Swimming Pool Installation
- Thread starter gselectrical
- Start date
Help Support Talk Electrician Forum:
and in a single install proper PME where exactly are the currents diverted from?
how can you divert your own currents onto your own system?
Well when you loose your neutral because of the pme link, some or all of the current may divert through what ever is connected to your met. If you copper water and gas pipe has a Resistance to earth of 1 ohm and the broken supply is much higher the majority of current diverts. Simple
as for the resistance to cne the rods are required to be, well, thats a DNO issue we have no bearing on.
BTW, it wont go anywhere if you lose the neutral at the head, not unless you have a proper PME , even then, it will depend where your last DNO rod is terminated.
this is why I advocate the use of localised PME where possible.
this is why I advocate the use of localised PME where possible.
Hope ive answered your question's. Look forward to your replyHow can a single cable from a Tx to a single consumer be "conventional" "PME"?
So TN-C-S is defined by the number of consumers connected, i dont think so!!
Please explain, in detail.
Whats to explain? What dont you understand?
The Tx electrode is that at the Tx, thus the Star point earth for the Tx.
Not necessarily at the TX, but ill go along with that.
Even IF the DNO drop rods along the SINGLE supply cable from the Tx, this would not make it a PME supply requiring all of the safeguards of "normal" PME as there would be NO possibility of diverted N currents.
Ok, so we have a Dy11from there we have a CNE which is connectred to earth at 2 points or more, if the Pen was to break the current in the consumers install would divide and divert, why do you think we rod the CNE? THE DIVERTED NEUTRAL CURRENT FROM THE INSTALLATION WILL FLOW THROUGH THE INSTALLATIONS MAIN PROTECTIVE BONDING TO EARTH 'T' AND THEN TO THE SOURCE.
1 Tx, 1 Consumer, where can the diverted N currents come from?
From within
Why TT something when you have a perfectly good very low impedance DNO earth?
Im not saying i would, explain your purpose of an additioal electrode and why you feel the Ra is not of to much importance
What are the chances of a broken PEN, risk assessment?
Slim
Also, you need to be careful to understand the subtleties of PME & PME & TN-C-S.
I am aware of them.
Finally for now, got to dash of for a few minutes, it is not definite that the supply is actually TN-C-S, I recently worked on an install "out in the sticks" and I don't do much domestic, that was a pole mount Tx 11kv/400V, which appeared to be TN-C-S, but upon careful checking was actually TN-S, not immediately easy to spot due to the install methods used by the DNO.
Did you ask the design engineer what type of System Earthing was in place?
Last edited by a moderator:
Ok, which standard are you refering to? So again what requirment is in place with regard to the resistance to earth of the electrodes along the CNE and at which points do the electrodes need to be placed?
So if the last Point on the CNE had a Electode at 50 ohms and a break occurs upstream, your house has Extraneous conductive Parts with a resistance of 5 ohms, do you really think the current goes nowhere?
Thats because andrewedwardjudd, woops i mean chr!s is trolling you & the more you bite ?
Troll LMFAO
Well your more than welcome to debate the points raised if you know better, the only contentious issue is that to which sidewinder was angleing too, that of PNB and the Neutral Bond Position which actually presents itself as TN-S, but thats another story.
I will reply in the same manor as other's, if they want to be rude and patronising then so will I!!!
Sidewinder will answer himself when he looks into the purpose of the additional electrode on a PME, why the Ra is important and what current it is that becomes a danger upon a broken PEN, GN5 has a section on it, have a look you may learn something
gselectrical
Well-known member
- Joined
- Oct 13, 2009
- Messages
- 627
- Reaction score
- 0
Thanks for all the points made. Interesting read. I for one am certainly learning as I am sure others are too.
