Using The Nuetral Line As The Earth/grounding

[Pilchard]

dhrobertson, as you said the pole outside with the transformer does have an earth embeded at the base.

As far as i can see this is attached to the body of the transformer.

On the other side of the pole is an embeded nuetral grounding that runs up to the overhead nuetral.

Putting an LED screw driver on the neutral at the pole base shows positive for voltage.

A multi meter between the embeded earth and embeded neutral at the base of the pole reads 225 volt.

I guess this means the problem could be coming from anywhere in the street.

Now I have to try and get the power company interested enough to come out.

[elkangorito]

dhrobertson, as you said the pole outside with the transformer does have an earth embeded at the base.

As far as i can see this is attached to the body of the transformer.

On the other side of the pole is an embeded nuetral grounding that runs up to the overhead nuetral.

Putting an LED screw driver on the neutral at the pole base shows positive for voltage.

A multi meter between the embeded earth and embeded neutral at the base of the pole reads 225 volt.

I guess this means the problem could be coming from anywhere in the street.

Now I have to try and get the power company interested enough to come out.

I'd be interested to see what this 'embeded earth and embeded neutral' voltage is if the power for your whole block (combined establishements) is turned off.

But this is not solving the problem. What NEEDS to be done at your establishment, is an active/neutral continuity test, an insulation resistance test & a ground fault loop impedance test. These tests need to be conducted whilst the installation is de-energised at each main distribution board. These tests will absolutely reveal any dangerous faults in the installation.

Of course, none of these tests are ever conducted in THailand, which could easily explain all the mishaps & potential mishaps.

Also, installing MEN/PEN systems is NOT a straight forward procedure. Most Thais haven't even heard of an MEN/PEN system so I would strongly recommend against this unless your combined establishments have been inspected by a knowledgeable person? I'm an advocate of such systems BUT I also highlight the "required detail" that surrounds such installations. The MEN/PEN systems are the sorts of things that are "easier said than done".

Yes Pilchard, get the power company then let us know how you get on. Good luck.

[chownah]

Clearly the earthing is defective. The most likely would be the earthing for the neutral. Can you run a light bulb between the earth and neutral at the base of the pole? Is it possible that if you work things the right way you could get free power out of this entanglement?

Chownah

P.S. The discussion has sort of gotten around to a previous comment of mine about ALL neutrals in any properly constructed power supply system being grounded (earthed) at some place on the circuit. The reply was that in some countries they are not. It seems to me that if a conductor in a power distribution system is not grounded then it can not be called a neutral....consider. An simple alternator has two output wires and if neither of them is grounded then they can both be considered hot....there is really no way to differentiate between them based on examining the current flows....neither is neutral. If, however one of the output wires is grounded (earthed) and all along the circuit this conductor is grounded periodically then this conductor is a neutral...it will read approximately zero volts between it and a ground wire (earth) which is not directly connected to the distribution system.. Is this correct?

Chownah

PPS OOOps, I just thought of something about the construction of alternators that makes me think that I am wrong but I'll leave my comment and hope to learn something here.

Chownah

Edited December 20, 2006 by chownah

[elkangorito]

Clearly the earthing is defective. The most likely would be the earthing for the neutral. Can you run a light bulb between the earth and neutral at the base of the pole? Is it possible that if you work things the right way you could get free power out of this entanglement?

Chownah

P.S. The discussion has sort of gotten around to a previous comment of mine about ALL neutrals in any properly constructed power supply system being grounded (earthed) at some place on the circuit. The reply was that in some countries they are not. It seems to me that if a conductor in a power distribution system is not grounded then it can not be called a neutral....consider. An simple alternator has two output wires and if neither of them is grounded then they can both be considered hot....there is really no way to differentiate between them based on examining the current flows....neither is neutral. If, however one of the output wires is grounded (earthed) and all along the circuit this conductor is grounded periodically then this conductor is a neutral...it will read approximately zero volts between it and a ground wire (earth) which is not directly connected to the distribution system.. Is this correct?

Chownah

PPS OOOps, I just thought of something about the construction of alternators that makes me think that I am wrong but I'll leave my comment and hope to learn something here.

