Application of dielectric response for oil-immersed transformer

Reliability of large oil-immersed power transformers is attracting more and more attention by the power system, and a lot of new test methods are being under research. In this paper, the dielectric response for oil-immersed transformer insulation condition and ageing diagnosis is introduced; a 220 kV transformer was measured utilizing frequency domain spectroscopy in China. The tan delta-f curves of the transformer insulation system before and after maintenance were obtained and compared, respectively. The results showed that the dielectric response methods can reflect the internal transformer insulation, estimate moisture content in solid insulation, and provide reference information for the insulation diagnosis. Dielectric response is a non-destructive testing method that can be used as a supplementary technique for the existing diagnosis methods and has good application prospects.