JP2007028710A - Connection structure for dc superconductive cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection structure for a DC superconductive cable which can remove foreign matter carried together with a refrigerant. <P>SOLUTION: This connection structure is equipped with a superconductor 11 provided in a cable core 10 drawn out of a superconductive cable, a conductor lead-out part (a sleeve 12, a lead part 13, a joint part 14, and a bushing 15) on normal temperature side connected to the superconductor 11, and a terminal connection box 20 where these connection points are stored. The terminal connection box 20 is equipped with a refrigerant container 21 filled with a refrigerant and a vacuum container 22 arranged to cover the periphery of the refrigerant container 21. A supply path 23, which supplies a refrigerant into a box 21 and a discharge path 24, which discharges a refrigerant from the box 21, are connected to the refrigerant container 21, and the refrigerant is circulated by these supply path 23 and the discharge path 24. The supply path 23 is equipped with a filtering means 1, which removes foreign matter f carried together with the refrigerant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a connection structure for a superconducting cable used for direct current power transmission. In particular, the present invention relates to a superconducting cable connection structure capable of removing foreign matters transported together with a refrigerant.

  In recent years, superconducting cables have been studied as power cables. A superconducting cable has a cable core having a superconducting conductor and a heat insulating tube for housing the core. A refrigerant such as liquid nitrogen is circulated in the heat insulating tube, and the core is cooled by this refrigerant to superconducting the superconducting conductor. It is the structure maintained to. The cable core generally includes a former, a superconducting conductor, and an electrical insulating layer in order from the center. When constructing a power supply line using such a superconducting cable, in addition to an intermediate connection structure for connecting the cables, a superconducting cable in a low temperature state and a normal temperature side power device such as a normal conducting cable arranged at room temperature A terminal connection structure to be connected is constructed.

  FIG. 4 is a schematic configuration diagram showing an intermediate connection structure of a superconducting cable. The intermediate connection structure accommodates the cable core 101A drawn from the end of one superconducting cable 100A to be connected, the cable core 101B drawn from the end of the other superconducting cable 100B, and the ends of these cores 101A and 101B. And an intermediate junction box 110. The connection of each core 101A, 101B is stepped off to expose a former (not shown) formed of superconducting conductors 102A, 102B and copper stranded wire. The insertion is performed by compressing the sleeve 103 and inserting both the superconducting conductors 102A and 102B into the sleeve 103 and soldering. A reinforcing insulating layer 104 is provided on the outer periphery of the superconducting conductors 102A and 102B and the sleeve 103. An intermediate connection box 110 in which the ends of the cores 101A and 101B and the connection points of the superconducting conductors 102A and 102B are housed is a refrigerant tank 111 in which a refrigerant such as liquid nitrogen is circulated, and a vacuum disposed on the outer periphery of the refrigerant tank 111. A tank 112 is provided. Refrigerant circulation in the refrigerant tank 111 is performed between a tank 111 and a cooling system (not shown) that stores and cools the refrigerant, and a supply path (same as above) that transports the refrigerant introduced into the tank 111. It connects with the discharge path (same) which conveys the refrigerant | coolant discharged | emitted from 111 inside and returned to a cooling system, and performs using these supply paths and discharge paths. In addition, the refrigerant may be circulated by introducing the refrigerant from one superconducting cable connected to the refrigerant tank 111 and discharging the refrigerant to the other cable.

  On the other hand, as a terminal connection structure of a superconducting cable, for example, there is a structure shown in FIG. 5 (see Patent Document 1). This termination connection structure accommodates the cable core 101 drawn from the end portion of the superconducting cable, the room temperature side conductor lead portion connected to the end portion of the core 101, and the core connection side in the room temperature side conductor lead portion. And a termination junction box 200. The room temperature side conductor lead-out portion is connected to the superconducting conductor 102 exposed by stripping the end portion of the core 101 via the terminal connection sleeve 150, and connected to the lead portion 151 via the joint portion 152. And a bushing 153 to be provided. The sleeve 150, the lead portion 151, the joint portion 152, and a conductor portion 153a described later are formed of a conductive material such as copper, and the superconducting conductor 102 and the sleeve 150 are connected by soldering. Reinforcing insulating layers 104a and 104b are formed on the outer periphery of the superconducting conductor 102, the sleeve 150, and the lead portion 151. The bushing 153 has a conductor portion 153a connected to the lead portion 151 at the center, and includes a solid insulating layer 153b formed of FRP or the like on the outer periphery of the conductor portion 153a. Both ends of the solid insulating layer 153b are provided with stress cone portions formed in a tapered shape.

Then, a part of the superconducting conductor 102, the sleeve 150, and the lead part 151 (on the side connected to the superconducting conductor 102) is housed in the auxiliary connection box 210 connected to the terminal connection box 200, and the other part of the lead part 151 (bushing 153), the joint portion 152, and a part of the bushing 153 (the connection side with the lead portion 151) are accommodated in the terminal junction box 200. The terminal junction box 200 and the auxiliary junction box 210 include refrigerant tanks 201 and 211 in which a refrigerant such as liquid nitrogen is circulated, and vacuum tanks 202 and 212 arranged to cover the outer periphery of the refrigerant tanks 201 and 211. These refrigerant tanks 201 and 211 and vacuum tanks 202 and 212 are formed of a high-strength material such as stainless steel. The other part of the bushing 153 disposed on the normal temperature side is protruded outside the terminal junction box 200 and is housed in a soot tube 220 filled with an insulating fluid such as insulating oil or SF ₆ gas.

  In the refrigerant tanks 201 and 211, for example, as shown in FIG. 5, supply paths 203 and 213 for introducing refrigerant from a cooling system (not shown), and refrigerant discharged from the tanks 201 and 211 for transporting to the cooling system The discharge paths 204 and 214 are connected, and the refrigerant controlled to a predetermined temperature and transport pressure by the cooling system is circulated and supplied. In addition, a terminal connection box is provided with only the supply path or the discharge path, and the refrigerant introduced from the supply path is supplied from the terminal connection box to the superconducting cable connected to the terminal connection box, and is separated via the cable. The refrigerant may be discharged through a discharge path connected to the terminal connection box or the intermediate connection box. In addition, the refrigerant tank 201 is connected to the ground wire 205, the inner surface of the tank 201 is set to the ground potential (low voltage), and a refrigerant having excellent insulation properties such as liquid nitrogen is used for the high voltage side joint portion 152. In contrast, the structure is provided with insulating properties.

  On the other hand, the solid insulation layer 153b of the bushing 153 has a so-called capacitor-type electric field control structure in which FRP and foil electrodes are laminated on the outer periphery of a stainless steel pipe. It has been proposed to control the electric field as described above.

JP 2005-12915 (Fig. 5)

  When a line is constructed using a superconducting cable and the connection structure as described above, and direct current transmission is performed on this line, there is no direct current on the outer periphery of the superconducting conductor or the outer periphery of the portion connected to the superconducting conductor and energized. A world arises. And, the dust containing metal is easily collected at the place where the DC electric field is applied, and when such dust is collected at the place where the DC electric field is applied in the connection structure, the dust functions as the projection of the electrode, There is a risk of destruction.

