Study on Dynamic Current Distribution Characteristics of Non-uniform Superconducting Types in Parallel Connection

In superconducting fault current limiter (SFCL), due to the special process characteristics and possible defects of YBCO tapes, the performance of superconducting tape and welding resistance of parallel branch will be non-uniform in parallel connection. In this way, non-uniform quench loss and non-uniform current distribution in parallel types will occur, which will cause a degeneration in current carrying capacity and performance of SFCL. In this paper, the change process of dynamic current distribution in parallel type under impulse current is simulated, and the self-balance effect of current in the process is analyzed. Besides, the current distribution characteristics and the current carrying capacity of YBCO tapes' parallel connection with inhomogeneity of type and welding resistance are studied. In order to study the influence of non-uniform tape on current distribution, a mathematical model for parallel connection of YBCO tapes in SFCL is established, and the correctness of the model is verified by experiments. The study shows non-uniform welding resistance will reduce the current carrying capacity of parallel structure, and the relationship between degradation of current carrying capacity and inhomogeneity of welding resistance is obtained. Besides, a minimum requirement for uniformity of type performance in different branch is put forward. Through the above research, the influence of inhomogeneity of type and welding resistance was studied, which is of great significance to the design of SFCL. And it provides a selection of inhomogeneity margin for superconducting type of parallel structure.