What's the purpose of earth ground?

I am trying to understand the purpose for earth ground. Imagine a world where the power company never attached the neutral conductor to ground, anywhere, not at the generation source, not along the transmission route and not at the destination. The neutral would be isolated from the earth, the same as the hot conductors are now. In that world, if either a neutral, or hot conductor were to come in contact with a metal equipment case and a person were standing in water with bare feet and touched it, they would not get shocked would they, since there would be no path back to either the neutral or hot side through the earth? How is earthing the neutral making things safer? Seems like we would have been better off if they never would have done it.

Earth ground

Oh god.

In such a world, we would all be dead.

Re: Earth ground

You really miss the point of ground, do you?

Why they prvide a neutral line?

Why touching a bare cable with 220V, 110V, 5kV etc will cause electricution to you?

It is simple electronic Physics: Different potentials denote a voltage difference. Now, the only way not to be electrified is for you to stand on an equal potential "ground" . If you are standing on 220V and you touch 220V cable nothng happens as no voltage difference is there to make electrons to move from higher to lower potential.

The use of the ground path from the electical company to the consumption is for your "system" ( house, office, factory) to be provided with the ground that is used to name the voltage. Giving 220V means with respect to the line that has the neutral.

I.E. the power distribution cabinets in the houses, sometimes use the neutral line and a ground line that goes to the wall in order to give the local ground as well. Sometimes though you can measure a small leackage voltage on the ground ( 20-30 V). That means that your real voltage if you line the house with this ground it will be 220V-30V!

I hope now it is more clear. On the other hand, if there is a more profound explanation I will be glad to hear it!

D.

Re: Earth ground

Neutral ground is for providing the return path to the line current while earth ground is provided for safety to shock hazards.

Earth ground

Don't forget capacity of all your system against ground! If the system (and capacity) is large enough, the capacity current would kil you anyway.

Re: Earth ground

iamsand,
Consider the following situation, which applies to the US. I'm not familiar with Euorpean or Asian standards:
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The neutral opens up due to failure, accident, etc. You have an unbalanced load on the 220V lines (one of the 110 v "phases", call it side "A" has a heavier load than the other "phase", call it side "B". because of the unbalanced load, anything connected to the lightly loaded side, wiil see a voltage much higher than 110V. The Earth ground provides an alternate pathe for what would normally be the neutral current, preventing the severe voltage unbalance due to the unbalanced load.
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The Earth ground also provides an alternate neutral path, so that safety devices such as GFCIs (Ground Fault Current Interrupters) can perform properly.
Regards,
Kral

Re: Earth ground

I thank those who have attempted to clarify this for me so far. I am still a bit confused however. Let's take this answer as an example:

"It is simple electronic Physics: Different potentials denote a voltage difference. Now, the only way not to be electrified is for you to stand on an equal potential "ground" . If you are standing on 220V and you touch 220V cable nothng happens as no voltage difference is there to make electrons to move from higher to lower potential."

In my original scenario I suggested that the power company had never connected the neutral conductor to the earth, anywhere. Why therefore, would there be a difference in potential between the live conductor and earth in that case?

Or this answer:
"The neutral opens up due to failure, accident, etc. You have an unbalanced load on the 220V lines (one of the 110 v "phases", call it side "A" has a heavier load than the other "phase", call it side "B". because of the unbalanced load, anything connected to the lightly loaded side, wiil see a voltage much higher than 110V. The Earth ground provides an alternate pathe for what would normally be the neutral current, preventing the severe voltage unbalance due to the unbalanced load."

Here again, it is stated that the Earth ground provides a path. My question is what would happen if the power company did not use the earth at all. How then would the "earth" get involved in a return path? If I touched both a live conductor and the earth in that case, how would it be any different than when I now touch a live conductor and I have good insulated shoes on? In both cases there would be no path back to another live conductor.

This is why I am wondering where the safety advantage is when the power company connects the neutral to the earth. It kind of seems like the fact that it does provide a path back to the neutral conductor puts me in more potential danger than if it didn't.

I am very grateful for the attempts so far to educate me on this and appreciate all the answers very much.

Re: Earth ground

In my original scenario I suggested that the power company had never connected the neutral conductor to the earth, anywhere. Why therefore, would there be a difference in potential between the live conductor and earth in that case?

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i think the question is not correct....the neutral conductor is never connected to the earth, its the return path of the completed electric circuit which terminates at the generating coil.
Ground earth is a separate mechanism to provide an low resistance path for the unbalanced or leakage current in the circuit. In implementation its the copper plates embedded deep in the ground

Sidd

Earth ground

earth ground is the returning current path

Re: Earth ground

yes in electronic circuits its ground thats return path but in power where there is +ve, -ve and earth or High, low and earth

Re: Earth ground

Ok, now I get the whole picture. Sorry for the confusion.
I wil agree with all the above collegues, the "Earth Path": is the return path for the complete circuit, but it happens to be in 0 potential. This is why you can make it similar to real ground.

