Grounded conductor (neutral) and earth voltage

[kwired]

This makes sense. I’m going to study it again and knowing this will help.

If you were to place many ground rods in succession and maybe create some sort of bonding of the entire earth from the rod at the house all the way to the rod at the transformer, then you couldn’t get a difference in potential between a hot conductor shorted to the ground rod and ground surrounding it, right? Would that be comparable to equipotential bonding by eliminating touch potential of the ground rod?

Is a step in the same direction as creating an equipotential grounding system around the pool. Steel encased in concrete in general will still have lesser resistance to earth than a rod that has less contact with the earth.

then you couldn’t get a difference in potential between a hot conductor shorted to the ground rod and ground surrounding it, right?

You still have potential between this and the "hot conductor" and it is most if not all the potential that the system normally sees between that particular ungrounded conductor and the grounded conductor of the system.

What you are doing is keeping the area near those rods closer to whatever potential the grounded conductor is at the point you connected to it.
If there is no current on the ungrounded conductor then that potential is very near earth potential. If there is current on the grounded conductor then there is a voltage drop on the ungrounded conductor, which will make the voltage to earth equal to the amount of voltage that has dropped across the grounded conductor, presuming it is also has a ground reference at the source.

 

[Fred B]

There is some significant misunderstanding by OP related to Bonding and Grounding vs Equipotential Bonding and neither are alike other than a connection that is "electrically" continuous between points.

Bonding of the electrical system is to provide a electrically continuous connection of the normally non current carrying parts of the electrical components and system that helps to provide a low resistance means for a fault to be cleared.
Grounding of the electrical systems is a connection to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

The EP bonding is to provide a means to put everything within the reach of the area to be bonded at the same potential and thus prevent a flow of current that could be a danger to persons or animals (Farm application) due to a difference of potential between point A and B with both being within reach. EP bonding is even done at utility substations, Utility Solar farm, and Utility Wind farm equipment. EP Bonding on a pool or even a structure such as a barn, even if no power supplied equipment are present, is beneficial as there are times a NEV potential is present from the utility service. Seen on a pool that had voltage present even with everything electrical disconnected from the pool, source was from Utility neutral being compromised and once repaired voltage was eliminated.

To illustrate the need for EP bonding You can measure the "step potential" from an energized point at earth to a distance from that point along the earth gradually reducing the farther from the source point, and will vary depending on soil conditions. Example: If source point is at 120V 1 ft away could be 110V 2 ft @ 90V 3ft @ 75V, So a single stride could provide 45V between the one foot and the other foot in this scenario, and a shock hazard. If in a swimming pool it could be enough to cause shock drowning as that can occur with just milli-amps of current.

 

[Bro8898]

You can do it in someone's backyard or around a barn but you can't make the whole 500 square mile county an equi-potential plane.

Good point. This is helpful.

 

[Bro8898]

neither are alike other than a connection that is "electrically" continuous between points.

Thank you for pointing this out. I’ve been trying to understand one in order to understand the other and I think it helps to separate the two concepts.

EP Bonding on a pool or even a structure such as a barn, even if no power supplied equipment are present, is beneficial as there are times a NEV potential is present from the utility service.

This is good. And answers what I was originally asking. Although I did think it also applied to a current carrying conductor coming in contact with the ground and causing a shock hazard for someone in the water. I may need to rethink that.

Example: If source point is at 120V 1 ft away could be 110V 2 ft @ 90V 3ft @ 75V, So a single stride could provide 45V between the one foot and the other foot in this scenario, and a shock hazard.

I assumed that the potential voltage difference would increase as one’s feet were further apart. Meaning if you hop on one foot or keep both feet together there is less of a voltage difference than if you stand with both feet two feet apart. I may need to get a better understanding from what I was thinking. I will read and inform myself on this and come back.

Thank you so much for your teaching.

 

[kwired]

Example: If source point is at 120V 1 ft away could be 110V 2 ft @ 90V 3ft @ 75V, So a single stride could provide 45V between the one foot and the other foot in this scenario, and a shock hazard.