  When forming the connection structure, silver, metal powder such as copper or stainless steel, solder powder used for connection, or the like that has come out of a constituent member such as a superconducting conductor may remain in the refrigerant tank. Further, metallic dust may be generated in the cooling system due to sliding friction between the constituent members and the refrigerant. Since the superconducting cable line circulates the refrigerant as described above, metallic foreign matters such as the metallic dust are also transported along with the transportation of the refrigerant. At this time, as a superconducting cable, when using a cable including a cable core having an electric field shielding structure having a shield layer that becomes a ground potential on the outer periphery of a superconducting conductor having a high potential, in this cable portion, the surface of the core Even if foreign matter accumulates, there is almost no possibility of causing creepage failure. However, unlike the cable portion, the connection structure may have a portion where the electric field is released. In such a place, if foreign matter accumulates on the surface, it may cause creeping damage. For example, in the terminal connection structure, when foreign matter accumulates on the surface of the stress cone portion at the bushing end portion that is in contact with the refrigerant on the bushing surface, there is a risk of causing creepage failure at this portion. Of the parts stored in the refrigerant tank in the bushing, the flat part in the middle often has an electric field shielding structure with a shield layer that is at ground potential, but the stress cone part at the end has a shield layer. In some cases, the surface is exposed without being provided. In such a case, the electric field is opened in the refrigerant in the refrigerant tank. For this reason, metallic foreign matters are likely to accumulate on the stress cone portion of the bushing, and creeping damage may occur due to the foreign matters.

  On the other hand, in the intermediate connection structure, like the cable portion having the electric field shielding structure, the electric field shielding structure is provided on the surface of the ground potential layer (shield layer) by providing a shield layer having a ground potential on the outer periphery of the reinforcing insulating layer. Even if foreign matter accumulates, creeping damage hardly occurs. However, when a foreign substance enters inside the ground potential layer, the state becomes electrically unstable.

  Accordingly, a main object of the present invention is to provide a connection structure that can effectively remove foreign matters in a connection structure of a DC superconducting cable in order to eliminate problems caused by foreign matters such as metallic dust.

  The present invention is a DC superconducting cable connection structure comprising a superconducting conductor provided in a superconducting cable and a connection box in which a connection object to the superconducting conductor is accommodated and in which a refrigerant for cooling the superconducting conductor is circulated. In addition, a supply path for supplying the refrigerant into the box and a discharge path for discharging the refrigerant to the outside of the box are connected to the connection box. And in this invention, it is proposed to provide a filtration means in order to remove effectively the foreign material conveyed by a refrigerant | coolant in the refrigerant | coolant flow path which leads to a discharge path from this supply path through a junction box. Hereinafter, the present invention will be described in more detail.

  In the present invention, the connection structure may be any of intermediate connection for connecting the superconducting cables, and termination connection for connecting a room temperature side device such as a superconducting cable arranged on the low temperature side and a normal conducting cable arranged on the room temperature side. . The configuration of the superconducting cable to be used is not particularly limited. A typical example includes a cable core having a superconducting conductor and a heat insulating pipe that houses the core and in which a refrigerant for cooling the superconducting conductor is circulated. As a basic configuration of the cable core, a configuration having a former, a superconducting conductor, and an electrical insulating layer in order from the center can be given. Further, an outer superconducting layer made of a superconducting material as in the superconducting conductor may be provided on the outer periphery of the electrical insulating layer, and a protective layer may be provided on the outer periphery thereof. When the external superconducting layer is provided, the external superconducting layer is set to the ground potential (ground potential). When the external superconducting layer is not provided, a grounding shield layer as a ground potential may be provided. The superconducting cable may be a single-core cable having one such cable core or a multi-core cable having a plurality of cores. In the case of a multi-core cable having a plurality of cores, the plurality of cores may be twisted and then stored in the heat insulating tube. The heat insulation pipe which accommodates the said cable core is the double structure which consists of an inner pipe and an outer pipe, and the structure which evacuated the inside of a double pipe is mentioned. Furthermore, you may arrange | position a heat insulating material between both pipes. The inside of the inner pipe is used as a refrigerant flow path for cooling the superconducting conductor and the outer superconducting layer.

  The former may be a solid body or a hollow body formed of a metal material such as copper or aluminum, and examples thereof include a configuration in which a plurality of copper wires are twisted together. For example, the superconducting conductor may be formed by winding a wire made of an oxide superconducting material, specifically a Bi2223 superconducting material, around the former in a single layer or multiple layers. When the superconducting conductor is a multilayer, 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 electrical insulating layer may be formed by winding an insulating material such as insulating paper such as kraft paper or semi-synthetic insulating paper such as PPLP (registered trademark) around the outer periphery of the superconducting conductor. When an external superconducting layer is provided on the outer periphery of the electrical insulating layer in addition to the superconducting conductor, it may be formed of a superconducting material in the same manner as the superconducting conductor. Furthermore, a semiconductive layer may be provided by carbon paper or the like between the superconducting conductor and the electric insulating layer, and between the electric insulating layer and the external superconducting layer. A configuration including the former internal semiconductive layer and the latter external semiconductive layer is effective in stabilizing electrical performance.

  The connection structure of the present invention is formed at the end of the superconducting cable. Specifically, it is formed by stripping the cable end (cable core end) and exposing a part of the superconducting conductor. The object to be connected to the exposed superconducting conductor is a superconducting conductor provided in another superconducting cable when the connecting structure of the present invention is used as an intermediate connection. It becomes a normal temperature side conductor lead-out part arranged in the.

  When the connection structure of the present invention is an intermediate connection, the superconducting conductors may be connected using an intermediate connection sleeve made of a conductive material such as copper. As an intermediate | middle connection sleeve, the thing of the shape which has a hollow part which can insert a superconducting conductor and a former | foamer in both ends is mentioned, for example. When using this sleeve, first insert the former into the hollow part and compress it, connect the former and the sleeve by crimping, and then insert the superconducting conductors drawn from both cables into the hollow part, soldering etc. It is preferable to connect the superconducting conductor and the sleeve. Alternatively, use an intermediate connection sleeve with a shape that has a hollow part into which both ends can be inserted. Insert the former into the hollow part and connect the former to the sleeve by crimping, etc., and connect to the outer periphery of this sleeve. The superconducting material may be connected to each other by fixing the superconducting material for vertical connection and soldering the superconducting conductors drawn from both cables to both ends of the connecting superconducting material. A reinforcing insulating layer is formed on the outer periphery of the superconducting conductor and the sleeve using an insulating material such as kraft paper or semi-synthetic insulating paper. Since the electric field tends to concentrate on the end portion of the reinforcing insulating layer, it is preferable that the end portion of the reinforcing insulating layer has a shape capable of controlling the electric field as a taper shape that tapers away from the intermediate connection sleeve. Moreover, the connection part of such a superconducting conductor is good also as a structure fixed to the intermediate | middle junction box mentioned later. For example, by providing a solid insulating member made of epoxy resin or the like on the outer periphery of the connection portion, attaching a fixing member for fixing the solid insulating member to the intermediate connection box, and fixing the solid insulating member to the fixing member, superconductivity The connecting portion of the conductor may be fixed to the intermediate connection box. This fixing member is constituted by, for example, a plate-like member having a shape adapted to the inner periphery of the intermediate connection box (refrigerant tank), and the space in the intermediate connection box is one superconducting cable side and the other superconducting cable side. It may be used as a partition wall that is separated into two. An electric field shielding structure may be provided by providing a shield layer made of a conductive material on the outer periphery of the reinforcing insulating layer. Examples of the conductive material forming the shield layer include carbon paper, annealed copper wire, and metal mesh tape. The shield layer may be formed by winding these conductive materials on the reinforcing insulating layer. This shield layer is set to the ground potential. With such an electric field shielding structure, even when metallic foreign matter is accumulated on the surface of the reinforcing insulating layer, creeping damage hardly occurs. However, if foreign matter enters the inside of the shield layer, it becomes electrically unstable. Therefore, in the connection structure of the present invention, it is proposed that the intermediate connection structure has a filtering means.

