中国聚变工程实验堆（CFETR）是中国自主设计的下一代聚变装置，其超导线圈的电流最大达到100 kA。失超保护系统尤其是直流保护开关的可靠性对于超导线圈的保护极为重要。分析了系统中泄能回路参数对CFETR失超保护开关的动作可靠性影响，首先通过理论计算分析杂散参数对开关动作的影响趋势，然后通过仿真求解关断过程中各支路电流电压来验证计算。计算结果证明，较大的泄能支路杂散参数将改变直流开关的关断参数，并降低直流保护开关的动作可靠性。最后对泄能电阻杂散电感提出小于120 μH的设计要求，确保系统安全可靠地运行。

China fusion engineering test reactor(CFETR) is a magnetic confinement fusion device designed, which used high current magnetic field in the superconducting coil to generate high intensity magnetic field, thus constraining the high-temperature plasma to conduct fusion experiments. Therefore, the reliability of quench protection system, especially DC protection switch, is very important for the protection of the superconducting coil. However, the reliability of the DC protection switch is affected by many factors, including the action time, the speed of arc extinguishing, the current drop rate of the switch and the voltage rise rate around zero-crossing point. In the literature on quench protection system design of Tokamak devices such as international thermonuclear experimental reactor (ITER), the influence of circuit stray parameters on switch reliability is rarely described, and the influence of discharge circuit to quench protection system is less. However, the larger stray parameters of discharge circuit will greatly reduce the operational reliability of the DC protection switch and even lead to failure and damage of the switch. In this paper, the influence of the parameters of the discharge branch on the reliability of the quench protection system in CFETR is analyzed. Firstly, the influence factors and the influence trend are analyzed by theoretical calculation, and the correctness of the theoretical analysis of the current and voltage of each branch is carried out in a set of simulations. The simulation results show that when the stray inductance of discharge branch is large, the turnoff parameters of each branch will be greatly impacted, which directly affects the reliability quench protection system in CFETR.