JP4028454B2 - Cryogenic cable termination connection - Google Patents

Description

  The present invention relates to a terminal connection portion of a cryogenic cable (including a superconducting cable, a cryogenic resistance cable, etc.) cooled by a cryogenic liquid such as liquid nitrogen.

A terminal connection portion of a cryogenic cable, for example, a superconducting cable, includes a lead conductor having one end connected directly to the conductor of the superconducting cable or indirectly through another connecting member and the other end drawn into the atmosphere. .
This lead conductor is generally made of a copper conductor, one end is cooled with liquid nitrogen or the like, and the other end is drawn into the atmosphere, so the temperature of liquid nitrogen, that is, a very high temperature from extremely low temperature to room temperature. It has a slope (temperature gradient).

A termination connection part of a general cryogenic cable will be described with reference to FIG.
FIG. 3 is a longitudinal sectional view showing an example of a terminal connection portion of a conventional general cryogenic cable. As shown in FIG. 3, a conductor 1 such as a superconducting cable is connected to a lead conductor 3 through a connection portion 2. The lead conductor 3 passes through a temperature gradient portion 12 constituted by a liquid refrigerant layer 4 such as liquid nitrogen and a refrigerant gas layer 5 made of nitrogen gas or the like connected to the upper portion of the liquid refrigerant layer 4, and further this temperature gradient portion. After passing through the high voltage lead-out part 13 partitioned by 12 and the flange 6, it is led to the outside.
The high voltage lead-out portion 13 is mainly composed of an insulator 7 and a fluid insulator 8 made of insulating oil, SF ₆ gas, or the like filled in the insulator 7.

  Here, reference numeral 9 denotes a high-pressure insulated container. By the way, the lead conductor 3 extends over a portion located in the temperature inclined portion 12 and a portion located in the lower portion of the high voltage lead portion 13, and an insulating covering portion 3a provided with an insulating covering made of, for example, ethylene propylene rubber, It comprises a conductor exposed portion 3b that extends above the insulating coating portion 3a, passes through the high voltage lead-out portion 13, and is not provided with an insulating coating that is led out to the outside, that is, a bare copper conductor. Reference numeral 10 denotes an electric field control member, that is, a stress cone provided near both ends of the insulating coating portion 3a.

Since the termination connection part of such a cryogenic cable is exposed to a very large temperature gradient (temperature gradient) from cryogenic temperature to room temperature, it has various thermal problems.
For example, the liquid refrigerant is vaporized by the intrusion heat from the outside or the Joule heat of the lead conductor 3 at the lower end portion of the insulating coating portion 3 a located in the liquid refrigerant layer 4 or the lower end portion of the stress cone 10, and the evaporated gas is There is a problem that it accumulates and lowers the insulation strength (Patent Document 1).
Furthermore, there is a problem that the fluid insulator 8 in the insulator 7 is deprived of heat to the refrigerant gas layer 5 or the liquid refrigerant layer 4 side through the lead conductor 3 and solidifies or liquefies to lower the insulation strength. Patent Document 2).

  Among these problems, the former has been proposed (Patent Document 1) in which the liquid refrigerant layer 4 is pressurized with a gas having a boiling point lower than that of the liquid refrigerant, and the lead conductor 3 on the fluid insulator 8 side is also proposed for the latter problem. Has been proposed (Patent Document 2) such that the outer diameter of the refrigerant is larger than the outer diameter on the refrigerant gas layer 5 or liquid refrigerant layer 4 side.

Patent Document 1: Japanese Patent Application Laid-Open No. 10-70828 Patent Document 2: Japanese Patent Application Laid-Open No. 8-196032

Incidentally, in the terminal connection portion of the conventional cryogenic cable shown in FIG. 3, as described above, the liquid refrigerant enters the insulating coating portion 3a located in the liquid refrigerant layer 4 or the lower end portion of the stress cone 10 and intrudes heat or draws out. The problem is that vaporization is caused by Joule heat of the conductor 3 and the evaporated gas accumulates, resulting in a decrease in insulation strength, and the heat of the fluid insulator is taken away by the refrigerant gas layer 5 or the liquid refrigerant layer 4 side, resulting in an insulation strength. In addition to the problem of deterioration, there were the following problems.
That is, the insulating coating made of, for example, ethylene propylene rubber, of the insulating coating portion 3a of the lead conductor 3 is reduced in mechanical strength at the temperature of liquid nitrogen to cause cracking, and the insulating strength is deteriorated.

