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A model superconducting fault current limiter (SFCL) with high-speed communication switch is discussed. Findings reveal that the model SFCL is able to decrease the temperature rise for adapting the high-speed circuit breaker and is also able to reduce the heat load of the superconductor.

The current limiting properties of the metal organic deposition Y[Ba.sub.2][Cu.sub.3][O.sub.7] (MOD-YBCO) thin films with high-resistivity alloy shunt layer are discussed. These films are capable of withstanding high electric fields and can be easily used in fault current limiters.

Tests on the ITER project are described and discussed.

A dc superconducting to normal transition type three phase fault current limiter, consisting of superconducting material Bi-2223, was developed.

Research was conducted to examine alternating current (ac) losses in high temperature superconducting coil carrying ac transport current. The electrical method was used to test ac losses at 77 K and 4.2 K. Calculated ac losses were compared with the conventional theory based on the critical state model. Theoretical results were in agreement with experimental results particularly in the region of low transport current.

Quench tests were conducted using the time-frequency distribution of acoustic emission signals enabling a NbTi superconducting winding cooled in liquid helium to rotate. Acoustic emission converters were used for data acquisition for voltages in the superconducting winding. A comparison of the acoustic emission signals during a quench propagation with those of a non-quench case was performed to investigate the acoustic emission components resulting from only the quench propagation.

A study was conducted to analyze the association between acoustic emission signals induced from an ac superconducting coil and normal components in the superconducting winding during quenching. The coil was impregnated with epoxy to prevent wire motion. Results indicated that increases in acoustic emission during quenching correlated with increases in the high rate of the normal components in the superconducting winding.

Conductor configuration and characteristics of superconducting cable for 50Hz a.c. use are reported. We developed a.c. conductors aiming low loss kA class current capacity. In consideration of reducing the current degradation by cabling, structures suitable for a.c. conductor are designed. In these conductors, low loss a.c. superconducting wires with very fine NbTi filaments are stranded around central cable of Cu-Ni or stainless steel wires for equal cooling condition, equal current distribution and mechanical reinforcing. Characteristics of small coils with these conductor at 50Hz a.c. load are tested and reported.

Stabilities of magnets in a high gravitational field up to 2000 G are discussed, based upon the experimental results of forced quench tests in a set of rotating magnets, in order to establish the stability design criterion of field windings of superconducting generators. Relations of propagation velocities, recovery currents, minimum quench energy and heat transfer characteristics are studied, a good agreement between the experimental results and a theory confirmed the improvement of magnet stability in a high gravitational field because of the enhanced heat transfer characteristics.

The technological progress of power frequency ac superconductor is remarkable and application studies are being carried out, targeting ac super-conducting (SC) machines for power systems. The introduction of SC machines into the power system, needs to display the merits of not only efficiency improvement but also power system performance and operation. A conceptual design for a coreless super-conducting transformer (SCT) is made, based on the above views and it's merits evaluated. A future possible power system employing coreless SCT's is presented, and consideration is given to the actual service in a future power system. Index Terms--Coreless superconducting transformer, exciting current, shunt reactor, fault current limiter, ac superconductor, low temperature electrical insulation, power system.