Transformer running operation

Transformer parallel operation conditions:
1, the same connection group
2, the transformer ratio equal (allowable difference of 5%)
3, the short-circuit voltage equal to (allowable difference of 5%)
Or short-circuit air circuit breaker  transformation Circuit breaker of the transformer is not equal, will not at any side of the case of overload, the line can be tied.
Unequal transformer  mcb circuit breaker  impedance, may be appropriate to increase the high short-circuit impedance transformer secondary voltage, so that parallel operation of transformer capacity can be fully utilized.