JPH07254312A - Insulation structure for cryogenic cable - Google Patents

Abstract

PURPOSE:To easily release insulation material generated gas to the outside of an insulation layer, and increase the degree of vacuum inside and outside the layer by alternately stacking the insulation material layer of semisynthetic paper or a polymeric film, and the insulating paper layer of only cellulose. CONSTITUTION:Carbon paper 2a is wound around the surface of a brass electrode rod 1 via a 1mm gap 3a, thereby forming the first layer. Then, as the second layer, carbon paper 2b of the same size is wound thereon in half- wrapping state so as to have a gap 3a positioned at a center and form a 1mm gap 3b. in addition, semisynthetic paper, kapton or kraft paper as the first insulation layer 4a is wound thereon via 1mm gap 3'a for the second layer carbon paper 2b. Subsequently, the second insulation layer 4b is wound around the insulation layer 4a in 1/3-wrapping state via 1mm gap 3'b. Similarly, layers up to the seventh layer 4g are subsequently formed. According to this construction, gas trapped inside the insulation layer and insulation material generated gas can be discharged outside via the gaps and the kraft paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission cable as a cryogenic cable which uses liquefied gas such as liquid nitrogen, liquid hydrogen, liquefied natural gas and liquid helium as a refrigerant, and a temperature of liquid helium or liquid nitrogen. The present invention relates to an insulation structure for cables and bus lines used at extremely low temperatures such as superconducting cables used in.

[0002]

2. Description of the Related Art Conventionally, in the insulation structure of these cryogenic cables, a single kind of semi-synthetic paper or polymer film insulating material is wrapped around a conductor, and this is formed into a plurality of layers to form an insulating layer. The portion of the insulating layer was further evacuated and configured. Specific examples of the semi-synthetic paper include biaxially oriented polypropylene laminated paper (OPPL) and other polypropylene laminated paper, and a polyimide resin is used as the polymer film. For example, Kapton (Toray, DuPont), Apical (Kanebuchi Chemical), Upilex (Ube Industries), Nopax (Mitsubishi Kasei) and others.

[0003]

In such a conventional insulating structure, the adsorbed gas such as H ₂ O, O ₂ , H ₂ , N ₂ generated from the insulating material when the insulating layer is evacuated is permeable to gas. Since it is not smoothly exhausted by being blocked by the polymer film that is inferior in properties or the polymer film in semi-synthetic paper, it is not possible to smoothly exhaust between each insulating material, and in the gap (ButtGap) described below that is formed when winding a tape-shaped insulating material The degree of vacuum inside the material and even outside the insulating layer did not rise.

The main cause of the dielectric breakdown in the high-vacuum insulating material laminated insulating method having such a structure is not the penetration breakdown that directly penetrates through the insulating material but the surface flashing through the gap between the insulating materials. However, since the degree of vacuum does not rise as described above, such a dielectric breakdown is apt to occur and the withstand voltage characteristic is deteriorated.

[0005]

DISCLOSURE OF THE INVENTION As a result of studies in view of this, the present invention has developed an insulating structure for a cryogenic cable which can easily improve the degree of vacuum in an insulating material or between these materials. , In the insulation structure of a cable for cryogenic use, in which the conductor is covered with an insulating layer and the surroundings are evacuated, the insulating material layer of semi-synthetic paper or polymer film and the insulating paper layer consisting of cellulose are laminated alternately. It is characterized by having done. The above-mentioned insulating paper made of only cellulose refers to kraft paper generally used for power OF cables and the like (including those not subjected to deionization treatment and hanging).

[0006]

As described above, according to the present invention, for example, one or more insulating materials are laminated on a conductor including an internal semiconductive layer without laminating only insulating materials such as semi-synthetic paper and polymer film, On top of that, one or more sheets of insulating paper such as kraft paper (not including polymer film, only cellulose) are laminated, and further one or more sheets of insulating material such as semi-synthetic paper and polymer film are laminated. . That is, the insulating layer is formed by repeating a structure in which one or more insulating papers such as kraft paper are laminated and a structure in which one or more insulating materials such as semi-synthetic paper and polymer film are laminated. The presence or absence of the internal semiconductive layer does not matter, and the material which is first coated on the conductor with or without the internal semiconductive layer may be insulating paper having excellent gas permeability such as kraft paper.

[0007] As described above, a structure in which only insulating materials such as semi-synthetic paper and polymer film having poor gas permeability are laminated is used.
By sandwiching kraft paper with excellent gas permeability between polymer films, the gas generated from the insulating material can be easily released to the outside of the insulating layer through the laminated insulating paper and the gap (Butt Gap) of the insulating material of each layer. Therefore, the degree of vacuum inside and outside the insulating layer can be easily increased, and the time required to reach a high vacuum can be shortened.

[0008]

EXAMPLES Next, it will be described with reference to examples that the present invention is effective in improving the degree of vacuum and thereby improving withstand voltage characteristics.

