Electrical Tests and Current Distribution of 500-m-Long DC Superconducting Power Cable

The third cooling test of 500-m-long superconducting DC power transmission (SCDC) line constructed in Ishikari city, Hokkaido, was carried out in 2021. The system consists of underground superconducting cable with its electric capacities, 5kA and 100MVA. After completing two cooling tests in 2015, the system remained in a shutdown state. Therefore, this test was the first operation test in six years. The targets of the 3rd cooling test were to confirm the presence/absence of the damage due the Hokkaido Eastern Iburi Earthquake (Mj.6.7) that occurred in and acquire basic data for improving the efficiency of SCDC. Regarding electrical tests, the various tests, such as the capacitance/dielectric loss tangent temperature characteristic measurement, the insulation resistance measurement, the DC withstand voltage test, the rated current loading test were conducted to confirm the soundness of cables and the stability of current loading. One of the characteristic tests conducted this time is the current diversion test. Despite the six-year outage and the massive earthquake that occurred during that time, all tests confirmed that there was no deterioration in the performance of the cable system. In the current diversion test, it was confirmed that the current was evenly distributed to each conductor at the cable joint.