Large power transformers are indispensable core hub equipment in the power system, mainly used for long-distance and efficient transmission and hierarchical distribution of electrical energy. They are typically classified according to industry standards as transformers with a rated capacity ranging from 8000 to 63000 KVA and a voltage level of 110 kV or above. Some special types of products can have a capacity exceeding 63000 KVA and a voltage level up to 500 kV or above. They are widely used throughout the entire chain of power production, transmission, and distribution. The stability of their performance directly determines the safety and efficiency of the entire power system. As a static electromagnetic induction device, it relies on the principle of electromagnetic induction to convert the electrical energy of one voltage level into the same-frequency electrical energy of another voltage level. It can both increase the voltage of the medium and low voltage electricity generated by power plants to high voltage for long-distance low-loss transmission, and reduce the voltage of high voltage electricity to medium and low voltage to meet the electricity demands of industrial production and daily life. It is the key bridge connecting the power generation end, the transmission network, and the end users. The core structure of a large power transformer consists of the iron core, windings, insulation system, cooling system and auxiliary protection devices. These components work together to ensure the stable operation of the equipment. The iron core, as the core of the magnetic circuit, is *ly made of high-performance oriented silicon steel sheets laminated together. Some new products use amorphous alloy materials, which can significantly reduce no-load losses. The windings, as the core of the circuit, achieve voltage conversion through different numbers of coils and are combined with high-quality insulation materials such as Nomex aramid paper to enhance the insulation strength and service life of the equipment. The cooling system is divided into oil-cooled and dry-cooled types. The oil-cooled type is widely used in large-scale scenarios due to its high heat dissipation efficiency, while the dry type is more suitable for areas with strict environmental protection and fire prevention requirements, and can be flexibly combined with Box Type Substation and High And Low Voltage Switchgear to form a complete power distribution system. The auxiliary protection devices include online oil chromatography monitoring and winding hot spot temperature monitoring, which can monitor the operating status of the equipment in real time and promptly warn of potential fault hazards. In terms of application scenarios, large power transformers are mainly concentrated in three core areas: Firstly, in the power generation plant's voltage boosting stage, the 10-20kV electrical energy from the generator is boosted to high voltage levels such as 500kV, and then connected to the national power transmission network for long-distance power transmission; Secondly, in the power grid hub substations, they undertake the conversion tasks of different voltage levels such as 500kV/220kV, 220kV/110kV, etc., to achieve interconnection and power allocation of regional power grids; Thirdly, for large industrial users, they provide core equipment for the 220kV substations built by large enterprises such as steel and chemical industries, meeting the centralized power supply requirements of large-power production equipment, and at the same time, they can collaborate with Combined Photovoltaic Substations and Electric Power Converters to adapt to the power grid connection requirements of new energy power stations. Compared with small transformers, large power transformers have the characteristics of large capacity, high voltage levels, complex structure, and high operation and maintenance requirements. They have more stringent requirements for manufacturing processes and material properties, and are one of the important indicators for measuring a country's power equipment manufacturing level.