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.