  When the connection structure of the present invention is a terminal connection, examples of the room temperature side conductor lead-out portion include a lead portion connected to the superconducting conductor and a bushing connected to the lead portion. Examples of the lead portion include a rod-shaped body made of a conductive material such as copper. The lead portion and the superconducting conductor may be connected via a terminal connection sleeve made of a conductive material such as copper. The terminal connection sleeve includes a conductor-side insertion hole into which a superconducting conductor or former can be inserted at one end, and a lead-side insertion hole into which the lead portion can be inserted at the other end. To connect the lead part and the superconducting conductor using this sleeve, for example, after inserting the former into the insertion hole and crimping it to connect the former to the sleeve, the superconducting conductor is inserted into the conductor side insertion hole. Connect the sleeve and the superconducting conductor by soldering. On the other hand, the lead part is inserted into the lead part side insertion hole and crimped to connect the sleeve and the lead part, or the lead part side insertion hole is provided with a multi-contact (product name). Connect the sleeve and the lead part. In this way, the superconducting conductor and the lead portion can be connected via the sleeve. A reinforcing insulating layer is formed on the outer periphery of these superconducting conductors, sleeves, and lead portions using an insulating material such as kraft paper or PPLP (registered trademark), as in the case of the intermediate connection. Since the electric field tends to concentrate on the end portion of the reinforcing insulating layer, it is preferable that the end portion of the reinforcing insulating layer has a shape capable of controlling the electric field as a tapered shape that tapers away from the terminal connection sleeve. The bushing has a configuration in which a conductive portion made of a conductive material such as copper is connected to the lead portion at the center, and a solid insulating layer formed of an insulating material such as FRP is provided on the outer periphery of the conductive portion. Can be mentioned. The solid insulating layer is preferably a so-called capacitor-type electric field control structure in which an insulating material such as FRP and a foil electrode are laminated on the outer periphery of a metal pipe such as a stainless steel pipe. In addition, since the electric field tends to concentrate at both ends of the solid insulating layer, it is preferable that both have a shape that can control the electric field as a tapered shape that tapers toward the end. The bushing and the lead portion may be connected via a joint portion made of a conductive material such as copper.

The superconducting conductor and its connection target are stored in a connection box. The connection box preferably has a configuration including a refrigerant tank filled with a refrigerant for cooling the superconducting conductor and the like, and a vacuum tank arranged so as to cover the outer periphery of the refrigerant tank. Such a junction box is preferably formed of a high-strength material such as a metal such as stainless steel having excellent strength. When the connection structure of the present invention is an intermediate connection, the superconducting conductor to be connected and the intermediate connection sleeve used for the connection may be stored in the same connection box. When the connection structure of the present invention is a terminal connection, the superconducting conductor and the room temperature side conductor lead-out part may be housed in the same junction box, or the superconducting conductor and a part of the room temperature side conductor lead-out part may be housed. The junction box for storing the other part of the room temperature side conductor lead-out part may be separated. In the room temperature side conductor lead-out portion, the room temperature side is housed in a soot tube filled with an insulating fluid such as insulating oil or SF ₆ gas. This soot tube may be projected outside the vacuum chamber. These connection boxes are preferably configured to be grounded by attaching a grounding wire so as to be at a low voltage (ground potential) at a connection point with a superconducting conductor having a high voltage.

  And in this invention, it is set as the structure which comprises the supply path which supplies a refrigerant | coolant in the said connection box, and the discharge path which discharges | emits a refrigerant | coolant outside a connection box, and distribute | circulates a refrigerant | coolant in a connection box. When constructing a superconducting cable line, a cooling system equipped with a tank, a refrigerator, a pump, and the like is usually provided, and refrigerant storage, temperature control, transport pressure control, and the like are performed by this cooling system. Therefore, the supply path and the discharge path are connected to the cooling system, the refrigerant controlled to a predetermined temperature and flow rate by the system is supplied into the junction box, and the refrigerant whose temperature has increased due to intrusion heat or the like is connected to the junction box. Circulating supply such as discharging outside and returning to the system to adjust the temperature of the refrigerant, etc., and supplying it again into the box may be performed. A non-circular supply such as discharging the refrigerant that has become may be performed. Such a supply path and a discharge path are composed of a double pipe composed of an inner pipe and an outer pipe so that the refrigerant can maintain a predetermined temperature, and the inside of the double pipe is evacuated. You may arrange | position a heat insulating material between double pipes. These tubes are preferably formed of a high-strength material such as a metal such as stainless steel having excellent strength.

  In the connection structure of the present invention, the supply path, the connection box (refrigerant tank), and the discharge path described above serve as a refrigerant flow path, and the most characteristic feature is that the refrigerant flow path includes a filtering means. The filtering means can be used in a refrigerant temperature range, for example, in the case of using liquid nitrogen as a refrigerant, about 65 to 77K, and a filter made of a material that can withstand a transport pressure during refrigerant circulation, for example, about 0.5 MPa · G. It can be suitably used. Examples of such a filter include a mesh member made of stainless steel and a filter member having an element made of a sintered body on the mesh member. A known filtration means may be used.

  When a filter is used as the filtering means, the filtering ability can be changed by changing the mesh size of the filter. If the mesh size is made too large, there is a possibility that foreign substances having an adverse effect cannot be captured. Therefore, in order to capture foreign substances more reliably, it is desirable to reduce the mesh size. However, if the mesh size is too small, the pressure loss during refrigerant transportation increases. Considering these circumstances, the mesh size is preferably 2 μm or more and 300 μm or less, and particularly preferably 75 μm or more and 100 μm or less.

