Noise from Transformer

[Vikram]

Hi,

We have a 5 MVA transformer.  Of late we have been hearing a noise from inside the transformer.  This noise is different from the normal humming sound from the transformer.  What can be the possilble reasons?

[Ajay]

Transformers produce a humming noise during normal operation. This noise is caused by magnetostriction and is normal.

However, it is necessary to investigation any other noise from transformer and take prompt remedial action. Different types of Transformer noises may indicate different abnormality.

Hissing sound may indicate partial discharge across the bushings. Probable cause may be dirt accumulation on surface

Excessive humming sound may indicate overvoltage

Chattering sound can indicate loose connection

A sharp squealing sound may indicate improper contact in the tap changer. The transformer should be stopped at once.

A buzzing sound can indicate overload.

Inter turn short circuits tend to cause a sound similar to boiling water. This is because the discharge causes the gasification of the transformer oil. A discharge from the winding to the transformer tank through the oil can also cause this boiling sound

[titangsu]

good answer. thanks