WHAT is the Difference between the expression Earthing and Grounding

[haitham]

hello ..
actually i read in many sites tries to differ between earthing and ground and every one trying to discuss according too his local system

anyway according to american system ,how to supply a consumer i mean how many wires 3L+Neutal+PE or 3L+PEN one neutral and earth in one wire ?

what is the earthing/grounding system used there TNC TNC-S ... ? making rod driven in earth just at transformer side or consumers can build their own rod at their distribution board too ?

what is the terminology used there earthing or grounding ? is there any difference between them in usage or the wire or part which connected to the earth ?

Thank you

 

[mbrooke]

The USA uses a TN-C-S system. TN-S for 480 to 120/208 transformers in buildings. Grounding electrodes are required at the service.

 

[petersonra]

Here in the US we like to confuse things so we use the term grounding to indicate both an actual connection to earth and what the rest of the world calls PE which is really just bonding all the conductive metal parts together that are not normally energized.

As for how many wires are needed, in most cases for a 3 phase service you will need L1,L2,L3, N and G. However sometimes you can make the same wire serve as both N and G at the service end. But you might also need a G that is called a supply side bonding jumper.

A grounding electrode system is always required, but there are different kinds of grounding electrodes allowed besides ground rods.

 

[GoldDigger]

And unlike many other countries we do not require testing of the earth electrode resistance or the Grounding Electrode System (GES) as a whole.
Part of the reasoning behind this is that we do not consider a circuit through the earth as being a valid path for fault current that can be depended upon to open an upstream overcurrent device.

 

[haitham]

Thank you for these information

 

[haitham]

And unlike many other countries we do not require testing of the earth electrode resistance or the Grounding Electrode System (GES) as a whole.
Part of the reasoning behind this is that we do not consider a circuit through the earth as being a valid path for fault current that can be depended upon to open an upstream overcurrent device.

this mean NEC doesn't require as a- must - to test earth resistance ? but how to protect against indirect contact ,touching voltage ?

 

[don_resqcapt19]

this mean NEC doesn't require as a- must - to test earth resistance ? but how to protect against indirect contact ,touching voltage ?

The connection to earth does almost nothing to reduce the shock hazard.

 

[mbrooke]

this mean NEC doesn't require as a- must - to test earth resistance ? but how to protect against indirect contact ,touching voltage ?

Bonding. The current generated during the fault trips the breaker. The reason testing is so important for TT being that current must be high enough to trip the RCD (GFP). In TN-S and TN-C-S that is not a concern as earth resistance will not effect the impedance of the returning fault current.

 

[haitham]

Bonding. The current generated during the fault trips the breaker. The reason testing is so important for TT being that current must be high enough to trip the RCD (GFP). In TN-S and TN-C-S that is not a concern as earth resistance will not effect the impedance of the returning fault current.

yea i got it now it cus system used in us isn't TT , but reducing touching voltage by reducing R fault is important to reduce degree of the shock specially in TT cus R is much higher ..

Still Have question in TC or tcs


in this system I wanna ask about the touching voltage at normal operation for single phase load
where the metallic body of the equipment is connected to neutral which carry the load current in this case ..is there any voltage between the equipment and the earth in this normal operation case .. or due to the very small impedance of the return path from neutral to the grounding supply the voltage will be safe value ? so it depending on the neutral resistance ?
the question is connecting the body to the neutral during normal operation is a safe procedure ?

and related your answer guys above i got that the effective protective device is what is important ..this meaning it would trip even before i feel any pain during direct/indirect contact ?

if so that's why I shocked when I touched neutral line in single phase load ? may be the voltage was much lower than the supply voltage but still unsafe ..and may be the protective device wasn't effective due to setting or bad choice - it was OCD in TT system it had to be RCD ..?

 

[mbrooke]

yea i got it now it cus system used in us isn't TT , but reducing touching voltage by reducing R fault is important to reduce degree of the shock specially in TT cus R is much higher ..

Still Have question in TC or tcs
View attachment 15652

Reducing R will reduce the voltage relative to remote earth, however even if soil R equaled zero, you would still have some voltage to remote earth because the earthing wires have impedance themselves. What matters in any case to the protection of people is the speed at which the supply is disconnected during a fault. IEC 1200-413 Technical Report is a great resource in understanding this. I will post the graph which demonstrates voltage vs time in relation to protecting people.

in this system I wanna ask about the touching voltage at normal operation for single phase load
where the metallic body of the equipment is connected to neutral which carry the load current in this case ..is there any voltage between the equipment and the earth in this normal operation case ..

