I.Oil-immersed transformer components: iron core, winding, tank, transformer oil, casing pipe, radiator, oil conservator (small power distribution transformer may not have this.)
II.Characteristics of Oil-immersed Transformer
Advantages:
1. The transformer oil has good insulation performance and thermal conductivity, while the transformer oil is cheap.
2. Be able to solve the problems of high-capacity heat dissipation of the transformer and the insulation of high voltage.

Shortcomings:
1. Transformer oil is flammable, when it encountered flame, it may burn and explode.
2. Transformer oil is harmful to human body.
3. Transformer oil should be regularly checked.
4. The sealing performance for oil-immersed transformer is bad and is easy to get aging. Its oil leakage is serious in the running place, affecting the safe operation of equipment and has influence on the environment simultaneously.
5. The insulation class for the oil-immersed transformer is low, it’s designed and manufactured according to A-class insulation.

III.Classification of Oil-immersed Transformer
Divided into iron core type transformer and iron shell type transformer. For example, if the winding is wrapped in the outside of the iron core; then the transformer is called as iron core type transformer; if the iron core is wrapped in the outside of the winding, then the transformer is called as iron shell type transformer. But the structure between both is slightly different; there is no essential difference on principle. Power transformers are all of iron core type.
Transformer is mainly made up of the iron core, winding, fuel tank, oil conservator, insulation casing pipe, tap switch and gas relay and other components.