MGN and EGC

[bwat]

On a medium voltage customer-owned MGN system, can you use the neutral as the method to ground equipment? Or do you have to run separate EGCs?

Electrically, I feel like I could make an argument for either way. The separate EGC is pointless because it's directly in parallel with the neutral and could carry current in normal conditions. Or the separate EGC is a good idea because it ensures continuity between metallic components (even though it would be there anyway).

Envision some MV gear fed from utility MGN feed. N-G share a common bus in this gear and there exists GEC to ground rods, then what wires would you need to bring from the gear to a YgYg transformer?

250.190(A) Kind of makes me think that I could use neutral as grounding method.

250.190 Grounding of Equipment.
(A) Equipment Grounding. All non–current-carrying metal
parts of fixed, portable, and mobile equipment and associated
fences, housings, enclosures, and supporting structures shall be
grounded

It simply says "shall be grounded". Well if we're talking about the transformer, and the neutral is being grounded there again, then connecting to the neutral certainly seems logical to say it is being grounded.

Part X of article 250 leaves some clarity to be desired...

 

[electrofelon]

On a medium voltage customer-owned MGN system, can you use the neutral as the method to ground equipment? Or do you have to run separate EGCs?

Electrically, I feel like I could make an argument for either way. The separate EGC is pointless because it's directly in parallel with the neutral and could carry current in normal conditions. Or the separate EGC is a good idea because it ensures continuity between metallic components (even though it would be there anyway).

Envision some MV gear fed from utility MGN feed. N-G share a common bus in this gear and there exists GEC to ground rods, then what wires would you need to bring from the gear to a YgYg transformer?

250.190(A) Kind of makes me think that I could use neutral as grounding method.

It simply says "shall be grounded". Well if we're talking about the transformer, and the neutral is being grounded there again, then connecting to the neutral certainly seems logical to say it is being grounded.

Part X of article 250 leaves some clarity to be desired...

Yes I agree the wording is poor. The title of part X is:

"Grounding of Systems and Circuits of over 1000
Volts"

But they seem to skip over bonding/equipment grounding and seem to just assume you will do that by bonding to the neutral. 250.184(C) talks about "grounding" the neutral at each piece of equipment and they seem to mean earthing. They dont seem to address how to bond the equipment. I think we just have to assume we bond to the neutral because otherwise it would be single point and covered in 250.184(B).