CN1989575A - Superconducting cable line - Google Patents

Abstract

The invention discloses a superconducting cable, which comprises a heat insulating pipe (2) for liquid hydrogen (1), a superconducting cable ( 10) and heat exchange means for performing heat exchange between the liquid hydrogen (1) and the cable (10). Since the superconducting cable (10) includes the cable core inside the heat insulating tube for the cable and is housed in the heat insulating tube for the fluid (2), the outer periphery of the cable (10) is exposed to a low temperature environment, and The superconducting cable is formed as a double thermal insulation structure in relation to the thermal insulation tube (2). Therefore, since the heat intruded into the superconducting cable (10) is reduced and the coolant is cooled with liquid hydrogen (1), the energy required for cooling the coolant can be reduced.

Description

Superconducting cable lines

technical field

The invention relates to a power circuit comprising a superconducting cable. More specifically, the present invention relates to a superconducting cable line that reduces the intrusion of heat into the superconducting cable, thereby reducing the energy used to cool the coolant used in the cable, and the cable as a whole , which can increase the coefficient of performance (COP).

Background technique

A superconducting cable comprising a thermally insulating tube housing a cable core with a superconductor layer is generally known. Such superconducting cables include, for example, a single-core cable having a thermal insulation tube housing one cable core or a three-core cable housing three cable cores in a bundle. Fig. 7 is a cross-sectional view of a three-core superconducting cable for three-phase alternating current. FIG. 8 is a cross-sectional view of each cable core 102 . This superconducting cable 100 has a structure in which three strands of cables 102 are accommodated in one heat insulating tube 101 . The heat insulation pipe 101 is structured such that a heat insulation material (not shown) is provided between double pipes formed of an outer pipe 101a and an inner pipe 101b, and air between the pipes 101a, 101b is exhausted. Each cable core 102 comprises, starting from its central part, a sizing tube 200 , a superconductor layer 201 , an electrical insulation layer 202 , a superconducting shield 203 and a protective layer 204 . The space 103 surrounded by the inner tube 101b and each cable core 102 serves as a passage for a coolant such as liquid nitrogen. The superconducting state of the superconducting layer 201 and the superconducting shielding layer 203 of the cable core 102 is maintained by coolant cooling. On the outer periphery of the heat insulating pipe 101, a corrosion protection layer 104 is provided.

Superconducting cables must be continuously cooled with a coolant such as liquid nitrogen to maintain the superconducting state of the superconducting layer and the superconducting shield. Therefore, lines using superconducting cables usually include cooling systems for coolants. Cyclic cooling is performed with such a system in which the coolant sprayed from the cable is cooled and the cooled coolant flows into the cable again.

By using the cooling system to cool the coolant to an appropriate temperature, and by sufficiently reducing the heat generated by the coolant through the passage of current or the temperature increase of the coolant caused by heat intruding from the outside such as the environment, the superconducting cable can maintain the superconductor layer and the superconducting cable. The superconducting state of the conducting shield. However, where the coolant is liquid nitrogen, the energy required to cool the coolant to overcome this generated or intrusive heat becomes at least 10 times higher than the energy required to cool the cable by the coolant. Therefore, when the superconducting cable line including the cooling system for the coolant is considered as a whole, the coefficient of performance (COP) becomes 0.1 or lower. This low COP is one of the reasons for reducing the application effect of superconducting devices such as superconducting cables. Therefore, each of Japanese Patent Application Publication No. JP2002-130851 (Patent Document 1) and Japanese Patent Application Publication No. JP10-092627 (Patent Document 2) proposes to use the cold heat of liquefied natural gas (LNG) to cool super Coolant for wire coils.

On the other hand, with the development of fuel cell vehicles, it is planned to establish hydrogen stations in many places in Japan to store compressed hydrogen gas or liquid hydrogen for supplying fuel cell vehicles. The hydrogen station includes, for example, a tank for storing liquid hydrogen produced at a factory and transported or produced at a hydrogen station, and a cooling system for liquefying vaporized hydrogen to maintain it in a liquid state. Although hydrogen gas can be maintained in a liquid state by cooling to an appropriate temperature using a cooling system, since liquid hydrogen has a low-temperature boiling point of about 20K, which is significantly different from normal ambient temperature, heat intruded from the outside becomes large. Therefore, a large amount of energy is required to cool the liquid hydrogen to reduce the temperature increase due to thermal intrusion.

Patent Document 1: Japanese Patent Application Publication No. JP2002-130851

Patent Document 2: Japanese Patent Application Publication No. JP10-092627

Contents of the invention

Each of the above-mentioned Patent Documents 1 and 2 only discloses the use of cold heat of LNG for cooling a coolant of a superconducting coil, and does not consider reducing heat intruded from the outside. On the other hand, at liquid hydrogen stations, it is also desirable to be able to reduce the energy used to cool the hydrogen, as mentioned above.

Therefore, the main object of the present invention is to provide a superconducting cable line which can reduce the heat intrusion into the superconducting cable and can reduce the energy for cooling the superconducting cable and the energy for cooling liquid hydrogen as a whole.

The present invention achieves the above objects by arranging a superconducting cable in a thermally insulating pipe for transporting liquid hydrogen and exchanging heat between the liquid hydrogen and the coolant of the cable. That is to say, the superconducting cable line of the present invention includes a heat-insulating pipe for fluid for transporting liquid hydrogen and a superconducting cable, and the superconducting cable is placed in the heat-insulating pipe for fluid to use a temperature higher than The coolant of liquid hydrogen cools the superconducting part. Also included are heat exchange means for cooling the liquid hydrogen and elevating the temperature of the coolant of the superconducting cable cooled by the liquid hydrogen. The present invention will be described in more detail below.

The structure of the superconducting cable used in the present invention includes a superconducting part formed of a superconducting material, and a thermal insulating tube (hereinafter referred to as a thermal insulating tube for the cable) that accommodates the superconducting part and is filled with Coolant for cooling the superconducting part. The superconducting portion may comprise a superconductor layer for passing a power supply current and an outer superconducting layer for passing a current in an opposite direction of approximately the same value as the superconductor layer. The superconducting portion is usually formed in the cable core. Therefore, a superconducting cable can be constructed by enclosing a superconducting cable including a superconducting layer in a heat insulating tube for the cable. The more specific structure of the cable core includes a sizing tube, a superconductor layer, an electrical insulation layer, an outer superconductor layer and a protective layer starting from its central part. Thermal insulation tubes for cables can accommodate one cable core (single core (one core)) or multiple cable cores (multiple cores). More specifically, for example, when the line of the present invention is used for three-phase AC transmission, a three-core cable having a heat insulating tube for the cable for accommodating three-strand cores can be used, and when the line of the present invention is used for single-phase For AC transmission, a single-core cable having a heat insulating tube for the cable accommodating one core may be used. For example, when the line of the present invention is used for DC transmission (unipolar transmission), a single-core cable with a heat insulating tube for the cable for accommodating one core can be used, and when the line of the present invention is used for DC transmission (bipolar transmission). For pole transmission), a two-core cable or a three-core cable with a heat insulating tube for the cable accommodating two or three cores can be used. As described above, the superconducting cable line of the present invention can be used for DC transmission or AC transmission.

