Ground Rod Installation

[kwired]

Unfortunately there is mistake in your reasoning.Since the neutral is broken and the earth resistance of the neutral at the residence side is assumed to be zero,everything bonded to the grounded service conductor will operate at 0 volts above earth ground on the residence side.So where is the catch?

Zero volts to ground will be at/very near the grounding electrode and depending on soil conditions can drop the entire voltage imposed within just inches in poor soil. In good conductive soil we are still talking about just a few feet. This is why we have to put equipotential planes around swimming pools. Everything is tied together creating same potential to those items as well as the Eq. plane, even if full 120 volts to ground is impressed upon it. Measure from those bonded items to a point that is not bonded but is earthed several feet away though and you will have voltage.

Where are you getting the assumption that the earth resistance at the residence side is zero? I only said to use zero at the transformer for demonstration purposes to make calculations simpler to point out that the grounding electrode at the residence still has a resistance, in reality the electode at the transformer will also have a resistance that needs consideration.

 

[iwire]

Zero volts to ground will be at/very near the grounding electrode and depending on soil conditions can drop the entire voltage imposed within just inches in poor soil.

Exactly, you would pretty much have to be standing on the electrode to be at 0 potential to the neutral, as soon as you moved away from the electrode the potential would rise quickly.

 

[T.M.Haja Sahib]

Zero volts to ground will be at/very near the grounding electrode and depending on soil conditions can drop the entire voltage imposed within just inches in poor soil. In good conductive soil we are still talking about just a few feet. This is why we have to put equipotential planes around swimming pools. Everything is tied together creating same potential to those items as well as the Eq. plane, even if full 120 volts to ground is impressed upon it. Measure from those bonded items to a point that is not bonded but is earthed several feet away though and you will have voltage.

Where are you getting the assumption that the earth resistance at the residence side is zero? I only said to use zero at the transformer for demonstration purposes to make calculations simpler to point out that the grounding electrode at the residence still has a resistance, in reality the electode at the transformer will also have a resistance that needs consideration.

Why do you not agree that if the earth resistance of broken neutral is reduced further to a low value,everything bonded to the grounded service conductor can operate at a safe voltage level above earth ground on the residence side?

 

[T.M.Haja Sahib]

Here is a goofy looking but great example of what an electrode cannot accomplish.

Always?

 

[T.M.Haja Sahib]

Your assertion is wrong.

It really depends on the actual conditions.

 

[George Stolz]

Why do you not agree that if the earth resistance of broken neutral is reduced further to a low value,everything bonded to the grounded service conductor can operate at a safe voltage level above earth ground on the residence side?

Perhaps because it's not true?

Always?

Yes, with the values given.

It really depends on the actual conditions.

For all practical purposes, it doesn't matter. We are not required to meet any resistance value from the premises GES to earth; and we are forbidden from using the earth as a ground fault current return path.

 

[kwired]

Perhaps because it's not true?



Yes, with the values given.



For all practical purposes, it doesn't matter. We are not required to meet any resistance value from the premises GES to earth; and we are forbidden from using the earth as a ground fault current return path.

This all started with his suggestion that the grounding electrode will take over if the neutral conductor is lost with basically no noticeable change in performance. He needs to get past the idea he seems to have that earth is a good conductor. Sometimes you have to actually see the results of this problem before it starts to make sense, hopefully it is not the death of a fellow human that causes it to finally make sense.

 

[T.M.Haja Sahib]

QUOTE=kwired;1339465]This all started with his suggestion that the grounding electrode will take over if the neutral conductor is lost with basically no noticeable change in performance. He needs to get past the idea he seems to have that earth is a good conductor. Sometimes you have to actually see the results of this problem before it starts to make sense, hopefully it is not the death of a fellow human that causes it to finally make sense.[/QUOTE]

We are electrical professionals.Otherwise the forum administrators would not have allowed us to be talking here.We are well aware what will happen if safety procedures are breached.

My goal is not only to substantiate the observation in post no.47 but also to show a valid counterargument to it just to shed more light on the issues at hand.

So let us continue,if you are willing,our question-answer session.What is your reply to post no.63?

 

[T.M.Haja Sahib]

For all practical purposes, it doesn't matter.

See the picture in post no.60 again.It has a condition ''2-wire circuit without low impedance current path''.Of course it is a practical situation.Consider this condition:'2-wire circuit with low impedance current path''.This can also be a practical situation.But with this condition,the picture will change dramatically.

We are not required to meet any resistance value from the premises GES to earth; and we are forbidden from using the earth as a ground fault current return path.

Nor did I suggest that.

 

[SG-1]

The low impedance circuit path would be an EGC, not earth.

