• high-temperature superconducting power apparatus;
  • composite insulating system;
  • liquid nitrogen;
  • insulating paper;
  • ice;
  • electric breakdown


In recent years, research on the development of high-temperature superconducting cables has advanced. The application of a composite insulating system made of insulating paper-liquid nitrogen has been studied as an electrical insulating system for high-temperature superconducting cables. In paper-liquid nitrogen composite insulating systems developed on the basis of conventional techniques, microscopic bubbles easily remain inside the paper, and the partial discharge are supposed to occur easily. In order to overcome this drawback, we formulated a paper-ice composite insulating system as a substitute for the paper-LN2 of the cryogenic electrical insulating system in high-temperature superconducting cables. In this study, the breakdown strength, partial discharge, V-t characteristics, effect of pressure on breakdown characteristics, and the self-healing breakdown characteristics of a paper-ice composite insulating system were investigated in order to understand the basic properties of new insulating materials for applications to high-temperature superconducting cables. As a result, it was clarified that the AC breakdown strength of paper-ice composite insulating system was higher than that of paper-liquid nitrogen insulating system, and that of paper-ice composite insulating system exhibited a self-healing type. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.