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Shorting neutral to earth confusion

by ElectroPhysics
Tags: confusion, earth, neutral, shorting
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ElectroPhysics
#1
Mar9-12, 09:44 AM
P: 113
what will happen if i short neutral ac outlet wire with earth? please see the figure if you have any confusion.
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SHORTING EARTH TO N.JPG  
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davenn
#2
Mar9-12, 07:05 PM
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neutral and earth are usually connected at the house entry buss board anyway

Dave
OldEngr63
#3
Mar15-12, 06:12 PM
P: 343
The answer is nothing, provided that everything was properly wired and that the power source generator was grounded. This covers most cases, but certainly not all of them.

With a Y-connected generator, it is easy to ground the center of the generator, and it is common practice to do so. With a delta-connected generator, there is no center point, and consequently such systems often have not grounded neutral (the happens in the US Navy in places).

If in doubt, measure the potential between the two wires before you short them.

nsaspook
#4
Mar15-12, 08:01 PM
P: 594
Shorting neutral to earth confusion

With a ground to neutral connection at more than one place (at the main power panel) on a normal house AC system the risk of the ground connection becoming a current carrying connection increases. The voltage difference between ground and neutral might be several volts at a distant power plug on a circuit that draws significant current (due to voltage drops from line resistance). If the connection is made at the distant device a GFCI device will trip due the unsafe condition if you are lucky. High currents passing in grounding circuits can be dangerous because they are designed to handle fault currents that only last a short time and are not normally current carrying conductors.

http://en.wikipedia.org/wiki/Residual-current_device
NascentOxygen
#5
Mar25-12, 09:09 AM
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Sometimes neutral and active get swapped around, accidently, as can happen when someone makes up their own extension cord, or replaces a broken plug, etc., and in the process gets the wiring reversed through carelessness. Many appliances [seem to] operate satisfactorily despite this, though they can be an electrical hazard to the user.

You can picture the scene were you to unknowingly connect the lead marked "neutral" to ground in the event of it being one of those botched wiring jobs.
philrainey
#6
Aug3-13, 03:00 AM
P: 89
there is a concern it that if there is a bad connection (Break) in the Neutral somewhere the Neutral would become live creating a short circuit (hopefully blowing the fuse )
Averagesupernova
#7
Aug10-13, 10:22 AM
P: 2,499
Quote Quote by philrainey View Post
there is a concern it that if there is a bad connection (Break) in the Neutral somewhere the Neutral would become live creating a short circuit (hopefully blowing the fuse )
How do you figure? Where did you come up with this misinformation?
SteamKing
#8
Aug10-13, 02:42 PM
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It's like grounding a ground wire.
Baluncore
#9
Aug11-13, 04:28 AM
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A “Multiply Earthed Neutral” MEN system is often used to distribute three phase power. The local transformer has a star (or Y) wound secondary. The centre connection is called neutral and is earthed at the transformer, and usually at every second pole. So it takes 4 wires to supply customers in one street. Single phase power is provided to a customer as a two wire line. One is neutral, the other is active. When they enter the customers meter/fuse box they meet the customers buried earth line which gives the three wires available at outlet sockets. There is only one connection (it is in the fusebox) where the earth is joined to the neutral. At no other point should they connect.

Earth leakage detection, AKA residual current detection, compares the current flowing in the neutral and active wires. It does that by winding them together on a magnetic core. Their currents should be equal and opposite so there should be no magnetic field in the core. If a magnetic field is detected then the circuit is quickly broken automatically.

Any current that returns through the earth rather than the neutral will trip the system because the neutral and active currents are no longer equal and opposite. That will happen if you connect an earth to a neutral on a circuit that is drawing current since part of that current will flow through the earth wire. If no current is being drawn while the earth to neutral connection is made it will not trip.

