All About Circuits Forum what is the difference between neutral and ground ??
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#1
09-16-2008, 03:35 PM
 gauravalwaysyours New Member Join Date: Sep 2008 Posts: 1
what is the difference between neutral and ground ??

please tell me the difference between the two
#2
09-16-2008, 03:40 PM
 scubasteve_911 Senior Member Join Date: Dec 2007 Posts: 1,202

It can be stated that Neutral can be grounded, but Ground is not neutral.

A Neutral represents a reference point within an electrical distribution system. Conductors connected to this reference point (Neutral) should, normally, be non current carrying conductors, sized to handle momentary faults (short circuits) occurring in electrical equipment. However, with the introduction of non linear loads, such as computers, electronic lighting, TVs, VCRs and other switchmode power conversion equipment, the requirements for the neutral conductor has changed (increased).

A Ground represents an electrical path, normally designed to carry fault current when a insulation breakdown occurs within electrical equipment. (Note: Breakdowns can be forced by connecting (dropping) a metal tool or conductive material from a voltage potential to the steel structure within a facility.) Connections to the electrical path (Ground) are made convenient for the installation of electrical equipment. Some current will always flow through the ground path. This current will come from a number of normal sources. Capacitive coupling and Inductive coupling between power conductors and the ground path (conductive conduit, conductive structure members, etc) are the greatest sources of ground path current.

Source: http://www.ab.com/drives/techpapers/rfignds.htm

also http://en.wikipedia.org/wiki/Neutral_wire is good
#3
09-17-2008, 12:59 AM
 SgtWookie Expert Member Join Date: Jul 2007 Location: In the vast midwest of the USA; CST Posts: 22,038

Scubasteve,
I have exceptions with your post.

In a "normal" AC service, the neutral provides the return path for current on the 120v sides, and has no function for 240v appliances.

"Ground" should never have any current on it. If there is more than a few mA current on a "ground" wire, there is a problem.

The purpose of the Neutral wire is a power return path.

The purpose of the Ground wire is for operator safety.

At the electrical service panel, Neutral and Ground are connected together. This must be the only place that they meet, or the premise of human safety is violated.

No, I'm not an electrician. However, this is a very important issue. I hope that someone who IS a licensed electrician will respond to this thread, and confirm or correct my assertion.
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#4
09-17-2008, 02:51 AM
 scubasteve_911 Senior Member Join Date: Dec 2007 Posts: 1,202

Well, I actually just copied and pasted from that website to make it easy, which I stated the source. I'm glad I am not under the Wookie-glass !

Steve
#5
09-17-2008, 04:16 AM
 thingmaker3 Super Moderator Join Date: May 2005 Location: Rural, Oregon GMT -8 Posts: 5,072 Blog Entries: 6

I'm licensed in Oregon and Washington and am a member of IBEW Local 48.

The notion of neutral and ground is indeed a confusing one, primarily because of unfortunate terminology.

First, a word to all those who oppose the phrase "current flow:" Buzz off! I am not going to further complicate this SAFETY issue with the phrase "charge flow." The terms "current" and "charge flow" and "current flow" all mean the same thing. If you don't like it, stop reading NOW.

"Current carrying" does not mean the same thing as "conducting." "Current carrying" is more like "hot" or "switched hot" or "traveler." Current does absolutely flow through the neutral, even though the neutral is not a "current carrying" conductor.

Under normal conditions, no current flows through the ground wire. Under certain fault conditions, current does flow through the ground wire - instead of where we don't want it.

The neutral is the grounded conductor, whereas the ground is the grounding conductor.
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#6
09-17-2008, 04:22 PM
 muni Junior Member Join Date: Jul 2008 Location: hyderabad (india) Posts: 45

sir i could understand sgt wookies' and scubasteve's thread. it is very interesting and thanks for the information. but thingmaker sir thread is really some thing vague
#7
09-17-2008, 05:19 PM
 studiot E-book Developer Join Date: Nov 2007 Location: Somerset UK Posts: 4,014

Depends where in the world you are.

Most mains AC electrical supply these days is three phase to the local substation. This may be a transformer on a pole near you supplying overhead cables or a transformer in a compound, with underground cables.

Three phase means that the are effectively three elctricity supplies on three separate cables.
As you know, with AC the voltage varies periodically, rising and falling with time.
The three phases are carefully controlled so that when one is rising another is falling.

On any individual phase once the current has passed through your load it is returned by your neutral connection to the substation.

Here the magic occurs, because the rises and falls in the different phases are at different times they nearly cancel each other out, leaving only a small imbalance current.

This is fed to earth at the substation.

Your neutral should not be earthed at your local distribution board as this nullifies the whole cleverness of the scheme and throws the phases into imbalance.

Steve and Wookie.

The average voltage between the phase conductor and the neutral is 230 volts standard in Europe and 120 volts standard in North America.

The voltage between any two phases is 240 volts in North America and 415 volts in Europe. So beware of suggesting that the neutral at 240 volts has no function.

The clever part of balancing the return current of one phase against another is that it substantially reduces the cabling requirement for electricity distribution.
Two common schemes are for one phase to feed alternate houses or one side of a street and another phase to feed the remainder. The third phase is used for street lighting etc.
On average the currents and thus the return currents will be very similar in each phase.

Heavy duty (industrial) equipment receives the extra oomph provided by all three phases.
#8
09-18-2008, 12:56 PM
 Metalfan1185 Senior Member Join Date: Sep 2008 Posts: 129

interesting...
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#9
09-18-2008, 01:35 PM
 thingmaker3 Super Moderator Join Date: May 2005 Location: Rural, Oregon GMT -8 Posts: 5,072 Blog Entries: 6

Quote:
 Originally Posted by studiot The average voltage between the phase conductor and the neutral is 230 volts standard in Europe and 120 volts standard in North America. The voltage between any two phases is 240 volts in North America and 415 volts in Europe. So beware of suggesting that the neutral at 240 volts has no function.
I'm not conversant with European power distribution, but American residential power is split single phase, not three phase. That's 240 between the hot leads and 120 from either hot lead to ground. American residential hot leads have current 180 degrees apart, not 120 degrees as is found in 3-phase.
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"I want to establish in your mind very clearly that you must not think I deny all that I do not admit. On the contrary, I think there are many things which may be true, and which I shall receive as such hereafter, though I do not as yet receive them; but that is not because there is any proof to the contrary, but that the proof in the affirmative is not yet sufficient for me"
#10
09-18-2008, 09:36 PM
 studiot E-book Developer Join Date: Nov 2007 Location: Somerset UK Posts: 4,014

I do believe that the US has many local generating sets, especially in rural areas.
These can be of all sorts of types.

This situation is also typical in many other parts of the globe especially where population density is low.

In the UK we have centralised power stations and a distribution grid. I think they use 3 phase also because 3 is the smallest number you can connect in star - delta formation. You cannot do this with two phase systems. However the principal of load balancing on polyphase systems still holds good.

 Tags difference, ground, neutral

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