HK1069685A - Termination structure of cryogenic cable - Google Patents

Description

Terminal member of cryogenic cable

Technical Field

The present invention relates to a terminal structure of a cryogenic cable such as a superconducting cable, and more particularly to a structure for coupling one end of the cryogenic cable to one end of a wire connected to an external current system, which is at room temperature.

Background

The conventional conductive cable has its end portion vertically raised to the longitudinal direction of the conventional conductive cable to be linearly connected to one end portion of the electric wire extended to the external current system.

For cryogenic cables, the cable thermally contracts when cooled, for example, with liquid nitrogen, whereas in the event of a temperature increase of the cable, such as due to some accident, the cable thermally expands. In these cases, the end of the cryogenic cable is disposed in the longitudinal direction of the cable. Therefore, the end portion is provided with a blocking part (blocking part) that blocks the cable from moving in the longitudinal direction. Accordingly, the end of the cryogenic cable is linearly connected to a conventional conductor and then connected to the end of the wire disposed perpendicular thereto, thereby forming an L-shaped joint (joint).

The end portion of the electric wire is also disposed in the longitudinal direction of the electric wire due to thermal contraction caused by cooling with, for example, liquid nitrogen, thermal expansion caused by heat generated by the flow of electric current therethrough, and the like. In this case, the joint portion may be broken, resulting in deterioration of the reliability of the entire system.

For example, japanese laid-open patent application No.8-265956 discloses a method of absorbing (absorbing) thermal contraction and expansion of a low-temperature cable. According to this method, the end portion of the cryogenic cable is made movable, and the end portion slides in accordance with the amount of thermal contraction and expansion of the cryogenic cable, thereby absorbing the amount of thermal contraction and expansion.

In particular, the end of such a cryogenic cable comprises: a mechanism for sliding said end in the longitudinal direction of the cryogenic cable, and means for measuring any change in the cryogenic cable, for example due to thermal contraction thereof, the end sliding in accordance with said measurement. More specifically, the sliding mechanism for sliding the end portion in the longitudinal direction of the cryogenic cable has a wheel on a joint portion between the cryogenic cable and the electric wire, and the joint portion on the wheel moves correspondingly along the rail.

However, the above-described method requires means for sliding the cryogenic cable end in the longitudinal direction of the cable, i.e. for example wheels and rails, and means for measuring any changes in the cable caused by, for example, thermal contraction of the cable. Therefore, such a structure is complicated, and an additional operation of sliding the end portion in the longitudinal direction of the cable according to the measurement result is required, thereby causing such problems as deterioration in reliability and increase in manufacturing and maintenance costs. And other problems arise because the wires also slide in the longitudinal direction of the cable, and the connector part between the wires and the external current system is subjected to stresses, for example, due to sliding in the longitudinal direction of the cable.

In addition, the above method is intended to absorb thermal contraction and expansion of the cryogenic cable in the longitudinal direction, and is not intended to absorb any displacement in the longitudinal direction of the electric wire. Therefore, this method cannot solve the problem of breaking of the contact or connector portion due to any displacement in the longitudinal direction of the electric wire, and the resulting problem of impairing the reliability of the entire system.

Disclosure of Invention

An object of the present invention is to provide a terminal member of a cryogenic cable capable of absorbing movement in three dimensions due to thermal contraction and thermal expansion of the cryogenic cable and electric wires and ensuring sufficient current carrying capacity without the above-described complicated members and special operations.

According to a first aspect of the present invention, in order to achieve the above object, a cryogenic cable and an electric wire are coupled to each other through a flexible conductor.

Specifically, according to a first aspect of the present invention, there is provided a terminal member of a cryogenic cable, which member causes one end portion of the cryogenic cable and one end portion of an electric wire to be coupled to each other through a flexible conductor. The flexible conductor can thus absorb any movement of the end of the cryogenic cable in its longitudinal direction and accommodate any deviations in the three-dimensional direction.

According to the second aspect of the present invention, the connection is achieved using a multi-contact (multi-contact) so as to absorb any movement of the end of the wire in the longitudinal direction thereof more effectively.

In particular, according to a second aspect of the present invention, there is provided the terminal member of the cryogenic cable of the first aspect, which has a conductive terminal on one end of the electric wire, and the end of the electric wire and the conductive terminal are connected to each other by multiple contacts.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

Drawings

Fig. 1 is a cross-sectional view specifically illustrating a terminal member of a cryogenic cable according to the present invention.