For example, the superconductor layer can be formed by helically winding a tape-shaped wire comprising a plurality of wires made of a Bi oxide-based superconducting material, more specifically, a Bi2223-based superconducting material. A plurality of wires are provided in a matrix such as a silver sheath. The superconductor layer may have a single-layer or multi-layer structure. When the superconductor layer has a multilayer structure, an interlayer insulating layer may be provided therein. The interlaminar insulating layer may be formed by winding insulating paper such as kraft paper or semi-synthetic insulating paper such as PPLP (trademark of Sumitomo Electric Industries, Ltd.). The superconductor layer is formed by winding a wire made of superconducting material around the sizing tube. The sizing tube may be a solid or hollow body formed of a metallic material such as copper or aluminum, and have a structure such as bundles of copper wires. Insulated copper conductors can be used. The sizing tube serves as a shape-maintaining member for the superconductor layer. A bedding layer may be inserted between the sizing tube and the superconductor layer. The cushion layer avoids direct metal contact between the sizing tube and the superconducting wire, thereby preventing the superconducting wire from being damaged. In particular, when the sizing pipe is in a twisted structure, the cushion also has the function of smoothing the surface of the sizing pipe. Insulating paper or carbon paper can be suitably used as the specified material for the underlayment.

The electrical insulating layer may be formed by winding a semi-synthetic insulating paper such as PPLP (trade mark) or insulating paper such as kraft paper on the superconductor layer. The semiconductor layer may be formed by carbon paper or the like on at least one of the inner periphery or the outer periphery of the electrical insulating layer, that is, formed between the superconductor layer and the electrical insulating layer and between the electrical insulating layer and the outer superconducting layer (described below). between. By forming an inner semiconducting layer (as the former), or forming an outer semiconducting layer (as the latter), the adhesion between the superconductor layer and the electrically insulating layer or between the electrically insulating layer and the outer superconducting layer is increased, thereby suppressing partial discharge caused by etc. resulting in deterioration.

When the circuit of the present invention is used for DC transmission, the electrical insulating layer can be subjected to p grading to obtain low resistivity on the inner peripheral side of the electrical insulating layer and high resistivity on the outer peripheral side, so that in its diameter direction (thickness direction) ) on the DC electric field distribution becomes smooth. As mentioned above, "ρ grading" means that the resistivity in the thickness direction of the electrical insulating layer changes in a stepwise manner, which can smooth the distribution of the DC electric field in the entire thickness direction of the electrical insulating layer and can reduce the electrical resistance. The thickness of the insulating layer. Although the number of layers having different resistivities is not specifically limited, two or three layers are actually used. In particular, when the thicknesses of the layers are equalized, the smoothness of the DC electric field distribution can be performed more effectively.

The ρ classification can be performed using insulating materials having different resistivities (ρ) from each other. When using insulating paper such as kraft paper, for example, the resistivity can be changed by changing the density of the kraft paper or adding dicyandiamide to the kraft paper. When using a composite paper formed of insulating paper and plastic film such as PPLP (trademark), the resistivity can be changed by changing the ratio k, or by changing the density, material, additive, etc. of the insulating paper, wherein the ratio k=(tp/ T)×100, which is the ratio between the thickness tp of the plastic film and the thickness T of the entire composite paper. The value of the ratio k is preferably, for example, in the range of 40-90%. In general, the resistivity ρ increases as the ratio k increases.

In addition, the Imp. withstand voltage characteristic can be increased in addition to the DC withstand voltage characteristic when the electrical insulating layer has a high ε layer which is provided near the superconducting conductor and has a higher dielectric constant than the other part . The dielectric constant ε (20°C) is about 3.2-4.5 in general kraft paper, about 2.8 in composite paper with a ratio of 40%, about 2.6 in composite paper with a ratio of 60%, and about 2.6 in a ratio of 80% Composite paper is about 2.4. An electrical insulation layer constructed of composite paper using kraft paper with a high ratio k and high airtightness is particularly preferred because of the increased DC withstand voltage and Imp. withstand voltage.

In addition to the ρ classification described above, by constructing an electrical insulating layer whose dielectric constant ε increases toward the inner peripheral side and decreases toward the outer peripheral side, a cable suitable also for AC transmission is formed. "ε classification" is also performed over the entire area in the diameter direction of the electrical insulating layer. In addition, the superconducting cable subjected to the above-mentioned ρ classification has better DC characteristics, and can be suitably used as a DC transmission line. On the other hand, most current transmission lines are constructed for AC transmission. When a transmission system is converted from an AC system to a DC system, a case occurs in which AC transmission is performed instantaneously using a ρ-graded superconducting cable before conversion to DC transmission. For example, when a part of the cable of the transmission line is replaced by a ρ-graded superconducting cable, while the other part is still a cable for AC transmission, or the cable used for the AC transmission of the transmission line is replaced by a ρ-graded superconducting cable This can occur when the cable is replaced and the transmission device connected to the cable is still a device for AC. In this case, AC transmission is instantaneously performed using a ρ-graded superconducting cable, and then the system is finally converted to DC transmission. Therefore, superconducting cables can preferably be designed not only to have good DC characteristics, but also to take into account AC characteristics. When AC characteristics are also considered, a superconducting cable having good pulse characteristics such as surge can be constructed by constructing an electrical insulating layer whose dielectric constant ε increases toward the inner peripheral side and decreases toward the outer peripheral side. Then, when the above-mentioned transient period ends and DC transmission is performed, the ρ-graded superconducting cable used during the transient period can be continuously used as a DC cable. That is, using a superconducting cable that is ε-graded in addition to ρ-classified is applicable to each of DC transmission and AC transmission, and is also suitable as a line for AC and DC transmission.

The PPLP (trademark) described above generally has higher p values and lower ε values as the ratio k increases. Therefore, when the electrical insulating layer is constituted with PPLP (trademark) in which the ratio k increases toward the outer peripheral side of the electrical insulating layer, ρ can be increased toward the outer peripheral side, and at the same time, ε can be decreased toward the outer peripheral side.

Kraft paper, on the other hand, generally has higher p values and higher ε values as air tightness increases. Therefore, it is difficult to construct an electrical insulating layer in which the p value increases toward the outer peripheral side and the ε value decreases toward the outer peripheral side using only kraft paper. Therefore, kraft paper and composite paper can be used to form an electrical insulation layer. As an example, a kraft paper layer may be formed on the inner peripheral side of the electrical insulating layer, and a PPLP layer may be formed on the outer side thereof, so that the kraft paper has a resistivity ρ value lower than that of the PPLP layer, and a kraft paper has a dielectric constant ε value lower than that of the PPLP layer. Higher than the dielectric constant ε value of PPLP.

