JP2005237062A - Terminal structure of superconductive cable and super conductive cable line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized terminal structure of a superconductive cable that can further reduce a Joule loss and heat intrusion, and the superconductive cable conduit equipped with the terminal structure. <P>SOLUTION: The small-sized terminal structure comprises: a conductor 20 electrically connected to the end of the superconductive cable 100 (cable core 102); a bushing 21 containing the conductor 20; and a low-temperature tank 22 into which the connection side of the cable of the conductor 10 is accommodated. The terminal structure further comprises a power changer 25 that changes the magnitude of a voltage applied to the superconductive cable 100 or a voltage applied to the conductor 20 between the end of a lead 114 and the conductor 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a terminal structure of a superconducting cable disposed between a room temperature side and a cryogenic side, and a superconducting cable line having the terminal structure. In particular, the present invention relates to a terminal structure of a small superconducting cable that enables large-capacity power transmission using a superconducting cable.

  As a terminal structure of a superconducting cable, for example, a structure shown in FIG. 6 is known (see Patent Document 1). FIG. 6 is a schematic configuration diagram showing a terminal structure of a conventional superconducting cable. This terminal structure is composed of an end portion of the superconducting cable 100, a conductor portion 110a that is electrically connected between the cable 100 at an extremely low temperature and the normal temperature side, and one end side of the conductor portion 110a (connection side to the cable 100). A low-temperature tank 111 for storing the container, a vacuum vessel 112 covering the outer periphery of the low-temperature vessel 111, and a soot tube 113 protruding from the room temperature side of the vacuum vessel 112.

  The superconducting cable 100 includes a cable core 102 having a superconducting conductor. In the configuration shown in FIG. 6, a conductive lead 114 is connected to the core 102, and the superconducting cable is connected to the core 102 via the lead 114 and the joint 115. The conductor and the conductor portion 110a are electrically connected. The conductor portion 110a is usually formed of a normal conductive material such as copper or aluminum, and is disposed from the low-temperature vessel 111 through the heat insulating layer 112a of the vacuum vessel 112 to the soot tube 113. The conductor portion 110a is built in a bushing 110b made of an insulating material such as FRP. In the cryogenic bath 111, one end side of the lead portion 114 (the connection side with the conductor portion 110a (the left side in FIG. 6)) and one end side of the conductor portion 110 (the connection side with the superconducting conductor (the same lower side)) A refrigerant such as liquid nitrogen is cooled. The soot tube 113 accommodates the other end side (the upper side in FIG. 6) of the conductor portion 110a and is filled with an insulating fluid 113a such as insulating oil. A lead part refrigerant tank 116 is disposed on the outer periphery of the lead part 114, and a lead part vacuum vessel 117 is disposed on the outer periphery thereof.

JP 2002-238144 JP

  However, the conventional terminal structure has a problem that it is difficult to reduce the size when trying to reduce both the Joule loss and the intrusion heat from the normal temperature side to the extremely low temperature side.

  The superconducting cable is cooled to an extremely low temperature (for example, about 77 K) with a refrigerant such as liquid nitrogen, thereby making the superconducting conductor portion in a superconducting state and reducing the resistance, thereby enabling large current transmission. On the other hand, since the power equipment outside the superconducting cable line is used at room temperature, power is supplied to the power equipment and the like by drawing it from the cryogenic temperature to room temperature at the end of the superconducting cable. Therefore, a large current flows through the conductor portion connecting the superconducting cable and the normal temperature side so as to supply electric power equivalent to that of the superconducting cable to the normal temperature side. At this time, since the conductor portion formed of the normal conducting material has a larger resistance than the superconducting conductor, the Joule loss becomes very large when a large current flows.

  In order to reduce Joule loss due to energization of a large current in the conductor part, it is conceivable to increase the cross-sectional area (outer diameter) of the conductor part to reduce the resistance. However, as the cross-sectional area of the conductor portion increases in size and diameter, heat penetration from the room temperature side to the cryogenic side increases, and the superconducting state may not be sufficiently maintained on the cryogenic temperature side. Therefore, it is necessary to reduce the heat intrusion in order to sufficiently maintain the superconducting state. However, if the cooling capacity is increased by, for example, placing a large refrigerator in the low-temperature tank, the energy required to maintain a high cooling capacity will be excessive in addition to the increase in the size of the terminal structure, and superconducting cables will be used. The effect to do becomes small. Also, without installing a large refrigerator, the length of the conductor part is sufficient for thermal insulation, that is, when the length is increased, the length of the conductor part is increased in addition to an increase in the cross-sectional area of the conductor part. As in the case described above, the terminal structure is enlarged and it is difficult to make it practical. Furthermore, even if heat penetration is reduced by increasing the length of the conductor portion, the Joule loss increases, so the effect of reducing power transmission loss is reduced.

  In addition, when the cross-sectional area of the conductor portion is increased in size and increased in diameter, the outer diameter of the bushing increases accordingly. At this time, the one end side of the bushing disposed in the low-temperature tank has a problem in terms of mechanical strength such that the shrinkage stress at the time of cooling by the refrigerant becomes large and the crack becomes easy to break.

  The terminal structure of the superconducting cable is desired to be smaller due to the limitation of the space at the installation location. Therefore, a main object of the present invention is to provide a smaller superconducting cable terminal structure while reducing Joule loss and loss due to heat penetration. Another object of the present invention is to provide a superconducting cable line having the terminal structure of the superconducting cable.

  The present invention achieves the above object by reducing the amount of current that flows per conductor portion built in one bushing.

