Construction and the Circulation Test of the 500-m and 1000-m DC Superconducting Power Cables in Ishikari

A demonstration project of the dc superconducting power transmission line using the BSCCO wires was started in Ishikari, Japan as a national project (Ishikari project) from 2013FY. In the project, two power lines have been installed. Line 1 connects a photovoltaic power plant and an Internet data center by a 500-m underground cable for practical use, whereas line 2 with a 1000-m cable will be used for verification tests. In this project, we developed a new design of an adiabatic double tube with reduced heat leaks, i. e., < 1.5 W/m. We have also adopted the Peltier current lead that drastically cuts heat transfer at the cable terminal below 35W/kA. To control the thermal contraction and expansion of the cable to avoid its breakage, we adopted two techniques, namely, a movable cryostat and a helical deformation technique. The construction was started in the field in June 2014 and completed at the end of April 2015 for line 1. Then, we performed the first cooling test for line 1 from May to June in 2015, during which we have confirmed that the thermal performance is as good as what we designed, and the current of 5 kA was successfully transported.