传输线残余电荷放电响应模型的研究

残余电荷放电机制研究对开关操作中快速暂态过电压和电磁干扰研究有着重要意义。基于传输线电荷密度与电压之间的关系,建立了以传输线电荷密度和沿线电流为变量的新传输线模型;结合传输线终端条件,给出了端接负载时域有限差分公式,对该差分公式进行修改获得了终端开路和短路时的差分公式。运用时域有限差分法和无损传输线理论,验证了新传输线模型的正确性,比较了新模型与传统模型在分析残余电荷放电时电压响应中的各自特点。从分析结果发现,无论空间和时间离散步长是否满足Courant条件的等式关系,残余电荷释放产生的响应均发生了振荡现象。对比电荷均匀分布和不均分布传输线电压响应可以看出:电荷不均匀分布对电压幅值和传输时延有很大的影响。

Research on a New Model for Analyzing Response of Trapped Charge on Line

It is significant for the research on very fast transient overvoltage(VFTO) during circuit breaker switching and electromagnetic interference(EMI) to research the discharging mechanism of trapped charge in transmission line.Based on the relation between the charge density and voltage of transmission line,a new transmission line model,in which the charge density of transmission line and the current along the line are taken as variables,is built to analyze discharging response of trapped charge.Combining with the voltage-current relations at both ends of transmission line,finite-element difference formulae in time-domain are given when load is connected to the ends,and after slightly modifying the finite-difference formulae under open-circuit and short-circuit of the ends are obtained.Utilizing finite difference method in time-domain and the theory of lossless transmission line,the proposed transmission line model is verified,and respective features of the proposed transmission line model and traditional transmission line model,which are applied in the analysis on the voltage response during discharge of trapped charge,are compared.It is discovered from simulation results that whether the discrete time and space step-length could meet equal Courant conditions or not,there is oscillation in the voltage response caused by the discharge of trapped charge.Comparing the discharging voltage response of trapped charge of non-uniform distribution with that of uniform distribution,it can be seen that there is evident influence of non-uniform charge distribution on amplitude of voltage response and transmission delay.