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Description
The ITER project represents a cornerstone of the global effort to achieve controlled thermonuclear fusion, with the objective of demonstrating the feasibility of sustaining a burning plasma and paving the way for future fusion power plants. Among its most critical subsystems are the Toroidal Field (TF) magnets, massive superconducting coils responsible for generating the strong and steady toroidal magnetic field necessary to confine the plasma. Owing to their large stored energy, intricate structure, and complex electrical environment, understanding their electromagnetic behavior, particularly under fault conditions, is essential to ensure safe and reliable operation.
This work presents a comprehensive analysis of fault scenarios in an ITER TF magnet. The TF coil model, implemented in Simulink, integrates the detailed electrical network of the TF magnet, the ground connections, and the Fast Discharge Unit (FDU), enabling the simulation of fault behavior during a fast discharge event. Several practically relevant fault cases were investigated, including magnet terminal–to–ground faults, double pancake joint–to–ground faults, double pancake joint–to–radial plate faults, and radial plate–to–ground faults. The primary objective was to identify the highest voltages arising during these events so that protection systems can be calibrated accordingly, preventing the possibility of subsequent cascading faults triggered by the initial failure.
A particular focus was placed on assessing the influence of distributed capacitances throughout the system. The analysis demonstrates that capacitive effects substantially shape the transient response, giving rise to overvoltage and oscillatory behavior during fault events. These resonance phenomena are shown to be linked not only to the model of the TF itself but also to the fast discharge unit (FDU) connected to it. The results highlight that a realistic model including all parasitic capacitances, both in the TF coil and in the FDU, is essential to evaluate the severity of fault-induced transients and to ensure that the insulation and protection design of the TF magnet system remains robust under all credible fault scenarios.
