23. Verification of commercial line operation using a superconducting feeding system
Superconducting feeding systems are expected to consolidate and reduce the number of substations and reduce power consumption through zero resistance power transmission. We have been developing a superconducting feeding system and verifying its functionality on the main line by testing its ability to transmit power to a single test run train without passengers during the night after business hours.
However, on actual commercial lines, multiple trains operate under various conditions, such as express train and local train services.
Therefore, it is essential to evaluate the system's adaptability and reliability under complex changes in load current.
In addition, if installation between substations is assumed, the refrigerator must be downsized to fit along the railway line.
Therefore, we first developed a compact refrigerator with high cooling capacity suitable for installation along railway lines. By efficiently operating the Stirling cycle, the refrigerator's cooling capacity per unit volume has been increased to 0.47 kW/m3, about three times that of the conventional model (0.15 kW/m3). This downsized unit, with a cooling capacity of 1.5 kW, can be installed in a space of approximately 1.8 m2 (Figure 1).
Next, we confirmed that the superconducting feeding system complies with technical standards for operational verification during business hours and obtained approval from the Ministry of Land, Infrastructure, Transport and Tourism. A superconducting feeding system consisting of the developed refrigerator and superconducting cables was installed along a railway line, and it was confirmed that the 102-meter-long superconducting cable could be stably cooled to superconductivity operation temperature (Figure 2).
The system supplied power to a total of 135 trains per day (67 trains in the inbound direction and 68 trains in the outbound direction), and confirmed that the developed superconducting feeding system can stably transmit the load current, which changes in a complex manner due to multiple trains running during business hours (Figure 3).
