Yttrium Barium Copper Oxide Tape Research Articles

Research on Data-Driven Approaches for Life Prediction of YBCO Tapes Under Overcurrent

Superconducting power devices have many advantages. In recent years, prototypes of various superconducting power devices based on high-temperature superconducting wires have been successfully developed, and some prototypes have also been tested on the power grid, which has accelerated the development of superconducting power technology. However, the reliability of superconducting devices under overcurrent has not yet been supported by research, which is part of the important reason that restricts large-scale promotion of them. In this article, the critical current degradation and life distribution characteristics of yttrium barium copper oxide (YBCO) tapes under overcurrent were analyzed. The overcurrent test adopted a sinusoidal alternating current with an amplitude of 480 A (4–5 times the critical current) and a frequency of 50 Hz. The duration of each overcurrent was 0.44 s. The critical current of the sample was measured in liquid nitrogen using the 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> V·m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> criterion. The results show that there is an approximately exponential relationship between the critical current degradation rate of YBCO tapes and the number of overcurrent cycles. The life of YBCO tapes under overcurrent can be considered to obey the two-parameter Weibull distribution. Two different remaining useful life of YBCO tape prediction models based on data-driven methods were built. It is verified through cross-checking that the relative prediction errors of the two methods are 8.4% and 5.3%, respectively. And the validity of the models was verified through uncertainty analysis and the comparison with two traditional statistical methods.

A Resistance Model of Fault Current Limiting Coils Under DC Impact

The short-circuit fault current on the dc side affects the operation safety of the multiterminal flexible HVdc (MTDC) transmission system seriously. The resistance-type superconducting fault current limiter (RSFCL) has received extensive attention in limiting the dc impact current because it has a fast response speed and zero impedance at a steady state. At present, there are so many works on the simulations of RSFCLs but the error is relatively larger, which affects the design accuracy of RSFCLs. In this article, the characteristics of dc fault current limiters are studied. The resistance and other parameters of yttrium barium copper oxide (YBCO) samples under the dc impact are measured. The equivalent heat capacity and the equivalent heat dissipation of YBCO tapes are defined and calculated to analyze the heat transfer process of YBCO tapes under the dc impact. A modeling method based on the equivalent heat parameters is obtained. In addition, the thermal balance point during the dc impact is defined by that thermal power production and heat loss of the YBCO tape are equal to identify the credible boundary of the resistance curve. Finally, the correctness of the proposed method is verified by the experimental results of fault current limiter coils and compared with the R-Q fit model. This research aids in the simulation analysis and optimization design of dc RSFCLs.

Experimental Study on the Performance Change of YBCO Tapes Under Repeated Overcurrent

Superconducting cables or fault current limiters may encounter short-circuit currents during operation. When experiencing multiple overcurrent cycles, the critical current degradation of yttrium barium copper oxide (YBCO) tapes may occur. The performance degradation of YBCO tapes under overcurrent is a gradual process. It may take dozens or hundreds of overcurrent or overheating pulses. To get a better understanding of this process, we explored the performance change of YBCO tapes under repeated overcurrent. A life characteristics test platform was established. The electromagnetic performance degradation of YBCO tape under 50 Hz sinusoidal ac operating conditions was investigated, taking the effect of the overcurrent amplitude and duration into account. Meanwhile, the relationship between the number of overcurrent cycles and the I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> degradation is proposed. The reason for this performance change is analyzed by comparing the 2-D current density distribution of the YBCO film before and after experiencing overcurrent. In addition, the U-I property and resistance variations of these tapes are presented. It is inferred that the cracking of the superconducting layer is the main cause of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> degradation. The experimental results provide meaningful references for the performance degradation of the YBCO tapes and related devices.

Critical Current Degradation of YBCO Tape With Different Stabilizing Layers Under Cyclic Mechanical Strains

Yttrium Barium Copper Oxide (YBCO) tape has a superconducting layer with a thickness of 1 μm. In the actual operation of YBCO superconducting devices, they may be subjected to mechanical strains produced by electromagnetic and thermal forces. In some cases, these forces may repeat tens of thousands times during their lifetime. We designed and built a cyclic strain test apparatus for HTS tapes, and tested the critical current degradation characteristics of YBCO tapes with two different stabilizing layers. Most of the test samples show extremely small critical current degradation even after 60000 cyclic mechanical strains. But the tapes with stainless steel layer are more likely to suffer from thermal stability problems. Increased current density was observed in the lateral direction when magnetizing the degraded samples.

