Research on damage characteristics and microscopic appearance of ReBCO tapes after DC overcurrent

With the expansion of the power grid, the use of DC transmission technology is becoming increasingly prevalent. This has led to higher transmission voltage levels, which in turn have brought to the fore the issue of large short-circuit currents. The existing circuit limiter's performance is insufficient to meet the growing demand. Superconducting fault current limiter, which based on ReBCO tapes, is considered to be the solution to the problem of large short-circuit current. However, the failure mode of ReBCO tapes under DC overcurrent remains to be studied. In the superconducting state, the current flows mainly through the superconducting layer. Therefore, it is necessary to investigate the overcurrent characteristics of the superconducting layer after overcurrent. In this work, the damage characteristics and microscopic appearance of ReBCO tapes after overcurrent were investigated. The magnetic field distribution characteristics and the microscopic appearance of the superconducting layers of ReBCO tapes with different degrees of critical current recession were investigated, and the chemical elements of the superconducting layers were analyzed. The results show that large-area pits were found on superconducting layer after overcurrent, the element types and mass proportions did not change. Overcurrent affects the superconductivity of the tape mainly by changing the physical structure of the superconducting layer.