Experimental investigation of localized axial winding displacement in a high frequency range for power transformers

Sweep frequency response analysis (SFRA) is an efficient diagnostic technique for detecting mechanical and electrical faults of transformer windings. Recent research effort has been devoted to using the SFRA method for characterization of transformer winding faults in high frequency range (>1 MHz) by modeling of transformers. This paper presents an experimental investigation of localized axial winding displacement over the frequency range from 20 Hz to 5 MHz. The corresponding experiment setup is described, and the obtained spectra are analyzed by using visual inspection as well as quantitative comparison. It indicates that the variation of the frequency response beyond 1 MHz due to the localized axial winding displacement cannot exclude the influence of the change of winding structure. The results also verify that the frequency sub-bands of a FRA spectrum supporting FRA interpretation are specific to the design of transformer windings.