Why is the neutral called the grounded conductor?

[Strathead]

I hear you, but why is there a difference of potential to the ground rod? Is it because the earth has a different potential than the xfmr or is it because there is an available path back through the earth to the xfmr the current was generated at? (Neutral) I'm having trouble understanding why my boss says the neutral on the pole and the planet earth are the same thing and that if you remove the neutral all together, current will flow to earth because it's another different potential, not because there's a path to get back to the xfmr where it was created. Will current flow to ANY difference of potential or will it only flow back to source? He said the current seeks planet earth if source cannot be found, because it's the next best potential that can be found. Is this right?



I did, and you're right there's no potential between the batteries. I always thought the dissimilar metals naturally had a potential between them inside a battery, but I guess the dielectric inside allows the potential to exist? Man I'm confused now. Thanks for sticking with me on this. I'm a visual learner so maybe I'm struggling because I can't see it in my head.



When you say that I hear "current ONLY flows from source back to SAME source." I definitely added words there but in my mind that's where all of this confusion lies. My boss says no...current can leave one potential (xfmr) and travel to any other potential it chooses (earth) and there's a complete circuit happening.


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Sorry, I can't figure out how to multiquote.

First question, getting this is VERY important, but don't let it be too complicated. Voltage requires a reference. I generally say, "How far is San Francisco?" That question can't be answered. It requires one more variable. "From where?" Voltage is the same thing. When you have two items separated by and insulation, they are going to have different charges. So we could just as easily say, "more negative and less negative" as "negative and positive" In reality, and I am sort of surmising, but it has to be true. Any two points have a difference in voltage potential even two points on a conductor. It is just so infinitesimal that we think of it as zero volts. The ground rod in my example could be charged statically, so that touching it causes an instant discharge that dissipates, or it can be because there is a path, however unlikely back to the source.

At this time, the last question. If this is what your boss says, it is time to start ignoring him. He is wrong. I am hoping you are misunderstanding him, but that is what it is. Even the term, "complete circuit" tells you this. What you hear is what it means. Science gets very sketchy when we talk about electrons. Are they particles or waves? They are probably not any more conceivable than infinity is. But for purposes of our pea brains to understand. They are. As such they don't just appear from thin air and disappear in to thin air. The source doesn't produce them from nothing and they don't become nothing, so if you look at it as one electron leaving the source, that electron has to come back to the source from somewhere. THAT is the circuit. One circuit can influence another circuit through magnetism, but that is not current flow. It is more like putting two balloons filled with water side by side. If you squeeze on one, it will force the other to move, but no water is exchanged. Again, electricity is not a marble or a piece of dust, but it is still subject to the laws of physics.

Battery... Not sure what is confusing you. Dissimilar metals that are touching create a reaction that causes current flow. Those that are separated by a dielectric are subject to the same forces as similar metals, as in the charge or voltage between is dependent on what more or less negative things they have been influenced by. The discharge of usable energy from a battery, whether a lead acid one, a capacitor, a potato, is chemistry. I think you are better off sticking with this electrical problem first, and then you can wrap your brain up with chemistry later.

One last thing. As a visual person, go back to water or better yet a hydraulic system every time. A closed loop system, will act the same way as electricity. Sometimes the analogy has to be realized, but it is there. If you dump the fluid on the ground, a person has to pour it or more, back in. that is "completing the circuit". "But it is different fluid." you say? Only until all known fluid is used, then you have to recycle. Hydraulic fluid nor electricity magically appears.

 

[teufelhounden91]

Why is the neutral called the grounded conductor?

First question, getting this is VERY important, but don't let it be too complicated. Voltage requires a reference. I generally say, "How far is San Francisco?" That question can't be answered. It requires one more variable. "From where?" Voltage is the same thing. When you have two items separated by and insulation, they are going to have different charges. So we could just as easily say, "more negative and less negative" as "negative and positive" In reality, and I am sort of surmising, but it has to be true. Any two points have a difference in voltage potential even two points on a conductor. It is just so infinitesimal that we think of it as zero volts. The ground rod in my example could be charged statically, so that touching it causes an instant discharge that dissipates, or it can be because there is a path, however unlikely back to the source.

I understand this, and I realize that there is a very different thing happening with current flow in a static situation than there is in an alternating current circuit. Where I'm confused is that static is not a two-way street as I understand it. When lightning happens there's a discharge from a high potential to a low potential but it's not bidirectional right? It seems as if the high charge would move electrons to a low charge and dissipate in the earth because there's more room for the charges to fit in that her and equalize the two potentials. So in this situation it would appear that the electrons do not travel back to source. Unless I'm way wrong and somehow charge flows in both directions to equalize charge during a lightning strike. So if all of the electricity discharges into the earth during a lightning strike why is it not possible that you could take fault current down to earth and it would also dissipate the electrons without needing to go back source? Just because one makes a circuit doesn't mean that the theory is mutually exclusive. Electron flow should be electron flow regardless if it's in a circuit or in a static buildup right?