(Diversion method)
As a technique for reducing the amount of current flowing through the conductor portion, one suggests that a plurality of conductor portions are provided and the current flowing through the superconducting cable is divided into each conductor portion. That is, the present invention is a terminal structure of a superconducting cable having a superconducting conductor cooled by a refrigerant. In this terminal structure, there are a plurality of conductor portions electrically connected to the end portions of the superconducting conductor, a plurality of bushings containing a conductor portion for each conductor portion, and a connection side of the conductor portions to the superconducting conductor. It is characterized by comprising a cryogenic bath to be stored.

  If a large current is passed through one conductor and the cross-sectional area (outer diameter) of the conductor is increased in order to reduce resistance in order to reduce Joule loss, the conductor must be lengthened in consideration of thermal insulation. Absent. Then, Joule loss will increase. On the other hand, in the present invention, a plurality of conductor portions are arranged in parallel, and a large current flowing in the superconducting cable is shunted to each conductor portion, thereby reducing the current flowing per conductor portion built in the bushing. Thus, the joule loss is reduced. Since the Joule loss is proportional to the square of the current value, the Joule loss can be reduced by reducing the current value. Therefore, it is not necessary to excessively increase the cross-sectional area of the conductor portion incorporated in the bushing, and as a result, the length necessary for thermal insulation can be reduced, specifically, a practical size. Moreover, Joule loss can be reduced more by shortening the said conductor part.

(Voltage change method)
As another method for reducing the amount of current flowing through the conductor, it is proposed to change the voltage applied to the superconducting cable or the voltage applied to the conductor. That is, the present invention is a terminal structure of a superconducting cable having a superconducting conductor cooled by a refrigerant, a conductor part electrically connected to an end of the superconducting conductor, a bushing incorporating the conductor part, With And a power changing device that is disposed between the end portion of the superconducting conductor and the conductor portion and changes a voltage applied to the superconducting cable or a voltage applied to the conductor portion to a voltage having a different magnitude, and the conductor The structure which comprises the connection side with the electric power change apparatus of a part and the low-temperature tank in which an electric power change apparatus is accommodated is proposed.

  Power is expressed as the product of voltage and current. Therefore, it is effective to change the voltage in order to change the current without changing the magnitude of the electric power. Therefore, the present invention includes a power changing device capable of changing the voltage applied to the superconducting cable or the voltage applied to the conductor to a voltage having a different magnitude. This power changing device may be appropriately selected according to the direction of power transmission. For example, when power is transmitted from a superconducting cable through which a large current flows to the room temperature side, the power changing device can increase the voltage and is applied to the cable. By raising the voltage with the power changing device, the amount of power transmitted to the cable can be kept as it is, and the current flowing through the conductor part built in the bushing can be reduced and transmitted to the room temperature side. On the other hand, when power is transmitted from the room temperature side to the superconducting cable, the conductor portion built in the bushing transmits power with a high voltage and a small current value. Therefore, the power change device can reduce the voltage, and can increase the current flowing in the superconducting cable while maintaining the amount of power transmitted to the conductor. That is, in the voltage change method, power is transmitted in a high voltage and small current state in a conductor portion built in the bushing, and power is transmitted in a small voltage and large current state in a superconducting cable. Since a high voltage is applied to the conductor part built in the bushing, a sufficient current can be passed even if the cross-sectional area of the conductor part is reduced. Therefore, this method can reduce the cross-sectional area of the conductor portion built in the bushing, and can also reduce the distance required for thermal insulation, so this conductor portion can be further shortened, It is possible to further reduce power transmission loss as compared with the diversion method.

Hereinafter, the present invention will be described in more detail.
In the present invention, the superconducting cable may be a single-phase superconducting cable having one cable core having a superconducting conductor or a multiphase superconducting cable having a plurality of the cable cores. In the latter case, for example, a three-core three-phase superconducting cable in which three cable cores are twisted and accommodated in a heat insulating tube can be used. A known single-phase superconducting cable or multiphase superconducting cable may be used.

  The superconducting conductor may be formed, for example, by spirally winding a wire made of a Bi2223 superconducting material, and may be a single layer or a multilayer. In the case of a multilayer structure, an interlayer insulating layer may be provided. The interlayer insulating layer may be provided by winding insulating paper such as kraft paper or semi-synthetic insulating paper such as PPLP (registered trademark). The outer periphery of the superconducting conductor is provided with an electrically insulating layer formed by winding semi-synthetic insulating paper such as PPLP (registered trademark) or insulating paper such as kraft paper. A shield layer configured similarly to the superconducting conductor may be provided on the outer periphery of the electrical insulating layer.

  In the superconducting cable, the superconducting conductor is cooled by a refrigerant such as liquid nitrogen so that the superconducting conductor can maintain the superconducting state. Therefore, in the terminal structure of the present invention, the end portion of the superconducting cable may be housed in a low-temperature tank filled with a refrigerant, for example, and the outer periphery thereof may be disposed in a vacuum container having a heat insulating layer. The cryostat and the vacuum vessel are preferably made of a metal such as stainless steel having excellent strength. It is good also as a structure similar to the conventional vacuum vessel and a low-temperature tank. The refrigerant may be circulated in a pressurized state.

