Influence of moisture content variation on Frequency Response Analysis of transformer winding

Frequency Response Analysis (FRA) has been used as a diagnostic method for transformers since the last decade and is emerging as a popular technique. Recent studies on this technique reveal that FRA data are not only influenced by transformer winding deformation but could be also affected by transformer insulation parameters. Hence, this study has concentrated on the influence of moisture content variation on the winding frequency response spectrum. To this end, transformer water dynamic is briefly discussed. A model transformer is used as the test object. Frequency response spectra of `wet´ and `dry´ conditions of the test object are examined for different moisture contents and different temperatures. The results of both examinations are then compared, and finally the common trend in FRA spectrum deviation under such circumstances is explored.