Yes, there is and always will be voltage between the case and remote earth / other earthed objects in TN-C. This is due to the impedance of the PEN conductor. The more impedance in the PEN conductor the higher the case voltage for any given current flowing.

or due to the very small impedance of the return path from neutral to the grounding supply the voltage will be safe value ? so it depending on the neutral resistance ?

Well, thats highly relative. In most wiring practices the case to earth voltage is small, about a few volts. However, depending on the situation those few volts may be either benign or detrimental. Take gas pumps in the Untied States. The NEC mandates that the neutral conductor be broken when the hot conductor is opened. Why? Because the few volts on the neutral conductor is enough to cause a very small spark to ignite flammable vapors. In Hospitals, where people are undergoing procedures and connected to equipment like EKGs, those few volts going 24/7 can cause great harm to the individual whose body resistance is significantly lowered.

the question is connecting the body to the neutral during normal operation is a safe procedure ?

Well, for something like a home, it is usually safe, but not considered reasonably safe. Those few volts might not harm anyone under normal indoor use of a product, but should the PEN conductor break the case will be live at either 120 or 230 volts relative to earth and everything else. As a result, instead of the appliance simply not working, it becomes a lethal hazard.


In the US, ranges and clothes dryers not used in mobile homes were allowed to connect the metal case to the neutral wire up until 1996. However, after 1996 that changed requiring a separate ground (PE) wire.

and related your answer guys above i got that the effective protective device is what is important ..this meaning it would trip even before i feel any pain during direct/indirect contact ?

Hard to say if you will feel anything or what as I don't know much about the human body and stimulus response, but, its considered the faster an OCPD/RCD/GFCI operates the better.

if so that's why I shocked when I touched neutral line in single phase load ? may be the voltage was much lower than the supply voltage but still unsafe ..and may be the protective device wasn't effective due to setting or bad choice - it was OCD in TT system it had to be RCD ..?

RCDs and GFCI do not protect against electric shock, they protect against electrocution and serious burns. It is still possible to feel a painful shock if say 10ma is passing through your body but its not enough to exceed the 30ma threshold of an RCD. Same can happen with a GFCI, if only 2ma is passing through you it might not trip, but you will still feel something. The idea is that because its not over 5ma, the person can still "let go".


In terms of voltage, if a person's resistance is low enough, a supply as low as 12 volt can pass enough current to hurt. In fact in cases of swimming pools its been documented where just a few volts can result in painful shock.

 

[mbrooke]

yea i got it now it cus system used in us isn't TT , but reducing touching voltage by reducing R fault is important to reduce degree of the shock specially in TT cus R is much higher ..

Still Have question in TC or tcs
View attachment 15652

in this system I wanna ask about the touching voltage at normal operation for single phase load
where the metallic body of the equipment is connected to neutral which carry the load current in this case ..is there any voltage between the equipment and the earth in this normal operation case .. or due to the very small impedance of the return path from neutral to the grounding supply the voltage will be safe value ? so it depending on the neutral resistance ?
the question is connecting the body to the neutral during normal operation is a safe procedure ?

and related your answer guys above i got that the effective protective device is what is important ..this meaning it would trip even before i feel any pain during direct/indirect contact ?

if so that's why I shocked when I touched neutral line in single phase load ? may be the voltage was much lower than the supply voltage but still unsafe ..and may be the protective device wasn't effective due to setting or bad choice - it was OCD in TT system it had to be RCD ..?

Here is the graph I was thinking about. What damage any given current will do flowing through the the human body is governed by two major things: 1. The magnitude of the current; 2. The duration of that current.

The basis of grounding, bonding, GFCI, RCDs and OCPDs in the NEC and IEC: to reduce 1 and 2 for any given electrical installation when a fault does happen.

 

[mbrooke]

This is also essential to the topic at hand imo:

 

[romex jockey]

The NEC grounding terminology has always been disputed. GroundED, GroundING often being confused. The term Neutral finally debuted after a century

I'm unaware of the term 'Earthing' being in the NEC , i can't recall it anywhere , but it would seem to clarify what appears to be an ongoing definitional misunderstanding.

Have there been any rop's to this end?

~RJ~

 

[don_resqcapt19]

The NEC grounding terminology has always been disputed. GroundED, GroundING often being confused. The term Neutral finally debuted after a century

I'm unaware of the term 'Earthing' being in the NEC , i can't recall it anywhere , but it would seem to clarify what appears to be an ongoing definitional misunderstanding.

