Recovery characteristics of fault current limiter with adjustable trigger current level

A superconducting fault current limiter (SCFCL) of a transformer type with adjustable trigger current level is proposed. A trial SCFCL of this type is designed and made. Basic tests on the SCFCL are carried out. The current limiting impedance of SCFCL of the transformer type is almost determined by an inductance of a primary coil. The trigger current level and recovery characteristics of the SCFCL depends upon the design of a secondary coil. In this paper, recovery characteristics of the proposed SCFCL are studied experimentally. Joule heat in the secondary winding in the current limiting mode is measured. It is pointed out that the resistance of the secondary winding, that is the normal zone length, decreases as the line current decreases. Problems in the design of secondary windings are discussed. It is confirmed that the trial SCFCL recovers successfully from the current limiting mode to the waiting mode in shorter than ten cycles.