Determination and Understanding the Impedance Behaviour of Power Transformers

The impedance enables a holistic and frequency-dependent characterization of power transformers and represents fundamental physical properties. So far, there is no the standard for measuring this quantity, which often leads to confusion regarding the measurement and interpretation of impedance behaviour. In the first part of this article, the aim is to clarify the differences between standard FRA and an actual measurement of the transformer imped-ance. The second part is focusing on the mutual influence of windings and core on the impedance of a 20 MVA single-phase R&D transformer.