Moisture estimation for oil‐immersed bushing based on FDS method: at a reference temperature

Oil-immersed bushing is one of the most important accessory equipment of a transformer, whose insulation status is crucial. Moisture is an important factor that affects the insulation status of oil-immersed bushing. It has a very important significance to estimate the moisture content of oil-immersed bushing accurately. Here, the 72.5 kV bushing samples with different moisture contents were made. Afterwards, the frequency domain dielectric spectrum (FDS) of samples were tested at 15°C. The Havriliak-Negami equation was modified based on the analysations of complex planes, then it was used to analyse the experimental results. Moreover, the characteristic parameters and method to estimate moisture content were obtained and testified. Finally, the field application of the proposed estimation method was also discussed. The results of the studies shown here indicate that the moisture content of oil-immersed bushing can be estimated based on the proposed method effectively; however, in order to estimate the moisture content of field oil-immersed bushing, the elimination of temperature effects should be considered.