Detailed Description

Generally, a conventional conductor is linearly connected to one end of the cryogenic cable, and an electrically conductive terminal (hereinafter, referred to as a conductive terminal) formed of a conventional conductive material is further provided on a front end of the conventional conductor so as to be coupled with one end of the electric wire. Conductive terminations are also provided on the ends of the wires to facilitate coupling. Here, if the end of the cryogenic cable or wire has conventional conductors and conductive terminals, the term "end" refers to the end that contains these conventional conductors and conductive terminals.

The flexible conductor couples respective ends of the cryogenic cable and the electrical wire to each other, and in addition to being flexible, the flexible conductor needs to have sufficient current carrying capacity characteristics. A preferred embodiment of a conductor meeting these requirements is a braided wire. The braided wire is an assembly of many parallel thin metal wires. For example, copper or aluminum wires may be used.

The respective ends of the braided wires are connected to the ends of the cryogenic cable and the ends of the electric wires, respectively. The end of the cryogenic cable and/or the end of the electric wire is provided with a (corresponding) electrically conductive terminal and preferably the electrically conductive terminal and the braided wire are connected to each other by brazing (e.g. silver soldering), soldering or crimping of the electrically conductive terminal to ensure connection and large current carrying capacity. The conductive terminals have a shape and size suitable for ensuring sufficient current carrying capacity, and are preferably made of, for example, copper or aluminum.

If the terminal member of the cryogenic cable of the present invention is used to transmit electric power, a high voltage is applied to the terminal member of the cryogenic cable. Then, if the coupling section between the cryogenic cable and the respective end of the wire or the downstream portion of the wire has any protruding portion, electric field concentration occurs at the protruding portion and thus the allowable stress is exceeded. For this reason, the coupling section between the cryogenic cable end and the wire end is preferably covered with an electric field attenuation shield by which the electric field can be controlled.

The electrical line is, for example, a conductor for connection to an external current system and is made, for example, of copper. The wire is typically tubular and, for example, nitrogen gas may flow in the tube for cooling. Furthermore, for sensors measuring the temperature of e.g. the lower part of the electrical line, a cable may be arranged through the tube. It should be noted that tubular conductors are not significantly disadvantageous in terms of electrical conduction compared to solid conductors because of the skin effect of the current.

A large voltage is applied to the wire. Therefore, in order to maintain electrical insulation from the ground portion, the electric wire is generally covered with a sleeve made of an insulating material, and the sleeve is covered with a tubular insulator (pipe). However, in most cases the lower part of the wire is not covered with an electric field attenuating shield, for example, in order to be connected to a conductive terminal. In this case, for example, the exposed lower portion of the electric wire is preferably covered with an electric field attenuation shield, and a space formed between the lower portion of the electric wire and a grounded member such as a container or a sidewall is filled with an electrically insulating coolant such as nitrogen gas. Preferably, the bushing is made of FRP (fiber reinforced plastic), and more preferably GFRP (glass fiber reinforced plastic).

As described above, the end of the wire preferably has a conductive terminal. Also, the end of the electric wire moves in the longitudinal direction of the electric wire due to, for example, thermal contraction of the electric wire. To absorb this movement, the wire and the conductive terminal are preferably interconnected by multiple contacts.

Specifically, the conductive terminal has a hollow portion having a diameter slightly larger than an outer diameter of the electric wire, and a predetermined number of grooves are formed in the hollow portion or on an outer circumference of a lower portion of the electric wire. One or more conductive elastomers, commonly called multi-bands, are inserted into these grooves, and then the ends of the wires are inserted into the hollow portions of the conductive terminals to connect them to each other.

By the above-described multi-contact connection, a large current can be carried, and the end of the electric wire can slide in the hollow portion, which is preferable in terms of absorbing the movement of the end of the electric wire in the longitudinal direction of the electric wire.

Specific examples of preferred embodiments of the present invention will now be given. Fig. 1 shows a conventional conductor 1 linearly connected to one end of a cryogenic cable, and a conductive terminal 2 fixed to one end of the conventional conductor 1. In the present embodiment, the conventional lead wire 1 is inserted into the hollow portion of the conductive terminal 2 and fixed thereto by the screw 3. The end 4 of the conductive terminal 2 is connected to the braided wire 5 by soldering or brazing.