An outer superconducting layer is provided on the outer periphery of the aforementioned electrically insulating layer. The outer superconducting layer is formed of a superconducting material, such as the material used to form superconducting layers. The same superconducting material as that used to form the superconductor layer can be used in the outer superconducting layer. When the superconducting cable line of the invention is used for DC transmission, the outer superconducting layer can be used, for example, as a return conductor in unipolar transmission and as a neutral conductor layer in bipolar transmission. In particular, when performing bipolar transport, the outer superconducting layer can be used to flow an unbalanced current when an imbalance is created between the positive and negative poles. In addition, when one electrode is abnormal and bipolar transmission changes to unipolar transmission, the outer superconducting layer can be used as a return wire for passing a current equivalent to the transport current flowing through the superconducting layer. When the superconducting cable line of the present invention is used for AC transmission, the outer superconducting layer can be used as a shield for passing a shielding current induced by the current flowing through the superconducting layer. A protective layer also for insulation is provided on the outer periphery of the outer superconducting layer.

The thermal insulating tube for accommodating a cable having the above structure may have a double-layered tube structure formed by an inner tube and an outer tube, and a thermal insulating material is provided between the tubes, and a vacuum is applied to obtain a vacuum for forming a vacuum. The specified degree of vacuum required for insulating structures. The space inside the inner tube is used as a coolant channel, which is filled with a coolant such as liquid nitrogen for cooling the cable core, especially the superconductor layer and the outer superconductor layer. Likewise, the thermal insulation tube for the cable is preferably a flexible corrugated tube. In particular, heat insulating pipes for cables are preferably formed of metallic materials such as high-strength stainless steel.

The temperature of the coolant filling the thermal insulation tube for cables (which is used in the present invention) is higher than the temperature of the liquid hydrogen conveyed inside the thermal insulation tube for fluid. For example, liquid nitrogen is used as a coolant. Since the temperature of liquid hydrogen is lower than that of the coolant of the superconducting cable, the coolant of the superconducting cable contained in the heat insulating tube for fluid can be cooled with liquid hydrogen. Therefore, in the circuit of the present invention, a temperature capable of maintaining the superconducting state of the superconducting portion can be set without providing a separate cooling system for the coolant for cooling the coolant of the superconducting cable.

In the circuit of the present invention, a superconducting cable with a thermally insulating tube for the cable is housed in a thermally insulating tube for fluid, which is used to transport liquid hydrogen. With this structure, the superconducting cable housed in the heat insulating tube for fluid has an environment around the cable whose temperature is lower than normal temperature, more specifically, a low temperature environment of about 20K which is the temperature of liquid hydrogen, and The temperature difference between the inside and the outside of the thermally insulating tube for the cable is thereby reduced to less than 200K compared to the case of placement in the environment. In particular, when liquid nitrogen is used as a cable coolant, the temperature difference between the inside and outside of the heat insulating tube for the cable becomes about 50K. In addition, a superconducting cable housed in a thermal insulation tube for fluid has a double-layer thermal insulation structure formed of a thermal insulation structure for liquid hydrogen and a thermal insulation structure for the cable itself. Therefore, since the line of the present invention has a small temperature difference between the inside and the outside of the thermal insulation tube for the cable, and the superconducting cable has the double-layer thermal insulation structure as described above, it is different from the superconducting cable placed in the environment Compared with the line, it can effectively reduce the heat intruded into the cable part from the outside.

A heat insulating pipe having a heat insulating property corresponding to liquid hydrogen conveyed therein can be used as a heat insulating pipe for fluid for accommodating a superconducting cable. As an example, it is possible to use a thermally insulating tube having a structure similar to that of a superconducting cable, that is, having a double-layered tube structure formed by an outer tube and an inner tube, including a thermal insulating material between the tubes and evacuating it . In this case, the space inside the inner tube becomes a delivery channel for liquid hydrogen.

For example, when forming a heat insulating pipe for fluid by welding a metal plate made of stainless steel, steel, etc., by arranging cables on the metal plate, bending the metal plate to cover the cables, and welding the edges of the metal plate, Superconducting cables can be housed in thermally insulated tubes for fluids. When a metal pipe made of stainless steel, steel, or the like is used as the heat insulating pipe for fluid, by inserting a superconducting cable into the pipe, the cable can be housed in the heat insulating pipe for fluid. In this case, a skidwire (sliding wire) may be helically wound around the cable, thereby improving the insertion characteristics of the superconducting cable. In particular, when the heat insulating tube for the cable is a corrugated tube having protrusions and dents, by winding the slide wire with a pitch larger than that between the protrusions and dents of the corrugated tube (long pitch (1ong pitch)), Thereby preventing the slide wire from entering the recessed portion of the bellows, and thereby placing the slide wire over the protrusions and depressions of the bellows to prevent the outer periphery of the bellows from coming into direct contact with the heat insulating tube for the fluid, that is, to A point contact is obtained between the slide wire wound around the bellows and the heat insulating tube for the fluid, so that insertion characteristics can be improved. In addition, tension members and the like can be connected to the superconducting cable so that it can be pulled into a thermally insulated tube for the fluid.

The superconducting cable housed in the thermally insulating tube for fluid may be arranged to be in contact with or not to be in contact with liquid hydrogen conveyed inside the thermally insulating tube for fluid. In the former case, the superconducting cables can be submerged in liquid hydrogen. In this case, since the entire periphery of the superconducting cable is in contact with low-temperature liquid hydrogen, heat intruded into the cable from the outside can be effectively reduced, and the cable coolant can be sufficiently cooled by the liquid hydrogen.

On the other hand, when the superconducting cable is immersed in liquid hydrogen, for example, in the case where the superconducting cable is short-circuited to generate a spark, problems such as explosion of liquid hydrogen may occur. Thus, the area inside the thermally insulating tube for the fluid can be divided into a transport area for liquid hydrogen and an area for arranging the superconducting cable therein. As a delivery area, for example, a delivery pipe for liquid hydrogen may be provided separately inside a heat insulating pipe for fluid, and a superconducting cable may be provided longitudinally along the delivery pipe. In this case, when the heat exchanger partition with high thermal conductivity is placed in the space not occupied by the delivery pipe and the superconducting cable inside the thermal insulation pipe for the fluid, the liquid can be transported through the heat exchanger partition. The heat of the hydrogen is efficiently conducted to the cable and thereby effectively cools the cable. Such heat exchanger partitions can be formed, for example, from a material with high thermal conductivity, such as aluminum. More specifically, heat exchanger separators may be formed by winding aluminum foil.

In the present invention, a superconducting cable using a coolant whose temperature is higher than that of liquid hydrogen can be used, and since the cable is housed in a thermally insulated tube for fluid (which is used to transport liquid hydrogen), the liquid hydrogen can be used to Coolant cools. However, the coolant of the superconducting cable can be supercooled by liquid hydrogen, and solidification of the coolant can occur. Therefore, it is necessary to raise the temperature of the supercooled coolant of the superconducting cable housed in the heat insulating tube for fluid within a range capable of maintaining the superconducting state. On the other hand, liquid hydrogen needs to be cooled to maintain a liquid state (liquefaction). Accordingly, the present invention includes heat exchange means for exchanging heat between liquid hydrogen and liquid nitrogen in order to cool the liquid hydrogen and raise the temperature of the coolant supercooled by the liquid hydrogen.