As shown in FIGS. 1 and 2, a brass electrode rod (1) as a conductor has a thickness of 1 as an inner semiconductive layer around the electrode rod (1).
A tape-like carbon paper (2a) having a width of 30 μm and a width of 20 mm was wound while providing a gap (Butt Gap) (3a) of 1 mm, and a carbon paper (2b) of the same size was further wound on the tape with a half wrap. Each of them has a thickness of 120 μm and a width of 20
mm tape-shaped semi-synthetic paper, polymer film or Kapton, and 20 mm wide tape-shaped kraft paper with the structure shown in Table 1 and a gap of 1 mm each (Butt Gap)
And was wound alternately with 1/3 wrap and laminated in 7 layers to form an insulating layer (4). Then, a carbon paper (5) for electric field relaxation and partial discharge prevention is wound on a part of the insulating layer (4), an aluminum foil (6) for grounding is ground, and a copper wire (7) is further placed on the aluminum foil (6). ) Was wound to make a cryogenic cable.
The tip of the electrode is covered with fiber reinforced plastic (8),
(9) is a stress relief cone made of kraft paper (deionized, shackled) for electric field relaxation.

This configuration will be further described with reference to FIG. FIG. 2 is an axial cross section of the insulating layer of FIG. 1st layer of 20mm wide carbon paper (2a) on the surface of brass electrode rod (1)
It is wound to form a mm gap (Butt Gap) (3a). Next, as the second layer, a carbon paper (2b) having the same size is wound so that the position of the gap (3a) is aligned with the center of the tape (half wrap) to form a gap (3b) of 1 mm. And on top of this is an insulating material as shown in Table 1.
20mm width semi-synthetic paper, polymer film or Kapton,
Alternatively, a kraft paper is wound as a first insulating layer (4a) with a 1 mm gap (3'a) provided by half-wrapping with respect to the second carbon paper (2b), followed by a second insulating layer ( 4b) was wound on the first insulating layer (4a) with a 1/3 wrap with a 1 mm gap (3'b), and thereafter, according to Table 1, up to the seventh insulating layer (4g) was provided. .

[0011]

[Table 1] ・ In the table, A is OPPL (biaxially oriented polypropylene laminated paper) B is Kapton C is TYVEK (nonwoven fabric) × is kraft paper

Table 2 shows the test results obtained by measuring the DC breakdown voltage and the exhaust time until the degree of vacuum outside the insulating layer reaches 10 ^-3 torr for these cryogenic cables. In addition,
The test equipment is a copper block with excellent thermal conductivity embedded in the bottom of the refrigerant tank filled with the refrigerant, the indirect cooling by connecting the cryogenic cable placed outside the refrigerant tank to this copper block, at the same time the cable The surroundings are configured to be evacuated, and the DC breakdown voltage is indirectly cooled with liquid N ₂ using these cables as a refrigerant, and after the temperature of these cables reaches almost the liquid N ₂ temperature, the voltage is increased by 1 kV for 5 minutes. . Also, the vacuum pump evacuates with a pump of 345 L / sec,
The degree of vacuum in the test apparatus when liquid N _{2 was} cooled was constant at 2 × 10 ^-6 torr.

[0013]

[Table 2]

It can be seen from Table 2 that the cryogenic cable of the present invention reaches a predetermined degree of vacuum in a shorter time than that of the conventional example and has a good insulating property. This is because the conventional insulating layers were all semi-synthetic paper containing polymer film, polymer film, Kapton, etc., so gas inside the insulating layer does not easily escape to the outside, improving the degree of vacuum inside the insulating layer and the outside of the insulating layer. Although it was not possible to increase the vacuum evacuation speed of the above, in the present invention, since the polymer film portion having poor gas permeability is not continuously laminated, gas and semi-synthetic paper trapped inside the insulating layer, etc. Gas generated from the insulating material of the gap (Butt
Gap) and kraft paper with excellent gas permeability can now be exhausted to the outside of the insulating layer.

[0015]

As described above, according to the present invention, since a predetermined vacuum degree is reached in a short time, a cryogenic cable having good workability and low cost can be obtained, and further, a cryogenic cable such as a superconducting cable can be obtained. It has a remarkable effect that it is very effective as a high vacuum insulating means.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a cryogenic cable used in an example of the present invention.

FIG. 2 is an explanatory diagram showing details of an insulating layer of the cable of FIG.

[Explanation of symbols]

 1 Electrode Rod 2 Carbon Paper 3 Gap (Butt Gap) 4 Insulating Layer 5 Carbon Paper 6 Aluminum Foil 7 Copper Wire 8 Textile Machine Reinforced Plastic 9 Stress Relief Cone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Tanaka 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Osamu Fujii 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Hirokazu Misawa Ichiban, Higashishin-cho, Higashi-ku, Nagoya, Aichi Prefecture Chubu Electric Power Co., Inc.

Claims (1)

[Claims] 1. An insulating structure of a cable for cryogenic use, which comprises covering an electric conductor with an insulating layer and evacuating the surroundings, and an insulating material layer of semi-synthetic paper or polymer film, and an insulating paper layer made of only cellulose. Cryogenic cable insulation structure characterized by alternating layers.