  Examples of the shape of the filtering means include a plate shape and a bottomed cylindrical shape. In the case of the latter bottomed cylindrical shape, a cylindrical shape is mentioned as a cylindrical shape. In addition, when the bottomed cylindrical shape is used, both the side wall portion and the bottom portion may have a net shape, and both portions may be configured to allow refrigerant to pass therethrough. And maintenance such as cleaning may take time. Therefore, in the case of using a bottomed cylindrical filtration means, the side wall portion may be meshed to allow the refrigerant to pass therethrough, and the bottom portion may not be meshed and may be a foreign matter retaining portion. With this configuration, the foreign matter adhering to the side wall portion settles and accumulates at the bottom portion, and clogging of the side wall portion is reduced. Further, in this case, it is preferable to arrange the filtering means so that the bottom portion is located on the downstream side with respect to the flow direction of the refrigerant so that foreign matters are likely to be accumulated in the bottom portion.

  The filtration means may be disposed in at least one of a supply path, a discharge path, and a connection box (refrigerant tank), and may be disposed in any one of the supply path, the discharge path, and the connection box, You may arrange | position to both of a discharge path, a supply path or both a discharge path, and a connection box, and may arrange | position to all of these three. Moreover, it is good also as a structure which arrange | positions a filtration means in two or more different places as mentioned above, and provides a plurality of filtration means as the whole connection structure. It is good also as a structure which arrange | positions and provides several filtration means as the whole connection structure. Thus, by providing a plurality of filtering means in multiple stages, foreign substances can be captured more reliably. When arranging a plurality of filtering means, each filtering means may have the same specification, or may have different specifications, for example, different mesh sizes.

  Further, it is preferable that the filtering means be configured to be detachable from the refrigerant flow passage because maintenance work such as replacement and cleaning can be easily performed. In particular, when a filtering means is provided in the supply path or the discharge path, it is preferable that valves be provided on the refrigerant introduction side (upstream side of the refrigerant) and the refrigerant discharge side (downstream side of the refrigerant) in the filtering means. These valves are normally opened to allow the refrigerant to flow, such as supply of refrigerant to the junction box or discharge of refrigerant from the junction box, and be closed during maintenance of the filtering means. The supply of the refrigerant or the discharge of the refrigerant is stopped in a state where the refrigerant is filled. By providing the valve in this way and closing the valve, the filtering means provided in the supply path and the discharge path and the connection box can be separated. Maintenance work can be performed without draining. That is, the maintenance work can be performed in a state where the line having the connection structure of the present invention performs DC power transmission (energized state). As such a valve, for example, a valve having a commercially available vacuum jacket (for example, a jacket type vacuum insulation valve manufactured by Yamada Valve Manufacturing Co., Ltd.) may be used.

  By providing a valve as described above, it is possible to perform maintenance of the filtering means in a state where the junction box is filled with the refrigerant. As a result, the temperature of the refrigerant rises and the superconducting conductor in the junction box may not be able to maintain the superconducting state. Therefore, even if the line having the connection structure of the present invention is in an energized state, the transportation path such as the supply path and the discharge path is not a single system (single), but a plurality of systems (single) so that the filtration means can be sufficiently maintained. It is preferable to use a plurality of). Specifically, the transportation path is branched, a plurality of branch paths are arranged in parallel, each of the branch paths is provided with a filtering means, and each filtering means is provided with a valve on both the refrigerant introduction side and the discharge side. Is preferable. By supplying a plurality of parallel branch passages each having a filtering means and having a valve on each branch passage, the supply and discharge of the refrigerant is normally performed using a certain branch passage. When maintaining the filtering means provided in this branch path, the valve of this branch path is closed and the valve of another branch path is opened and switched to the other branch path, so that the flow of the refrigerant can be stopped without stopping. Means maintenance can be performed. When the maintenance of the filtration means is completed, the branch path may be switched by opening and closing the valve again, or the refrigerant is used as it is until the filtration means provided in the branch path switched for maintenance performs the maintenance. May be transported.

  The connection structure of the present invention is intended for use in DC power transmission. The direct current power transmission may be either single pole power transmission (monopole power transmission) or bipolar transmission (bipole power transmission). For single-pole power transmission, prepare two or more single-core cables that have a superconducting conductor and have a coaxial cable core that does not have a separate external superconducting layer. The conductor may be the forward path, the superconducting conductor provided in the core of another cable may be returned, and the remaining cable may be reserved, or two cores that have a superconducting conductor and do not have a separate external superconducting layer coaxially. One multi-core cable having the above may be prepared, the superconducting conductor provided in one of the cores may be the outgoing path, the superconducting conductor provided in another core may be the return path, and the remaining core may be used as a spare core. In either case, the cable core is provided with a ground shield layer. Alternatively, a superconducting cable (which may be single-core or multi-core) having a superconducting conductor and a cable core having an outer superconducting layer coaxially with the superconducting conductor is prepared, and the superconducting conductor is connected to the outer superconducting layer in the same core. May be the return route. The external superconducting layer is grounded.

  When conducting bipolar power transmission, prepare three or more single-core cables that have a superconducting conductor and have a coaxial cable core that does not have a separate external superconducting layer. Can be used as a positive electrode, a superconducting conductor provided in the core of another cable as a negative electrode, a superconducting conductor provided in another cable as a neutral wire, and the remaining cables as spares. Prepare a single multi-core cable with three or more cable cores that do not have an external superconducting layer, one core superconducting conductor as the positive electrode, another core superconducting conductor as the negative electrode, and another core superconducting The conductor may be a neutral wire and the remaining core may be a spare core. In either case, the positive electrode core and the negative electrode core are provided with a ground shield layer. Alternatively, a multi-core cable having two or more superconducting conductors and a cable core having an outer superconducting layer coaxially with the superconducting conductor is prepared, the superconducting conductor of one core is the positive electrode, and the superconducting conductor of the other core is provided. The negative electrode, the external superconducting layers of these two cores may be neutral wires, and the remaining cores may be reserved. The external superconducting layer is grounded.

  As described above, since the connection structure of the present invention can efficiently remove metallic foreign matters by providing the filtering means in the refrigerant flow passage, the surface of the connection member, particularly the portion where a DC electric field is applied. It is possible to effectively prevent foreign matter from accumulating on the surface of the metal and causing surface damage due to surface discharge. In addition, the connection structure of the present invention is provided with a filtering means, so that not only the above-mentioned metallic foreign matter but also insulating material waste generated at the time of manufacturing the connection structure and moisture (moisture) entering the connection structure are cooled by the refrigerant. In addition, foreign matters such as solidified matter (ice) generated can be removed. Therefore, in addition to preventing electrical problems due to these foreign substances, it is possible to prevent problems such as blocking of the refrigerant flow path, particularly the supply path and the discharge path, and damage to constituent members due to collisions of foreign substances. it can.

  Embodiments of the present invention will be described below.

