About the oil-immersed transformer

Structure of oil-immersed transformer

The oil-immersed transformer consists of magnetic core, winding and bushing. The magnetic core provides a path for the magnetic flow. The windings generate a magnetic field and consist of a conductor coil wound around the core and insulated with a cardboard barrier and screen. The thickness of winding insulation increases with the increase of voltage. The bushing connects the transformer windings to the substation. An oil-immersed transformer is characterized by an oil storage tank. It simplifies operation by monitoring the oil level in the tank and providing space for the thermal expansion of the oil.

 Characteristics of oil-immersed transformer

Oil-immersed transformer is a transformer whose heat dissipation medium is transformer oil. Oil-immersed transformers have been used in power transmission and distribution engineering for hundreds of years. Oil-immersed power transformer has become one of the most widely used electrical equipment in the world due to its advantages of simple structure, long history, abundant manufacturing and operation, and reliable operation. Oil - immersed transformers are mostly used in power system. As the name implies, dry transformer is a kind of transformer with air instead of transformer oil as the heat dissipation medium.

Why do transformers use oil?

Transformer oil is used as the cooling medium of oil-immersed transformer, and the heat generated during transformer operation is transmitted to the metal shell and emitted by the transformer oil. It has the advantages of fast heat dissipation, uniform conduction and recovery of oil insulation. However, the oil itself has the disadvantages of low heat resistance, inflammability and easy aging, so there are many specific requirements in the use of transformer oil as cooling medium.

For example, the building where the transformer is placed must meet the fire rating requirements specified in the building fire protection code; Measures must be taken to prevent the spread of fire caused by oil flow in case of fire; Fire extinguishing measures must be in place to extinguish oil fires; There must be oil storage pool facilities to prevent oil leakage pollution to the environment; Daily work should monitor the aging of insulating oil and regular oil regeneration work.

Moreover, the minimum net distance between the external profile of the oil-immersed transformer and the wall and door of the transformer room also has strict distance requirements. The various civil structures, fire barriers and storage tanks of oil-immersed substations are designed for the flammability and fluidity of oil. In addition, "when the substation is located in the building, the door should be a fire door." In this way, each substation design fire prevention construction investment is naturally much larger.

With the continuous development of science and technology and the progress of material science, there are a series of fully sealed s9-M, S10-M, S11-M and other fully sealed oil-immersed transformers. The corrugated oil tank is adopted, and the thermal expansion and contraction of transformer oil are adjusted by the elasticity of the corrugated sheet, which is isolated from the air and basically overcomes the problem of oil leakage.

Fully enclosed oil-immersed transformer without breathing apparatus solves the problem of oil oxidation caused by oil and air contact and prolongs the service life. It also has a small footprint, energy saving and leading performance technology. High quality high magnetic orientation cold rolled silicon steel sheet. Compared with S9 with the same capacity, no-load loss is reduced by 30%, no-load current is reduced by 40-70%, and noise is reduced by 5≤8 dB (A). However, because oil is still used as a cooling medium, the design must also comply with the relevant specifications of oil-immersed transformers.

Finally, oil-immersed transformer scrap, can be disassembled into raw material recycling.