Purpose of Grounding Electrode System

[daytonajim00]

Hello everyone,

I've been a following the forums for years now and have finally joined.

For whatever reason, grounding and bonding seems like the most misunderstood sections in the electrical field- at least on the construction end. Either I understand some things wrong or most other electricians I've met do. The specific topics I most frequently get into debates about are as follows:

An electrical system must have a grounding electrode system. Grounding electrodes are buried metal, like ground rods, water pipe, etc., per NEC, that connect to our electrical system, offering zero potential to ground.

Why do we make a purposeful connection to earth is where the debate comes in. Many responses are "to clear faults" or "to assist in opening a breaker during a fault" or "to protect against electrical shock".

I thought our connection to earth has nothing to do with clearing a fault. So let's consider a fault: electricity needs a path back to its source to flow. During a fault current flows onto the intentionally bonded surface, back to the main bounding jumper, on to the neutral, offering a complete circuit (home) of low resistance at which point a properly functioning breaker will trip.

So what is the point of the ground rod (GE) then?

I always thought a ground rod- or any other GE's main purpose is to offer zero potential between the bonded metal parts of our electrical system and earth. This is done to quickly 'drain' foreign voltages like lightning, static, and other abnormal surges."

I've read other reasons why the GE system is required... As far as tethering our service down to stabilize voltages during normal operation I'm not sure about. I've installed systems that were not bonded by design. These were operating room SDS's in hospitals where the neutral was always completely floating. Voltages seemed fine.

I think a lot of confusion comes from the word 'ground' and people automatically think earth. I think they see the ground rods as the 'master component' of the equipment grounds we usually include throughout the system. Add to the mix the 'grounded conductor' (neutral) and most apprentices get totally lost. I was for the first four years. I was never taught correctly.

So what I'm saying is please correct me if I'm wrong. 95% of the electricians I've met think the GE system has something to do with the voltages we use (utility or emergency standby).

What does the community think?

 

[electrofelon]

I like to say that system grounding isn't about safety, it's just a system topology. It effects the potential between the various conductors and earth, the number and placement of OCPD's, and how faults are handled.

 

[jaggedben]

The purpose is multifold, but is generally to remove any potential between the earth and exposed bonded metal parts, so that no one standing on the earth in bare feet who touches a bare metal part will get electrocuted. There a variety of ways that a potential difference could end up in unintended places. In the US it is also significant that we use a grounded conductor as a fault clearing path. However, my understanding is that even in countries where they don't do that, they still ground expose metal non-current carrying parts, just in case an ungrounded system becomes unintentionally grounded.

 

[daytonajim00]

So electrofelon, you are saying that grounding (to earth) our systems is about the potential between conductors and earth, OCPD's, and clearing faults?

Jaggedben, you are saying that grounding (to earth) our systems is about the making equal the potential between exposed bonded metal parts, to protect people in bare feet from electric shock?

Let me give a scenario and use both of those responses. Scenario is there is NO grounding electrode system installed but all metal parts are bonded and all circuits have equiptment grounds going back to the main in which the neutral is bonded. Basically a normal system minus the GE's.

Electrofelon, should a fault occur in this system, would it not find its way back to the neutral and trip the breaker?

Jaggedben, since electricity needs to flow back to neutral for one to get shocked, would the removal of the grounding electrodes make a difference? If anything, becoming energized in bare feet with ground rods installed would increase the chance of current flowing and one getting shocked. The current would have that much better of a path: through the slab, across the ground, up the ground rod's GEC, onto the neutral.

Like I said, perhaps I have had it wrong, but this is exactly like other conversations I've had.

 

[jaggedben]

...

Jaggedben, since electricity needs to flow back to neutral for one to get shocked, would the removal of the grounding electrodes make a difference?

Well, let's say the utility neutral fails open, then it would make a pretty big difference. Now the current will try to flow from any bonded metal, through a person with bare feet, to the earth, and back to the grounded neutral node at the utility transformer.

If anything, becoming energized in bare feet with ground rods installed would increase the chance of current flowing and one getting shocked.

No, it wouldn't.

The current would have that much better of a path: through the slab, across the ground, up the ground rod's GEC, onto the neutral.
...

That would only happen if the metal you touched wasn't already properly bonded to the service neutral with an EGC, which is its own hazard. Even if there were no ground rod and GEC locally, you could still get shocked by that metal, because the neutral is grounded back at the utility transformer as well. Having a local grounding electrode system doesn't meaningfully increase that hazard.

 

[jaggedben]

Well, let's say the utility neutral fails open, then it would make a pretty big difference. Now the current will try to flow from any bonded metal, through a person with bare feet, to the earth, and back to the grounded neutral node at the utility transformer.
...

