Abstract
Research and demonstrations of the near-future use of high-temperature superconducting (HTS) cable as a transmission power cable has been conducted in many countries. Our study focused on a HTS tri-axial cable composed of three concentric phases. A tri-axial cable is more advantageous than a co-axial cable that is composed of three cores in one cryostat. Since conventional tri-axial cables have not realized three-phase equilibrium, we proposed a tri-axial cable composed of two longitudinal sections with different twist pitches. The characteristics of the balanced tri-axial cable were not clear, so we studied AC loss and fault current behavior of the balanced model. On the other hand, there have been no reports of the analysis of heat transfer for the balanced tri-axial cable in steady state operation. The steady state analysis is important for operating a HTS cable for a long time stably and for optimization of the cable structure. In this paper, we analyzed the temperature distribution in the balanced tri-axial cable using a finite difference method. AC losses and fluid characteristics were considered in this analysis. Since a tri-axial cable has two LN2 channels, we considered four types of cooling methods that have different LN2 streams and locations of refrigerators. In the LN2 stream, parallel flow and counter flow were adopted in this analysis. We investigated the cooling characteristics of an HTS tri-axial cable considering heat transfer and fluid properties.
