Differences between dry-type transformers and oil-immersed transformers (purchasing method included)

2022-12-31 12:10  |  By:  |  53click

Transformers are generally divided into two categories, dry-type transformers and oil-immersed transformers. A dry-type transformer is one in which the core and windings are not immersed in insulating oil. An oil-immersed transformer is a transformer in which the iron core and windings are immersed in insulating oil. The biggest difference between the two is the "oil type" and "dry type", that is to say, the cooling medium of the two is different. The former uses transformer oil as the cooling and insulating medium, and the latter uses air or other gases such as SF6 as the cooling medium. cooling medium. Below we introduce the difference between the two and how to make a choice when purchasing.



The price becomes more expensive than oil. For transformers with the same capacity, the purchase price of dry-type transformers is much higher than that of oil-type transformers. Dry-type transformer models generally start with SC (epoxy resin casting encapsulation), SCR (non-epoxy resin casting solid insulation encapsulation), SG (open type)

2.Different capacity and voltage

In terms of capacity: large capacity oil becomes more than dry.

Dry-type transformers are generally suitable for power distribution, with a capacity mostly below 1600KVA, a voltage below 10KV, and some with a voltage level of 35KV;

However, oil-type transformers can achieve full capacity from small to large, and the voltage level can also achieve all voltages; for example, the UHV 1000KV test line under construction must use oil-type transformers.

3.Places of use

dry change is required in complex buildings (basement, floor, roof, etc.) and crowded places. The oil substation is used in an independent substation.

During construction, dry substation and oil substation are selected according to the space. When the space is large, oil substation can be selected, and when the space is crowded, dry substation can be selected.


The regional climate is relatively humid and hot, and it is easy to use oil. If dry change is used, it must be equipped with forced air cooling equipment.

5.The appearance and packaging are different.

Dry-type transformers can directly see the iron core and coil, while oil-type transformers can only see the outer shell of the transformer;


The noise of dry-type transformers with the same voltage level and capacity is greater than that of oil-immersed transformers.

7.Lead form is different

Most dry-type transformers use silicone rubber bushings, while most oil-type transformers use porcelain bushings;

8. Insulation and heat dissipation are different.

Dry-type transformers are generally insulated with resin, which is cooled by natural air, and large-capacity is cooled by fans, while oil-type transformers are insulated by insulating oil, and the heat generated by the coil is heated by the circulation of insulating oil inside the transformer. Heat dissipation is carried out on the heat sink (sheet) of the transformer.


Dry-type transformers are mostly used in places that require "fireproof and explosion-proof", and are generally easy to use in large buildings and high-rise buildings; oil-type transformers may have oil spray or leak after "accidents", causing fires, and are mostly used in Outdoors, and there is a site where an "accident oil pool" is dug. the

10.The load bearing capacity is different.

Generally, dry-type transformers should be operated under rated capacity, while oil-type transformers have better overload capacity. the


How to choose a dry-type transformer or an oil-immersed transformer?

Selection conditions

Dry type transformer

Oil-immersed transformer

Suitable for installation in densely populated places

(from safety point of view)


Larger voltage and capacity


cheap price


High environmental protection


low noise


Easy to transport


fire resistance


easy installation


Moisture-proof and dust-proof



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