Chownah

Sorry about this Chownah but you have made a slight error.

The neutral conductor in your home is so called because it is the 4th wire in a 3 phase system. In effect, it is the return path to the distribution transformer, for any "out of balance" current arising from the 3 phases. For a perfectly balanced load (a 3 phase motor), a neutral is not required because there is no "out of balance" current.

In your home where you are using 1 of the 3 phases, you will therefore create an out of balance condition with the 3 phase supply. As a consequence, a neutral is required.

The neutral in a 3 phase 4 wire system is not live. It is the return "out of balance" current path to the star point of the distribution transformer.

This same principle does not apply to a portable single phase generator, in which both conductors will be active. However, single phase generators are uncommon, costly & inefficient compared to a 3 phase portable generator so your portable generator is most likely a 3 phase unit & you are only using 1 of the phases & the neutral.

Earthing the neutral does not affect it in any way. This merely helps to provide a lower impedance return path to help trip the protective devices.

[chownah]

Earthing the neutral does not affect it in any way. This merely helps to provide a lower impedance return path to help trip the protective devices.

For an unbalanced load (which means virtually all of the time for all residential applications) doesn't the earthing lower the voltage on the neutral? That is to say that if there were NO earthings ANYWHERE on the neutral line all the way back to the generator (I'm assuming that the neutral line goes all the way back to the generator, does it?) the neutral line would (under unbalanced load conditions) have a much higher voltage than it would have with earth connections liberally applied?

Chownah

Edited December 21, 2006 by chownah

[elkangorito]

Earthing the neutral does not affect it in any way. This merely helps to provide a lower impedance return path to help trip the protective devices.

For an unbalanced load (which means virtually all of the time for all residential applications) doesn't the earthing lower the voltage on the neutral? That is to say that if there were NO earthings ANYWHERE on the neutral line all the way back to the generator (I'm assuming that the neutral line goes all the way back to the generator, does it?) the neutral line would (under unbalanced load conditions) have a much higher voltage than it would have with earth connections liberally applied?

Chownah

Earthing the neutral does not necessarily lower the voltage on the neutral. All earthing will do is put the neutral conductor at the same potential as the earth conductor, since the earth is now forming a part of the neutral return circuit.

Also, high voltages to earth measured against a neutral are not always the result of current flowing through the neutral. High neutral-earth voltages can be the result of harmonics, a break in the neutral, a high resistance neutral connection or induction.

[chownah]

Earthing the neutral does not necessarily lower the voltage on the neutral. All earthing will do is put the neutral conductor at the same potential as the earth conductor, since the earth is now forming a part of the neutral return circuit.

I'm having a problem understanding this. The earth (the dirt upon which we stand) is used as a reference for measuring voltages. If we say that the neutral has a voltage of zero then we are saying that it has the same electrical potential as the earth....I believe that this is correct. If you have "neutral" wire that has an electrical potential higher than what the ground has then there is a voltage difference between the "neutral" wire and the earth...and...if you connect a conductor between the "neutral" wire and the earth then a current will flow. If the voltage difference between the "neutral" wire and the earth does not decrease when this conductor is connected then we say that the voltage in the "neutral" wire has not been lowered......but......if it is the case that the voltage is not lowered then you will have a good source of power....this is like a generator whose function is to maintain a certain voltage difference between its two terminals.

If there is a "neutral" wire that has a voltage above the earth that will maintain its voltage when connected to the earth then you should be able to use it as a power source......it seems unlikely to me that this would be the case.

Chownah

P.S. When looking at the conductors running between power pole along a road there is often one conductor which has no insulation.....is this the neutral?......and if so then why do they have no insulation?......my view is because there should be only a small voltage difference between the bare wire and the ground and this is maintained by having conductors running from the bare wire to the ground periodically because any conductor running from a neutral to the ground would have the effect of lowering the voltage of the neutral with respect to the ground at the location where the conductor contacts the ground. I'm wondering if my thinking is wrong here.

