3-D Finite Element Simulations of Strip Lines in a YBCO/Au Fault Current Limiter

Abstract

Abstract-Geometrical aspects of the design of fault current limiters (FCL) have a great impact on their performances. Recently, the University of Geneva have made certain optimizations by splitting the FCL into many small dissipative lengths in order to achieve a distributed transition along the device.For this paper, we have performed new 3D finite element method (FEM) simulations for studying the behavior of strip lines of a YBCO/Au FCL in an AC nominal use (sinusoidal current at industrial frequency) up to 3 Ic. The very large aspect ratio of the device needs a particular attention to the modeling and meshing process.The numerical results show that presence of sharp corners can influence the performance of the device. Due to the high value of the electric field in these areas, the local losses are much higher than in the case of smooth corners, and this may lead to burning and cracking the wafer. Irreversible damage experiments have confirmed these locations.In this paper we proposed new geometries, taking into account the length of the connecting path and the corners optimization in order to decrease the risk of very high localized losses in the meander.

500 V/200 A fault current limiter modules made of large-area MOD-YBa2Cu3O7thin films with high-resistivity Au–Ag alloy shunt layers

“…Another possible explanation is that in the neighboring segment to the segment in which the first quench occurred, the superconducting current flow, mainly a detour current coming from the external resistor, becomes nonlinear due to inhomogeneous connection resistances through Cu leads, solder and Ag electrodes (figure 10). An electric field reportedly becomes high at the superconducting current flow along sharp corners, which induces local losses much higher than those along smooth corners [15]. Friesen and Gurevich showed theoretically that nonlinear current flows in superconductors caused by restricted geometries cause significant peaks of voltage and dissipation due to the highly nonlinear E-J characteristics, E = E c (J/J c ) n , n 1 [16].…”

“…Figures 18 and 19 show examples of successful switching, where the prospective fault currents of 4.27 kA rms and 4.29 kA rms were limited to 990 A rms and 973 A rms , respectively, which were much higher than those for module no. 1 (figures [15][16][17] due to the smaller external resistor (0.2 ) compared to the resistor (0.35 ) used in module no. 1 .…”

Finite-Element Method Modeling of Superconductors: From 2-D to 3-D

“…The goal is to use the new 3-D simulations for proposing geometries that prevent such negative effects. The results will be presented in [14].…”

Finite-element analysis and comparison of the AC loss performance of BSCCO and YBCO conductors

“…Aspect ratios exceeding 1,000 require a very fine mesh with a huge number of elements, which would result in an enormous consumption of CPU time and memory. A possible FEM approach is to 'approximate' the thin strip by increasing its thickness and thus decreasing artificially the aspect ratio of the conductor by a factor of 10 to 1000 [5], [6]. Another possibility is to treat the problem as one-dimensional and in this way to avoid creating a 2D region and FEM mesh in the y-direction for the YBCO strip [7], and we have employed a similar approach.…”