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Power systems must be developed and extended to supply the continuous enhancement of demands for electrical energy. This development of systems in addition to the integration of distributed generation (DG) units to the power systems results higher capacity of system. Hence, short circuit current of network is confronted with persistent increasing. Since exploration of high temperature superconducting (HTS) materials, superconducting fault current limiters (SFCLs) have attracted a lot of attention all over the world. There are different types of SFCLs. Flux-lock type of SFCL because of its characteristics in fault current limitation is an important category of SFCLs. This paper aims to present a comprehensive review of research activities and applications of Flux-lock type of SFCLs in power systems.

Dynamic responses of high temperature superconducting bulk to inhomogeneous magnetic field distribution of permanent magnet guideway, as well as enlarged amplitude of magnetic field obtained by partially covering the permanent magnet guideway (PMG) with iron sheets in different thickness, are investigated. Experiments show that the instantaneous levitation force increases with the increase of the variation rate of magnetic field (dB/dt). Meanwhile, inhomogeneous magnetic field from PMG causes the decay of levitation force. The decay of levitation force almost increases linearly with the increase of alternating magnetic field amplitude. It should be very important for the application of high-speed maglev system.

The presence of charge order in high-transition-temperature copper oxides (high-Tc cuprates) was identified a decade ago. Now it is a universally observed order like the antiferromagnetic and the superconducting orders of the cuprates. The charge order shows up in various forms depending on materials, and it overlaps other orders in the phase diagram. Because of this diversity and complexity it has been far from clear whether or not the charge order has a direct relevance to superconductivity and to the mysterious pseudogap phenomenon. However, the research development in the last few years has been successful in revealing universal aspects of the charge order and its fluctuations. It turns out that the charge order is compatible with superconductivity, and that its fluctuations have high onset temperature and high energy scale comparable to those of the pseudogap. The charge order correlations might be indispensable for creating the pseudogap and possibly generating high-Tc superconductivity by collaborating with spin and pairing correlations., Comment: 17 pages, 6 figures

Transmitted light measurements in ultraviolet and visible light regions have revealed giant optical anisotropy at 298 K in the high-Tc superconducting cuprates Bi2Sr2CaCu2O8+δ crystals with optimal...

With the development of the second generation (2G) high temperature superconducting (HTS) tape, a several types of high current-carrying conductors have been proposed, among which the quasi-isotropic strand (Q-IS) can effectively improve critical current anisotropy. Twisting technology is essential in practical applications as it can effectively improve current uniformity and stability, reducing AC loss. Aiming at the structural characteristics of the Q-IS, this paper establishes a longitudinal strain model to describe the torsional strain of the tapes in the strand and studies the dependence of critical current characteristics on twisting pitch by theory and experiment. A set of twisting devices were designed, experiments were carried out on the tapes at three different positions in the Q-IS, and their critical currents under different twisting pitches were measured at 77 K. After comparing experiments, the results show that the longitudinal strain model can well describe the characteristics of the critical current of the twisting tapes in a Q-IS.

A 14 T whole-body magnetic resonance imaging (MRI) magnet is designed with Bi2223 high temperature superconducting (HTS) wire. Owing to the large critical current and large critical tensile strength of the wire type HT-NX at ultra-high field, the magnet is optimized in a compact shape with length of 1.9 m and outer diameter of 1.3 m. It is in the form of stacked double pancakes (DPs) with total wire consumption of 455 km. The DPs with various inner and outer radii enable the electromagnetic design to obtain highly homogeneous field of 1.5 ppm over 400 mm diameter of spherical volume (DSV). Hoopstress by winding process, thermal contraction and Lorenz force is calculated and below the wire strength specification. Considerable reduction of screening current effect in MRI magnet application is proved by a calculation example. Field homogeneity as it is influenced by various systematic tolerances and random geometric tolerances is numerically estimated, for further design optimization and design of shimming system. Iron room for passive shielding with dimension of 5 × 5 × 10 m is found to be with wall thickness of around 30 cm to effectively contain the 5-Gauss field to the wall surface. Cooling strategy for cryogen-free technique is proposed and the magnet coils temperature is calculated as below 8 K based on the estimation of joint Ohmic heating power of 1.0 W. Quench protection adopts circuit subdivision and dumping resistors to restrict the maximum voltage below 1.9 kV. No-insulation technique for the quench protection is also discussed. Some other wire candidates like REBCO and Nb3Sn for development of such ultra-high field MRI magnets are commented.