Chownah

[autonomous_unit]

The inductance and resistance he speaks of are important. The Earth is not all at one potential! You can often sink a few ground stakes and measure a voltage across them. Soil itself can be an inductor, capacitor, or battery because of the various mineral components, moisture levels, acidity, etc.

You really have to choose the boundaries of your system and then consider all the paths within the circuit, i.e. a house. That is why isolation is so important with paths that go in and out of the system, e.g. a telephone line or even a shield on some RF line that goes from one structure to another may close an earth loop and draw a dangerous amount of current.

[elkangorito]

I'm having a hard time thinking of how dust on or around an appliance could cause a neutral to earth voltage....can you give a scenerio?

Doesn't the term "neutral" indicate that at some place in the overall circuit (all the way back to the generator perhaps) the wire is earthed?

Chownah

In a 4 wire 3 phase distribution system it is called "neutral" because it does not supply any voltage & it is the "neutral point" of a star connection. The phasor sum of the currents in a 3 ph balanced load at this "neutral point" is zero.

The name "neutral" has nothing to do with the earth or earthing.

[southerndog]

I haven't read this whole thread, but I just wanted to say that I almost got KILLED taking a shower in my house.. The box wasn't probably grounded, etc.. I came very close to dying from the electric current that went through me.. I couldn't get off the current. Scariest moment of my life.

I write this to recommend that you all take these things VERY seriously.

[elkangorito]

I haven't read this whole thread, but I just wanted to say that I almost got KILLED taking a shower in my house.. The box wasn't probably grounded, etc.. I came very close to dying from the electric current that went through me.. I couldn't get off the current. Scariest moment of my life.

I write this to recommend that you all take these things VERY seriously.

You may find this site interesting.

http://www.crossy.co.uk/wiring/

[chownah]

In a 4 wire 3 phase distribution system it is called "neutral" because it does not supply any voltage & it is the "neutral point" of a star connection. The phasor sum of the currents in a 3 ph balanced load at this "neutral point" is zero.

Thanks for this....it helps me to clarify my thinking.

Now, consider a neutral wire that is at 100 volts relative to the reference voltage of zero at the ground. Let's connect the neutral to the ground using a very good earthing rod and 100 metres of 8 square mm copper wire which would have a resistence of about 0.067 ohm. You claim that this might not lower the voltage on the neutral...so let's go with that...there is no voltage drop at the neutral. Let's also assume that the voltage of the ground at our earthing rod also is not raised by this connection....then....by E=IR we get E=70v, R=0.067 ohm and solving for I we get I=1,044 amps approximately....I think this would vaporize the wire. My point is that if a neutral wire has a voltage relative to the earth then connecting an earth wire will likely lower the voltage on the neutral....aren't neutrals supposed to be earthed?...on all properly designed and constructed public power distribution systems in the real world?

Chownah

[chownah]

I haven't read this whole thread, but I just wanted to say that I almost got KILLED taking a shower in my house.. The box wasn't probably grounded, etc.. I came very close to dying from the electric current that went through me.. I couldn't get off the current. Scariest moment of my life.

I write this to recommend that you all take these things VERY seriously.

I use a gas water heater...there is some danger from the gas but it makes me totally in control of the elements which might be dangerous and I make sure that all is in proper working order. Having the same assurance of everything being in proper working order is much more difficult with electrical appliances in Thailand given the uncertainty of domestic wiring and even of the distribution system..

Chownah

[elkangorito]

In a 4 wire 3 phase distribution system it is called "neutral" because it does not supply any voltage & it is the "neutral point" of a star connection. The phasor sum of the currents in a 3 ph balanced load at this "neutral point" is zero.

Thanks for this....it helps me to clarify my thinking.

Chownah, my comments in blue. But before I continue, let's assume that the system we are talking about is a system whereby the neutral is supposed to be earthed at regular intervals throughout the distribution system, for the sole purpose of reducing the impedance of the return current path of each distribution transformer. Under a 'fault' condition, this will cause more current to flow through protective devices like CB's & fuses (faster trip times), & therefore adds to the safety of the system.

