Description
Hermetically Sealed Oil Immersed Distribution Transformers
Manufactured with power ratings between 25 – 5000 kVA and voltage levels up to 36 kV,
these transformers are available as single-phase or three-phase units with natural oil cooling (ONAN).
They can be produced with off-circuit tap changers or automatic on-load tap changers.
They are suitable for both indoor and outdoor applications.
In hermetically sealed transformers, the contact between transformer oil and atmosphere is eliminated
through vacuum oil filling. This prevents oxidation and protects the insulating oil against moisture
and atmospheric pressure changes.
Pressure variations caused by thermal expansion and contraction are naturally compensated through
the expansion of the tank walls. Therefore, the transformer tank is designed with high mechanical
strength and safety.
Hermetically sealed transformers provide installation advantages in limited spaces due to their lower
height compared to expansion tank models. Since the oil does not come into contact with the atmosphere,
regular oil replacement is not required.
Conservator Type Transformers
Conservator type transformers have a similar core and winding structure to hermetically sealed models.
However, they are equipped with an expansion tank designed to compensate for oil volume changes
caused by temperature variations.
In these systems, oil pressure changes caused by atmospheric exposure are balanced through a silica gel
breather. The silica gel absorbs moisture from the incoming air and prevents contamination of the
transformer oil.
Since silica gel loses its moisture absorption capability over time, periodic maintenance is required.
Regular replacement of silica gel and monitoring of oil levels ensure long service life and reliable
transformer operation.
