Neutral Connection in a System Grounding

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ronaldrc said:
If you want to use an analogy

Do this, take a pickup truck set you a 5 kw 120 volt portable generator in the back of it take a extension cord cut the female plug off and splice a temporary light socket pig tail with a 100 watt light bulb in the socket.


Now drive a ground rod in the ground at the back of the truck, Oh say a few feet from the truck.


Now plug the cord in the GFI receptacle that most the new generators have, start the generator the bulb should be lite.

Now take the wire nut off the black wire of the pigtail, but please don't take it apart and get between it.

With the wire nut off and the bulb lite touch the black wire to the ground rod, Please make sure you are not touching the pickup or generator when you do this.

If the GFI trips you all are right if it doesn't Larry and myself are right, I will take your word for it. :D
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For the GFCI to trip there must be a complete circuit back to the frame of the generator. My point is that if the ground rod is not part of the fault current path then it is not needed in order for a GFCI to operate.

Do you intend the ground rod be bonded to the generator in any manner?
What happens, if there is no ground rod at all, and you touch the generator frame instead?

I do not own a generator or a pickup truck.:mad:
Have you tried this experiment?
 
Hello Jim

No the rod is not hooked to any thing just like not being there as far as function.

But this is the same thing we where talking about, instead of being a house
on a wood/Block foundation its in a pickup truck. :)
 
ronaldrc said:
If the GFI trips you all are right if it doesn't Larry and myself are right, I will take your word for it. :D
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I am confused with your interpretation of the outcome. Last night Larry wrote:
Lose the earth, and the GFCI doesn't work.
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I say the GFCI will not operate as the ground rod is not part of the fault current path. But if you touch your test lead to the generator frame it will trip even though no ground rod is connected.
 
You or we should be right because like you said there is no place for the current to get where it needs to go, which is around the GFI CT. coil.

Larry was talking about standing on the ground outside at the GFI outlet with something plug in it sitting on the ground which would be equal to the rod with a fault to the case or metal encloser. And assuming it wasn't grounded with the equipment ground.It wouldn't trip the breaker we don't think even considering the capacitance. But as Larry said you don't really need the GFI under those cicumstances since there will not be enough fault current to even feel.

Anything thats a good conductor thats bonded to the neutral on the inside of the house like the kitchen metal toaster or range would trip it as usual.


And George and Don, you all did not mention the next door neighbors grounding rod. :D
 
jim dungar said:
What about a corner grounded delta? How about a transformer with only a 2-wire output?

But, as you mentioned it is the bonding that is most important.
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A corner grounded transformer is a grounded system also. If any transformer is grounded it qualifies it as a grounded system.

If none of the phases are grounded and it has no neutral it is an ungrounded system.
 
ronaldrc said:
If you want to use an analogy

Do this, take a pickup truck set you a 5 kw 120 volt portable generator in the back of it take a extension cord cut the female plug off and splice a temporary light socket pig tail with a 100 watt light bulb in the socket.


Now drive a ground rod in the ground at the back of the truck, Oh say a few feet from the truck.


Now plug the cord in the GFI receptacle that most the new generators have, start the generator the bulb should be lite.

Now take the wire nut off the black wire of the pigtail, but please don't take it apart and get between it.

With the wire nut off and the bulb lite touch the black wire to the ground rod, Please make sure you are not touching the pickup or generator when you do this.

If the GFI trips you all are right if it doesn't Larry and myself are right, I will take your word for it. :D
Click to expand...

And this is considered a grounded system with or without the electrode because a neutral exists.
 
Tryinghard

I will let someone else put a name on it.

Electrical names like me don't make much sense I'm mean they call a SDS a seperate Derived system athough it is tied to the High voltage lines? And the NEC says it shouldn't be. :)
 
ronaldrc said:
Tryinghard

I will let someone else put a name on it.

Electrical names like me don't make much sense I'm mean they call a SDS a seperate Derived system athough it is tied to the High voltage lines? And the NEC says it shouldn't be. :)
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Basically there are two types of AC systems: grounded and ungrounded.

The ungrounded system 250.4(B) is intentionally ungrounded, none of the phases ? A, B, or C ? of the secondary are bonded to frame or grounded.

A system that is required to be bonded and not bonded or grounded is a violation not an ?ungrounded system?.

A generator 250.34 is usually a grounded system and rarely an ungrounded system. When it?s a grounded system as described in 250.34 it frame is the ground plane and an additional electrode to earth may not be required but it?s still a ?grounded system?. :grin:
 
Okay, let me restate my position one more time, if I may:

In order for a GFCI device to perform its intended function, whatever surface or material you want to protect personnel against electrocution while in contact with during accidental contact with an energized conductor, must be bonded to another conductor of the supply.

In other words, if a wiggy* that is placed between the energized conductor, and whatever conductive surface would eventually lead back to the source at a point of a different potential, is activated enough to indicate real power, then a GFCI device would properly trip.

*For the sake of this discussion, let's pretend that the wiggy's impedance is just enough to trip a GFCI.

Now, if that leaves anything less than clear, I give up. :roll:
 
LarryFine said:
Okay, let me restate my position one more time, if I may:

In order for a GFCI device to perform its intended function, whatever surface or material you want to protect personnel against electrocution while in contact with during accidental contact with an energized conductor, must be bonded to another conductor of the supply.

In other words, if a wiggy* that is placed between the energized conductor, and whatever conductive surface would eventually lead back to the source at a point of a different potential, is activated enough to indicate real power, then a GFCI device would properly trip.

