Why is the neutral called the grounded conductor?

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GoldDigger said:
To be totally blunt, you are totally wrong. But you are in good company. :)
The resistance of the earth is not exactly zero. But it is so low that for all practical purposes it is zero.
Individual electrons do make the whole trip. They just move a little more in that direction, as do gazillions of other electrons along the way. There is a very very small but finite voltage gradient that moves the all. The actual voltage gradient within the earth is a linear sum of all of the voltage gradients from all of the circuits that are completed through the earth.
But there are far higher voltages and currents within the core which are responsible for the Earth's magnetic field.

Finally, if there really is no earth path to the source the elections will not just wander around looking. :)
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"....do NOT make the whole trip...."
 
teufelhounden91 said:
1) Yes I agree about the poco ground. I should've specified that as well. I see what you're saying about the earth's resistance decreasing as parallel paths increase. I believe I was thinking of that backwards but either way the earth's resistance is not a constant because of the changing density of the dirt, sand, rocks, moisture, etc as well as the fact that it is a 3 dimensional plane. Theoretically however if we are being told that earth's overall resistance is 0 ohms then I believe you would be correct.

2) If this is the case (zero earth resistance) then current will always find a path back to source no matter where you are right? If fault current experiences no resistance once it hits earth why would it not always keep going to find its path back to source somewhere. Nothing is resisting it. This is why I feel like Earth can't have an exact zero resistance.

I don't think that a fault will travel 5000 miles to find source. I don't know why I feel that way but it just doesn't seem right to me that at some point the current will not just lose its momentum or and not make it to source at a great enough distance. I admit I could be totally wrong.
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A couple things: First I get the impression that you may not realize that the source is generally an isolation transformer. It couples with the higher voltage using magnetism, so electrons don't flow between the two voltage, so there is no path that takes electrons 5000 miles to a source. Second I think you are getting confused by the scope and invisibility of electricity. Pardon me if I am interpreting your words wrong.

If there isn't a path back to the source, then there isn't any fault current. Loss of momentum in regards to electricity is resistance, period. infinite resistance means no current flow. Does that make sense? I find it far easier to use water to conceive of the principles as we can instinctively understand what happens with water. If I have 5000 miles of pipe filled with water, and I put one drop more in one end, what is going to happen at the other end? Don't get hung up on what it takes to move the water, or if the drop will just drip off the beginning end. You know that an equivalent drop of water will come out the other end. Resistance with water is anything that would stop the flow of the water, just like resistance in electricity is anything that would stop the flow of electricity. With water, height is a resistance, with electricity it isn't. With water, also, the size of the pipe, the smoothness of the inside, constrictions or interruptions in the pipe are all resistances. Distance has the potential to "look" like resistance, but I think it is more of an illusion. Water takes time, so if the water on one end isn't given enough time to act then it would not move the 5000 miles of water to "push" out the other end, but given time it will happen period. Electricity moves so much faster that short distances like 5000 miles are nothing to it.
 
Before current could travel through planet Earth for a 5000 mile return trip to its source, it would have to first travel that same 5000 miles along some other conductive medium. Take another look at my "Path 2" from post #3 of this thread. Current starts at the panel, and runs out to the tool (or in the present discussion, to the point at which the wire is stuck into dirt). Care to calculate the resistance of 5000 miles of #12 THHN, and then divide that into 120 volts to get the amount of current that will flow?
 
charlie b said:
Before current could travel through planet Earth for a 5000 mile return trip to its source, it would have to first travel that same 5000 miles along some other conductive medium. Take another look at my "Path 2" from post #3 of this thread. Current starts at the panel, and runs out to the tool (or in the present discussion, to the point at which the wire is stuck into dirt). Care to calculate the resistance of 5000 miles of #12 THHN, and then divide that into 120 volts to get the amount of current that will flow?
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Based on a chart I saw, #12 solid copper wire has 1.588 ohms/1k feet @20*C. A mile would be 1.588*5.28= 8.38464ohms/mile, or 41,923.2 ohms/5k miles. 120/~42k = ~0.003A, or 3mA
 
mgookin said:
Isn't it true that the ground rod at your service is intended to form a path through the Earth to the ground rod at the pole such that when a primary crosses to a secondary it reverts energy back to the source instead of into the building?
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To a degree, but my bets are still on a metal city water main. 7,200 or 13,200 volts will definitely cause a voltage rise, especially if relying only on ground rods. In fact depending on the over current device/setting and ground rod impedance it may never trip a line protective device.
 
mbrooke said:
To a degree, but my bets are still on a metal city water main. 7,200 or 13,200 volts will definitely cause a voltage rise, especially if relying only on ground rods. In fact depending on the over current device/setting and ground rod impedance it may never trip a line protective device.
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At those voltage levels the earth will provide a path that will typically open the overcurrent device assuming a bolted fault. Basic ohms law.




If it's an arcing situation all bets are off.
 
iwire said:
At those voltage levels the earth will provide a path that will typically open the overcurrent device assuming a bolted fault. Basic ohms law.
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Going by ohms law is a wrong assumption. At 100 ohms 7,200 volts will only produce 72 amps of current. A 100K lateral fuse will never blow. At 25 ohms we are talking about 288amps, and that will blow typical lateral fuses, but main trunk lines holding is not uncommon. A typical feeder may be set 800 to 1000 amps per phase with ground pick up at 350 to 500 amps. It wont happen.
 
mbrooke said:
Going by ohms law is a wrong assumption.
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Why? Because I am not using you chosen assumptions? :D

At 100 ohms 7,200 volts will only produce 72 amps of current.
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Yeah, I agree that is how it works.

