As the names indicate, the main difference between dry-type and oil-cooled transformers is their medium of cooling. While conventional transformers are cooled and insulated by oil, dry-type transformers only use air to stay cool.
This cooling function is vital, as transformers generate heat through the losses that occur in the windings and core as energy is converted from one voltage level to another. The heat dissipation generally increases with the capacity of the transformer. Effective cooling is essential not only for the performance of the transformer, but for its safety and longevity.
Oil-cooled transformers need regular testing and changing of oil, as it tends to deteriorate over time. Their structure and joints also need to be inspected regularly to avoid leakage of oil, which can have serious environmental impacts.
The absence of oil in dry-type transformers makes them easier to maintain, making them more suitable for remote locations. There is also no risk of environmental impact through oil spillage.
