Shielding Characteristics of Solenoidal Superconducting Screens Made From HTS Tape, for SFCL Applications

In the design and prototyping of an Inductive-Resistive Superconductor Fault Current Limiter (IR-SFCL), previously presented by the authors, superconducting screens made from BSCO bulk have been used for shielding the inductive stage of the device. This kind of screens has several problems as rigidity, brittleness, commercial dependence on size and high cost. In order to avoid such issues, replacing the bulk-type superconducting screens by screens made from high temperature superconducting (HTS) tape is proposed. Tapes are more flexible and allow to easily make screens with several sizes and configurations, and better behavior against temperature changes and dynamic effects. To select a suitable configuration for this type of screen, a preliminary study of the shielding capacity of screens with different configurations, made from tape, is presented. This study, as well as literature, led us to select the solenoidal configuration as the most suitable for our application. In this work, we study solenoidal screens built with independent concentric layers, each one made from non-insulated tape, and all in contact just by the Ag external cover of the tape. A test method has been developed, and screens with 1 to 10 solenoid layers have been tested to find out their shielding factor. The shielding mechanism (diamagnetism vs. induced currents) has been studied by measuring of the transport current generated in between the non-insulated solenoids. The low incidence of these currents in the magnetic shielding process of the superconducting tape screens is reported.