Quench Detection Based on Voltage Measurement for the KSTAR Superconducting Coils

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.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Chen¹,

Guan²,

Tong³

et al. 2022

“…However, the quench and its detection method are still the main issues and tough challenges that restrict the growing application of superconducting materials, especially for high-field magnets. The resistive voltage quench detection method, as a universally used technique, has been widely studied for lowtemperature superconducting (LTS) systems [5][6][7][8][9], which is performed by voltage taps to measure abnormal voltage signals. High temperature superconducting (HTS) materials have abundant application prospects due to their higher cryogenic stability and optimum performance indicators such as much higher critical current, operation temperature and magnetic field.…”

Section: Introductionmentioning

confidence: 99%

A visual and full-field method for detecting quench and normal zone propagation in HTS tapes

Wang¹,

Guan²,

Chen³

et al. 2021

A fast and effective quench detection method is especially challenging in the development of high-field high-temperature superconducting (HTS) magnets for their safe operations and reliably releasing the stored energy during a quench. The occurrence and propagation of a quench are often accompanied by strong thermal and magneto-mechanical responses within superconducting magnets. Aiming to detect a quench in the whole process and capture the thermoelastic behavior associated with it, a new detection technique with a visual and full-field perception based on the digital image correlation (DIC) method is proposed in the present study. The experiment of a quench triggered thermally by a local spot heater is conducted for a YBCO coated conductor tape in a cryogenic chamber. The evolution and characteristics of the full-field strain in the HTS tape during the processes of a non-quench, a quench occurrence and quench propagation are intuitively presented with experimental observations. For the comparison purpose, the conventional quench detection methods by monitoring temperature and voltage signals during a quench are also utilized experimentally. The results verify the visual and full-field quench detection method which uses a criterion of thermoelastic strain-rate for the quench occurrence and the evolution of strain contours for the normal zone propagating aspect. Additionally, a numerical quench model of coupled thermoelasticity to simulate the experiment is established and solved with the aid of Comsol multiphysics software. The quantitative results are in good agreement with the experimental measurements to prove the reliability and availability of the developed detection method. Since the DIC method is non-contact and insensitivity to intense electromagnetic interferences, it is expected to provide a new technique on quench issues and some basic measurements on strain/stress behaviors in extreme environments of high-field HTS magnets in the future.

“…Non-electrical methods include monitoring temperature using optical fiber [29][30][31][32][33], stress and strain [34,35], acoustic signals [36][37][38][39] and variation of capacitances [40,41]. Electrical quench detection methods are mainly based on sensing the resistive voltages in magnets, including the direct monitoring method [42,43], bridge method [44] and voltage pickup method [45]. Although electrical methods are more mature and straightforward compared to non-electrical approaches, the sensitivity has yet to be improved, since identifying a weak resistive voltage signal from strong background inductive voltage noise is always challenging.…”

Section: Introductionmentioning

confidence: 99%

A quench detection method for parallel co-wound HTS coils based on current redistribution

Hu,

Lin,

Tan

et al. 2024

High-temperature superconducting (HTS) coated conductors (CCs) have become the preferred material for superconducting magnet applications due to their high engineering current density and high mechanical strength. However, due to low quench zone propagation velocity of CCs, magnets wound with CCs suffered from severe quench risks. Therefore, a rapid, sensitive, and reliable quench detection method is crucial for the safe operation of such HTS magnets. In this paper, we propose a quench detection method based on current redistribution, in which two pieces of HTS CCs are soldered together at each end and insulated in the middle part. then parallel co-wound into a double-pancake coil. The two tightly coupled windings and low resistance joints form a very low inductance current loop, resulting in fast current redistribution between the two co-windings even at at inception of quench ( with still low quench voltage ). We deducted analytical solutions of the current redistribution process under different magnet operational scenarios, including constant current operation, charging and discharging, and proposed quench detection criteria. Corresponding quench tests were done on a small scale co-wound HTS coil, and results well verified the analytical solutions and the effectiveness of the quench detection method. The work may be useful for lowering the risk of HTS magnet quench in various applications.