Critical Current Equalization via Neutral Lines in a Transformer-Type SFCL

In order to increase the capacity of the superconducting fault current limiter (SFCL), serial and parallel connections of the superconducting units are necessary. The resistive-type SFCL with serial and parallel connections has the unbalance of power burden because of the difference of critical current between the superconducting units. The transformer-type SFCL using a neutral line consists of a primary coil and several secondary coils with the superconducting units. Because the neutral line is connected with the secondary coils in the SFCL, it induces the simultaneous quench from compulsive current distribution in the superconducting units. The simultaneous quench enables the power burden between the superconducting units to be distributed equally. The neutral line also induces the equal voltage distribution between the superconducting units due to the equal turn´s ratio of the secondary coil. In conclusion, the increase of the capacity in the transformer-type SFCL could be achieved easily through the application of the neutral line between the secondary coils and the superconducting units.