BUSBAR SYSTEM ELEMENT WITH A SUPRACONDUCTOR STRIP AND A CONNECTOR, AS WELL AS A BUSBAR WITH A NUMBER OF SUCH BUSBAR SYSTEM ELEMENTS

Description

[0001] The invention relates to a busbar system element comprising a superconducting strand extending along the busbar system element and a connector at the end of the superconducting strand for electrically connecting the superconducting strand to a further superconducting strand of another busbar system element with a mating connector. It further relates to a busbar comprising a plurality of such busbar system elements.

[0002] The problem lies in the simple and reliable connection of electrical busbar system components within a busbar system consisting of multiple components. These components essentially comprise an elongated, tubular, vacuum-insulated housing or "cryostat" open at both ends, through which a strand of superconductors is routed. The superconductors, or the strand, protrude from both ends of the housing. In the prior art, during installation of the entire system, the protruding superconductors are electrically connected to each other using connecting components, creating a continuous conductor path. The housing is then closed at the connection points, resulting in a completely enclosed busbar system.The busbar system is used for high-current purposes, where direct or alternating current in the range of kiloamperes to megaamperes is to be transmitted and whose conductor material consists essentially of high-temperature superconductors (HTSL) that can conduct direct current without loss in the nominal temperature range below the so-called transition temperature.

[0003] These HTSLs are not in the classic wire form, but rather as strip material in standard widths of 4, 10, and 12 mm, with planned widths up to 100 mm, and in thicknesses from 20 to 300 µm. To achieve the required high current-carrying capacity of the system element, they are bundled into stacks. One or more stacks form a strand. One or more strands provide the current-carrying capacity of the entire system.

[0004] The following describes commercially available high-temperature superconducting tapes (HTSL tapes) that, with all the features mentioned here, can be part of the invention. HTSL tapes essentially consist of a thin ceramic layer built up on a metallic support or substrate, which becomes superconducting when the so-called transition temperature is undershot. The composition of the layers of an HTSL tape varies depending on the requirements, manufacturer, or manufacturing process. Typically, the superconducting layer is coated with a thin silver layer of 0.5–2 µm. The finished HTSL tape can additionally be coated with a copper stabilizer, either electroplated or by lamination. Furthermore, the conductor can be coated with solder, either electroplated or by immersion in a bath.For electrical contact with other HTSL tapes, the metallic layers made of highly conductive material, which are directly contacted on the superconducting ceramic layer, are always recommended, as the substrate is considered to have a high resistance in comparison. As a distinguishing feature in the description, the low-resistance HTSL side of the tape is referred to as the "good side." In the case of a complete copper coating, with sufficient layer thickness, the current can also be conducted from the "good side" to the back, i.e., the metallic substrate. However, this is subject to ohmic resistance, which is determined by the coating material and the layer thickness.

[0005] In the production of HTSL tapes, the superconducting layer is typically applied to one side of the support material or substrate using physical or chemical processes. Nickel-based alloys (HASTELLOY C-276) or tungsten-nickel alloys are suitable as support materials. Tungsten-nickel alloy support tapes undergo processes such as annealing and may also be pre-structured. Due to the manufacturing process, they are therefore relatively thin, typically <= 60 µm, and soft. This makes them very fragile and easily damaged or degraded during subsequent handling. To improve handling and current-carrying capacity, these conductors are laminated together with their respective back-side supports. This creates a double conductor with improved stiffness, current-carrying capacity, and handling. Unlike a single conductor, the double conductor has two good sides.In some cases, the superconducting layer of the standard single conductor underlying the double conductor is produced using chemical processes and exhibits high pressure sensitivity in soldering tests. The conductor then degrades even under comparatively low pressure. Therefore, this conductor requires different conditions for both soldering and current transmission from one connector segment to the next compared to the single-ended conductor based on a Hastelloy substrate and physical coating. This will be discussed separately below.

[0006] When HTSL strips are stacked, they influence each other via their self-generated magnetic fields. The current-carrying capacity of each individual HTSL strip decreases the stronger the magnetic field to which it is exposed at its stacking position. This effect must always be considered when calculating the current-carrying capacity of the overall system, but for the sake of simplicity and clarity, it is omitted from the following description. To avoid negatively impacting the overall system's current-carrying capacity, the spacing between the individual HTSL strips in the connector must not be smaller than in the rest of the track. No bottleneck should occur; however, widening of the spacing is not critical and does not pose a problem.

[0007] For the transmission of high to very high currents in the kiloampere to megaampere range, high-temperature superconductivity applications require very low electrical resistance at the junctions of the superconductors, due to the power loss equation Pv = I2 < xR. In the kiloampere range, this resistance should be less than 5 nanoohms (5 nΩ), otherwise excessive heat generation would necessitate costly cooling of the HTSLs. The required higher cooling capacity would increase the system's operating costs. Furthermore, the current-carrying capacity of the HTSLs would be reduced, requiring more HTSL bands, which in turn would significantly increase system costs. This extremely low resistance can only be achieved with a superconducting junction or at least an extremely low-resistance metallic-material connection between the good sides of the HTSL bands.Soft soldering with low-melting-point solders is suitable for this purpose, as it allows for the creation of very thin transition layers without damaging the HTSL through thermal degradation caused by excessively high, prolonged temperatures and thus impairing its current-carrying capacity. A resistance value on the order of 100 nΩ per square centimeter of contact area between two HTSL strips can be achieved with reasonable effort. Therefore, by increasing the contact area and connecting many HTSL strips in parallel, a low overall resistance can be achieved. For example, with a 5 cm overlap length and 50 parallel 12 mm wide strips, a theoretical total resistance of only 0.33 nΩ is obtained.