  FIG. 1 (A) is a schematic configuration diagram showing a termination connection structure in the connection structure of the present invention, and FIG. 1 (B) is a schematic configuration diagram showing a state in which filtering means is arranged in a supply path. The basic configuration of this termination connection structure is the same as the conventional configuration shown in FIG. That is, the cable core 10 drawn from the end of the superconducting cable, the normal temperature side conductor lead portion connected to the end portion of the core 10, and the termination junction box 20 that houses the connection side with the core in the normal temperature side conductor lead portion With. The termination junction box 20 includes a refrigerant tank 21 filled with a cryogenic refrigerant for cooling a connection portion with the core 10 and a vacuum tank 22 arranged so as to cover the outer periphery of the refrigerant tank 21. . The connection box 20 is connected to a supply path 23 for supplying the refrigerant to the refrigerant tank 21 and a discharge path 24 for discharging the refrigerant from the refrigerant tank 21. These supply path 23 and discharge path 24 are connected to a separate cooling system (not shown), and supply path 23 → connection box 20 (refrigerant tank 21) → discharge path 24 → cooling system (→ supply path 23). ), The refrigerant is circulated and supplied to the connection box 20. That is, in this terminal connection structure, the above path is used as a refrigerant flow path. In such a terminal connection structure, the most characteristic feature is that in the supply path 23 forming the refrigerant flow path, in the vicinity of the refrigerant tank 21 (indicated by a broken line circle A in FIG. 1 (A), outside the vacuum tank 22), The filtering means 1 (see FIG. 1B) is provided, and the filtering means 1 removes foreign matters transported along with the refrigerant.

  In this example, as the superconducting cable, a single-core cable in which a cable core including a former, a superconducting conductor, an electric insulating layer, an external superconducting layer, and a protective layer is housed in a heat insulating tube in order from the inner peripheral side. The superconducting conductor and the external superconducting layer were formed by using Bi2223 superconducting tape wire (Ag-Mn sheath wire) and spirally winding the tape wire around the outer periphery of the former and the outer periphery of the electrical insulating layer. As the former, a plurality of twisted copper wires were used, and a cushion layer was formed of insulating paper between the former and the superconducting conductor. The electrical insulating layer was formed by winding semi-synthetic insulating paper PPLP (registered trademark) so as to have a predetermined insulation strength with respect to the superconducting conductor. A semiconductive layer may be provided on the inner periphery of the electrical insulating layer (the outer periphery of the superconducting conductor) and on the outer periphery of the electrical insulating layer (the inner periphery of the external superconducting layer). The protective layer was formed by winding kraft paper. The heat insulation pipe is a double pipe consisting of an inner pipe and an outer pipe made of stainless steel, and a heat insulating material such as Super Insulation (trade name) is arranged on the outer circumference of the inner pipe, and a vacuum is drawn between the two pipes. The configuration. A refrigerant (in this example, liquid nitrogen) for cooling the superconducting conductor and the outer superconducting layer is circulated through the inner tube. Pull out the cable core 10 from the end of such a superconducting cable, step off the end of the core 10 to sequentially expose the external superconducting layer, the electrical insulating layer, the superconducting conductor 11, and the former, and use the terminal connection sleeve 12 Then, the superconducting conductor 11 and the room temperature side conductor lead-out portion are connected. The end connection sleeve 12 has a conductor side insertion hole into which the former and the superconducting conductor 11 can be inserted at one end, and a lead portion side insertion hole into which the room temperature side conductor lead-out portion (lead portion 13 described later) can be inserted at the other end. A copper tubular member was used. The superconducting conductor 11 and the sleeve 12 are connected by inserting the former and the superconducting conductor 11 into the conductor-side insertion hole, connecting the sleeve 12 and the former by crimping, and then soldering the superconducting conductor 11. The lead part 13 and the sleeve 12 were connected by providing a multi-contact inside the lead part side insertion hole of the sleeve 12 and making contact with the multi-contact.

The room temperature side conductor lead portion includes a lead portion 13 connected to the superconducting conductor 11 via the sleeve 12 and a bushing 15 connected to the lead portion 13 via the joint portion 14. The lead part 13 was made of a copper rod-like body. Reinforcing insulating layers 16a and 16b are formed of synthetic insulating paper on the outer periphery of the superconducting conductor 11, the sleeve 12, and the lead portion 13 in the same manner as the electric insulating layer. The ends of the reinforcing insulating layers 16a and 16b are tapered (a shape that tapers as the distance from the sleeve 12 increases) in order to control the concentration of the electric field. The joint portion 14 is made of a copper braided material having a connection end with the lead portion 13 and a connection end with the bushing 15, and has a shield structure in which the outer periphery is covered with a copper cover. The bushing 15 has a conductor part 15a made of a copper rod connected to the lead part 13 at the center, and includes a solid insulating layer 15b formed of FRP on the outer periphery of the conductor part 15a. The solid insulating layer 15b is formed by laminating FRP and foil electrodes on the outer periphery of a stainless steel pipe, and both ends are tapered (one end on the low temperature side is tapered toward the joint portion 14, and the other end on the normal temperature side is a cover. A rod-shaped body having a stress cone portion of 31 (to taper toward 31 (described later)) was obtained. With this laminated structure, so-called capacitor-type electric field control was performed so that the DC electric field applied to the surface of the bushing 15 was uniform. In such a room temperature side conductor lead-out part, a part of the lead part 13 (connection side with the joint part 14), a part of the joint part 14 and a bushing 15 (connection side with the joint part 14) are stored in the refrigerant tank 21. Then, the outer periphery is covered with the vacuum chamber 22. The refrigerant tank 21 and the vacuum tank 22 are stainless steel containers. A ground wire 25 is connected to the refrigerant tank 21, and the ground tank 25 is grounded so that the refrigerant tank 21 is configured to have a ground potential, and liquid nitrogen having excellent insulating properties is used as the refrigerant. As a result, insulation is maintained with respect to a high voltage portion such as the joint portion 14. The ground line 25 is penetrated through the vacuum chamber 22, and a hermetic seal is used as a seal at the penetration portion in the vacuum chamber 22 to maintain airtightness. Insulating spacers (epoxy units) 17 made of an epoxy resin are disposed on the outer periphery of the portion where the lead portion 13 is introduced into the refrigerant tank 21 in order to insulate it from the refrigerant tank 21 at the ground potential. The vacuum chamber 22 is provided with a heat insulating material such as super insulation inside and is evacuated to a predetermined degree of vacuum. Also, outside the vacuum chamber 22, a soot tube 30 is provided which is filled with an insulating fluid such as insulating oil or SF ₆ gas, and one end of the bushing 15 (the side connected to the normal conducting device) is provided. Stored. A normal temperature side end portion of the soot tube 30 has a shield structure covered with a conductive cover 31.

  A part of the superconducting conductor 11, the sleeve 12, and the lead portion 13 covered with the reinforcing insulating layer 16a is housed in an auxiliary connection box 40 connected to the terminal connection box 20. The auxiliary junction box 40 includes a refrigerant tank 41 through which a refrigerant for cooling the superconducting conductor 11 is circulated, and a vacuum tank 42 covering the outer periphery thereof. The configuration of the auxiliary connection box 40 is the same as that of the terminal connection box 20, and the refrigerant tank 41 is connected to the refrigerant supply path 43 and the discharge path 44 in the same manner as the refrigerant tank 21, and the supply path 43 and the discharge path. Refrigerant is distributed using 44. These supply path 43 and discharge path 44 are also connected to a cooling system (not shown), and circulate and supply refrigerant to the auxiliary connection box 40 in the same manner as the connection box 20. Accordingly, the supply path 43, the auxiliary connection box 40 (refrigerant tank 41), and the discharge path 44 are also used as the refrigerant flow path. In this example, the refrigerant tank 21 and the refrigerant tank 41 are separated from each other so that the refrigerant does not go back and forth directly. The supply path 42 and the discharge path 43 have the same configuration as a supply path 23 and a discharge path 24 described later.

