Article 220.5

[Dennis Alwon]

Does anyone know why the voltages specific to 277V and 208V are omitted. I know it seems redundant but it is there for the other voltages

220.5 Calculations.
(A) Voltages. Unless other voltages are specified, for purposes
of calculating branch-circuit and feeder loads, nominal
system voltages of 120, 120/240, 208Y/120, 240, 347,
480Y/277, 480, 600Y/347, and 600 volts shall be used.

 

[GoldDigger]

Does anyone know why the voltages specific to 277V and 208V are omitted. I know it seems redundant but it is there for the other voltages

It sure looks like that are assuming that those voltages will never be present except as part of a three-phase system. The other voltages are likely to appear as line to neutral voltages in single phase system as well as line to line or line to neutral in three phase.
How they came to that conclusion, I cannot say. On that basis, it looks odd to see 347 there on its own.
As you say, it does not affect the calculation in any way, but I agree that it is odd.