  The connection between the end portion of the superconducting cable and the conductor portion described later may be performed directly, or may be performed indirectly by connecting a lead portion to the end portion and connecting the conductor portion to the lead portion. Good. In the former case, one end side of the conductor portion (connection side to the same end portion) may be housed in a low temperature bath that cools the end portion of the superconducting cable. In the latter case, a low-temperature bath that houses one end side (connection side to the superconducting cable) of the conductor portion and a low-temperature bath that houses the same end portion may be arranged separately. In the case where a separate low temperature bath is provided for the conductor portion, this low temperature bath may also be disposed in a vacuum vessel having a heat insulating layer. As the lead portion, a lead portion formed of a normal conductive material such as copper, copper alloy, aluminum, or aluminum alloy can be used. An insulating material such as an epoxy unit or reinforced insulating paper may be disposed on the outer periphery of the lead portion, and stored in a lead portion refrigerant tank filled with a refrigerant. You may arrange | position a lead part refrigerant | coolant tank in the lead part vacuum vessel which provides a heat insulation layer.

In the present invention, a conductor is connected to the end of the superconducting cable to perform power transmission between the cryogenic temperature side and the room temperature side. The conductor portion only needs to be capable of taking electrical continuity with the superconducting conductor of the superconducting cable. The temperature of the refrigerant used in the cable, for example, when liquid nitrogen is used as the refrigerant, near the temperature of liquid nitrogen. In other words, it may be formed of a normal conductive material such as a metal having a small electrical resistance, such as copper or aluminum (both having a specific resistance ρ = 2 × 10 ⁻⁷ Ω · cm of 77K). This conductor is incorporated in a bushing having an insulating function. The bushing may be formed from an insulating material, or may be configured such that an insulating material is provided on the outer periphery of a metal cylinder such as stainless steel. For example, in the former case, the bushing may be formed integrally with the conductor portion. In the latter case, the conductor portion may be inserted and arranged inside the metal cylinder. Examples of the insulating material include an insulating resin, for example, an insulating rubber material such as ethylene propylene rubber, and reinforced fiber plastic (FRP). FRP is preferable because it has higher insulation performance.

One end side of the conductor portion connected to the end portion of the superconducting cable is disposed on the low temperature side, and the other end side is disposed on the normal temperature side. One end side arranged on the low temperature side of the conductor part is arranged in the low temperature bath, and the other end side arranged on the normal temperature side is arranged in the soot tube. Fill the pipe with an insulating fluid such as insulating oil or SF ₆ gas. That is, the conductor portion is arranged from the low temperature tank through the heat insulating layer in the vacuum vessel and over the soot tube.

  In the shunting method, the connection between the superconducting conductor (or the lead portion) of the superconducting cable and the conductor portion can be performed, for example, via a branch connection portion formed of a conductive material. The branch connection portion is not particularly limited as long as the end portion of the superconducting conductor (or the lead portion) and the conductor portion can be attached. The conductive material may be either a superconductive material or a normal conductive material. In the case of a normal conductive material, copper, aluminum, or the like is preferable.

  In the voltage change method, a power change device capable of changing the voltage applied to the cable or the magnitude of the voltage applied to the conductor is provided between the terminal of the superconducting cable and the conductor. When power is transmitted from the normal temperature side toward the superconducting cable, it is preferable to use a power changing device that changes the magnitude of the voltage applied to the conductor, specifically, a voltage that can be reduced. When power is transmitted from the superconducting cable toward the room temperature side, the power changing device may change the voltage applied to the superconducting cable, specifically, a device capable of increasing the voltage.

  In addition, the power change device may be appropriately selected according to the normal temperature side, the type of power transmission of the superconducting cable (AC power transmission, DC power transmission), and the function capable of changing the magnitude of the voltage, specifically, the transformation function and frequency. It is good to use what has at least one of the conversion functions. For example, the AC voltage applied to the conductor part or superconducting cable can be changed to an AC voltage or DC voltage of different magnitude, i.e. AC / AC equipment (transformer), AC / DC converter, conductor part or superconductivity Examples include a DC voltage applied to a cable that can be changed to an AC voltage or a DC voltage having different magnitudes, that is, a DC / AC converter and a DC / DC converter. Table 1 shows examples of line patterns and power change devices.

  Each line pattern shown in Table 1 indicates a line that transmits power from the room temperature side A on the left side to the room temperature side B on the right side through a superconducting cable. In the line that transmits power from the room temperature side A on the left side to the room temperature side B on the right side via the superconducting cable as shown in Table 1, only between the room temperature side A and the superconducting cable, or between the superconducting cable and the room temperature side Power change equipment may be provided only between B and power change equipment as shown in Table 1 between room temperature side A and the superconducting cable, and between the superconducting cable and room temperature side B. It may be provided. In the former case, for example, the line pattern 4 may include a power changing device only between the room temperature side A and the superconducting cable, and the line pattern 5 may change the power only between the superconducting cable and the room temperature side B. Equipment may be provided. In the latter case, for example, in the case where both the room temperature sides A and B and the superconducting cable perform AC transmission like the line pattern 1 shown in Table 1, the power change device is a transformer (AC / AC device), The voltage applied to the conductor portion when power is transmitted from the side A to the superconducting cable side may be reduced, and the voltage applied to the superconducting cable may be increased when power is transmitted from the superconducting cable side to the room temperature side B. Also, if the type of power transmission on room temperature side B is different from the type of power transmission on superconducting cable, for example, room temperature side A and superconducting cable: AC transmission, room temperature side B: room temperature side in case of DC transmission It is recommended to use different types of power change devices to be placed on A and room temperature side B (room temperature side A: AC / AC equipment, room temperature side B: AC / DC converter).