Design of a 1 MJ/100 kW high temperature superconducting magnet for energy storage

With significant progress in the manufacturing of second-generation (2G) high temperature superconducting (HTS) tape, applications such as superconducting magnetic energy storage (SMES) have become promising for implementation in the electricity grid. Compared to Li-ion batteries, SMES can provide higher power levels at a lower capital cost (down to $200/kW), they have a longer lifetime (over 20 years) and a comparable cycle efficiency of over 95%. Nevertheless, SMES technology is still underdeveloped, which is reflected in the lack of large-scale 2G HTS SMES units. One of the main challenges is designing an optimal magnet that can persistently store energy while withstanding the forces arising from the magnetic field and maintaining a temperature below the critical transition value. This paper outlines a methodology of designing a 2G HTS SMES, using Yttrium-Barium-Copper-Oxide (YBCO) tapes operating at 22 K. The target storage capacity is set at 1 MJ, with a maximum output power of 100 kW. The magnet consists of a stack of double pancake coils designed for maximum storage capacity, using the minimum tape length. The properties of a commercial YBCO tape published in the literature are used to derive the equations for scaling the critical current with magnetic field intensity and direction, as well as operating temperature. The inductance of the resulting coil configuration is calculated analytically, and is used for estimating the total storage capacity of the magnet. Finally, the properties of the superconducting magnet are summarised in a table.

Newly Developed Modeling Application for Quench Characteristic Analysis of YBCO Pancake Coil

We demonstrate a newly developed three-dimensional (3-D) heat conduction analysis model for a yttrium barium copper oxide (YBCO) pancake coil by including the turn-to-turn and layer-to-layer heat conduction in the one-dimensional heat transport equation. The YBCO tape is represented by two thermal components, which are in thermal contact through a thermal resistance. The turn-to-turn and layer-to-layer thermal contacts are defined with thermal conduction coefficients of the insulation. For validating the accuracy of the simulation model, a quench propagation analysis of a racetrack pancake coil is performed, and the simulation results are compared with the experimental results presented in a published paper. The comparison shows that the simulation model can give a reliable forecast of the quench propagation characteristics. When considering the reduction of the thermal conduction efficiency induced due to temperature variation near the hotspot, the simulation results are in high consistency with the experimental results. A 3-D surface map of the temperature profile is displayed to show the impact of the thermal conductivity coefficient of the insulation. The simulation model is proven to be a powerful tool to study the quench propagation characteristics of the YBCO coil.

Performance comparison of 1X versus 4X HTS tapes toward the design a 10‐MW direct drive HTS generator for wind turbine applications

AbstractWith current developments underway at the University of Houston, 4× high‐temperature superconducting (HTS) yttrium barium copper oxide (YBCO) tapes are expected to reach a fourfold critical current density improvement at 30 K and 3 T as part of an Advanced Research Projects Agency‐Energy (ARPA‐E)‐sponsored project. The impetus for this project is to develop and deploy cost‐effective direct drive HTS generators for large offshore wind turbine generators. The improved conductor performance of 4× tapes over 1× tapes is projected to allow for a significant reduction in the amount of HTS tapes required to generate the excitation field and, thus, lead to a reduction of the overall generator cost. It was, however, deduced from simulation results that conventional methods of rotor field enhancement using rotor iron makes 1× conductor competitive enough compared with 4× conductors; hence, commercially available YBCO tapes can provide all the energy density requirements to make wind turbines a competitive energy resource based on energy forecasts. This paper is a presentation of design and optimization work to find the best generator topology from the point of view of both machine design and electricity supply. The generators are numerically modeled and simulated using 1× and 4× YBCO HTS conductors on either or of both the rotor and stator side of the generators.

