Paralleling Different Capacity Transformers

Is paralleling the transformers to be permanent or just temporary during a switching operation?

Dear Sir,

Any book in Electrical Engg will give you the General Conditions required for

the parallel operation of Transformers.

(1) Same Vector Group (2) Same turn ratio (3) % impedence with in 5 % variation

to limit circulating current among the Trs. (4) Protection Circuits to protect

Lessor capacity transformer from getting overloaded. (5) Preferable to have

equal capacity of Trs- or in the ratio 1:0.75 to be on safer side.

Manroop.Chennai