JP2001008356A - Insulated conductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductor for cryogenic temperatures, which uses an electrical insulating material which can ensure quick chilling operation down to the cryogenic temperature, and which can be extruded by finding the electrical insulating material. SOLUTION: This insulated conductor for a cryogenic temperature is provided with a conductor 10, which can be electrified at the cryogenic temperature and/or in a temperature region up to room temperature from the cryogenic temperature. The insulated conductor is provided with an electrical insulating layer 12 which covers the conductor part 10. The electrical insulating layer 12 is composed of an ionomer resin. In addition, as required, an internal semiconducting layer 11 can be insulated between the conductor 10 and the electrical insulating layer 12, and an outer semiconducting layer 13 and a shielding layer 14 can be installed at the outside of the electrical insulating layer 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cryogenic insulated conductor using an ionomer resin as an electric insulating material.
In particular, the present invention relates to a terminal for a superconducting device such as a superconducting coil, a terminal of a cryogenic cable, a terminal of a superconducting cable, a cryogenic insulating conductor used as a current lead and the like.

[0002]

2. Description of the Related Art A terminal for a superconducting device such as a superconducting coil, a cryogenic cable or a terminal portion (termination portion) of a superconducting cable draws a conductor under cryogenic temperature to room temperature, so that an environment having a very wide temperature range is required. Below. Such a terminal unit has a structure as shown in FIG. 7, for example. In the terminal portion, a conductor extraction rod 121 is used between the extremely low temperature cable main body 120 and the normal temperature range. The conductor extraction rod 121 is extracted from the cable main body 120 into the container 122 containing the refrigerant 123, and is further extracted at room temperature through the insulator tube 125 filled with the insulator 126. Refrigerant 1
In general, a liquid or a high-pressure gas is used for 23, and an insulating oil or SF ₆ is used for the insulator 126. In addition, since a portion of the insulator 126 near the refrigerant 123 may be solidified or liquefied to lower the insulation strength, the insulator 126 is circulated and heated externally using the device 129 to reduce the insulation characteristics. To prevent.

[0003] The insulation withstand voltage can be increased by providing a solid insulating coating and a shield layer having a ground potential on a conductor extraction rod connecting an extremely low temperature region and a normal temperature region. Ethylene propylene rubber (EPR) has been conventionally used as a material for the solid insulating coating.

In addition, EPR or glass fiber reinforced plastic (FRP) has been conventionally used for terminals for superconducting equipment such as superconducting coils, bushings for terminals of cryogenic cables, and insulators for current leads.

Further, superconducting cables having an extruded EPR insulating layer have been proposed.

[0006]

When an EPR is used in a cryogenic application, the EPR must be gradually cooled to a cryogenic temperature in order to prevent cracks from being generated or broken due to rapid cooling to the cryogenic temperature. For example, when using liquid nitrogen as a refrigerant, it is necessary to gradually cool the EPR insulating layer with a temperature-controlled low-temperature nitrogen gas and then contact the liquid nitrogen, instead of immediately bringing the EPR insulating layer into contact with liquid nitrogen. is there. Such temperature control and slow cooling require cumbersome operations.

When performing FRP insulation, generally, a base material is wound on a conductor, a resin is poured therein, and a pressure is applied to form an FRP insulation layer. Therefore, when applying an FRP insulating layer to a long conductor, the pressure vessel used in the above process becomes long, and large-scale equipment is required.

An object of the present invention is to provide a conductor for a cryogenic temperature using an electrically insulating material which can withstand rapid cooling to a cryogenic temperature and can be continuously manufactured with a small-scale facility.

[0009]

SUMMARY OF THE INVENTION The present invention provides an insulated conductor for cryogenic use, comprising: a conductor portion energized in a cryogenic temperature and / or a temperature range from cryogenic temperature to normal temperature; and an electrically insulating material covering the conductor portion. Wherein the electrically insulating material is mainly composed of an ionomer resin.

