基于二端口散射参数的CVT宽频暂态模型

Broadband Transient Model of CVT Based on Two-port Scattering Parameters

摘要:

电容式电压互感器(CVT)因为绝缘强度高,测量工频准确的优点,在电力系统中的运用十分广泛。由于雷电过电压、操作过电压等暂态信号时常在电力系统内发生，而CVT只能准确传递工频信号，对于非工频信号将产生不同程度的失真，因此有必要对CVT进行宽频的建模。本文利用黑盒模型基于CVT的端口参数进行宽频建模，通过网络分析仪测量其散射参数并利用矢量匹配法和福斯特等值电路理论转化为π型等值电路。最后通过雷电冲击实验得到的CVT高压输入波形，利用贝杰龙法和支路电流矩阵法计算成功得到与测量结果近似相同的二次侧输出波形，验证了模型的正确性。

Abstract:

Due to the advantages of high insulation strength and accurate power frequency measurement of capacitor voltage transformer (CVT), it is widely used in power system. As lightning overvoltage, switching overvoltage and other transient signals often occur in power system, CVT can only accurately transmit power frequency signals, and non-power frequency signals will produce varying degrees of distortion, so it is necessary to model CVT in broadband transient. A black box model based on port parameters of CVT is used to build the model, then with network analyzer measuring the scattering parameters of the CVT, and vector fitting method and Forster equivalent circuit theory are used to transform the model to π type of equivalent circuit. Finally, the high-voltage lightning input waveform of CVT is obtained by lightning impulse test, and the output waveform of secondary side is obtained by using Bergeron model and computing branch current equation, which is similar to the measurement results, so the correctness of the proposed model is verified.