Overcritical Current Resistivity of YBCO-Coated Conductors Through Combination of PCM and Finite-Element Analysis

Supercond. Sci. Technol.

Lacroix

et al. 2020

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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 accounting for heating effects occurring during the current pulses. We demonstrated that it is possible to retrieve the correct current and temperature dependence of the resistivity data points of the superconductor material. In this contribution, we apply this method to characterize the resistivity vs. current and temperature of commercial REBCO tapes in the overcritical current regime, between 77 K and 90 K and in self-field conditions. The self-consistency of the overcritical resistivity model ρ OC (I, T) is verified by comparing DC fault measurements with the results of numerical simulations using this model as input. We then analyze by numerical simulation to what extent using the ρ OC (I, T) model instead of the widely used power-law model ρ PWL (I, T) affects the thermal and electrical performance of the tapes in the practical case of a superconducting fault current limiter. A remarkable difference is observed between the measured overcritical current resistivity model ρ OC (I, T) and the power-law resistivity model ρ PWL (I, T). In particular, the simulations using the power-law model show that the device quenches faster than with the overcritical resistivity model. This information can be used to optimize the architecture of the stabilizer in superconducting fault current limiters.

Section: Resistivity Curves In the Overcritical Current Regimementioning

confidence: 99%

Section: Regularized Overcritical Current Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Resistivity of REBCO tapes in overcritical current regime: impact on superconducting fault current limiter modeling

Riva

Supercond. Sci. Technol.

Lacroix

et al. 2020

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“…Moreover, due to the current sharing between the layers, it is difficult to know the amount of current carried by the superconducting layer and its resistivity. In our previous works [4], [5], we combined pulsed current measurements This project has received funding from the Swiss Federal Office of Energy SFOE under grant agreement SI/500193-02. N. Riva, A.Akbar and B. Dutoit are with Ecole Polytechnique Fédérale de Lausanne, Switzerland (e-mail:nicolo.riva@epfl.ch, bertrand.dutoit@epfl.ch) F. Sirois and C. Lacroix are with Polytechnique Montréal, Canada (f.sirois@polymtl.ca, c.lacroix@polymtl.ca) F. Grilli is with Karlsruhe Institute of Technology (francesco.grilli@kit.edu) (PCM) with a 2-D thermal model (which we named Uniform Current (UC) model), in order to estimate the temperature over time for each layer of the REBCO tape, as well as the amount of current flowing in each layer.…”

Section: Introductionmentioning

confidence: 99%

Optimization Method for Extracting Stabilizer Geometry and Properties of REBCO Tapes

Riva

Grilli

IEEE Trans. Appl. Supercond.

et al. 2021

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A good knowledge of material properties is a critical aspect for modeling high-temperature superconductor (HTS) devices. However, 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 our previous works we proposed the overcritical current model, 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 and current in each layer of the tape). 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 to correctly estimate the geometry and the resistivity of the silver layer was developed. This method combined experimental measurements of resistance R(T) of the tape and pulsed current measurement. The development of this strategy allowed us to determine the parameters that significantly impact the UC model and helps to minimize their uncertainties. This can enable a precise estimation of the overcritical current resistivity. 10 %

Post-processing method for extracting the resistivity of Rare-Earth Barium Copper Oxide (REBCO) coated conductors in over-critical current conditions from ultra-fast V-I pulsed current measurements

Richard

Journal of Applied Physics

Lacroix

2019

This paper presents a simple but rigorous method to extract correctly the resistivity of the superconducting Rare-Earth Barium Copper Oxide (REBCO) layer of High Temperature Superconductor coated conductors, when the latter are characterized in over-critical current conditions using ultrafast V-I pulsed current measurements. The pulsed current measurement method is used to reduce the amount of heat generated by the strong current flowing in the sample, but it cannot prevent it completely at current levels well above the critical current. In order to estimate accurately the temperature rise, we developed the so-called “Uniform Current” (UC) model, which consists in a static current sharing model coupled with a 2D thermal solver. The model assumes that the electric field is uniform over the sample cross section. It has been shown that this hypothesis works fine at high currents, but for lower current levels, although still higher than the critical current, one must wait until the magnetic relaxation effects disappear before using the outputs of the UC model. We also derived a theoretical bound for the error related to magnetic relaxation, which can be estimated experimentally by using a rectangular pick-up coil located just above the sample surface. After applying the UC model on an experimental set of data, one obtains a whole set of data points defining the resistivity ρ(J,T) of the REBCO superconductor being characterized.