Analysis of thermo-physical properties of materials suitable for thermal stabilization of superconducting tapes for high-voltage superconducting fault current limiters

Abstract

High-temperature superconducting coated conductors (CC) are attractive materials for high-voltage resistive fault current limiters. Commercially produced CC tapes cannot withstand electric fields over 100 V m−1, and therefore, they have to be modified by addition of thermal stabilization layer. We investigated several composite systems suitable for such thermal stabilization. As a matrix of composites, Stycast resins were used, which contain various contents of powder particles from SiC, SiO2, PbTiO3, ZrW2O8, or synthetic diamond. The thermo-physical properties such as thermal expansion, heat capacity, thermal diffusivity and direct-current electrical conductivity were measured because they are influenced by filler content in the composite. The possible highest amount of the powder can slightly increase the thermal conductivity and decrease the thermal expansion of the system to an acceptable value needed for the coating of CCs. A side effect is simultaneous drop of heat capacity; however, its value stays still high enough for the purpose of heat sinking. Overall, the best results were achieved in system with 20 vol% of SiC filler in Stycast 2850FT + Catalyst 23LV resin matrix. There the contribution of the semiconducting SiC addition to the electrical conductivity of composite was negligible.