Just for those wondering how its done around here:
>5-30kv from generator;
>generator step up transformer: 5-35kv to 345kv, Delta Y grounded; 345kv transmission backbone with lighting wire, VTs connected P-G everywhere.
> 345kv to 115kv: Y auto transformer grounded with delta tertiary, (a few subs use the tertiary for 13.8kv distribution by adding a zig-zag for a neutral); 115kv with lightning guard, all VTs P-G.
> lower level generation: gen voltage to 115kv, Delta Y grounded.
>115kv to either 13.2, 13.8 or 23kv distribution, Delta Y grounded; distribution system is 3 phases with a multi grounded neutral and single bushing transformers, all loads wye with a few delta connected on large Kva banks.
>115kv to older 69kv segments: Y grounded auto transformer, some have delta tertiary. 69kv one tall towers has a lightning guard, 69kv on short wooden poles is 3 wire only.
>69kv to 13.8kv distribution: Delta Y grounded
>69kv to 23kv or 27.6kv sub-transmission: Delta Y grounded, some have a 3rd 4.8kv tertiary for back in the day distribution; sub-transmission is 3 wire on wooden poles.
>115kv to 23kv or 27.6kv sub-transmission: Y grounded Y grounded, 4.8kv delta tertiary, was used to supply 3 wire ungrounded delta distribution years ago, now left unconnected. 23kv or 27.6kv is 3 wire on wood poles.
>27.6kv to 23kv distribution: Delta Y grounded
>27.6kv to 13.8kv distribution: Delta Y grounded
>27.6 or 23kv to 4.8kv distribution: Delta Delta; this system is no longer used and was 3 wire with all loads delta connected.
Of note 27.6kv sub-transmission is being phased out for being non standard, and 23kv 3 wire sub transmission are now mostly converted to 4 wire distribution with a multi grounded neutral and use single bushing 13.2kv transformers. Years ago 13.8kv was also considered sub-transmission and was 3 wire but is now exclusively 4 wire distribution.