Increase in impedance of transformer

[kimseunghee]

Six step-down transformers(6.6kV/440V) are used for refregerator containers. These are fed from local power socket box via local power distiribution board. There is MCCB in the the local socket. This MCCB does not withstand estimated fault current.
As a measure, I am considering significant increase in impendace of transformer.
I am not sure if there is any limitation in increase or any side effect. I know ther is more voltage dip but When generator come on the line these containers are not engerzied because feeder breakers to TR is under volatge tripped. I should wsitch on after power restoration.

 

[alehman]

An MCCB with a higher short circuit rating may be a better approach. Higher impedance will reduce fault current, but depending on how high it must be could cause voltage dip problems (or possibly harmonic distortion) if drives are involved.

 

[pwrtran]

You may consider MCCB cascading with current limiting fuses.

 

[123MB]

Is there an MCCB in the local power distribution board (upstream of this MCCB that has less than acceptable fault withstand)

Have you looked at how the two cascade at the moment?

 

[123MB]

How would one increase the impedance of the transformer while keeping voltage constant?