Maximum Possible Size of Downstream Transformer

I don't see any issue with doing this.

Just ensure:

The primary and secondary cables of transformer, 11 KV bus and other related gears are rated for the additional load (it should be designed with the full capacity of transformer, but in case)

The transformer protection settings are adequate to avoid nuisance tripping with additional loads (I would suggest to do the relay coordination study)

-MS

The 25 MVA transformer is not a concern.

1. Can the 132 KV system take the added load.

2. Are the 11 KV conductors large enough for the added load? Voltage drop?

3 11 KV breaker ampacity.

4. Effect on other customers? Motor Flicker?

5 Does the Fuse on the 9 MVA transformer coordinate with the feeder breaker?

6 What did I forget?

My Friend,

Do what MSAMAD recommendations and add the "voltage dip" protections from the largest capacity/rating of the SQCI motor(s) to complete your system protections.

Eren