Neutral Connection in a System Grounding

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nakulak said:
imo the importance of earthing the neutral is to provide the utility with a return path in the event of a bolted fault before the main.
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What do you mean by a bolted fault? Is it line-to-line fault? Is line to ground fault a bolted fault for you?

nakulak said:
(of course, if the utility wasn't so cheap, providing a separate grounding conductor would alleviate using the earth and probably save lives as well, since the earth path is not so hot)
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What do you mean if earth is not so hot?
 
bobby ocampo said:
Why is it important in System Grounding?

What is the importance of grounding or connecting to earth of the neutral of the transformer? Or in premises wiring connecting and bonding the neutral and grounding in the service equipment?
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You missed my point. It can't be a solidly grounded system without a connection to a grounding electrode. If there is no connection then there is not a solidly grounded system. So from that point of view it is very important as with out the connection to earth the system does not exist. The major reasons for a connection to earth is for protection from accidental contact with higher voltage systems and from lightning.


Do you mean that it will only be important if voltage is above 600 volts?
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I am saying that the connection to earth provides more safety advantages on higher voltage systems, but only because of ohms law. The relatively high impedance of the earth ground can flow enough current to cause the OCPDs to open on higher voltage systems, something that an earth connection can rarely do on systems below 600 volts.
 
bobby ocampo said:
Never did I say that neutral is not allowed to be bonded. However in an Ungrounded system where there is no neutral conductor the bonded EGC is connected to the metal case of the transformer then connected to earth through a grounding rod.

Neutral if connected to earth is solidly grounded. If neutral is not connected to earth then the system is considered ungrounded. If the neutral is connected through a resistor then the system is considered impedance grounded.
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So why the question about a multi-pole breaker and a "neutral" conductor?

Roger
 
roger said:
So why the question about a multi-pole breaker and a "neutral" conductor?

Roger
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The use of the single pole is when one of the current carry conductor (neutral is grounded or connected to earth) If neutral is not grounded then 2pole circuit breaker should be used. Article 240 of NEC
 
don_resqcapt19 said:
You missed my point. It can't be a solidly grounded system without a connection to a grounding electrode. If there is no connection then there is not a solidly grounded system. So from that point of view it is very important as with out the connection to earth the system does not exist. The major reasons for a connection to earth is for protection from accidental contact with higher voltage systems and from lightning.
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1.3 Purposes of System Grounding
System grounding, or the intentional connection of a phase or neutral conductor to earth, is for the purpose of controlling the voltage to earth, or ground, within predictable limits.

It also provides for a flow of current that will allow detection of an unwanted connection between system conductors and ground and which may instigate operation of automatic devices to remove the source of voltage from conductors with such undesired connections to ground.

The NEC [1], prescribes certain system grounding connections that must be made to be in compliance with the code. The control of voltage to ground limits the voltage stress on the insulation of conductors so that insulation performance can more readily be predicted.

The control of voltage also allows reduction of shock hazard to persons who might come in contact with live conductors.

don_resqcapt19 said:
I am saying that the connection to earth provides more safety advantages on higher voltage systems, but only because of ohms law. The relatively high impedance of the earth ground can flow enough current to cause the OCPDs to open on higher voltage systems, something that an earth connection can rarely do on systems below 600 volts.
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Even in higher voltage bonding is highly recommended not only in low voltage.
 
bobby ocampo said:
Both are important. It is still important to connect the bonded EGC to ground. Never will I say that bonding is not important. What I will always say is it is important to connect the bonded EGC to ground or earth.
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Yes, it's important to bond the neutral to earth for systems of 600 volts of less. Nobody is arguing against that point. What continues to fly over your head in these discussions is the PRACTICAL PURPOSE for bonding vs. earthing, and what purpose each of them serve (assume systems of 600 volts or less.)

In the case of a premises wiring system, the N-G main bonding jumper will facilitate the operation of the OCPD. The connection to the earth will not facilitate the operation of an OCPD, nor will it significantly reduce touch potential hazards.
 
peter d said:
The connection to the earth will not facilitate the operation of an OCPD, nor will it significantly reduce touch potential hazards.
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No, but GFCI's wouldn't work without the earthing of a supply conductor. Of course, one could argue that they wouldn't be necessary in that case.

But, knowing what I know about electricity, I'll take a grounded system every time (except for the benefits of ungrounded systems in inductry, etc.)
 
LarryFine said:
No, but GFCI's wouldn't work without the earthing of a supply conductor. ...
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Larry -
GFCIs will work fine with out a rod driven in the earth. GFICs will work fine with out even a connection to the receptacle grounding terminal.