Cheers
GS
Cheers
GS
Last edited by a moderator:
Well its been a very interesting read I must say, almost action packed :Applaud :ApplaudTroll LMFAO
Well your more than welcome to debate the points raised if you know better, the only contentious issue is that to which sidewinder was angleing too, that of PNB and the Neutral Bond Position which actually presents itself as TN-S, but thats another story.
I will reply in the same manor as other's, if they want to be rude and patronising then so will I!!!
Sidewinder will answer himself when he looks into the purpose of the additional electrode on a PME, why the Ra is important and what current it is that becomes a danger upon a broken PEN, GN5 has a section on it, have a look you may learn something
where is the last point of your PME rodded?
you have no control over this, so you should do it yourself, localise the PME system so you can ensure its integrity.
We are now into multiple quoted posts, this always goes wrong for me.
I should not have posted late last night, I had too much work on and because of this I am a day behind now where I should be, so I don;t have the time tonight to prattle on with this.
My post #41 has a typing error.
It was too late, diverted neutral currents are from outside the installation.
Anything originating in the installation that does not follow the correct design path is NOT diverted it is due to a fault.
Chris, your post #42, a correctly designed and installed PME system will not divert, i.e. export neutral fault currents outside the installation where the fault lies.
Chris, your post #44 picks up on my typo, it was too late & I was stressed out with the work I had here.
Post #45.
This is no concern of ours and does depend upon several things including the number of earthing points, there is no single answer. IIRC it is <20 Ohms, but, if you have enough rods dropped connected to the CNE then they could be 100 Ohms per rod and still achieve 0.35 Ohms.
This is a DNO issue, and will be covered by their engineering manuals.
The 0.35 figure given in BS7671 is not set in stone, it is a suggestion no more.
Post #46.
Yes the current will find an alternative route, but this is NOT diverted it is due to a FAULT.
Post #47 & #48, #49 & #50, are specific to Steps and have no response, as it is up to HIM how he installs his rods, and as I have said, DNO cabling is nothing to do with BS7671, thus the installation electrician. I agree that the current is a fault current if originating within the installation.
Post #51.
It seems you are confusing TN-C-S & PME they are NOT the same.
Your irksome comments are not constructive.
Why can't you get the concept that TN-C-S & PME are different?
You are also suggesting that the star point of the DNO Tx is at the consumers install.
Every one I have queried has not been.
I am guessing that by Dy11 you mean a Delta/Star connection, however how can you be sure it is in 11 configuration?
IMHO you then go on to describe a fault scenario related to a single installation.
This does not allow currents from another installation to be diverted into "our" install.
I will concede that the N current is "diverted" from its design path, but I do not consider this diverted N current as would be experienced in multiple consumer TN-C-S/PME systems.
I don't recall stating that the Ra was of not too much importance, if you READ my post I said that you should ensure it is low enough to ensure that there is no discernible touch voltage, that has to be determined on site & from the relevant guidance.
I don't think that you are totally au fait with the TN-C-S/PME situation, and, no I did not ask the design engineer, as I was the design engineer for the work being done.
After careful study of the cable route & the installation methods, it became apparent what the system was.
The DNO in this situation could NOT have moved the star point to the consumers install, in "my" area I'm told they don't also.
Oh, and no, you have not answered all of my questions yet!
Post #52,
You seem to again be concerned with ESQCR stuff, DNO standards etc.
This is "technically" not "our" concern.
Once again it seems that we disagree over the terminology, I do not consider that neutral currents originating within an installation being re-directed "diverted" if you choose due to a break in the CNE are "diverted", they are due to a fault on the single installation.
I consider "diverted" N currents those being imposed on an installation by a fault on another installation or on a common supply to many installations.
Post #53.
I disagree with your terms.
It seems will will have to agree to disagree.
Post #54 is not really important.
Post #55.
I have read GN5, in fact I have read GN1-8 and hold copies along with many other standards & guidance.
I still hold my point.
Oh & by the way it does not matter, where, I am, I have the same views.
