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(a) Comparison between the power-law and the overcritical resistivity models in term of resistance per unit length. The normal state resistance of REBCO is considered in the model. (b) Comparison between the global resistance per unit length of the tape, using the power-law and the overcritical current model, in parallel with the resistance of silver at 90 K.
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A detailed knowledge of the resistivity of high-temperature superconductors in the overcritical current regime is important to achieve reliable numerical simulations of applications such as superconducting fault current limiters. We have previously shown that the combination of fast pulsed current measurements and finite element analysis allows acc...
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... looking at the tape as a whole, this difference is mitigated by the presence of a stabilizer such as silver. In Figure 8b, the resistance per unit length of silver is represented as a constant line at 3.4 · 10 −3 Ω cm −1 . The silver acts as a parallel resistor and the effective resistance per unit length of the tape is lower than that of a single REBCO layer. ...
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Citations
... Nowadays, high-temperature superconducting (HTS) tapes are increasingly finding applications in the fields of the energy industry, energyefficient systems for transmission, storage, distribution and distribution of energy [2][3][4]. The realization of pronounced thermally-induced dynamic states (TDS) leading to the transition of the superconductor to the normal state allows the application of HTS tapes in such devices as current limiters [5] and HTS switches (keys) [6]. The actuation rate of such HTS switches is generally limited by the rate of heat propagation and the normal zone. ...
This paper presents the results of experimental studies of switching processes of high-temperature superconducting tapes under the action of a pulse current load of microsecond duration. The reversible, stable and irreversible switching of the superconductor to the normal state has been realized. To demonstrate the opportunity of controlled generation of transients in superconducting composites, the characteristics of a superconducting switch capable of cyclic switching between flux flow and ohmic modes with preservation of switching parameters were investigated. The characteristics of a superconducting switch have been calculated based on experimental results.
... Thus, the resistivity of the YBCO layer in the full temperature range can be expressed as Eq. (6) [19]: ...
For high-temperature superconducting (HTS) cables carrying substantial currents, the current carrying capacity of a single YBCO tape is limited, and multiple tapes need to be connected in parallel. The current sharing design of parallel YBCO tapes has emerged as a central concern in the HTS cable design. However, various tape parameters, including critical current \(I_\textrm{c}\), n-value, and joint resistance, can significantly influence the current distribution in the system. In this paper, the influence of YBCO tape parameters on the current distribution characteristics of the cable was studied. The results showed that the current distribution and quench characteristics were regulated by tape \(I_\textrm{c}\), tape n-value, and tape joint resistance together, and that meanwhile, the total current also served as an important factor. Significant influence of the joint resistance was also observed in the event of a limited total current, which was no longer obvious for a total current close to the total \(I_\textrm{c}\). For the parallel tapes with the same \(I_\textrm{c}\), the one with higher resistance quenched later, while in the case of the same resistance, the effect of the tape \(I_\textrm{c}\) is greater than that of the tape n-value.
... High-temperature superconducting (HTS) power cables using 2G coated conductors are particularly attractive to replace traditional metal conductors for power transmission and distribution applications that require power cables of higher power density, smaller size and lighter weight. Additionally, the very fast and responsive nature of the transition from superconducting to normal state when an HTS cable carries a current higher [5,6,7,8,9,10,11]. Advanced Conductors Technologies in collaboration with the Center for Advanced Power Systems (CAPS) developed and tested FCL performance on two CORC ® cables, one has 8 layers of two 2G REBCO tapes wound on a copper core and the other has 6 layers of three REBCO tapes wound on a stainless steel core. ...
p>Simulation for the fault current limiting operation of REBCO CORC® superconducting cables with different core materials</p
... High-temperature superconducting (HTS) power cables using 2G coated conductors are particularly attractive to replace traditional metal conductors for power transmission and distribution applications that require power cables of higher power density, smaller size and lighter weight. Additionally, the very fast and responsive nature of the transition from superconducting to normal state when an HTS cable carries a current higher [5,6,7,8,9,10,11]. Advanced Conductors Technologies in collaboration with the Center for Advanced Power Systems (CAPS) developed and tested FCL performance on two CORC ® cables, one has 8 layers of two 2G REBCO tapes wound on a copper core and the other has 6 layers of three REBCO tapes wound on a stainless steel core. ...
With high power density and low loss, CORC® superconducting cables composed of RE-Ba2Cu2O7-δ (REBCO) coated conductors are of great interest for power transmission applications. They can also effectively be designed to serve as fault current limiters, thanks to their sharp superconducting-to-normal transition. Coupled electromagnetic-thermal finite element (FE) simulations implemented in COMSOL Multiphysics® were developed and validated against the published results for the fault current limiting performance of two CORC® cables of REBCO coated conductors wound on either copper or stainless steel cores. For improved accuracy, temperature dependencies of electrical and thermal properties of all component materials were considered in the simulations. The simulations were performed in the cross-sections of the cables for every individual layer of each REBCO tape to deliver comprehensive understanding of evolution of the current distribution and temperature rise in those layers. The studies can suggest approaches to optimize cable design for fault current limiting (FCL) applications by assessing the role of individual components. In the paper, possible computational errors, challenges and improvements are also discussed.