The insulated conductor for cryogenic use according to the present invention preferably includes at least one of an inner semiconductive layer provided between the conductor portion and the electrically insulating material and an outer semiconductive layer covering the electrically insulating material. At least one of the inner semiconductive layer and the outer semiconductive layer can contain an ionomer resin and a conductive material blended in the ionomer resin as main components.

The cryogenic insulating conductor according to the present invention may be selected from the group consisting of a terminal for a superconducting device such as a superconducting coil, a terminal of a cryogenic cable, a terminal of a superconducting cable, and a current lead. . The cryogenic insulated conductor according to the present invention may have a stress cone or a condenser cone made of the electrically insulating material.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that an ionomer resin (ionomer resin) is suitable as an electrically insulating material capable of withstanding quenching to extremely low temperatures and extrudable. The ionomer resin is a generic term for polymers having ionic cross-linking. Common ionomer resins are ethylene, α-olefins such as propylene,
It is obtained by crosslinking a carboxyl group (anion portion) of a copolymer composed of acrylic acid, methacrylic acid, or the like with a metal ion (cation portion) such as sodium, potassium, magnesium, or zinc. One obtained by crosslinking a copolymer of ethylene and methacrylic acid or acrylic acid with a metal ion such as zinc (Zn) or sodium (Na) is a preferred ionomer resin in the present invention.
As an ionomer resin, Himilan manufactured by Mitsui-Dupont Polychemical Co., Ltd., for example, Himilan 1554, 155
5, 1557, 1601, 1605, 1650, 165
2, 1702, 1705, 1706, 1707, 185
5, 1856 and the like.

The ionomer resin preferably used in the present invention has, for example, a specific gravity of 0.91 to 0.1.
97, the tensile strength is 20-35 MPa, the elongation at break is 300-600%, and the impact strength is 500-1.
200 kg · cm / cm ² , softening point 57-80
° C, the embrittlement temperature is -50 ° C or lower, and the dielectric strength (in the sheet) is 40 kV / mm or higher.

The electrical insulating material used in the present invention contains an ionomer resin as a main component. In addition to the ionomer resin, if necessary, coloring and coloring materials such as titanium oxide, carbon black and calcium silicate, and 4,4′-thiobis (3-methyl-6-t-butylphenol) (4,4′-t
An antioxidant such as hiobis (3-methyl-6-tert-butylphenol) or an antioxidant can be added according to a usual technique. Further, an electrically insulating material composed of a polymer blend obtained by mixing another polymer such as a polyethylene resin, an ethylene propylene rubber (EPR), or a fluororesin with an ionomer resin may be used in the present invention.

A semiconductive material can be obtained by adding a conductive material such as a carbon material such as carbon black to the ionomer resin or the above-described polymer blend. The content of carbon black in such a semiconductive material is, for example, 30 to 40% by weight. As described below, the semiconductive material is used to reduce the electric field on the surface of the conductor or to prevent partial discharge caused by the gap between the conductor and the insulator, between the conductor and the electrically insulating material, and / or It can be provided outside the electrically insulating material.

In the present invention, the electrically insulating material can be well coated on the conductor by extrusion. Also,
A tape-like electrically insulating material may be wound around a conductor to form an insulating layer. In general, extrusion is carried out via a crosshead in an extruder usually used for the production of insulated cables. The insulating material mainly composed of the kneaded ionomer resin is introduced into the space defined by the nipple supporting the conductor, the nipple holder and the crosshead by a screw, expanded into a tube shape, and formed into a predetermined diameter with a die. You. The conductor is fed from the rear in the extrusion direction, passes through the nipple, and is coated with an insulating material. The semiconductive material mainly composed of an ionomer resin and a conductive material such as carbon can be simultaneously coated with an electrically insulating material mainly composed of an ionomer resin by extrusion and can be coated on a conductor.

