In the area of developing innovative methods for theoretical and experimental study of the electromagnetic and thermal behavior of new types of ReBCO-, BSCCO-, and MgB2-based high-temperature superconductor (HTS) tape and windings with innovative configurations for prototype devices for the power grid, research activity is currently being directed mainly in two directions: developing theoretical and experimental analyses regarding possible innovative winding modes for HTS tapes for applications in the power grid; developing numerical models for the behavior of coils made with layered windings (as opposed to pancake coils made) in non-insulated or metal-insulated mode.

In this report, which is part of the main body of RSE’s experience in the design, development, characterization, and testing of HTS windings for superconducting fault current limiters (SFCLs), a number of relevant issues are addressed when designing devices that require superconducting windings. In particular, results are reported on the development of simplified equivalent circuits for the representation of non-insulated helical multilayer windings; on the modeling of first-generation HTS coils both with and without electrical isolation between turns.

The test set-up used for the measurement of AC losses produced in windings is then described; and a theoretical and numerical analysis for the processing the results of AC test on straight HTS samples; tests for the determination of AC losses in straight HTS tapes at various temperatures (65 K – 77 K); and studies for the realization of innovative sample holders for the study of multiple test configurations.

The report suggests continuing the activities by validating the proposed equivalent circuit (and/or possibly developing new interpretative models) by comparison with the experimental results obtained on multilayer helical coils made with the innovative ‘L-shaped’ clamp holder described in this report. In addition, the experimental AC testing campaign on new supplies of HTS tapes will be continued.