Dear ;
First, I'm surprised, because the ditributed Medieum Voltage that you should be used is normally defined by the ” Utility “, as the Utility defines accordingly to the consumed power from where the load should be electrified. In Syria for exp. The Utility defined as follow :
– The load up to ” 35kW ” will be connected directly to LV network ” 0.4kV “.
– The load up to ” 10MW ” should be connected to MV network ” 20kV “, that means the client will have a substation ” 20/0.4kV “.
– The load more than ” 10MW ” should be connected to HV network ” 66kV “, that means the client will have 2 substations ” 1st : 66/20kV ” & ” 2nd : 20/0.4kV “
But if you have the possibility to select one of 33kV or 11kV, please note that the transformer ” 33/0.415 kV ” is more expensive than ” 11/0.415 kV ” by around ” 15% “, and the Circuit Breakers ” 33 kV ” are also more expensive than ” 11 kV ” by around ” 3-4% “.
About the ” Step-Down ratio ” between HV and MV, please note that's approx ” 3.3 – 3.6 “, and some manufactures can produce transformers with more than this ration but the cost will be very expensive.
Regards.