[0008] To minimize the costs of using HTSL tapes, efforts are made to utilize even the portion of the critical current exceeding the minimum current-carrying capacity. Therefore, the aim is to distribute the current energetically optimally across the HTSL tapes in each system element of the busbar system. This requires that compensating currents be able to flow between the superconductors at the transition from one system element to the next. The average current-carrying capacity of the individual HTSL tapes is referred to as the critical current Ic. It generally exceeds the minimum current-carrying capacity Icmin required by suppliers, which results from locally confined areas with dips in current-carrying capacity. These dips range from a few tenths of a millimeter to a few millimeters in size. HTSL material with few defects per 1,000 meters or very small dips is considered to have good homogeneity.Numerous defects or larger dips indicate inhomogeneous material. Very large dips are cut out. Even with inhomogeneous material, therefore, only a relatively small number of defects occur on the few-meter-long HTSL band sections of the system elements. These defects could limit the current-carrying capacity and prevent the full average current-carrying capacity Ic from being utilized. However, they cannot be completely eliminated. It is therefore necessary to enable the redistribution of currents exceeding the Icmin at the connection points from one HTSL band with Ic to another with Ic, which entails increased connection complexity.

[0009] The HTSL stacks or strands that conduct the current through the superconducting busbar system consist of numerous individual HTSL strips, ranging from about twenty to several hundred, depending on the temperature and the required current. Connecting each individual HTSL strip on a construction site while maintaining high quality standards presents a costly challenge. This is especially true when dealing with a large number of HTSL strips. Therefore, another objective is to enable a simple, fast, safe, and high-quality connection on-site by ensuring the demanding preparation of the connection process under defined conditions through prefabrication in suitable workshops.

[0010] WO 2016 / 077662 A1, JP 2015 211009 A, JP H07 263045 A, JP 2015 006076 A reveal the connection of HTSL cables.

[0011] The following publications reveal a generic busbar: BN SORBOM ET AL: "ARC: A compact, high-field, fusion nuclear science facility and demonstration power plant with demountable magnets", FUSION ENGINEERING AND DESIGN., Vol. 100, November 2015 (2015-11), pages 378-405, M Takayasu ET AL: "Termination Methods for REBCO Tape High-Current Cable Conductors", MANGIAROTTI FJ ET AL: "Demountable Toroidal Field Magnets for Use in a Compact Modular Fusion Reactor", JOURNAL OF PHYSICS: CONFERENCE SERIES, INSTITUTE OF PHYSICS PUBLISHING, BRISTOL, GB, Vol. 507, No. 3, May 12, 2014 (2014-05-12), page 32030.

[0012] It is therefore an object of the present invention to provide an improved busbar system element with a connecting piece and a busbar with a plurality of such busbar system elements.

[0013] This problem is solved by a busbar system element with a connecting piece having the features of the main claim and a busbar with a plurality of such busbar system elements having the features of the dependent claim. Advantageous embodiments are the subject of the dependent claims.

[0014] The proposed busbar system element comprises a stabilizing housing that also forms the cryostat and extends along the busbar system element. A superconducting strand runs inside the housing and preferably extends beyond its ends. As described in the introduction, the superconducting strand has a multitude of parallel HTSL bands. Parallel generally means that the bands are stacked, possibly maintaining certain distances to prevent the magnetic field from unduly reducing the current-carrying capacity of the overall system. Several such stacks can, in turn, be arranged side by side. Each of the HTSL bands has a good side with a ceramic material as the HTSL and a back side facing away from the good side.This formulation therefore covers both the single-conductor tape with a carrier coated on one side with HTSL, and the double-conductor tape with HTSL layers on both sides of the HTSL tape. Therefore, in the case of the double-conductor tape, one of the two good sides also forms the reverse side.

[0015] Furthermore, a connector is provided at the end of the superconducting strand, which typically extends beyond the housing. This connector serves to electrically connect the superconducting strand to another superconducting strand of a further busbar system element with a matching mating connector. In the prior art, the end of each HTSL strip forms such a connector, but this requires laborious and difficult-to-reproducibly soldering each strip individually.

[0016] According to the invention, a special connecting piece is provided as a unique feature, to which the back ends of the HTSL tapes are attached. This feature allows contact without having to handle each end of the HTSL tape individually.

[0017] The connector is designed such that two connectors – preferably of the same type – can be joined in a direction perpendicular to the longitudinal axis of the busbar system element. Unlike known plug-in systems, no rails need to be moved longitudinally during installation, or even less efficiently, when removing the connector from an installed busbar section.

[0018] This enables methods for space-saving, particularly low-resistance connection of HTSL strips to one another. The connector according to the invention enables, for the first time in superconductor technology, the fast, simultaneous, and reliable connection of a large number of HTSL strips using a "face-to-face" technique, without the need for complex splicing work during on-site installation by expensive, experienced application specialists. The connector allows system elements of a fully assembled system to be installed or removed perpendicular to the longitudinal axis without having to dismantle adjacent elements, which has a very positive impact on the costs associated with a potential defect in a system element over long distances. The HTSL ends, which are spliced ​​and fixed at the factory under controlled conditions within the connector, form a current bridge with large-area contacts between the HTSL and, if applicable, current equalization elements.The handling-sensitive HTSL individual strips of the unstable stack are therefore combined to form a pluggable HTSL contact.

