The difference between oil transformer and dry transformer

Cooling method and insulation medium
Dry Transformation: relying on natural air convection or forced air cooling for heat dissipation, the winding and iron core are encapsulated with solid insulation materials such as epoxy resin, without the need for oil media.
Oil Transformer: Using transformer oil as a cooling and insulation medium, the oil circulates to remove heat and prevent internal components from oxidizing, resulting in higher heat dissipation efficiency.

2. Appearance and structure
Dry transformation: It is usually an open or cast structure, where the iron core and coil can be directly seen, and the leads are often made of silicone rubber sleeves.
Oil immersion: completely enclosed within the casing, with only the radiator and porcelain sleeve visible, and the internal coils submerged in oil.
3. Capacity and voltage level
Dry type transformer: commonly used for power distribution, with a capacity generally ≤ 1600KVA and a voltage ≤ 35KV, with a few reaching up to 35KV.
Oil transformer: covering the full capacity range, with higher voltage levels (including ultra-high voltage 1000KV), suitable for large-scale power systems.
4. Applicable places and safety
Dry transformation: Due to its oil-free and flammable nature, it is suitable for fire and explosion prevention places (such as high-rise buildings, subways, etc.) and can be directly installed in the distribution room.
Oil transformer: It is necessary to set up an accident oil tank to prevent leakage, which is mostly used in outdoor substations or industrial facilities. The maintenance cost is low but there is a risk of fire.
5. Performance and Economy
Overload capacity: Oil based transformers have better heat dissipation and significantly stronger overload capacity than dry based transformers.
Cost: Due to the complex insulation material process, the cost of dry transformation is usually higher than that of the same capacity oil transformation.
Summary: Choosing the type of transformer requires comprehensive consideration of the environment, load, safety, and budget. Dry transformers are suitable for places with limited space and high safety requirements, while oil transformers are more suitable for outdoor power systems with large capacity and high voltage.