Frequency Characteristics of Transformer Windings

Transformers are subjected to voltages and currents of various waveforms while in service or during insulation tests. They could be system voltages, ferroresonance, and harmonics at low frequencies, lightning or switching impulses at high frequencies, and corona/partial discharges at ultra-high frequencies (a brief explanation is given at the end of the chapter). It is of great importance to understand the frequency characteristics of transformer windings, so that technical problems such as impulse distribution, resonance, and partial discharge attenuation can be more readily solved. The frequency characteristics of a transformer winding depend on its layout, core structure, and insulation materials.