I am having trouble discovering why temperature fluctuations and magnetic field fluctuations are not a stability concern for superconducting magnetic levitation trains. I am under the impression that liquid helium is expensive and leaks out of containment fairly easily, suggesting higher probability of quenching. The weather naturally induces temperature fluctuations, suggesting possible temperature quenching. The magnetic field fluctuations in the motion of the train could max out the critical field limit, inducing a quench. Why are none of these quenching situations regarded as statistical concerns in maglev trains?
I know that Wikipedia is not the best source for reference, but according to this page the superconducting parts that are cooled by liquid nitrogen in most cases. Most of the superconductors are High TC ones, which still needs to be cooled.
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I still can't put this in a comment, so if the admins could move this into a comment that's fine.