The reason we do this in art 547 applications is things like cows have four feet, don't wear any shoes, and can span across more voltage gradient in the surface they are standing on than what people do standing on only two feet.

Swimming pools simply have enhanced conductivity and being immersed in the water enhances conductivity of user's skin as well, which makes it possible to span across more voltage gradient easier than in most other situations

 

[Bro8898]

can span across more voltage gradient in the surface they are standing on than what people do

Can you explain the statement you quoted above? Is this saying that the farther your feet are apart the greater the potential difference in voltage and opportunity for more current to flow when both are touching the ground?
If source point is at 120V 1 ft away could be 110V 2 ft @ 90V 3ft @ 75V, So a single stride could provide 45V between the one foot and the other foot in this scenario, and a shock hazard.

I read a paper by someone named Zipse about neutral current flowing through the earth. Is equipotential bonding a way to decrease the negative effects of neutral current flowing through the ground?

Thanks

 

[don_resqcapt19]

Can you explain the statement you quoted above? Is this saying that the farther your feet are apart the greater the potential difference in voltage and opportunity for more current to flow when both are touching the ground?
If source point is at 120V 1 ft away could be 110V 2 ft @ 90V 3ft @ 75V, So a single stride could provide 45V between the one foot and the other foot in this scenario, and a shock hazard.

I read a paper by someone named Zipse about neutral current flowing through the earth. Is equipotential bonding a way to decrease the negative effects of neutral current flowing through the ground?

Thanks

that would have no effect on the current flowing in the earth.

 

[wwhitney]

that would have no effect on the current flowing in the earth.

I agree there would be no practical effect on the current magnitude, but if the current is causing a voltage gradient, the equipotential bonding should reduce that voltage gradient, yes? By replacing the resistance of the earth with the resistance of the bonding conductor, and so lowering the voltage gradient per unit length per unit current.

So, in that sense, yes, the equipotential bonding will decrease one of the negative effects of the current, namely the voltage gradient it causes.

Cheers, Wayne

 

[don_resqcapt19]

I agree there would be no practical effect on the current magnitude, but if the current is causing a voltage gradient, the equipotential bonding should reduce that voltage gradient, yes? By replacing the resistance of the earth with the resistance of the bonding conductor, and so lowering the voltage gradient per unit length per unit current.

So, in that sense, yes, the equipotential bonding will decrease one of the negative effects of the current, namely the voltage gradient it causes.

Cheers, Wayne

Yes, reducing the gradient or step potential is the most common purpose.
I was reading it as the overall issues in the earth that Zipse often wrote about...most notably neutral to earth voltage.

 

[Flicker Index]

Something that is common with sound and video system is when current in the order of several amperes flow where it shouldn't and interferes with signal circuit.

For example, if the power amplifier is plugged into an outlet there, and its hooked up to a piece of instrument that's plugged into a different grounded outlet, there maybe a half volt difference.

Another common example is horizontal bars on TV from current flowing through the chassis due to a few amps flowing between grounded coax and grounded chassis.

 

[Flicker Index]

Can you explain the statement you quoted above? Is this saying that the farther your feet are apart the greater the potential difference in voltage and opportunity for more current to flow when both are touching the ground?
If source point is at 120V 1 ft away could be 110V 2 ft @ 90V 3ft @ 75V, So a single stride could provide 45V between the one foot and the other foot in this scenario, and a shock hazard.

I read a paper by someone named Zipse about neutral current flowing through the earth. Is equipotential bonding a way to decrease the negative effects of neutral current flowing through the ground?

Thanks

Wrap the long ends of a sub sandwich with tin foil, then attach the ends to a doorbell transformer. For the purpose of this demo, leave the secondary floating (not grounded).

The current flowing through the bread is "constant". Jab your voltmeter probes at any two points in the bread. The farther apart the probes, the higher the voltage "step potential" you'll see, thus higher the current flowing through the meter. The step potential doesn't have to be at a dangerous level for it to cause behavioral effects on livestock.

