Superconductor power transmission

Metals and semiconductors are electronic conductors in which an electric current is carried by delocalized electrons. A metallic conductor is an electronic conductor in which the electrical conductivity decreases as the temperature is raised. A semiconductor is an electronic conductor in which the electrical conductivity increases as the temperature is raised. In most cases, a metallic conductor has a much higher electrical conductivity than a semiconductor, but it is the temperature dependence of the conductivity that distinguishes the two types of conductors. An insulator does not conduct electricity. A superconductor is a solid that has zero resistance to an electric current. Some metals become superconductors at very low temperatures, at about 20 K or less, and some compounds also show superconductivity (see Box 5.2). High-temperature superconductors have enormous technological potential because they offer the prospect of more efficient power transmission and the generation of high magnetic fields for use in transport systems (Fig. 3.42). 

For example, American Superconductor (ASC) of Westborough, Massachusetts, in conjunction with Pirelli Cable of Milan, Italy, has produced a prototype, high-temperature superconducting wire that exceeds the current-carrying threshold required for commercial underground power transmission cables. 

Snowden, Donald P., "Superconductors for Power Transmission", Scientific American, Vol. 226, No. 4, April 1972, Page 84 Ross, Marc, "Improving the Efficiency of Electricity Use in Manufacturing", Science, Vol. 244, No. 4902, April 21, 1989, Page 311... 

The applications we discuss here, in magnets, power transmission, computer interconnections, Josephson devices and instrumentation, have almost all been studied before, during two decades of active work in applied superconductivity 41. Thought of simply as a standard superconductor with a higher transition temperature, YBaCuO does not by itself imply new kinds of applications, even though it may improve the commercial prospects for applications previously burdened by overhead costs associated with helium refrigeration. More novel applications may well emerge in the future. 

E. B. Forsyth, M. Garber, J. E. Jensen, G. H. Morgan, R. B. Britton, J. R. Powell, J. P. Blewett, D. H. Gurinski and J. M. Hendrie, Factors Influencing the Choice of Superconductor in AC Power Transmission Applications, Proceedings of the Applied Superconductivity Conference, IEEE Pub. No. 72CH0682-5 TABSC, 202 (1972). 

Actually it has been known for over seventy years that certain metals and alloys, when cooled to very low temperatures (around the boiling point of liquid helium, or 4 K), lose their resistance totally. However, it is not practical to use these substances, called superconductors, for transmission of electric power because the cost of maintaining electrical cables at such low temperatures is prohibitive and would far exceed the savings from more efficient electricity transmission. 

High-temperature ceramic superconductors are also promising for the application of fault current limiter, which protects the power transmission system from the damages caused by unanticipated power disturbances. The high-temperature superconducting current limiter has tremendous benefits of... 

Superconductors find application in electrical power transmission, superfast computers, powerful electromagnets etc. 

Alumina fibers have been incorporated with aluminum, lead, and magnesium for superconductor restraints in fuston power reactors, storage battery plates, and helicopter transmission structures. 

Probably the most obvious application for superconductors is in the transmission of electrical power and it seems that that this is close to being a reality. There are many other potential applications in the power electrical engineering field, for example power generators, motors, transformers, leads and fault current-limiters. 

The early work of Garwin and Matisoo (28) focused on d.c. transmission because the hysteretic losses in superconductors of the late 1960 s made a.c. lines uneconomical. Transmission at d.c. is most favorable, however, for long lines and high powers to amortize a.c.-to-d.c. converter costs. The prospects for practical introduction of SPTL s, however, are greatest for smaller a.c. systems, on which we focus below. 

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