415 / 2022-03-15 21:10:27

Diffusion Coefficients of Characteristic Gases in Transformer Oil Measured by Bubble Dissolution Method

apparent diffusion coefficient,dissolved gas-in-oil analysis,bubble dissolution method

Purpose/Aim

Characteristic gas concentration is an important indicator of the safe operation of oil-immersed transformers. In order to analyze the transport and distribution of the characteristic gases, it is necessary to obtain the diffusion coefficient of characteristic gases in the insulating oil.

Experimental/Modeling methods

The diffusion coefficient was estimated from experimental observation of bubble dissolution process in oil on a specially designed platform, and Ansys Fluent fluid simulation was adopted to iteratively correct the effect of convection caused by the dissolution process. Electrodes were also added to study the effect of electric field on the diffusion coefficient. In addition, a thermostat was used to control the temperature of the insulating oil, with an adjustable range of 10 to 90°C. The experimental setup allows the study of the diffusion coefficient of gases in insulating oil at different temperatures and electric field strengths.

Results/discussion

The diffusion coefficients of the leading diagnostic gases (hydrogen, methane, ethane, ethylene, acetylene, carbon monoxide and carbon dioxide) in transformer oil were determined. Some anomalies in the observed results may have resulted from the gas purity in the bubbles during bubble formation and the liquid’s residual dissolved air concentrations.

Conclusions

Data were obtained on the diffusion coefficients of characteristic gases in transformer oil under different temperature and electric field conditions to better understand the operating behaviors of the transformer and the causes of faults.