It's all mathematics, my friend.

 

Gee don't you read all the posts.
I just explained how that is implemented in the UK .
As a ground conductor think of the earth as a huge circular conductor.
Max.

Somehow I don't really understand your posts Max...........I'm not a native english speaker

 

As per the U of Penn PDF.
Early developers of electrical systems theorized that the earth was an electrically neutral body, i.e. an equal number of negative and positive charges are distributed throughout the earth at any given time. Being electrically neutral, earth is considered to be at zero potential and establishes a convenient reference frame for voltage measurements. Noting that voltmeters read only the difference in potential between two points, absolute measurements can be made by using earth as a reference.

A true earth ground, as defined by the National Electrical Code, physically consists of a conductive pipe or rod driven into the earth to a minimum depth of 8 feet.
Max.

 

Paulo............I believe I understand your problem. Please refer to the diagram in post #19. This will only work with that circuit, it will NOT work with a mains supply. Because the mains supply is reference to ground already.

Disconnect the ground. Get your meter out. A pretend meter will work, if you understand potentials and currents.

Start up your generator. To measure the voltage across the load, you will have to put the meter leads across the load. Red lead on top and black lead on bottom of load symbol. You will read an RMS of the supply ac voltage.

Now, remove the black meter lead, and connect it to ground. What voltage do you read on the meter? 0.

Put the black lead back on the bottom of the load. You will see the voltage again. Now take the red meter lead and connect it to ground. What voltage do you read? 0.

Now, take the red meter lead and put it back on top of load. You will see the supply voltage.

Now....while the generator is on...and you are reading the voltage across the load, connect a jumper from the bottom end of the load....to ground.

Did the meter reading change? No. Disconnect the ground from the bottom of load and put the ground at the top of load. Did the meter reading change? No.

Do you see what is happening here? It's a matter of reference. The ac generator has two output poles. Referencing one of these poles to ground does not effect power transmission.

The pole that we selected as ground, becomes a NEUTRAL conductor.

A neutral conductor is a conductor that USUALLY and NORMALLY has no potential or voltage on it. We took the potential off of it by grounding it.

But it still has the current potential. This can be most dangerous. Some idiot will measure a neutral and see no voltage on it..................and think it is safe to touch or to disconnect.

IF, or as soon as it is disconnected, the neutral will receive and establish the full "hot" voltage. This voltage is supplied thru the load.

That hot voltage will now be between the neutral and ground, You do not want to be between them.

All power generation is symmetrical (balanced) and gives us two equal potentials. (+ and - poles) By grounding one of the potentials, we can deliver the same amount of power with one potential. This gives us safety and a common reference of ground for the other potential.

Hang on.... let me finish reading this.

 

I think I understand now. Some final questions.............................

What does it mean to measure a voltage in relation to the earth ? Voltage is Joules per Coulomb.


AND.............


"If one of those poles is also connected to ground, then the voltage on the other pole can also be referenced to ground. "

is that because if one of them is connected to ground, then the ground becomes kind of an all encompassing fluid that can be used to measure voltages on the hot wire, or anywhere else for that matter ?

 

Measuring voltage to reference the earth means using earth as a zero potential. That means we can measure a positive potential and a negative potential from the same reference (earth). And at the same time of course.

Only one leg of the power supply potential can be grounded. i.e. neutralized. i.e. referenced to ground.
When you ground one leg, you still get the full negative swing and the full positive swing on the hot conductor.

And yes on the encompassing fluid, except it's not a fluid, it's a conductive surface of ground potential.

There are other circuit configurations (both power and signal) where the neutral is not grounded.
In this case the neutral is referenced between the two poles, and not ground.

All of my statements are based on your circuit diagram. Commercial power is not generated or transmitted in this fashion.

 

The earth is a special conductor. It is a conductive surface like other conductors, but the earth conductor can actually source and sink electrons. It's an active conductor.

Notice I said electrons and not charge. That subtle difference will become important later in your studies, one way or another.

So, have you got the idea of a neutral ac leg now? And do you understand that current flows thru your neutral, but not thru the ground?

 

50 Volts is measured across the load. It's positive one moment and negative another. Whatever the cycles per second - whatever the amplitude, the measurement is across the load. If you measure to ground (common points) you get zero volts. If you measure across the upper part of the load in the drawing you get 50 VAC (positive one moment and negative another).

 

The earth is a special conductor. It is a conductive surface like other conductors, but the earth conductor can actually source and sink electrons. It's an active conductor.

Notice I said electrons and not charge. That subtle difference will become important later in your studies, one way or another.

So, have you got the idea of a neutral ac leg now? And do you understand that current flows thru your neutral, but not thru the ground?

