Abstract
The Normal zone propagation velocity (NZPV) of a double-layer second generation high temperature superconducting wire manufactured by American Superconductor has been measured by electrical and thermal methods, and the results have been compared and discussed. The NZPV values determined by the voltage traces are ranging from 3.8 mm/s at 0.4 I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> to 19.2 mm/s at 0.9 I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ; while from 5.9 to 18.3 mm/s by the temperature traces. NZPV determined by these two approaches agrees well with each other. Also, NZPV of double-layer YBCO tape is close to that of conventional single-layer superconducting tape.
Highlights
FOR THE DESIGN and implementation of commercial applications such as superconducting fault current limiters and superconducting magnets [1, 2] using second generation (2G) high temperature superconducting (HTS) wires, a comprehensive understanding of the thermal stability of 2] using second generation (2G)-HTS wires under different conditions of transport current and ambient magnetic fields is required
In order to quantitatively estimate the performance of a 2GHTS wire, it is important to determine the propagation speed at which the thermal instability travels along the length of a testing sample, known as normal zone propagation velocity (NZPV)
In order to propagate the normal zone along the entire conductor, and determine the NZPV, the sample was quenched with a high end-to-end voltage
Summary
FOR THE DESIGN and implementation of commercial applications such as superconducting fault current limiters and superconducting magnets [1, 2] using second generation (2G) high temperature superconducting (HTS) wires, a comprehensive understanding of the thermal stability of 2G-HTS wires under different conditions of transport current and ambient magnetic fields is required. It is well recognized that one of the major issues involving the use of 2G-HTS wires is the formation of destructive hot spots, or localized thermal instabilities, due to the ineluctable presence of flaws in the microstructure of the superconducting composite. In order to quantitatively estimate the performance of a 2GHTS wire, it is important to determine the propagation speed at which the thermal instability travels along the length of a testing sample, known as normal zone propagation velocity (NZPV). To assess the NZPV in a 2G-HTS wire, the voltage rise at different positions along the sample length are measured. Extensive efforts have been pursued in the past in order to determine the NZPV of different superconductors under The typical values obtained are in the order of 10-3 – 10-2 m/s [3, 4] which is two to three orders of magnitude slower than that in low Tc counterparts [5].
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