Analysis of resonance in transformer windings under very fast transient overvoltages

To study the resonance in transformer windings, under very fast transient overvoltages (VFTOs) generated by switching operations in gas insulated substation (GIS), a single input and multiple output circuit model is presented in this paper which is based on multi-conductor transmission line (MTL) model of transformer windings. The procedure to determine the transfer function is deduced. The resonant frequencies and the location of resonance are determined by the analysis of amplitude frequency response characteristics. For validation, the calculated results are compared with the measurements on a transformer winding model and the result is satisfactory.