The application of the transfer function is discussed at present as a method for on-site monitoring and diagnosis of power transformers with regard to mechanical damages of the winding. In order to be able to evaluate the measurements, the correlation between the characteristics of transfer functions and possible damages must be known. Radial deformation of transformer windings have been studied both experimentally and theoretically. The primary winding of the test transformer has 30 double disk coils (1.2 MVA, 10 kV) and the secondary is a one layer winding with 23 turns (1.2 MVA, 400 V). A detailed mathematical model was developed for the test object and a comparison between measured and calculated results was carried out. A numerical method for the calculation of inductances is suggested, which is independent of the shape of the windings’ turns. For the calculation of the earth capacitances a relationship is given. An independent simulation confirmed the
accuracy of this relationship by using finite elements method. It is shown that the developed model can represent the behavior of transformer windings in the frequency domain in case of sound and deformed conditions.
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