a feasible solution to distinguish the transformer winding deformation from insulation characteristic impacts on fra spectrum

frequency response analysis (fra) is popular technique which has been used since the last decade as a diagnostic method for transformers. however, accurate interpretation of fra measurements is still challenging. recent studies reveal that apart from winding deformation, fra data can also be influenced by moisture variation in transformer paper insulation. hence, a specific transformer’s model is fabricated for this study and the experiment was concentrated on the paper moisture variation and mechanical deformation influences on fra spectrum deviation. different physical changes to the test object are investigated and the results are discussed. at the end, the weakness of fra evaluation indicators to recognize winding deformation under different circumstances is highlighted and a feasible solution is recommended.