transformers

[instrument]

It just confused me on the design that ive seen from a contractor... they had installed a 100KVA transformer for a 460V primary from (MCC) to 230V to utilities (3phase), and the protection 150A and 400A circuit breaker for primary and secodary respectively.Of course based on the computed load came to arrive for the protection of 400A breaker. and if you based it for computation of the protection it just only 125% of the rated current of the transformer. is it okay?...pls correct me if Im wrong?

Also is it okay if I use a power cable of 1-50square mm and 1-90square mm just to comply for the size of power cable, say 145square mm,required for rated current (primary) of the 100KVa transformer...
Correct me if Im wrong...your feed backs are highly appreciated...thanks more power

 

[brian john]

Instrument:

Now I am confused.

1.The utility (power company) is 230 VAC the contractor is taking this to a Transformer and stepping this up to 480 VAC.
2.The utility power company is supplying 460 VAC this feeds an MCC that is to have OCP for a 480 to 208 transformer to feed loads you term as utilities.
3.I am assuming the transformers are delta/delta or are they delta/wye so the 230 VAC secondary actually is 208/120 VAC?

 

[instrument]

transformer primary protection

transformer primary protection

Im sory for making you confuse...and the term that i'd use.
Ourpower utility (driven by steam) delivers 4160v for every MCC that we have...now from MCC has its own transformer to step down to 460v (DELTA)...

Now im confused for the contractors protection to transformer down to loads. The transformer that id said is a DELTA-DELTA connection. From MCC to loads 460/230v. now on their design primary CB is 150A which is 125% of the x'former rated primary current...and 400A CB for secondary (computed from loads)

wire size is 1-50sq mm and 95sq mm on primary and secondary 1-180sq mm...assuming primary cables are correct, is this two cables used are complying 145sq mm cable requirement