Frequency response analysis is always considered to be a method with most prospect to diagnose power transformer winding deformation fault, however, most existing frequency response analysis just uses the amplitude information of frequency response, and ignores the characteristic of phase variation, the sensitivity of diagnosing fault is not high enough. Thus, this paper proposes a new polar image method, the frequency response is used to construct polar image, which assists to diagnose winding deformation fault. A case study of winding equivalent electrical model is carried out, the result demonstrates that when the normal frequency response analysis can"t reflect the winding minor radial deformation fault, the method proposed in this paper may detect winding fault more effectively, the polar image method has higher sensitivity of diagnosis.