[0019] According to the invention, the connecting piece has a plurality of comb-like wedges arranged parallel to one another, the inclined side surfaces of which converge at an angle preferably less than 10°. Similar to two interlocking racks, the comb teeth interlock. Since the rear ends of the HTSL straps are attached to the side surfaces of the wedges, a wedge-typical force amplification occurs: A slight compression of the identical connecting pieces placed one on top of the other generates a strong contact pressure on the overlapping HTSL straps.

[0020] If the width of the wedges extends along the length of the end of the HTSL strips, it is possible to connect two connectors in a direction perpendicular to the longitudinal axis of the busbar system element. Furthermore, the width of the wedge, which here corresponds to the length of the HTSL strip held in the connector, defines the length and thus the cross-section of the overlap. This determines the current-carrying capacity and the electrical resistance of the connection.

[0021] To achieve pluggability of the connection, the spacing of the parallel wedges with the attached HTSL strips on the connector is preferably designed as follows: If a similar mating connector equipped with HTSL strips is electrically connected to the connector in a contact zone, then at least one mating wedge of the mating connector should fit into the space between adjacent wedges of the connector. In this case, at least in the contact zone, the good surfaces on the side faces of the mating wedge rest against the respective good surfaces on the side faces of the adjacent wedges. A contact zone is the area in which, when the connection between two contact elements is made, the good surfaces of two overlapping HTSL strips are in direct contact, possibly with the exception of a solder layer and / or other thin layers typical of HTSL strips.

[0022] Preferably, if the connector is designed such that an electrical connection can be established by movement and pressure in the wedge direction relative to a similar mating contact, the aforementioned force amplification results, which is particularly beneficial to the solder distribution proposed later. The low assembly force produces a high contact pressure and is also suitable, if necessary, as a connector without soldering.

[0023] Preferably, the tips of the wedges are flattened to make them more compact and robust. In the case of HTSL single-conductor strips, this improves the accuracy of the connection. When using HTSL double-conductor strips, this zone constitutes the secondary contact zone, which will be explained later.

[0024] What is particularly noteworthy, however, is that the contact surfaces are soldered together to ensure compliance with the minimum resistance values ​​discussed in the introduction. For this purpose, the HTSL strips already have a solder layer applied at the factory, at least in the section designated for electrically conductive connection with a similar mating HTSL strip. This section also corresponds to the minimum width of the wedges on which the HTSL strips are mounted. To connect the strips, the pressed-together contact pieces are heated to melt the solder layer. This results in gentle contacting of the pressure-sensitive HTSL strips, as there is virtually no relative movement once the pressure is applied. The solder, which is liquid during the soldering process, acts as a kind of "hydrodynamic bearing" during movement, similar to the oil in a plain bearing at its rated speed.When the contact areas are placed, the movement stops, and the HTS conductors are fixed in the contact zone after the solder has cooled. A precisely preheated, thermally controlled soldering jig allows the necessary amount of heat to be applied—sufficient for soldering but low enough to prevent thermal damage to the HTSL tape. Monitoring the temperature of the HTSL over time is crucial, as degradation can occur at temperatures above 150°C for durations exceeding one minute. The preheated soldering jig ensures uniform heat distribution, as all conductors are soldered simultaneously. This jig also allows for consistent contact pressure during soldering, which is essential for pressure-sensitive HTSL tapes, especially those on NiW substrates.

[0025] Furthermore, it can be advantageous if the width of the wedges extends beyond the width of the contact zone, as does the solder layer. Preferably, these wedges extend over the entire length along which the HTSL strips are attached to the side surfaces. The width of the wedges, or the solder layer, thus extends beyond the contact zone itself, creating space for a simple technical implementation of current equalization: For this purpose, the connector has an electrically conductive equalization element that electrically connects the good surfaces of the HTSL strips attached to the inclined side surfaces of the parallel wedges. The equalization element is inserted where the HTSL strips are not intended to overlap, i.e., outside the contact zone. The equalization element has a geometry comparable to that of the mating contact piece and is also designed to be inserted between the good surfaces of the HTSL strips.The current equalization piece therefore has wedges that make electrically conductive contact between two opposing adjacent surfaces. These wedges are advantageously soldered to the surfaces, but this soldering need not be done on-site; it can be done at the factory under well-controlled conditions. To prevent the current equalization piece from coming loose when the contact pieces are soldered together on-site, either the melting temperature of the solder is at least 20 K higher than the melting temperature of the solder layer on the good side of the HTSL strips in the section intended for electrically conductive connection with HTSL strips of a similar mating connection, or, if the solders have the same melting temperature, the current equalization pieces are sufficiently cooled down during the soldering of the contact zones.

[0026] If several parallel superconducting strands are provided, each with a connector at its end, and a current equalization element is attached to each connector, the current equalization elements can preferably also be electrically connected to each other. This creates a current equalization between the strands.