 

[SG-1]

Earth is a good conductor. The trouble is that we cannot make a good low impedance connection with it.

 

[T.M.Haja Sahib]

Earth is a good conductor. The trouble is that we cannot make a good low impedance connection with it.

Please see

http://en.wikipedia.org/wiki/Single-wire_earth_return

 

[kwired]

QUOTE=kwired;1339465]This all started with his suggestion that the grounding electrode will take over if the neutral conductor is lost with basically no noticeable change in performance. He needs to get past the idea he seems to have that earth is a good conductor. Sometimes you have to actually see the results of this problem before it starts to make sense, hopefully it is not the death of a fellow human that causes it to finally make sense.

We are electrical professionals.Otherwise the forum administrators would not have allowed us to be talking here.We are well aware what will happen if safety procedures are breached.

My goal is not only to substantiate the observation in post no.47 but also to show a valid counterargument to it just to shed more light on the issues at hand.

So let us continue,if you are willing,our question-answer session.What is your reply to post no.63?[/QUOTE]

I believe I have given that answer several times in this thread.

 

[kwired]

Earth is a good conductor. The trouble is that we cannot make a good low impedance connection with it.

That is a good way of summing up what I have been thinking all along.

 

[T.M.Haja Sahib]

That is a good way of summing up what I have been thinking all along.

The problem was we each had in mind a different earthing system,

Today 3 earthing system in world wide use.

1.Exposed conductive parts connected to neutral-TN system (in your mind and what you

are practicing there)

2.Earthed neutral system-TT system (in my mind what I am

practicing here)

3.Unearthed neutral- IT system

All the three systems are considered equivalent with respect to safety to life and property concerned.

 

[T.M.Haja Sahib]

We are not required to meet any resistance value from the premises GES to earth;

Consider this.Suppose we disconnect the power supply to a residence including the neutral.Measure the earth resistance of GEC at the service neutral earth point.Let it be 10 0hms.Connect a 10 ohms load between phase and neutral. Now energize with neutral disconnected. With 120V supply,the voltage drop between GEC and earth is 60V,which would be present for all the metal enclosures of equipments in the residence and this is an unsafe voltage.But in real situations this does not happen.Why? May be

1.The potential of all points inside the residence raises to the same 60V.So there is no way to get shocked. or

2.The resistance of GEC to earth is so low that such unsafe voltage does not arise.

Which one actually happens?

I doubt the equipotential condition is always achievable in practical conditions.

 

[kwired]

Consider this.Suppose we disconnect the power supply to a residence including the neutral.Measure the earth resistance of GEC at the service neutral earth point.Let it be 10 0hms.Connect a 10 ohms load between phase and neutral. Now energize with neutral disconnected. With 120V supply,the voltage drop between GEC and earth is 60V,which would be present for all the metal enclosures of equipments in the residence and this is an unsafe voltage.But in real situations this does not happen.Why? May be

1.The potential of all points inside the residence raises to the same 60V.So there is no way to get shocked. or

2.The resistance of GEC to earth is so low that such unsafe voltage does not arise.

Which one actually happens?

I doubt the equipotential condition is always achievable in practical conditions.

The potential of everything bonded to the grounded service conductor does rise to same level as grounded service conductor and touch potential between those objects is safe. The problem is there is voltage between those objects and anything else at earth potential that is not bonded to the grounded service conductor. Inside the residence there will be voltage between objects bonded to electrical system and on grade concrete floors like in a basement or garage, outside anything connected to equipment grounding conductor will have voltage to earth.

 

[T.M.Haja Sahib]

Inside the residence there will be voltage between objects bonded to electrical system and on grade concrete floors like in a basement or garage

If the second condition of post no.76 is satisfied,such unsafe voltage will also not exist.As the items such as plain concrete floors at ground level can not be bonded,the second condition is the only option. Correct?

 

[kwired]

If the second condition of post no.76 is satisfied,such unsafe voltage will also not exist.As the items such as plain concrete floors at ground level can not be bonded,the second condition is the only option. Correct?

You are getting it, but remember concrete can be bonded - it is done at swimming pools all the time for the reasons we have been discussing. But even there, voltage potentials are going to start to rise as soon as you start moving away from the last bonded item.

 

[T.M.Haja Sahib]

but remember concrete can be bonded - it is done at swimming pools all the time for the reasons we have been discussing. But even there, voltage potentials are going to start to rise as soon as you start moving away from the last bonded item.

Without reinforcement steel rods embedded in the concrete,it can not be bonded.The plain concrete floor provided in basement etc of a residence is such a construction.It can not be bonded.In such cases,we have to depend on the earth resistance of EGC to ground in respect of whether there exists a safe touch voltage or not in those places.Correct?