Iron-Steel Cryogenic Pipe for DC Superconducting Power Transmission Line

The 200-meter DC cable test facility was constructed in Chubu University. The cryogenic pipe is composed of two pipes, and the material of the inner pipe is stainless steel (SS304). The outer pipe is the straight pipe, and made from the iron steel because of high strength, low cost and not low temperature. If the cable structure is co-axial, the magnetic field is not generated outside the cable, and the ferromagnetism of the iron steel is not affected to the electric circuit. However, if the single core cable is used, the ferromagnetic effect of the outer pipe should be considered. Therefore, we measured the inductances of the cable after the construction of the experimental device. The measured inductance of the co-axial cable is matched with the analytical value, and it is very small. But the measured inductance of the single core cable configuration, it is 0. 4 mH. This is a large value, and therefore we can save the inductor in the power converter. Moreover, the energy storage can be available in the grid power line if large current operation is used.