[0027] The following features apply to the use of single-conductor HTSL strips with only one good side. The reverse side of each HTSL strip serves as a carrier or substrate. Therefore, the reverse side has a relatively high resistance and does not contribute to current-carrying capacity. Preferably, the connector provided with HTSL strips is designed such that, when electrically connected to a similar mating connector provided with HTSL strips in the contact zone, the connector and mating connector support each other exclusively in the contact zone. This ensures that an optimal amount of solder is squeezed out of the contact zone during soldering, minimizing the contact resistance. Current flow thus occurs exclusively in the area of ​​the overlapping HTSL strips. If the depth of the wedge is 5–25% greater than the width of the HTSL strips, a space is created to accommodate the displaced solder.

[0028] The following characteristics apply to the use of dual-conductor HTSL tapes with two good sides. The reverse side of each HTSL tape is also designed as a good side, usually with at least one or two layers of a carrier in between. Since the reverse good side must also be electrically connected to the mating contact, the reverse sides of the HTSL tapes are also electrically conductively connected to the side surfaces, e.g., by soldering. However, the interconnected contact pieces must also be connected to each other in a secondary contact zone beyond the primary contact zone.This requires that the connector be electrically conductive, at least in the area of ​​the wedges; and that the connector equipped with HTSL strips is such that, when electrically connected in the contact zone to a similar mating connector equipped with HTSL strips, the connector and the mating connector can support each other in secondary contact zones away from this contact zone and be electrically connected to each other. These secondary contact zones can also be soldered together. If the depth of the wedge is only 1-5% greater than the width of the HTSL strips, there is a possibility that the free end of the wedge presses against the material of the mating contact, thus forming the secondary contact zone.

[0029] The following characteristics apply to the use of single-conductor and / or dual-conductor HTSL tapes.

[0030] Preferably, a busbar with a plurality of busbar system elements according to the invention is proposed, which are connected to one another at their respective connecting pieces. The overlapping good sides of the ends of the HTSL strips are electrically connected to one another by soldering the solder layer. In the case of double-conductor HTSL strips, the connecting pieces are optionally soldered to one another in the area of ​​the secondary contact zones.

[0031] Since contact resistances must be minimized in the high-current applications described here, a skilled person would normally only connect HTSL tapes of the same width with an overlap, for example, 10 mm with 10 mm. Surprisingly, tests have shown that this influence is hardly relevant in practice, provided that the width of the narrower tape is at least 50%, preferably 70%, of the width of the wider tape. This also applies when transitioning from single conductors to twin conductors. This finding allows, for reasons of economy or availability, the transition between HTSL tapes from different manufacturers, batches, and dimensions.

[0032] In general, the principle of the invention consists of a specific arrangement of the electrical contact zones of a plurality of electrically connected planar superconductors, which are arranged on connecting pieces. The contact zones formed by the planar superconductors are arranged at an angle of less than 20°, preferably 10° and greater than 1° to each other.

[0033] Previously, it was described that an electrical connection between adjacent connectors was made directly; that is, the wedges of the connectors were interlocked directly into one another for electrical contact. However, due to the sensitivity of the HTSL strips located on the sides of the wedges, the wedges must be brought together very carefully to prevent damage to the HTSL strips. Since the connectors are connected to longer busbar system elements, this connection requires considerable force, making damage possible. Therefore, a separate coupling piece is proposed below, which can be used to connect the previously described and completely unchanged connectors.However, these are not directly plugged into each other: The coupling piece functions exactly like the previously described connector, with the sole difference that the HTSL strips applied to the side surfaces serve only to electrically connect the HTSL strips of two adjacent connectors. Because the coupling piece is small and light, it can be used more precisely.

[0034] The two connecting pieces to be coupled are arranged one behind the other in their longitudinal axis direction and face each other end to end, with the comb-like wedges arranged parallel to each other aligned.

[0035] The connecting pieces to be coupled, arranged in this manner, are then joined by the coupling piece, which has a multitude of comb-like, parallel wedges running lengthwise along the coupling piece. Additional HTSL bands are provided on the side surfaces, thus corresponding to the construction of the connecting pieces.

[0036] The coupling piece can be inserted with its wedges into the spaces formed by the aligned wedges of the connecting pieces. This ensures that the good sides of the subsequent HTSL strips electrically connect the good sides of the aligned HTSL strips.

[0037] The inventive method for connecting two busbar system elements comprises the following steps: Arranging two busbar system elements one behind the other in their longitudinal axis direction; aligning at least one busbar system element so that the connecting pieces (41, 51) face each other end-to-end; aligning at least one busbar system element so that the comb-like wedges of the two connecting pieces (41, 51) arranged parallel to each other are aligned; providing a coupling piece (100) with a plurality of comb-like wedges extending in the longitudinal direction of the coupling piece and arranged parallel to each other, the inclined side surfaces (144) of which converge at an angle preferably less than 10°, wherein the coupling piece (100) has further HTSL strips (160) on the side surfaces (144), which comprise a good side with a ceramic material as HTSL and a back side facing away from the good side,wherein the back sides of the additional HTSL strips (160) are attached to the side surfaces (144) and the additional HTSL strips (160) extend along the width of the wedge, wherein the coupling piece is adapted to the geometry of the two connecting pieces (41, 51) so that the coupling piece (100) can be inserted with its wedges intermeshing into the spaces formed by the aligned wedges of the connecting pieces (41, 51), wherein the good sides of the additional HTSL strips (160) each electrically connect the good sides of the aligned HTSL strips (61, 62) to each other; insertion of the coupling piece (100) at an angle, first only at one of its edges, whereby only all ends of the wedges at the edge of the coupling piece are inserted into the spaces between the wedges of one of the connecting pieces (41); and subsequent pivoting of the coupling piece (100),as the rotation increases, the wedges are pivoted further and further from the edge into the spaces between the wedges of the two connecting pieces (41, 51).

