The criteria of dissolved gas analysis in natural ester fluid

In this paper, dissolved gasses of natural ester fluid were analyzed to suggest DGA criteria for transformer filled with natural ester fluid. Samples of mineral oil and natural ester fluid made to correspond to the ratios of the iron core, winding, insulating materials and insulating oil in a transformer were deteriorated for 1,600 hours in a 150°C thermostat and samples were collected every two hundred hours to analyze changes in the contents of dissolved gases. As the results, H₂ and C₂H₂ gases were hardly detected and C₂H₆ gas detected from natural ester fluid was two times larger in quantity than mineral oil. CH₄ gas detected from natural ester fluid was 1/4 in quantity of the gas detected from mineral oil. Amount of other dissolved gasses were similar to each other. Based on these results, DGA criteria for transformers applied with natural ester fluid were presented.