YBCO超导带材二次冲击恢复过程的模拟及实验研究

Simulation and experimental research on the secondary quench and recovery process of YBCO superconducting tape

YBCO超导带材失超后的快速恢复对于电阻型超导故障限流器(RSFCL)重合闸应对二次故障电流冲击至关重要。当前研究通常将电阻恢复视为带材恢复,在实际的盘式结构中存在复杂的微孔结构,一次冲击恢复至超导态时仍存在大量气泡滞留,影响带材的二次冲击恢复过程。针对典型的微孔结构建立了三维模型,采用CFD模拟并结合大电流冲击实验,对比分析了一次冲击恢复过程和二次冲击恢复过程中各项参数的变化。实验结果表明二次冲击过程中的峰值温度为162.9 K,比一次冲击高14.6 K,带材恢复至超导态需要1.88 s,比一次冲击延长0.63 s。模拟结果表明初始状态存在气泡滞留,二次冲击过程中带材温度上升更快,气泡量更多,温度横向分布更不均匀,最大温差达20.5 K。由此可见,超导态的恢复不能作为重合闸的标准,气泡场未完全恢复会降低限流器的安全阈值,危害系统安全,所以也应将气泡完全消散的时间作为实际运行中重合闸的参考时间。

The rapid recovery of YBCO superconducting tape after quenching is very important for the resistance type superconducting fault current limiter(RSFCL)reclosing to deal with the secondary fault current impact.Current research usually regards resistance recovery as tape recovery.However,there is a complex microporous structure in the actual disk structure and there are still a large number of bubbles remaining when the tape returns to the superconducting state after the first impact,which affects the secondary quench and recovery process of the tape.In this paper,a three-dimensional model of the typical microporous structure was established and CFD simulation was combined with large-current impact experiments for comparing and analyzing the changes of various parameters during the quench and recovery process of the first and secondary impact.The experimental results show that the peak temperature during the secondary impact is 162.9 K,which is 14.6 K higher than that during the first impact.It takes 1.88 s for the tape to return to the superconducting state,which is 0.63 s longer than that of the first impact.The simulation results show that there is bubble retention in the initial state.During the secondary impact,due to the presence of bubbles the temperature of the tape rises faster and the amount of bubbles is more.The lateral temperature distribution is more uneven and the maximum temperature difference is 20.5 K.It can be seen that the recovery of the superconducting state cannot be used as the standard for system reclosing.The incomplete recovery of the bubble field will reduce the safety threshold of the superconducting fault current limiter and endanger the safety of the system.Therefore,the time when the bubble is completely dissipated should also be used as the reference time for system reclosing in actual operation.