Semi-empirical correlation for quench time of inductively coupled fault current limiter

Experimental results on the quench time of an inductively coupled fault current limiter are presented. The quench time is defined as the period between the initiation of the fault and the time when the device begins to limit the current. The experimental results show that the fault current limiter begins to limit the current well before the superconductor is fully quenched. A semi-empirical model, based on a lumped-parameter circuit analysis, is developed to predict the quench time. The model assumes that the average power dissipated in the fault current limiter is used to heat up the superconductor. The derived equation indicates that the quench time depends on the properties of the superconductor, the design parameters of the fault current limiter, and the system parameters. There is very little dissipation in the superconductor when the system voltage is less than the critical voltage of the superconductor. Therefore, the over-voltage (system voltage minus the critical voltage), instead of the system voltage, should be used in calculating the quench time. The quench time calculated from the semi-empirical correlation agrees well with experimental data.