Magneto-thermal coupling modeling for the stability analysis of a 110 kV/3 kA high temperature superconducting cable under fault current conditions

In the power grid, the cold dielectric hightemperature superconducting (CD HTS) cable frequently subjects to overcurrents caused by the shortcircuit fault. During the fault, a large amount of Joule heat is generated. The heat causes the temperature of the HTS cable to rise and leads to the transition of the HTS cable from superconducting state to normal state which would influence the current carrying capacity of the HTS cable seriously. An algorithm has been proposed to calculate the transient current distributions of superconducting layers in fault conditions. This method couples an equivalent circuit model and a thermal model. So the temperature distributions in HTS cable is obtained based on the heat generated by the fault current. Finally, the current and temperature distributions of a 110 kV/3 kA CD HTS cable are investigated with a fault current impact of 25 kA _rms for 3 s. The results show that the currents of the conducting layers decrease while the temperature increases in the HTS cable and the former withstands most of the fault current impacts. The current in the former of the HTS cable changes from zero to about 90 % of the fault current. A current diversion effect in the HTS cable is obvious. The conclusions provide the basis for the protection strategy of superconducting cable considering fault current impact and will be a benefit to the stable operation of a superconducting transmission grid.