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Superconducting coils may suffer from electromagnetic vibration due to changing electromagnetic fields under AC conditions. In the long term, this vibration may cause performance degradation of superconducting tapes. In order to study the influence of electromagnetic vibration between superconducting tapes on their performance, the study can be started from the simplest form of electromagnetic vibration, that is, the electromagnetic vibration between two superconducting tapes. The degree of electromagnetic vibration under different AC currents were analyzed by simulation, and the variation of critical current ( I c) and the n-value of Y-Ba-Cu-O (YBCO) tapes after undergoing long-term electromagnetic vibration through experiments were measured. The results show that two YBCO tapes does not show obvious performance degradation under tens of hours the electromagnetic vibration caused by the AC current amplitude of 1.2 to 1.4 times Ic .

The performance degradation of High Temperature Superconducting (HTS) tape, which may be influenced by various heat exchange conditions due to different cooling methods, is of significant for HTS devices under repeated overcurrent. In this article, considering different heat exchange conditions, a series of repeated overcurrent experiments were carried on YBCO tapes under 50Hz sinusoidal alternating current. The degradation of critical current of YBCO tapes after repeated overcurrent was recorded. the resistance characteristics of YBCO tapes under different cooling conditions were analyzed. Through finite element simulation, the temperature and current distribution of YBCO tape under different heat exchange conditions were simulated. The experimental results show that the overcurrent capability of the conductor under conduction cooling is far inferior to the liquid nitrogen immersion method.

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 c 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 c degradation. The experimental results provide meaningful references for the performance degradation of the YBCO tapes and related devices.

The performance degradation of superconducting equipment under repeat fault is a key issue for the operation of superconducting equipment in grid operation. The mechanism of the High Temperature Superconducting (HTS) tape performance degradation behavior is an important issue that need to be figured out. Therefore, it's necessary to carry out the performance degradation study of HTS tape under repeat overcurrent. In this paper, considering overcurrent duration, a series of repeated overcurrent experiments were carried on YBCO tapes under 50 Hz sinusoidal alternating current. The degradation of critical current of YBCO tapes after repeat overcurrent was recorded. The critical current density of the YBCO tape was scanned to track sample's structural change during experiment. The mechanism of the degradation development of YBCO tapes after their first degradation was described. The research could provide a reference for the design of fault protection and life assessment of HTS devices.

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.