  As shown in FIG. 1 (B), the supply path 23 is composed of a double tube of an inner tube 23a and an outer tube 23b, and is a heat insulating structure in which the space between both the tubes 23a and 23b is evacuated. Is used as a refrigerant flow passage. The discharge path 24 has the same configuration. In this example, the filtering means 1 is provided in the inner tube 23a. The filtering means 1 is a bottomed cylindrical filter, and is formed of a plate material in which the side wall 1a is permeable to refrigerant and the bottom 1b is not permeable to refrigerant. Examples of such a filter include trade name: Poremet (manufactured by FLOWELL CORPORATION), cylindrical type (CY), and mesh size 100 μm. The size of the filtering means may be variously changed depending on the diameter of the pipe forming the supply path 23. For example, a filter having an outer diameter of about 50 to 100 mm and a length of about 200 mm can be used.

  In this example, as shown in FIG. 1 (B), in the supply path 23, the bottom 1b is perpendicular to the vertical direction and the side wall 1a is in the vertical direction at a location where the refrigerant flows downward from the vertical direction. The filtration means 1 is arranged so as to be parallel to the. In particular, the bottom 1b is disposed on the downstream side of the refrigerant. In FIG. 1 (B), black triangular arrows indicate the direction of refrigerant flow. The same applies to FIG. 2 described later.

  In the connection structure of the present invention having the above configuration, when the refrigerant is transported from the cooling system (not shown) to the supply pipe 23, the refrigerant passes through the filtering means 1 and is supplied to the refrigerant tank 21. At this time, when the foreign matter f is transported together with the refrigerant, the passage of the foreign matter f is blocked by the side wall portion 1a, and the foreign matter f sinks and stays in the bottom portion 1b due to the transport pressure of the refrigerant. Therefore, in the connection structure of the present invention, only the refrigerant from which the foreign substance f has been removed can be efficiently supplied to the refrigerant tank 21. Then, the refrigerant discharged from the refrigerant tank 21 via the discharge path 24 is subjected to temperature adjustment or the like in the cooling system, passes through the supply path 23 again, and is supplied to the refrigerant tank 21. At this time, since the foreign substance f is removed by the filtering means 1, even if dust existing in the cooling system or the like is transported together with the refrigerant, the dust is not supplied to the refrigerant tank 21. Thus, in the connection structure of the present invention, even if foreign matter exists in any of the supply path 23, the refrigerant tank 21, the discharge path 22, and the cooling system and is transported along with the refrigerant, the foreign matter is removed by the filtering means 1. It can be removed efficiently. In the connection structure of the present invention used for direct current power transmission, a direct current electric field is applied to various places. In such a place where a direct current electric field is applied, metallic scraps are easily accumulated due to a so-called dust collection effect. And depending on an accumulation location, the malfunction that a creepage failure will arise arises, but in the connection structure of this invention, the said malfunction can be effectively reduced by providing a filtration means.

  In the above description, the supply means 23 is provided with the filtering means 1. However, the supply means 23 may be provided in the discharge path 24, may be disposed in the refrigerant tank 21, or both the supply path 23 and the discharge path 24. It may be included. By providing a plurality of filtering means for one refrigerant flow passage, foreign matter can be captured more reliably. Further, in the above description, the supply path 23 is provided with one filtering means 1, but a plurality of filtering means 1 may be provided at an appropriate interval. Further, it is preferable that at least one of the refrigerant tank 40, the supply path 42, and the discharge path 43 is similarly provided with the filtering means 1 so that foreign matters can be removed.

The filtering means is preferably configured to facilitate maintenance such as cleaning and replacement. That is, it is preferable that the configuration be easily removable from the refrigerant flow passage. Then, next, the specific structure of the filtration means which can be attached or detached easily is demonstrated. FIG. 2 is a schematic configuration diagram showing an example in which filtering means is provided at a bent portion in the refrigerant flow passage. Considering the attachment / detachment of the filtering means, the filtering means is preferably provided in the supply path and the discharge path. In particular, it is preferable that the portion protrudes from the junction box. Further, if the filtering means is disposed in a place where the refrigerant flow direction changes in the supply path or the discharge path, for example, a position bent from the horizontal direction to the vertical direction or a position bent from the vertical direction to the horizontal direction, the attachment or detachment is possible. Easy to configure. For example, as shown in FIG. 2, as the inner pipe 50 of the supply path or the discharge path, a horizontal inner pipe 51 in which the refrigerant flows in the horizontal direction, a vertical inner pipe 52 in which the refrigerant mainly flows in the vertical direction, a horizontal inner pipe 51 and A bent inner pipe 53 that connects the vertical inner pipe 52, and the bent inner pipe 53 is detachable from the horizontal inner pipe 51 and the vertical inner pipe 52, and the filtration means 1 is attached to the bent inner pipe 53. Use the thing. In this example, one end of the bent inner tube 53 is a connection end with the horizontal inner tube 51 and the other end is a connection end with the filtering means 1. In the filtering means 1, a flange 1c is provided on the opening side of the side wall portion 1a so as to protrude in the outer peripheral direction, and is fixed to the vertical inner tube 52 via the flange 1c. With this configuration, the diameter R ₁ of the flange 1c is larger than the outer diameter of the side wall portion 1a. The bent inner tube 53 may be a rigid tube, but if a part of the bent inner tube 53 is a flexible bellows tube as shown in FIG. 2, the filtering means 1 can be easily attached.

  The horizontal inner pipe 51, the vertical inner pipe 52, and the bent inner pipe 53 are provided with flanges at the openings, respectively, the flange of the horizontal inner pipe 51 and the flange of the bent inner pipe 53, and the flange 1c of the filtering means 1 and the vertical inner pipe. The flanges of the pipes 52 are overlapped and connected and fixed by a fastening member such as a bolt. It is preferable to arrange a sealing material such as a metal O-ring between the flanges. With the above connection, the filtering means 1 is disposed in the inner tube 50. With this arrangement, the refrigerant that has passed through the horizontal inner pipe 51 passes through the bent inner pipe 53 and is transported to the filtering means 1, passes through the side wall portion 1 a of the filtering means 1, and is transported to the vertical inner pipe 52. On the other hand, the foreign substance f transported with the refrigerant sinks and stays at the bottom 1b due to the transport pressure of the refrigerant.

