Speaker
Qiaosen Wang
(State Key Laboratory of Electrical Insulation and Power Equipment)
Description
Superconducting magnet is one of the most crucial components in a superconducting Tokamak. During the normal operation stage, high current of some tens of kA flows through the magnet with large inductance of ~1H. Therefore, extremely large energy (~0.1-10GJ) is stored in the magnet, which must be dissipated in the case of magnet quench in certain duration before the occurrence of local or even overall damage of the magnet. The task of a quench protection switch (QPS) is to transfer the high current from the low-resistance branch to another one with a dump resistance, through which the energy is dissipated. A QPS based on the principle of artificial current zero has been proposed. The full QPS consists of four branches, i.e., the by-pass switch (BPS), the main circuit breaker (MCB), the dump resistance (DR), and the commutation branch (CB), which includes a capacitor, a inductor, and a commutation switch connected in series. In present work, the detailed current commutation process after the current is transferred from the BPS to MCB is investigated by a circuit model. Then, the influence of the frequency of countercurrent and the value of the dump resistance on the characteristics of quench protection is analyzed. The simulation results indicate that the commutation duration can be decreased slightly by increasing the frequency of countercurrent. However, the decrease of frequency of countercurrent can lower the current decreasing rate before current zero of the MCB, which benefits a successful interruption of the MCB and the reliability of the QPS. Furthermore, it indicates that the voltage across the superconducting coil decreases with the decrease of the dump resistance. However, from another point of view, a larger dump resistance can reduce the overvoltage across the commutation switch, which also benefits a reliable protection.
Co-authors
Lijun Wang
(State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China)
Qiaosen Wang
(State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China)
Sheng Li
(State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China)
Shenli Jia
(State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China)
Zhanpeng Gao
(State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China)
Zongqian Shi
(State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China)
