oil‑immersed transformer -XinYa China manufacturer

Oil-Immersed Transformer: Technical Overview for Medium and High Voltage Power Systems

An oil-immersed transformer is a power transformer that uses mineral or synthetic insulating oil as both the dielectric medium and the main cooling agent. It is widely applied in utility substations, industrial power networks, renewable energy plants, outdoor distribution systems, and long-distance transmission projects. The insulating oil absorbs heat generated by core and winding losses and transfers it through the tank, radiators, or cooling circuits, helping maintain stable operating temperature under continuous load. The main structure includes a laminated steel core, copper or aluminum windings, a sealed or conservator-type tank, insulating oil, radiators or cooling fins, bushings, tap changer, pressure relief device, temperature indicators, and protective relays. The oil provides electrical insulation between live parts and improves heat dissipation efficiency. Modern oil-immersed transformers may adopt sealed tank designs, nitrogen cushion systems, or improved sealing structures to reduce oil oxidation and moisture ingress, which helps extend insulation life. Oil-immersed transformers are available in distribution and power transformer types, and can be designed for single-phase or three-phase systems. Common cooling methods include ONAN, ONAF, OFAF, and ODAF, selected according to rated capacity, load profile, and installation conditions. They are suitable for outdoor installation, high-load applications, and environments where efficient cooling and high dielectric strength are required. Because insulating oil is flammable, installation must comply with fire safety regulations, environmental protection requirements, and local utility standards. Key selection parameters include rated power, primary and secondary voltage, frequency, impedance, vector group, insulation level, temperature rise, no-load loss, load loss, short-circuit withstand capability, and ambient operating conditions. Routine maintenance should cover oil quality testing, dissolved gas analysis, insulation resistance measurement, cooling system inspection, leakage check, tap changer operation, and protective device verification. When correctly specified, installed, and maintained, an oil-immersed transformer provides reliable and efficient voltage transformation for medium and high voltage power distribution.

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