一种基于散射参数的电压互感器二端口高频电路模型

A High Frequency Two-port Circuit Model for Potential Transformer Based on the Scattering Parameter

为了计算气体绝缘变电站(GIS)内由特快速暂态过电压(VFTO)对二次设备产生的传导干扰,必须建立电压互感器和电流互感器(PT/CT)的高频模型。为此,该文提出了基于散射参数的互感器二端口高频电路模型建立的新方法。该方法首先将测量得到的互感器的散射参数转化为导纳参数并构建互感器的π形等值电路;然后,应用矢量匹配法对π形等值电路的导纳参数进行有理函数逼近获得它们部分分式和形式的频域表达式;最后采用电路综合方法构建出导纳元件的等值电路。时域仿真和实测结果的比较验证了该方法的可行性和有效性。该方法具有简单、有效和通用的特点,克服了以前建模方法的不足,所建立的模型可以使GIS内的传导干扰计算更为准确。

For accurate simulation of voltage stress on secondary circuits caused by very fast transient over-voltage in gas insulated substation （GIS）, a sophisticated modeling of potential and current transformers （PT/CT） is of vital importance. A new method is proposed to setup high frequency two-port circuit model of PT based on scattering parameters. First, the scattering parameters of PT are transformed in to Y-parameters and equivalent ＂π＂ circuit model could be established. Second, vector fitting method is used to approximate admittances of equivalent ＂π＂ circuit model by rational functions. At last, a circuit synthesis method for rational functions is applied to build circuit model. The simulation and measurement results are presented, which confirmed validity of the proposed model. The proposed method is effective and general, and overcomes the limitation of former methods. The model setup by this method can make simulation more accurate of conductive coupling through PT/CT in GIS.