Voltage Ratings: 110/115/120, 220/230/240 or 440/460/480

[jim dungar]

For Wye systems the letter Y is included in the descriptor which I believe is an IEEE standard such as 208Y/120 or 480Y/277. It's also directly from the NEC, a few examples:

Most utilities do not follow this standard nomenclature. But those of us that depend on the NEC should.

 

[JakupstateNY]

REA crews traveled through the American countryside, bringing teams of electricians along with them. The electricians added wiring to houses and barns to utilize the newly available power provided by the line crews. A standard REA installation in a house (post World War II) consisted of:

• A 60 amp, 230 volt fuse panel, with:

1. A 60 amp range circuit
2. A 20 amp kitchen circuit
3. Two or three 15 amp lighting circuits

A ceiling-mounted light fixture was installed in each room, usually controlled by a single switch mounted near a door. At most, one outlet was installed per room, since plug-connected appliances were expensive and uncommon.
Wiring was performed using type NM (nonmetallic
sheathed cable), insulated with asbestos-reinforced rubber covered with jute and tar.

History of REA

I also like to use this chart:
View attachment 2557797

Learning daily, thank you