Main Earthing Conductor and Earthing System question.

[Deleted member 26818]

I was thinking to compare this Ze with line to neutral impedance.

Nah, just guess it.

 

[Nigel]

PME conditions can apply to TN-S.

Please explain what ypu mean by “PME conditions”?

 

[Deleted member 26818]

Please explain what ypu mean by “PME conditions”?

PME (Protective Multiple Earthing) is used where a network is configured as TN-C (earth and Neutral combined).
It’s primary purpose is to keep the difference in potential between the combined earth and neutral and the general mass of the earth as close to zero as possible.

One of the ‘conditions’ associated with PME systems is that neutral current from other installations will be present on earthing and bonding conductors in a particular installation.
Hence the requirement for larger CSA bonding conductors.

Older networks configured as TN-S are being changed to TN-C.
Whilst installations may be presented with TN-S, the bulk of the network is TN-C with PME.

When conducting a periodic inspection on an installation which is presented as TN-S, the Inspector should determine whether PME conditions apply and whether the CSA of bonding conductors is adequate.
One method to determine this is to measure the Ze.
A Ze close to or below the typical value for a TN-C-S system would suggest PME conditions apply.
A further test would be to compare the values for PSSC and PEFC.

 

[Nigel]

PME (Protective Multiple Earthing) is used where a network is configured as TN-C (earth and Neutral combined).
It’s primary purpose is to keep the difference in potential between the combined earth and neutral and the general mass of the earth as close to zero as possible.

One of the ‘conditions’ associated with PME systems is that neutral current from other installations will be present on earthing and bonding conductors in a particular installation.
Hence the requirement for larger CSA bonding conductors.

Older networks configured as TN-S are being changed to TN-C.
Whilst installations may be presented with TN-S, the bulk of the network is TN-C with PME.

When conducting a periodic inspection on an installation which is presented as TN-S, the Inspector should determine whether PME conditions apply and whether the CSA of bonding conductors is adequate.
One method to determine this is to measure the Ze.
A Ze close to or below the typical value for a TN-C-S system would suggest PME conditions apply.
A further test would be to compare the values for PSSC and PEFC.

This is a great copy and paste describing why a TNC-S is not always a PME.

It still does not explain how a TN-S can have ‘PME conditions’.

 

[Deleted member 26818]

This is a great copy and paste describing why a TNC-S is not always a PME.

It still does not explain how a TN-S can have ‘PME conditions’.

Not sure whether I should be flattered or insulted, that you believe my post is copied and pasted?
When taken into consideration with the fact that you deliberately misconstrue it’s intent, I can only assume it’s a puerile attempt at insulting me.

In any event, I have attempted to educate and inform you, as per your request.
I suggest you either take it on board, or remain in blissful ignorance.

 

[mhar]

Almost every time an underground joint is made it is earthed, often by just burying bare conductor but sometimes by a rod with (often bare) conductor crimped to it. A tns supply that has had multiple joints will have multiple earthing points so you can be presented with a supply that looks like tns but has Protective Multiple Earthing along it's route

 

[westward10]

You judge the system on how it enters the building.

 

[Nigel]

Not sure whether I should be flattered or insulted, that you believe my post is copied and pasted?
When taken into consideration with the fact that you deliberately misconstrue it’s intent, I can only assume it’s a puerile attempt at insulting me.

In any event, I have attempted to educate and inform you, as per your request.
I suggest you either take it on board, or remain in blissful ignorance.

I am honestly not trying to insult you. Not at all.

However all you have posted is the reason why a TNC-S is not always a PME.

It goes nowhere near explaining when a TN-S has PME conditions.

What it does say is that sometimes when presented with a TN-S it may actually be a PME. But this is not a TN-S then is it?

 

[Nigel]

Almost every time an underground joint is made it is earthed, often by just burying bare conductor but sometimes by a rod with (often bare) conductor crimped to it. A tns supply that has had multiple joints will have multiple earthing points so you can be presented with a supply that looks like tns but has Protective Multiple Earthing along it's route

Would those joint earths be linked to the neutral?

 

[Midwest]

This is better than Jeremy Kyle.

I was told by one DNO engineer, I could convert 'my' TNS supply at a property to PME (i.e. do it myself), 'cos its probably been 'PME'd' in the street, or down the road somewhere anyway.

Didn't take up the suggestion.

 

[mhar]

Would those joint earths be linked to the neutral?

Sorry son doesn't know on a tns, yes on tncs. He works more on the hv distribution side