This is not an original with me - there have been several good discussions.

carl
 
Other than lightning strikes, the only thing that I know of that a household ground rod does is give millions of free grounds to the utility.

Bonding will trip a breaker, grounding will not.

carl
 
Bobby 0 -
Please differentiate whether you are discussing
utility distribution or
industrial or
residential

The laws (codes) are different. Construction techniques are different. And the science is different.

Some of your discussion appears to be jumping between the three and it makes it hard to follow.

carl
 
bobby 0 -
Although I don't work residential (except my own), I can follow the science pretty well.

Tell me the science behind how a ground rod makes a residential system safer. For this discussion, consider all of the non-current carrying parts are bonded together and there is solid connection at only one point between the neutral and the equipment bonding conductor.

Leave the lightning out of it for now, we can deal with that when we get to NFPA 780.

PS: I'm not even particularly convinced this single point connection between neutral and ground does any good - but let's leave this discussion for later too.

carl
 
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coulter said:
bobby 0 -
Although I don't work residential (except my own), I can follow the science pretty well.

Tell me the science behind how a ground rod makes a residential system safer. For this discussion, consider all of the non-current carrying parts are bonded together and there is solid connection at only one point between the neutral and the equipment bonding conductor.
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Or beter yet can you tell me the science of why connecting the bonded EGC to ground will not make it safer?
 
coulter said:
Larry -
GFCIs will work fine with out a rod driven in the earth. GFICs will work fine with out even a connection to the receptacle grounding terminal.

This is not an original with me - there have been several good discussions.

carl
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I know that an EGC is not required for a GFCI to function, but the supply system must be grounded. Otherwise, there won't be any current for the GFCI to detect. (Well, maybe a few microamps, due to capacitive coupling, but not the needed 4-6ma.)
 
bobby ocampo said:
Or beter yet can you tell me the science of why connecting the bonded EGC to ground will not make it safer?
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What's a "bonded EGC"? Is this an Equipment Bonding Conductor that connects all of the non-current carrying metal parts together and has a single point connection to the neutral?

Cause if it is, I didn't say connecting a "bonded EGC" to a ground rod would make the system less safe. I don't think anyone else has either. I said it wouldn't help any.

PS: Are you still working on how this ground rod make the breadbox any safer?

carl
 
LarryFine said:
I know that an EGC is not required for a GFCI to function, but the supply system must be grounded. Otherwise, there won't be any current for the GFCI to detect. (Well, maybe a few microamps, due to capacitive coupling, but not the needed 4-6ma.)
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You're right. There has to be a current differential for a GFCI to work I probably would have said "bonded" as opposed to grounded - as in the example of airplanes and ships. Still, close enough - I agree.

carl
 
bobby ocampo said:
The use of the single pole is when one of the current carry conductor (neutral is grounded or connected to earth)
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The use of a single pole breaker would be for a two wire circuit, and this would mean that there is no neutral but, there is indeed a grounded conductor.

bobby ocampo said:
If neutral is not grounded then 2pole circuit breaker should be used. Article 240 of NEC
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I think your terminology or understanding of the circuits is the problem. A neutral conductor can only be present in circuits where it would be common to more than one leg or phase (post #12 and #19) and it has to be grounded per the NEC. The other circuit conductors (ungrounded conductors) would have to be connected to a multi-pole breaker or breakers with handle ties.

See 210.4 and 210.7

Roger
 
coulter said:
bobby 0
This is a link to an excellent paper on grounding systems. It has a pretty good discussion on the TN-S systm used in the US.

http://www.schneider-electric.com/documents/technical-publications/en/shared/electrical-engineering/dependability-availability-safety/low-voltage-minus-1kv/ect173.pdf

There will be a test tomorrow to see if you read it:roll:

Or maybe this belongs on your other thread..

carl
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Dear Carl after reading found out that connection to earth is realy imporant as shown in the illustrations. In fact in one of the illustration shows that bonded EGC may not be a 100% proof that the OCPD will open. They are recommending RCD. Reason being is that during an arcing ground fault, current may be very low that it may not be detected by the OCPD despite the connection of bonded EGC. At this point the metal enclosure will be energized and should be reduced to ground potetial for the safety of personnel. The example in the illustration are solidly grounded system.

I also remember the provision that for 1000amps and above of more than 150volts to ground a ground fault protection shall be installed. Article 2.40. Objective for this ground fault protection is to sense low fault current brough about bay single line to ground fault. Importance of connecting to earth is to reduce the potential of the energized metal piece to ground potential for safety in a solidly grounded system.
 
bobby ocampo said:
Importance of connecting to earth is to reduce the potential of the energized metal piece to ground potential for safety in a solidly grounded system.
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You really have learned nothing from reading this thread, have you? :confused:
 
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