Have there been any rop's to this end?

~RJ~

We don't need to add the term earthing...we just need to use the term grounding only for conductors that connect directly to a grounding electrode. All of the other conductors in the NEC that use the word grounding are really bonding conductors as they do not connect directly to a grounding electrode.

 

[haitham]

Reducing R will reduce the voltage relative to remote earth, however even if soil R equaled zero, you would still have some voltage to remote earth because the earthing wires have impedance themselves. What matters in any case to the protection of people is the speed at which the supply is disconnected during a fault. IEC 1200-413 Technical Report is a great resource in understanding this. I will post the graph which demonstrates voltage vs time in relation to protecting people.





Yes, there is and always will be voltage between the case and remote earth / other earthed objects in TN-C. This is due to the impedance of the PEN conductor. The more impedance in the PEN conductor the higher the case voltage for any given current flowing.





Well, thats highly relative. In most wiring practices the case to earth voltage is small, about a few volts. However, depending on the situation those few volts may be either benign or detrimental. Take gas pumps in the Untied States. The NEC mandates that the neutral conductor be broken when the hot conductor is opened. Why? Because the few volts on the neutral conductor is enough to cause a very small spark to ignite flammable vapors. In Hospitals, where people are undergoing procedures and connected to equipment like EKGs, those few volts going 24/7 can cause great harm to the individual whose body resistance is significantly lowered.






Well, for something like a home, it is usually safe, but not considered reasonably safe. Those few volts might not harm anyone under normal indoor use of a product, but should the PEN conductor break the case will be live at either 120 or 230 volts relative to earth and everything else. As a result, instead of the appliance simply not working, it becomes a lethal hazard.


In the US, ranges and clothes dryers not used in mobile homes were allowed to connect the metal case to the neutral wire up until 1996. However, after 1996 that changed requiring a separate ground (PE) wire.







Hard to say if you will feel anything or what as I don't know much about the human body and stimulus response, but, its considered the faster an OCPD/RCD/GFCI operates the better.






RCDs and GFCI do not protect against electric shock, they protect against electrocution and serious burns. It is still possible to feel a painful shock if say 10ma is passing through your body but its not enough to exceed the 30ma threshold of an RCD. Same can happen with a GFCI, if only 2ma is passing through you it might not trip, but you will still feel something. The idea is that because its not over 5ma, the person can still "let go".


In terms of voltage, if a person's resistance is low enough, a supply as low as 12 volt can pass enough current to hurt. In fact in cases of swimming pools its been documented where just a few volts can result in painful shock.

really thank you sir for this discussion

 

[haitham]

We don't need to add the term earthing...we just need to use the term grounding only for conductors that connect directly to a grounding electrode. All of the other conductors in the NEC that use the word grounding are really bonding conductors as they do not connect directly to a grounding electrode.

yea they using just grounded vs grounding
grounded conductor the neutral which grounded to earth electrode

grounding conductor the one which connect the equipment to the earth electrode

 

[mbrooke]

We don't need to add the term earthing...we just need to use the term grounding only for conductors that connect directly to a grounding electrode. All of the other conductors in the NEC that use the word grounding are really bonding conductors as they do not connect directly to a grounding electrode.

I agree 100% and this change is long needed. In the IEC terminology such as earthing conductor (or even grounding conductor) to describe a bonding conductor is technically accurate because TT systems make up a very large portion of global power supplies in which the earth is actually used as part of fault clearing. However, under the NEC this system is forbidden making earth or grounding a complete misnomer.

really thank you sir for this discussion

Welcome! If you have any questions always feel free to ask. :thumbsup:

 

[haitham]

In the US, ranges and clothes dryers not used in mobile homes were allowed to connect the metal case to the neutral wire up until 1996. However, after 1996 that changed requiring a separate ground (PE) wire.

Ok sir i got that the more dangerous case in PEC sys hen it opened the full source voltage will appear on the appliances , and i got the point to clear or trip the circuit quickly before the current become more dangerous may be above 10ma ..i got it but i want to back to voltage which will appear on the appliance during normal operation but this time in TC-S system is it like the case of PEC ?

2- for TN-C-S they used additional electrodes at customer side so if the N opened there is another path it converted to TT system where high R resistance fault path ,the voltage will be less than PEC case but still unsafe to pass current according to human R ,is this right ?i know RCD will trip if the current above 30 mA and OCD may not trip ,,but i want ask to say still there is a voltage on the appliance like the case of PEC at normal operation ?

