Single Phase And Three Phase Loads

[Smart $]

These are for Asian PS where the transformers are delta and not Y.

For balanced 3? loads, delta or wye...

VA = √3 x E x I

...or...

kVA = √3 x E x I / 1000​

...where E is the line to line voltage and I is the current of each phase conductor.

In these cases the line currents are 1.732 of the phase currents. Is that so ?
but I am confused about the line currents that a transformer or facility will see.

This will only come into play for single phase line to line loads. Three phase load currents are stated in terms of phase amperes. A 30A, 3? load will tax each phase at 30 amps. A 30A, 1? load will tax each of the two connected phases at 30A if there is no other load on the other two line to line combinations (i.e. if the load is A-B, the 30A current will be reduced when loads are placed across A-C and/or B-C, and/or line to neutral loads on a wye system). If you have only a 30A, 1? load across both A-B and A-C, the current on A will be √3 x 30A. The current on B and C will remain at 30A each until other currents are on these phases. When other currents are added to B and C, the reduction per circuit in phase current would be √3/2:1 or 86.6% at best...

Click this link for a very similar forum discussion on this site.

In summation, designing the system as others have suggested here will provide adequate to superior performance. When you design using current reductions, you end up with a marginal system.