二代高温超导带材失超特性研究OACSTPCD

The quench of high temperature superconducting(HTS)tapes will reduce their flow capacity and thus affect the operation stability of high temperature superconducting devices.At present,most simulation models of superconducting tapes are two-dimensional models,which cannot accurately simulate the electromagnetic-thermal behavior in the process of quench.A finite element method with multiple physical field coupling is used to study the quench characteristics of the second-generation high temperature superconducting tapes.In the three-dimensional coordinate system,the magnetic field intensity vector is taken as the solution variable to establish the second-generation HTS tape quench evolution electromagnetic-thermal simulation model.The electromagnetic-thermal characteristics and evolution under different thermal disturbance conditions of the second-generation HTS tapes along the length direction as well as the width direction are studied.The shunt state of each layer and the resistivity change behavior of the superconducting layer in the process of superconducting tapes overcurrent are analyzed,different types of overcurrent and overcurrent behaviors are distinguished,and the resistivity criterion of overcurrent quench is proposed. For the superconducting tapes studied in this paper,the minimum quench energy is 4.62 J and the propagation velocity is 0.96 cm/s when Iop = 0.6Ic.When the local heat energy is 1.82Qmq,the temperature of tape stays above critical temperature for a short time after the thermal disturbance ends,and the tape stays quenching.When the local heat energy is 3.9Qmq,during the thermal disturbance the maximum current density region of the superconducting layer diffusing to other regions,the hot region changes from superconducting state to resistive state,and propagates symmetrically along the tapes.After 2 s,the quench region expands to twice the quenching region than the initial stage of the thermal disturbance. According to the overcurrent degree,duration and the shunt condition of high temperature superconducting tapes,and corresponding resistivity change of the superconducting layer,the criterion of overcurrent quench resistivity is put forward as follows.When the overcurrent causes the resistivity of the superconducting layer to be lower than that of the silver layer and the copper layer,the overcurrent causes the recoverable quench of the tapes.When the overcurrent causes heat accumulates in the superconducting layer,the resistivity of the superconducting layer continues to be higher than that of the silver layer and the copper layer,and when the critical resistivity reaches a certain transition time,the overcurrent impact leads to unrecoverable quench. Compared with the two-dimensional model,the three-dimensional model solves the problem that the two-dimensional model cannot simulate the electromagnetic-thermal behavior of the superconducting tapesin width direction during the quench process.It can accurately simulate the electromagnetic-thermal characteristics and evolution process of the second-generation superconducting tapes in length and width direction under different thermal disturbances.