At this time, the last question. If this is what your boss says, it is time to start ignoring him. He is wrong. I am hoping you are misunderstanding him, but that is what it is. Even the term, "complete circuit" tells you this. What you hear is what it means. Science gets very sketchy when we talk about electrons. Are they particles or waves? They are probably not any more conceivable than infinity is. But for purposes of our pea brains to understand. They are. As such they don't just appear from thin air and disappear in to thin air

Right, they already exist in the wire, they're just being vibratedback-and-forth

THAT is the circuit. One circuit can influence another circuit through magnetism, but that is not current flow. It is more like putting two balloons filled with water side by side. If you squeeze on one, it will force the other to move, but no water is exchanged. Again, electricity is not a marble or a piece of dust, but it is still subject to the laws of physics.

I agree, through inductive or capacitive coupling.

One last thing. As a visual person, go back to water or better yet a hydraulic system every time. A closed loop system, will act the same way as electricity. Sometimes the analogy has to be realized, but it is there. If you dump the fluid on the ground, a person has to pour it or more, back in. that is "completing the circuit". "But it is different fluid." you say? Only until all known fluid is used, then you have to recycle. Hydraulic fluid nor electricity magically appears.

With the water analogy, if you have one tank of water elevated, connected by a pipe to another tank on the ground "current" will flow down to the tank on the bottom(static) , I get this. Also if you have a pump at the bottom and another pipe connected back up to the source tank there will be a circuit and current will flow(circuit). Where the disconnect in my thinking is, is that if any point you take a sawsall and cut the first pipe water will continue to flow out of that pipe to the earth because it still has another lower potential and no other path back to source... But the water in the tank above will still continue to flow until is is empty. However in an electrical circuit if you cut the primary conductor that is traveling towards negative potential at the source and touch it to the earth electrons are not going to just keep dumping into the earth right? Current is going to stop immediately even though it has another place of low potential to travel to (planet earth), rather than continue to trickle down to earth to balance out right? Or since the generator back if utility is still spinning will current continue to flow into the earth as long as the earth has space for the electrons to fit in it?

For example...and maybe a poor one...will an ungrounded circuit (with no ground rod around to get those electrons back to source) fault into the earth through a motor casing and keep flowing because the earth is another place for low potential...or will that equipment seize to be energized because there's no path back to the source through a ground rod? Taking a conductor from a power pole to earth does not complete the circuit in my mind - so my thought is that taking that conductor to earth will in no way allow current to continue to flow into the earth. I do believe that maybe a static discharge can happen immediately upon fault because on that utility pole current is already heading in one direction so it has to go somewhere to stabilize like a static discharge would do.


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[teufelhounden91]

Why is the neutral called the grounded conductor?

Sorry, I can't figure out how to multiquote.

I had trouble figuring this out too but I realized all you have to do is select the text you want to quote, and pasted into the text field. Then above the text type open bracket, then the word QUOTE, then close bracket. Then after the text type open bracket, forward slash, the word QUOTE, close bracket. See pic below:

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[ActionDave]

I understand this, and I realize that there is a very different thing happening with current flow in a static situation than there is in an alternating current circuit. Where I'm confused is that static is not a two-way street as I understand it. When lightning happens there's a discharge from a high potential to a low potential but it's not bidirectional right? It seems as if the high charge would move electrons to a low charge and dissipate in the earth because there's more room for the charges to fit in that her and equalize the two potentials. So in this situation it would appear that the electrons do not travel back to source. Unless I'm way wrong and somehow charge flows in both directions to equalize charge during a lightning strike. So if all of the electricity discharges into the earth during a lightning strike why is it not possible that you could take fault current down to earth and it would also dissipate the electrons without needing to go back source? Just because one makes a circuit doesn't mean that the theory is mutually exclusive. Electron flow should be electron flow regardless if it's in a circuit or in a static buildup right?



Right, they already exist in the wire, they're just being vibratedback-and-forth



I agree, through inductive or capacitive coupling.



With the water analogy, if you have one tank of water elevated, connected by a pipe to another tank on the ground "current" will flow down to the tank on the bottom(static) , I get this. Also if you have a pump at the bottom and another pipe connected back up to the source tank there will be a circuit and current will flow(circuit). Where the disconnect in my thinking is, is that if any point you take a sawsall and cut the first pipe water will continue to flow out of that pipe to the earth because it still has another lower potential and no other path back to source... But the water in the tank above will still continue to flow until is is empty. However in an electrical circuit if you cut the primary conductor that is traveling towards negative potential at the source and touch it to the earth electrons are not going to just keep dumping into the earth right? Current is going to stop immediately even though it has another place of low potential to travel to (planet earth), rather than continue to trickle down to earth to balance out right? Or since the generator back if utility is still spinning will current continue to flow into the earth as long as the earth has space for the electrons to fit in it?

