A new on-line monitoring method of transformer winding axial displacement based on measurement of scattering parameters and decision tree

► Transformer winding axial displacement can be detected by comparison of S-parameters. ► The measured S-parameters are compared with the latest measurements (time-based). ► Two indices ( MAMD and MAPD) are defined from the magnitude and phase of S-parameters. ► The decision tree method has a good accuracy to determine the winding displacement. In this paper the scattering parameter of a simplified model of transformer has been measured in different axial displacement of the winding using a Network Analyzer. Two indices have been suggested to detect the axial displacement. The measurement results show the effectiveness of these indices. A new method of the detection of the axial displacement extent based on decision tree (DT) has been proposed, too. It has been shown that this method has a good accuracy to determine the displacement of the winding and its extent.