Heat leak and pressure drop measurements of the 1000 m class superconducting DC power transmission system in Ishikari

The second cooling test of the 1000 m class superconducting DC power transmission system constructed in Ishikari, Japan, was performed in 2016. In this cooling test, the heat leaks to the low temperature parts and the pressure drops of the liquid nitrogen circulation were measured for each section of the 1000 m system. The heat leaks were measured at different outer pipe temperatures of the cryogenic pipe constituting the transmission line. The total heat leaks of the cable system, composed by the cryogenic pipe and the terminals, were 1.746 and 2.091 kW at the outer pipe temperatures of -2.4 and 17.4 degrees C, respectively, which were consistent with those measured in the first cooling test. The heat leak of the cryogenic pipe increased by 30-40 % by the increase of the outer pipe temperature from -2.4 and 17.4 degrees C. The pressure drop of the cable system was 42.80 kPa and that of all the system, including the cooling system, was 98.4 kPa at the flow rate of 36.03 L/min. The degradation of the heat leak and pressure drop characteristics were not observed between the first and second cooling tests. Based on the present results, the heat leak, the temperature rise and the pressure drop of 10 km systems were estimated. From this estimation it can be said that the cooling and the circulation of 10 km systems are possible by the present level of technology.