First of all, I would like to thank you for making this incredible site, where we can ask or answer questions.
Right now, In a third world country far, far away, where the system sub-transmission works at 60 Hz 115 KV and distribution works level is 13.8 KV, I receive a entire uncompleted project of a "campus". Due to the project is going to be constructed by parts, for example one year a building then maybe 3 years later another and so on, I'm dealing whit which distribution design is better. A schematics goes like these:
The buildings have an area of 500x250 mts: Estimated Power-Demand: 1.2 MVA
I divided the building in 4 Zones and feed them with 4 pad-mounted transformers (see image, click for a larger version).
Δ: Pad-Mounted Transformers 400 KVA in ring-bus.
---: 13.8 KV from S/E feeders. (underground)
So my question is, in your experience is this a good distribution practice method?
Or I'm missing something? what would you believe is a critical issue here?
Or is better to put a switch-gear and then go with radial transformers? I did not mention vault transformers because the building foundations are already under construction.
Other criteria would be to use dry-type transformers inside the building. But I don't want to get inside the building with an industrial voltage, and going inside with 480/277 V does not make sense if all air conditioners units will work at 208V according to mechanical specifications.
I would like to thank you for taking your time to read my question.