Sizing equipment grounding conductor for impedance grounded system

C

chuckd83

Member
Is there a special provision for sizing an equipment grounding conductor for an impedance grounded system? Say it is a 400A resistor so the EGC will see a maximum of 400A for 1-2 seconds during a ground fault. Does it still have to be sized per Table 250.122?
 
I’m pretty sure you need to look at 250.36(A) through (G). It lays out the rules based off of how you have it set it up… hopefully that helps
 
ron said:
A L-G fault results in the impedance grounded system to become a grounded system for a 2nd fault. The EGC is sized per 250.122
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Thanks. The "automatic overcurrent device" ahead of the equipment has both a phase and ground setting. Does the NEC specify which one to use?
 
I believe that would depend on what you are looking for the device to do in regards to what it’s protecting. I think you should refer to the manufacturer instructions of the device you have… correct me if I’m wrong, but I’m pretty sure there isn’t anything in the code that would tell you what setting to chose
 
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