  In particular, when the superconducting cable performs DC power transmission as in the line patterns 3 to 6 shown in Table 1, the power transmission loss can be reduced more than in the case of AC, and therefore it is preferable because the loss can be further reduced. At this time, the power conversion device arranged on the room temperature side A is capable of changing the AC voltage or DC voltage applied to the conductor part to a DC voltage having a different magnitude, specifically, an AC / DC converter, DC / DC The DC converter, the power conversion device placed on the room temperature side B, can change the DC voltage applied to the superconducting cable to a DC voltage of a different magnitude, specifically a DC / AC converter, DC / DC Use a transducer.

  The AC / AC device may be AC direct conversion that directly converts AC to AC, or AC indirect conversion that temporarily converts AC to DC and then converts it to AC again. Similarly, the DC / DC converter may be direct DC conversion for directly converting DC to DC, or direct current indirect conversion for once converting DC to AC and then converting to DC again. Further, these power change devices may be superconducting devices formed of a superconducting material, normal conducting devices formed of a normal conducting material, or known devices may be used. In the case of a normal conducting device, the configuration is easier than that of a superconducting device, and the equipment cost can be reduced.

  The connection side of the power change device and the power change device of the conductor portion is disposed in a low temperature bath. In the case where the end of the superconducting cable (or the end of the lead) is housed together, the cryostat is preferably filled with a refrigerant such as liquid nitrogen that cools the cable. At this time, when using a superconducting device as the power changing device, the refrigerant used for cooling the end of the superconducting cable can also be used for cooling the power changing device, and it is necessary to provide a cooling mechanism for the power changing device separately. Therefore, the efficiency of the cooling system can be improved.

  When using a normal conducting device as a power changing device, a low temperature bath (hereinafter referred to as an intermediate temperature bath) that houses the connection side of the power changing device and the power changing device of the conductor part and a superconducting cable end are stored. A low-temperature tank (hereinafter referred to as a refrigerant tank) is provided separately, and the medium-temperature tank is controlled to a temperature range below the normal temperature of the refrigerant that cools the end of the superconducting cable, and the normal conductive equipment is placed in the medium-temperature tank. It is good to arrange in. Therefore, for example, the refrigerant tank may be a liquid refrigerant layer filled with a liquid refrigerant such as liquid nitrogen, and the intermediate temperature tank may be a gas refrigerant layer filled with a gas refrigerant such as nitrogen gas. Further, a liquid refrigerant having a temperature capable of maintaining the superconducting state may be filled in the refrigerant tank, and a liquid refrigerant having a higher temperature than the liquid refrigerant filled in the refrigerant tank may be filled in the intermediate temperature tank. In order to control the inside of the intermediate temperature tank to a temperature range below the normal temperature of the refrigerant that cools the end of the superconducting cable, the two tanks are completely separated by interposing a heat insulating layer between the refrigerant tank and the intermediate temperature tank. It is preferable to have a two-stage heat insulation structure. In addition, maintenance such as inspection, maintenance, and replacement of the superconducting cable disposed in the refrigerant tank and the power change device disposed in the intermediate temperature tank can be performed individually, and thus maintainability is preferable. The medium temperature bath is also preferably formed of a metal having excellent strength such as stainless steel.

(Diversion and voltage change method)
A combination of the shunt method and the voltage change method may be used. For example, in a superconducting cable line, a shunt system may be constructed on one end side of the superconducting cable and a voltage change system may be constructed on the other end side. Specifically, for example, in a line that transmits power from the room temperature side A to the room temperature side B via the superconducting cable as shown in Table 1, a shunting method is constructed between the room temperature side A and the superconducting cable. A voltage change method may be established between the superconducting cable and the normal temperature side B, or a voltage change method may be established between the normal temperature side A and the superconducting cable, between the superconducting cable and the normal temperature side B. In this case, a diversion system may be constructed. Moreover, you may construct | assemble both a shunting system and a voltage change system only by the one end side of a superconducting cable. That is, the power changing device may be arranged in a shunting method. Specifically, for example, when connecting a plurality of conductor portions and the end portion of a superconducting cable at a branch connection portion, the configuration in which the power changing device is arranged between the end portion of the cable and the branch connection portion is as follows. Can be mentioned. With this configuration, for example, when power is transmitted from the superconducting cable to the room temperature side, the current transmitted to the conductor portion can be reduced by increasing the voltage in the power change device, and this current is further divided into a plurality of conductor portions. Therefore, the current flowing through each conductor portion becomes smaller. Therefore, the area of the cross-sectional area (outer diameter) of each conductor portion can be further reduced, and the length of the conductor portion can be further shortened. Therefore, further miniaturization of the terminal structure is realized.

  The terminal structure of the present invention is suitably constructed at the terminal end of a superconducting cable line connected to an electric device or normal conducting cable used at room temperature.

  The terminal structure of the present invention enables at least one of a shunt structure and a voltage change structure at the end of the superconducting cable to enable large-current power transmission through the cable and a conductor portion connected to the end of the cable. The current flowing per one can be reduced. Therefore, while reducing Joule loss and intrusion heat, it is possible to provide a terminal structure with a practical size by shortening the conductor portion. In particular, in the case of the voltage change structure, the cross-sectional area (outer diameter) can be further reduced, so that further miniaturization of the conductor portion can be realized. Therefore, the terminal structure itself can be reduced in size without reducing the power supplied to the superconducting cable.

  Embodiments of the present invention will be described below.

