Size of equipment grounding conductor on 4160V circuit

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frnkhr

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I understand the equipment grounding conductor is sized based on NEC 250.122(A): "General. Copper, aluminum, or copper-clad aluminum equipment grounding conductors of the wire type shall not be smaller than shown in Table 250.122,??. Table 250.122 lists the minimum size equipment grounding conductor per the "Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of Equipment,...".

On a 4,160 volt circuit, is this the setting of the 50/51 relay (2000 Amp setting which requires a 250 kcmil copper equipment grounding conductor in my case), or the setting of the 51G relay (400 Amp setting which would require a #3 copper equipment grounding conductor in my case)?
 

charlie b

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Location
Lockport, IL
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Retired Electrical Engineer
It is based on the overcurrent trip setting of the breaker (or fuse, if applicable), not the ground fault protection setting. So the 250 MCM copper EGC is called for in your application. Welcome to the forum.
 
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