You can be rude or patronising if you like, I'm a Professional Engineer, thus, I am paid for my opinion, hence I am forthright in expressing this, it is how I earn my living as I am freelance.
I follow your reasoning, but I disagree on the terminology.
I do not consider current arising from within an installation due to a fault on the installation and its single supply cable from a dedicated transformer as "diverted", I agree that we can use the term, but IMHO it is not diverted in from another install, or a fault on a common supply to other installs, which is how I use the term.
Post #58.
An opinion by Steps, not a point of debate as yet.
However, I agree that a rod should be dropped of sufficiently low impedance to ensure the required conditions are met.
Posts #56 & #57 are not relevant to the debate.
I should not have posted late last night, I had too much work on and because of this I am a day behind now where I should be, so I don;t have the time tonight to prattle on with this.
My post #41 has a typing error.
It was too late, diverted neutral currents are from outside the installation.
Anything originating in the installation that does not follow the correct design path is NOT diverted it is due to a fault.
Chris, your post #42, a correctly designed and installed PME system will not divert, i.e. export neutral fault currents outside the installation where the fault lies.
Chris, your post #44 picks up on my typo, it was too late & I was stressed out with the work I had here.
Post #45.
This is no concern of ours and does depend upon several things including the number of earthing points, there is no single answer. IIRC it is <20 Ohms, but, if you have enough rods dropped connected to the CNE then they could be 100 Ohms per rod and still achieve 0.35 Ohms.
This is a DNO issue, and will be covered by their engineering manuals.
The 0.35 figure given in BS7671 is not set in stone, it is a suggestion no more.
Post #46.
Yes the current will find an alternative route, but this is NOT diverted it is due to a FAULT.
Post #47 & #48, #49 & #50, are specific to Steps and have no response, as it is up to HIM how he installs his rods, and as I have said, DNO cabling is nothing to do with BS7671, thus the installation electrician. I agree that the current is a fault current if originating within the installation.
Post #51.
It seems you are confusing TN-C-S & PME they are NOT the same.
Your irksome comments are not constructive.
Why can't you get the concept that TN-C-S & PME are different?
You are also suggesting that the star point of the DNO Tx is at the consumers install.
Every one I have queried has not been.
I am guessing that by Dy11 you mean a Delta/Star connection, however how can you be sure it is in 11 configuration?
IMHO you then go on to describe a fault scenario related to a single installation.
This does not allow currents from another installation to be diverted into "our" install.
I will concede that the N current is "diverted" from its design path, but I do not consider this diverted N current as would be experienced in multiple consumer TN-C-S/PME systems.
I don't recall stating that the Ra was of not too much importance, if you READ my post I said that you should ensure it is low enough to ensure that there is no discernible touch voltage, that has to be determined on site & from the relevant guidance.
I don't think that you are totally au fait with the TN-C-S/PME situation, and, no I did not ask the design engineer, as I was the design engineer for the work being done.
After careful study of the cable route & the installation methods, it became apparent what the system was.
The DNO in this situation could NOT have moved the star point to the consumers install, in "my" area I'm told they don't also.
Oh, and no, you have not answered all of my questions yet!
Post #52,
You seem to again be concerned with ESQCR stuff, DNO standards etc.
This is "technically" not "our" concern.
Once again it seems that we disagree over the terminology, I do not consider that neutral currents originating within an installation being re-directed "diverted" if you choose due to a break in the CNE are "diverted", they are due to a fault on the single installation.
I consider "diverted" N currents those being imposed on an installation by a fault on another installation or on a common supply to many installations.
Post #53.
I disagree with your terms.
It seems will will have to agree to disagree.
Post #54 is not really important.
Post #55.
I have read GN5, in fact I have read GN1-8 and hold copies along with many other standards & guidance.
I still hold my point.
Oh & by the way it does not matter, where, I am, I have the same views.