 

[ggunn]

The reason we do this in art 547 applications is things like cows have four feet, don't wear any shoes, and can span across more voltage gradient in the surface they are standing on than what people do standing on only two feet.

How Lightning Can Kill 300 Reindeer With One Strike

It all comes down to some basic principles of electromagnetism—and some unfortunately placed permafrost.

www.wired.com

 

[Bro8898]

The current flowing through the bread is "constant". Jab your voltmeter probes at any two points in the bread. The farther apart the probes, the higher the voltage "step potential" you'll see, thus higher the current flowing through the meter. The step potential doesn't have to be at a dangerous level for it to cause behavioral effects on livestock.

So if I were to put a clamp around the bread (or the wire) it would be the same current no matter where I placed it. But if I put each lead of the meter into the bread I’ll see a greater voltage difference the farther apart I place them, and thus more potential for current to flow.

In this statement it seems that the farther away the leads are the less voltage there is between them, am I interpreting it incorrectly?
120V 1 ft away could be 110V 2 ft @ 90V 3ft @ 75V

 

[Flicker Index]

So if I were to put a clamp around the bread (or the wire) it would be the same current no matter where I placed it. But if I put each lead of the meter into the bread I’ll see a greater voltage difference the farther apart I place them, and thus more potential for current to flow.

In this statement it seems that the farther away the leads are the less voltage there is between them, am I interpreting it incorrectly?
120V 1 ft away could be 110V 2 ft @ 90V 3ft @ 75V

Correct, clamp meter would read the same.

Farther apart, the higher the voltage. This is why in a downed power line situation, you should bunny hop with feet as close together as possible.

X--A--B--C--D--E--X

C-D would read 20v,
C-E would read 40v
X-X would read 120v

 

[Bro8898]

Correct, clamp meter would read the same.

Farther apart, the higher the voltage. This is why in a downed power line situation, you should bunny hop with feet as close together as possible.

X--A--B--C--D--E--X

C-D would read 20v,
C-E would read 40v
X-X would read 120v

That’s what I was thinking. Thank you for the response.

 

[kwired]

Can you explain the statement you quoted above? Is this saying that the farther your feet are apart the greater the potential difference in voltage and opportunity for more current to flow when both are touching the ground?
If source point is at 120V 1 ft away could be 110V 2 ft @ 90V 3ft @ 75V, So a single stride could provide 45V between the one foot and the other foot in this scenario, and a shock hazard.

You sort of on the right track, but your second sentence needs more clarification.

If you drive a rod in the ground and apply 120 volts (to ground) on it, the area close to the rod is going to be near 120 when referenced to true earth. the farther away you go the less the measurement of the surface will be to true earth. How far away until there is little or no voltage to measure will depend on soil conditions and will vary even will vary when wet vs dry for the same setup.

Now consider that a person standing on their feet with shoes that provide some insulating value can probably touch the rod and in the right conditions may only get a little tingle or even feel nothing at all, try it again in wet conditions and they get hit pretty hard, may not be subjected to full 120 volts but likely still most of the 120.

Now presume a drinking tank for cattle replaces the rod mentioned above and is energized to 120 volts (they do put 120 volt heaters in those to keep them from freezing in places that get cold). The tank may have some earth bond just by it's design and will act like an electrode and will have voltage gradients around it in this situation. If a cow touches the tank/water with it's mouth it could be spanning six feet or so across that voltate gradient on the surface to where it's back feet are in relation to the tank.

They are usually found dead by the tank if it is energized by direct fault. What is less obvious is when there is just a rise in voltage on the EGC of say 10 volts that is imposed on the tank. A human might touch the tank and feel little or nothing, really will depend on how insulated their footwear is for the most part. The cows will feel the gradients in the surface between front and rear legs as they are approaching but before they ever reach the tank and don't like what they feel, and simply stay away and ultimately don't drink.

 

[Bro8898]

What is less obvious is when there is just a rise in voltage on the EGC of say 10 volts that is imposed on the tank.