Start-ups tackle fusion

Martin Greenwald stands in a windowless control room at Massachusetts Institute of Technology, holding a heavy, thick cable in his left hand. Pinched between his right index finger and thumb is a thin strip of dull-brown metal tape. That strip can carry as much electrical current as the hefty cable, he explains, and could enable scientists to build a mighty machine they’ve been dreaming about for decades. By winding spool after spool of the yttrium barium copper oxide tape into some of the strongest magnets on Earth, scientists at the MIT Plasma Science & Fusion Center hope to build a nuclear fusion reactor. If all goes well, these ultrastrong magnets will lasso and wrangle a roughly 100 million oC hydrogen plasma, driving its protons to fuse and releasing tremendous amounts of energy over sustainable time periods. Commonwealth Fusion Systems, a spin-off company from this MIT project, hopes to turn the

Numerical and Experimental Evaluations of the Quench Detection Performance of an YBCO/Nb–Ti d Tape

Quench detection for the high-temperature superconducting tape, especially rare-earth barium copper oxide (REBCO) tape, is difficult due to the small normal zone propagation velocity in it. To address this issue, we have proposed a novel quench detectable REBCO tape with a low-temperature superconducting wire used as a quench detector, “REBCO/LTSd tape.” In this paper, we numerically and experimentally demonstrated the validity of the tape consisting of the yttrium barium copper oxide (YBCO) tape and the Nb–Ti wire used at 4.2 K under no external field. Results of the numerical simulation showed that sufficiently high voltage of 0.1 V can be detected before the maximum temperature of the YBCO tape reaches 50 K with the Nb–Ti wires having high resistance at normal conducting state. Experimental results also demonstrated that the quench in the YBCO was detected with the 1 V scale voltage by using the pure Nb–Ti wire.

Bending–Peeling Method to Measure Interface Strength of YBCO Tape

Modern yttrium barium copper oxide (YBCO) superconductor tape can carry a high critical current under a rather high magnetic field with good strain tolerance. However, the interface between the laminas is quite weak, and the interfacial strength has thus attracted considerable research interests. We designed a new method to analyze the interfacial strength of YBCO tape. A piece of tape was first embedded in a rectangular-section beam of epoxy resin, with the tape plane parallel to the middle cross section of the beam and the tape edge at the beam surface. The epoxy beam height was greater than the tape width. Three-point bending was applied to the beam, with one point on the opposite side of the tape across the beam and the other two points at the two ends. The interface was thus tensed during loading. In this way, the interfacial strength could be directly determined, and the interfacial energy could be calculated from the force–displacement curve. The crack interface was examined using scanning electron microscopy and analyzed using energy-dispersive X-ray spectroscopy. The average interface strength was 5.16 MPa. The experimental data were used to further simulate the crack behavior during the cooling process.

Maximum Endurance Lightning Current of Different High-Temperature Superconducting Wires

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.

Simulation of YBCO Tape and Coils in HTS Maglev System

In the process of running high temperature superconducting maglev train, the AC(Alternating Current) loss of superconducting coil is directly related to its safe operation and operating cost. In this paper, the simulation model was built based on the finite element software COMSOL Multiphysics, and mainly simulated and calculated the AC losses of YBCO(Yttrium Barium Copper Oxide) tape and coils. In this model, as the solving object, the singular and infinite long YBCO tape and coils model was solved with H-formulation and the nonlinear characteristic (E-J constitutive law) and anisotrophy (B-J characteristic) were taken into consideration as the theoretical foundation. Then on the basis of the model under maglev suspension system, AC losses under different amplitude and frequence AC currents were calculated. The results shows that under different frequencies and dynamic components, the local maximum AC loss of YBCO tape and coils occurs when the steady-state DC(Direct Current) current is 30A. Then comparing with old maglev suspension system, the new system can greatly reduce the energy consumption and the material cost.

