating layer 21. → (4) The metal sheath 22 → (5) Polyethylene (PE) tape is wound around the outer periphery of the metal sheath 22 and melted to form the anticorrosion layer 23 → (6) Further, a reinforcing layer 24, an exterior 25, and the like are provided.

  The connecting portion insulating layer 21 is formed by winding an insulating material impregnated with the same insulating oil as the cable insulating oil in advance. For example, the winding is performed while applying an insulating oil having a viscosity lower than that of the cable insulating oil. In addition, after forming the metal sheath 22, a hole is formed in a part of the metal sheath 22, and insulating oil is injected into the metal sheath 22 from the hole, and the insulating oil is interposed between the metal sheath 22 and the connection portion insulating layer 21. Meet. The same insulating oil as that used for the cable insulating oil is used. After injecting the insulating oil, the hole provided in the metal sheath 22 is closed.

Japanese Patent Laid-Open No. 11-224546

  However, in the conventional intermediate connection structure, there is a possibility that a deoiled portion is generated during the construction, and the presence of the deoiled portion may cause a decrease in insulation performance.

  As described above, when the anticorrosion layer is formed on the outer periphery of the metal sheath, heating is performed to melt the polyethylene tape. By this heating, the insulating oil impregnated in the connection portion insulating layer present on the inner peripheral side of the metal sheath, the insulating oil used for the sachet, the insulating oil injected after the formation of the metal sheath expands and moves, There is a risk of deoiling at the intermediate connection. For example, due to gravity, the insulating oil may move downward between the metal sheath and the connection portion insulating layer, and a deoiled portion may be generated on the upper side. In addition, the insulating oil impregnated in the connection part insulating layer may move to the metal sheath side (outer peripheral side) and escape to the gap between the metal sheath and the connection part insulating layer. A portion where the insulating oil does not exist due to deoiling becomes an electrical weak point portion, and the presence of such a deoiling portion may cause a deterioration in the insulation characteristics of the cable.

  Accordingly, one of the objects of the present invention is to provide an intermediate connection structure for a solid cable in which insulating oil does not easily escape from the connection portion insulating layer.

  The present invention achieves the above object by providing a high viscosity portion between the metal sheath and the connecting portion insulating layer. The intermediate connection structure of the solid cable according to the present invention relates to a connection structure for connecting solid cables having a cable oil immersion insulation layer on the outer periphery of the conductor, and the conductor and the cable oil immersion insulation layer covering the conductor are in stages. A pair of exposed cable cores, a conductor connecting portion, a connecting portion insulating layer, a metal sheath, and an anticorrosion layer. A conductor connection part is a location which connects the conductors exposed from the said cable oil-immersion insulating layer. The connecting part insulating layer is formed by winding a tape-like insulating material around the end of the cable core and the outer periphery of the conductor connecting part, and is impregnated with insulating oil. The metal sheath is formed on the outer periphery of the connection portion insulating layer. The anticorrosion layer is formed on the outer periphery of the metal sheath. The intermediate connection structure includes a high viscosity portion made of a material having a higher kinematic viscosity than the cable insulation oil impregnated in the cable oil immersion insulation layer between the metal sheath and the connection portion insulation layer. Yeah.

  When the constituent material of the anticorrosion layer is heated in forming the anticorrosion layer in the intermediate connection structure, the metal sheath and the constituent members existing on the inner peripheral side thereof are also heated. In particular, the high viscosity portion located immediately below the metal sheath is heated. However, the high-viscosity part is made of a material having a high kinematic viscosity, and thus is difficult to move by the heating. In addition, since the high-viscosity part that is difficult to move exists between the metal sheath and the connection part insulating layer, the insulating oil impregnated in the connection part insulating layer is heated and moved to the outer peripheral side. The high-viscosity part functions as an obstacle wall and tries to keep the insulating oil inside as much as possible from the high-viscosity part. Accordingly, it is possible to suppress the insulating oil or the like impregnated in the connecting portion insulating layer from moving into the gap between the metal sheath and the connecting portion insulating layer. In this way, the movement of the insulating oil impregnated in the connecting portion insulating layer can be reduced, and the high viscosity portion itself functions as an oil flow resistance element of the insulating oil existing in the gap, so that the intermediate connecting portion is deoiled. It can suppress that a location arises. Hereinafter, the present invention will be described in more detail.

