Tools are Grounded to Send the surge of electricty to earth

[Sahib]

As for a standard ocpd on short runs, adding a rod is on it's face pointless and useless- still a poor path back to source and breaker won't trip. And remember that the dangerous current doesn't disappear down the rod and the breaker still has to trip to eliminate the hazard.

If the touch voltage is,say 70V, clearing time of OCPD is, say 1 second, there is a risk of electrocution. The operating time of the OCPD could be reduced to safe level either by increasing the size of the phase conductor, provided it is feasible, by providing GFCI, provided it does not trip by existing leakage currents, or by reducing the ground resistance which the code does not permit. So which alternative you propose?

Gfci doesn't need any help to do anything (as if a rod would help it anyway)- the amount of current it trips on is considered harmless to most everybody.

A ground connection is helpful: it does not then require a person to be put in the path of electricity to operate the GFCI.

 

[user 100]

If the touch voltage is,say 70V, clearing time of OCPD is, say 1 second, there is a risk of electrocution...... or by reducing ground resistance which the code does not permit...

A ground connection is helpful: it does not then require a person to be put in the path of electricity to operate the GFCI.

So you still believe the rod is beneficial even though it wont trip the brkr, or even speed up operation and and despite the fact the ckt (including the added electrode) would still be live and present a shock hazard in the absence or failure of the egc?:roll: And in light of the fact of everything that has been explained thoroughly by several members?

Explain where this 70v would come from exactly.

Lets do a hypothetical about your rod vs. egc:

Lets be generous and assume the resistance between the rod and source is low, say 15 ohms., and lets assume the ckt connected to the rod is your avg 120v ckt, so 120v/15= 8 amps of fault current, not enough to trip a 15 amp breaker. Breaker stays closed, shock continues/ person is electrocuted.

Now lets do the egc, which is connected to the svc neutral (which is connected directly to the source) in the panel. Svc neutral often has an ohm or less of resistance, so:

120v/1 ohm= 120 amps of fault current. 15 amp brkr opens instantly, eliminating the danger, lives are saved.

Still believe the stuff about a rod helping now?

I'm going to totally ignore the gfci claim as well as the conductor size question, as that has been answered.

Maybe we should get you back to basics. Do you know the difference between bonding and grounding, why they are different and what the intent of each one is?

I don't think you do, and it is causing you to make assumptions that are incorrect.

Do you post questions and make suggestions here to learn and improve yourself, or do you do it to try to make the rest of us look like we are not familiar with our work?

If you really want to learn, all of us have the sincere desire to help you in any way we can. If you are just trying to be argumentative, you are in the wrong place to do that, especially when it comes to safety issues.

^^^^^^^^^^^^^
Starting to agree w/ this.........

 

[Sahib]

So you still believe the rod is beneficial even though it wont trip the brkr, or even speed up operation and and despite the fact the ckt (including the added electrode) would still be live and present a shock hazard in the absence or failure of the egc?:roll: And in light of the fact of everything that has been explained thoroughly by several members?Explain where this 70v would come from exactly. Lets do a hypothetical about your rod vs. egc:Lets be generous and assume the resistance between the rod and source is low, say 15 ohms., and lets assume the ckt connected to the rod is your avg 120v ckt, so 120v/15= 8 amps of fault current, not enough to trip a 15 amp breaker. Breaker stays closed, shock continues/ person is electrocuted.Now lets do the egc, which is connected to the svc neutral (which is connected directly to the source) in the panel. Svc neutral often has an ohm or less of resistance, so:120v/1 ohm= 120 amps of fault current. 15 amp brkr opens instantly, eliminating the danger, lives are saved.Still believe the stuff about a rod helping now?I'm going to totally ignore the gfci claim as well as the conductor size question, as that has been answered.

The code has banned use of ground for fault clearing. Yet there may exist power systems whose safety depends on it despite having intact EGC.Touch voltage 70V may come from voltage division between phase and neutral during ground fault with EGC functional for duration OCPD operation.

^^^^^^^^^^^^^Starting to agree w/ this.........

That is stupid.

 

[electrofelon]

The code has banned use of ground for fault clearing. Yet there may exist power systems whose safety depends on it despite having intact EGC.Touch voltage 70V may come from voltage division between phase and neutral during ground fault with EGC functional for duration OCPD operation.

Can you give a specific example of how a ground rod would result in significant less touch potential? The problem is the resistance of earth (dirt, comcrete, etc) is too high to equalize the potential between the earth and the faulted metal part. One would nearly literally have to be standing right on the electrode.

 

[user 100]

The code has banned use of ground for fault clearing. Yet there may exist power systems whose safety depends on it despite having intact EGC.Touch voltage 70V may come from voltage division between phase and neutral during ground fault with EGC functional for duration OCPD operation. That is stupid.

The point we are trying to get across is that the rod will be of zero benefit when there is a fault- forget about "voltage division" and that other stuff,- it doesn't matter in this case as you are concerned solely about the breaker opening when there is a fault .

And I'm going to say it again, the earth doesn't absorb electrons and/ or help (as said above, you would have to be standing on the electrode for it to maybe be effective- so does someone supposed to stand there on top of the rod, waiting for there to be a fault- kind of pointless when the equipment could just be bonded/gfci'd) with touch potential during a fault nor do rods don't make breakers open faster, and again if metal was bonded anyway, the brkr would have tripped and kept someone from being shocked in the first place.

And I'm ignoring the second part of your post as it adds nothing useful to the discussion.

 

[jim dungar]

Yet there may exist power systems whose safety depends on it despite having intact EGC.Touch voltage 70V may come from voltage division between phase and neutral during ground fault with EGC functional for duration OCPD operation.

You talk about hypothetical situations and then you change the parameters after someone provides a likely solution.