I have been with my eyes closed for the past 20 mins trying to imagine every possible detail. As I understand now, the ground connection makes no difference to the circuit, it only provides a point of reference to measure voltages. One thing that I really want to know is still about the "all encompassing fluid" that I mentioned. What I want to know is, if we ground one of the poles in order to use that point as a reference, could I take a metre, and stick one end of it inside the earth, 1000 km away from the circuit, and the other end at the higher potential end of the load, and get the same voltage reading as if I had used the initial grounding point that I connected one of the poles to ? Since the earth is continuous, the initial grounding point should "feel" exactly the same as a point 1000km away right?

Thanks for your help. It's immensely appreciated.

 

Being able to source and sink electrons at a local ground, is completely different than flowing electrons thru the ground from separate grounding points.

Electrons moving in and out of ground encounter little resistance. But the resistance thru the ground, to complete the power supply circuit, is variable for many, many reasons.

It has been tried and used in the past. That's why we use a neutral today.

The earth is a good source/sink, but in reference to itself, it is a poor conductor.

Earth is an electrical vertical device (in and out), not a horizontal one (across or thru).

 

Being able to source and sink electrons at a local ground, is completely different than flowing electrons thru the ground from separate grounding points.

Electrons moving in and out of ground encounter little resistance. But the resistance thru the ground, to complete the power supply circuit, is variable for many, many reasons.

It has been tried and used in the past. That's why we use a neutral today.

The earth is a good source/sink, but in reference to itself, it is a poor conductor.

Earth is an electrical vertical device (in and out), not a horizontal one (across or thru).

I didn't mean to complete a circuit through the earth. What I mean is, since we are using the neutral as a reference point, and the neutral is connected to the ground, then the neutral and the earth are equivalent in terms of being a reference point. Therefore, can I spread a wire a long distance away from my circuit, bury the far away end into the earth, and use that as a ground instead? Of course no one would do this but I want to know if that would be equivalent to using the closer neutral/ground reference point ?


you said before that if I connected one end of the metre to the ground and another to the opposite end of the load.... then the voltage should read 0............. so how come it doesnt read zero if you measure it from the neutral to the opposite end of the load? That's because the earth doesnt conduct horizontally, right?

 

Therefore, can I spread a wire a long distance away from my circuit, bury the far away end into the earth, and use that as a ground instead?

Spread a wire from where? I can not understand you. Draw a picture.

 

At 1,000 kM away - you'll encounter a lot of resistance, so, no, you won't be able to use just one wire. But generally speaking, if you have two grounding rods - lets say just 10 meters apart and you have 1/2 of your source going to the load and the other end of the source grounded near by then you SHOULD be able to run a 10 meter wire long enough to test the voltage and should find very little loss. But it depends on how moist the ground is.

They say light travels 186,292 feet per second. But how much is one foot? How long is one second? If you were going to walk to the store and asked "How far is it" and I said it's 16 parsec's" I'll probably get an annoyed look from you. "What the llleh is a 'Parsec?'" you may ask. But if I said it's 3/10 of a mile, now you know. Based on a common frame of reference.

We call ground "Zero volts". But maybe it's really 1.21 gigawatts. Maybe it's trillions of trillions of volts. When you measure your 50 VAC generator you're getting 50 VAC because your point of reference is common ground.

As you can see from my picture, measuring between two common points - you're going to get zero volts (respectively). Suppose you have a battery, the positive terminal is connected to a light bulb. The bulb's other wire is connected to a copper pipe. Now, if you touch your meter probes both to the copper pipe - what voltage will you get? Zero? Yes. But suppose you reverse the connections of the battery and now the positive is connected to the copper pipe and the negative wire is directly wired to the light bulb; what would you get by touching your meter probes both to the copper pipe? Again, zero volts.

Your generator is grounded for safety reasons. If for some reason the case of your appliance (load or whatever) becomes shorted to the high potential. What happens if you touch the case and it's not grounded? You become the path of least resistance to ground. In other words, you get a shock if your source is grounded. That's why it's common to have a hot, neutral AND a ground in your homes electrical circuit. Should the case become hot - you don't die, the power is going somewhere, thus protecting you.

Now, if you use only a two wire cord like a lamp cord and your source is grounded, and you touch one of the wires - guess who's swearing and jerking hands away quickly. Ever leave skin on a screw because you touched something live? I have.

Ground is just that - ground. Whether it's zero volts or 1.21 GigaWatts - or whatever, it's still ground.

 

This is what I mean.......... Are those voltage readings all the same?

 

At 1,000 kM away - you'll encounter a lot of resistance, so, no, you won't be able to use just one wire. But generally speaking, if you have two grounding rods - lets say just 10 meters apart and you have 1/2 of your source going to the load and the other end of the source grounded near by then you SHOULD be able to run a 10 meter wire long enough to test the voltage and should find very little loss. But it depends on how moist the ground is.

They say light travels 186,292 feet per second. But how much is one foot? How long is one second? If you were going to walk to the store and asked "How far is it" and I said it's 16 parsec's" I'll probably get an annoyed look from you. "What the llleh is a 'Parsec?'" you may ask. But if I said it's 3/10 of a mile, now you know. Based on a common frame of reference.

