Application of frequency domain spectroscopy to the insulation diagnosis of oil-immersed power transformer on site

In order to improve the reliability of large oil-immersed power transformers, the frequency domain spectroscopy for oil-immersed transformer insulation condition and aging diagnosis was introduced, a domestic 220 kV transformer was measured using FDS methods, and the tan δ-f curves of the transformer insulation system before and after maintenance were obtained and compared. The consistency of frequency domain spectroscopy and preventive test on measuring capacitance was verified by comparing the data acquired by both methods. The results show that the frequency domain spectroscopy can reflect the internal transformer insulation, estimate moisture content in solid insulation, and provide reference information for the insulation diagnosis. FDS is a non-destructive testing method that can be used as a supplementary technique for the existing diagnosis methods, having good application prospects.