The method of connecting the braided wire 5, the conductive terminal 2 and the conventional conductor 1 is not limited to the above-described method. For example, the conductive terminal 2 and the conventional conductor 1 may be connected to each other by a multi-contact. The braided wire 5 and the conductive terminal 2 may be connected to each other by a rectangular-racquet-shaped conductive terminal, to which an end of the braided wire 5 may be fixed using a screw, for example. Also, as described above, crimping may be suitably used in addition to soldering and brazing. Crimping of the conductive terminals is advantageous without the need for silver soldering or brazing materials.

The other end of the braided wire 5 is connected to a tip 6 of the conductive terminal 7 by soldering or brazing, the tip 6 being provided on the end of the electric wire 10. In the hollow portion provided on the conductive terminal 7, the lower portion of the end portion of the electric wire 10 is inserted and connected to each other with the multiple contacts 8.

The tubular wire 10 is covered with a stainless steel or aluminum tube 9. The lower portion of the tube 9 is formed with a flange 11, and the flange 11 is fixed with screws to a flange 12 formed on the upper portion of the conductive terminal 7. The conductive terminal 2 and the conventional conductor 1 are immersed in liquid nitrogen, and such a flange structure is used to prevent the liquid nitrogen from leaking to the outside.

The tube 9 is covered with a sleeve 13, which is further covered with a tube insulator (not shown). Note that the lower part of the electric wire 10 is not covered with the sleeve 13 and the part extending downward from this part is covered with the electric field attenuation shield 14. The electric field attenuation shield 14 has a circular shape without protrusions for the purpose of stress relaxation.

With the terminal member of the cryogenic cable of the present invention, thermal contraction of the cable occurring when the cable is cooled and thermal expansion of the cable occurring in the case where the cable grows due to an unexpected temperature can be absorbed by deformation of the flexible conductor. Therefore, even if the cable is thermally contracted or expanded, no pressure, such as pressure, is generated at the end of the cable. In this way, it is possible to prevent the terminal member from breaking, for example, due to pressure, and thus improve the reliability of the system. This effect is significantly enhanced when the flexible conductor is a braided wire.

With the terminal member of the cryogenic cable of the present invention, thermal contraction of the cable occurring when the cable is cooled and thermal expansion of the cable occurring in the case where the cable has to be raised in temperature due to some accident can be absorbed by deformation of the flexible conductor. Therefore, even if the cable thermally contracts or thermally expands, for example, no pressure is generated on the end of the cable. In this way, for example, the terminal member can be prevented from being broken due to pressure, and thus reliability can be improved. This effect is particularly enhanced when the flexible conductor is a braided wire.

Furthermore, with the terminal member of the present invention, during assembly of the terminal member, deviations in the longitudinal direction of the cryogenic cable and in the direction perpendicular to the longitudinal direction can be absorbed by deformation of the flexible conductor. Thus, other effects of facilitating the assembly of the terminal member can be obtained.

Also, since the conductive terminal is provided at the end of the electric wire, and the electric wire and the end of the conductive terminal are connected to each other through the multiple contacts, any movement in the longitudinal direction of the electric wire due to thermal contraction or expansion of the electric wire can be absorbed.

Although the present invention has been described and illustrated in detail, it should be clearly understood that: the drawings and examples are to be regarded as illustrative in nature and not as restrictive, and the spirit and scope of the present invention is to be limited only by the appended claims.

Claims (6)

1. A termination component for a cryogenic cable comprising:

a cryogenic cable end (1);

a wire end (10); and

a flexible conductor (5) connecting the cryogenic cable end (1) and the wire end (10) to each other.

2. A termination member of a cryogenic cable according to claim 1, wherein the flexible conductor (5) is a braided wire.

3. A termination member of a cryogenic cable according to claim 2, wherein the braided wire (5) is made of copper or aluminium.

4. A terminal member of a cryogenic cable according to claim 3, wherein an electrically conductive terminal (2, 7) is provided to the cryogenic cable end (1) and/or the wire end (10), and the electrically conductive terminal (2, 7) and the braided wire (5) are connected to each other by brazing, soldering or crimping of the electrically conductive terminal (2, 7).

5. The terminal member of a cryogenic cable according to claim 1, wherein the coupling portion between the cryogenic cable end (1) and the wire end (10) is covered with an electric field attenuation shield (14).

6. A terminal member of a cryogenic cable according to claim 1, wherein a conductive terminal (7) is provided to the wire end (10), and the wire end (10) and the conductive terminal (7) are connected to each other by a multi-contact (8).