Examples of the constituent material of the high viscosity portion include an insulating oil having a kinematic viscosity higher than that of the cable insulating oil. In particular, when the cable insulating oil is used as a medium viscosity oil as described later, a medium viscosity oil having a kinematic viscosity higher than that of the cable insulating oil is used, or the kinematic viscosity at 60 ° C. is 500 mm ² / s (500 cst) or more. High viscosity oil can be utilized. When such an insulating oil having a high kinematic viscosity is used, a high-viscosity part can be easily formed by applying before covering the metal sheath or injecting from a hole provided in the metal sheath. That is, as the insulating oil injected from the hole of the metal sheath, an insulating oil having a higher kinematic viscosity than the conventional one is used. When injecting, if the insulating oil is heated to reduce the viscosity, it is easy to inject.

  Alternatively, the high-viscosity part contains an insulating oil, and as the insulating oil, a configuration in which the same insulating oil as the cable insulating oil is used as a base oil, and a thickener is added to the base oil can be mentioned.

  According to the said structure, the insulating oil of desired kinematic viscosity can be obtained easily by adjusting content of a thickener with respect to base oil, or selecting the kinematic viscosity of base oil itself. In particular, the cable insulating oil is a medium-viscosity oil which will be described later, and it is preferable that the same insulating oil as the cable insulating oil is used as the base oil because the injection operation is easy. For example, base oils include polybuden oils with a wide product viscosity range. Any agent that can increase the viscosity of the insulating oil when mixed with the insulating oil can be used as the thickener, and examples thereof include polyisobutylene and a rubber-based material described later.

As one embodiment of the present invention, a configuration in which the cable insulating oil has a kinematic viscosity at 60 ° C. of 10 mm ² / s (10 cst) or more and less than 500 mm ² / s (500 cst) can be given. Moreover, the structure by which the insulating oil impregnated in the insulating material which comprises a connection part insulating layer is the same as the said cable insulating oil is mentioned.

  As the insulation oil impregnated in the cable insulation oil and the connection part insulation layer, the medium viscosity oil is used, and the oil immersion insulation layer of the cable and the connection insulation layer of the intermediate connection part are composed of a composite tape as will be described later. Therefore, the capacity can be increased by increasing the use temperature of the cable. Further, by using the above-mentioned medium viscosity oil, it is easy to impregnate the insulating material constituting the cable oil immersion insulating layer and the connection portion insulating layer as compared with the conventional high viscosity oil. As the insulating oil satisfying the above viscosity, for example, one selected from polystyrene insulating oil, mineral oil, synthetic oil mainly composed of alkylbenzene, and heavy alkylate, or a mixed oil of two or more of these can be used.

  As one form of this invention, the structure formed by winding the composite tape which has an insulating paper and a plastic layer for at least one part of a cable oil immersion insulating layer and at least one part of a connection part insulating layer is mentioned.

  The cable oil immersion insulating layer and the connecting portion insulating layer are formed by winding a tape-shaped insulating material. As this insulating material, it is preferable to use a composite tape having a plastic layer on one surface of insulating paper or a plastic tape having a plastic layer between two sheets of insulating paper. When a composite tape having a high thickness ratio (k value) of the plastic layer is used, the resistivity ρ is large and the insulating characteristics are high. A composite tape having a high k value can be produced, for example, by super calendering.

  In the intermediate connection structure of the solid cable of the present invention, oil removal is difficult to occur, the insulating oil can be sufficiently present on the inner peripheral side of the metal sheath, and the insulating property is excellent.