I will come with some drawing as soon as I locate them in my library. For the time being I think a review on the house main power panel will convince everyone for that. There, two grounds exist. One is the return path, and second is the real ground ( connected to the wall or the floor or whereever!) Grey for return, yellow - green for real ground is in Greece.

D.

Earth ground

ground basically for shock protection.I dont understand what u want?

Re: Earth ground

[/quote]ground basically for shock protection.I dont understand what u want?

Shock protection is facilitatd if in an electric appliance there is any leakage current then it will be dangerous to touch it but if there is an earth terminal connected to the body of the appliance, the leakage current will be returned to ground thus provide safety to the user.

Sidd

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Re: Earth ground

ricksidd said:

In my original scenario I suggested that the power company had never connected the neutral conductor to the earth, anywhere. Why therefore, would there be a difference in potential between the live conductor and earth in that case?

Click to expand...

i think the question is not correct....the neutral conductor is never connected to the earth, its the return path of the completed electric circuit which terminates at the generating coil.
Ground earth is a separate mechanism to provide an low resistance path for the unbalanced or leakage current in the circuit. In implementation its the copper plates embedded deep in the ground

Sidd

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You're partially right. However, 'earth' ground sooner or later is connected to the neutral, usually in your main electrical panel. Check for the thick copper braided wire...

Last summer I had to upgrade the power in my workshop from 2-wire (hot/neutral) to 3-wire (hot/neutral/ground) in order to use power tools. I slammed a 6-feet copper rod into the ground which does the trick.

Re: Earth ground

I slammed a 6-feet copper rod into the ground which does the trick.

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As I said earlier, it is the copper plate/plates which are required to be embedded in the ground. Due to a larger surface area of plates the impedance will be ~ Zero (very Low). You can actuallully measure it. If you are using copper rod that is not going to serve the purpose as the impedance craeted will no be ~ Zero. Moreover, sometimes we have to go for more than one plates conneccted parallelly.
2. At no point in the circuitry, there is any connection between Neutral and Earth.

Sidd

Re: Earth ground

Hi everybody !!!
In my mind, the 'ground' or neutral or Vee is the return path, and the ground earth is a mean to fix the potential.
If you don't connect to ground, you will have floating potential.
The potential come from capacity and electron charge. If the charge or the capacity is important, the potential could go up to kV and there could be electrostatic discharge (never had wear a wool pullover and plastic shoes ???)
Electronic devices are very sensitive to electrostatic discharge (latch up : the diode to the substrat start to conduct).
24 mA could kill a human, and the human body resistance (when there is conduction) is only 1 kOhm in humid environnement, so 24V of difference in potential could kill someone. (This is one reason why car constructor are reluctant to rise the electric potential : isolation class )
The only solution to electrostatic discharge is to fix the potential to a common reference : the earth.
Moreover, most of the protection device use differential measure. If the return path is isolated from earth, the protection doesn't work if there is a isolation default (live conductor touching the shielding, but no current flow because of no return path). And you will be very surprise if you touch the shielding...
if the shielding is connected to earth, and the neutral is connected to earth, an isolation default will lead to a current flow which will active the protection.

Added after 6 minutes:

Another point :

It is a pratical point : It is 2 protection scheme :
Either you are isolated, but EVERYTHING has to be isolated.
Either you are connected to ground, but at least ONE point has to be connected to ground.

It is easier to make a connection in at least one point than to be sure there is no connection everywhere.

Re: Earth ground

The explaination has to be premised on whether we are talking about AC or DC circuits....

Earth ground

the Earth ground provides a path

Re: Earth ground

Yes, the path is from higher potential to lower potential...

The PSTN (Public Telephone) Line Potential is kept at -45V so that the earth potential at higher level and there is no leakage for the the buried copper cable...

Re: Earth ground

Let me try to explain the terms from a text extract :

It is important to realize that there are several purposes of a ground system. The
concept of a ground as being a zero-potential surface may be appropriate at dc or
low frequencies, but is never true at higher frequencies, since conductors have significant impedance (inductance) and high-frequency currents flow through these
impedances, resulting in points on the ground having different high-frequency
potentials.
This highlights the distinction between the two types of ground:
safety ground and signal ground.
1. Safety Ground:
Commercial power is utilized as 120 V, 60 Hz voltage in the United States (240 V, 50 Hz in Europe). A safety ground is normally required in order to provide protection against shock hazard. This safety ground is generally called “chassis ground.” In addition to shock protection, it also serves an important role in draining electrostatic discharge (ESD) charge.
2 Signal Ground:
The other type of ground is the signal ground along which the signal currents return
to their source. So we should think of signal ground as the return path for signal
currents and not as an equipotential conductor surface (which it is not). It is important to emphasize that although it may be the designer’s intent for the signals to return to their source through these designated paths, there is no guarantee that this will occur! In fact, some frequency components of that same signal may return through one path, while other frequency components of that same signal may return through another path. A shielded cable above a ground plane is a good example. The frequency components that are below the cutoff frequency of the shield–ground plane circuit will return along the ground plane, but those above this cutoff frequency will return along the shield and not the ground plane

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I hope this will not confuse further...
-Sidd