(Diversion method)
FIG. 1 (A) is a schematic configuration diagram showing the terminal structure of the superconducting cable of the present invention, showing an example in which current flowing through the cable is shunted and supplied to a plurality of conductor parts, and FIG. 1 (B) is a branch connection part. It is the elements on larger scale showing the outline of the structure. Hereinafter, the same reference numerals in the drawings denote the same items. The basic structure of this terminal structure is the same as the terminal structure of the conventional superconducting cable shown in FIG. That is, the conductor 10 electrically connected to the end of the superconducting conductor (not shown in FIG. 1) included in the superconducting cable, the bushing 11 incorporating the conductor 10, and the connection side of the conductor 10 to the superconducting conductor 1 (lower side in FIG. 1), a vacuum vessel 13 covering the outer periphery of the low-temperature vessel 12, and a soot tube 14 disposed on the room temperature side of the vacuum vessel 13. A feature of the present invention is that a plurality of the conductor portions 10 are provided in parallel. This will be described in detail below.

  The superconducting cable 100 used in this example is a three-core one-phase superconducting cable in which three cable cores 102 as shown in FIG. The heat insulating tube 101 has a structure in which a heat insulating material (not shown) is disposed between the double tubes composed of the outer tube 101a and the inner tube 101b, and the inside of the double tube is evacuated. Each cable core 102 includes a former 200, a superconducting conductor 201, an electrical insulating layer 202, a shield layer 203, and a protective layer 204 in order from the center. The superconducting conductor 201 is formed by spirally winding a superconducting wire on the former 200 in multiple layers. The electrical insulating layer 202 is configured by winding semi-synthetic insulating paper. The shield layer 203 is configured by spirally winding a superconducting wire similar to the superconducting conductor 201 on the electrical insulating layer 202. In the shield layer 203, a current of almost the same magnitude is induced in the opposite direction to the current flowing in the superconducting conductor 201 in a steady state. With the magnetic field generated by the induced current, the magnetic field generated from the superconducting conductor 201 can be canceled and the leakage magnetic field to the outside of the cable core 102 can be made almost zero. A space 103 surrounded by the inner tube 101b and each cable core 102 is usually a refrigerant flow path. An anticorrosion layer 104 made of polyvinyl chloride is provided on the outer periphery of the heat insulating tube 101. The following examples also use the three-phase superconducting cable shown in FIG.

  When the superconducting cable 100 is connected to an external electric device, a normal conducting cable, or the like, a terminal structure is formed by branching for each cable core (each phase) at the cable end. FIG. 1 shows a terminal structure in one cable core. In the case of a three-phase superconducting cable, two other such terminal structures are formed. In this example, aluminum lead portions 114 are respectively connected to the ends of the branched cable cores. An epoxy unit 114a having an insulating function and mechanical strength is disposed on the outer periphery of the lead portion 114, and an insulating material 114b such as kraft paper is disposed. The lead portion 114 is connected to the superconducting cable in the lead portion refrigerant tank 116 filled with a refrigerant 116a such as liquid nitrogen, and the lead portion refrigerant tank 116 is contained in the lead portion vacuum vessel 117. The lead part vacuum vessel 117 is connected to the vacuum vessel 13, and a fixing jig 118 made of FRP is disposed between the end surface of the vacuum vessel 117 and the end surface of the cryostat 12.

  The connecting side of the lead part 114 to the conductor part 10 is housed in the low temperature bath 12. The low-temperature tank 12 is made of stainless steel and is housed in a vacuum vessel 13 that is also made of stainless steel. A heat insulating layer 13a is provided between the low-temperature tank 12 and the vacuum vessel 13. In the low-temperature tank 12, a refrigerant 12a such as liquid nitrogen is circulated. Each conductor 10 may be arranged in a separate low temperature bath, but in this example, a plurality of conductors 10 are stored in one low temperature bath 12 in order to simplify the container configuration.

  The end portion of the lead portion and the plurality of conductor portions 10 are connected via the branch connection portion 15. In this example, the branch connection portion 15 includes a block portion 15a connected to the lead portion 114 as shown in FIG. 1 (B), and a connecting portion 15b that connects the block portion 15a and each conductor portion 10. It is. The block portion 15a uses a copper block-like member, and includes a mounting portion 15c at a connection location with the lead portion 114. The connecting part 15b is made of a braided material made of copper, and includes attachment parts 15d at connection points with the lead part 114 and connection parts with the conductor part 10, respectively. By using a flexible braided material, the attachment work to the block part 15a and the attachment work to the conductor part 10 can be easily performed, and the thermal expansion and contraction of the conductor part 10 and the lead part 114 can be absorbed. . In this example, the lead part 114 and the block part 15a, and the block part 15a and each conductor part 10 are connected by fastening metal fittings such as bolts.

  Each conductor 10 was formed of copper having a small electrical resistance near the temperature of liquid nitrogen. In addition, each conductor portion 10 is disposed inside a different bushing 11. The bushing 11 is configured to include an insulating material made of FRP having excellent insulating properties on the outer periphery of a stainless steel cylindrical body. An upper shield 11a made of copper is provided at the upper end of the bushing 11 (the end disposed on the room temperature side). The conductor part 10 and the bushing 11 are arranged from the low-temperature tank 12 through the heat insulating layer 13a to the soot pipe 14, and one end side of the conductor part 10 is connected to the branch connection part 15. Note that the soot tube 14 is filled with an insulating fluid 14a such as insulating oil.

