The early activity to demonstrate high field superconducting magnets, which achieved field levels greater than 10 T in a relatively short period, was essentially paralleled by a comparable effort toward applying these Type II superconductors to a wide range of electric power applications. The superconducting power applications can be divided into two categories:

high field > 1 T applications — generators, motors, fusion, magnetohydrodynamics (MHD), energy storage

low field < 1 T applications -- transmission cables, transformers, fault current limiters (FCL) The distribution-level FCLs are, for the most part, low field designs, < 1 T, with some of the subtransmission-and transmission-level FCL concepts in the > 1 T range. Some of the low field applications, such as transformers and transmission cables, expose the superconductor to a high level of ac line conditions since they are directly inserted into the ac system; they thus require a conductor design that shows an acceptable ac loss. Some of the FCL designs also expose the superconductor to a high ac field component and therefore need a low-ac-loss conductor. As a result of conductor limitations, work on most “full ac” applications was deferred until the 1980s, when the theory and an ac conductor were more sufficiently developed. The ac transmission cable is an exception as a result of the very low fields of Hop < 0.1 T and the ability to use available Nb3Sn tape conductor, which allows the major field component to be parallel to the plane of the tape. Table 2.1 highlights some of the major electric power components that were constructed and successfully tested during the 1970s and 1980s using liquid helium LTS technology.

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