Study of the Influence of Helical Bending Strain and Perpendicular Self-Field on Critical Current Degradation for Multilayer YBCO Tapes

An experimental investigation of the critical current (I c ) degradation of multilayer twisted yttrium barium copper oxide (YBCO) tapes in self-field was performed. The influence of the number of tape layers (N) and twist pitch (P) on critical current was researched. The results showed that the influence of helical bending strain and perpendicular self-field on critical current degradation was a comprehensive process. No critical current degradation was found when there was just one layer and the twist pitch was over 20 mm. However, the situation would change when the number of tape layers increased. The critical current degradation would increase with increase in helical bending strain or perpendicular self-field. The critical current degradation can reach a maximum of 24.6% when the helical bending strain was 0.23% and the number of tape layers was 5. A mathematic formula was set up to express the comprehensive influence of helical bending strain and perpendicular self-field on critical current degradation. The results can provide an important theoretical foundation for the application of high temperature superconducting tapes and the design of YBCO cables.

Semifluorinated Alkylphosphonic Acids Form High-Quality Self-Assembled Monolayers on Ag-Coated Yttrium Barium Copper Oxide Tapes and Enable Filamentization of the Tapes by Microcontact Printing.

A custom-designed semifluorinated phosphonic acid, (9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,16-heptadecafluorohexadecyl)phosphonic acid (F8H8PA), and a normal hexadecylphosphonic acid (H16PA) were synthesized and used to generate self-assembled monolayers (SAMs) on commercially available yttrium barium copper oxide (YBCO) tapes. In this study, we wished to evaluate the effectiveness of these monolayer films as coatings for selectively etching YBCO. Initial films formed by solution deposition and manual stamping using a non-patterned polydimethylsiloxane stamp allowed for a comparison of the film-formation characteristics. The resulting monolayers were characterized by X-ray photoelectron spectroscopy (XPS), contact angle goniometry, and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). To prepare line-patterned (filamentized) YBCO tapes, standard microcontact printing (μ-CP) procedures were used. The stamped patterns on the YBCO tapes were characterized by scanning electron microscopy (SEM) before and after etching to confirm the effectiveness of the patterning process on the YBCO surface and energy-dispersive X-ray spectroscopy (EDX) to obtain the atomic composition of the exposed interface.

The Study of Critical Current for YBCO Tape in Distorted Bending Mode

A mathematical model of equivalent bending radius was used to analyze the effect of bending strain on the critical current of yttrium barium copper oxide (YBCO) tapes in distorted bending mode. The relationship between critical current and twist pitch under different bending radii was measured. For enough larger twist pitch, even though the bending radius was smaller than the critical bending radius, the equivalent bending radius was always greater than the critical bending radius. Only when the bending radius was less than the critical bending radius and the twist pitch was reduced to a certain extent, the equivalent bending radius was smaller than the critical bending radius. As a consequence, the critical current dropped sharply and cannot be restored. The model and analytical equation was feasible and can be used for the design of solenoid YBCO magnet.

Design and development of high-temperature superconducting magnet system with joint-winding for the helical fusion reactor

An innovative winding method is developed by connecting high-temperature superconducting (HTS) conductors to enable efficient construction of a magnet system for the helical fusion reactor FFHR-d1. A large-current capacity HTS conductor, referred to as STARS, is being developed by the incorporation of several innovative ideas, such as the simple stacking of state-of-the-art yttrium barium copper oxide tapes embedded in a copper jacket, surrounded by electrical insulation inside a conductor, and an outer stainless-steel jacket cooled by helium gas. A prototype conductor sample was fabricated and reached a current of 100 kA at a bias magnetic field of 5.3 T with the temperature at 20 K. At 4.2 K, the maximum current reached was 120 kA, and a current of 100 kA was successfully sustained for 1 h. A low-resistance bridge-type mechanical lap joint was developed and a joint resistance of 2 nΩ was experimentally confirmed for the conductor sample.