The heat exchanging device may have a structure comprising, for example, passages for circulating the heat exchanging medium, expansion valves for expanding the heat exchanging medium, compressors for compressing the heat exchanging medium, and for accommodating the passages, expansion valves and Thermally insulated casing of the compressor. The delivery line for the liquid hydrogen is arranged on a part of the channel which passes through the expansion valve in order to cool the liquid hydrogen with the expanded heat exchange medium, and the delivery line for the coolant of the cable is arranged on a part of the channel, This part of the channel passes through the compressor to raise the temperature of the coolant of the superconducting cable with the compressed heat exchange medium. The delivery pipeline for liquid hydrogen can, for example, be arranged to form a circulation path in which the liquid hydrogen sprayed from the heat insulation pipe for fluid flows into the heat insulation pipe for fluid again. Alternatively, a liquid tank storing liquid hydrogen may be connected to a thermally insulated pipe for fluid, and a transfer line may be provided to form a circulation path in which liquid hydrogen sprayed from the liquid tank flows into the liquid again. Can. A portion of this delivery line for liquid hydrogen may then be placed in contact with, or adjacent to, a portion of the passage of the heat exchange medium passing through the expansion valve. The delivery line for the coolant may be provided as a circulation path in which the coolant sprayed from the heat insulation pipe for cables flows into the heat insulation pipe for cables again. A portion of this delivery line for coolant may then be arranged in contact with, or in the vicinity of, a portion of the passage of the heat exchange medium passing through the compressor. In the heat exchange device, the temperature of the coolant is raised within a temperature range capable of maintaining the superconducting state of the superconducting portion. Due to the inclusion of heat exchange means for cooling the liquid hydrogen and heating the coolant of the cable at the same time, the present invention can satisfy both the requirement of raising the temperature of the coolant of the superconducting cable and the requirement of cooling the liquid hydrogen.

It is to be noted that, in the present invention, since the heat intruded into the superconducting cable housed in the heat insulating tube for fluid can be reduced as described above, the thermal insulation structure of the thermal insulating tube for the cable can be simplified, and also That is, the level of thermal insulation performance of heat intruding into the cable from the outside can be reduced. When the thermal insulation tube used for the cable has a double-layer tube structure formed by the outer tube and the inner tube, for example, by changing the degree of vacuum between the outer tube and the inner tube, changing the thermal insulation provided between the outer tube and the inner tube The number of windings of the material or the material of the thermal insulation material is changed to change the thermal insulation performance, wherein the thermal insulation material is arranged between the tubes and vacuumized.

In addition, in the superconducting cable line of the present invention, the entire length in the longitudinal direction of the superconducting cable forming the line may be housed in the heat insulating pipe for fluid, or only a part of the cable may be housed in the heat insulating pipe for fluid . In view of reducing intrusive heat, it is preferred to enclose the entire length of the superconducting cable in a thermally insulating tube for the fluid.

For example, the superconducting cable line of the present invention can be constructed in such a way that the superconducting cable is packed into a pipeline with a thermal insulation structure, wherein the pipeline is used to connect a hydrogen plant for producing liquid hydrogen with a storage facility for liquid hydrogen. The hydrogen station is connected, or the superconducting cable is installed in the heat insulation pipe used to transport liquid hydrogen at the hydrogen station, and a heat exchange device is installed near the hydrogen station. The circuit of the present invention can be used to supply electric power to various electric devices used in the hydrogen station, or to absorb required electric power from pipelines to supply electric power to various places.

As described above, the superconducting cable line of the present invention can be used for DC transmission or AC transmission. For example in the case of three-phase AC transmission, the cable can be formed as a three-core superconducting cable, wherein the superconducting layer of each core is used for the transmission of each phase, and the outer superconducting layer of each core is used as a shielding layer. For single-phase AC transmission, the cable can be formed as a single-core superconducting cable, where a superconductor layer contained in the core can be used for phase transmission and an outer superconducting layer can be used as a shield. When performing unipolar DC transmission, the cable can be formed as a single core superconducting cable, where the superconducting layer of the core can be used as a "go conductor" and the outer superconducting layer can be used as a return conductor. When performing bipolar DC transmission, the cable can be formed as a two-core superconducting cable, where the superconducting layer of one core can be used for positive pole transmission and the superconducting layer of the other core can be used for negative pole transmission, and the outer superconducting layer of each core can be used as a neutral conductor.

In addition, the superconducting cable of the present invention can also be used as a line for DC and AC transmission by using a superconducting cable comprising a cable core having a ρ-classified and ε-classified electrical insulating layer as described above. In this case, not only the superconducting cable but also the terminal structure, which is formed in the end of the line for connecting the superconducting cable to the conductive part on the normal temperature side, is preferably configured to be suitable for DC and AC transmission (common conductive cable, connected to the lead of a normal conductive cable). A representative structure of the terminal structure includes a cable core end extending from the end of the superconducting cable, a drawn conductor part connected to the conduction part on the normal temperature side, a connection part electrically connected to the cable core end using the drawn conductor part, and a termination. A junction box, wherein the terminating junction box is used to accommodate the cable core end, the end of the withdrawn conductor part on the side connected to the cable core, and the connection part. The terminating junction box generally includes a coolant pool for cooling the cable core end or the end of the withdrawn conductor section, and a vacuum insulation pool arranged on the outer periphery of the coolant pool. In this terminal structure, the cross-sectional area of the conductor of the drawn conductor portion is variable as needed because the amount of current flowing through the drawn conductor portion differs in AC transmission and DC transmission. Therefore, an appropriate structure of the terminal structure for AC and DC transmission has a conductor cross-sectional area of the drawn conductor portion that can be changed according to the load. Such a terminal structure may have, for example, a structure in which the drawn-out conductor portion is divided into a low-temperature-side conductor portion connected to the end portion of the cable core and a normal-temperature-side conductor portion disposed on the side of the conduction portion on the normal-temperature side, wherein the low-temperature The side conductor part and the normal temperature side conductor part are detachable from each other. In addition, a plurality of such withdrawable conductor parts are included to allow the cross-sectional area of the conductors of the entire withdrawn conductor part to be changed according to the number of joints between the low temperature side conductor part and the normal temperature side conductor part. The cross-sectional areas of the conductors of the respective drawn conductor portions may be the same as or different from each other. The superconducting cable line of the present invention including such a terminal structure can be easily changed from DC transmission to AC transmission, or from AC transmission to DC transmission, by performing attachment and detachment of the drawn conductor portion. In addition, since the cross-sectional area of the conductor drawn from the conductor portion can be changed as described above, the cross-sectional area of the conductor can also be appropriately changed when the amount of supplied power is changed during AC transmission or DC transmission.