Embodiments of the present invention will be described below.
[Embodiment 1]
FIG. 1 is a schematic partial sectional view of an intermediate connection structure of a solid cable of the present invention. The solid cable 1 includes a conductor 10, a cable oil immersion insulating layer 11, a metal sheath 12, an anticorrosion layer 13, a reinforcing layer 14, and an exterior 15 in order from the center. The cable oil immersion insulating layer 11 is impregnated with insulating oil (cable insulating oil). The pair of solid cables 1 to be connected have the above-described constituent members stripped at the ends thereof. The intermediate connection structure 2 that connects the two cables 1 includes a conductor 10 and a cable oil-immersed insulating layer 11 covering the conductor 10 that are exposed in stages, and a pair of the exposed conductors 10. A conductor connecting portion 20 that connects the end portion of the cable core 1c and the outer periphery of the conductor connecting portion 20, a metal sheath 22 formed on the outer periphery of the connecting portion insulating layer 21, An anticorrosion layer 23 formed on the outer periphery of the metal sheath 22 is provided. The connection insulating layer 21 is also impregnated with insulating oil. The most characteristic feature of the intermediate connection structure 2 is that a high-viscosity portion (not shown) is provided between the metal sheath 22 and the connection portion insulating layer 21. Hereinafter, each structure is demonstrated centering on a high-viscosity part.

<Solid cable>
《Conductor etc.》
As the conductor 10, a so-called keystone conductor obtained by twisting a plurality of copper strands can be used. The metal sheath 12 is made of lead. The anticorrosion layer 13 is formed of a resin such as polyethylene (PE). The reinforcing layer 14 is a layer that shares the hoop stress applied to the metal sheath 12, and is configured by winding a belt-shaped material made of a high tensile strength material such as stainless steel. The exterior 15 can use an iron wire.

<Cable oil immersion insulation layer>
The cable oil immersion insulating layer 11 includes an internal semiconductive layer (not shown), a main insulating layer, and an external semiconductive layer (not shown) in order from the conductor 10 side. For example, the main insulating layer is formed by spirally winding a composite tape having a plastic layer between two sheets of insulating paper. As the composite tape, PPLP (registered trademark of Sumitomo Electric Industries, Ltd.) having a polypropylene (PP) layer between two kraft papers can be used. As this composite tape, a suitable tape having a PP layer thickness ratio (k value) of 40 to 90%, for example, a k-value increased by supercalendering can be used.

  In addition, if the main insulation layer has a low rho layer formed by wrapping kraft paper on the inner circumference side (just above the conductor) and the outer circumference side (just below the metal sheath), the main insulation layer is highly stressed and the influence of the conductor The stress which the part which is easy to receive can receive can be reduced.

As the cable insulation oil impregnated in the cable oil immersion insulation layer 11, for example, a medium viscosity polybutene oil (trade name: HV-15, manufactured by Nippon Petrochemical Co., Ltd.) having a kinematic viscosity at 60 ° C. of about 200 mm ² / s. Available.

  A cloth tape (not shown) woven with copper wire is wound around the outer periphery of the outer semiconductive layer in order to ensure conduction between the outer semiconductive layer and the metal sheath 12.

<Intermediate connection structure>
<Conductor connection, etc.>
The conductor connecting portion 20 is configured by welding the conductors 10 exposed from the end of the cable core 1c of each cable 1 or connecting the conductors 10 using a connecting sleeve. Similar to the cable 1, the outer periphery of the anticorrosion layer 23 includes a reinforcing layer 24 made of a stainless steel strip or the like, and an exterior 25 made of iron wire.

《Connection insulation layer》
The connection part insulating layer 21 is formed by winding a tape-like insulating material (PPLP (registered trademark)) similar to the cable oil-immersed insulation layer 11 around the outer periphery of the conductor connection part 20 and the end of the cable core 1c in a spiral manner. At the same time, a part of the insulating material constituting the cable oil immersion insulating layer 11 is rewound. The insulating material added to form the connecting portion insulating layer 21 is impregnated with the same insulating oil as the cable insulating oil (medium viscosity oil described above) before winding, and then wound. Further, between the insulating materials, there is an insulating oil used as a spilling oil when the connection portion insulating layer 21 is formed. In general, an insulating oil having a kinematic viscosity lower than that of the cable insulating oil is used as the sachet oil, but the same oil as the cable insulating oil may be used.