You can be rude or patronising if you like, I'm a Professional Engineer, thus, I am paid for my opinion, hence I am forthright in expressing this, it is how I earn my living as I am freelance.
I follow your reasoning, but I disagree on the terminology.
I do not consider current arising from within an installation due to a fault on the installation and its single supply cable from a dedicated transformer as "diverted", I agree that we can use the term, but IMHO it is not diverted in from another install, or a fault on a common supply to other installs, which is how I use the term.
Post #58.
An opinion by Steps, not a point of debate as yet.
However, I agree that a rod should be dropped of sufficiently low impedance to ensure the required conditions are met.
Posts #56 & #57 are not relevant to the debate.
a3
3 of 9
Do you need some screen shots of how to use the MultiQuote Button for future reference ?
Chris, your post #42, a correctly designed and installed PME system will not divert, i.e. export neutral fault currents outside the installation where the fault lies.
Its simple, With a TNC-S you will get Diverted Neutral Current, now whether that is Diverted Current due ro a fault on the Pen or whether its Divereted Currents between multiple systems in normal operating conditions, any cuurent not contained within the Neutral is Diverted. Its not my termonology, its used by the IEC!
Post #45.
This is no concern of ours and does depend upon several things including the number of earthing points, there is no single answer. IIRC it is <20 Ohms, but, if you have enough rods dropped connected to the CNE then they could be 100 Ohms per rod and still achieve 0.35 Ohms.
This is a DNO issue, and will be covered by their engineering manuals.
The 0.35 figure given in BS7671 is not set in stone, it is a suggestion no more.
We may have no diect influence on the DNO'S paramenters, though understanding them allows us to design our systems, the issue with rods at 100 ohm's is when the PEN breaks, at this Ra the touch voltage will not be sufficiantly reduced, after all that is the purpose of PME!! The Enginering Manulals are born out of the ENA guidance notes, these in turn from the IEC standards.
Post #51.
It seems you are confusing TN-C-S & PME they are NOT the same.
PME is a variant of TNC-S, its how the PEN is Constructed that Makes a TNC-S a TNC-S PME, what is it im confusing,please?
Your irksome comments are not constructive.
Neither are you patronising remarks like this .. "You obviously are out of your depth with no clue so please leave it to those who know." Yet you still have not explained why im out of my depth with this.
Why can't you get the concept that TN-C-S & PME are different?
As i have said PME is just a variant of TNC-S
You are also suggesting that the star point of the DNO Tx is at the consumers install.
Every one I have queried has not been.
Errm NO, that's not what i have suggested, if we look at a PNB with the single source electrode at the consumers intake then arguably Yes hence teh TN-S dabate.
I am guessing that by Dy11 you mean a Delta/Star connection, however how can you be sure it is in 11 configuration?
Well that's pretty much standard in this country for distribution, have you come accross other vectors group's on public distribution?
IMHO you then go on to describe a fault scenario related to a single installation.
This does not allow currents from another installation to be diverted into "our" install.
I will concede that the N current is "diverted" from its design path, but I do not consider this diverted N current as would be experienced in multiple consumer TN-C-S/PME systems.
I beleive i have answered this above.
I don't recall stating that the Ra was of not too much importance, if you READ my post I said that you should ensure it is low enough to ensure that there is no discernible touch voltage, that has to be determined on site & from the relevant guidance.
Okay, so how do we determine the Ra of the electrode to ensure a low touch voltage? GN5 give's reference, Is it not based on the Diverted Neutral Current of the Installation, could you please explain your differing opinion with GN5.
I don't think that you are totally au fait with the TN-C-S/PME situation, and, no I did not ask the design engineer, as I was the design engineer for the work being done.
Why's that,can you explain in more detail as to what it is you imply i dont understand?
When i refer to a design engineer, i refer to the System Engineer responsible for the Transmission and distribution for that section of the Network. No spur will be made without it being passed by He/She.
After careful study of the cable route & the installation methods, it became apparent what the system was.
