Quench Detection of 20-kA HTS Current Leads Using Distributed Optical Fibers

High-temperature superconducting current leads (HTSCLs) are critical components in the China's Experimental and Advanced Superconducting Tokamak and China Fusion Engineering Test Reactor, known for their slow quench propagation speed and weak quench signals. Traditionally, quench detection is primarily performed using voltage measurements. However, the real operational environment presents complex electromagnetic signal interference, rendering voltage signals unreliable for quench detection. To address this issue, we have adopted a novel quench detection method using Rayleigh backscattering based on distributed optical fiber. Optical fiber sensors offer immunity to electromagnetic interference, can endure harsh conditions (such as low temperatures and high magnetic fields), and provide a faster response time compared to voltage measurements in HTSCL systems. To simulate the actual operation of the HTSCL, we conducted quench experiments at 20 kA. The experimental results yielded a temperature distribution map from the distributed optical fiber, demonstrating its excellent performance in temperature measurement. Notably, the quench detection time using optical fiber was earlier than that using voltage measurements.