  The terminal structure shown in this example includes a plurality of the conductor portions 10 (four in the example shown in FIG. 1), and these are arranged in parallel. With this configuration, a large current flows through the superconducting cable, and when a current amount equivalent to this current amount is supplied to the room temperature side, the current from the cable is sent to each conductor portion 10 via the branch connection portion 15. Since the amount of current that is shunted and flows through one conductor portion 10 can be reduced, a reduction in Joule loss is realized. Therefore, it is not necessary to excessively increase the cross-sectional area (outer diameter) of each conductor part 10, reducing heat penetration from the normal temperature side to the cryogenic temperature side, and reducing the length required for thermal insulation in the conductor part 10. Even if the conductor portion 10 is made shorter than the conventional one, it is possible to maintain sufficient thermal insulation. As described above, the present invention can supply a current amount equivalent to the amount of current flowing through the superconducting cable, and even if the terminal structure is downsized, the thermal insulation performance is not deteriorated, and the power transmission loss such as Joule loss is reduced. To make it smaller. When the currents flowing through the plurality of conductors 10 are combined, the current amount is equal to the current amount flowing through the superconducting cable, and the same amount as the current flowing through the cable can be supplied to the room temperature side.

  In addition, when power is transmitted from the normal temperature side to the superconducting cable side, the current flowing through each conductor 10 is collected by the branch connection 15 so that the current to the cable can be increased. As described above, the terminal structure of the present invention is configured such that a large current flows in the superconducting cable and a small current flows in each of the conductor portions 10 incorporated in the different bushings 11.

  In this example, a multiphase superconducting cable is shown, but a single-phase superconducting cable can also be used. This also applies to the following examples. In this example, the number of conductors is four, but may be changed as appropriate according to the amount of current flowing through the superconducting cable. Furthermore, in this example, the lead portion 114 is connected to the end portion of the cable core, but the end portion may be connected to the branch connection portion 15. At this time, the end of the cable core may be stored in the low-temperature tank 12. This also applies to the following embodiments.

(Voltage change method 1)
In the first embodiment, the configuration in which the conductor portion is shortened by dividing the current flowing through the superconducting cable has been described. In this example, by changing the voltage applied to the superconducting cable or the voltage applied to the conductor, the current flowing through the conductor is reduced, and the cross-sectional area of the conductor is reduced and shortened. The structure to perform is demonstrated. FIG. 2 is a schematic configuration diagram showing the terminal structure of the superconducting cable of the present invention, and shows an example including a power changing device that changes the magnitude of voltage between an end portion of the cable and a conductor portion.

  The basic structure of the terminal structure shown in FIG. 2 is the same as the terminal structure of the superconducting cable shown in FIG. 1, and a conductor part 20 electrically connected to the end of the superconducting cable 100 (cable core 102), and a conductor A bushing 21 containing the part 20, a low-temperature tank 22 in which the connection side of the conductor part 20 to the same cable is housed, a vacuum container 23 covering the outer periphery of the low-temperature tank 22 and having a heat insulating layer 23a, and the room temperature of the vacuum container 23 And a side tube 24 arranged on the side. That is, the terminal structure of the superconducting cable shown in this example is configured to include one conductor portion 20 as in the terminal structure of the conventional superconducting cable shown in FIG. Each configuration of the conductor part 20 and the bushing 21 is the same as that of the first embodiment, and an upper shield 21a made of copper is provided at the upper end of the bushing 21. A lead part 114 is provided at the end of the cable core 102 as in the first embodiment. A feature of the present invention is that a power changing device 25 that changes the magnitude of the voltage applied to the superconducting cable 100 is provided between the end portion of the lead portion 114 and the conductor portion 20. Hereinafter, this point will be described in detail.

  In this example, the power changing device 25 is an AC / AC device capable of boosting an AC voltage applied to the superconducting cable to an AC voltage. In addition, the power changing device 25 is a superconducting device formed of a superconducting material and is disposed in the low-temperature tank 22, so that the power changing device 25 on the connection side of the lead portion 114 with the power changing device 25 and the conductor portion 20 The refrigerant 22a such as liquid nitrogen used for cooling on the connection side can also be used for cooling the power changing device 25. In the pair of coils constituting the power change device, the coil connected to the conductor part 20 has one end connected to the conductor part 20 and the other end grounded, and the coil connected to the lead part 114 leads one end. The other end is connected to the ground (not shown) of the superconducting cable 100.

  The power supplied to the superconducting cable is represented by the product of voltage and current. Therefore, when power is transmitted from the superconducting cable 100 to the normal temperature side, the voltage applied to the cable 100 by the power changing device 25 is boosted, so that the current to the conductor portion 20 can be reduced. Accordingly, since the Joule loss in the conductor portion 20 can be reduced, the length of the conductor portion 20 can be shortened as in the first embodiment. In addition, since a high voltage is applied to the conductor portion 20, a sufficient current can flow even if the cross-sectional area (outer diameter) of the conductor portion 20 is reduced. For this reason, it is possible to reduce the cross-sectional area of the conductor portion 20. Therefore, even if the conductor part 20 is made thinner and shorter than before, sufficient thermal insulation can be maintained. Further, since the bushing 21 can be reduced by reducing the area of the conductor portion 20, it is possible to reduce cracks during cooling. In addition, since the voltage of the conductor portion 20 is high even if the amount of current is small, it can be made equal to the amount of power supplied to the superconducting cable 100. As described above, the present invention can supply the same amount of power as that of the superconducting cable, and even if the terminal structure is further downsized, the thermal insulation performance is not deteriorated and the transmission loss such as Joule loss can be achieved. Can also be reduced.

