Modeling of potential transformers for the very fast transient simulation based on wideband scattering parameter measurements

The wide frequency circuit models of instrument transformers is indispensable for an accurate simulation of the electromagnetic interference from primary system to the secondary system caused by very fast transients through potential and current transformer (PT/CT) in gas insulated substations. A systematic methodology is described for establishing the wide frequency circuit model of PTs based on wideband scattering parameter measurements in this paper. The new passive circuit model is only composed of R, L and C elements and ideal transformers, and the parameters of the elements can be easily calculated by the poles and residues of the PT short circuit admittance function. The circuit model is simple and robust. The simulation and measured results are presented, confirming the validity of the model and the systematic methodology proposed in this paper.