Transport characteristics of the 100 m KEPCO HTS cable system for balanced three-phase currents

Abstract

Since a 100m, 22.9kV/50MVA high temperature superconductor (HTS) cable system was installed at the Gochang test yard of Korea Electric Power Corp. (KEPCO) in 2005, a long-term test has been performed. In this paper, the transport characteristics of the KEPCO HTS cable system were examined by the electrical and calorimetric methods. To analyze the shield current in this system, an equivalent circuit model for the KEPCO HTS cable was suggested, and the calculated shield current compared with the measured one.The results show that the electrically measured total loss, which includes the AC and ohmic losses, corresponds well with the loss measured from the calorimetric method. The measured AC loss of the HTS cable is proportional to the 2.5th power of transport current, and four times larger than the conductor loss calculated from the monoblock model. This is because the conductor’s geometry in the HTS cable is not identical to a cylindrical superconductor in the monoblock model, its temperature rises due to a thick insulator, and the shield loss is included in the measured AC loss. In addition, the measured AC resistance of the current-lead is constant regardless of transport current, particularly in the low current region. Finally, the shield current calculated from our equivalent circuit model is in good agreement with the measured one.