Influence of the pyrolysis of benzotriazole passivator on the characteristics of dissolved gas in the insulating oil

Insulation failures of oil-immersed power transformer induced by sulfur corrosion can be controlled by adding the metal passivator into insulating oil. However, it has been reported that the addition of benzotriazole and its derivative passivators into insulating oil would cause abnormal generation of dissolved gases in the oil during the operation of oil-immersed transformer. Therefore, this paper investigated on the effect of passivator on the characteristics of dissolved gas in the oil under the action of thermal field. Benzotriazole (BTA) that widely used in the oil-immersed transformer was selected as the research object, the thermogravimetric analysis of BTA was conducted, and a series of accelerate thermal ageing experiments of oil-paper insulation with and without BTA were also conducted, the composition and content of dissolved gases in oil were measured and analyzed. The results show that BTA was pyrolyzed continuously as the temperature increase. The addition of BTA in oil accelerated the contents of H2, CO and CO2 and decelerated the content of hydrocarbon gases, which lead to abnormal generation of dissolved gases in oil. All of these may interfere the operation condition evaluation of oil-immersed transformer based on DGA technology.