Heat conduction and thermal stabilization in YBCO tape

Yttrium barium copper oxide (YBCO) coated conductors are widely used in the conduction-cooled superconducting magnets with rapid development in refrigeration technologies at present. ‘Quench’ is a state that refers to the irreversible and uncontrolled superconductor to resistive transitions in the superconductor. The propagation of ‘quench’ or ‘normal zone’ has different characteristics in these high temperature superconductors (HTS) compared to low temperature superconductors. The superconductor to normal index, known as ‘n’ is much flatter in HTS. The hot spot emerging in local region due to quench and non-uniform critical current may cause permanent damage to whole HTS tape and hence the magnet winding pack. Thus it is necessary to determine the temperature profile along the length of HTS tape under a given energy (joule heating) such that propagation of the hot spot developed locally can be prevented early. In this study, a one dimensional, time dependent heat diffusion equation with appropriate boundary conditions are used to describe the consequences of the normal zone propagation resulting in the temperature diffusion in a HTS tape. The results demonstrate the necessity of adequate cooling of the edges of the flat HTS tapes to prevent irreversible normal zone transitions.

Thermal diffusion and quench propagation in YBCO pancake coils wound with ZnO andMylar insulations

The thermal diffusion properties of several different kinds of YBCO (yttriumbarium copper oxide) insulations and the quench properties of pancakecoils made using these insulations were studied. Insulations investigatedinclude Nomex, Kapton, and Mylar, as well as insulations based on ZnO,Zn2GeO4, and ZnO–Cu. Nomex, Kapton, and Mylar, chosen for their availability and ease of use,were obtained as thin ribbons, while the ZnO based insulations were chosen for their highthermal conductivity and were applied by a thin film technique. Initially, short stacks ofYBCO conductors with interlayer insulation, epoxy, and a central heater strip were madeand later measured as regards their thermal conductivity in liquid nitrogen. Subsequently,three different pancake coils were made. The first two were smaller, each using one metertotal of YBCO tape present as four turns around a G-10 former. One of thesesmaller coils used Mylar insulation co-wound with the YBCO tape, the other usedYBCO tape onto which ZnO based insulation had been deposited. One largercoil was made which used 12 total meters of ZnO insulated tape and had 45turns. Temperature gradients were measured and thermal conductivities wereestimated from these coils; the results obtained were compared to those for theshort stacks. Quench propagation velocity measurements were performed on thecoils (77 K, self-field) by applying a DC current and then using a heater pulse toinitiate a quench. Radial NZP (normal zone propagation velocity) values (0.02–1 mm s − 1) were two orders of magnitude lower than axial values (∼10–20 mm s − 1). Nevertheless, the quenches were generally seen to propagate radially within the coils, in thesense that any given turn in the coil is driven normal by the turn underneath it. This was dueto the fact that while the radial NZP is much lower than the NZP along the conductor (∼100 ×) the distance by which the normal zone must expand longitudinally is much larger than thedistance by which it must expand radially to reach the same point; in our case this ratio is ∼ 1600.

A new finite-element method simulation model for computing AC loss in roll assistedbiaxially textured substrate YBCO tapes

This paper presents a new finite-element simulation model for computing theelectromagnetic properties and AC losses in systems of YBCO (yttrium barium copperoxide) conductors on roll assisted biaxially textured substrates (RABiTS). In this model,the magnetic field dependent permeability and ferromagnetic loss of the substrates inRABiTS YBCO tapes are taken into account. The simulations were employed to simulatethe AC loss in stacks of two parallel connected YBCO tapes. The simulation results arecompared with the experimental data to check the validity of the simulation model. Theresult reveals an effective way of significantly reducing AC loss in YBCO tapes by stackingtwo RABiTS YBCO coated conductors with the appropriate relative tape orientation.

AC loss study of antiparallel connected YBCO coated conductors

Some applications of high temperature superconducting conductors require a non-inductivewinding, which may be constructed from antiparallel connected YBCO (yttrium bariumcopper oxide) tapes. In the case of AC applications, this antiparallel winding changes theAC losses from that of an isolated conductor. This study focuses on the effect of the spatialseparation and misalignment between conductors on their AC loss behavior for YBCOconductors on both rolling assisted biaxially textured substrate (RABiTS) and ion beamassisted deposition templates in an effort to fully understand the behavior of theseconductors in real world applications. For RABiTS samples, the study was carried out forall three possible configurations (the so-called back-to-back, front-to-front and same-wayconfigurations) to clarify the effect of the ferromagnetic substrate on the ACloss behavior in these conductor configurations. Numerical simulations were alsoemployed in some cases to compare with and elucidate experimental observations.