The influence of dielectric dissipation factor on transformer Frequency Response Analysis

Frequency Response Analysis (FRA) is regarded as a robust technique to recognize transformer winding deformation. It has been implemented and used since the last decade. However, its interpretation and measurement sensitivity are still under development. Recent studies reveal that apart from winding deformation, FRA data can also be influenced by moisture variation in transformer paper insulation. Technically speaking, moisture variation will certainly influence the Dielectric Dissipation Factor (DDF) in transformer. Therefore, it is of interest to investigate the correlation between DDF value and FRA spectrum. A model transformer was fabricated for this study and the experiment was concentrated on the temperature changes and paper moisture variation and eventually DDF alteration on the FRA spectrum deviation. DDF was measured for the “wet” and “dry” model transformer at different temperatures. In parallel, the FRA spectrum was also recorded. The correlation between the transformer DDF value and FRA spectrum is highlighted and discussed.