Voltage Drop Increase on a Minimum Neutral for a 3W Service?

[ziggy-zag]

I have a 225A fused service entrance disconnect, 480V, 3PH, 3W. Ordinary utility owned transformer, ordinary wye-gnd secondary. Service conductors to be 3-#4/0 with a neutral i.e. grounded conductor (GC) per 250.24(C). GC to be #2 per Table 250.102(C)(1). Then, realizing it is almost 1500 feet away, we will have to look at voltage drop. Now, under the principle of 250.122(B), if the 3-#4/0 are increased in size for a reason not relating to ampacity, then EGC's must be also increased in size, proportionally. 250.122(B) only explicitly applies to EGC's, but it seems intuitive it should apply to the #2 GC as well in this case. It would not apply to the two grounding electrode conductors (one at the service disconnect, one at the transformer).

So my question is if this logic is sound, and maybe if this is an oversight by the code? Or there's a part of the code I don't know? If the #2 GC was an EGC, it would only be required to be #4 based on the 225A OCPD. But what if the 3-#4/0 were increased in size (for voltage drop) proportionally more than the change from #2/#4? oR... say the service entrance conductors were increased to 400kcmil, we would have to circle back to Table 250.102(C)(1) which would then call for a #1/0 GC since the ungrounded conductor is greater than 350kcmil. Same effect, but for some reason that just seems like a convenient coincidence and not the full picture. If VD was only increased to 350 it would have remained #2 under the same logic.

NEC 2020

 

[waross]

This is to limit the voltage rise on possibly exposed energized surfaces in the event of a fault to an exposed surface.
In a 480 Volt system, the line conductors and equipment grounding conductor will form a voltage divider across the 277 Volts to ground.
As the equipment grounding conductor is smaller than the line conductors, the touch voltage on the exposed energized surface will be more that 50% of the 277 Volts.
If the size of the line conductors is increased without a corresponding increase in the size of the ECG, the touch voltage will rise further.
A second concern is that if the line conductors are increased to address a longer length, the longer length and greater impedace on an EGC that is not increased may limit the fault current enough to extend fault clearing times.


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Ohm's law
Not just a good idea;
It's the LAW!