Oil type distribution transformers can change the input and output voltages up to 36 kV voltage levels with a capacity of 5000kVa power in desired ratios. The heat generated during operation is maintained and cooled at the normal temperature level with transformer oil. This type of transformer can be examined under two main headings as hermetic and conservator tank:

They are produced in a range of 25 – 5000 kVA, up to 36 kV high voltage level, with three or single phase, oiled, naturally cooled (ONAN), idle tap changer, or automatic on-load tap changer, both externally and indoors. Hermetic oil type distribution transformers are manufactured by filling the oil under a vacuum by balancing the oil pressure and atmospheric pressure at the desired temperature and not allowing the cooling oil to come into contact with the atmosphere.

As a result of changing oil pressure due to thermal changes in hermetic oil type distribution transformers, the internal heat is controlled by a natural conservator and contraction of boiler wave walls. Mechanical design and manufacturing are made to withstand these effects.

Hermetic oil type distribution transformers are shorter in length than a conservator tank transformer”. Therefore, it can be used in smaller areas.

Since the oil does not come into contact with the atmosphere in hermetic transformers, it does not require oil change in certain periods as in a transformer with a conservator tank.