  Therefore, various materials other than ethylene propylene rubber were examined as the material for the insulating coating. Specifically, for example, it was replaced with an epoxy resin, but because the linear expansion coefficient of the epoxy resin is larger than the linear expansion coefficient of the copper conductor, excessive stress is generated in the epoxy resin during cooling, Insulation coating sometimes cracked.

  Accordingly, an object of the present invention is to propose a structure of a lead conductor that does not cause cracking even when the insulation coating covering a part of the lead conductor (insulation coating portion 3a in FIG. 3) is cooled by liquid refrigerant or refrigerant gas. Accordingly, an object of the present invention is to provide a highly reliable termination connection for a cryogenic cable.

In order to achieve the above object, the present invention according to claim 1 is directed to an end of a cryogenic cable having a lead conductor drawn from a cryogenic temperature to a normal temperature through a liquid refrigerant layer, a refrigerant gas layer and a high voltage lead portion in a temperature gradient portion. In the connecting portion, the lead conductor is provided with an insulating coating having an electric field control member at both ends across a portion located in the temperature inclined portion and a portion located in the lower portion of the high voltage lead portion, and at least the A mold release process is performed between the lead conductor and the insulating coating in the portion located in the temperature inclined portion, and the outer diameter of the portion of the lead conductor located in the high voltage lead portion is located in the temperature inclined portion. The outer diameter of the portion which is larger than the outer diameter of the portion and which is located in the temperature inclined portion is tapered toward the upper portion .

According to the terminal connection portion of the cryogenic cable of the present invention as described in claim 1, the insulating coating portion of the lead conductor is cooled by the liquid refrigerant layer or the refrigerant gas layer, and the resin constituting the insulating coating is copper. Even if the shrinkage amount and shrinkage speed are different due to the difference in linear expansion coefficient between them, at least the portion between the lead conductor and the insulation coating in the temperature inclined portion is contracted. Since the mold release treatment is performed between them, it is assumed that both contract while sliding on the interface with each other, and are less likely to receive the stress accompanying the contraction.
Further, the outer diameter of the portion of the lead conductor located in the high voltage lead portion is larger than the outer diameter of the portion located in the temperature inclined portion, and the outer diameter of the portion located in the temperature inclined portion is the upper portion The insulation coating portion of the lead conductor is cooled by the liquid refrigerant layer or the refrigerant gas layer, and the amount of contraction between the resin and the copper conductor constituting the insulation coating due to the difference in linear expansion coefficient at that time Even if the shrinkage speed is different, in addition to the fact that a release treatment is performed between the lead conductor and the insulation coating at least in the portion located in the temperature gradient portion as described above, the copper conductor is in the state described above. Since the outer diameter of the portion located in the temperature inclined portion is tapered toward the upper portion, the shrinking resin becomes easier to slide on the lead conductor, and an excessive stress is hardly generated.
As described above, it is difficult for excessive stress to be applied to the resin side, the resin insulation coating is difficult to break, and a highly reliable terminal connection portion of the cryogenic cable can be provided.

Furthermore, the present invention according to claim 2 is characterized in that, in the invention according to claim 1 , the insulating coating is made of an epoxy resin.
According to the second aspect of the present invention as described above, since the epoxy resin is used as the resin for the insulating coating, it becomes more difficult to break even under cooling.
Therefore, it is possible to provide a highly reliable terminal connection portion for a cryogenic cable.

  As described above, according to the terminal connection portion of the cryogenic cable of the present invention, it is difficult for excessive stress to be applied to the insulation coating in the insulation coating portion of the lead conductor, and the resin insulation coating is difficult to break. Therefore, it is possible to provide a highly reliable terminal connection portion for a cryogenic cable.

  An embodiment of the termination connecting portion of the cryogenic cable according to the present invention will be described in detail with reference to FIGS.

FIG. 1 is a longitudinal sectional view of an essential part of a terminal connection part of a cryogenic cable according to the present invention. In FIG. 1, reference numeral 3 denotes a lead conductor which is an object of the present invention. The lower end of the lead conductor 3 is connected to the interface conductor 11 by a connection terminal 20 such as a flexible connector.
The interface conductor 11 is a conductor that is directly connected to the conductor of the superconducting cable, or a conductor that is indirectly connected to the conductor of the superconducting cable via a multi-contact or various connection sleeves.

  As described above, the lead conductor 3 whose lower end is connected to the conductor 11 has a liquid refrigerant layer 4 such as liquid nitrogen in the temperature gradient portion 12, a refrigerant gas layer 5 made of nitrogen gas and the like, and a temperature gradient. Through the high voltage lead-out part 13 connected above the part 12, the tip of the high-voltage lead-out part 13, that is, the state at room temperature is drawn out.

