Sizing a Neutral Conductor

What is the max possible current that can eventually flow through such a grounding wire. Double it, then size the wire.

Determine the following:

1. Line to ground fault that will flow to the neutral conductor.

2. Time to Clear the fault

3. Conductor temp and Short circuit temp.

then use the formula below as per NFPA 70.

Det. the ff:

1. Line to ground fault that will flow to the neutral conductor.

2. Time to clear the fault.

3. Temp of conductor and SHort circuit.

then us the formula below as per NFPA 70/

Thanks for everyones help however I had hoped to read a thread from NEC that simply states (from tables), how to size a neutral wire that is used for grounding and not a current carrying conductor. Since the neutral is grounded and the ground grid is connected accordingly it would appear that they would be the same!

Check this book for Grounding Grid calculation ( IEEE 80 guide for safety in AC substation grounding 2000. )

First off... you are using language that is rather confusing. Are you looking to size the "neutral conductor" or the "grounding conductor". They are not the same thing.

I designed switchgear for compressor stations. The customer had me install a ground bus and a neutral bus and connect them both to ground. System voltage is 480 v, 3 phase. He specified a 300 amp ground bus and a 1200 amp neutral bus. The circuit breaker is rated at 1200 amp LTP. He required a surge suppressor as well. Makes no sense to me why he would have a ground bus and a neutral bus but he does. The ground bus is tied into his grounding grid. I'm not much on NEC rules as I don't use them much and thought there would be a NEC table that would simply state the ground/neutral size relative to the current carrying conductor size.