直流真空断路器弧后介质恢复特性影响因素分析

直流真空断路器采用人工过零的方式实现故障开断，是当前直流系统兼具经济性与可靠性的控保方式之一，其弧后介质恢复特性是判定故障开断成功与否的关键条件。为探究直流真空断路器电磁与机电参数耦合作用下介质恢复特性的影响因素，本文基于连续过渡模型、能量守恒定律和电荷守恒定律，建立了零区带电粒子数密度计算模型，研究了触头型面参数和零前电流下降率影响下的零区带电粒子数密度分布；通过搭建12 kV直流真空断路器配永磁斥力机构运动特性测试平台，实验测得机构位移-时间特性曲线，研究了短路开断电流、零前电流下降率和换流投入时刻影响下的零区极间距分布。在此基础上，基于漂移扩散方程、Maxwell-Stefan方程和泊松方程，建立了弧后鞘层发展模型，以求得电磁与机电参数影响下的电场强度最大值；并与零区金属蒸气压和短路开断电流影响下的临界击穿电场强度进行对比分析，进而评估不同换流投入时刻、零前电流下降率、暂态电压上升率、触头直径下的弧后介质恢复强度。此外，求得了直流真空断路器可靠开断时零前电流下降率和换流投入时刻的极限安全域，以及电磁与机电参数耦合作用下的最小安全间隙与开断电流极限，为设计满足可靠开断要求的直流真空断路器灭弧系统结构参数与换流参数群组提供解决方案。

Analysis of the Influence Factors of Post-Arc Dielectric Recovery on DC Vacuum Circuit Breaker

The DC vacuum circuit breaker adopts the artificial zero crossing commutation mode to interrupt the DC fault current, which is one of the economical and reliable control and protection methods in DC system. And the post-arc dielectric recovery characteristic of vacuum circuit breaker is the key to determine the fault breaking capability. In order to research the influencing factors of dielectric recovery under the coupling effect of electromagnetic and electromechanical parameters in DC vacuum circuit breakers, based on continuous transition model, law of conservation of energy and law of conservation of electric charge, the calculation model of charged particle number density in the current zero zone was established to study the distribution of the charged particle number density under contact contour parameters and pre-zero current drop rate. And by constructing a motion characteristic testing experimental platform for a 12 kV DC vacuum circuit breaker equipped with permanent magnet repulsion mechanism to measure the curve of stroke-time, the distribution of the gap length of current zero zone under the fault current, pre-zero current drop rate, and commutation input instant was obtained. Moreover, based on the drift diffusion equation, Maxwell-Stefan equation and Poisson equation, the post-arc sheath development model was established to obtain the maximum electric field intensity under the influence of electromagnetic and electromechanical parameters. For evaluating the post-arc dielectric recovery strength with different commutation input time, pre-zero current drop rate, transient voltage rise rate, and contact diameter, the maximum cathode electric field intensity and critical electric field strength under the influence of zero zone metal vapor pressure and short-circuit breaking current were compared. Furthermore, the limit values of the pre-zero current drop rate and commutation input time, the minimum safety gap and the breaking current limit was obtained. Moreover, a solution for the design of the structural parameters and commutation parameter groups of the DC vacuum circuit breaker that meet the reliable breaking requirements can be provided.