Superconducting (SC) electrical machines could affect different industries due to their high power density. The most promising of them are fully superconducting machines. In the paper whole cycle of development of fully high temperature superconducting electrical machine is described: analytical calculation of magnetic field in the active zone of the machine, finite element modeling, some design features and experimental research of small-scale prototype. It is shown that theoretical and experimental results are in good correlation. Developed approaches could be used to develop high-power machines.

The construction of a new hybrid magnet, consisting of a 11 T superconducting outsert and a 34 T resistive insert magnet, has been finished at the Chinese High Magnetic Field Laboratory (CHMFL) in Hefei. With a room temperature bore of 800 mm in diameter, the hybrid magnet superconducting outsert is composed of four separate Nb 3 Sn-based Cable-in-Conduit Conductor (CICC) coils electrically connected in series and powered by a single power supply system. The power supply system for the superconducting outsert consists of a 16 kA DC power supply, a quench protection system, a pair of 16 kA High Temperature Superconducting (HTS) current leads, and two Low Temperature Superconducting bus-lines. The design and manufacturing of the power supply system have been completed at the CHMFL. This paper describes the design features of the power supply system as well as the current fabrication condition of its main components.

The over-current performance of high-temperature superconductors (HTSs) has been well studied. However, the superconducting devices used in power grid might also suffer lightning current. In previous researches, we have investigated the influences of the substrate layer, encapsulation layer, and tape dimension on the thermal stability of yttrium barium copper oxide (YBCO) tapes after suffering a lightning current. However, in this paper, we will focus on the maximum endurance lightning currents (MELCs) of different HTS tapes including YBCO and BSCCO tapes. We prepared and tested seven HTS samples. The critical current and n value of each sample were measured and calculated before and after the 8/20-μs lightning current tests. A maximum endurable value of lightning current which might not cause the critical current degradation was obtained from the testing results. Finally, the mechanisms causing the degradation were analyzed.

Based on the pre-existing assembled, stacked, or twisted structures of high temperature superconducting (HTS) wires, a novel soldered-stacked-square (3S) HTS wire is suggested and developed through narrowing, stacking, and soldering processes in this study. For the fabrication processes of the 3S wire, a narrow 2G tape with 1 mm width is applied, and the stacking and soldering processes are completed simultaneously. To confirm the performance of the 3S HTS wire, several 3S samples are fabricated. For the 3S HTS samples, we evaluate typical electrical and mechanical properties, and investigated for the feasibility of the 3S HTS wire in the HTS applications. The test results show that measured critical currents of two 3S wire samples are 170 and 255 A, and their curves are typical ones of HTS tapes. The measured self-field ac loss is also reasonable, which is analyzed from both theoretical models of the elliptical and thin strip equations. Moreover, the minimum bending diameter for the 3S samples is approximately 60 mm, and the allowable axial tensile force is 350 N. These mechanical properties of 3S wire are satisfied for the HTS applications significantly. Finally, the smallest round structure of the HTS wire is conceptually suggested for the 3S HTS wire.

High temperature superconducting (HTS) cable operates under relatively low temperature and its unique operating condition brings new challenges in the area of maintenance and diagnostics of the cable. As an example, a temperature difference occurs on connection systems between instruments on room temperature and HTS cables which eventually leads to thermal energy loss. The thermal energy loss affects frequency characteristics of the cable which are critical aspects for simulation and maintenance of the HTS cable systems. In this paper, an attempt to reduce thermal loss is introduced with an improved connector applying a Peltier module. The performance of the designed connector is verified with analysis of electromagnetic wave propagation properties of HTS tapes and a cable. The investigation of S -parameters and the proposed connection method is expected to be further applied to various HTS systems in future.

