Essential Material Knowledge and Recent Model Developments for REBCO-Coated Conductors in Electric Power Systems

Abstract

The manufacturing of commercial REBCO tapes, REBCO referring to Rare-earth barium copper oxide, has matured enough to lead to a variety of applications ranging from scientific instruments to electric power systems. In particular, its large current density with a high n index and low hysteresis losses make it a strong candidate for specific applications relying on the dependence of its resistance on current. Despite its advantages, there are still issues that remain to be addressed, such as the scarcity of experimental data for the basic characteristics of the superconductor over a wide range of temperature and applied magnetic field, the homogeneity of these characteristics along the conductor length, as well as the anisotropy of the critical current and n index with respect to the direction of the applied magnetic field. To better utilize the technology, it is therefore sensible to understand the relevancy of these issues so that one could simulate as accurately as possible the physics of the superconductor, at least the dynamics that may impact the correct operation of the superconducting device. There are different levels of modelling to achieve such a goal that can either focus on the performance of the superconductor itself, or on the whole device. The present work addresses some of the latest developments in the modelling of commercial REBCO tapes in power systems with a particular focus on the thermoelectric behavior of superconducting devices connected to external circuits. Two very different approaches corresponding to two different scales in the modelling of superconducting devices are presented: (1) analysis using equivalent models and lumped parameters to study the thermoelectric response of superconducting devices as a whole, (2) Finite Element Analysis (FEA) to compute distributed fields such as current density, magnetic flux density and local losses in tapes. In this context, this paper reviews both approaches and gives a broad variety of examples to show their practical applications in electric power systems. Firstly, they show the relevance of the technology in power systems engineering. Secondly, they allow inferring the necessary level of model details to optimize the operation of superconducting power devices in power grids. This level of details relies completely on the knowledge of some basic measurable properties of superconducting tapes (critical current and n index) and their cooling conditions.

Effective circuit modelling and experimental realization of an ultra-compact self-rectifier flux pump

“…We also note that the degree to which these effects are significant will depend on the details of the experimental set up. Future experiments and extensions to the current effective circuit model will look to quantitatively incorporate such physics, as has recently been done in other areas of superconductor power electronics [33], and assess the degree to which they improve agreement with experiment.…”

Strategies for conformal REBCO windings

“…However, there is a countervening effect as discussed by Trillaud et al [9]. As the current in each tape approaches its limit, the internal dynamics within its REBCO layer shifts from flux creep to flux flow before reaching the normal state (as demonstrated in Figure 1 from [9]).…”

“…However, there is a countervening effect as discussed by Trillaud et al [9]. As the current in each tape approaches its limit, the internal dynamics within its REBCO layer shifts from flux creep to flux flow before reaching the normal state (as demonstrated in Figure 1 from [9]). The local electric field in the tape increases exponentially with current: where 𝐸 0 = 10 −6 𝑉 𝑚 is the quench criterion, 𝐼 𝑐 (|𝐵|, 𝜃, 𝑇) is the critical current for the conditions (B,) for that tape, and 𝑛~30 is the index that characterizes the power-law dependence of the superconductornormal transition for REBCO.…”

Plastic Deformation Simulation of REBCO Tapes Using Particle Methods

“…The PEEC method enables to simulate an accurate screening current with short computation time. A REBCO tape is modeled with a number of inductances L and REBCO resistances are considered with the power index model [16] considering the J c -B- characteristics.…”