Incidentally, the temperature gradient portion 12 is covered with a SUS external pressure vessel 21 that mainly forms a vacuum heat insulating layer as shown in FIG. 1, and also the SUS internal pressure vessel 22, and the internal pressure vessel 22. The liquid refrigerant layer 4 and the refrigerant gas layer 5 are formed inside. The high voltage lead-out portion 13 partitioned by the temperature gradient portion 12 and the flange 6 is mainly composed of an insulator 7, a fluid insulator 8 made of insulating oil, SF ₆ gas, or the like filled in the insulator 7 and a high voltage. It is constituted by an upper metal fitting 14 provided at the leading end of the drawing portion 13. Reference numeral 23 denotes a pressure partition that partitions the temperature inclined portion 12 and the interface side (not shown).

Now, the lead conductor 3 of the present invention arranged in the terminal connection part of the cryogenic cable as described above straddles the part located in the temperature inclined part 12 and the part located in the lower part of the high voltage lead part 13, As shown in FIG. 1 and FIG. 2 at both ends, an insulating coating made of epoxy resin having a bell mouth structure 3g is applied as an electric field control member. The electric field control member is not limited to the bell mouth structure 3g, and various commonly used stress cones can be used.
The portion thus provided with the insulating coating is referred to as an insulating coating portion 3a. Above the insulating coating portion 3a, a conductor exposed portion 3b having a conductor outer diameter of about D, which is not covered with an insulating coating via a connecting portion if necessary, that is, made of a bare copper conductor, is connected. It is led to the upper metal fitting 14.

As shown in FIG. 1, the copper conductor of the lead conductor 3 is such that the outer diameter of the portion 3e located in the high voltage lead portion 13 is relatively larger than that of the portion 3f located in the temperature inclined portion 12. The fluid insulator 8 in the insulator 7 is designed to be difficult to be deprived of heat toward the refrigerant gas layer 5 or the liquid refrigerant layer 4 through the lead conductor 3. That is, the fluid insulator 8 is prevented from being solidified or liquefied to lower the insulation strength.
As described above, the lead conductor 3 is composed of the insulating coating portion 3a and the conductor exposed portion 3b.

The feature of the present invention resides in the insulating coating portion 3a of the lead conductor 3. Therefore, the present invention will be described in detail with reference to FIG. 2 which is an enlarged partial sectional view of the insulating coating portion 3a.
First, the shape of the lead conductor 3 will be described. In FIG. 2, the right side toward the paper surface shows the lower end portion of the lead conductor 3 in FIG. 1, and the left side of the paper surface shows the upper end portion rising to the high voltage extraction portion 13.
2, the outer diameter D of the portion of the conductor 3 e located in the high voltage lead-out portion 13 is located in the temperature gradient portion 12 on the right side of FIG. 2 and corresponds to the lower end side of the lead-out conductor 3. The lowermost outer diameter d of the conductor 3f is larger. Further, the outer diameter of the conductor 3f located in the temperature inclined portion 12 is narrowed toward the upper portion by a taper angle θ, and after reaching the minimum outer diameter at the lower end near the flange 6 in FIG. On the contrary, the diameter is increased, and the conductor outer diameter D is designed in the vicinity of the flange 6.

  On the other hand, as shown in FIG. 2, bellows structures 3g and 3g for electric field control are provided in the vicinity of both ends of the insulating coating portion 3a. Further, a flange portion 3k is provided at the center, and this is for positioning and fixing the lead conductor 3 by bringing the upper surface of the flange portion 3k into contact with the lower end of the flange 6 in FIG. If the lead conductor 3 can be positioned by another method, it is not necessary to provide the flange portion 3k.

  In the portion of the lead conductor 3 where the conductor is tapered (on the side of the conductor 3f), a release treatment is performed between the insulating coating and the lead conductor 3f.

After the insulating coating portion 3a thus formed was connected to the conductor exposed portion 3b, it was set in the terminal connection portion shown in FIG. When the upper metal fitting 14 of the high voltage lead-out portion 13 is attached, the inside of the insulator 7, the inside of the external pressure vessel 21 and the inside of the internal pressure vessel 22 are evacuated, and then the insulating oil is injected into the insulator 7 to obtain a fluid insulator. 8 and the internal pressure vessel 22 is first filled with liquid nitrogen from a liquid refrigerant inlet (not shown) to a level where only the portion 3n where the conductor at the lower end of the insulating coating portion 3a is exposed is immersed in the liquid refrigerant layer 4. Injected.
This state was maintained for about 10 minutes, and the lead conductor 3 side was cooled before the insulating coating (resin) to start thermal contraction. Thereafter, liquid nitrogen was injected to the level shown in FIG.

