The design, fabrication and testing of a cooling system using solid nitrogen for a resistive high-T_csuperconducting fault current limiter

Abstract

In general, conventional high-T c superconducting fault current limiters (SFCLs) are operated by cooling systems with a liquid cryogen, such as liquid nitrogen (LN2). However, in the fault mode, LN2 evaporates because of joule heating in the SFCL module, so the SFCL system experiences an enormous increase in nitrogen gas volume. In this case, the thermal stability and protection of the system become the primary concerns for the design of the SFCL cooling system. In order to enhance the thermal stability and safety of the system, an SFCL cooled by solid nitrogen (SN2) as a large heat capacitor has been proposed as an alternative. In this paper 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 also conducted on the reference design codes and thermal requirements for the optimal design of the SN2 cooling system. The results demonstrate that the improved thermal contact obtained between the SN2 cooling system and the SFCL module renders the proposed system a suitable cryogen for the SFCL module. Detailed experimental results for the LN2 and SN2 cooling systems are presented and discussed.

Thermal and Electrical Stabilities of Solid Nitrogen (SN2) Cooled YBCO Coated Conductors for HTS Magnet Applications

“…The sample did not recover completely even after the test was complete. These results suggest that, at , thermal contact between the SN2 and YBCO CC tape worsens gradually and they become separated at the inter-surface (i.e., dry-out phenomenon), which causes the YBCO CC tape to recover more slowly and finally run away [8]. In the case of , the YBCO CC tape recovered completely during the repetitive quench/recovery tests because relative small was not enough to cause the SN2 to dry-out, or delayed the time for drying-out to occur.…”

“…8(b)], the values (92.5 ) were also similar until after the 5th quench/recovery test, and the recovery times were 3.5 s. After the 6th test, the value (101.7 ) and recovery time (4.8 s) increased slightly until the 8th quench/recovery test, after which it increased abruptly to 136. 8 . The sample did not recover completely even after the test was complete.…”

“…At , the peak joule heating flux measured in the SN2 ( traces 1) and conduction cooling system ( traces 2) were 60.7 and 60. 8 , respectively. Although these two values were similar, the sample in the SN2 cooling system recovered fully within 1 s, whereas the trace curve of the conduction cooling system increased gradually with time, which indicates that sample had not recovered even after the test was finished.…”

Thermal and Electrical Stabilities of YBCO Coated Conductor Tapes in a Solid Argon-Liquid Nitrogen Mixed Cooling System

“…However, cooling systems that employ SCs alone show a thermal contact problem (thermal "dry-out") between the SC and the object being cooled upon repeated thermal or electrical disturbances [4,9]. To improve thermal contact, mixed-phase cryogens have been proposed using the solid-liquid phase transition temperature of a single component [13]. Although this can improve thermal contact between the SC and the cooled object, it is a difficult method to apply to HTS power devices because the two phases cannot be simultaneously maintained unless temperature is fixed at transition temperature and the solid/liquid ratio is controlled.…”

Solid cryogen: a cooling system for future MgB2 MRI magnet

“…Soon afterwards, Song et al . investigated the SN 2 cooling system for a high temperature superconducting (HTS) fault current limiter 28 . Bascuñán et al .…”