In the superconducting cable line having the above structure according to the present invention, the superconducting cable is housed in the heat insulating pipe for transporting liquid hydrogen to reduce the temperature difference between the inside and outside of the heat insulating pipe for the cable, and the cable The thermal insulation structure is formed as a double-layer thermal insulation structure, which includes a thermal insulation tube for the cable and a thermal insulation tube for the fluid, so as to effectively reduce the heat intruding into the cable. In addition, in the circuit of the present invention, the coolant of the superconducting cable can be cooled by liquid hydrogen conveyed in the heat insulating tube for the fluid. With the reduced heat intrusion as described above and cooling of the coolant with said fluid, the circuit of the invention substantially reduces or substantially eliminates the energy required for cooling the coolant for the cable. In particular, a cooling system for cooling the coolant of the superconducting cable is not required, or even if a cooling system is provided, the level of cooling performance can be lowered compared with conventional systems.

Therefore, as described above, when the coolant cooling of the superconducting cable is also taken into consideration, the coefficient of performance of the superconducting cable having the above-mentioned structure of the present invention is increased compared with the conventional line, because the above-mentioned By reducing the heat intrusion into the cable as described above, the energy required for cooling the coolant can be substantially reduced. In particular, the reduction of heat intrusion is extremely effective for increasing the coefficient of performance when the circuit of the present invention is used as a circuit for DC transmission, wherein, in the circuit of the present invention, the current path generates little heat (conductor loss), because In this case heat intrusion becomes the main cause of energy loss.

In addition, in the circuit of the present invention, the energy for cooling the liquid hydrogen is also greatly reduced by using the coolant of the superconducting cable as a heat exchange object for cooling the liquid hydrogen. Therefore, the present invention can completely reduce the energy required for cooling the coolant of the superconducting cable and the energy required for cooling liquid hydrogen, thereby substantially increasing the coefficient of performance.

Furthermore, when a superconducting cable including a cable core having a ρ-graded electric insulating layer is used in the line of the present invention, the line can have good DC withstand voltage characteristics and be suitable for DC transmission. In addition, in the circuit of the present invention, using a superconducting cable including a cable core having an electric insulation layer that is p-graded and provided with a high ε value at a portion close to the superconductor layer, in addition to the above-mentioned increase in the DC withstand voltage characteristic, Imp. withstand voltage characteristics can also be increased. In particular, when the electrical insulating layer is formed so that the ε value increases toward the inner peripheral side and the ε value decreases toward the outer peripheral side, the wiring of the present invention can also have good AC electrical characteristics. Therefore, the superconducting cable of the present invention is applicable to each of DC transmission and AC transmission. In addition, a superconducting cable including a cable core having a ρ-classified and ε-classified electrical insulating layer is used as the line of the present invention and the terminal structure formed at the end of the line has a conductor whose cross-sectional area is variable. When having a structure, the circuit of the present invention is applicable to a transient period in which the transmission system is changed from an AC system to a DC system, wherein the extraction conductor portion is provided between the superconducting cable and the conduction portion on the normal temperature side.

Description of drawings

Fig. 1 is a schematic cross-sectional view of the structure of a superconducting cable line of the present invention;

2 is a schematic cross-sectional view of a part of the structure near the superconducting cable in the superconducting cable circuit of the present invention;

Fig. 3 is a schematic view of the structure in which the superconducting cable line of the present invention is constructed;

Fig. 4 is a schematic diagram of the structure of the superconducting cable line of the present invention, wherein the structure of the superconducting cable line includes a transport pipe for liquid hydrogen, a superconducting cable, and a heat exchanger insulation inside the heat insulation pipe for fluid plate, which is a schematic cross-sectional view of a part of the structure near the cable;

5 is a schematic diagram of the construction of a terminal structure formed in the end of the superconducting cable of the present invention using a three-core type superconducting cable in the case of an AC transmission line;

6 is a schematic diagram of the construction of a terminal structure formed in the end of the superconducting cable of the present invention using a three-core type superconducting cable in the case of a DC transmission line;

7 is a cross-sectional view of a three-core type superconducting cable for three-phase AC transmission;

Fig. 8 is a cross-sectional view of each cable core.

Explanation of reference signs

1: liquid hydrogen, 2: thermal insulation tube for fluid, 2a: outer tube, 2b: inner tube, 3: delivery tube, 4: heat exchanger separator, 10: superconducting cable, 11: for cable Thermal insulation tube, 11a: outer tube, 11b: inner tube, 12: cable core, 13: space, 14: superconductor layer, 15: outer superconductor layer, 16: delivery pipeline, 20: hydrogen station, 21: tank, 22: Conveying pipeline, 30: Heat exchange device, 31: Passage, 32: Expansion valve, 33: Compressor, 34: Thermal insulation casing, 40: Pull out conductor part, 41: Low temperature side conductor part, 41a: Low temperature side seal Parts, 42: Normal temperature side conductor part, 42a: Normal temperature side sealing part, 43: Guide part, 44: Ground wire, 50: Termination junction box, 51, 52: Coolant pool, 53: Vacuum insulation pool, 53a: Possible Extension part, 60: insulating sleeve, 61: extracted conductor part, 62: porcelain tube, 63: epoxy unit, 70: short circuit part, 100: superconducting cable for three-phase AC transmission, 101: thermal insulation tube, 101a: outer tube, 101b: inner tube, 102: cable core, 103: space, 104: anticorrosion layer, 200: sizing tube, 201: superconductor layer, 202: electrical insulation layer, 203: superconducting shielding layer, 204: The protective layer.

Detailed ways

Embodiments of the present invention will now be described

Example 1

Fig. 1 is a schematic cross-sectional view of the structure of a superconducting cable line of the present invention. Fig. 2 is a schematic cross-sectional view of the structure of a portion near the superconducting cable in the superconducting cable of the present invention. Fig. 3 is a schematic diagram of a structure in which the conductive cabling of the present invention is constructed. The same characters in the drawings indicate the same parts. The superconducting cable of the present invention includes a heat insulating pipe 2 for fluid used to transport liquid hydrogen 1, a superconducting cable 10 housed in the heat insulating pipe 2 for fluid, and a cable for regulating the temperature of liquid hydrogen 1 The temperature of the coolant in the heat exchange device 30.