The horizontal inner pipe 51, the filtration unit 1 and the bent inner pipe 53, and the outer pipe 54 in which the vertical inner pipe 52 is housed are configured to be able to open the bent portion. In the example shown in FIG. 2, an opening is provided in the upper direction in the outer tube 54, and a lid 54a that closes the opening is provided. A flange 54b is provided in the opening of the outer tube 54. The flange 54b and the lid 54a are overlapped, the opening is closed with a fastening member such as a bolt, and the fastening member is removed, whereby the lid Open 54a and open the opening. It is preferable to arrange a sealing material such as a metal O-ring between the lid portion 54a and the flange 54b. The diameter R ₀ of the opening of the outer tube 54 is made larger than the diameter R _{1 of the} flange 1c included in the filtering means 1. With this configuration, the lid 54 a of the outer tube 54 can be opened, and the integrated body of the filtering means 1 and the bent inner tube 53 can be easily removed from the outer tube 54. In FIG. 2, the bent portion of the outer tube 54 where the integral part of the filtering means 1 and the bent inner tube 53 is disposed is larger than the other portions, but it is of course possible to have the same size. Further, the outer tube 54 is provided with a vacuum port 54c so that the inside of the outer tube 54 can be evacuated.

In the example shown in FIG. 2, the maintenance work procedure of the filtering means 1 will be described.
(1) When the superconducting cable is energized and the refrigerant is flowing through the refrigerant flow passage, the refrigerant circulation is stopped.
(2) The inside of the outer tube 54 is returned from the vacuum to the atmospheric pressure by the evacuation port 54c.
(3) Remove the lid 54a from the outer tube 54, remove the connection between the horizontal inner tube 51 and the bent inner tube 53, remove the connection between the vertical inner tube 52 and the filtering means 1 (flange 1c), and remove the connection between the filtering means 1 and the bent inner tube 53. The integral with the tube 53 is taken out from the outer tube 54. The refrigerant in the inner pipe 50 is discharged.
(4) Check the dirt on the filtration means 1 and the retention of foreign matter. Examples of the confirmation work include visually observing the filtering means 1, using a fiberscope or the like, or checking for foreign matter to come out or shaking the integrated object. When the length of the filtering means is about 200 mm, the length from the opening of the bent inner tube 53 to the bottom 1b of the filtering means 1 is at most about 300 mm and can be easily checked visually. If foreign matter is accumulated by this confirmation, the filtering means 1 is washed or replaced.
(5) The unitary object is inserted into the outer tube 54 and fixed to the horizontal inner tube 51 and the vertical inner tube 52.
(6) After closing the lid portion 54a, evacuation is performed from the evacuation port 54c to start circulation of the refrigerant.

  In the above-described configuration, it is necessary to stop the circulation of the refrigerant and to discharge the refrigerant from the transport pipe or the like for the maintenance of the filtering means 1, which takes time. Therefore, it is preferable to provide valves on the refrigerant introduction side and the refrigerant discharge side of the filtration means 1 so that the filtration means 1 can be maintained without discharging the refrigerant from the transport pipe or the refrigerant tank. For example, in the case of the pipe shown in FIG. 2, a valve may be provided near the end on the filtration means side in the horizontal inner pipe 51 and on the lower side of the filtration means 1 in the vertical inner pipe 52. These valves are opened during normal energization so that the refrigerant can be supplied to the refrigerant tank and discharged from the refrigerant tank, and are closed when the filtration means 1 is maintained, and the refrigerant is supplied to the refrigerant tank. Supply and discharge of the refrigerant from the refrigerant tank are stopped. At this time, the refrigerant tank is in a state where the refrigerant does not flow, but the state in which the refrigerant is filled is maintained. Note that the vacuum state of the vacuum chamber of the connection box is not broken during maintenance. On the other hand, a partition wall or the like is provided between the outer tube that covers the vicinity of the location where the filtering means is provided in the inner tube and the outer tube that covers other locations of the inner tube, and independent vacuum layers are provided in both tubes. It is set as the structure which has. With this configuration, even if the flow of the refrigerant is stopped during maintenance, the vacuum state is maintained except in the vicinity of the attachment portion of the filtering means, so that the temperature rise of the refrigerant can be reduced. And after maintenance, it is only necessary to evacuate the vicinity of the place where the filtering means is attached, so workability is good.

  Also, instead of a single-system transportation route as shown in FIG. 2, a plurality of transportation routes are formed by branching the piping and paralleling a plurality of branching routes. When the valve is provided on the upstream side and the downstream side of the filtering unit, the filtering unit can be maintained while the refrigerant is circulating in the refrigerant tank. That is, during normal operation, one of the branch passage valves is opened to supply / discharge the refrigerant, and the remaining branch passage valves are closed, and maintenance of the filtering means provided in the branch passages used in normal times is performed. When performing, the valve of this branch path is closed and the valve of any remaining branch path is opened. By using the branch path with the valve opened in this way for the circulation of the refrigerant, the refrigerant tank is supplied / discharged without delay, and the filtration means is maintained without stopping the refrigerant circulation. be able to. In addition, a branch path not provided with a filtering means may be provided, and this branch path may be used at the time of maintenance, but foreign substances are always removed by providing a filtering means in each branch path. be able to. Each branch path is preferably configured to have an independent vacuum layer as described above.

  In the above description, the case of a terminal connection structure has been described. However, the connection structure of the present invention can also be applied to an intermediate connection for connecting superconducting cables. FIG. 3 is a schematic configuration diagram showing an intermediate connection structure in the connection structure of the present invention. In this intermediate connection structure, the basic configuration is the same as the conventional configuration shown in FIG. That is, this intermediate connection structure includes a cable core 61A drawn from the end of one superconducting cable 60A to be connected, a core 61B drawn from the end of the other superconducting cable 60B, and ends of both cores 61A and 61B. And an intermediate connection box 70 in which is stored. In this example, each of the superconducting cables 60A and 60B is a three-core cable that is formed by twisting three cable cores having the same configuration as in Example 1, and three connection points are stored in one connection box 70. (In FIG. 3, there are only two connection points, but there are actually three). The cores 61A and 61B are stepped off to expose the superconducting conductors 62A and 62B, and are connected by an intermediate connection sleeve 63. A reinforcing insulating layer 64 is provided on the outer circumferences of the connected superconducting conductors 62A and 62B and the sleeve 63. The reinforcing insulating layer 64 has a configuration in which an end thereof is tapered so as to taper away from the sleeve 63, and the concentration of the electric field at the end is controlled. In addition, a shield layer (not shown) was provided on the outer periphery of the reinforcing insulating layer 64 with a conductive material such as copper, thereby forming an electric field shielding structure. The intermediate connection box 70 includes a refrigerant tank 71 in which a refrigerant such as liquid nitrogen for cooling the superconducting conductors 62A and 62B is circulated, and a vacuum tank 72 disposed on the outer periphery of the refrigerant tank 71. The refrigerant tank 71 includes a supply path 73 for supplying a refrigerant and a discharge path 74 for discharging the refrigerant. In this example, a stainless steel disk-like member 65 having a size suitable for the inner periphery of the refrigerant tank 71 is provided in the refrigerant tank 71, and the disk-like member 65 allows superconducting the space in the refrigerant tank 71. The space is divided into a space A on the cable 60A side and a space B on the superconducting cable 60B side so that the refrigerant does not flow between the spaces A and B. Therefore, the supply path 73 and the discharge path 74 are provided in each of the spaces A and B. In addition, by providing the filtering means described in the first embodiment in at least one of the supply path 73 and the discharge path 74, foreign substances can be captured. In this example, a shield layer is provided on the outer periphery of the reinforcing insulating layer 64 to form an electric field shielding structure, and even if metallic foreign matter accumulates on the surface of the shield layer, creeping damage is unlikely to occur. However, if this shield layer is broken and dust enters the inside of the shield layer, there is a risk of electrical instability. On the other hand, in the connection structure of the present invention, such a problem can be prevented by providing the filtering means. If this filtering means is provided at a location arranged outside the connection box 70 in the supply path 73 and the discharge path 74, operations such as maintenance can be easily performed.

