JPH0432108A - superconducting cable - Google Patents

Abstract

PURPOSE:To enable to maintain stably such superior insulating performance that no crack occurs by cooling, even if the electric insulating layer is formed of existing insulating materials by providing a heat insulating layer inside an electric insulating layer and keeping the electric insulating layer at the room temperature. CONSTITUTION:A passage 1, in which liquid nitrogen flows, is provided inside a pipe 2 made of an good heat transfer material such as copper or the like. And on its outside a current conductor 3 using a high temperature superconductor, a heat insulating layer 4, a pipe 5 having low conductivity and low thermal conductivity, an electric insulating layer 6 and a sheath 7 are successively provided. In this way the electric insulating layer 6 is arranged outside the heat insulating layer 4, and an existing insulating material is quite enough. And as the electric insulating layer 6 is apart sufficiently from the current conductor, a thin thickness of the layer does well and as the result the size of the cable can be made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superconducting cable for power transmission.

[Conventional technology]

An example of a design example of a power cable using a high-temperature superconductor exhibiting a superconducting phenomenon at liquid nitrogen temperature is shown in FIG. 5, for example. In the figure, 20 is a refrigerant outward path, 21 is a superconducting conductor, 23 is an electrical insulation material, 24 is a refrigerant return path, 25 is a pipe, 26 is a composite insulation layer that combines multilayer vacuum insulation and superinsulation, and 27 is a protective material. be.

In addition, the 63rd National Conference of the Institute of Electrical Engineers of Japan 1303,
04 (88 Osaka International Symbo P337-342), 1st Year National Conference of the Institute of Electrical Engineers of Japan 845 (846), 14th National Conference
There is a design example shown in 50, but these cables also
The electrical insulation layer is placed inside the thermal insulation layer, similar to the cable of FIG.

[Problem to be solved by the invention]

As mentioned above, in conventional cables of this type, the electrical insulation layer is located inside the thermal insulation layer, so cranks and the like are likely to enter the electrical insulation material when the conductor is cooled, and there is concern that the performance of the electrical insulation will deteriorate.

Note that since a material with excellent electrical insulation performance and sufficient resistance to liquid nitrogen temperatures has not yet been developed, it is impossible to solve the above-mentioned problems from the viewpoint of the materials used.

Therefore, the present invention provides a cable structure that maintains excellent electrical insulation performance even when existing electrical insulation materials are used.

[Means to solve the problem]

In the second invention, above! I! In order to solve the problem S, a thermal insulating layer is provided inside the electrical insulating layer to insulate a current conductor made of a high-temperature superconductor and a coolant flow path attached to this conductor from the outside.

[Function] When the thermal insulating layer is provided inside the electrically insulating layer, the outer electrically insulating layer is kept at room temperature. Therefore, insulating materials such as cross-linked polyethylene used in existing cables can be used, and even with such insulating materials, the electrical insulation performance does not deteriorate due to cranks or the like.

〔Example〕

FIG. 1 shows a first embodiment of the present invention, in which 1 is a flow path for passing liquid nitrogen, 2 is a pipe made of a material with good heat conductivity such as copper, 3 is a current conductor using a high-temperature superconductor, and 4 is a current conductor made of a high-temperature superconductor. is a thermal insulation layer,
5 is a pipe with low electrical conductivity and thermal conductivity, 6 is an electrical insulating layer, and 7 is a sheath.

In this way, the electrically insulating layer 6 is outside the thermally insulating layer 4, so that existing insulating materials are sufficient.

Furthermore, since the electrical insulating layer 6 is sufficiently far away from the current conductor, the layer thickness can be reduced, leading to a compact cable size.

FIG. 2 shows a second embodiment of the invention. The current conductor 3 is
Since it is indirectly cooled via the pipe 2, it is placed on the pipe 2 with solder, good thermal conductive grease, etc. to make very good thermal contact with the pipe 2. In addition, pipes with good heat conductivity, such as copper pipes, are used. Here, if a highly conductive material such as copper is used for the pipe 2, there is a concern about loss due to eddy currents generated in this pipe, but this problem can be solved by winding the current conductor 3 in a double helical winding, as shown in Figure 3. This can be solved by canceling out the eddy currents caused by the lower layer conductor and the eddy currents caused by the upper layer conductor.

The pipe 5 is preferably made of a material with poor thermal conductivity, such as stainless steel. If vacuum insulation is not incorporated into the thermal insulation layer 4,
FRPhJ (7) resin pipe will also suffice.

In the figure, a corrugated pipe is used for 5 to give flexibility to the cable.

The heat insulating layer 4 may be of a vacuum insulation type using pearlite foam or the like, or of a multilayer insulation type using super insulation or the like. The latter is advantageous in terms of making the cable size more compact.

The area outside pipe 5 is at room temperature, so -IIG
The same structure as the Cv cable can be adopted. 6 is an electrically insulating layer made of crosslinked polyethylene or the like, 7 is a sheath, 8 is an inner semiconducting layer, 9 is an outer semiconducting layer, and 10 is a wire shield.

FIG. 4 shows yet another embodiment. As shown in the figure, a pipe 11 is provided between the current conductor 3 and the thermal insulation layer 4.
A flow path 12 for liquid nitrogen is created between the two. pipe 1
1 should be similar to 5.

In this structure, since the current conductor 3 can be directly cooled with liquid nitrogen, the stability is higher than that of the first and second embodiments described above, and the current capacity can be increased.

However, the cable size will be slightly larger. This structure allows liquid nitrogen to be circulated in a closed cycle with the flow path 1 as the forward path and the flow path 12 as the return path. Further, it is also possible to make a hole in the pipe 2 and make the wave paths 1 and 12 communicate with each other at each part in the longitudinal direction of the cable.

〔effect〕

As explained above, in this invention, the thermal insulating layer is provided inside the electrical insulating layer to keep the electrical insulating layer at room temperature. This prevents this from occurring, making it possible to stably maintain excellent insulation performance.

Furthermore, since the electrical insulation layer can be made thinner, the cable size can also be made more compact.

[Brief explanation of drawings]

FIG. 1 is a sectional view of one embodiment of the invention, FIG. 2 is a perspective view of another embodiment, FIG. 3 is a side view showing a double helical winding current conductor, and FIG. 4 is a further view of the cable. FIG. 5 is a sectional view showing another example of a conventional cable design. 1.12...Flow path, 2...Pipe, 3...Current conductor, 4...Thermal insulation layer, 5.11...・Pipe, 6...
Electrical insulation layer, 7... sheath, 8...
...Inner semiconducting layer, 9...Outer semiconducting layer, 10...Wire shield. Figure 1 Figure 2 Figure 4 Figure 3 Figure 5

Claims (1)

[Claims] (1) In a superconducting cable in which a high-temperature superconductor that becomes superconducting at liquid nitrogen temperature is used as a current conductor, and this current conductor is attached to a coolant flow path, the thermal insulation layer surrounding the current conductor and the coolant flow path is an electrical insulation layer. A superconducting cable characterized by being installed inside the.