You should clearly stated the specific conditions you want evaluated. Show on your drawing where the 70V exists. Show the ground rod locations in the circuit. Provide the resistances.
You could even post your calculations. Prove us wrong, instead of just saying it.

 

[K8MHZ]

You talk about hypothetical situations and then you change the parameters after someone provides a likely solution.

You should clearly stated the specific conditions you want evaluated. Show on your drawing where the 70V exists. Show the ground rod locations in the circuit. Provide the resistances.
You could even post your calculations. Prove us wrong, instead of just saying it.

See post #62.

 

[K8MHZ]

And post #5.

 

[Sahib]

You talk about hypothetical situations and then you change the parameters after someone provides a likely solution.

First Iam here not to advocate any concepts but to inquire into them with you. In the light of it, this does not apply;

Prove us wrong,.

 

[jim dungar]

First Iam here not to advocate any concepts but to inquire into them with you.

Your actions contradict this statement.

 

[Sahib]

Back to the topic please.

Here is a drawing with one three phase source(4) and one three phase consumer(1). The neutral at source is grounded by artificial earth rod(2) with ground resistance Rart. The consumer equipment enclosure(1) is bonded to the neutral wire having resistance r0. When there is a phase to equipment enclosure(1) fault with auxiliary earth rod(2) with ground resistance Raux not connected to the equipment enclosure, the touch potential V0 for a fault current of Isc is given by V0=r0*Isc. But when the auxiliary earth rod(2) is connected to the equipment enclosure, the potential Vt is given by Vt= V0/2=r0*Isc/2, when Raux=Rart.

 

[don_resqcapt19]

The additional grounding electrode does not change the voltage on the equipment, as measured to remote earth, it only raises the voltage of the earth for a small area around the additional grounding electrode. There is a reduction in the touch voltage only if you are standing on or very close to the additional grounding electrode.

 

[kwired]

The additional grounding electrode does not change the voltage on the equipment, as measured to remote earth, it only raises the voltage of the earth for a small area around the additional grounding electrode. There is a reduction in the touch voltage only if you are standing on or very close to the additional grounding electrode.

And standing over or near the electrode without touching anything else can be dangerous when dealing with faults on systems of medium or high voltage ranges. Voltage gradient of the surface area between your feet can be at a dangerous level if your feet are too far apart. Below 1000 volts those zones are usually large enough to not be too much of an issue for humans especially if wearing shoes constructed of an insulating material.

Larger animals like horses, cattle, pigs - is why we have equipotential plane requirements in art 547. Those animals have a wide enough base between front and rear feet that they are more sensitive to low voltage gradients on the surface they are standing on then humans are, because their feet span across a higher voltage zone in such situations.

 

[Ultrafault]

Sahib your two formulas you typed are identical.
I think I can see the source of the misunderstanding here. Do you belive that if i had a power source that had no ocpd and then I hooked it to a earth grounded rod that it would not have any shock potential to ground? Do you belive it would have shock potential to the other phase of same source or the neutral?
Please anwser these questions.

 

[K8MHZ]

Sahib your two formulas you typed are identical.
I think I can see the source of the misunderstanding here. Do you belive that if i had a power source that had no ocpd and then I hooked it to a earth grounded rod that it would not have any shock potential to ground? Do you belive it would have shock potential to the other phase of same source or the neutral?
Please anwser these questions.

He is also negating the fact that the earth is a better insulator than a conductor and the resistance between the two rods would be 1000 or more ohms.

 

[electrofelon]

It is a common misconception that a ground rod will "hold" the potential of earth and a energized metal part to a low potential difference and thus result in increased safety. Iirc, even mike holt admits to falling for that one at one time.

 

[Sahib]

The additional grounding electrode does not change the voltage on the equipment, as measured to remote earth

Both Rart and Raux are resistances measured to remote earth. A ground fault current flowing through Rart should also flow through Raux to return to source via the grounded neutral. If Vt1 is the touch voltage at source side and Vt2, on the load side, V0 is the voltage drop along the neutral wire and Isc is the ground fault current, then

V0=Vt1+Vt2=(Isc*Rart)+(Isc*Raux)

The above equation holds not only during a ground fault but also during normal condition. To verify it, experiment with a small generator instead of POCO service for safety reasons. Ground the generator neutral and load neutral. Measure the ground resistances on each side. Load the generator and then measure the ground leakage currents in the GEC's. Also measure the voltage drop along the neutral wire. With the above data, the above equation may be verified.

Any one willing to do the above experiment?

 

[K8MHZ]

Both Rart and Raux are resistances measured to remote earth. A ground fault current flowing through Rart should also flow through Raux to return to source via the grounded neutral. If Vt1 is the touch voltage at source side and Vt2, on the load side, V0 is the voltage drop along the neutral wire and Isc is the ground fault current, then

V0=Vt1+Vt2=(Isc*Rart)+(Isc*Raux)

The above equation holds not only during a ground fault but also during normal condition. To verify it, experiment with a small generator instead of POCO service for safety reasons. Ground the generator neutral and load neutral. Measure the ground resistances on each side. Load the generator and then measure the ground leakage currents in the GEC's. Also measure the voltage drop along the neutral wire. With the above data, the above equation may be verified.

Any one willing to do the above experiment?

What are the values in ohms of Rart and Raux?

 

[Ultrafault]

Why would we discuss your diagram? Where is the egc? The premise of your argument presupposes that it is convenient to install additional ground rods, yet not than the code required bonding conductors. Any of us can see that is false. You ignore any questions asked of you and only press your strawman theory forward. This is indicative of a person who is bieng intentionality obtuse.

 

[Sahib]

What are the values in ohms of Rart and Raux?

Any reasonable values you like.