Oil power transformers are the main device that ensures the reliability of power distribution in the electric power network. It is the only device for connecting electric power rings of any voltage. Long-term reliable operation of oil power transformers has a direct impact on the power system and can sometimes lead to accidents. The technical condition of oil power transformers depends on the technical parameters of their main components. In this paper, the results obtained in the oil power transformer tank under operating conditions, the generation theory and the simulation model are analyzed. As a result, an express evaluation of the technical condition of oil power transformers was carried out.