In the 200 m high temperature superconducting (HTS) cable test facility at Chubu University constructed in 2010, a three-layer structure of the tapes in the cable is employed for obtaining the high current capacity up to 2 kA. Previous study shows that the critical current is affected by the layout of the tapes such as gaps and the current feeding mode. In the stacked tape conductors, the critical current of BSCCO tapes shows strong dependence on the current feeding directions between the tapes. The critical current is improved when the opposite-direction current is applied to them and degraded for the same-direction current feeding mode because of strong magnetic field interaction between them from the transport current in each tape. This paper presents the measurements of the critical currents of a BSCCO tape in the stacked conductors with the ferromagnetic materials. By using the ferromagnetic materials surrounding the tapes, self-field of HTS tapes is affected and their critical currents are improved by more than 10%. Ferromagnetic shunt effects on the critical current of HTS tape are reported through the magnetic field analysis.

The Ni- substituted Y1−xNixBa2Cu3O7−δ high temperature superconducting samples with 0 ≤ x

The effect of Co2+, 3+ and Ca2+ substitution in Y3+ site in YBa2Cu3O7−δ superconductor has been studied. The series of high temperature superconducting samples of Y1−y−xCoyCaxBa2Cu3O7−δ with 0 ≤ x ≤ 0.015 and y = 0.020 were prepared by solid-state reaction method. The samples were characterized for phase purity and lattice parameter variations by X-ray diffraction. The AC susceptibility curves, χ'(T), show that in reserving cobalt fixed sample with the optimum Tc, by substitution of divalent Ca2+ at the trivalent Y3+ site no sensitive increasing happen in the superconducting transition temperature.

Characterizing high-temperature superconducting (HTS) filters is considered in this paper. An accurate, fast, and economic cryogenic platform is in-house developed. The novel platform involves only foam box and liquid nitrogen. The characterization of a HTS bandpass filter (BPF) takes only minutes rather than hours compared with the outsourced characterization in refrigerator. Measurement results are in good agreement with the properties benchmarked in refrigerator.

The high temperature superconducting (HTS) exciting double stator direct-drive wind generator (HTS-DSDDG) is a promising approach for offshore wind generation, due to the fact that double-stator structure is employed to simultaneously realize stationary seal of the cooling system and brushless of current transfer. In this paper, two kinds of placement strategies of HTS coils are proposed, denoted as single-polarity excitation and double-polarity excitation, respectively. Furthermore, the relationship between the consumption of HTS wires and the volume of the single-/double-polarity HTS-DSDDGs is quantitatively investigated to determine the excitation operating points of HTS coils. Since the different placement strategies of HTS coils will lead to differences of the excitation operating points, as well as differences of generator size and HTS wires consumption, the single-/double-polarity HTS-DSDDGs are compared in terms of the electromagnetic performance, the weight and the material cost. Finally, the conclusion is drawn that the 10 MW double-polarity HTS-DSDDG is lighter and lower cost than the single-polarity one.

Smart Ship Systems Design (S3D) is a software environment for the definition and assessment of energy distribution systems. A detailed study of high-temperature superconducting (HTS) technologies in a shipboard environment has driven the development of new capabilities and models in the S3D tool. As a result of conducting the HTS study, we introduced into S3D a new capability for quick analysis of thermal systems independently of the electrical systems with which they interact, we improved the method for importing and exporting the bill of materials to facilitate rapid setting of system alignments, we demonstrated a new tool to merge LEAPS databases, and we began testing methods to expand the design space. The study also provided insight for further S3D improvements such as the need for a supervisory controller that optimizes the system operating point to ensure fair analysis of concepts, for a method to prevent cross-connecting of components that are represented in multiple disciplines, and for an API to permit the use of design space exploration methods such as TIES.

The need for ship system level models for assessing the benefits of high temperature superconducting (HTS) technology is articulated. The development of ship designs with HTS power cables using Smart Ship Systems Design (S3D) showed the need for new components such as the cable terminations that serve multiple HTS cables at the nodes. Conceptual designs of such multi-cable terminations are discussed. Results of the investigations of several alternative thermal insulation systems for HTS cables are discussed in the context of reducing the mass, size, and complexity as well as increasing the resiliency of the shipboard integrated power system. Design considerations for gaseous helium HTS power devices are discussed.

