why we create vaccume in transformer tank before oil
filteration?

Answer Posted / byd

Generally Hermetic Onan transnformer vaccume before oil
filteration and after oil filling,, because if there is
any air inside of transformer tank and oil then we
apply anergy after there will be short circuit and
insilation resistances will be min, and IEC 60076-1 High
voltage test, if transformer is 33kv, you should apply
mono phase to HV winding as 70kv for 1 minute,, if there
is any short circuit it means oil didnt vaccume ,, or
there is some insilation wrong ,, i am sorry my english
is not good

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