I should add, it would even worse if, in the course of responding to an open utility neutral, someone happens to touch both an electrical conduit and a cold water pipe that goes underground to the street. That water pipe is a functional electrode, so now the person becomes a GEC. If there is already a code compliant low-impedance GEC, then significant current will already be flowing, and the voltage drop between those two pieces of metal will be negligible. The negligible voltage drop is what the person will experience instead of possibly a voltage higher than the line-neutral voltage.

 

[romex jockey]

Welcome to MH Jim

First, i would encourage you to go here ,as MH's forum is international

2ndly, know that we exist on one big nuetral , the closer to substations one gets , the more this applies.

3rd, Tesla was right

more as the crew opines

~RJ~

 

[daytonajim00]

Well, let's say the utility neutral fails open, then it would make a pretty big difference. Now the current will try to flow from any bonded metal, through a person with bare feet, to the earth, and back to the grounded neutral node at the utility transformer.

If the neutral on the utility failed open, I would guess an electrician is on the way because no single phase circuit using a neutral would be working. In the event that a fault on a piece of metal happened directly after said neutral failure, I can see a hazard laying await. Whether you had a GES apart of that building or not would not matter, the hazard would be the same: there would not be enough conductivity through the earth to clear the fault. This is why, to my understanding, the GES has nothing to do with clearing faults. I could be misunderstanding something but what you explained is a doomsday scenario. It's also the reason why every electrician should know the theory behind all of this. When going on a call never assume anything. I would use an amp probe on the GEC even if everything seems to be working fine. Voltage is easy to see. Current is the invisible killer.

That would only happen if the metal you touched wasn't already properly bonded to the service neutral with an EGC

I was thinking more in line with becoming energized from an ungrounded conductor. But I can see what you mean that it doesn't make a difference because the utility transformer in grounded as well. The only difference is there would be more earth to have to travel through for the current to make it there.

 

[romex jockey]

We should invite Mr Kirchoff into this thread... ~RJ~

 

[daytonajim00]

We should invite Mr Kirchoff into this thread... ~RJ~

Or Mike Holt. They wrote an article titled"Ground Rod Does Not Assist in Clearing a Fault"


https://www.mikeholt.com/technical-...Not-Assist-in-Clearing-a-Fault-(01-25-2K).php

And before the thread gets off topic- which is cool too- I would just like to bring it back to my original point. Why do we bond our electrical systems to earth?

Is it for lightning, static, and other foreign surges like I thought or is there something I'm missing?

 

[al hildenbrand]

If the neutral on the utility failed open, I would guess an electrician is on the way because no single phase circuit using a neutral would be working.

In the presence of a water pipe grounding electrode, where the water pipe is from a municipal system, and where neighbors are also connected to the same Power Company transformer secondary, the loss of YOUR service grounded conductor will only shift unbalance currents into your neighbor's service connections.

However, if there is no local connection to a grounding electrode system that includes a municipal water pipe so connected, the open service grounded conductor results in the neutral on the load side of the Service Disconnect having a voltage derived from the balanced, or unbalanced, load impedances.

 

[ActionDave]

Or Mike Holt. They wrote an article titled"Ground Rod Does Not Assist in Clearing a Fault"


https://www.mikeholt.com/technical-...Not-Assist-in-Clearing-a-Fault-(01-25-2K).php

And before the thread gets off topic- which is cool too- I would just like to bring it back to my original point. Why do we bond our electrical systems to earth?

Is it for lightning, static, and other foreign surges like I thought or is there something I'm missing?

I think the main reason is it is all but impossible to maintain an ungrounded/unearthed system, so it's best to go ahead and get something earthed. You mentioned OR rooms. Look at the work that has to be done to make that happen. Also, there are problems with ungrounded systems, capacitive coupling shocks and voltage spikes.

Norway tried to go with a totally unearthed system and it didn't work. There was a post on this forum a couple of years ago about how bad it worked out. I tried tried to find it but failed. Maybe someone with better google skills can find it.

 

[daytonajim00]

I would like to read that article Actiondave. I know a lot of work and money goes into ungrounded systems- where the neutral is left floating. It may be a bad anecdote to include that leads to a distraction. At any rate it leads back to my question: why do we bond our systems to earth? Why do we set up a GES? I thought it was for lightning, static, and other foreign voltages. So according to this thread, the main purpose of setting up a GES is as follows:

1.) Clearing faults
2.) Safe guarding against from electrical shock

Is this correct?

 

[jaggedben]

If the neutral on the utility failed open, I would guess an electrician is on the way because no single phase circuit using a neutral would be working. In the event that a fault on a piece of metal happened directly after said neutral failure, I can see a hazard laying await. Whether you had a GES apart of that building or not would not matter, the hazard would be the same: there would not be enough conductivity through the earth to clear the fault.