... The three inductors are magnetically coupled and are non-linear due to the ferromagnetic core. An uniform current density J cu is calculated by equation (12) and obtained as the ratio between the total current I AC of the AC circuit (see figure 5). Where, V app represents the applied voltage that comes from the electrical circuit (here modeled as a lumped electrical parameter), V indcu is the total induced voltage in the copper coil, η is the total cross-section area of the copper coil, N cu is the number of turns of the copper coil, R cu is the total resistance of the copper coil, and z is the unit vector in the z-direction. ...
Superconducting devices have been widely studied over these years. Their application can be found in cables for electric power transmission, energy storage systems, magnetic levitation, electric machines, and fault current limiters. The literature presents some formulations to model the superconductors' behavior using the finite element method (FEM), such as the H, the AV, and the T formulations, among others. Many superconducting devices have been simulated and designed using some of these formulations. However, none method available offers a coupling between an electric power system, simulated using electrical lumped parameters, to the superconducting FEM model. In this context, this work introduces a methodology for coupling superconducting devices in FEM to lumped parameters composing the power system. Here, a case study with a Saturated Iron Core Superconducting Fault Current Limiter was presented to apply the proposed methodology. This research analyzes the influence of the self and external fields in the superconducting coil on its critical current density. Moreover, it investigates the DC-biased coil voltage drop and the superconducting resistance. Besides, the paper presents the simulations of short circuits for various DC currents applied to the superconducting coil. Short-circuit tests were performed for validating the simulation results, and it showed a maximum error of 15% for the compared points.
... The first step of the method requires to have a good initial guess of the involved quantities (namely h Ag,tot and ρ Ag (T )). This is done by combining the characteristics provided by the manufacturers on their data sheets with direct measurements of R vs. T (carried out with an experimental setup similar to that described in [9]). In Fig. 3(left), we report the measured resistance vs. temperature for the same SuperPower sample as Fig. 2. It is possible to describe the electrical resistance of the tape as follows: ...
A good knowledge of material properties is a critical aspect for modeling high-temperature superconductor (HTS) devices. However, the knowledge of the electrical resistivity of coated conductors above the critical current is limited. The major challenge in characterizing this regime lies in the fact that for I>Ic, heating effects and thermal instabilities can quickly destroy the conductor if nothing is done to protect it. In previous work we extracted overcritical current data, obtained by combining fast pulsed current measurements with finite element analysis (Uniform Current (UC) model). In this work, we assessed the impact of the uncertainties of the input parameters on the quantities calculated with the UC model (temperature, current in each layer of the tape and resistivity of HTS). Firstly, sensitivity and uncertainty analyses were performed and it was found that the input parameters that mostly affect the UC model are the electrical resistivity and the thickness of the silver layer. Afterwards, an optimization method was developed to correctly estimate the geometry and the resistivity of the silver layer. This method combines experimental measurements of resistance R(T) of the tape and pulsed current measurements. The development of this strategy allowed us to determine the parameters that significantly impact the results of the UC model and helped to minimize their uncertainties. This enables a more accurate estimation of the resistivity in the overcritical current regime.
Self-regulating high temperature superconducting (HTS) flux pumps offer a promising solution for compensating the magnetic field degradation in closed HTS coils without direct electrical contacts. These flux pumps utilize superconducting bridges, which function as switches based on their nonlinear resistance. This study focuses on evaluating and analyzing the charging performance of a bifilar bridge coil wound with various insulated coated conductors. The
V-I
curves of these tapes are measured across a wide range, highlighting the occurrence of current sharing beyond the critical current. Furthermore, a full-scale finite element (FEM) model is developed to investigate the current variation within multilayer tapes during the charging process and elucidate the underlying noninductive principle. The findings reveal remarkable disparities in the charging characteristics of REBCO conductors with different widths and thicknesses as bridge materials, which will significantly impact the charging function of flux pumps. This research provides valuable insights for optimizing the design of self-regulating flux pump.
The design of superconducting applications containing windings of superconducting wires or tapes requires electro-thermal quench modelling. In this article, we present a reliable numerical method based on a variational principle and we benchmark it to a conventional finite difference method that we implemented in C++. As benchmark problem, we consider a racetrack coil made of REBCO superconducting tape under short circuit, approximated as a DC voltage that appears at the initial time. Results show that both models agree with each other and analytical limits. Since both models take screening currents into account, they are promising for the design of magnets (especially fast-ramp magnets) and power applications, such as the stator windings of superconducting motors or generators.
With high power density and low loss, CORC® superconducting cables composed of RE-
$\rm{Ba_{2}Cu_{3}O_{7-\delta}}$
(REBCO) coated conductors are of great interest for power transmission applications. They can also effectively be designed to serve as fault current limiters, thanks to their sharp superconducting-to-normal transition. Coupled electromagnetic-thermal finite element (FE) simulations implemented in COMSOL Multiphysics® were developed and validated against the published results for the fault current limiting performance of two CORC® cables of REBCO coasted conductors wound on either copper or stainless steel cores. For improved accuracy, temperature dependencies of electrical and thermal properties of all component materials were considered in the simulations. The simulations were performed in the cross-sections of the cables for every individual layer of each REBCO tape to deliver comprehensive understanding of evolution of the current distribution and temperature rise in those layers. The studies can suggest approaches to optimize cable design for fault current limiting (FCL) applications by assessing the role of individual components. In the paper, possible computational errors, challenges and improvements are also discussed.
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 paper, the critical current degradation and life distribution characteristics of 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
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V·m
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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.