Hereinafter, specific examples of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 shows a terminal part (termination part) of a power cable such as a cryogenic cable or a superconducting cable according to the present invention. The terminal portion 2 connected to the cable main body 1 extends through the refrigerant liquid layer 4 to the refrigerant gas layer 5 in the heat insulating container 3. As the refrigerant, for example, liquid nitrogen is used. The terminal portion 2 further penetrates through the flange 6 and reaches the inside of the porcelain pipe 7, and is drawn out of the room temperature (room temperature) through the end insulating layer 9 that accommodates the insulator 8. For the insulator 8, SF ₆ , insulating oil, or the like is used. Therefore, the terminal portion is exposed to a refrigerant temperature such as liquid nitrogen temperature (about 77 K) which is an extremely low temperature, and has a temperature gradient from the refrigerant temperature such as liquid nitrogen temperature to normal temperature.

Such a terminal section 2 has a sectional structure as shown in FIG. In the terminal section 2, a conductor 10 made of a good electrical conductor (for example, copper) is arranged at the center.
The surface of the conductor 10 has an inner semiconductive layer 1 formed thereon.
Covered by 1. An electric insulating layer 12 is provided on the inner semiconductive layer 11. An external semiconductive layer 13 is provided on the electric insulating layer 12, and a shielding layer (shield layer) 1
4 are provided. The shielding layer 14 has a ground potential. The electrical insulating layer 12 contains the ionomer resin as described above as a main component. Inner semiconductive layer 11 and outer semiconductive layer 13
Is composed of, for example, an ionomer resin blended with carbon black. When each of the layers 11, 12 and 13 is mainly composed of an ionomer resin, these layers
For example, three layers can be provided on the conductor by extrusion at the same time. In the terminal portion 2, such a laminated structure is as follows:
For example, the region indicated by the arrow, that is, the refrigerant liquid phase 4
Is preferably provided at least from the vicinity of the liquid level to the middle of the end insulating layer 9. Further, in the terminal section 2, a structure having no coating can be provided from the middle to the upper end of the end insulating layer 9. Further, if necessary, it is preferable to provide a stress cone 15 at a connection portion between the cable main body 1 immersed in the refrigerant and the terminal portion provided with the electric insulating layer. It is preferable to provide the stress cone 16 at the boundary between the portion having no insulation and the portion having the insulating coating. Any of these stress cones,
Although it can be made of an electrically insulating material mainly composed of an ionomer resin, it is particularly preferable that the stress cone in contact with the refrigerant is made of an electrically insulating material mainly composed of an ionomer resin.

Instead of the covering structure shown in FIG. 2, FIG.
To (c) may be used. FIG.
In the structure shown in FIG. 2A, an inner semiconductive layer 11, an electric insulating layer 12, and a shielding layer 14 are provided around a conductor 10 in this order. In the structure shown in FIG. 3B, an electric insulating layer 12, an outer semiconductive layer 13, and a shielding layer 14 are provided around the conductor 10 in this order. In the structure shown in FIG. 3C, there is no semiconductive layer, and the electric insulating layer 12 is directly provided on the conductor.
The shielding layer 14 is provided on the outside.

A capacitor cone as shown in FIG. 4 may be provided instead of the stress cone as shown in FIG. In the structure shown in FIG. 4, a cable insulator 22 is provided around the conductor 20, and a reinforcing insulator 32 and a capacitor cone 17 made of a metal foil 33 buried therein are provided around the cable insulator 22. In the present invention, the cable insulator 22 and the reinforcing insulator 32 can be formed from an electrical insulating material whose main component is an ionomer resin.

FIGS. 5A and 5B show one specific example of the current lead. In the current lead 50,
Electrodes 44a and 44b made of copper or the like are provided at both ends of a conductor 40 made of a normal conductor such as copper, or a superconductor such as a metal superconductor, a metal compound superconductor, or an oxide superconductor. A portion between the two electrodes of the conductor 40 is covered with an electric insulating layer 42 containing an ionomer resin as a main component. Such a current lead is useful as a lead for supplying power to an extremely low temperature portion such as the temperature of liquid nitrogen.

