Effects of Metal Passivator Degradation on the Dissolved Gases Characteristics of Oil in Oil-immersed Transformers

Sulfur corrosion has been proven to significantly decrease the insulation performance of oil-immersed transformer and the addition of benzotriazole passivator (BTA) to insulating oil has been widely used to control the sulfur corrosion. However, the relevant studies indicate that the addition of metal passivator to oil can cause abnormal generation of dissolved gases in oil. Thus, this study further explores the effects of metal passivator degradation on the dissolved gas characteristics of oil in oil-immersed transformers. Several accelerated aging experiments on oil-paper insulations with and without BTA are conducted. The results indicate that the addition of BTA lead to the generation of abnormal dissolved gases in the oil along with an increase of stray gases, especially the increase of H2, CO and CO2. Moreover, an abnormal production of the total hydrocarbon fraction is found, which may interfere with the DGA results. Finally, the degradation of BTA related to abnormal production of stray gases in the insulating oil was preliminarily analyzed and discussed.