Service entrance grounded or grounding

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kralcp

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Do I pull in a neutral or a ground with my parallel conductors and then what size?

The system is:

1500kVA service from utility owned pole mounted transformers, 12470/7200 primary with 100 amp fuses.

480 center grounded Delta secondary (yeah, I know - all they would give me, I have no 240 volt loads) feeding a 2000amp fully rated breaker in a 3 phase 3 wire MCC.

transformer X0 is grounded

I think I have to have parallel runs of 600kcmil (MCC lug limit) and full 600kcmil neutrals. I think the full size neutrals are required per the "delta" requirment of 250.24.C.1

Is this correct? I have a consultant that is saying I need to pull an equipment ground and don't need the neutral. I still calculate this to be 350kcmil if required based on upstream fuse size.

Which is it? - or is it something else.
 
This animal appears to have two heads.
It can't be both a 480 volt, corner grounded delta and a transformer with a grounded XO.
If the transformer has an XO terminal that is grounded, then you must install a grounded conductor and the phase conductor can not be grounded.
 
Not corner grounded. I should have said along with "center grounded delta" that ONE "transformer X0 is grounded". It is a 480 Delta with one transformer center tapped to give 480 phase to phase and 240 phase to ground on 2 phases and 415 (high leg) on the other.

I don't think my code reference above is relative since this is a 4 wire system. So do I pull in a 1/0 grounding electrode conductor per T250.66 based on parallel 600kcmils or do I size an equipment ground for the upstream transformer overcurrent protection size. Modelling the transformer in ETAP equates this to be equivalent to about a 80 amp fuse on the secondary which would require a 250kcmil equipment gnd per T250.122.

Which way is correct? Does this service require a grounded or a grounding conductor be run. I have no use or place to connect a neutral, just a ground bus that does not appear to be rated to even physically support 6 250kcmils. ground bus only has 2 lugs (could add a third) that appear to be about 1/0 rated.
 
That system is totally foreign to me, but 250.24(C) would appear to require you to install a grounded conductor. In addition, per that section a 1/0 per raceway would be required.
 
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