Now, consider a neutral wire that is at 100 volts relative to the reference voltage of zero at the ground. If there is 100 volts N -E, then there is a problem with the system. Most likely a bad or broken neutral or earth connection. Let's connect the neutral to the ground using a very good earthing rod and 100 metres of 8 square mm copper wire which would have a resistence of about 0.067 ohm. You claim that this might not lower the voltage on the neutral...so let's go with that...there is no voltage drop at the neutral. Let's also assume that the voltage of the ground at our earthing rod also is not raised by this connection....then....by E=IR we get E=70v, R=0.067 ohm and solving for I we get I=1,044 amps approximately....I think this would vaporize the wire. Yes, it would vapourise the wire because the neutral/earth system is faulty (providing that the supply txer could supply such a high current & the circuit impedance is low). Current will flow under these conditions because of the fault. Yes, THIS system is supposed to earth the neutral & YES, connecting a wire under a fault condition like the one you describe, will 'vapourise' the wire....but this is because of a fault. Fix the fault & this scenario disappears. My point is that if a neutral wire has a voltage relative to the earth then connecting an earth wire will likely lower the voltage on the neutral The connection of neutral to earth will put the neutral at the same potential as the earth (whatever that is).....aren't neutrals supposed to be earthed?...on all properly designed and constructed public power distribution systems in the real world? No. Some systems do not bond the neutral with earth (eg the IT network).

Chownah

Edited December 22, 2006 by elkangorito

[chownah]

In a 4 wire 3 phase distribution system it is called "neutral" because it does not supply any voltage & it is the "neutral point" of a star connection. The phasor sum of the currents in a 3 ph balanced load at this "neutral point" is zero.

Thanks for this....it helps me to clarify my thinking.

Chownah, my comments in blue. But before I continue, let's assume that the system we are talking about is a system whereby the neutral is supposed to be earthed at regular intervals throughout the distribution system, for the sole purpose of reducing the impedance of the return current path of each distribution transformer. Under a 'fault' condition, this will cause more current to flow through protective devices like CB's & fuses (faster trip times), & therefore adds to the safety of the system.

Now, consider a neutral wire that is at 100 volts relative to the reference voltage of zero at the ground. If there is 100 volts N -E, then there is a problem with the system. Most likely a bad or broken neutral or earth connection. Let's connect the neutral to the ground using a very good earthing rod and 100 metres of 8 square mm copper wire which would have a resistence of about 0.067 ohm. You claim that this might not lower the voltage on the neutral...so let's go with that...there is no voltage drop at the neutral. Let's also assume that the voltage of the ground at our earthing rod also is not raised by this connection....then....by E=IR we get E=70v, R=0.067 ohm and solving for I we get I=1,044 amps approximately....I think this would vaporize the wire. Yes, it would vapourise the wire because the neutral/earth system is faulty (providing that the supply txer could supply such a high current & the circuit impedance is low). Current will flow under these conditions because of the fault. Yes, THIS system is supposed to earth the neutral & YES, connecting a wire under a fault condition like the one you describe, will 'vapourise' the wire....but this is because of a fault. Fix the fault & this scenario disappears. My point is that if a neutral wire has a voltage relative to the earth then connecting an earth wire will likely lower the voltage on the neutral The connection of neutral to earth will put the neutral at the same potential as the earth (whatever that is).....aren't neutrals supposed to be earthed?...on all properly designed and constructed public power distribution systems in the real world? No. Some systems do not bond the neutral with earth (eg the IT network).

Chownah

Is the IT network a public power distribution system? Do all properly designed and constructed public power distribution systems in the real world have the neutral wire earthed? (I'm assuming that the IT network is not a public power distsribution system.) I'm talking about the systems that are created to provide power to residences.

I think that you are agreeing with me that in general adding a conductor between a neutral wire and the earth will lower the voltage of the neutral relative to the earth with the earth being the reference point (zero volts reference).

Chownah

[oxymoron]

Chownah, Elkangorito

Enjoy reading your exchange a lot. Just one point I would offer though Bonding of the Power Authority and the Telstra Telecommunications earth in Australia is mandatory. The short answer is that it has to do with Earth Potential Rises (EPR) caused by lightning and other odd things such as you are currently discussing. The long answer might be a subject of another day.

