Neutral Connection in a System Grounding

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Bobby: You are consistently missing the point and you cannot adequate explain HOW the earth plays a part in clearing faults within a structure with distribution under 600 VAC.
 
bobby ocampo said:
NEC requires it to be connected to ground for the reason that it will reduce the potential of an accidentally energized metal piece to ground potential and therefore reduce electric shock hazard. Otherwise NEC would have removed it a long time ago.

Proof of this is is in a single line-to-ground fault in an ungrounded system or HRG SYSTEM.



Bonding without connection to the reference plane will still have a an electric shock hazard. This is the reason and the PHYSICS behind why NEC requires it to be connected to ground through a ground rod or other acceptable means in the NEC.
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What does ground/earth have to do with any reference point in my kitchen? Please draw the fault path for a line to bonded metal piece (say a toaster) to a human body to the wooden floor. Now draw a circuit of the same faulted metal to a human body to the bonded kitchen sink. Now try to draw a fault path that includes a path through the kitchen and ground/earth.

Inter-surface bonding including a connection to a reference plane (if one exists) is important for shock prevention, but there is no reason that the reference plane be earth/dirt except that the NEC says it must be.


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peter d said:
So again I ask, how do we accomplish this all important connection to earth in a ship or an airplane? The structure of a ship or plane and EGC's are bonded to the source neutral and never connect to dirt.
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The reference plane is the metal body of the ship or the plane. In land the reference plane is the earth.

If grounding and connection to earth is not important then NEC should have a long time ago removed this requirement.
 
bobby ocampo said:
If grounding and connection to earth is not important then NEC should have a long time ago removed this requirement.
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Then what would you do in regards to lightning and primary to secondary faults with in the utility transformers?

There are reasons for this connection to earth JUST not the horse you are beating to death.
 
brian john said:
Then what would you do in regards to lightning and primary to secondary faults with in the utility transformers?

There are reasons for this connection to earth JUST not the horse you are beating to death.
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Same reason why it is important to ground for static electricity. Same reason also for UNGRUNDED AND HIGH RESISTANCE GROUNDED.

Please give me the reason why this connection to ground is required in the NEC.
 
brian john said:
Bobby: You are consistently missing the point and you cannot adequate explain HOW the earth plays a part in clearing faults within a structure with distribution under 600 VAC.
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Connecting to earth is not for clearing the fault. Connecting to earth is to reduce electric shock by reducing the potential of the energized metal piece to ground potential. In an ungrounded system the OCPD will not clear the fault in a single line-to-ground fault to have continuity of service. Industrial Power System Handbook by Beeman. However Equipment grounding is important to reduce the potential of the accidentally energized metal piece to ground potential not clear the fault.
 
bobby ocampo said:
Please clarify what you mean by your question Sir.
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If you have one potential value within 1' of your grounding electrode will you have the exact same potential value at 6' from the same grounding electrode?
 
peter d said:
The structure of a ship or plane and EGC's are bonded to the source neutral and never connect to dirt.
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True, but then, when is the last time you were able to touch a hot electrical conductor on a ship or a boat while standing on earth?

By the way, aircraft do require grounding and bonding while fueling.
 
tryinghard said:
If you have one potential value within 1' of your grounding electrode will you have the exact same potential value at 6' from the same grounding electrode?
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Sorry Sir, Still don't get what you are driving at?
 
bobby ocampo said:
Sorry Sir, Still don't get what you are driving at?
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And I think this may hold true of your side of this discussion as well.

Roger
 
Connecting to earth is not for clearing the fault. Connecting to earth is to reduce electric shock by reducing the potential of the energized metal piece to ground potential. In an ungrounded system the OCPD will not clear the fault in a single line-to-ground fault to have continuity of service. Industrial Power System Handbook by Beeman. However Equipment grounding is important to reduce the potential of the accidentally energized metal piece to ground potential not clear the fault.
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Just as you said in an airplane it is the frame of the plane, in a building It is not the earth it is the structual steel, duct work, piping that is of importance. I could totally isolate the building from earth and and the system would work exactly the same

Connecting to earth is to reduce electric shock by reducing the potential of the energized metal piece to ground potential
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How does this work on the 26th floor of a high rise.
 
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tryinghard said:
Do you think potential is affected by resistance?
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bobby ocampo said:
Please clarify what you mean by your question Sir.
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tryinghard said:
If you have one potential value within 1' of your grounding electrode will you have the exact same potential value at 6' from the same grounding electrode?
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bobby ocampo said:
Sorry Sir, Still don't get what you are driving at?
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I?m really not driving I?m asking you a poignant question.

Do you think if you stand on earth 1? from your grounding electrode and touch a non current carrying item that has dangerous touch voltage on it from a short that you will receive the same shock if you?re standing 6? from the grounding electrode? Is your resistance exactly the same at 6? or more as 1? from your grounding electrode? Do you believe earth has the same resistance everywhere?
 
brian john said:
I could totally isolate the building from earth and and the system would work exactly the same.
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With the exception that GFCI's would neither function nor be necessary to protect someone standing on the earth while contacting a hot wire.
 
LarryFine said:
With the exception that GFCI's would neither function nor be necessary to protect someone standing on the earth while contacting a hot wire.
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Larry, GFCIs do not need a ground reference to function. If there is not a complete circuit then current will not flow and the GFCI will not trip, but it is not because there is no dirt. GFCIs function just fine in my wooden floor kitchen or on the 25th floor of a high rise, neither of which have dirt in their fault path.
 
jim dungar said:
Larry, GFCIs do not need a ground reference to function. If there is not a complete circuit then current will not flow and the GFCI will not trip, but it is not because there is no dirt. GFCIs function just fine in my wooden floor kitchen or on the 25th floor of a high rise, neither of which have dirt in their fault path.
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It doesn't have to be 'dirt' per se, but there has to be a connection between one circuit conductor and whatever coductive surface (i.e., the aforementioned 'ground plane') one might contact while making accidental contact with the other (i.e., the 'hot') circuit conductor.

A GFCI only works if it's connected to a supply with a grounded conductor. By grounded, I mean whatever surface one might be in contact with when the accidental touch occurs. In a non-grounded supply, there's no electrocution hazard for the same reason the first ground fault doesn't trip a breaker.

I'm making no reference to the circuit EGC, but it's the grounding electrode system connected between the earth, concrete, metal floor, airplane body, etc., and the supply's grounded conductor that allows current to flow through a person's body.

In other words, yes, GFCI's do need a ground reference in the sense that the 'ground' must be part of the circuit included in the shocking-current pathway. Your kitchen floor, if dry, is not conductive enough for accidental contact with a hot wire to trip a GFCI.

But, if your supply was non-grounded, then stepping barefooted on a wet concrete floor slab on grade, or even a well-grounded metal floor, would not electrocute you during contact with a hot wire. There must be a pathway to one conductor for contact with another to be hazardous.

Unless you're touching a system's neutral, contact with a system's hot does not create a closed circuit through your body. Current will not enter your body unless it has a pathway through you back to the source. You won't get a shock, and a GFCI will not trip, without such a pathway.

To protect you against electrocution when standing on earth, the system requires an earth connection. To protect you while in contact with supposedly-bonded metallic surfaces, they system must have a connection to those surfaces. It doesn't have to be earth.

It does, however, have to be whatever you're in contact with during the accidental contact with an energized part. It's handy and convenient to use the earth, because so much of our environment is, or is bonded to, the earth. What creates the hazard also provides the means for the protection to work.
 
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