  In this example, an AC direct conversion device capable of boosting was used as the power change device, but the type of power transmission on the superconducting cable and the room temperature side (DC or AC), power transmission direction (power transmission from the superconducting cable to the room temperature side, or room temperature) It may be changed as appropriate according to the case of power transmission from the side to the superconducting cable. Specifically, depending on the type of power transmission, either an AC indirect conversion device, a DC / DC converter (DC direct conversion device or DC indirect conversion device), AC / DC converter, or DC / AC converter is used. Good. Also, when transmitting power from the superconducting cable to the room temperature side, use a voltage that can increase the voltage applied to the superconducting cable, and when transmitting power from the room temperature side to the superconducting cable, use a cable that can decrease the voltage applied to the conductor. Good. This also applies to the embodiments described later. Furthermore, in this example, a superconducting device is used as the power changing device, but a normal conducting device formed of a normal conducting material may be used. In the case where the normal conducting device is arranged in a low temperature bath, it is preferable to use a material having a low resistance even at a liquid refrigerant temperature such as copper or aluminum as the normal conducting material.

(Voltage change method 2)
In the voltage change method 1, the case where the vacuum vessel 23 is provided with only the low temperature chamber 22 is shown, but the connection side of the low temperature chamber for storing the lead portion 114 and the power change device 25 of the conductor portion 20 and the power change It is possible to provide a separate cryostat for storing the device 25 and change the temperature of each cryostat. FIG. 3 is a schematic configuration diagram showing a terminal structure of the superconducting cable of the present invention, and shows an example in which a power change device is provided in an intermediate temperature bath.

  The basic structure of the terminal structure shown in FIG. 3 is the same as the terminal structure of the superconducting cable shown in FIG. 2, and the lead part 114 connected to the end of the superconducting cable and the conductor electrically connected to the lead part 114 Portion 20, power changing device 26 connected to conductor portion 20 and lead portion 114, connection side of conductor portion 20 to power changing device 26 and low temperature bath (medium temperature bath) 30 for storing power changing device 26, medium A vacuum vessel 23 for storing the temperature vessel 30 and a soot tube 24 protruding from the room temperature side of the vacuum vessel 23 are provided. The feature of the present invention is that the temperature of the intermediate temperature tank 30 is controlled within a temperature range that is lower than the normal temperature of the refrigerant that cools the superconducting cable, and a low-temperature tank (refrigerant) that houses the lead part 114 in the vacuum vessel 23. It has a tank 31). Hereinafter, this point will be mainly described.

  In this example, the refrigerant tank 31 is a liquid refrigerant layer 31a filled with a liquid refrigerant, and the intermediate temperature tank 30 is a gas refrigerant layer 30a filled with a gas refrigerant. A space between the refrigerant tank 31 and the intermediate temperature tank 30 is a heat insulating layer 23a, which suppresses heat intrusion from the refrigerant tank 31 to the intermediate temperature tank 30.

  In this example, the intermediate temperature tank 30 and the refrigerant tank 31 are made of stainless steel having excellent strength. The gas refrigerant layer 30a is filled with nitrogen gas so that the temperature is higher than the liquid refrigerant (liquid nitrogen, for example, about 77K) filled in the refrigerant tank 31, and can be maintained at a temperature lower than normal temperature. In addition, a temperature adjusting device (not shown) is connected to the intermediate temperature bath 30. By controlling the temperature of the gas refrigerant layer 30a with this temperature adjusting device, for example, the gas refrigerant in the intermediate temperature tank 30 can be controlled to about 170K (about -100 ° C). Further, by providing the intermediate temperature tank 30 and the refrigerant tank 31 having different temperatures in the vacuum vessel 23, a temperature gradient can be provided. In this example, a gas refrigerant is used as the refrigerant of the intermediate temperature tank 30, but it may not be a gas.

  In this example, the power changing device 26 (AC / AC device in this example) that boosts the voltage applied to the superconducting cable is disposed in the intermediate temperature bath 30. The intermediate temperature bath 30 does not have to be a temperature that maintains the superconducting state. Therefore, the power change device 26 can use a normal conductive device made of a normal conductive material. Compared to a superconducting device such as the power change device 25, the normal conducting device does not require a refrigerant for maintaining the superconducting state, and can reduce the refrigerant cost.

  The lead portion 114 and the power change device 26 are connected by a copper member 32, and an electrical insulating layer 33 is provided on the outer periphery of the member 32 at a place where it is disposed on the heat insulating layer 23a. ing.

(Diversion and voltage change method 1)
The configuration of the first embodiment and the second embodiment may be combined. FIG. 4 is a schematic configuration diagram showing a connection portion between the end portion of the superconducting cable (end portion of the lead portion) and the conductor portion in the terminal structure of the superconducting cable of the present invention. In FIG. 4, the cryogenic bath and the vacuum vessel are omitted.

  As a method of further reducing the amount of current flowing through one conductor portion 40, in addition to providing a plurality of conductor portions 40, the voltage applied to the superconducting cable or the magnitude of the voltage applied to the conductor portion is changed. A configuration including the power changing device 27 can be given. For example, as shown in FIG. 4, a power change device 27 is disposed between the end of the lead part 114 and the branch connection part 15, and the voltage applied to the superconducting cable is boosted to reduce the current. A configuration may be adopted in which each of the conductor portions 40 is diverted via the branch connection portion 15. In addition to increasing the voltage applied to the superconducting cable by the power changing device 27 to reduce the current to the conductor portion 40, each of the conductors can be divided by dividing the reduced current through the plurality of conductor portions 40. The current flowing through the portion 40 can be further reduced. Therefore, the cross-sectional area (outer diameter) and length of the conductor part 40 can be further reduced, and the conductor part 40 can be further reduced in size.