Since the discovery of high-temperature superconductivity, over 30 years ago, there has been great interest in utilising these materials to develop next-generation electric power applications that would replace conventional transformers, cables and motors and generators. There also exist novel technologies enabled by superconductivity, such as superconducting fault current limiters (SFCLs) and superconducting magnetic energy storage (SMES). The high current carrying capacity of high-temperature superconducting (HTS) coated-conductor wires, with zero (DC), or low (AC) losses, enables more efficient devices with smaller footprints and reduced weight. Continual advances in manufacturing techniques have resulted in the commercial availability of long lengths (km+) of high-quality wire from several manufacturers worldwide. This has improved the technological readiness level and commercial attractiveness of such devices.

Recently, using the superconducting cuprates as the conducting layers, high temperature superconducting (HTS) cable with high capacity and low loss has been widely researched for the construction of urban distribution network. In this work, a 35 kV/1 kA HTS cable system in the length of 100 m has been established and put into operation since February 15 in 2017. During the process of cable manufacture, the witness samples in the length of 5 m were fabricated to verify the cable design. The results showed that the addition of comber board to the cable winding machine would be beneficial for the uniform distribution of superconducting tapes, and successively, the improvement of current capability of superconducting cable. The critical current (IC) of the superconducting layer was measured to be more than 1 kA, which conforms to the requirements of rated current of the HTS cable system.

WOS:000476530300001; International audience; Thanks to their very high current carrying capabilities even under high magnetic field conditions and their outstanding mechanical properties, high temperature superconductors (HTSs) such as REBCO (rare-earth BaCuO) tapes are very attractive for high magnetic field applications. Depending on the magnet design goals and constraints, it can be advantageous in some cases to reduce the electrical margins of the conductor. Considering the uncertainty in locally evaluating the critical current, and the inhomogeneities of present-day REBCO tapes, there is a significant risk of the critical current being overstepped locally, thus triggering local damaging hotspots. Such an event does not have the sudden occurrence and/or fast spreading quality usually associated with the concept of 'quench' and should be simply seen as thermal runaway induced by dissipative zones (DZs). The development of numerical models to evaluate the occurrence and propagation of such zones inside windings is critical in the development of a HTS magnet fully using REBCO tape performance while guaranteeing safe operation conditions. In this work, we have developed a transient electro-thermal model adapted to pancake-based coils. It accounts for both the nonlinear electrical and thermal behavior of the material and considers the local inhomogeneities of the critical current I c along the tape. The electrical part is one-dimensional (1D) and computes the nonlinear dissipation in the conductor depending on the local operation conditions while the thermal part is two-dimensional (2D) to account for the heat propagation along the conductor length and from turn to turn. In order to improve computation efficiency, adaptive time-stepping methods have been introduced with the objective of ensuring good accuracy of simulation results.

In the last 10-15 years, the most common strategy in the development of High Temperature Superconducting (HTS) cable for magnets has been to imitate Low Temperature Superconducting (LTS) cable designs. However, requirements for LTS materials are not valid for HTS materials, which are extremely stable. For example, non-twisted multifilamentary Bi-2223 tapes have been successfully used in several magnets. This paper review stability and analyse inductance and AC losses in non-twisted stack of HTS tapes. Numerical calculations show that twisting has negligible effect on inductance variations in a stack of tapes. Regarding AC losses, any magnet built with coated conductors have larger losses than LTS ones, because of the aspect ratio and large width of the tape. If a wide tape is replaced by a non-twisted stack of narrow tapes, losses and residual magnetisation could be reduced. In contrast with multifilamentary wires, twisting a stack of tapes reduces losses only marginally. Therefore, cables composed of non-twisted stack could be designed to have losses comparable to the one of twisted stack concepts. Few examples of large cables for fusion applications are discussed. Designs based on non-twisted stacks can be simpler, more robust and cost effective than twisted ones., Comment: 20 pages, 10 figures, submitted to Cryogenics