  A partial discharge test was attempted on the terminal connection portion of the cryogenic cable thus assembled. As a result, it was confirmed that the noise level was 2 pc and no partial discharge occurred even when 95 kV, which is a partial discharge test voltage for a 77 kV transmission cable, was loaded. Further, after the end of the test, this terminal connection part was disassembled and the lead conductor 3 was pulled up and observed, but no cracks or cracks were found in the insulation coating of the insulation coating portion 3a.

The reason why the insulating coating made of epoxy resin was not cracked in this way is assumed as follows.
That is, when the insulating coating portion 3a is cooled by the liquid refrigerant layer 4 or the refrigerant gas layer 5 and the resin constituting the insulating coating shrinks together with the lead conductor 3 made of a copper conductor, the insulating coating portion 3a When the lead conductor 3 and the insulating coating covering the lead conductor 3 are in close contact (including adhesion), both of them whose linear expansion coefficients are different from each other regardless of the contraction amount or contraction speed. Try to shrink together. For this reason, excessive stress is applied to both of them, and the resin having relatively low mechanical strength, that is, the insulating coating is cracked or cracked.

  On the other hand, in the insulation coating portion 3a of the lead conductor 3 of the present invention, at least in the portion located in the temperature inclined portion 12 where the cooling amount is large, a release treatment is performed between the lead conductor 3 and the insulation coating. For this reason, when the lead conductor 3 and the insulation coating are cooled by the liquid refrigerant layer 4 or the refrigerant gas layer 5 and both contract, a release treatment is performed between the two, causing slippage between the two, It is presumed that the contraction of the film becomes difficult to be disturbed, and as a result, the situation where an excessive stress is applied is alleviated.

  In particular, if the outer diameter of the lead conductor 3 positioned in the temperature inclined portion 12 is made thinner as it goes upward as shown in FIG. 2, the insulating coating portion 3a is sequentially cooled from the lower side. When contracting, the lead conductor 3 having a high thermal conductivity is contracted in the radial direction and the longitudinal direction in advance, and then the insulating coating (resin) having a low thermal conductivity is contracted, so that it is generated in the insulating coating. It is thought that the stress is further relaxed.

  Further, in the lead conductor 3 having the structure described above, as a result of using an epoxy resin instead of ethylene propylene rubber as the resin for the insulation coating, the insulation coating was less cracked.

  Further, as described above, after the lead conductor 3 is incorporated in the temperature inclined portion 12, first, only the portion 3n where the conductor at the lower end is exposed is immersed in the liquid refrigerant layer 4, and this portion is cooled first. The level of the liquid refrigerant layer 4 was raised, but as a result, the lead conductor 3 was cooled earlier than the insulating coating side and contracted, so that some stress was generated on the contracted insulating coating after that. It is speculated that it was made smaller.

It is an expanded longitudinal cross-sectional view which shows the principal part of the termination | terminus connection part of the cryogenic cable of this invention. FIG. 2 is an enlarged partial cross-sectional view showing an insulating coating portion of the lead conductor of FIG. 1. It is a principal part longitudinal cross-sectional view of the termination | terminus connection part of the conventional cryogenic cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Lead conductor 3a Insulation coating | cover part 3b Conductor exposure part 4 Liquid refrigerant | coolant layer 5 Refrigerant gas layer 6 Flange 7 Insulator 8 Fluid insulator 12 Temperature gradient part 13 High voltage extraction part

Claims (2)

In a termination connection part of a cryogenic cable having a lead conductor drawn from a cryogenic temperature to a normal temperature through a liquid refrigerant layer, a refrigerant gas layer, and a high voltage lead part in the temperature slope part, the lead conductor is located in the temperature slope part The insulation coating having electric field control members at both ends thereof, and at least the portion located in the temperature gradient portion and the insulation conductor and the insulation coating. A mold release process is performed therebetween, and the lead conductor has an outer diameter of a portion located in the high-voltage lead portion larger than an outer diameter of a portion located in the temperature slope portion, and the inside of the temperature slope portion. A terminal connection part of a cryogenic cable, characterized in that the outer diameter of the portion located in the taper is tapered toward the upper part. The insulating coating sealing end of the cryogenic cable according to claim 1, characterized in that it consists of an epoxy resin.

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