(Diversion and voltage change method 2)
A line having the terminal structure of Example 1 on one end side of the superconducting cable and the terminal structure of Example 2 on the other end side may be constructed. For example, in a line that transmits power from room temperature side X to room temperature side Y via a superconducting cable, the terminal structure of Example 1 is constructed between room temperature side X and the superconducting cable, and the superconducting cable and room temperature side Y In the meantime, the terminal structure of Example 2 is constructed. At this time, if power is transmitted from the room temperature side X, the current flows separately to each conductor part on the room temperature side, so that the current flowing per conductor part can be reduced. And in a superconducting cable part, since the electric current which flows into each conductor part is collected in a branch connection part, a large current can be sent. From the superconducting cable toward the room temperature side Y, the voltage applied to the cable is increased by the power changing device, so that the current value is reduced, and a small current can flow through the conductor portion on the room temperature side Y.

  The terminal structure of the present invention is suitable for forming a terminal portion of a superconducting cable, and can be used for either a single-phase superconducting cable or a multiphase superconducting cable. Further, it can be used for either an AC line or a DC line.

(A) is a schematic configuration diagram showing the terminal structure of the superconducting cable of the present invention, showing an example in which a current flowing through the cable is shunted and supplied to a plurality of conductor parts, (B) is an outline of a branch connection part It is the elements on larger scale which show a structure. It is a schematic block diagram which shows the terminal structure of this invention superconducting cable, and shows the example which provides the electric power change apparatus which changes a voltage between the edge part and conductor part of the cable. It is a schematic block diagram which shows the terminal structure of this invention superconducting cable, and shows the example which equips an intermediate temperature tank with an electric power change apparatus. In the terminal structure of the superconducting cable of this invention, it is a schematic block diagram which shows the connection part of the edge part and conductor part of a superconducting cable. It is a cross-sectional block diagram which shows the outline of a three-core package type three-phase superconducting cable. It is a schematic block diagram which shows the terminal structure of the conventional superconducting cable.

Explanation of symbols

10, 20, 40 Conductor 11, 21, 41 Bushing 11a, 21a Upper shield
12,22 Cryogenic tank 12a, 22a Refrigerant 13a, 23a Heat insulation layer 13,23 Vacuum container
14,24 Steel pipe 14a Insulating fluid 15 Branch connection 15a Block
15b Connecting part 15c, 15d Mounting part 25 to 27 Power change device 30 Medium temperature chamber
30a Gas refrigerant layer 31 Refrigerant tank 31a Liquid refrigerant layer 32 Copper component
33 Electrical insulation layer
100 Superconducting cable 101 Heat insulation pipe 101a Outer pipe 101b Inner pipe
102 Cable core 103 Space 104 Anticorrosion layer
110a Conductor 110b Bushing 111 Cryogenic bath 112 Vacuum vessel
112a Heat insulation layer 113 Steel pipe 113a Insulating fluid 114 Lead
114a Epoxy unit 114b Insulation material 115 Joint
116 Reed refrigerant tank 116a Liquid refrigerant 117 Lead vacuum container
118 Fixing jig
200 Former 201 Superconducting conductor 202 Electrical insulation layer 203 Shield layer
204 Protective layer

Claims (9)

A superconducting cable terminal structure having a superconducting conductor cooled by a refrigerant,
A plurality of conductor portions electrically connected to the ends of the superconducting conductor;
A plurality of bushings each including a conductor portion for each conductor portion;
A terminal structure of a superconducting cable, comprising a low-temperature tank in which a connection side of the conductor portion to the superconducting conductor is housed. A superconducting cable terminal structure having a superconducting conductor cooled by a refrigerant,
A conductor portion electrically connected to an end portion of the superconducting conductor;
A bushing incorporating the conductor portion;
A power change device that is arranged between the end portion of the superconducting conductor and the conductor portion, and that changes the voltage applied to the conductor portion, or the voltage applied to the superconducting cable to a voltage having a different magnitude;
A terminal structure of a superconducting cable, comprising a connection side of the conductor portion with a power change device and a low-temperature bath in which the power change device is accommodated. A superconducting cable is a direct current transmission cable,
3. The superconducting cable according to claim 2, wherein the power changing device changes an AC voltage or a DC voltage applied to the conductor portion, or a DC voltage applied to the superconducting cable into a DC voltage having a different magnitude. Terminal structure. Comprising a branch connecting portion for connecting a plurality of conductor portions and the end portion of the superconducting conductor;
4. The terminal structure of a superconducting cable according to claim 2, wherein the power changing device is disposed between an end portion of the superconducting conductor and the branch connection portion.   5. The terminal structure of a superconducting cable according to claim 2, wherein the power change device is a superconducting device formed of a superconducting material.   5. The terminal structure of a superconducting cable according to claim 2, wherein the power change device is a normal conductive device formed of a normal conductive material.   7. The terminal structure of a superconducting cable according to any one of claims 2 to 6, wherein the low temperature bath is controlled in a temperature range in which the end portion of the superconducting cable is cooled to a temperature range that is higher than a refrigerant temperature that is less than room temperature.   A superconducting cable line comprising the terminal structure of the superconducting cable according to any one of claims 1 to 7.   A superconducting cable line comprising the terminal structure according to claim 1 at one end of the superconducting cable and the terminal structure according to claim 2 at the other end.

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