3- do you mean by PE USING TN-S ( 3L+N+PE ) no connecting between chassis and N but with PE ,so during normal operation there isnt any voltage ,and there isnt any other additional electrodes at customer , the fault path through PE is effective .
the worst problem will appear if PE is opened ?

always thank you Sir(s) for your time

 

[mbrooke]

Ok sir i got that the more dangerous case in PEC sys hen it opened the full source voltage will appear on the appliances , and i got the point to clear or trip the circuit quickly before the current become more dangerous may be above 10ma ..i got it but i want to back to voltage which will appear on the appliance during normal operation but this time in TC-S system is it like the case of PEC ?

In TN-C-S this case voltage will be lower since only the impedance of the utility neutral is involved instead of the utility neutral + the branch circuit neutral.


However, when everything is bonded together in a building, this voltage will actually be zero relative to other bonded appliances/metal objects (such a plumbing pipes) in the same building. However, the voltage to remote earth will still be present. I might get zero volts between my sink and stove, but 1/2 a volt between my outdoor water spigot and earth soil.

2- for TN-C-S they used additional electrodes at customer side so if the N opened there is another path it converted to TT system where high R resistance fault path ,the voltage will be less than PEC case but still unsafe to pass current according to human R ,is this right ?

Well, it depends on what those electrodes are and their resistance. A typical 8 foot ground rod or plate usually does nothing significant. An underground metal water pipe which forms a continuous metallic path with neighboring buildings which also have their neutral bonded to the incoming water supply (as common in urban US areas) will completely mask an open utility neutral resulting in no significant voltage rise to remote earth.


In the NEC there is no requirement that earthing/grounding electrodes act as a backup neutral.

i know RCD will trip if the current above 30 mA and OCD may not trip ,,but i want ask to say still there is a voltage on the appliance like the case of PEC at normal operation ?

During an open utility neutral the RCD will not trip, no matter how sensitive. All current flowing in and out of the appliance will go through the RCD, into the panel, and then through the PEs.

3- do you mean by PE USING TN-S ( 3L+N+PE ) no connecting between chassis and N but with PE ,so during normal operation there isnt any voltage ,and there

Yes.

isnt any other additional electrodes at customer , the fault path through PE is effective .
the worst problem will appear if PE is opened ?

always thank you Sir(s) for your time

Under the NEC grounding electrodes are required regardless of TN-C-S or TN-S. I know in some IEC countries grounding electrodes are skipped for none TT supplies, but not in the NEC. The idea is that grounding electrodes help mitigate/reduce the damage from lightning strikes regardless of TN-C-S or TN-S. In the NEC they have nothing to do with mitigating the risk of an open neutral.


IF I may ask, what are the requirements for TN-C-S and TN-S in your country with grounding electrodes?


Now, if the PE is opened, if a fault occurs it will not trip the OCPD. If the PE break is between an RCD and the faulted appliance, the RCD is intended to be the last resort to prevent electrocution.

 

[mbrooke]

Ok sir i got that the more dangerous case in PEC sys hen it opened the full source voltage will appear on the appliances , and i got the point to clear or trip the circuit quickly before the current become more dangerous may be above 10ma ..i got it but i want to back to voltage which will appear on the appliance during normal operation but this time in TC-S system is it like the case of PEC ?

2- for TN-C-S they used additional electrodes at customer side so if the N opened there is another path it converted to TT system where high R resistance fault path ,the voltage will be less than PEC case but still unsafe to pass current according to human R ,is this right ?i know RCD will trip if the current above 30 mA and OCD may not trip ,,but i want ask to say still there is a voltage on the appliance like the case of PEC at normal operation ?

3- do you mean by PE USING TN-S ( 3L+N+PE ) no connecting between chassis and N but with PE ,so during normal operation there isnt any voltage ,and there isnt any other additional electrodes at customer , the fault path through PE is effective .
the worst problem will appear if PE is opened ?

always thank you Sir(s) for your time

This is interesting and may give you a good visual. Starting at 20:42, a TN-C-S supply with the utility neutral disconnected is tested for touch potential in relation to grounding electrode resistance and load levels.



https://www.youtube.com/watch?v=Yg6G5VUSsWA



The less load and the lower the grounding electrode resistance the less voltage relative to remote earth. Keep in mind that in this case the ground rods Mr. Holt has driven both in quantity and depth are well above what is normally required in the NEC as the minimum.