As a traditional and classic device in the field of power transmission, the oil-immersed transformer occupies an important position in the power system with its mature technology and excellent performance. It takes insulating oil as the core medium, undertaking two key functions of cooling and insulation simultaneously. Insulating oil has excellent electrical insulation performance, which can effectively isolate the charged components inside the transformer, preventing electric leakage and short circuits. Meanwhile, through natural convection or forced circulation, it rapidly transfers the heat generated during the operation of the transformer, ensuring that the equipment always operates within a safe temperature range, greatly enhancing the operation stability and reliability of the transformer.​

In terms of structural design, the oil-immersed transformer is mainly composed of components such as the iron core, windings, oil tank, and insulating bushings. The iron core is made by laminating high-quality silicon steel sheets. Through a reasonable magnetic circuit design, it effectively reduces hysteresis and eddy current losses and improves the transmission efficiency of magnetic flux. The windings are made of high-purity copper or aluminum materials. After precise winding and insulation treatment, they have good electrical conductivity and mechanical strength, capable of withstanding the impact of high voltage and large current. The oil tank, as the outer shell of the transformer, is usually welded from high-quality steel plates, not only providing mechanical protection for internal components but also serving as a container for insulating oil. The surface of the oil tank is designed with radiating fins or radiators to further enhance the heat dissipation effect. The insulating bushings are used to lead out the high and low voltage windings inside the transformer, ensuring the insulation performance between the charged parts and the grounded parts. At the same time, they have good mechanical strength and thermal stability, ensuring reliable power transmission.​

In terms of performance, the oil-immersed transformer demonstrates significant advantages. Its capacity range is extensive, ranging from tens of kilovolt-amperes for small-sized ones to hundreds of megavolt-amperes for large-sized ones, capable of meeting the needs of power systems of different scales. It has low losses. Under the optimized design of the iron core and windings and the efficient cooling effect of insulating oil, both no-load losses and load losses are controlled at a low level, effectively reducing operating costs. In addition, this transformer has excellent overload capacity and can operate beyond the rated load for a short time, calmly coping with peak power consumption periods. Moreover, it has a long service life. High-quality materials, exquisite manufacturing processes, combined with the regular maintenance and replacement of insulating oil, enable the transformer to operate stably for decades.​

The application scenarios of oil-immersed transformers are very extensive. In large power stations and substations, it serves as a key device for power transmission and distribution, enabling efficient conversion and long-distance transmission of high-voltage electrical energy. In industrial plants, it provides stable and reliable power support for various large mechanical equipment and production lines, ensuring the continuous operation of industrial production. In urban power grids, it can be used for regional power distribution and capacity expansion to meet the electricity needs of residential life and commercial use. At the same time, in some places with high requirements for heat dissipation conditions and sufficient installation space, the oil-immersed transformer becomes the preferred power equipment due to its excellent heat dissipation performance and large-capacity advantages.​