Macroscopic broadband loss characteristics of power transformer winding extracted by Vector Fitting Method

In order to perfect the simulation of fast and very fast transient in power transformer and describe the impact of the broadband losses in power transformers accurately, this paper carried out the research of broadband losses characteristics in power transformer windings. Network analyzer Agilent 4395A was selected to measure the voltage transfer functions of testing transformer. Based on the measured curves, a targeted initial pole selecting method was proposed and Vector Fitting Method (VFM) was adopted to extract poles from measured transfer functions. The fitting formula of damping losses was determined by theoretical analysis of transformer circuit model. It was proved that the relationship of attenuation factor versus angle frequency extracted by VFM is quite accordant to the theoretical one deduced from circuit model.