Temporal resistance variation of the second generation HTS tape during superconducting-to-normal state transition
BackgroundThe quench process in high-temperature superconducting (HTS) wires plays an important role in superconducting power devices, such as fault current limiters, magnets, cables, etc. The superconducting device should survive after the overheating due to quench.MethodsWe studied the evolution of the resistance of the YBCO tape wire during the quench process with 1 ms time resolution for various excitation voltages.FindingsThe resistive normal zone was found to be located in a domain of about 1-4 cm long. The normal state nucleation begins in 40-60 ms after voltage is applied across the HTS tape. In subsequent 200-300 ms other normal state regions appear. The normal domain heating continues in the following 5-10s that results in a factor of 2–3 increase of its resistance.ConclusionsFormation of the normal domain during the quench process follows the same stages for different excitation voltages. Characteristic domain sizes, lifetimes and temperatures are determined for all stages.
Stable Overload Operation of High-Temperature Superconductor Protective Resistors
The use of high-temperature superconductor (HTS) resistors to protect electrical equipment and ac networks from emergency short-circuit currents and single phase-to-ground faults has been considered. It has been proposed to use a stable overload operation in HTS composite wires to enhance the speed of response and thermal stability of HTS current-limiting devices. Design solutions for the use of stabilized low-resistance HTS wires in protective resistors for ac networks have been developed that increase the resistance inserted in the circuit by several orders of magnitude. The characteristics of first-generation HTS wires with high critical parameters in the resistive state have been measured in a wide current overload range. Prototypes of instantaneous thermally stable current-limiting devices with HTS protective resistors have been fabricated and tested. The design parameters of HTS protective resistors for use in electric power networks have been calculated.
Evaluation of the Normal-Zone Propagation Characteristics of REBCO Coated Conductors With Laminated Cu Tape
The quench characteristics, particularly the normal-zone propagation and increase in hot-spot temperature, of REBa2Cu3Ox (REBCO) coated conductors are important issues for safe operation in the superconducting applications. Although experimental data on the quench characteristics of REBCO coated conductors have been reported only limited data is available specifically on REBCO coated conductors laminated with Cu tape of thickness no less than 0.1 mm, which are expected to be used for high-current operation in future superconducting applications. Here we reported experimental measurements of the normal-zone propagation velocity (NZPV) in REBCO coated conductors laminated with Cu tape of 0.1 mm thickness at 77, 65 and 50 K in a background magnetic field. We also compared these results with the NZPV at 77 K of REBCO coated conductors laminated with Cu stabilizer tape of thickness 0.05 and 0.3 mm.