Likely a multi grounded neutral system, where single phase loads are typically connected line to grounded neutral. The concentric neutral on the cable carries the grounded conductor. Just curious why are there two cables connected in parallel? Is this very very long? I didn't do the math on how far you can run 7200 volts on a 4/0, but it's got to be dozens of miles .
The two cables are not in parallel. They terminate in a line selector switch on the transformer, so they are likely for redundancy/backup.
If anything, the primary could be called a wye, because it is intended to be fed from a wye system, and the standard call out for the primary would be "1247GY/2400" per IEEE standards. In field jargon, a transformer with two bushings on the primary is sometimes called a "delta", because it's fed from a Delta system (usually).
Generally yes I agree, however for single phase medium voltage transformers, they are often referred to by the type of system they will be fed from.
Utilities tend to follow their own industry slang and standards rather than what electricians use.
Agree, but IEEE Std C57.12.00-2015 in my experience is pretty much universally used, even for "utility transformers", and some of these have "wye" on the data plate (document attached).
