Temperature influence on FRA spectrum of oil-filled and oil-free single-phase transformer

A fast, non-destructive, and accurate technique has been introduced more than 30 years ago and industrialized since the last decade to recognize the transformer mechanical defect. This method called Frequency Response Analysis (FRA) and implemented as an off-line technique. Nowadays, transformer researchers as well as experts showing significant interest in real-time application of diagnosis methods such as Frequency Response Analysis (FRA), while accurate interpretation of FRA signature is still challenging. Recent studies reveal that apart from winding deformation, FRA data can also be influenced by temperature and moisture variation in transformer paper insulation. Hence, this study has specifically concentrated on the influence of temperature variation of the transformer winding on FRA spectrum. For this, a single phase model transformer is fabricated and taken as a test object. The test object temperature in the presence and absence of the oil, before and after dry-out process is changed widely from low to high temperatures and the frequency response traces of the windings are recorded. The results are discussed in detail and deviated anti-response and resonances are compared.