22. Development and Commercial Operation Demonstration of High-capacity Superconducting Feeding for Urban Commuter Lines

In urban commuter lines, a large number of trains run throughout the day requiring currents of several thousand amperes to be supplied. To prevent voltage drops and ensure stable power supply, many substations are required. Therefore, we developed a superconducting feeding system for urban commuter lines that eliminates electrical resistance, thereby suppressing voltage drops. The superconducting cable measures 408 meters in length and has a current capacity exceeding 8,000 amperes. To maintain its superconducting state, we adopted a Brayton cycle refrigerator with a cooling capacity of over 2 kW, suitable for large-scale applications.

We installed the developed superconducting feeding system at the Hino Civil Engineering Testing Station of the Railway Technical Research Institute (Figure 1) and conducted demonstration tests supplying electricity via the superconducting
cable to commercial trains running on an adjacent line. The system was able to handle the complex current variations during powering and regenerative braking of commercial trains operating under the line’s complex timetable. We confirmed that voltage drops were suppressed even at high current levels, up to 3,692 A during powering and 2,768 A during regeneration, demonstrating the effectiveness of the superconducting feeding system (Figure 2). Additionally, the cable temperature remained stable without being affected by the powering or regenerative braking of commercial trains, confirming that the superconducting state was maintained (Figure 3). This marked the world’s first successful demonstration of superconducting electric power transmission on a high-load urban commuter line. The superconducting feeding system allows for longer intervals between substations, enabling a reduction in substation load and the number of substations.