Study On Overvoltages Of The Transformer Windings Under VFTO Based On Scattering Parameters

Supported by Hebei Natural Science Foundation under grant No.503624, The high frequency circuit model of the transformer windings in GIS is researched in this paper. The main contributions are as follows: 1 The scattering parameters of the multiconductor transmission lines are derived for the calculation of the voltage distribution of the transformer windings under VFTO. 2 The transfer functions of the transformer windings are derived, which are expressed in S parameters of the two-ports and multi-ports, respectively. And the transfer functions are also approximated by the Vector Fitting. 3 The reduced-order models of the transfer functions are obtained based on Pade approximation. 4 The high frequency circuit model of the transformer windings is established by the network synthesis. And the calculated result is compared with the measured, it is shown that the circuit is simple and robust.