The superconducting cable 10 used in this example has a structure in which three cable cores 12 are twisted and housed in a heat insulating tube 11 for the cable, and its structure is roughly the same as that of the superconducting cable shown in FIG. The structure is similar. Each cable core 12 comprises, starting from the central part, a sizing tube, a superconductor layer, an electrical insulation layer, an outer superconductor layer and a protective layer. Both the superconductor layer and the outer superconductor layer were formed of Bi2223-based superconducting tape lines (Ag-Mn sheathed lines). The superconducting layer and the outer superconducting layer are formed by winding a superconducting tape line on the outer periphery of the sizing tube and the outer periphery of the electrical insulating layer, respectively. Multiple stranded copper wires can be used as the sizing tube. A cushion layer is formed between the sizing tube and the superconductor layer using insulating paper. The electrical insulating layer was constructed by winding semi-synthetic insulating paper (PPLP: trademark of Sumitomo Electric Industries, Ltd.) on the outer periphery of the superconductor layer. The protective layer is formed by wrapping kraft paper around the outer perimeter of the outer superconducting layer. The inner semiconducting layer and the outer semiconducting layer may be provided on the inner peripheral side and the outer peripheral side (under the outer superconducting layer) of the electrical insulating layer, respectively. These three cable cores 12 are prepared, loosely stranded to allow for thermal shrinkage, and housed within a thermally insulating tube 11 for the cable. In this example, a SUS corrugated pipe is used to form a heat insulating pipe 11 for electric cables, in which a heat insulating material (not shown) having a multilayer structure is provided between a double pipe formed by an outer pipe 11a and an inner pipe 11b space, and the air between the outer pipe 11a and the inner pipe 11b is drawn out, thereby obtaining a prescribed degree of vacuum to form a vacuum multilayer insulation structure. The space 13 closed by the inner periphery of the inner tube 11b and the outer periphery of the three-core cable 12 becomes a passage for the coolant. A coolant for cooling the superconductor layer and the outer superconductor layer is circulated in this channel by a pump or the like. In this example, liquid nitrogen (approximately 77K) was used as the coolant. The pipe line 16 is connected to the heat insulating pipe 11 for the cable of the superconducting cable 10 to perform circulation delivery of coolant, wherein, for example, the coolant is sprayed from the heat insulating pipe 11 to one side of the heat exchanging device 30, and the The coolant flows into the heat insulating tube 11 from one side of the heat exchanging device 30 . A pump (not shown) is provided on a part of the piping 16 to circulate the coolant.

The superconducting cable 10 having the above structure is housed in the heat insulating tube 2 for fluid. In this example, the heat insulating pipe 2 for fluid has a double pipe structure formed by an outer pipe 2a and an inner pipe 2b, wherein a heat insulating material (not shown) is provided between the pipes 2a, 2b, and the The air between the tubes is evacuated. A space surrounded by the inner periphery of the inner tube 2b and the outer periphery of the superconducting cable 10 becomes a delivery channel for the liquid hydrogen 1 . Each of the tubes 2a, 2b is a welded tube made of steel, and the superconducting cable 10 can be housed in the inner tube 2b by arranging the superconducting cable 10 on a steel plate forming the inner tube 2b and welding both edges of the steel plate. In this example, the superconducting cable 10 is set in the inner tube 2b while being immersed in liquid hydrogen. In this example, the thermally insulated pipes 2 for fluids constitute the pipeline for the transport of liquid hydrogen from a hydrogen plant (not shown) to the various hydrogen stations 20 . Each hydrogen station 20 includes a tank 21 for storing liquid hydrogen and a heat exchange device 30 for heat exchange between the liquid hydrogen 1 and the coolant of the superconducting cable 10 . The tank 21 is connected to the heat insulating pipe for fluid 2 and stores liquid hydrogen delivered through the heat insulating pipe for fluid 2 . In addition, the pipeline 22 is connected to the tank 21 to perform circulation delivery of liquid hydrogen, wherein, for example, the liquid hydrogen is sprayed from the tank 21 to the side of the heat exchanging device 30 , and then the liquid hydrogen flows from the heat exchanging device 30 into the tank 21 . A pump (not shown) is included in a portion of line 22 to allow liquid hydrogen to be circulated.

In this example, the heat exchanging device 30 includes a channel 31 for circulating a heat exchanging medium such as helium, an expansion valve 32 for expanding the heat exchanging medium, a compressor 33 for compressing the expanded heat exchanging medium, and a heat exchanger for installing these elements. Insulating housing 34 . The pipeline 22 is arranged such that a part of the pipeline 22 for circulating liquid hydrogen is in contact with a part of the channel 31 passing through an expansion valve 32 to cool the liquid hydrogen with the expanding heat exchange medium. With this structure, the liquid hydrogen is cooled near the part of the pipe 22 that is in contact with the part of the passage 31 passing through the expansion valve 32 . Therefore, the liquid hydrogen injected from the tank 21 flows through the pipeline 22 , is cooled by the heat exchange device 30 and returns to the tank 21 . In addition, the pipeline 16 is provided so that a part of the pipeline 16 for circulating the coolant (liquid nitrogen) of the cable 10 is in contact with a part of the channel 31 passing through the compressor 33, so as to utilize The compressed heat exchange medium is used to increase the temperature of the coolant of the cable 10, wherein the coolant of the cable 10 is cooled with liquid hydrogen. With this structure, the temperature of the coolant rises near the part of the piping 16 that is in contact with the part of the passage 31 passing through the compressor 33 . Therefore, the coolant sprayed from the heat insulating pipe 11 for electric cables flows through the pipe line 16 , raises its temperature with the heat exchanging means 30 and returns to the heat insulating pipe 11 .

The superconducting cable housed in a thermal insulation tube for fluid has an outer periphery covered with cryogenic liquid hydrogen, and has a double-layer thermal insulation structure formed with a thermal insulation tube for the cable itself and a thermal insulation tube for liquid hydrogen. With such a structure, the wiring of the present invention can sufficiently reduce heat intruding into the superconducting cable from the outside. In addition, since the outer periphery of the superconducting cable is covered with cryogenic liquid hydrogen, the heat of the liquid hydrogen is conducted to the cable and cools the coolant of the cable. Therefore, a cooling system for cooling the coolant of the superconducting cable is not necessary. As a result, by constructing the superconducting cable line of the present invention, the energy required for cooling the coolant of the superconducting cable is reduced, and the coefficient of performance can be increased.

In addition, since the circuit of the present invention includes heat exchange means for heat exchange between the coolant of the superconducting cable and liquid hydrogen, thereby simultaneously performing heating of the coolant and cooling of the liquid hydrogen, using the heat exchange means, The temperature difference between heat exchange objects can be reduced, and the energy required for cooling the liquid hydrogen can also be reduced. In addition, with the heat exchange means included in the circuit of the invention, the heat associated with the cooling of liquid hydrogen can be used to increase the temperature of the coolant of the superconducting cable due to the heat contained in the fluid used Insulated tubes are overcooled. Therefore, the circuit of the present invention can adjust the temperature of the liquid hydrogen to an appropriate temperature and can also adjust the temperature of the cable coolant by using the heat exchange device configured for heat exchange between the liquid hydrogen and the coolant of the superconducting cable to the proper temperature. As a result, the energy required for cooling the coolant of the superconducting cable and the energy required for cooling liquid hydrogen can be reduced by constructing the superconducting cable line of the present invention.

