In the context of developing innovative approaches for the theoretical and experimental analysis of the electromagnetic and thermal behavior of new types of High-Temperature Superconductor (HTS) tapes based on ReBCO, BSCCO, and MgB2, as well as innovative winding configurations for prototypes of devices intended for the electrical grid, the current research activity is primarily focused on two key directions. The first involves the development of theoretical and experimental analyses concerning potential innovative winding methods for HTS tapes intended for applications in the electrical grid.

The second focuses on creating numerical models for the behavior of coils made in layer-wound or pancake-wound configurations, being Not-Insulated or with innovative electrical insulations. This report, aligning with RSE’s extensive experiences in designing, developing, characterizing, and testing HTS winding for Superconducting Fault Current Limiters (SFCL), addresses specific challenges related to the design phase of devices requiring the implementation of superconducting windings.

In particular, the mathematical treatment for developing a numerical model based on a lumped parameter equivalent circuit is presented to estimate the behavior of AC losses and currents between turns and within the same tape during transient regimes of power supply to helical windings made with HTS tapes. The model is validated against other numerical and analytical models for the simplified case of a straight tape. Subsequently, the results of an experimental campaign are presented, involving the power supply of two layer-wound coils made with 2G HTS tapes, one with electrical insulation between turns and one without.

These coils are wound on an innovative support that allows variation in the connection between layers; different supply combinations are systematically tested by varying the AC current at 50 Hz in liquid nitrogen, drawing qualitative conclusions on the respective trends of AC losses. Finally, a numerical-experimental study is presented regarding the impact of the surface characteristics of the tapes, as well as the operating temperature, on the transverse resistance in No-Insulation pancake coils made with HTS tapes. The simplified model, easily applicable to other windings, is tested on a coil supplied with current ramps at temperatures ranging from 10 K to 80 K.

The intention is to continue the activities by validating the proposed numerical models (for layer-wound and pancake coils) with others found in the literature or described in previous reports, along with the results of new and existing experiments.

The Report is available on the Italian site