7.2 Superconductor Technology in the Future
167
Fig. 7.6 Structure of a
superconducting power cable
in which the excess current
flowing in copper layers
decreases the longitudinal
magnetic field to decrease
the critical current density in
the superconducting layers
each conductor to decrease the longitudinal magnetic field when the excess current
flows in the copper layer.
A critical current density that increases with increasing longitudinal magnetic
field, as shown in Fig. 6.8a, has been obtained for short samples of REBCO tapes.
Its value for long commercial REBCO tapes is, however, almost flat or slightly
decreasing with increasing longitudinal magnetic field. Hence, the improvement of
the current-carrying capacity of a new-type cable is not so dramatic, as shown in
Fig. 7.5, although it is appreciably higher than that in the usual cables [3]. This is
probably caused by defects that disturb uniform current transportation in commercial
tapes. Improvement of the current-carrying property of commercial tapes, which will
realize a dramatic improvement in the cable performance, is expected in the future.
Superconducting instruments, such as generators, transformers, magnetic energy
storage devices, fault current limiters, etc., that compose the electric power grid with
generation using renewable energy are being developed now. Especially for the case
of high power generation using wind turbines, reduction in size of generators is
strongly required, and the application of superconducting generators is expected.
167
Fig. 7.6 Structure of a
superconducting power cable
in which the excess current
flowing in copper layers
decreases the longitudinal
magnetic field to decrease
the critical current density in
the superconducting layers
each conductor to decrease the longitudinal magnetic field when the excess current
flows in the copper layer.
A critical current density that increases with increasing longitudinal magnetic
field, as shown in Fig. 6.8a, has been obtained for short samples of REBCO tapes.
Its value for long commercial REBCO tapes is, however, almost flat or slightly
decreasing with increasing longitudinal magnetic field. Hence, the improvement of
the current-carrying capacity of a new-type cable is not so dramatic, as shown in
Fig. 7.5, although it is appreciably higher than that in the usual cables [3]. This is
probably caused by defects that disturb uniform current transportation in commercial
tapes. Improvement of the current-carrying property of commercial tapes, which will
realize a dramatic improvement in the cable performance, is expected in the future.
Superconducting instruments, such as generators, transformers, magnetic energy
storage devices, fault current limiters, etc., that compose the electric power grid with
generation using renewable energy are being developed now. Especially for the case
of high power generation using wind turbines, reduction in size of generators is
strongly required, and the application of superconducting generators is expected.