It should be noted that although the structure shown in this example has the entire length in the longitudinal direction of the superconducting cable housed in the heat insulating tube for fluid, only a part of the cable may be housed in the heat insulating tube for fluid. In the circuit of the present invention, the effect of heat intrusion can be reduced, and when only a small part of the superconducting cable is contained in the heat insulating tube for the fluid, it is easy to adjust the temperature of the coolant of the superconducting cable with the heat exchange device. become difficult. Thus, in the circuit of the invention, a sufficient portion of the superconducting cable is enclosed in a thermally insulating tube for the fluid, allowing the temperature of the coolant of the superconducting cable to be adjusted by means of heat exchange.

Example 2

Although the superconducting cable is immersed in liquid hydrogen in the above-mentioned Example 1, the superconducting cable may be housed in a heat insulating pipe for fluid without being immersed in liquid hydrogen. As an example, a delivery channel for liquid hydrogen may be provided separately in a thermally insulating tube for fluid. Fig. 4 is a schematic diagram of the structure of the superconducting cable of the present invention, which includes a delivery tube for liquid hydrogen and a heat exchanger partition inside the thermal insulation tube for fluid, which is a schematic horizontal view of the structure near the cable Sectional view. The superconducting cable has a structure including a separate delivery tube 3 for delivery of liquid hydrogen in the inner tube 2b of the heat insulating tube 2 for fluid. The heat exchanger partition plate 4 having high thermal conductivity is provided in a space surrounded by the inner periphery of the inner pipe 2b, the outer periphery of the delivery pipe 3, and the outer periphery of the superconducting cable 10. With this structure, the superconducting cable 10 has a double thermal insulation structure formed by the thermal insulation tube 2 for the fluid and the thermal insulation tube 11 (see FIGS. 1, 2) of the cable 10 itself as in Example 1, and is composed of This reduces heat ingress into the cable from the outside. In addition, since the heat of the liquid hydrogen is conducted to the superconducting cable 10 via the heat exchanger partition 4 , the cable 10 can also be cooled by the liquid hydrogen 1 . In addition, since the delivery pipe 3 physically separates the superconducting cable 10 from the liquid hydrogen 1 , in the event of an accident such as a short circuit of the cable 10 or sparks, problems such as combustion of the liquid hydrogen 1 can be prevented. In this example, the heat exchanger diaphragms are formed by coiling aluminum.

The superconducting cable of the present invention shown in each of Examples 1 and 2 above can be used for either DC transmission or AC transmission. In the case of DC transmission, when using a superconducting cable comprising a cable core with an electrical insulating layer p-graded to have a low resistivity on the inner peripheral side and a high resistivity on the outer peripheral side , can make the DC electric field distribution in the thickness direction of the electrical insulating layer smooth, and increase the DC withstand voltage characteristic. Resistivity can be varied using PPLP (trade mark) with various ratios k. The resistivity tends to increase as the ratio k increases. In addition, when the high ε layer is provided in the electrical insulating layer near the superconductor layer, the Imp. withstand voltage characteristic is increased in addition to the DC withstand voltage characteristic. High ε layers may be formed, for example, with low-k ratio PPLP (trademark). In this case, the high ε layer also becomes a low ρ layer. In addition, a superconducting cable including a cable core having a ρ-graded electrical insulating layer and also formed such that the dielectric constant ε increases toward the inner peripheral side and toward the outer peripheral side has good AC characteristics. The dielectric constant ε decreases. Therefore, the circuit of the present invention using such a cable is also applicable to AC transmission. As an example, PPLP (trade mark) may be used to provide the electrically insulating layer, wherein the PPLP has various ratios k as indicated below, to have three different resistivities and permittivity. The three layers described below can be arranged in order from the inner peripheral side (X and Y are constants).

Low ρ layer: ratio k=60%, resistivity ρ(20°C)=X[Ω·cm], dielectric constant ε=Y

Intermediate ρ layer: ratio k=70%, resistivity ρ(20°C)=about 1.2X[Ω·cm], dielectric constant ε=about 0.95Y

High ρ layer: ratio k=80%, resistivity ρ(20°C)=about 1.4X[Ω·cm], dielectric constant ε=about 0.9Y

When performing unipolar transmission with the line of the present invention using ρ-classified and ε-classified superconducting cables, two of the three cable cores 12 (see FIG. 2 ) can be used as auxiliary cores, one The superconducting layer of the core can be used as a "go" wire, and the outer superconducting layer of the core can be used as a return wire. Alternatively, the superconducting layer of each core can be used as a "go" wire and the outer superconducting layer of each core can be used as a return wire to form a three-line unipolar transmission line. On the other hand, when performing bipolar transmission, one of the three cores can be used as an auxiliary core, the superconductor layer of one core can be used as a positive electrode line, the superconductor layer of the other core can be used as a negative electrode line, and the two-core The outer superconducting layer can be used as a neutral conductor layer.

The line of the present invention using a superconducting cable subjected to ρ-grading and ε-grading and including the terminal structure as described above can easily perform DC transmission such as unipolar transmission or bipolar transmission after AC transmission, or after DC transmission AC transmission. 5 and 6 are schematic diagrams of the construction of a terminal structure having a detachable extractable conductor portion formed at the end of the superconducting cable line of the present invention using a three-core type superconducting cable. FIG. 5 shows the case of an AC transmission line, and FIG. 6 shows the case of a DC transmission line. Although only two cable cores 12 are shown in Figures 5 and 6, there are actually three cores.

The terminal structure includes the end portion of the cable core 12 extending from the end portion of the superconducting cable 10, the extracted conductor portions 40, 61 connected to the conduction portion (not shown) at the normal temperature side, connecting the end portion of the cable core 12 with the extracted conductor part 40 is electrically connected and the end portion of the cable core 12 is electrically connected to the connection portion of the extracted conductor portion 61, and the end portion of the cable core 12 is installed, and the end of the extracted conductor portion 40, 61 on the side connected to the cable core The terminal junction box 50 of the part and the connection part. The termination junction box 50 includes a coolant pool 51 filled with cooling the superconductor layer 14, a coolant pool 52 for cooling the outer superconducting layer 15, and a vacuum insulating pool 53 provided on the outer peripheries of the coolant pools 51, 52. , wherein the superconductor layer 14 exposed by stepwise stripping the end of the cable core 12 is introduced into the coolant pool 51, and the outer superconducting layer 15 exposed by the stepwise stripping is introduced into the coolant pool 52. The drawn conductor part 61 is connected to the superconductor layer 14 via a joint (connection part), thereby allowing electric power transmission and reception between the superconducting cable 10 and the conduction part on the normal temperature side, wherein the drawn conductor part 61 is embedded in the conduction part provided on the normal temperature side and the insulating sleeve 60 between the superconductor layer 14. One side (ordinary temperature side) of the insulating sleeve 60 connected to the conduction portion on the normal temperature side protrudes from the vacuum insulating tank 53 and is housed in a porcelain tube 62 protruding from the vacuum insulating tank 53 .