For a street with several single phase customers, each will have their own grounded earth and a common neutral for the street. But their active will be taken alternately from the three phases available. That will tend to balance the load on the phases in the street. So your two neighbours will have a different active phase. Your neighbours neutral, active and earth are all different to yours so they cannot be paralleled.
philrainey
#10
Aug14-13, 05:06 AM
P: 89
Where I live we have a multiple earth neutral electricity system. With that if you short the neutral to earth some of the current will return to the Neutral through the earth ( through the earth wire attached to the appliance and then through the link between the neutral and earth bus bars in the switch board ) so that if there is a RCD on the circuit it will trip as the current in the Neutral and phrase will not be balanced. If there is no RCD and no other faults it will keep operating with some of the current returning through the Neutral and some through the earth wire. There are differing electricity supply systems , I don't know about where you live.
philrainey
#11
Aug14-13, 05:22 AM
P: 89
Quote Quote by Averagesupernova View Post
How do you figure? Where did you come up with this misinformation?
Yeah you are right I'm wrong , for the case of the appliance to become live there would have to be both a bad earth and Neutral and it wouldn't blow any fuse.
Evo
#12
Aug15-13, 12:11 AM
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Stop me if I am wrong here. But in English the term is GROUND not Earth. I remember years ago my Toyota car manual said to EARTH one end of a connection. They meant GROUND one end.

I think we should be correcting these errors if they are born originally from translation errors.

I look at this

Quote:
Originally Posted by subtech View Post
I've no comments just yet, but earth, ground, and common are about the three most misunderstood words in all of the electrical world.
This discussion should be an eye opener.
I feel the same. That's the main reason why I opened this topic.
http://forum.allaboutcircuits.com/showthread.php?t=6050

and http://wiki.answers.com/Q/What_is_th...rth_and_ground

http://ecmweb.com/nec/grounding-bonding-definitions

My dad was an ee, and he never taught me to use earth instead of ground. (he's been dead for over thirty years, so I can't ask him) Is this just an acceptance of the misuse of the translation, or is this something that just wasn't in common use 45 years ago, that has a different meaning now, (earth doesn't mean ground)?

I find it confusing. Please help me out here. Is it correctly grounding, or is earthing something different from grounding now? And if it is different, what is the difference?

I'm beginning to think this stems first from bad translation then becomes literal... Any old folk out there that know what I am saying? I know my dad's old books never said earth, I read them all, he made me do all of the exercises.

Thanks!

well, lost all of what i just posted thasnks to chrome crashing again.

Anyway.

Difference in Terminology:
In USA term Grounding is used but in UK term Earthing is used.
So it is the result of an old translation error.

http://electricalnotes.wordpress.com...-and-earthing/
Baluncore
#13
Aug15-13, 03:05 AM
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Quote Quote by Evo
But in English the term is GROUND not Earth. I remember years ago my Toyota car manual said to EARTH one end of a connection. They meant GROUND one end.
What Toyota really meant was “connect it to the chassis”.

I have always interpreted the meaning of Ground and Earth as being synonyms.
My guess is that the terms arose about 100 years ago when radio (or wireless) used long wavelengths (or Low Band). At those wavelengths a dipole was not possible, so the local Earth (or ground) had to be used with the aerial (or antenna).
dlgoff
#14
Aug15-13, 03:44 AM
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Ground is ground. It's a question of "what" ground. Here are the symbols:



from http://www.rapidtables.com/electric/...ound%20symbols
russ_watters
#15
Aug15-13, 05:48 AM
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Quote Quote by Evo View Post
Stop me if I am wrong here. But in English the term is GROUND not Earth. I remember years ago my Toyota car manual said to EARTH one end of a connection. They meant GROUND one end.
Yes, but I believe in Britishese, the term is "earth".
Evo
#16
Aug15-13, 04:56 PM
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Quote Quote by Baluncore View Post
What Toyota really meant was “connect it to the chassis”.
Yes, that was the case.


Quote Quote by dlgoff View Post
Ground is ground. It's a question of "what" ground. Here are the symbols:
Thanks!

Quote Quote by russ_watters View Post
Yes, but I believe in Britishese, the term is "earth".
Yes, and they call cookies "biscuits" and french fries are "chips".

Thanks all of you, I was wondering if terminology had changed or if it was just that 40 years ago I was only exposed to American books and with the internet, terminology became mixed, it seems the latter is responsible for a lot of the mixed terminology I see now. This is what happens when you stop learning and then pick up after 40 years.


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