Medium voltage tray cables and EGC

[Dsg319]

I know next to nothing with MV equipment and requirements.

But on a job where we pulled 6 parallel 3c750kcmil tray cables with and 1/0 ground in the cable.

This is 4160v and coming off of from what I can tell is a 3000amp breaker.

How do they get away with not having a 400kcmil EGC ?.

Even with utilizing cable tray as an EGC at the expansion joints it as 4/0 jumpers for continuity.

I know there has to be more to this than what I know.
Just looking to get educated.

 

[mayanees]

I know next to nothing with MV equipment and requirements.

But on a job where we pulled 6 parallel 3c750kcmil tray cables with and 1/0 ground in the cable.

This is 4160v and coming off of from what I can tell is a 3000amp breaker.

How do they get away with not having a 400kcmil EGC ?.

Even with utilizing cable tray as an EGC at the expansion joints it as 4/0 jumpers for continuity.

I know there has to be more to this than what I know.
Just looking to get educated.

I too believe it needs to be a 400 kCMIL conductor for the EGC, in accordance with Table 250.122.

 

[Elect117]

250.122(A) - Last sentence

"Equipment grounding conductors shall be permitted to be sectioned within a multiconductor cable, provided the combined circular mil area complies with Table 250.122."

4160V conductor can have a concentric or shielding which acts like a fault current path back to the source where it is bonded at both ends. (250.190(C)(2)). The asterisk being that it is not a solidly grounded system and the shield is capable of clearing the fault before being damaged.

250.122(A) allows you to take the concentric + wire type egc as the size since it is all within the same cable.

 

[Dsg319]

250.122(A) - Last sentence

"Equipment grounding conductors shall be permitted to be sectioned within a multiconductor cable, provided the combined circular mil area complies with Table 250.122."

4160V conductor can have a concentric or shielding which acts like a fault current path back to the source where it is bonded at both ends. (250.190(C)(2)). The asterisk being that it is not a solidly grounded system and the shield is capable of clearing the fault before being damaged.

250.122(A) allows you to take the concentric + wire type egc as the size since it is all within the same cable.

Thank you!