Grounding Conductors separately dervived system

[elliot]

Here is the scenario: The building has a 15kv primary service with the swbd located indoors: We are replacing an indoor double ended 15kv-480v substation lineup with Main-Tie-Main scheme. To minimize interuption and help with space requirements, we are istalling (2) oil filled 2500kva transformers outdoors and a 3R main-tie-main swbd (3000a mains and tie). There are (8) sets of 4"c PVC from each transformer secondary to their respective main breakers. The system grounding and bonding will take place in the M-t-M swbd. Here is the question: Is a grounding conductor required in each of these conduits. As you know there is only a 1/2" ground stud for grounding in pad mount oil filled and (8) 4"c filles the secondary compartment, with (8) sets of (4)600kcml, there is no room to terminate (8) grounding conductors.

Please help with code reference. I was not sure if 250.30 was giving me some relief from this or not.
Look forward to some input.

 

[RB1]

In this case I think 250.30(A)(1) Exception No. 2 will permit you to install a bond at both the transformer and switchboard. A single 600 Kcmil from XO to the 1/2 stud in the transformers will give you the bond you need at the transformer. Repeat as needed at the switchboard. Because of the nonmetallic raceways I think the exception applies.

 

[augie47]

I respectfully disagree. I read exception as grounding at the source and first disconnecting means. To me, the 3000a 3R enclosure is the 1st disconnect and the inside switchboard is a sub. An 400 kcmil equipment ground should be in each of the conduits, IMHO.

 

[RB1]

I may have misread. I interpreted the source to be the two 2500 KVA transformers and the first disconnecting means to be the NEMA 3R switchboard.

 

[augie47]

On third reading, I believe you are correct and I misread. The OP seems to be questioning the conduits from the transformers. I misread that he was question the conduits between the two switchboards. (sorry..reading is not my forte' )

 

[elliot]

The question I am asking is: Is a grounding conductor required in each of these conduits. (from the transformer secondary to the NEMA 3R swbd where the system neutral will be grounded and bonded.)

 

[augie47]

I misread//I agree with RB1