We call ground "Zero volts". But maybe it's really 1.21 gigawatts. Maybe it's trillions of trillions of volts. When you measure your 50 VAC generator you're getting 50 VAC because your point of reference is common ground.

As you can see from my picture, measuring between two common points - you're going to get zero volts (respectively). Suppose you have a battery, the positive terminal is connected to a light bulb. The bulb's other wire is connected to a copper pipe. Now, if you touch your meter probes both to the copper pipe - what voltage will you get? Zero? Yes. But suppose you reverse the connections of the battery and now the positive is connected to the copper pipe and the negative wire is directly wired to the light bulb; what would you get by touching your meter probes both to the copper pipe? Again, zero volts.

Your generator is grounded for safety reasons. If for some reason the case of your appliance (load or whatever) becomes shorted to the high potential. What happens if you touch the case and it's not grounded? You become the path of least resistance to ground. In other words, you get a shock if your source is grounded. That's why it's common to have a hot, neutral AND a ground in your homes electrical circuit. Should the case become hot - you don't die, the power is going somewhere, thus protecting you.

Now, if you use only a two wire cord like a lamp cord and your source is grounded, and you touch one of the wires - guess who's swearing and jerking hands away quickly. Ever leave skin on a screw because you touched something live? I have.

Ground is just that - ground. Whether it's zero volts or 1.21 GigaWatts - or whatever, it's still ground.

Thank you Tony... That's of great help.... You mentioned that if my appliance becomes hot, and my source is grounded, then if I touch the appliance I will get a shock. Is this because current will flow from the appliance through my body, then through the earth until it goes back to the grounded source? But what about the earth resistance? Can current really flow through the earth like that !?!?

 

The green voltage will be a little higher than the blue voltage. The longer the distance from the power supply, that the load is......the higher the green voltage will be, compared to the blue. The green voltage is equal to the load voltage + the voltage drop of the neutral conductor.

The purple voltage could vary a great deal. It will depend on the ground conditions between the generator and the ground connection 50,000 miles away. Not to mention the resistance of the meter lead.

Paulo, You say that you have studied for a few weeks now. You can not study electronics like other subjects.
You have to start at the beginning. If you don't study and learn the basics, you can not proceed.
All further understanding requires a knowledge of the fundamentals.
That means you have to learn dc circuits before ac circuits.
You are still confused. You need to study the relationship between potential, current and resistance first.
Whatever you do, don't play with ac circuits.
Good luck.

edit----corrected.

 

At 1,000 kM away - you'll encounter a lot of resistance, so, no, you won't be able to use just one wire.

Not necessarily, you are using a conductive ball 12,000+ km in diameter, it is unknown.
Max.

 

The green voltage will be a little higher than the blue voltage. The longer the distance from the power supply, that the load is......the higher the green voltage will be, compared to the blue. The green voltage is equal to the load voltage + the voltage drop of the neutral conductor.

The purple voltage could vary a great deal. It will depend on the ground conditions between the generator and the ground connection 50,000 miles away. Not to mention the resistance of the meter lead.

Paulo, You say that you have studied for a few weeks now. You can not study electronics like other subjects.
You have to start at the beginning. If you don't study and learn the basics, you can not proceed.
All further understanding requires a knowledge of the fundamentals.
That means you have to learn dc circuits before ac circuits.
You are still confused. You need to study the relationship between potential, current and resistance first.
Whatever you do, don't play with ac circuits.
Good luck.

edit----corrected.

I have studied DC circuits............. I have studied Ohms laws, Kirchoff's Laws etc.......... I have studied chemistry and Ions........ and I have a degree in maths..........

And still this has caused me a great confusion that I dont know where it comes from ! It comes from me trying to understsnd something that nobody ever explained to me. I am studying this stuff on my own.

Now I understand that you can only measure voltages on a closed circuit......... So the "path" between the source and the 50000 mile ground rod should be looked at as a closed circuit..... Had it been made of Plastic (insulator), the voltage would read 0........ Right ?

 

This brings back memories when I was a boy I ran a roll of 12 -2 to a building that was 500 feet from my house I took the table saw out there and it had so much drop the motor wouldn't start so I got the idea I'd tie the black and white to the hot use the ground on the neutral and drive a ground rod for ground well the saw would run now and it did. Even without the bare copper tied to my new ground. It even worked with the bare wire not hooked anywhere. I was like no way this can't be then I looked outside at how the power lines ran to the house there was a power pole behind the building less then 25 feet of my ground rod and the ground was always wet so I took the ground rod lose and I was back to no saw hooked it up saw ran fine. I learned a lot in that old building I lived to remember it too LOL

 

Paulo, do you understand the difference between a reference point, and a conductor?

Do you understand what resistance is?

What exactly is the point of your question? ARE you asking.....that if we ground one side of a generator...........then measure from hot side of generator........................to ANY point on earth....that we would measure the same potential?

What is your reason to think up these questions. You keep going in circles.

CAN you clearly state the WHY of your questions?