Design and manufacturing of the large scale high-Tc superconducting DC magnet for the 2.3 MVA SFCL

To develop a High-T_c superconducting (HTS) magnet that is applicable to the high voltage electric device applications, it is necessary to consider several important factors such as large critical current, reliable electric insulation system, stable cryogenic status, expected economic benefits, and so on. This paper deals with the skills to design and manufacture the high voltage HTS DC magnet accepting large pulse input current. The multi-stacked HTS solenoid winding was suggested for the HTS magnet having large critical current. To protect the HTS winding, when quenched, the copper layer was suggested as a buffer sharing the large pulse current. The thin grooves on the GFRP bobbins not only guide the HTS winding but also play the role of electrical insulation for the high voltage application. With regard to the thermal stability of the magnet, sub-cooled liquid nitrogen cooling system was used for the cooling system of the HTS DC magnet. To reduce the resistance of the normal conducting parts in the HTS magnet, several HTS tapes were additionally attached on these parts. Based on this study, the HTS DC magnet for the 2.3 MVA class high-T_c superconducting fault current limiter (HTSFCL) was successfully manufactured and tested. The HTS DC magnet developed by this study endured 2.53 MJ (18.66 MW_max) without any evidence of quench.