[chownah]

Chownah, Elkangorito

Enjoy reading your exchange a lot. Just one point I would offer though Bonding of the Power Authority and the Telstra Telecommunications earth in Australia is mandatory. The short answer is that it has to do with Earth Potential Rises (EPR) caused by lightning and other odd things such as you are currently discussing. The long answer might be a subject of another day.

I have heard of a thing called an "equipotential zone". The idea is that if all of the water pipes, gas pipes, metal air duct runs, appliances, etc. that are found in a room or apt. or house are all connected together (at the panel) and this is connected to the earthing rod then they will all be at the same potential (whatever the earthing rod is providing) and so there would be no voltage difference between these items and thus no possibility of receiving a shock. Does it seem to you that this requirement in Australia is reasoned out along these same lines?

Chownah

[backflip]

Equipotential or not, if you connect ground to neutral, you're risking electrocution. A good method to provide a "ground" is to use metal water pipes. If you connect neutral to ground, the water pipes become a part of the electrical circuit. That is, if the circuit is "hot", the water pipes will be hot...and everything that contacts the water pipes will be hot...including the faucets and knobs - and people try to insulate the faucets using teflon tape at the water pipe! There have been several instances, in Thailand, where a homeowner or ignorant electrician has connected neutral and ground. As the lawn got wet, it became electrically hot. Then, as a person touched the lawn, and a metal portion of the home - cleaning the window frame, as an example - the person was electrocuted.

The "ground" is meant to disperse an electrical charge in an emergency - a wiring fault, for example. It is not meant to complete an electrical circuit for an ordinary happenstance.

[oxymoron]

Chownah, Elkangorito

Enjoy reading your exchange a lot. Just one point I would offer though Bonding of the Power Authority and the Telstra Telecommunications earth in Australia is mandatory. The short answer is that it has to do with Earth Potential Rises (EPR) caused by lightning and other odd things such as you are currently discussing. The long answer might be a subject of another day.

I have heard of a thing called an "equipotential zone". The idea is that if all of the water pipes, gas pipes, metal air duct runs, appliances, etc. that are found in a room or apt. or house are all connected together (at the panel) and this is connected to the earthing rod then they will all be at the same potential (whatever the earthing rod is providing) and so there would be no voltage difference between these items and thus no possibility of receiving a shock. Does it seem to you that this requirement in Australia is reasoned out along these same lines?

Chownah

Chownah,

Yes you are right both about the concept of "equipotential zones" and us figuring it out about 35 years ago when I was a Senior Design Engineer specialising in research into the effects of lightning on Telecommunications infrastructure. Contrary to poular belief lightning does not come into your premises and cause damage to your IT gear, actually "current" (amps) leave your premises causing the damage. PM me if you want this story, so we dont get off this extremely important topic.

backflip, sorry to disagree but you are not correct. Here and in Australia every correctly wired installation has the Neutral and Earth bonded in the Main Distribution Box. If you read the very detailed and excellent reports by 'Crossy' and 'Elkangorito' earlier on in this thread you will see why.

Finally I would offer strong support to Crossy's expose on earthing. Just because you have 1.5 or 2m of earth stake does not mean you have a good (5 ohm is usually accepted for power) earth. In fact where I am in Northern Thailand you do not in the "hot" season. This is because of the soil being what we used to call "refractive clay". Look at a rice paddy when it has dried out. Because of this my wifes house ( not mine of course ) but I designed ,built, electrically wired and plumbed it to Australian Standards 18 years ago, has 3 earth stakes around the septic tank and 8mm square earth cable that bond the power and the steel roof structure.

[dhrobertson]

In general, all electricity supply systems have neutral bonded to ground at the transformer. IT systems are the exception but these are rare. Sometimes these are used for circuits in hospitals supply life support sytems or some some local generator systems. For the purposes of this thread you can assume that neutral is bonded to ground.

An open neutral creates a dangerous situation where all parts of the system can float at the supply voltage. This is why we have PME (ptotective multiple earthing) which means neutral is tied to ground at several points along the line.

