Transients under current overload in an ac circuit with a HTSC wire

It has been found that the loss of superconductivity in HTSC wires under ac current overload is accompanied by the change in sign of the phase difference between current and voltage. In a stabilized second-generation HTSC wire under an overload the oscillations of ac current and voltage amplitudes have been found due to the oscillations of the normal zone size in the superconducting layer. The change in sign of the phase difference can be applied for a timely registration of a normal zone nucleation in current-carrying conductors of superconducting equipment.