In recent years, many cities have faced an increasing power demand, while the space for urban cable channels is limited. Due to the low transmission losses at large power densities, high temperature superconducting (HTS) cables offer an increasingly attractive alternative to conventional cable solutions. HTS cables allow a simpler grid structure with less space for cable routing and lower overall cost in comparison to conventional cables. They require operation below critical values of temperature, current density and magnetic field strength of the superconductor. Since HTS materials lose their electrical resistance at temperatures close to the normal boiling point of liquid nitrogen, LN2 is a common coolant in many HTS applications.
This work presents a differential equation model for three-phase concentric HTS cables, describing the temperature distribution in the various cable layers and in the liquid nitrogen flow. The model considers the AC losses in the superconducting phases in addition to the external thermal load, as well as pressure losses in the coolant flow. The integrity of the algorithm is verified through energy cons ... mehrervation, yielding negligible numerical solver errors. The final application study shows options for extending the cable length up to factor five, using a second cooling unit in combination with a mixed coolant.