What might cause this? Is it due to a short from a hot conductor to something that the egc is bonded to - in this case the breaker should trip right?

the area close to the rod is going to be near 120 when referenced to true earth

How far away until there is little or no voltage to measure will depend on soil conditions and will vary

I think it’s starting to click. The voltage potential difference from the rod (with 120 volts shorted to it) to the ground surrounding it will be higher than the voltage potential from the rod to ground a longer distance from it (because of resistance of the soil that varies based on soil conditions). Vs step potential which takes into account the whole circuit and in this case the farther the distance between points in the circuit the greater the voltage potential between them.

The cows will feel the gradients in the surface between front and rear legs as they are approaching but before they ever reach the tank and don't like what they feel, and simply stay away

Regarding equipotential bonding, when everything in the area is bonded and there is an underground bonding structure as well, this big bonding apparatus is not required to be bonded to neutral, or anything right? So instead of the cow or human being a part of the path we have lowered the resistance of everything in contact with the energized drinking tank to make it the lower resistance path and the cow walking across the ground surface is in parallel with the circuit. The 10 volts on the tank to ground “chooses” the ground and everything that’s bonded to it (equipotential bonding) as the path to complete the circuit back to the transformer instead of a cow or human. Does this sound like I’m on the right track? So this leads me to the question, if you were to step one foot on the ground over the underground bonding ring and the other foot on the other side where it’s not below you, would there be a potential difference and would someone or a cow feel current flow?

Appreciate the long and detailed response. It was very helpful. Thanks for taking the time to write that.

 

[Fred B]

Regarding equipotential bonding

path to complete the circuit back to the transformer

Equipotential Bonding has zero to do with path back to the transformer.

Equipotential bonding simply creates an environment which there would be no voltage difference between points of reference, thus no current flow, thus no shock potential. (Bird on a wire effect)

Again EP bonding and Bonding for grounding or grounded conductors are two very different things and not comparable.

EP bonding would give a similarity to (but don't try it) you being totally insulated from any other conductive source wire, metal or earth. and you can touch a single point on a voltage source and you will not get any current flow though you as there is no flow possible. See this bare hand electric work video:

 

[Bro8898]

Equipotential Bonding has zero to do with path back to the transformer.

This is very helpful. I think I’m starting to get it now. No current can flow if there’s no difference in potential between two points.

Again EP bonding and Bonding for grounding or grounded conductors are two very different things and not comparable

I really appreciate you clearing it up. I studied it pretty hard and this makes it click hearing it here.

It sounds like the underground bonding grid, around a pool for instance, is so well connected with the earth that if a hot conductor touches the earth at that point, then current still can’t flow because the earth itself is brought to the same voltage potential as the hot conductor in contact with it (in that particular location). There might be a difference in potential between the earth and the hot outside of the bonded area but within that particular space everything is at the same potential. I think this is where my confusion was happening. Does that sound like I’m making progress with this concept?

The video was very helpful as well. Thank you so much Fred.

 

[Fred B]

It sounds like the underground bonding grid, around a pool for instance, is so well connected with the earth that if a hot conductor touches the earth at that point, then current still can’t flow because the earth itself is brought to the same voltage potential as the hot conductor in contact with it

The EP bonding has nothing directly to do with the earth potential or grounding. A high voltage or any "hot" conductor making contact with the EP bonded items, or even earth will attempt to "flow" current back to the source. The only thing that would effect the "flow" is the resistance of the earth and the ability of the "hot" wire from blowing a fuse or breaker.
In fact NEV also can and does have an effect on the EP bonded items, in that "if" not done correctly someone at one potential touches something or someone at a different potential will get shocked. NEV is almost always at some level present where there is an electrical utility is around. Seen even on lake water where the utility fault was miles away. (Whole other issue related to bonding and safety.)
If there is a high enough difference of potential is present, electrocution and death can occur.
EP bonding is why in the video even at 220kv the person was able to "bare hand" the live wire.