Oil immersed transformer takes oil as the main insulation method of transformer and relies on oil as cooling medium (self cooling). The wind is cold. Water is cold). Generally, the main transformer of boost station is oil-immersed, and the ratio of 20KV/500KV. Dry-type transformer relies on air convection for cooling. Small capacity transformer ratio 6000V/400V.

Dry type transformers refer to transformers which are not immersed in insulating oil and iron core. The cooling methods are divided into natural air cooling (AN) and forced air cooling (AF). In natural air cooling, the transformer can operate continuously for a long time at rated capacity. When forced air cooling, the output capacity of the transformer can be increased by 50%. Suitable for intermittent overload operation or emergency overload operation; overload should not be in a long-term continuous overload operation because of the large increase of load loss and impedance voltage in the non-economic operation state.

Dry-type transformer and oil-type transformer, in addition to the same working principle, the biggest difference is whether there is oil inside the transformer, but also there are many differences.

(1) in terms of appearance, the form of encapsulation is different.

Dry type transformer can directly see iron core and coil, while oil transformer can only see the shell of transformer.

(2) The lead forms are different. Silicone rubber bushing is mostly used in dry-type transformers, while porcelain bushing is mostly used in oil-type transformers.

(3) Different capacities and voltages, dry-type transformers are generally suitable for distribution, most of which are below 1600KVA, voltage is below 10KV, and some of them are below 35KV; while oil-type transformers can be from small to large to achieve full capacity, voltage level is also achieved all voltage; China is building UHV 1000. The KV test line must be oil transformer.

(4) Insulation and heat dissipation are different, dry-type transformers are generally insulated by resin, by natural air cooling, large capacity by the fan cooling, and oil-type transformers by insulation oil, insulation oil in the transformer's internal circulation will be generated by the coil of the tropical to the transformer's radiator (chip) for heat dissipation.

From the application point of view, dry-type transformers are mostly used in places where "fire prevention, explosion-proof" is needed, and they are easy to be used in large buildings and high-rise buildings. Oil-type transformers may be sprayed or leaked after "accident", resulting in fire, mostly used outdoors, and there are sites where "accident pools" are excavated. (5) Generally, dry-type transformers should operate at rated capacity, while oil-type transformers have better overload capacity.