Temperature and Pressure Distribution Simulations of 3-km-Long High-Temperature Superconducting Power Cable System with Fault Current for 66-kV-Class Transmission Lines

A computer program has been developed by numerically solving the nonlinear heat conduction and heat transfer equations, which are discretized using the finite difference method, to calculate the temperature and pressure distributions in high-temperature superconducting (HTS) power cables cooled using liquid nitrogen (LN₂). The LN₂ coolant properties are estimated using Cryodata's GASPAK software package. This evaluation of the temperature and pressure distributions is important to understand how we can make practical use of HTS power cables and to assess the effects of short-circuit accidents. To incorporate HTS power cables into real grids, it is necessary to evaluate HTS power cables that are a few kilometers long. In this study, 3-km-long HTS cables were evaluated using our proposed computer program. This program was used to model the cooling system, ac loss, dielectric loss, and intermediate-joint losses. The results revealed that the temperature of the LN₂ coolant at the cable outlet could reach the saturation temperature when a fault current of 31.5 kA flowed for 2 s (worst case for the 66-kV-class transmission lines in Japan). From the results, it was also clear that the effects of the ac loss, dielectric loss, and intermediate-joint losses on the increase in the temperature of the LN₂ coolant could not be ignored.