*For the sake of this discussion, let's pretend that the wiggy's impedance is just enough to trip a GFCI.

Now, if that leaves anything less than clear, I give up. :roll:
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I cirtainly agree! :)
 
Here is a Mike Holt illustration which should explain why the GFI receptacle
would not work without a system ground electrode to the earth or dirt as some say.

I better add this is with a outside GFI receptacle with something setting on the ground plugged in and with a fault. :)




1010776626_2.gif
 
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ronaldrc said:
Here is a Mike Holt illustration which should explain why the GFI receptacle
would not work without a system ground electrode to the earth or dirt as some say.

I better add this is with a outside GFI receptacle with something setting on the ground plugged in and with a fault. :)
1010776626_2.gif
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So under very specific circumstances a an electrode would be needed for a GFCI to operate ........... of course in the example in the picture if the system was truly 'ungrounded' there would be no victim to save.
 
iwire said:
of course in the example in the picture if the system was truly 'ungrounded' there would be no victim to save.
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Yelp Bob

But just don't have any underground branch circuits that might fault to ground. :D

Of course I hope everyone understands that this was a hypothetical situation we where talking about here as a floating residential service with no earth ground.
At the pole or anywhere. :)
 
iwire said:
So under very specific circumstances a an electrode would be needed for a GFCI to operate ........... of course in the example in the picture if the system was truly 'ungrounded' there would be no victim to save.
Click to expand...

Yes, the ground rod bonds the dirt to the electrical system. The GFCI functions because all of the conductive surfaces in the fault path complete a circuit. This is the same reason why GFCIs work on ships, airplanes, portable generators, and other non-dirted systems.
 
bobby ocampo said:
If neutral is not connected to ground it is ungrounded system.
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So are you saying that it is not possible to ground (bond to dirt) a system that does not have a neutral?
 
George Stolz said:
Bobby, you're a fairly recent addition to the forum, welcome.

Let's take your gut feeling to the extreme for the purposes of illustration:

Drive a ground rod, and energize a metal pole. In your mind, not physically.

touch.gif


This pole is grounded (connected to the earth).
It's currently in a fault - the housing is energized.
The man is dead.
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The illustration would tell us that the ground resistance of the soil is very high. This is the reason why ground resistance is measured. In substations where there is a big step potential problem more than one ground rod is installed depending on the resistivity of the soil.

In the illustration it can also be seen that at certain distance from the ground rod is zerp potential. This shows that if the person is standing in this area he will not receive electric shock despite the very high fault current brought about by the single line to ground fault. If a ground mat is installed and connected to this ground the person will not be electrocuted. Ground mats are used in switching poles for utilities for protection of personnel in utility companies. The examples also shows why in substation there are many ground rods installed and are interconnected with each other to reduce shock due to step potential for a very high fault current. In substations, and you are standing near it without this installed ground rods, you will still be electrocuted at the instant of the fault long before the OCPD trips.
George Stolz said:
Why?

Because the connection to earth is not good enough to bring the voltage down on the faulted piece of metal. The man is still dead.
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This illustration only shows that one ground rod is not enough in certain cases as a protection for personnel standing near a faulted system. In substation because of the possibility of step potential more than one ground rod is installed. This is the reason why ground resistance is measured to design the number of ground rods that must be installed for safety on step potential.
George Stolz said:
The connection of the rod to the soil is not good enough to raise the voltage of the soil to match the pole. The man is still dead.
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In this case it is not good enough because it is not enough. You may ask other members in this thread on how they do this in a substation where there is a much possiblitiy of a higher line-to-ground fault.
George Stolz said:
The only hope for the man is to get that circuit shut off before anyone has a chance to touch the pole. The only way to get that done is to bond the pole to the EGC, which is connected to the neutral at the service. The bonding connection (N-G) creates an intentional circuit path to overload the breaker and shut down the circuit.
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I agree that it is as important to have a bonded EGC to operate the OCPD. But not all single line-to-ground fault are bolted fault to ground. Most of the single-line-to-ground fault are only ARCING GROUND FAULT. This fault is most of the time lower that the ratings of the OCPD. What will then happen is the pole in the illustration even if it has bonded EGC will still be energized and person touching the pole will be electrocuted. At low fault current due to the ARCING GROUND FAULT, there is a minimal STEP POTENTIAL because of a very low voltage drop due to low ARCING GROUND FAULT current.
George Stolz said:
Why do we bother to earth the service, if the transformer is the main focus of our intentional circuiting, and guarding against ground faults?

To protect the equipment and the structure from arcing in the event of lightning or unintentional contact with high voltage lines.

This is the truth these guys have been trying to get across to you. If you think any of these truths is wrong, you need to stop and make sure your pride isn't standing in the way of your learning, it happens to us all from time to time.

Hope that helps,
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I am not saying that connection to ground is not a protection to lightning and untintentional to high voltage. Just like lightning it also protects people against the hazards of electric shock due to accidentally energized metal piece of equipment.

How do you prevent people from electric shock in an ARCING GROUND FAULT?

How do you prevent people from electric shock in an UNGROUNDED SYSTEM AND HRG SYSTEM where there is a very small single line to ground fault current if the energized metal is not connected to earth?
George Stolz said:
you need to stop and make sure your pride isn't standing in the way of your learning, it happens to us all from time to time.
Click to expand...

This applies to the rest of us let us discuss this objectively.
 
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