  In the intermediate connection structure shown in this example, the connection part between the superconducting conductors 62A and 62B is fixed to the connection box 70 (refrigerant tank 71) by the disk-shaped member 65. Specifically, a connection conductor 66 made of a copper rod was interposed between the superconducting conductors 62A and 62B, and the superconducting conductors 62A and 62B were connected using the intermediate connection sleeve 63 and the connection conductor 66. The intermediate connection sleeve 63 has a conductor-side insertion hole into which a former and a superconducting conductor 62A (62B) can be inserted at one end, and a copper cylinder having a connection conductor insertion hole into which the connection conductor 66 can be inserted at the other end. A member having a multi-contact inside the connection conductor insertion hole was used. The connection conductor 66 has a solid insulating member 67 made of an epoxy resin molded body mounted on the outer periphery thereof. This solid insulating member 67 is inserted and disposed in an insertion hole provided in the disc-like member 65, and the bolt 69 is tightened with the flange portion 67a provided in the intermediate portion sandwiched between the disc-like member 65 and the pressing member 68. As a result, the disc-shaped member 65 is fixed. Then, the disk-shaped member 65 is fixed to the refrigerant tank 71 by welding or the like, so that the connection portion of the superconducting conductors 62A and 62B is fixed to the refrigerant tank 71.

  Further, in this example, the junction box 70 used is a combination of a pair of half crack pieces that can be divided in the longitudinal direction of the cable core (left and right in FIG. 3). Furthermore, in this example, in order to pull out the three cable cores from one superconducting cable, a holding tool 80 that can be held in a state where the cores are widened is arranged in the refrigerant tank 71 so as to facilitate the connection work. . In addition, in this example, a short-circuit portion 90 for short-circuiting the external superconducting layer included in the three-wire cable core drawn from the same superconducting cable is provided.

  The connection structure of the DC superconducting cable of the present invention can be applied to any of intermediate connection for connecting the superconducting cables and terminal connection for connecting the superconducting cable and a normal conducting device arranged on the room temperature side. Such a connection structure can be suitably used in the construction of a superconducting cable line that performs DC power transmission.

(A) is a schematic configuration diagram showing a termination connection structure in the connection structure of the present invention, and (B) is a schematic configuration diagram showing a state in which filtering means is arranged in a supply path. In this connection structure, it is a schematic block diagram which shows the state which has arrange | positioned the filtration means in the refrigerant | coolant flow path, and shows the example which provides a filtration means in the location bent in the supply path or the discharge path. In this connection structure, it is a schematic block diagram which shows an intermediate | middle connection structure. It is a schematic block diagram which shows the intermediate connection structure of the conventional superconducting cable. It is a schematic block diagram which shows the termination | terminus connection structure of the conventional superconducting cable.

Explanation of symbols

1 Filtration means 1a Side wall 1b Bottom 1c Flange
10 Cable core 11 Superconducting conductor 12 End connection sleeve 13 Lead
14 Joint 15 Bushing 15a Conductor 15b Solid insulation layer
16a, 16b Reinforced insulation layer 17 Insulation spacer 20 Termination junction box 21,41 Refrigerant tank
22,42 Vacuum chamber 23,43 Supply channel 23a Inner tube 23b Outer tube 24,44 Discharge channel
25 Ground wire 30 Steel pipe 31 Cover 40 Auxiliary junction box
50 Inner pipe 51 Horizontal inner pipe 52 Vertical inner pipe 53 Bent inner pipe 54 Outer pipe
54a Lid 54b Flange 54c Vacuum port
60A, 60B superconducting cable 61A, 61B cable core 62A, 62B superconducting conductor
63 Intermediate connection sleeve 64 Reinforcing insulation layer 65 Disk-shaped member 66 Connection conductor
67 Solid insulation member 67a Flange 68 Holding member 69 Bolt
70 Junction box 71 Refrigerant tank 72 Vacuum tank 73 Supply path 74 Discharge path
80 Holder 90 Short circuit
100A, 100B Superconducting cable 101,101A, 101B Cable core
102,102A, 102B Superconducting conductor 103 Intermediate connection sleeve
104,104a, 104b Reinforcing insulation layer
110 Intermediate connection box 111 Refrigerant tank 112 Vacuum tank
150 Terminal connection sleeve 151 Lead part 152 Joint part
153 Bushing 153a Conductor 153b Solid insulation layer
200 Terminal box 201,211 Refrigerant tank 202,212 Vacuum tank 203,213 Supply path
204,214 Discharge path 205 Ground wire 210 Auxiliary junction box 220 Steel pipe

Claims (8)

A superconducting conductor provided in the superconducting cable and a connection target of the superconducting conductor are housed, and a connection structure of a DC superconducting cable comprising a connection box in which a refrigerant for cooling the superconducting conductor is circulated.
The connection box is connected to a supply path for supplying the refrigerant into the box and a discharge path for discharging the refrigerant outside the box,
A direct current superconducting cable connection structure comprising a filtering means for removing foreign substances in the refrigerant in a refrigerant flow path extending from the supply path to the discharge path.   2. The DC superconducting cable connection structure according to claim 1, wherein the filtering means is disposed in at least one of the supply path and the discharge path.   2. The connection structure for a DC superconducting cable according to claim 1, wherein the filtering means is made of a material that can be used in a refrigerant temperature region and can withstand a transport pressure during refrigerant circulation.   2. The DC superconducting cable connection structure according to claim 1, wherein the filtering means includes a filter having a mesh size of 2 to 300 μm.   2. The connection structure for a DC superconducting cable according to claim 1, wherein a plurality of filtering means are arranged in multiple stages in the refrigerant flow passage.   3. The DC superconducting cable connection structure according to claim 2, wherein a valve is provided on the refrigerant introduction side and the refrigerant discharge side in the filtering means.   The DC superconducting cable connection structure according to any one of claims 1 to 6, wherein the connection object is a room temperature side conductor lead-out portion.   7. The DC superconducting cable connection structure according to claim 1, wherein the connection target is a superconducting conductor provided in another superconducting cable.

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