The Impact of critical current inhomogeneity in HTS coated conductors on the quench process for SFCL application

Growing electricity demand from a range of sources with higher loads and the industry structural changes open the possibility of more frequent and larger fault currents producible in liver power grids. Traditional solutions to the fault have difficulties in satisfying the requirement of the new power grid requirement due to many factors, such as high cost and additional impact to power grid in normal loading condition, which leads to the research for an efficient alternative solution of interest to both academia and industry: Superconducting fault current limiter (SFCL). Critical current I_c is used to describe the maximum current that a superconductor can transport and is one of the most important parameters to be considered while designing a SFCL. Guaranteeing the homogeneous distribution of the critical current density flowing in a superconductor is not possible due to manufacturing process limitations. In this paper, the impact of critical current inhomogeneity of coated high temperature superconductors (HTSs) during the quench process is studied experimentally. The results show that both the amount of I_c degradation and the size of I_c degraded segments have a great impact on the maximum temperature generated in the quench process of HTSs when the prospective fault current is low ( 1.13I_c to 1.51I_c. Higher amount of localized I_c degradation allows higher maximum temperatures under low voltage fault. Additionally, smaller I_c degraded segment allows higher maximum temperatures.