[0023]

EXAMPLE An ionomer resin obtained by crosslinking an ethylene-methacrylic acid copolymer with Zn ions (Himilan 170)
6, 100 parts by weight of Mitsui DuPont Polychemicals), 1 part by weight of carbon black as a coloring material, and 0.5 parts by weight of 4,4′-thiobis (3-methyl-6-t-butylphenol) as an antioxidant. The mixture was kneaded by a roll, kneaded by a roll, formed into a film by a calendar roll, and cut by a cutter to obtain a tape. The obtained tape is used as SU
After winding around the conductor made of S304, heating and molding,
A coated conductor was obtained. The maximum thickness of the coating was 11 mm. FIG. 6 shows an outline of the structure of the obtained coated conductor. Around the conductor 80, an electric insulating layer 82 made of a compound having the above composition is provided.

The obtained coated conductor was converted to liquid nitrogen (about 77K).
And quenched immediately, but no cracks or cracks occurred in the insulating layer. The withstand voltage of the insulating layer (sheet sample)
It was 40 kV / mm or more.

[0025]

As described above, since the present invention uses an electrically insulating material that can withstand quenching to cryogenic temperatures, it enables easier temperature control in cryogenic cooling. For example, the slow cooling process can be further simplified, or the insulated conductor according to the present invention can be brought into contact with a refrigerant such as liquid nitrogen without passing through the slow cooling process. In addition, since the electrical insulating material containing an ionomer resin as a main component can be extruded, the present invention can be easily manufactured and can be applied to various uses including long uses. An electrical insulating material mainly composed of an ionomer resin is also useful for forming a condenser cone and a stress cone for an electric field control function. Furthermore, if an ionomer resin is used for the semiconductive layer, the semiconductive layer together with the insulating layer can be formed by extrusion at the same time, and the manufacturing cost can be reduced.

The present invention is particularly useful for the terminal or connection structure provided between normal temperature and cryogenic temperature as described above, and is also applicable to a conductor exposed to cryogenic temperature, such as a cryogenic cable and a superconducting cable main body. can do. An electrically insulating material mainly composed of an ionomer resin can constitute an insulating layer of a cable or the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a specific example of a cable terminal according to the present invention.

FIG. 2 is a schematic sectional view of the terminal shown in FIG.

3 (a) to 3 (c) are schematic sectional views showing other specific examples of the terminal according to the present invention.

FIG. 4 is a schematic sectional view showing a specific example of a condenser cone.

FIGS. 5A and 5B are a cross-sectional view and a cross-sectional view illustrating a specific example of a current lead according to the present invention.

FIG. 6 is a schematic sectional view showing a coated conductor of an example.

FIG. 7 is a schematic diagram showing a terminal structure of a power cable.

[Explanation of symbols]

 10, 20, 40, 60, 80 Conductor 11 Internal semiconductive layer 12, 42, 62, 82 Electrical insulating layer 13 External semiconductive layer 14 Shielding layer

Claims (5)

[Claims] 1. An insulated conductor for a cryogenic temperature, comprising: a conductor portion energized in a temperature range from a cryogenic temperature and / or a cryogenic temperature to a normal temperature; and an electrically insulating material covering the conductor portion. An insulated conductor for cryogenic use, characterized in that the material is mainly composed of an ionomer resin. 2. The semiconductor device according to claim 1, further comprising at least one of an inner semiconductive layer provided between said conductor portion and said electrically insulating material and an outer semiconductive layer covering said electrically insulating material. The insulated conductor for cryogenic use according to the above. 3. The semiconductor device according to claim 1, wherein at least one of the inner semiconductive layer and the outer semiconductive layer contains an ionomer resin and a conductive material blended in the ionomer resin as main components. 3. The cryogenic insulated conductor according to 2. 4. A terminal for a superconducting device such as a terminal of a cryogenic cable, a superconducting coil, etc.,
The cryogenic insulated conductor according to any one of claims 1 to 3, wherein the conductor is selected from the group consisting of a current lead and a terminal of a superconducting cable. 5. The cryogenic insulating conductor is a terminal for a superconducting device such as a superconducting coil, a current lead, a terminal of a cryogenic cable or a terminal of a superconducting cable, and a stress cone or a stress cone made of the electric insulating material. The cryogenic insulated conductor according to any one of claims 1 to 3, further comprising a condenser cone.