  As with the cable 1, the inner insulating layer 21 of the connecting portion has an inner semiconductive layer, the outer periphery has an outer semiconductive layer, and a main insulating layer is provided between the two semiconductive layers. In order to ensure electrical connection between the external semiconductive layer and the metal sheath 22, a cloth tape (not shown) woven with a copper wire is wound.

《High viscosity part》
The high-viscosity part provided between the connection part insulating layer 21 and a metal sheath 22 described later is composed of an insulating oil having a kinematic viscosity higher than that of the cable insulating oil. Specifically, the same insulating oil as the cable insulating oil (the above-mentioned medium viscosity polybutene oil) is used as a base oil, and an insulating oil containing polyisobutylene as a thickener in the base oil can be used. The content of the thickener may be appropriately adjusted so as to obtain a desired kinematic viscosity. In addition, an insulating oil having a kinematic viscosity higher than that of the cable insulating oil (having a kinematic viscosity at 60 ° C. higher than about 200 mm ² / s) may be used as a constituent material of the high viscosity portion.

《Metal sheath, anticorrosion layer》
A metal sheath 22 formed of a lead pipe is provided on the outer periphery of the connecting portion insulating layer 21, more specifically on the outer periphery of the layer made of the cloth tape provided on the outer periphery of the external semiconductive layer. Further, the outer periphery of the metal sheath 22 is provided with a corrosion prevention layer 23 made of polyethylene (PE). The anticorrosion layer 23 is formed by winding a PE tape around the outer periphery of the metal sheath 22 and then heating and melting the PE tape. In addition to the PE tape, the anticorrosion layer may be formed using a PE tube or the like.

  The above-mentioned high-viscosity part is obtained by, for example, cutting the intermediate connection structure so as to be orthogonal to the axial direction of the cable, and in this cross section, insulating oil that exists immediately below the metal sheath, or insulation impregnated in the cloth tape. It can be identified by extracting the oil and examining its molecular weight distribution.

<Assembly procedure for intermediate connection structure>
The intermediate connection structure 2 having the above configuration can be formed as follows.

  At each end of the cable core 1c of the pair of solid cables 1 to be connected, the respective constituent members are stripped to expose the conductor 10. The insulating material constituting the end portion side of the cable oil-immersed insulating layer 11 is stripped off or unwound so that the end portion side of the conductor 10 becomes generally thin. Then, the exposed conductor 10 is joined by welding, for example.

  After the inner semiconductive layer is formed on the outer periphery of the conductor connecting portion 20 connecting the conductors 10, the insulating material impregnated with the insulating oil is wound around the outer periphery, and the cable oil-insulated insulating layer 11 is wound around the outer periphery. The dissolved insulating material is rewound to form a main insulating layer. A suitable oil is applied during the winding of these insulating materials. An external semiconductive layer is formed on the outer periphery of the main insulating layer to form the connection insulating layer 21. A cloth tape woven with copper wire is wound around the outer periphery.

  A lead pipe is arranged on the outer periphery of the connection part insulating layer 21 (cloth tape), and both ends of the lead pipe are welded to the metal sheath 12 of the cable 1 to form the metal sheath 22. A hole (not shown) penetrating the front and back of the metal sheath 22 is provided, and an insulating oil (insulating oil containing a thickener) having a higher kinematic viscosity than the cable insulating oil described above is injected from the hole. To do. At this time, when the temperature of the insulating oil is raised, the injection work is easy to perform. After the injection, the hole is closed. A high-viscosity part is formed by this injection process. Next, a polyethylene (PE) tape is wound around the outer periphery of the metal sheath 22. The connection portion around which the PE tape is wound is heated to melt the PE to form the anticorrosion layer 23.

