Advantages and disadvantages of Oil Immersed Distribution Transformer and Dry Type Cast Resin Distribution Transformer
1) Cooling media
In oil immersed distribution transformer used oil for a heat conductor, and heat is released through the radiator fins. Because the oil that used have a flash point in temperature from 160 to 180 (mineral oil), so the oil immersed distribution transformer need placed in the separate place, in case a fire occurs in the transformer, it does not endanger in the public space.
And in the dry type cast resin distribution transformers, the coil exposed to air, so the heat immediately released. Usually, the heat release supported by several fans that mounted on the bottom of the transformer. The transformer uses fire-resistant resin material, so it is safe to be placed in buildings.
Oil immersed distribution transformer need maintenance like purification/ periodic oil changing, bushing packing changing, bushing torsion and connection torsion check, silica gel changing in the breather, etc.
Dry type cast resin distribution transformers require torsion check periodically on the busbar connection. No oil leakage potential issue.
Oil immersed distribution transformer more efficient than Dry type cast resin distribution transformers, because oil immersed distribution transformer have more space, while the Dry type cast resin distribution transformer’s size is limited to the cast resin moulding dimension.
Dry type cast resin distribution transformers are more sensitive to overheating and high losses when subjected to overload.
B&D transformer have experience to manufacture the Dry type cast resin distribution transformers up to 5000 kVA and Oil immersed distribution transformer up to 167 MVA 275 kV (Power Transformer).
In the another literature explain that the Dry type cast resin distribution transformers is more noisy than the oil immersed distribution transformer. This noise is caused by the magnetostriction phenomenon, which causes the dimensions of the iron core to change (stretch & shrink) When magnetized (at a very small scale). When not magnetized, the core dimension return to the original size, so that make a buzzing sound in the transformer.
But as long as our experience, noise in the both of the transformers at normal load is relatively the same, not more than 60 dB.
Advantages : Dry type cast resin distribution transformers have lower partial discharge than Oil immersed distribution transformer. Dry transformers are also more resistant to sort circuits, and have better resistant to lightning impact / impulse (lightning strike).
But the Dry type cast resin distribution transformers have more losses than Oil immersed distribution transformer.
At the same capacity, Dry type cast resin distribution transformers have a higher price than Oil immersed distribution transformer. This is comparable to the advantages offered by the dry transformer.
In field applications, customers will tend to choose a dry transformer if the transformer is to be placed in a high rise building, And will choose the oil transformer if the transformer is to be placed in an isolated place from the public area. For a big transformer capacity (above 5000 kVA) it would be better to choose an oil transformer regarding its efficiency.