Generators as prime power

[ishium 80439]

I'm hoping to find some guidance regarding generators. Most everything I can find regarding generators deals with portable or back up but I'm working overseas in an environment where they are essentially prime power. I've tried to research this but honestly the more I dive into it the more I confuse myself. I'm hoping some of you can provide me with some clarity.

I'll give a direct example and then extrapolate out from there. There is a 120 kW generator being brought on line. There is a neutral to ground bond in the gen. it will feed out via G cable and a pin and sleeve connector to essentially a spider box. Out of that spider box are more pin and sleeve connectors and more G cable going out to the various loads.

The simple question is this: does this generator need a ground rod? (For what it's worth the gen will not actually be in touch with the earth- it sits on 4x4s inside a containment bladder to catch fuel spills.) I've read that it does, I've read that it does not. The way that I'm looking at this is that I'm not sure what the ground rod will add. But I've been known to be wrong before.

Any opinions you have would be appreciated (well, opinions about the grounding thing- if you're opinion is that I'm funny looking and listen to bad music, well those wouldn't be appreciated...)

 

[kwired]

I'm hoping to find some guidance regarding generators. Most everything I can find regarding generators deals with portable or back up but I'm working overseas in an environment where they are essentially prime power. I've tried to research this but honestly the more I dive into it the more I confuse myself. I'm hoping some of you can provide me with some clarity.

I'll give a direct example and then extrapolate out from there. There is a 120 kW generator being brought on line. There is a neutral to ground bond in the gen. it will feed out via G cable and a pin and sleeve connector to essentially a spider box. Out of that spider box are more pin and sleeve connectors and more G cable going out to the various loads.

The simple question is this: does this generator need a ground rod? (For what it's worth the gen will not actually be in touch with the earth- it sits on 4x4s inside a containment bladder to catch fuel spills.) I've read that it does, I've read that it does not. The way that I'm looking at this is that I'm not sure what the ground rod will add. But I've been known to be wrong before.

Any opinions you have would be appreciated (well, opinions about the grounding thing- if you're opinion is that I'm funny looking and listen to bad music, well those wouldn't be appreciated...)

The generator itself probably doesn't need a ground rod.

The wiring system you connect it to likely does need a grounding electrode system though.

 

[ishium 80439]

That is what I'm trying to understand. What these G cables are feeding are mostly tents with a pre-packaged wiring system- plug and play if you will. There is no concrete, there is no piping, there is no structural steel.

I took a grounding and bonding class with Mr. Holt about a year ago and I unfortunately left my notes and his book back home. What I do remember from that class was that ground rods were really over hyped and essentially provided some marginal level of lightning protection. There was a bit more to it but that is what I remember it boiling down to.

So in this situation what purpose would a ground rod serve? If one is needed where would you put it? At the first spider box? To reiterate the more I try to reason this out the more I confuse myself....

 

[romex jockey]

i found this in 250>

(2) Grounding Electrode. Except as permitted by 250.34 for
portable and vehicle-mounted generators, the grounding elec‐
trode shall comply with 250.30(A)(4).

~RJ~

 

[kwired]

i found this in 250>

(2) Grounding Electrode. Except as permitted by 250.34 for
portable and vehicle-mounted generators, the grounding elec‐
trode shall comply with 250.30(A)(4).

~RJ~

If that is 250.30(B)(2), which I think it is, (B) is titled "ungrounded systems"

But then it is sending you to a section in (A) "grounded systems" so I guess it applies whether a grounded system or not.

 

[romex jockey]

Thx Kwired

I'm confused

what's the theory here? do we protect the structure,or the power source from mother nature, or both?

~RJ~

 

[kwired]

Thx Kwired

I'm confused

what's the theory here? do we protect the structure,or the power source from mother nature, or both?

~RJ~

We install a grounding electrode - unless it is portable or vehicle mounted generator.

Now if you are supplying fixed premises wiring you need a GES at each structure no matter what the source is, even if it is an ungrounded system.

 

[ishium 80439]

Thanks for the responses. Forgive me if this is an ignorant question but I'm really trying to understand this. What role does the ground rod serve in this installation? What is the role of the grounding electrode here?