[0038] This allows for a slow, controlled pivoting of the coupling piece. In particular, there is no jolting or uncontrolled application of force, as contact is established gradually. Soldering will also occur when using the coupling piece, as described above. The invention is explained below with reference to the figures.

[0039] Fig. 1 Figure 1 shows a connection point 5 of a busbar system element 1 with a housing and an open tubular cryostat 3. At the ends of the schematically depicted busbar elements 1, the superconducting strands 2 with a stack of HTSL tapes extend beyond the cryostat 3. The individual HTSL tapes are connected to each other in an overlapping manner to transfer the current from one tape to the next. According to the invention, the requirements described above are met by attaching connecting pieces 4 to the HTSL tapes of the strands 2, with which the individual HTSL tapes are materially connected.

[0040] Each superconducting strand of a system element terminates in a connecting piece 4 with a support component 41 with comb-shaped wedges arranged according to Fig. 2 On the side surfaces 44 of the wedges, the HTSL strips 6 are attached with their backs facing outwards along the entire length of the support component 41. The good side faces the opening between the wedges. For multipolar connections, the connector 4 or the support component 41 is made of non-conductive material, such as fiber-reinforced thermosets or ceramics. The HTSL strips are then attached using adhesive methods. For monopolar connections, the support component 41 is optionally made of electrically conductive, solderable material, such as copper or copper-plated aluminum. Attachment is then achieved by soldering. The spacing of the wedges is chosen such that a similar second support component 42, equipped with HTSL strips 62, is mounted as a mating contact and fits with its mating wedges into the spaces between the wedges of the first support component 41, as shown in Fig. 3 depicted.

[0041] Fig. 4a Figure 1 shows the wedges with side surfaces 44 and the HTSL strips 61 and counter-HTSL strips 62 attached to them in the form of individual conductors in detail. The side surfaces 44 are wider than the HTSL strips, so that there is still free space 43 at the wedge tip for any displaced solder. The necessary soldering technique to achieve the resistance value described above, on the order of 100 nΩcm², for the overlapping connection of the HTSL good sides requires uniform pressure on each solder joint, with the possibility of reducing the solder thickness in the joint to a minimum of approximately 3–30 µm. Excess solder should be squeezed out, thereby ensuring that flux residues, oxidation products, and gas bubbles that may be present between the joining surfaces are flushed out.Pressure applied to the back surfaces 45, 46 of the connectors 4, 41, 42, is exerted by the wedge shape of the side surfaces 44 on the HTSL strips, the solder, and the side surfaces 44 of the wedges. During soldering, the solder gap narrows, and solder then flows out laterally. Any interfering bubbles or foreign matter are flushed out. The height of the wedges is chosen so that, after the mating part 42 is mounted, there is sufficient clearance 43 in the base of the wedges. During soldering, in the event of lateral pressure on the wedges, a drainage channel is available for the flowing solder. Due to the pressure applied to the back of the connectors and the flexibility of the molten solder, the connectors can be sufficiently compressed without the tips of the wedges bearing down on the opposite surface.This is necessary to reduce the distance between the side surfaces of the wedges to such an extent that the desired minimum solder gap of only 3-30µm can be achieved unhindered.

[0042] In the case of the use of pressure-sensitive double conductors 61, 62, as in Fig. 4b As shown in detail, instead of pressure-insensitive single conductors, the requirements for the contact pieces change. It is then additionally necessary that the good sides soldered to the side surfaces 44 of the wedges can transmit their current to the double conductors of the corresponding mating contact piece 42 via the shortest possible path and thus with the lowest resistance. This is made possible by modifying the geometry of the wedges and the wedge gaps so that, in the soldered state, the wedge tips are supported on the wedge base of the mating piece by an intermediate layer of solder. The clearance 43 in the wedge foot is undesirable in this case and becomes zero. This reduces the pressure on the side surfaces of the wedges to almost zero during the soldering process, and the tooth tip is soldered to the tooth base. This results in a very short electrically conductive connection between the side surfaces 44 contacted by the double conductor.The current can thus commutate from one side to the other at the connection point. The layer thickness of the finished solder joint between the directly contacted good sides of the double conductors is greater than with the single-conductor connection described above, but still remains approximately 30% to 70% less than the original thickness of the solder strip inserted before the soldering process. Therefore, even when using the modified geometry of the connector parts together with the double conductor, solder must be forced out of the gap, resulting in a flushing effect.

[0043] The individual HTSL bands of the system elements have different current-carrying capacities. To allow equalizing currents between the superconductors within a stack connection, the good sides 64 of the individual superconductors are contacted with a metallic current equalization piece 51, as shown in Fig. 5a und 5b This creates a kind of electrical junction, and in the event of differing current-carrying capacities due to dips in the individual HTSL bands of the busbar element, a compensating current will flow at the element connection via the current equalization piece 51. Thus, the current can redistribute itself when transitioning to the next system element, where the distribution of the maximum current-carrying capacity of the HTSL bands is somewhat different. This has the advantage that not only can the guaranteed minimum current-carrying capacity of each HTSL band be utilized, but also the additional maximum current-carrying capacity, which varies statistically across each band. This increases the current-carrying capacity of the overall system, which in turn allows for a tighter design of the necessary safety margins.