You need to read up on what happens when you have an open neutral, because it isn't nearly as simple as that. It's also not a 'fault' in the typical sense. The danger I described is there if you don't have a GES, and essentially not there if you do. That makes it a lot safer both for the homeowner who should turn off all his breakers right away, and the electrician who needs to check it out after getting the call. Both of those persons probably have to touch some metal housings to do that, and it's good if those metal housings don't have too many electrons trying to get out with nowhere to go besides those persons.

This is why, to my understanding, the GES has nothing to do with clearing faults. I could be misunderstanding something but what you explained is a doomsday scenario. It's also the reason why every electrician should know the theory behind all of this. When going on a call never assume anything. I would use an amp probe on the GEC even if everything seems to be working fine. Voltage is easy to see. Current is the invisible killer.

Here you are basically correct, but you talking around the subject of what the GES does.

...

And before the thread gets off topic- which is cool too- I would just like to bring it back to my original point. Why do we bond our electrical systems to earth?

Is it for lightning, static, and other foreign surges like I thought or is there something I'm missing?

It is all those things, and then some. (An NEC-compliant GES is not a lightning protection system, though; that is something else.) Dave's point about ungrounded systems becoming unintentionally grounded is an important one. So, once we have grounded systems, it's fairly important that they are consistently grounded. Each premises GES plays a role in that.

 

[ActionDave]

I would like to read that article Actiondave. I know a lot of work and money goes into ungrounded systems- where the neutral is left floating. It may be a bad anecdote to include that leads to a distraction. At any rate it leads back to my question: why do we bond our systems to earth? Why do we set up a GES? I thought it was for lightning, static, and other foreign voltages. So according to this thread, the main purpose of setting up a GES is as follows:

1.) Clearing faults
2.) Safe guarding against from electrical shock

Is this correct?

We connect to earth because earth is the ship we are on and it is too hard to maintain a system that is unearthed. You are correct that it has nothing to do with clearing a fault, don't let anybody try and talk you out of that.

 

[daytonajim00]

We connect to earth because earth is the ship we are on and it is too hard to maintain a system that is unearthed. You are correct that it has nothing to do with clearing a fault, don't let anybody try and talk you out of that.

Thanks ActionDave. I only ever had these discussions with those as interested as me with the topic. Electrical theory is VERY interesting.

Earth is the ship we are on and the voltages that come along with that ship must be addressed (lightning, static). That is the point of the GES. No? We create man made voltages (high voltage from utility) that aren't apart of our systems because our systems are stepped down in voltage through induction, so those higher voltages need to be addressed as well should they find a way on our stepped down systems. That is the point of the GES too. Is that what that means? That's how I currently understand it.

Could you take an AC system, complete from generator to outlet, and have it function properly floating on a blimp, not connected to the earth?

Also, can a small generator on wheels that we get at the local hardware store supply clean AC power without needing to be grounded to earth?

If so, what makes our common systems different? Why would we include the GE system. I think it's because we can sacrifice a small generator to a lightning strike. What we don't want is a lightning strike jumping on a whole service and then some. I would imagine the utility provider grounds their systems for the same reason.

 

[MAC702]

...Norway tried to go with a totally unearthed system and it didn't work. There was a post on this forum a couple of years ago about how bad it worked out. I tried tried to find it but failed. Maybe someone with better google skills can find it.

This has a 2004 copyright at the bottom. Does this address what you are thinking?

https://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/The-Grounding-Truth~20040602.php

 

[ActionDave]

This has a 2004 copyright at the bottom. Does this address what you are thinking?

https://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/The-Grounding-Truth~20040602.php

That's not what I was talking about but that is a great link.

 

[mbrooke]

Lets no forget the reason why utilities use grounding electrodes... I think that is the force behind the grounding electrodes.

 

[ActionDave]

Thanks ActionDave. I only ever had these discussions with those as interested as me with the topic. Electrical theory is VERY interesting.

Earth is the ship we are on and the voltages that come along with that ship must be addressed (lightning, static). That is the point of the GES. No? We create man made voltages (high voltage from utility) that aren't apart of our systems because our systems are stepped down in voltage through induction, so those higher voltages need to be addressed as well should they find a way on our stepped down systems. That is the point of the GES too. Is that what that means? That's how I currently understand it.

It's a common point and is easy to find and connect to.

Could you take an AC system, complete from generator to outlet, and have it function properly floating on a blimp, not connected to the earth?

Yes.

Also, can a small generator on wheels that we get at the local hardware store supply clean AC power without needing to be grounded to earth?

Yes.

If so, what makes our common systems different? Why would we include the GE system. I think it's because we can sacrifice a small generator to a lightning strike. What we don't want is a lightning strike jumping on a whole service and then some. I would imagine the utility provider grounds their systems for the same reason.

If there were a better way it would have been implemented. We've been solidly grounded for almost a century now. More than that if you go back to the telegraph days.