  As described above, in forming the anticorrosion layer in the intermediate connection structure (FJ), even if the connection portion is heated, the high viscosity portion exists between the metal sheath and the connection insulating layer in the FJ. In the intermediate connection structure, the insulating oil hardly moves. In addition, due to this heating, the components on the inner circumference side of the metal sheath in FJ, for example, the connecting portion insulating layer are warmed, and even if the insulating oil impregnated in the connecting portion insulating layer tries to move to the metal sheath side, the high The movement is regulated by the viscosity part. Therefore, it is possible to effectively prevent the insulating oil from leaking into the gap between the metal sheath and the connecting portion insulating layer in FJ. For example, if the amount of insulating oil impregnated in the connection insulating layer is 100% before heating when forming the FJ anticorrosive layer, the conventional example (insulating oil injected into the inner peripheral side of the metal sheath is the cable In the same example as the insulating oil), the amount of impregnated oil in the connecting portion insulating layer may be reduced after heating when the anticorrosion layer is formed. On the other hand, in this embodiment (an example having the high viscosity portion), it is expected that the amount of impregnated oil in the connecting portion insulating layer is the same level or slightly less than that before heating after the heating. Therefore, the intermediate connection structure having the high-viscosity portion is excellent in insulation characteristics, and a solid cable line having such an intermediate connection structure is expected to sufficiently satisfy desired insulation characteristics.

[Embodiment 2]
In the first embodiment, the configuration in which insulating oil is mainly used as the constituent material of the high viscosity portion has been described. In addition, the high-viscosity part can be composed of rubber or a resin-based organic solid material. Hereinafter, specific constituent materials and forming methods will be described. The configuration of the first embodiment described above and the configuration of the second embodiment may be combined, or an organic solid material may be used as a thickener.

  The form of the organic solid material may be, for example, a powder form, a fine grain form, a tape form, a braided material or the like, and these powders supported on a tape material, and is not particularly limited. In any form, a high-viscosity portion can be provided on the outer periphery of the connection insulating layer 21 by sprinkling or winding these materials on the outer semiconductive layer or copper wire woven cloth tape. it can. Alternatively, the fiber material may be used in place of a part or all of the cloth material of the copper wire woven cloth tape. In the second embodiment, the metal sheath 22 is formed after the high viscosity portion is formed. If it is difficult to connect the outer semiconductive layer and the metal sheath 22 with the copper wire woven cloth tape by configuring the high viscosity part with an organic solid material, a conductive filler such as carbon or metal is added to the organic solid material. It is preferable to add conductivity by adding it.

(Rubber material)
Examples of the rubber material include synthetic rubbers such as isoprene rubber, butadiene rubber, butyl rubber, ethylene propylene rubber, and polyisobutylene rubber. These synthetic rubbers swell (expand) when in contact with the insulating oil, and effectively suppress the movement of the insulating oil. Therefore, by arranging the rubber-based material close to the copper wire woven cloth tape itself or this cloth tape, the swollen rubber-based material compresses the gap of the copper wire woven cloth tape, or enters the gap, The movement of the insulating oil can be suppressed.

(Low melting point resin)
The high-viscosity part may be formed of a material whose melting point is lower than the heat-resistant temperature of the insulating material constituting the connection part insulating layer 21 and whose adhesiveness increases when heated above the melting point. For example, when the connection part insulating layer 21 is formed using the above PPLP (registered trademark), as a material having a melting point lower than the heat resistance temperature (about 140 ° C.) of PP (polypropylene) or heat resistance temperature, polyethylene (PE), Examples thereof include polymer materials such as polyethylene terephthalate (PET), polyvinyl alcohol (PVA), natural rubber (NR), synthetic rubber (isoprene rubber) (IR), styrene butadiene rubber (SBR), and urethane rubber (U).

(Low glass transition resin)
The glass transition point is lower than the heat resistance temperature of the insulating material constituting the connection insulating layer 21, and the high viscosity portion is formed of a thermoplastic synthetic resin that increases the adhesiveness when heated above this glass transition point. Also good. For example, when the connection insulating layer 21 is formed using the above PPLP (registered trademark), a resin having a glass transition point lower than the heat resistant temperature of PP (about 140 ° C.) is polyvinyl acetate (30 ° C.), nylon 6 (Registered trademark) (47 ° C), nylon 66 (registered trademark) (49 ° C), polyethylene terephthalate (80 ° C), polyvinyl chloride (82 ° C), polystyrene (100 ° C), and the like. In the above (), the glass transition point (temperature) is shown.

