The design, fabrication and testing of a cooling system using solid nitrogen for a resistivehigh-Tc superconducting fault current limiter

Abstract

In general, conventional high-Tc superconducting fault current limiters (SFCLs) are operated by cooling systems with aliquid cryogen, such as liquid nitrogen (LN2). However, in the fault mode, LN2 evaporatesbecause of joule heating in the SFCL module, so the SFCL system experiences an enormousincrease in nitrogen gas volume. In this case, the thermal stability and protection of thesystem become the primary concerns for the design of the SFCL cooling system. In order toenhance the thermal stability and safety of the system, an SFCL cooled by solidnitrogen (SN2) as a large heat capacitor has been proposed as an alternative. In thispaper we report the quench/recovery characteristics of a YBCO-coated conductor(CC) evaluated in an SN2 cooling system for the SFCL. A feasibility study is alsoconducted on the reference design codes and thermal requirements for the optimaldesign of the SN2 cooling system. The results demonstrate that the improvedthermal contact obtained between the SN2 cooling system and the SFCL modulerenders the proposed system a suitable cryogen for the SFCL module. Detailedexperimental results for the LN2 and SN2 cooling systems are presented anddiscussed.