Research on grounding protection system of the central solenoid model coil of the CRAFT

This work presents a grounding protection system of the central solenoid model coil (CSMC) of the Comprehensive Research Facility for Fusion Technology (CRAFT). The scheme of neutral point voltage detections has been adopted in grounding protection system. Compared with the usual current acquisition, the measurement data is accurate, there is no redundant loop, and the economic benefit is high. In this study, the single-end and double-end grounding fault protections of superconducting magnet coil are analyzed, and the fault voltage and current under different fault conditions are calculated. The simulation model of CSMC magnet grounding fault is established, and the simulation results of the model are basically consistent with the theoretical calculation. Finally, a small capacity experiment platform is used to verify the function of the grounding protection system. The experimental results show that by comparing the neutral fault sampling voltage with the theoretical grounding protection threshold, the grounding protection system can effectively detect different types of grounding faults and transmit signals to the control system to protect the coils of superconducting magnets.