Analysis of Lightning Surge on Transmission Line by New Numerical Electromagnetic Field Computation Method

虽然在电磁场数值计算方法中只处理了线性现象，但在本研究中，我们研究了如何处理放电现象，并在模拟器中增加了模拟非线性现象的功能。由于阻抗受非线性现象的影响，每隔一段时间都需要改变一个系统方程，存在计算时间大大增加的问题。我们注意到放电和避雷器被限制为传输线的一部分，并使用了自动设置电流变量数量顺序的算法，使其在创建系统方程时成为最小变化量。当传输线中存在非线性因素时，该算法使其计算时间增加10%左右，使在允许的计算时间内模拟雷击浪涌成为可能。雷电是一种非线性现象，它包含了从飘带到引线再到回程的复杂放电现象。在雷击浪涌分析中，如何建立模型是很重要的。我们研究了两种模型，第一种是电感元件模型，第二种是被空间边缘包围的等离子体核模型。后一模型在电磁场分析方法中易于编程，并明确了雷电通道的浪涌阻抗约为500欧姆，略高于电路模拟器中使用的传统雷电通道阻抗。研究了在给定前、尾时间下用双指数函数表示的脉冲电压参数的两种计算方法。第一种方法基于牛顿法，在前尾时间较宽的范围内，多次迭代具有较好的收敛性。第二种方法采用加速因子来减小迭代过程中时间参数的差异。这两种方法都可以在一毫秒内确定一个双指数函数。然而，短尾脉冲比标准雷电脉冲需要更多的迭代次数

Although only the linear phenomenon had been treated in the numerical electromagnetic field calculation method, we studied how to treat an electric discharge phenomenon and added the function to simulate nonlinear phenomenon to the simulator in this research. Since the impedance changes every moment by the nonlinear phenomenon, a system equation will need be changed for every simulation time step and there is a problem which the computation time increases greatly. We noted that electric discharge and lightning arrestor are limited to be a part of transmission line, and used the algorithm which sets the number of current variables in order automatically so that it becomes the minimum change at the time of creation of a system equation. Even when the nonlinear element existed in the transmission line, it held down to the increase in about 10% of calculation time by this algorithm, and it becomes possible to simulate lightning surge within allowable calculation time.Lightning which compri … More ses electric discharge phenomena complicated from streamers to leaders and the return stroke is also a nonlinear phenomenon. It is important how a model is created in lightning surge analysis. We examined two kinds of models, the first is made by the inductive element and the second is a plasma core surrounded by space *rges. The later model could be easily programmed in the electromagnetic field analysis method, and also clarified that tne surge impedance of lightning channel becomes about five hundreds ohm and a little higher than the conventional lightning channel impedance used in circuit simulator.We have studied two methods to compute parameters for the impulse voltage expressed by the double exponential functions under given front time and tail time. The first method is based on the Newton method and shows good convergence in several iterations over wide ratio of front time and tail time. The second method uses an acceleration factor to decrease the differences of time parameters which are given by the iteration process. We can determine a double exponential function under a millisecond by both methods. However, a short tail impulse needs more number of iterations than standard lightning impulse Less