On the other hand, the outer superconducting layer 15 is connected to the drawn conductor part 40 provided between the conduction part on the normal temperature side and the outer superconducting layer 15 via a short-circuit part 70 (connection part) described later, thereby allowing the superconducting cable Transmission and reception of power between 10 and the conduction part on the normal temperature side. The withdrawable conductor part 40 is formed with a low-temperature-side conductor part 41 connected to the short-circuit part 70 and a normal-temperature-side conductor part 42 provided on the normal-temperature side, which is detachable from the low-temperature-side conductor part 41 . In this example, the normal-temperature-side conductor portion 42 is formed in a rod shape with a predetermined cross-sectional area, and the low-temperature-side conductor portion 41 is formed in a cylindrical shape into which the rod-shaped normal-temperature-side conductor portion 42 can be fitted. When the normal temperature side conductor part 42 is inserted into the low temperature side conductor part 41, the conductor parts 41, 42 are both electrically connected to each other, allowing transmission and reception of electric power between the low temperature side and the normal temperature side. When the normal temperature side conductor part 42 is detached from the low temperature side conductor part 41, conduction between the conductor parts 41 and 42 is canceled. A plurality of such extracted conductor portions 40 are included in the terminal structure. The low-temperature-side conductor portion 41 is fixed in the coolant pool 52 , and one end thereof is electrically connected to the short-circuit portion 70 , and the other end enters the vacuum-insulated pool 53 . A low-temperature-side sealing portion 41a made of FRP is provided on the outer periphery of the fixing portion of the low-temperature-side conductor portion 41, thereby avoiding coolant leakage, short circuit of the coolant pool 52 and the conductor portion 41, and the like. The normal temperature side conductor part 42 is fixed to the vacuum insulation tank, and one end thereof is placed in the vacuum insulation tank 53 , and the other end is arranged so as to be exposed to the outside at normal temperature. The normal-temperature-side sealing portion 42a made of FRP is provided on the outer periphery of the fixed portion of the normal-temperature-side conductor portion 42, allowing heat intrusion to be reduced, and avoiding short circuiting of the vacuum insulation pool 53 and the conductor portion 42, and the like. In addition, an extensible portion 53a formed of a bellows is provided on the vacuum insulation pool 53 near the fixed portion of the normal temperature side conductor portion 42 to maintain the vacuum of the vacuum insulation pool 53 during attachment and detachment of the withdrawable conductor portion 40. state. It should be noted that the outer superconducting layer 15 of each of the three cores 12 is short-circuited in the short-circuit portion 70 . In addition, a lead portion 43 connected to an external device or the like or a ground wire 44 is attached to the normal temperature side end portion of the normal temperature side conductor portion 42 . The epoxy unit 63 is provided on a portion of the outer periphery of the superconductor layer 14 and in the vicinity of a portion between the coolant pools 51 , 52 .

When the superconducting cable of the present invention including the terminal structure having the above-mentioned structure is used as a three-phase AC line, for example, the drawn conductor part 40 connected to the outer superconducting layer 15 should have the transverse width of the conductor required to obtain the ground voltage. cross-sectional area. Therefore, as shown in FIG. 5 , when the low temperature side conductor portion 41 and the normal temperature side conductor portion 42 of the required extraction conductor portion 40 are connected to each other, it is not necessary to connect the low temperature side conductor portion 41 and the normal temperature side conductor portion of the extraction conductor portion 40 to each other. 42 are separated from each other to obtain the required conductor cross-sectional area. In this example, a ground wire for grounding is connected to the end portion on the normal temperature side of the normal temperature side conductor portion 42 of the drawn out conductor portion 40 being connected.

On the other hand, when it is necessary to convert the three-phase AC transmission as shown in FIG. 5 into DC transmission, a current equivalent to that for the superconductor layer 14 flows through the outer superconductor layer 15 . That is, the current flowing through the outer superconducting layer 15 is increased, and the current flowing through the drawn conductor portion 40 is also increased compared with those in the case of AC transmission shown in FIG. 5 . Therefore, as shown in FIG. 6 , the low-temperature-side conductor portion 41 and the normal-temperature-side conductor portion 42 of the drawn-out conductor portion 40 that are separated from each other during AC transmission are connected to each other, thereby securing the necessary capacity for passing the required amount of current. Sufficient conductor cross-sectional area. In this example, the lead portion 43 for grounding is connected to the normal-temperature-side end portion of the normal-temperature-side conductor portion 42 of the drawn-out conductor portion 40 to be connected. Conversely, when it is necessary to convert DC transmission as shown in FIG. 6 into AC transmission, separating one of the extracted conductor portions 40 that form conduction during the DC transmission will break its conduction.

The superconducting cable line of the present invention is suitable for performing a line for transmitting electric power to various power apparatuses. The superconducting cable of the present invention can be constructed, for example, by incorporating a superconducting cable into a pipeline for transporting liquid hydrogen and providing a heat exchange device at a hydrogen station connected to the pipeline. In this case, the circuit of the invention can be used as the power supply line of the power supply unit inside the hydrogen station or as the power supply line of any power supply unit which absorbs power as required from the thermally insulated pipes for the fluid. In addition, since the cable line of the present invention can be constructed during the construction of a transport channel for liquid hydrogen or a hydrogen station, the operability of laying can be increased.

Claims (7)

1. A superconducting cable circuit, comprising: A heat insulating pipe (2) for fluid, the heat insulating pipe for fluid is used for transporting liquid hydrogen (1); a superconducting cable (10) housed in said thermal insulation tube for fluid (2), whereby the superconducting part (12) is cooled by a coolant having a temperature higher than said liquid hydrogen (1); as well as Heat exchange means (30) for cooling said liquid hydrogen (1) and raising the temperature of the coolant of the cable cooled by said liquid hydrogen (1). 2. The superconducting cable line according to claim 1, wherein the superconducting cable (10) is immersed in the liquid hydrogen (10). 3. The superconducting cable line according to claim 1, wherein the area inside the thermally insulating tube (2) for fluid is divided into a transport area for transporting the liquid hydrogen (1) and a transport area for transporting the liquid hydrogen (1) A region in which the superconducting cable (10) is arranged. 4. The superconducting cable line according to claim 1, wherein the coolant of the superconducting cable (10) is liquid nitrogen. 5. The superconducting cable line according to claim 1, wherein, The superconducting cable (10) comprises a superconductor layer (14) and an electrically insulating layer provided on the outer periphery of the superconductor layer (14), and The electrical insulating layer is p-graded to obtain low resistivity on the inner peripheral side and high resistivity on the outer peripheral side of the electrical insulating layer, thereby smoothing the DC electric field distribution in the diameter direction thereof. 6. The superconducting cable line according to claim 5, wherein said electrical insulating layer has a high ε layer, which is arranged near said superconductor layer (14) and has a higher dielectric constant than the other part the dielectric constant. 7. The superconducting cable line according to claim 5, wherein the electric insulating layer is configured such that a dielectric constant increases toward an inner peripheral side and a dielectric constant decreases toward an outer peripheral side.

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