The DNO in this situation could NOT have moved the star point to the consumers install, in "my" area I'm told they don't also
Tehn i dont see ho it could be TN-S, if the solid earth was at the spill box and the PNB bond at the consumers then in effect you have a Pen, Neutral current and Earth fault current will be present .
Could you please explain the above queries in detail please.
Thankyou
Its simple, With a TNC-S you will get Diverted Neutral Current, now whether that is Diverted Current due ro a fault on the Pen or whether its Divereted Currents between multiple systems in normal operating conditions, any cuurent not contained within the Neutral is Diverted. Its not my termonology, its used by the IEC!
Post #45.
This is no concern of ours and does depend upon several things including the number of earthing points, there is no single answer. IIRC it is <20 Ohms, but, if you have enough rods dropped connected to the CNE then they could be 100 Ohms per rod and still achieve 0.35 Ohms.
This is a DNO issue, and will be covered by their engineering manuals.
The 0.35 figure given in BS7671 is not set in stone, it is a suggestion no more.
We may have no diect influence on the DNO'S paramenters, though understanding them allows us to design our systems, the issue with rods at 100 ohm's is when the PEN breaks, at this Ra the touch voltage will not be sufficiantly reduced, after all that is the purpose of PME!! The Enginering Manulals are born out of the ENA guidance notes, these in turn from the IEC standards.
Post #51.
It seems you are confusing TN-C-S & PME they are NOT the same.
PME is a variant of TNC-S, its how the PEN is Constructed that Makes a TNC-S a TNC-S PME, what is it im confusing,please?
Your irksome comments are not constructive.
Neither are you patronising remarks like this .. "You obviously are out of your depth with no clue so please leave it to those who know." Yet you still have not explained why im out of my depth with this.
Why can't you get the concept that TN-C-S & PME are different?
As i have said PME is just a variant of TNC-S
You are also suggesting that the star point of the DNO Tx is at the consumers install.
Every one I have queried has not been.
Errm NO, that's not what i have suggested, if we look at a PNB with the single source electrode at the consumers intake then arguably Yes hence teh TN-S dabate.
I am guessing that by Dy11 you mean a Delta/Star connection, however how can you be sure it is in 11 configuration?
Well that's pretty much standard in this country for distribution, have you come accross other vectors group's on public distribution?
IMHO you then go on to describe a fault scenario related to a single installation.
This does not allow currents from another installation to be diverted into "our" install.
I will concede that the N current is "diverted" from its design path, but I do not consider this diverted N current as would be experienced in multiple consumer TN-C-S/PME systems.
I beleive i have answered this above.
I don't recall stating that the Ra was of not too much importance, if you READ my post I said that you should ensure it is low enough to ensure that there is no discernible touch voltage, that has to be determined on site & from the relevant guidance.
Okay, so how do we determine the Ra of the electrode to ensure a low touch voltage? GN5 give's reference, Is it not based on the Diverted Neutral Current of the Installation, could you please explain your differing opinion with GN5.
I don't think that you are totally au fait with the TN-C-S/PME situation, and, no I did not ask the design engineer, as I was the design engineer for the work being done.
Why's that,can you explain in more detail as to what it is you imply i dont understand?
When i refer to a design engineer, i refer to the System Engineer responsible for the Transmission and distribution for that section of the Network. No spur will be made without it being passed by He/She.
After careful study of the cable route & the installation methods, it became apparent what the system was.
The DNO in this situation could NOT have moved the star point to the consumers install, in "my" area I'm told they don't also
Tehn i dont see ho it could be TN-S, if the solid earth was at the spill box and the PNB bond at the consumers then in effect you have a Pen, Neutral current and Earth fault current will be present .
Could you please explain the above queries in detail please.
Thankyou
headbang
PME is NOT a variant of TNC-S , it is a type of earthing system,
TNC-S is the supply type.
Similar threads
- Locked
