Time–Frequency-Based Quench Detection for HTS VIPER Cable Using Torsional Acoustic Wave

A new quench detection and diagnostic system is required for the reliable operation of high-field superconducting magnets for fusion which is fabricated with high-temperature superconductor (HTS) cables. The conventional voltage-based diagnostic methods have a limitation in detecting local temperature changes in large-scale HTS magnets. To address the limitation, an acoustic-based diagnostic method using torsional waves applied by piezoelectric transducers is proposed. In addition, from the sensor data collected by the piezoelectric transducers, a new monitoring index that can measure the temperature change is extracted via chirplet transform (CT), which is one of the time–frequency analyses. The proposed quench detection method using torsional wave guiding is implemented in a vacuum pressure-impregnated, insulated, partial dislocation, extruded, and roll-formed (VIPER) cable, and the performance of the new index, time–frequency-based phase delay, is validated. This work proves that the propagation characteristics of torsional acoustic waves depend on the strength and location of the heat and that the change can be monitored via the proposed time–frequency-based phase delay. The preliminary development and results of a new quench detection method are discussed to validate future use in complex environments such as fusion power plants.