Large AC current supply is essential for measuring the current transport characteristics of superconducting wires, such as AC loss in helical coil conductors. Commercial current supplies are generally too large and heavy, and therefore, they are inconvenient to use with the superconducting wires. The authors have been studying a small and lightweight large current supply with a high temperature superconducting (HTS) current transformer. An air-core HTS current transformer is suitable for the miniaturization of AC supply because this transformer does not have an iron core and thus does not have large volume and heavy weight. In this paper, we report that the current supply with the air-core HTS current transformer can output large current with high frequency by using the resonance phenomenon. Furthermore, we provide a method for the detection of normal transitions in the transformer by measuring the current transformation ratio of its primary and secondary currents. This detection method is composed of a simple measurement system, and experimental results show the usefulness of this detection method for the air-core transformer.

Fabricated by top-seeded melt-texture methods, high-temperature superconducting (HTS) bulk, such as YBaCuO bulk exhibits anisotropic properties of the critical current density J c spatial distribution in growth sector regions and growth sector boundaries (GSBs). It was found that the YBaCuO bulk arrangement optimization considering the J c spatial distribution above a permanent magnet guideway (PMG) enhances the levitation performance of the HTS magnetic levitation (maglev) system according to the past experiments. Therefore, from the point of view of practical applications, a theoretical model describing this HTS growth anisotropy is required to reproduce its effect on HTS maglev properties. In this study, we proposed an updated J c spatial function with an adjustment parameter to better describe HTS bulk’s growth anisotropy. Its Cartesian form is suitable for differently shaped bulk superconductors. We subsequently established a 3D simulation model of an HTS–PMG maglev system and completed the calculations of both the levitation force and decay of two different bulk arrangements above the PMG. The calculation results are consistent with the experimental results, which verifies the reliability of the 3D HTS–PMG maglev model and J c spatial function. Further, all results show that a more stable HTS levitation with a larger levitation force is generated in the case where the GSB is aligned with the longitudinal direction of the PMG’s largest magnetic field. This provides a reference for HTS maglev designs. Furthermore, the modeling can be a useful tool for optimizing the HTS–PMG maglev system for several scenarios.

The paper provides the results of the experimental and computational study of the processes occurring in high temperature superconducting transformer windings while secondary winding is short-circuited. The obtained mathematical simulation matches closely with the experimental results. The temperature variation curves for superconducting windings were analysed, and conclusions were made on the necessity of changes in HTS transformer design, namely the necessity of windings heat-insulation from each other and adding a high-resistance coating material for HTS wire in HTS transformer primary winding.

The Toroidal Field (TF) current leads which supply 68 kA DC current for the TF coils are the largest capacity High Temperature Superconducting (HTS) current leads among the three types of HTS current leads for ITER. Two TF HTS current leads prototypes have been successfully built and cold tested at the Institute of Plasma Physics of the Chinese Academy of Sciences (ASIPP). The cold performance test is a crucial step to verify the design parameters and manufacturing process before starting the series production. The cold performance test includes rated current steady state operation and Loss Of Flow Accident (LOFA) test, different Heat eXchanger (HX) boundary operation, over-current, joint resistance, and heat conduction tests. This paper will present the major results of those tests.

In this paper, the magnetostriction and stress of an orthotropic mechanical high-temperature superconducting disk with a concentric small hole are investigated based on the exponential model of the critical state. Approximate solutions of the displacement and stress for the superconducting disk during zero-field cooling (ZFC) and field-cooling (FC) processes are obtained. The results show that tensile stresses will appear in the disk during the decreasing field of ZFC, while the stresses are always compressive during the increasing field of ZFC and FC processes. This indicates that the superconducting disk is easily damaged during the decreasing field of ZFC and FC processes. The critical point where tensile stress is largest is provided. The value of magnetostriction depends on the size of the disk, the applied field and the magnetization process. This research is helpful in the reliability design of high-temperature superconducting disks and cables with high strength for space solar power stations.