Transformer is mainly composed of iron core and winding, in addition, there are oil tank, moisture absorbent, radiator, explosion proof pipe, insulation sleeve and so on.(1) iron core: the main function is to form transformer magnetic circuit. It consists of coated silicon steel sheets stacked and fixed by clamping iron and perforated nails. Insulation bushing is used for iron core clamping bolts to insulate the iron core and reduce eddy current loss.(2) high and low voltage winding (coil) : it is the main electrical part of the transformer and the circuit part of the transformer to establish the magnetic field and transmit electrical energy. Low-voltage windings are mostly made of drum type, and high-voltage windings are made of drum type or pie type according to different capacities, which are jointly set in the core of the transformer. The low-voltage winding is placed in the inner layer, and the high-voltage winding is arranged in the outer layer of the low-voltage winding.(3) oil tank: transformer shell, welded steel plate. The low-pressure hot oil pipe is welded on the oil tank to form an up and down convection channel, increasing the heat dissipation area and enhancing the heat dissipation effect.(4) oil pillow: it is an oil filling and storage device in the operation of transformer. It is one tenth of the volume of the tank. The oil level indicator (oil level meter) on the side of the oil pillow is used to monitor the oil color, oil temperature and oil level during operation.(5) hygroscopic device: in the internal storage of desiccant, absorb moisture and impurities in the air, (6) voltage tap switch: also known as voltage regulation switch, when the power supply voltage changes, tap switch tap position can be adjusted, so that the receiving end remains unchanged, in order to maintain the insulation performance of insulation oil in the transformer.(7) radiator: there is a temperature difference between the oil temperature on the transformer and the oil temperature when it is low. The oil cycle is formed through the radiator to achieve the oil cooling effect. (8) high and low voltage insulation sleeve (porcelain sleeve).It is the insulation device that leads the high and low voltage winding of transformer to the outside of oil tank. It acts as a fixed lead and insulates the ground.