The main reason for bonding neutral to ground at the incoming point or origin of the installation is to reduce the external ground fault loop impedance and speed up the time it takes for a standard breaker to trip. In Thailand it is difficult to obtain type B breakers and most installations only have type C. Type C breakers require about 10x rated current to trip near instantaneously. Consider this: a 32A type C MCB requires 320A to trip quickly in the case of a solid ground fault. That means a total loop impedance of max 0.68 ohms. This is impossible relying on a ground stake as part of the circuit.

The grounding system for an installation really has two purposes. One is to tie all exposed conductive parts to the earth at the reference voltage 0V. The second purpose is to ensure rapid disconnection of the supply to a circuit in the case of a ground fault.

Here in Thailand, having a suitable ground system is no guarantee of safety. Often appliances which must be connected to ground are supplied with a european style plug. These are the ones with a female ground contact and contacts at the side. In France, socket outlets have a male ground pin. in Germany, sockets can be recessed with ground contacts at the side. Here in Thailand, no contact is made. It is up to you to make these things safe by fitting a ground pin adaptor available from Homepro or fitting a standard 3 pin plug. the other favorite here is the availability of extension cables with 3 pin sockets but a 2 core cable and 2 pin plug. Bizzare. Finally we have the imported appliances such as refigerators where the importer replaces the 3 core cable with a 2 core and expects you to supply a ground lead!

Meanwhile, back at the neutral....

If you have more than a few volts on the neutral there is certainly a fault.

Trying to calculate currents in the way discussed is unrealistic. You have to consider the internal impedance of the source.

[dhrobertson]

Just read the piece from Backflip. Sorry to say this is completely incorrect.

Where supplies do not have a separate earth (historically, the steel armour of a cable was used as a separate erth), the neutral is used a combined protective earth and neutral called a PEN.

Concerning main ground conductors (from the neutral bus to the ground electrod(s). The size should be not less than 50% of the incoming PEN or neutral and should not be less than 6mm2 in any case.

Ground rods should be 10 feet long, 5/8 inch diameter copper clad. I usually use 3 in a triangular array. It is VERY difficult to get less than 5 ohms. Avoid the copper plated rods as the copper will be gone in no time. I predder compression joints to exothermic welds but that's just my opinion. You can use bare copper wire but I preffer to use THW to reduce corrosion and give additional mechanical protection.

[elkangorito]

From the information that I gathered from my learned Thai electrical colleagues, the Thai electrical system is supposed to be TT (the consumers earth is provided by a local earth stake, which is independent of the earth connection at the transformer star point.)

The problem is that it seems that this system is only partially implemented (did they just 'forget' to do the rest?), which will cause almost all of the problems that people have with their electrical supply.

Now the other biggest & most dangerous problem is when a person reads something about earthing, they then proceed to "do their own thing", without realising the consequences of their actions.

All of the necessary information about how to earth the neutral at the consumers board (MEN connection) & install an earth stake, is available on Crossy's website ( www.crossy.co.uk/wiring ). If somebody should want the topics on this website as individual 'papers', contact me & I will supply them.

Australian wiring standards (AS NZ 3000:2000 which very closely fit into the Thai elec. system & weather/temperature conditions), indicate that equipotential bonding shall be used throughout an installation. Most of this is achieved through the 3 wire power circuits (A+N+E) but a separate earth conductor is obviously required for gas, water & any other external conductive media.

I agree with dhrobertson....when bonding the main earth conductor of an installation to the main earth rod, I prefer mechanical clamping over welding/soldering.

The resistance to earth should be less than 1 ohm (AS NZ 3000:2000 specifies 0.5 ohms).

Having multiple earth stakes can be dangerous if incorrectly installed therefore most supply authorities allow only 1 main earth electrode per installation, which MUST achieve the required minimum resistance/impedance.

In summary (& in Thailand); the supply neutral is supposed to be bonded to the main earth electrode at an installation, via an MEN link.

This prescribed method for achieving this is available at www.crossy.co.uk/wiring or by myself.