Quench detection and early warning based on thermoelastic strain rate for HTS tapes thermally triggered by heat spots

Abstract

The rapid detection and comprehensive monitoring of quench onset and evolution in high-temperature superconducting (HTS) materials remain immensely challenging because the normal zone propagation velocity in HTS materials is two or three orders of magnitude less than that in low-temperature superconductors. In this study, we experimentally and numerically explore quench events triggered by heat spots in yttrium barium copper oxide HTS tapes to characterize the quench onset and propagation. A multiplexed fiber Bragg grating sensor with multiple gratings was used to perform highly accurate strain measurements. Conventional voltage and temperature measurements were performed synchronously on the HTS tapes. A systematic comparison of these multifield signals during quench onset and development illustrated that the evolution of thermoelastic strain and strain-rate in HTS tapes captures the quench onset and propagation. A distinct feature was exhibited during the quenching of a pre-tensioned HTS tape: the thermoelastic strain initially relaxed but subsequently increased until the strain rate exhibited a significant slope change, which corresponded to the quench onset time. The thermoelastic strain in a nearly unconstrained HTS tape gradually increased until quenching occurred. A prominent characteristic for detecting quench onset in HTS materials have been revealed based on the change in the slope of the thermoelastic strain-rate or the second derivative of the strain remaining nearly constant. For a pre-tensioned HTS tape, the minimization of the thermoelastic strain or the strain-rate becoming zero may be a predictor that preceded the quench by 1–2 s, which can be, to a certain extent, regarded as an early warning. Another important and novel result was the experimental demonstration of global strain responses distant from the quench location in the pre-tensioned HTS tape, while the temperature and voltage detection are commonly localized methods. The mechanism behind these thermoelastic strain characteristics was further discussed and simulated from the induced Joule heating throughout the quench event. The measurements and numerical predictions suggested a new paradigm of quench detection based on the thermoelastic strain-rate in HTS materials.

Unraveling quench dynamics and real-time continuous detection in HTS tapes through distributed fiber optic sensing

“…This implies that the inflection point of the thermal strain-rate can serve as a criterion for identifying quench events in HTS materials. This finding aligns with the phenomenon and criterion proposed in previous literatures [15,34], further validating the experimental observations. Moreover, the temperature rate also undergoes a significant change in slope during the quench process.…”

“…However, in contrast to LTS materials, HTS materials exhibit a relatively slow voltage transition during quench caused by overcurrent. The 1 µV cm −1 criterion provides an empirical guideline with considerable redundancy, which may even result in misjudgment of quench [34,37].…”

“…In their study, low-temperature strain gauges were employed to measure the overall magnetic-thermomechanical behavior of superconducting magnets during excitation. Additionally, Chen et al [34] investigated quench events triggered by hot spots in yttrium-barium-copper-oxide (YBCO) tapes through experimental and numerical simulations, employing FBGs for high-precision strain measurement to characterize quench onset and propagation. A notable feature for quench initiation detection in HTS materials is the nearly constant change in the slope of the thermoelastic strain rate or second derivative of the strain.…”