Detection and Quantitative Diagnosis of Axial Displacement of Transformer Winding by Frequency Response Analysis

Transfer functions of a transformer whose winding is axially displaced are measured in several connection schemes of frequency response analysis (FRA), and the sensitivities of the measured transfer functions in these connection schemes to the axial displacement are evaluated. For the objective evaluation, some numerical indices are employed, and it is found that the inductive inter-winding measurement is the most sensitive to the axial displacement. Furthermore, a simple circuit model is proposed to reproduce the measured transfer functions. All the parameters of the proposed circuit model can be determined from the measured transfer functions in FRA. The proposed model can also reproduce the measured transfer functions with the axial displacement by varying one parameter. The variation of the parameter in reproducing the transfer function with the axial displacement show good linear relation to the amount of the axial displacement. This indicates the possibility of a quantitative diagnosis of the axial displacement by FRA.