We have been developing an AC power source with a high-temperature superconducting (HTS) transformer
that is small and can supply a large AC current. The HTS transformer needs a detection system of normal
transition for high reliability. We have proposed the active power method as the detection system. The system
enabled early detection of the normal transition in a secondary coil of the transformer, which was wound with a
bundle of some HTS tapes. However, we could not identify the normally transited HTS tape in bundle conductors
using the conventional method. Therefore, in this paper, we propose a method to identify the normally transited
HTS tape in the bundle conductor by improving the active power method. The improved method is based on
measuring the active power in each HTS tape in the bundle conductor. Experiment results show that the proposed
method works successfully for early and accurate identification under outputting a secondary maximum current
of 1 kApeak at 1 kHz.
