Abstract: Oil-immersed transformers are key equipment in the power system, responsible for the transmission and distribution of electrical energy. They contain a large amount of insulating oil and withstand extremely high voltage and current. The main hidden dangers include insulation aging, overheating, seal failure, in-ternal discharge, etc., which may lead to catastrophic accidents such as transformer explosion, fire, and oil spraying. Dissolved Gas Analysis (DGA) of transformer oil is the core technology for diagnosing latent hidden dangers within oil-filled power equipment. From DGA to achieving precise hidden danger locali-zation, a complete set of hidden danger handling methods is required, and its practical application signifi-cance far exceeds simple laboratory testing. This paper analyzes a transformer hidden danger handling case where the transformer was returned to the factory for hood lifting maintenance due to excessive total hydrocarbons in dissolved gases in the oil. It summarizes a set of transformer total hydrocarbon excess hidden danger handling methods based on DGA combined with multiple diagnostic methods. The entire hidden danger handling process combines multiple diagnostic methods to achieve short-term targeted tracking of the hidden transformer. During the tracking process, the hidden danger handling strategy is optimized, and scheduled maintenance tasks are used to replace emergency repair work, completing the transition from "regular inspection" to "condition-based inspection". The diagnostic methods mainly in-volve DGA of transformer oil (characteristic gas method, three-ratio method, gas production rate analysis), infrared thermography temperature measurement and oil leakage inspection, multi-dimensional trans-former integrated detection and diagnosis system (TES-600), and diagnostic electrical testing. Finally, the hidden danger location is determined through a multi-dimensional evidence chain: the transformer''s in-ternal core has an overheating fault, and a return to the factory for hood lifting maintenance plan is pro-posed.