[0044] In the case of the use of double conductors, the connecting pieces must be made of conductive material in order to carry a balancing current between the good sides of the double conductors soldered to the side surfaces of the wedges.

[0045] The connection resistance is determined by the contact resistance of the HTSL and the stabilizing sheath, as well as by the resistances of the material of the connector or the wedges and the solder. Due to the large contact areas of several square centimeters, the comparatively large cross-section of the back of the current equalization piece 51, and the low equalization current, the remaining power loss of the normally conductive part of the connection can be kept very low. Furthermore, the additional current equalization piece 51 acts as a further metallurgical bond for the HTSL strips 61, especially if the connector also has a solderable surface. In this case, the HTSL strips are attached to the carrier component 41 and the current equalization piece 51 is soldered in a single, cost-saving operation.This process creates a solid, easily manageable end of the HTSL stack, which can be manufactured as a pre-assembled module in suitable workshops and later used very easily to connect the system elements during installation under construction site conditions.

[0046] The assembly process between the connector and the superconductor stack is essentially divided into two temporally separate processes: The first connection is made after Fig. 5a und 5b This first step takes place in the workshops: It describes the connection of the connecting piece 41, in particular the side surfaces 44 of the wedges, to the individual HTSL bands 61 of the superconducting strand during the assembly of a system element in the workshops. In this step, the HTSL bands 61 are connected to the connecting elements 41 and the current equalization pieces 51. The connection is made using a comb-shaped auxiliary device (not shown) with preheated jaws, for example, made of aluminum.

[0047] The second process after Fig. 6 This describes the connection B between two busbar system elements during an installation on a construction site as part of the construction of a superconducting link between a power generator and a power consumer. Here, the pre-assembled connecting pieces 41, 42 of adjacent system elements are engaged and soldered together, so that an overlapping solder joint is formed between the good sides of the HTSL bands 61, 62 in the engagement area B. The heat to the newly formed solder joint in contact zone B is applied using a soldering device (not shown) with preheated, spring-loaded soldering jaws. The soldering jaws are electrically heated, and the temperature is measured and monitored. After the solder has flowed, active and vibration-free cooling is carried out.During soldering in the overlap area B, cooling jaws are mounted on the solder joints produced in the first step in the workshop, creating a significant temperature gradient between the existing solder joint and the newly formed joint. This prevents the first solder joint from unintentionally coming loose. Instead of cooling jaws, soldering with solders of different melting points, known as step soldering, can also be used for the first and second steps. In this method, the first solder joint is performed with the higher melting point solder. The temperature difference should be approximately 20 Kelvin or higher.

[0048] Fig. 7 This section explains the case of two adjacent stacks 2a and 2b with the same polarity for the busbar. For the sake of even current distribution, it is also necessary to ensure the flow of equalizing currents not only between the HTSL strips 61 themselves, but also between the stacks 2a and 2b. For this purpose, the stacks 2a and 2b are connected to each other by highly conductive equalizing contacts 5 between the contacts 41a and 41b and / or the equalizing contacts 51am and 51b. The connection is designed to compensate for the different settling of the connecting pieces during soldering. The cross-sectional area of ​​the connection depends on the expected maximum equalizing current. Several equalizing contacts (5) can also be used in parallel.

[0049] Fig 8 Figures a-c show an advantageous embodiment of the invention using an additional compact coupling piece 100. The two connecting pieces 41, 51 of the adjacent busbar system elements to be connected correspond to those shown in Figure a-c. Fig. 5 However, the two connecting pieces 41, 51 do not interlock directly, but are aligned so that their end faces are opposite each other. The comb-like wedges of the two connecting pieces 41, 51 are aligned with each other, as are the good faces of the aligned HTLS strips 61, 62, which are attached to the side surfaces of the wedges.

[0050] The coupling piece 100 according to the invention has the same cross-sectional profile as the connecting pieces 41, 51, with a plurality of comb-like wedges arranged parallel to one another in the longitudinal direction of the coupling piece, the inclined side surfaces 144 of which converge at an angle of less than 10°. The coupling piece 100 also has further HTSL bands 160 on the side surfaces 144 of the wedges, with a good side and a back side facing away from the good side. The back sides of the further HTSL bands 160 are attached to the side surfaces 144 and extend along the width of the wedges. The coupling piece 100 is adapted to the geometry of the two connecting pieces 41, 51, and thus has the same cross-sectional profile. Therefore, the coupling piece 100 can be inserted with its wedges in a combing manner into the spaces formed by the aligned wedges of the connecting pieces 41, 51.The good sides of the further HTSL bands 160 connect the good sides of the aligned HTLS bands 61,62 of the connecting pieces 41,51 to each other in an electrically conductive manner, which in . Fig. 8c shown.

