Role of metal passivator on production of hydrogen gas in insulating oil and oil-impregnated insulation paper

Dissolved gas analysis is significant for the exact fault diagnosis of power transformers. This paper focuses on investigating the mechanism of hydrogen gas production in insulating oil and oil-impregnated insulation paper (OIIP) by a metal passivator named N-bis(2-Ethylhexyl)-aminomethyl-tolutriazole (TTAA). High-performance liquid and gas chromatography are used to quantitatively test the concentration of TTAA and dissolved gases in the oil, respectively. The molecular dynamics simulation is applied to analyze the mechanisms of gas production and adsorption of TTAA. The results indicate that TTAA could be easily pyrolyzed to form carbon and nitrogen free radicals, which induces oil decomposition to form more low-molecular-weight hydrocarbon gases and H2. The higher the TTAA concentration in oil, the more H2 is generated. Additionally, the H2 content decreases by about 80% in the OIIP compared with the insulating oil. In the OIIP, the residual content of TTAA decreases in the oil and increases in the paper after the thermal aging experiment as the mass of the pressboard increases. The simulation results indicate that the insulating pressboard could adsorb TTAA, slowing down the reaction between oil and TTAA, leading to the decreasing content of hydrogen. At 393 K, the adsorption energy reaches approximately − 60.0 kJ/mol, which is a stable physical adsorption. That is why the TTAA does not substantially affect gas quantity in the OIIP during transformer operation. This work contributes to the accurate diagnosis and safe operation of power transformers.