The paper considers the development history of criteria for assessing the technical condition of current transformers in Russia based on the results of dissolved gas analysis. Through dispersion analysis, the factors (design features, service life) having the greatest impact on gas generation in current transformer oil were identified. A system of criteria for evaluating dissolved gas in oil of 110-220 kV current transformers is given. The system is regulated by the new PJSC "Rosseti" standard - STO 34.01-23-003-2019 "Methodological guidelines for the technical diagnosis of developing defects in oil-filled high-voltage electrical equipment based on the results of dissolved gas analysis". The criteria are calculated based on a representative array of dissolved gas analyzes accumulated in the database of an expert diagnostic system for 25 years of its operation. Algorithms for determining the frequency of dissolved gas analysis and necessary operations for maintenance or repairs of 110-220 kV oil-filled current transformers are presented.