Ability of transfer function method to diagnose axial displacement of transformer windings

Transient currents can cause the mechanical displacement of transformer windings. The transfer function method is presented as a tool to detect this displacement. In order to be able to evaluate the measurements, the correlation between the characteristics of transfer functions and possible damages must be known. Axial displacement of transformer windings has been studied in this research. As test object a transformer with a primary winding of 31 double inverted disk (approx. 1.3 MVA, 10 kV) and a secondary winding with four layer concentric winding was used. A detailed mathematical model was developed for the test object and a comparison was carried out between measured and calculated results. To compare the sensitivity of transfer functions, five different transfer functions with different terminal conditions are simulated. It is shown that the detailed model can present the behaviour of the transformer winding in case of sound and displaced windings.