For example...and maybe a poor one...will an ungrounded circuit (with no ground rod around to get those electrons back to source) fault into the earth through a motor casing and keep flowing because the earth is another place for low potential...or will that equipment seize to be energized because there's no path back to the source through a ground rod? Taking a conductor from a power pole to earth does not complete the circuit in my mind - so my thought is that taking that conductor to earth will in no way allow current to continue to flow into the earth. I do believe that maybe a static discharge can happen immediately upon fault because on that utility pole current is already heading in one direction so it has to go somewhere to stabilize like a static discharge would do.


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You seem to think that the earth is a giant electron sucking sponge. It's not. It's just a pile of minerals, sure it's conductive, but not enough to allow for any useful current flow.

To multiquote click the little quote symbol in the lower right of each post you want to quote till you get to the last one, then click Reply With Quote.

 

[GoldDigger]

The standard simplified description given for the generation of lightning is that water droplets in the clouds collide producing a separation of charges. The problem is that separating charges in the clouds does not by itself create a voltage difference with respect to the Earth's surface.
Also, FWIW, lightning can in fact go in either direction.
One plausible explanation would be that some raindrops falling to earth would carry a net charge to the earth, building up a net charge in the cloud layer.
Then that charge imbalance is discharged by the lightning.

 

[mbrooke]

The earth is nothing more then a giant variable resistor. The greatest myths of our trade have been the importance of earthing everywhere from power quality to clearing a fault. Earth is nothing special, it has no magical properties and never will.

 

[GoldDigger]

The earth is nothing more then a giant variable resistor. The greatest myths of our trade have been the importance of earthing everywhere from power quality to clearing a fault. Earth is nothing special, it has no magical properties and never will.

Others will say that if is a big glob of stuff with varying resistivity.
You can calculate resistance for any particular geometry based on that.

 

[mbrooke]

Others will say that if is a big glob of stuff with varying resistivity.
You can calculate resistance for any particular geometry based on that.

They just worded it better then me :lol::thumbsup:

 

[iwire]

The earth is nothing more then a giant variable resistor. The greatest myths of our trade have been the importance of earthing everywhere from power quality to clearing a fault. Earth is nothing special, it has no magical properties and never will.

The earth is used by the power company for fault clearing.

 

[Strathead]

I






With the water analogy, if you have one tank of water elevated, connected by a pipe to another tank on the ground "current" will flow down to the tank on the bottom(static) , I get this. Also if you have a pump at the bottom and another pipe connected back up to the source tank there will be a circuit and current will flow(circuit). Where the disconnect in my thinking is, is that if any point you take a sawsall and cut the first pipe water will continue to flow out of that pipe to the earth because it still has another lower potential and no other path back to source... But the water in the tank above will still continue to flow until is is empty. However in an electrical circuit if you cut the primary conductor that is traveling towards negative potential at the source and touch it to the earth electrons are not going to just keep dumping into the earth right? Current is going to stop immediately even though it has another place of low potential to travel to (planet earth), rather than continue to trickle down to earth to balance out right? Or since the generator back if utility is still spinning will current continue to flow into the earth as long as the earth has space for the electrons to fit in it?


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Hopefully this answer will get you on the right path to answering the rest of them on your own. This is where the water analogy gets a little skewed. Since there is not a "place" for the electrons to be displaced in the earth, you could instead of thinking about cutting the pipe and the water draining to the ground, you would need to think of cutting the pipe and blocking it, but that isn't really good either. Wait, I just thought of something. Think of a sealed supply tank for the water. If you cut the pipe, and you have to realize that the return must be sealed, again imperfect analogy, then the water won't continue to flow out of the tank because there is nothing to displace it. There is no water coming back in and air can't get in,so the water must sit and wait until one of those two things happen. Discount the air, and the analogy is fairly good. Unless the source, (generator) is grounded, the generator can't be replenished with electrons. Analogy not fact.

 

[mbrooke]

The earth is used by the power company for fault clearing.

In some cases. It depends greatly on the system design, relaying and fault itself.


However, for the scope of 600 volt and under systems, this is the golden rule:

(5) Effective Ground-Fault Current Path. Electrical
equipment and wiring and other electrically conductive material
likely to become energized shall be installed in a
manner that creates a low-impedance circuit facilitating the
operation of the overcurrent device or ground detector for
high-impedance grounded systems. It shall be capable of
safely carrying the maximum ground-fault current likely to
be imposed on it from any point on the wiring system
where a ground fault may occur to the electrical supply
source. The earth shall not be considered as an effective
ground-fault current path.

Granted there is the TT system, however the TT system is only made feasible via GFP (RCD) breaker. Otherwise a ground fault would continue for eternity.

With that said the earth is a poor ground fault current path both for LV and MV. Even HV if the soil is dry enough.