Broadband frequency response analysis of transformer windings

In this paper, an analysis method of natural frequencies and corresponding oscillation modes for power transformer windings is proposed. Firstly, the natural frequencies and their response factors are calculated based on the structure and parameters of the transformer windings, then it is pointed out that not all of the input voltage at natural frequencies can cause significant oscillation in the windings. Secondly, the patterns of the oscillation modes corresponding to the natural frequencies are illustrated, which show the different effects of the oscillation modes on the voltages at different nodes in the windings. These patterns could help the transformer designers to estimate the insulation endurance of transformer against transient voltages containing particular frequency components.