(Plasticizer-containing resin)
A high-viscosity part can also be formed of a polymer material that includes a plasticizer and that increases in temperature by raising the temperature so that the plasticizer oozes out and the adhesiveness increases. A thermoplastic synthetic resin or a synthetic rubber to which a plasticizer is added becomes sticky when the plasticizer exudes and the surface becomes sticky when heated. For example, since a phthalate ester is added as a plasticizer to a vinyl chloride resin (soft), when this resin is heated, the plasticizer exudes to the surface and becomes sticky. Therefore, a high-viscosity portion can be formed by forming a vinyl chloride resin containing a plasticizer into a tape shape or the like and winding this around the outer periphery of the connection portion insulating layer 21. In addition, polystyrene containing diethyl phthalate as a plasticizer and rubber containing dimethyl phthalate as a plasticizer can be used as a material containing a plasticizer.

  When using the above low melting point resin or low glass transition point resin, plasticizer-containing resin, after placing these resins in close proximity to the copper wire woven cloth tape itself or the cloth tape, the metal sheath 22, The anticorrosion layer 23 is formed. In forming the anticorrosion layer 23, the melting temperature of the polyethylene tape (however, the temperature not higher than the heat resistance temperature of the composite tape, the temperature not lower than the melting point of the resin, the temperature not lower than the glass transition point of the resin, or the plasticizer oozes out. By heating to (temperature), the resin constituting the high-viscosity part is also heated and the adhesiveness is increased, and this resin compresses the gap of the copper wire woven cloth tape or enters the gap, and the rubber-based material described above Similarly to the above, the movement of the insulating oil can be suppressed.

(Fluid material)
As a material other than the organic solid material, the high viscosity portion may be formed by a fluid such as a synthetic rubber latex adhesive. In this case, for example, a synthetic rubber-based latex adhesive may be directly applied to the outer periphery of the outer semiconductive layer or the copper wire woven cloth tape.

  The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, the composition and kinematic viscosity of the insulating oil used for the cable insulating oil and the intermediate connection structure, the constituent material of the cable oil immersion insulating layer and the connecting portion insulating layer, and the like can be appropriately changed.

  The intermediate connection structure of the solid cable of the present invention can be suitably used for a place where the solid cables are connected to each other in constructing a power supply, in particular, a long-distance large-capacity power supply line.

It is a cross-sectional schematic diagram which shows a part of intermediate connection structure of a solid cable.

Explanation of symbols

1 Solid cable 1c Cable core 2 Intermediate connection structure
10 Conductor 11 Cable oil immersion insulation layer 12,22 Metal sheath 13,23 Anticorrosion layer
14,24 Reinforcement layer 15,25 Exterior 20 Conductor connection 21 Connection insulation

Claims (5)

The ends of the pair of cable cores in which the conductor and the cable oil-insulating insulating layer covering the conductors are exposed stepwise, the conductor connecting portions that connect the exposed conductors, and the ends of the cable cores and the conductor connections A connecting portion insulating layer formed by winding a tape-like insulating material around the outer periphery of the portion, a metal sheath formed on the outer periphery of the connecting portion insulating layer, and a corrosion protection layer formed on the outer periphery of the metal sheath. An intermediate connection structure for a solid cable,
The connection part insulating layer is impregnated with insulating oil;
Between the metal sheath and the connection part insulating layer, a solid having a high viscosity part made of a material having a higher kinematic viscosity than the cable insulating oil impregnated in the cable oil immersion insulating layer is provided. Cable intermediate connection structure. ^2. The solid cable intermediate connection structure according to claim 1, wherein the cable insulating oil has a kinematic viscosity at 60 ° C. of 10 mm ² / s or more and less than 500 mm ² / s.   3. The solid cable intermediate connection structure according to claim 1, wherein the high viscosity portion includes an insulating oil having a kinematic viscosity higher than that of the cable insulating oil.   The high-viscosity part contains an insulating oil, and the insulating oil includes the same base oil as the cable insulating oil and a thickener. The intermediate connection structure of the solid cable as described in the section.   5. At least a part of the cable oil immersion insulating layer and at least a part of the connection part insulating layer are configured by winding a composite tape having insulating paper and a plastic layer. An intermediate connection structure for a solid cable according to any one of the above.

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