Investigation on Formation Mechanisms of Carbon Oxides During Thermal Aging of Cellulosic Insulating Paper

The carbon oxides (CO
₂
and CO) in the insulating oil of power transformers come from the thermal aging of cellulosic insulating paper; the CO
₂
/CO ratio can reflect the aging state of cellulosic insulating paper. At present, the formation mechanisms of CO
₂
and CO in oil-immersed power transformers are still unclear. In this article, the ReaxFF reaction force field is used to simulate the thermal aging process of cellulosic insulating paper, and the main reaction pathways of CO
₂
and CO molecules formed by cellulose pyrolysis are obtained. The study finds that the amount of CO
₂
and CO generated is related to temperature. When the pyrolysis temperature continues to rise, the amount of CO
₂
generated shows a downward trend, while the amount of CO generated continues to increase, and the CO
₂
/CO ratio continues to decrease. The simulation results are consistent with the previous experimental results. Through pathway tracking, it is found that the CO
₂
and CO molecules are mainly derived from certain specific atoms of cellulose molecules. The COSMO-RS module is used to analyze the change trend of the solubility of CO
₂
and CO in insulating oil with temperature. The results show that the solubility of CO
₂
and CO decreases with the increase of insulating oil temperature, which provides theoretical support for accurate application of carbon oxides aging evaluation index at different temperatures.