Grounding at Power Plants
- Thread starter FER3
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charlie
Senior Member
- Location
- Indianapolis
It depends on the electric utility that owns the power plant. The NESC is the document that applies and it is up to the utility's professional engineer engineer to specify the size to be used to comply with the NESC. Since the NESC is a performance document, you can't just go to a table to find easy answers.FER3 said:
rcwilson
Senior Member
- Location
- Redmond, WA
Some installations need 500 kcmil or larger. Many use 250 kcmil. It depends on the maximum future fault level at that location, the fault clearing time, how much corrosion allowance the engineer or utility wants to add on, and other factors. That said, #4/0 awg is good for most installations. Check with the engineer.
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
Municipal and Utility owned power plants and substations are not under jurisdiction of NEC. Plants built by IPP's (Independent Power Producers) are.
With that said, either way, the ground grid is designed to reduce step and touch potentials to safe levels. You cannot arbitrarily use a size of conductor and think it is OK. The size of the conductor, the number of ground rods, placement of ground rods, grid spacing of grid conductor, amount of fault current contribution (now and in the future); all must be considered in the calculations. The calcs should then be reviewed by someone competent in grounding design. Therefore, a single conductor size does not fit all situations.
With that said, either way, the ground grid is designed to reduce step and touch potentials to safe levels. You cannot arbitrarily use a size of conductor and think it is OK. The size of the conductor, the number of ground rods, placement of ground rods, grid spacing of grid conductor, amount of fault current contribution (now and in the future); all must be considered in the calculations. The calcs should then be reviewed by someone competent in grounding design. Therefore, a single conductor size does not fit all situations.
D
dicklaxt
Guest
IEEE 80 is a really complete and complex doc that is oft used for guidelines. I got a copy last week in preparation for a 13.8 system with 4.16 and .48 swgr and MCC's. Its really boring reading and its long but hey if you do it per the book your home free of most liabilities. There are a couple of more IEEE docs I think 988 and 942 or something close . IEEE 80 will probably ref the others.
Wish me luck
dick
Wish me luck
dick
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