[0051] The coupling piece 100 can be inserted by sliding it parallel to the plane from the in Fig. 8a shown position. Advantageously, however, the in Fig. 8b The suggested pivoting operation is as follows: The coupling piece 100 is initially inserted at an angle, namely at one of its edges 101. At first, only the ends of the wedges on the edge 101 of the coupling piece 101 are inserted into the spaces between the wedges of one of the connecting pieces 41. Then, the coupling piece 100 is pivoted around the edge 101, whereby, with increasing rotation, the wedges are pivoted further and further from the edge 101 into the spaces between the wedges of the two connecting pieces 41, 51.

Claims

1. Busbar comprising a plurality of busbar system elements, each busbar system element (1) comprising a housing (3) extending along the busbar system element; a superconductor strand (2) which runs in the housing (3) along the housing, wherein the superconductor strand (2) has a plurality of HTS strips (61, 62) running side by side, and each HTS strip comprises a good side with a ceramic material as HTS and a rear side facing away from the good side, a connector (41) at the end of the superconductor strand (2) for electrically connecting the superconductor strand to another superconductor strand of another busbar system element with a counter connector (42), wherein the rear sides of the ends of the HTS strips are attached to the connector (41), wherein the connector (41) of the busbar system elements has a plurality of wedges arranged parallel to each other in a comb-like manner in the longitudinal direction of the connector, the inclined side surfaces (44) of which converge at an angle preferably less than 10°, the rear sides of the end of the HTS strips being attached to the side surfaces (44), and the connector (41) of the busbar system elements is designed in such a way that two of the connectors can be connected in a direction perpendicular to the longitudinal axis of the busbar system element, wherein the busbar system elements (1) are connected to each other at their respective connectors, characterized in that the good sides of the HTS strips have a solder layer, at least in a contact zone (B) in which the good sides of two overlapping HTS strips are in direct contact, wherein the solder layer is provided for electrically conductive connection to HTS strips of a similar counter-connection and is preferably located over the entire length on which the HTS strips are attached to the side surfaces, and the overlapping good sides of the ends of the HTS strips are electrically conductively connected to each other by soldering the solder layer.

2. Busbar according to the preceding claim 1, characterized in that the width of the wedge extends along the course of the end of the HTS strips (61).

3. Busbar according to one of the preceding claims, characterized in that the distances between the wedges arranged parallel to each other with the HTS strips attached thereto on the connector (41) are such that when a similar counter connector (42) provided with HTS strips is connected to the connector (41) in the contact zone (B), at least one counter wedge of the counter connector fits into the space between adjacent wedges of the connector, with the good surfaces on the side surfaces of the counter wedge resting against the respective good surfaces on the side surfaces of the adjacent wedges in the contact zone.

4. Busbar according to one of the preceding claims, characterized in that the connector of the busbar system elements is designed in such a way that an electrical connection can be made by movement and pressing in the wedge direction relative to a similar counter contact piece; and / or the tips of the wedges are flattened.

5. Busbar according to one of the preceding claims, characterized in that the connector of the busbar system elements comprises an electrically conductive current equalizing piece (51) which electrically connects the good surfaces of the HTS strips attached to the inclined side surfaces of the parallel wedges, wherein preferably the current equalizing piece (51) has wedges which are in flat, electrically conductive contact on and between two opposite adjacent good surfaces, and in particular are preferably soldered to these, wherein furthermore, preferably the melting temperature of the solder is at least 20 Kelvin above the melting temperature of the solder layer which is provided on the good side of the HTS strips in the section which is provided for electrically conductive connection to HTS strips of a similar counter-connection.

6. Busbar according to the preceding claim 8, characterized in that a plurality of superconducting strands (2a, 2b) running side by side, each having a connector (41a, 41b), are provided at the end of the superconducting strands, wherein a current equalizing piece (51a, 51b) is attached to each connector, and the current equalization pieces and / or connectors (41a, 41b) are electrically conductively connected to each other via a current equalization contact piece (5).

7. Busbar according to one of the preceding claims, characterized in that the rear side of each HTS strip is also designed as a good side and, in particular, at least one or two layers of a carrier are provided in between, and the rear sides of the HTS strips are electrically conductively connected to the side surfaces, preferably soldered by a solder layer; the connector is electrically conductive at least in the area of the wedges; and / or the connector provided with HTS strips is such that when it is electrically conductively connected in the contact zone to a similar counter connector provided with HTS strips, the connector and the counter connector can support each other away from this contact zone in secondary contact zones and can be electrically conductively connected to each other; and / or the depth of the wedge is 1-5% greater than the width of the HTS strips; and / or the rear side of each HTS strip is designed as a carrier; and / or the connector provided with HTS strips is such that, when it is electrically conductively connected in the contact zone to a similar counter connector provided with HTS strips, the connector and the counter connector support each other exclusively in the contact zone; and / or the depth of the wedge is 5-25% greater than the width of the HTS strips.

8. Busbar according to one of the preceding claims, characterized in that the electrical contact zones of a plurality of flat superconductors (61, 62) electrically connected to each other are arranged on connectors (41, 51), wherein the contact zones formed by the flat superconductors (61, 62) are formed at an angle of less than 20°, preferably 10° and greater than 1° to each other.