A 100K lateral fuse will never blow.
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Assuming a 100 K fuse and 100 ohms of resistance seems self serving of you.

At 25 ohms we are talking about 288amps, and that will blow typical lateral fuses,
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Which is what I was getting at, and much more typical.


but main trunk lines holding is not uncommon. A typical feeder may be set 800 to 1000 amps per phase with ground pick up at 350 to 500 amps. It wont happen.
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I agree.

But go back and read my post and understand the words used. I did not say 'the earth path will always trip the OCPD' I said

At those voltage levels the earth will provide a path that will typically open the overcurrent device assuming a bolted fault.
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Typically, as when there are typical sized OCPDs and typical resistance readings to the earth.

Most neighborhoods do not have a 'main trunk line' running down the street, most areas will have far less than 100 ohms of resistance to ground.

Are there exceptions? Certainly there are, there always is.
 
iwire said:
Why? Because I am not using you chosen assumptions? :D
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My assumptions reflect the real world. In the real world can and does have a broad range of variables.



Assuming a 100 K fuse and 100 ohms of resistance seems self serving of you.
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Because I am making a point. 100K fused lines exist (heck many 3 phase laterals are 140K here) and 100 ohms is a real world possibility.


Which is what I was getting at, and much more typical.
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Not as much when you factor in main lines. Homes and businesses do exist out on main roads.


I agree.

But go back and read my post and understand the words used. I did not say 'the earth path will always trip the OCPD' I said



Typically, as when there are typical sized OCPDs and typical resistance readings to the earth.
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Ok, I can agree on that, but typical may have been to strong a word.

Most neighborhoods do not have a 'main trunk line' running down the street, most areas will have far less than 100 ohms of resistance to ground.
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But you do have 2 main circuits on spacer cable ruining down your street :D :p
 
As always this forum is amazing because of the understanding and knowledge.
I used to joke with homeowners about the ground rod being just another way for the poco to get them to foot the bill by that ground rod using their dirt to get that current back to the ground round rod at the pole xfmr in case them little wires going to the house werent good enough.
Those were the days.

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electricalist said:
As always this forum is amazing because of the understanding and knowledge.
I used to joke with homeowners about the ground rod being just another way for the poco to get them to foot the bill by that ground rod using their dirt to get that current back to the ground round rod at the pole xfmr in case them little wires going to the house werent good enough.
Those were the days.

Sent from my LGLS770 using Tapatalk
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You arent to far off. A single ground rod does little, but thousands of ground rods plus city water mains, phone shields ect becomes a second neutral for POCOs.
 
I love to start a good rumor. Say the word and ill throw the satellite guy in the mix as a co conspirator , the way he secretly appears and puts a bonding jumper on the riser going up to a dish thats close enough for current to jump if need be. Dang power co shenanigans.

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electricalist said:
I love to start a good rumor. Say the word and ill throw the satellite guy in the mix as a co conspirator , the way he secretly appears and puts a bonding jumper on the riser going up to a dish thats close enough for current to jump if need be. Dang power co shenanigans.

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Telco guys and cable guys are always taught how important it is to tie into the home's grounding system :roll: (which is actually code btw)
 
mbrooke said:
And oh, how well grounded is this swing?


https://www.youtube.com/watch?v=28Xq3JulV1o
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Great video! God I love my job ?

So that we do not lose focus on this thread, I started a new thread and talk about this video in a different light. Please join me there if you're interested in talking about shorts vs dead shorts vs ground faults vs short circuits. I'm having another problem with the master electrician I work for using incorrect terminology, but I need to fact-check myself and make sure that I am using correct terminology is well.

http://forums.mikeholt.com/showthread.php?t=172664


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teufelhounden91 said:
Great video! God I love my job ?

So that we do not lose focus on this thread, I started a new thread and talk about this video in a different light. Please join me there if you're interested in talking about shorts vs dead shorts vs ground faults vs short circuits. I'm having another problem with the master electrician I work for using incorrect terminology, but I need to fact-check myself and make sure that I am using correct terminology is well.

http://forums.mikeholt.com/showthread.php?t=172664


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Poco needs afci protection. The video proves it.

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All right fellow wizards, I just had another discussion with the boss man and he said that current does not need to travel back to the same source but current can find another "source" to travel to and as long as there is a difference of potential, current will still flow. He said that the earth has such a high resistance value and it has such a different potential than the source voltage at a utility that current will still flow and you could still light a lightbulb in between a hot from the utility and the other side of the potential (the earth). He said current flow has nothing to do with getting back to the original source neutral. As long as you have a difference of potential and a high enough resistance value current will flow. His example was if you are at a light pole that is near a utility transmission line, and you get and induced voltage on that pole that you can take a wire from the pole go over to the break caliper on the car with rubber tires and no contact with earth, it will allow current flow. In this instance you have no reference through the earth back to source neutral so how is this possible? His next impossible situation was that if we have a hot wire coming from the utility and we can touch it to a building that is completely insulated from the earth with a massive piece of rubber he still thinks current will flow because of the resistance value of that building. He said if there's a high enough resistance in the entirety of that building, it will be an opposite polarity for electricity to discharge to.... Regardless of earth. He also said that a guy standing in an insulated bucket was recently shocked near transmission line current flowed through the air from the line to him and he got shocked with no referenced through the ground back up to source. How is this possible if current has to leave source and return to source to flow?


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