Determination of Characteristic Gases Diffusion Coefficients in Transformer Oil

Due to various reasons, large power transformers will inevitably produce bubble impurities with characteristic gases such as hydrogen, carbon monoxide, carbon dioxide, methane, ethane, ethylene, and acetylene as the main components. The content of characteristic gases at different locations provides important information for the operating status of the transformer. In order to simulate the transport of characteristic gases, it is necessary to obtain their diffusion coefficients in transformer oil. In this paper, the basic principle of the bubble dissolution method was used to build an experimental platform to efficiently determine the diffusion coefficients of hydrogen, ethane and ethylene in transformer oil at $25^{\circ}\mathrm{C}$., the measured values are $1.4\times 10^{-5}\text{cm}^{2}/\mathrm{s}$ for H2, $1.6\times 10^{-6}\text{cm}^{2}/\mathrm{s}$ for $\mathrm{C}_{2}\mathrm{H}_{6}$, and $1.1\times 10^{-6}$ cm ${}^{2}/\mathrm{s}$ for $\mathrm{C}_{2}\mathrm{H}_{4}$, with transformer oil degassed at 2 Pa for 20 min. It was found that inadequate degassing led to notably underestimated diffusion coefficients.