Flux pinning and AC loss in second generation high temperature superconductor wires

This book provides an overview of the current status of research and development, and fundamental understanding towards improving flux pinning and reducing AC loss in second-generation (2G) high temperature superconductor (HTS) wires. Superconductors have no electrical resistance; therefore can carry current with no electrical energy loss in a dc environment. HTS wires are so efficient that they can carry more than 200 times the power of conventional copper wires of the same size at liquid nitrogen temperatures. The potential uses for HTS wires in electric power applications include underground transmission cables, oil-free transformers, superconducting magnetic-energy storage (SMES) units, fault current limiters, high-efficiency motors, and compact generators. Electricity grid losses have grown to be 7-10% of all electricity generated due to conventional technologies, and transmission limitations have caused blackouts in the United States. Efficiency and reliability will be enhanced when new transmission technologies are used that have reduced line losses, and that have the capability to carry more current for a given size of the conductor. High temperature oxide superconductors, discovered in 1986, are moving into the pre-commercial development of secondgeneration (2G) wires. The first-generation (1G) relied on bismuth strontium calcium copper oxide superconductors (BSCCO), and the second- generation is based on yttrium barium copper oxide superconductors (YBCO), which has the potential to be less expensive compared to copper wires and better performance in liquid nitrogen temperatures. Wires of 100-500 meters in length carrying currents of over 300 A/cmwidth at 77 K can now be made [1-9]. However, flux pinning and ac loss issues must be solved before a broad commercial insertion of 2G conductors can be achieved [10-12]. This book contains a total of 18 chapters which covers a wide range of both in-situ and ex-situ techniques to improve flux pinning properties in YBCO and also several ways to reduce ac loss in 2G HTS wires.