9. Busbar comprising a plurality of busbar system elements, each busbar system element (1) comprising a housing (3) extending along the busbar system element; a superconductor strand (2) which runs in the housing (3) along the housing, wherein the superconductor strand (2) has a plurality of HTS strips (61, 62) running side by side, and each HTS strip comprises a good side with a ceramic material as HTS and a rear side facing away from the good side, a connector (41) at the end of the superconductor strand (2) for electrically connecting the superconductor strand to another superconductor strand of another busbar system element with a counter connector (42), wherein the rear sides of the ends of the HTS strips are attached to the connector (41), wherein the connector (41) of the busbar system elements has a plurality of wedges arranged parallel to each other in a comb-like manner in the longitudinal direction of the connector, the inclined side surfaces (44) of which converge at an angle preferably less than 10°, the rear sides of the end of the HTS strips being attached to the side surfaces (44), and the connector (41) of the busbar system elements is designed in such a way that two of the connectors can be connected in a direction perpendicular to the longitudinal axis of the busbar system element, characterized in that the busbar comprises a coupling piece (100) for connecting two busbar system elements (1), the coupling piece (100) having a plurality of wedges arranged parallel to each other and extending in a comb-like manner in the longitudinal direction of the coupling piece, the inclined side surfaces (144) of the wedges converging at an angle preferably less than 10°, wherein the coupling piece (100) comprises further HTS strips (160) on the side surfaces (144), which comprise a good side with a ceramic material as HTS and a rear side facing away from the good side, wherein the rear sides of the further HTS strips (160) are fastened to the side surfaces (144) and the further HTS strips (160) extend along the width of the wedge, the coupling piece (100) is adapted to the geometry of the two connectors (41, 51) of the busbar system elements so that when these are arranged one behind the other in their longitudinal axis direction and their connectors (41, 51) face each other at the front ends and the wedges arranged parallel to each other in a comb-like manner are aligned with each other, the coupling piece (100) can be inserted with its wedges combing into the spaces formed by the aligned wedges of the connectors (41, 51), whereby the good sides of the further HTS strips (160) electrically conductively connect the good sides of the HTS strips (61, 62) that are aligned with each other, the good sides of the HTS strips have a solder layer, at least in a contact zone (B) in which the good sides of two overlapping HTS strips are in direct contact, wherein the solder layer is provided for electrically conductive connection to HTS strips of a similar counter-connection and is preferably located over the entire length on which the HTS strips are attached to the side surfaces, and wherein the overlapping good sides of the ends of the HTS strips of the connectors (41, 51) are electrically conductively connected to the good sides of the further HTS strips (160) of the coupling piece (100) by soldering the solder layer.

10. Method for connecting two busbar system elements, each busbar system element (1) comprising a housing (3) extending along the busbar system element; a superconductor strand (2) which runs in the housing (3) along the housing, wherein the superconductor strand (2) has a plurality of HTS strips (61, 62) running side by side, and each HTS strip comprises a good side with a ceramic material as HTS and a rear side facing away from the good side, a connector (41) at the end of the superconductor strand (2) for electrically connecting the superconductor strand to another superconductor strand of another busbar system element with a counter connector (42), wherein the connector (41) of the busbar system elements has a plurality of wedges arranged parallel to each other in a comb-like manner in the longitudinal direction of the connector, the inclined side surfaces (44) of which converge at an angle preferably less than 10°, the rear sides of the end of the HTS strips being attached to the side surfaces (44), and the connector (41) of the busbar system elements is designed in such a way that two of the connectors can be connected in a direction perpendicular to the longitudinal axis of the busbar system element, wherein the good sides of the HTS strips have a solder layer, at least in a contact zone (B) in which the good sides of two overlapping HTS strips are in direct contact, wherein the solder layer is provided for electrically conductive connection to HTS strips of a similar counter-connection and is preferably located over the entire length on which the HTS strips are attached to the side surfaces, and the rear sides of the ends of the HTS strips are attached to the connector (41), comprising the following steps: arranging two busbar system elements one behind the other in their longitudinal axis direction; aligning at least one busbar system element so that the connectors (41, 51) face each other at the front side; aligning at least one busbar system element so that the wedges of the two connectors (41, 51), which are arranged parallel to each other in a comb-like manner, are aligned with each other; providing a coupling piece (100) with a plurality of wedges arranged parallel to each other in a comb-like manner in the longitudinal direction of the coupling piece, whose inclined side surfaces (144) converge at an angle of less than 20°, preferably 10°, the coupling piece (100) having further HTS strips (160) on the side surfaces (144), which comprise a good side with a ceramic material as HTS and a rear side facing away from the good side, the rear sides of the further HTS strips (160) being fastened to the side surfaces (144) and the further HTS strips (160) extending along the width of the wedge, wherein the coupling piece is adapted to the geometry of the two connectors (41, 51) so that the coupling piece (100) can be inserted with its wedges combing into the spaces formed by the aligned wedges of the connectors (41, 51), wherein the good sides of the further HTS strips (160) electrically conductively connect the good sides of the aligned HTLS strips (61, 62) to each other; Inserting the coupling piece (100) initially only at one of its edges, whereby only all ends of the wedges at the edge of the coupling piece are inserted into the spaces between the wedges of one of the connectors (41); Subsequently pivoting in the coupling piece (100) into place, whereby, as the rotation increases, the wedges are pivoted in further and further from the edge into the spaces between the wedges of the two connectors (41, 51); and electrically conductively connecting the overlapping good sides of the ends of the HTS strips of the connectors (41, 51) to the good sides of the further HTS strips (160) of the coupling piece (100) by soldering the solder layer.