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Topic Title: Application of the proposed regulation 542.1.201
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Created On: 29 July 2017 12:35 PM
Status: Read Only
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 Application of the proposed regulation 542.1.201   - sparkingchip - 29 July 2017 12:35 PM  
 Application of the proposed regulation 542.1.201   - dustydazzler - 29 July 2017 12:54 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 29 July 2017 01:00 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 29 July 2017 01:42 PM  
 Application of the proposed regulation 542.1.201   - Parsley - 29 July 2017 03:10 PM  
 Application of the proposed regulation 542.1.201   - dustydazzler - 29 July 2017 03:26 PM  
 Application of the proposed regulation 542.1.201   - dustydazzler - 29 July 2017 01:06 PM  
 Application of the proposed regulation 542.1.201   - Parsley - 29 July 2017 03:16 PM  
 Application of the proposed regulation 542.1.201   - psychicwarrior - 29 July 2017 04:44 PM  
 Application of the proposed regulation 542.1.201   - Alcomax - 29 July 2017 06:49 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 29 July 2017 08:07 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 29 July 2017 08:16 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 29 July 2017 08:14 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 29 July 2017 09:22 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 29 July 2017 09:59 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 30 July 2017 10:25 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 30 July 2017 11:08 AM  
 Application of the proposed regulation 542.1.201   - Zoomup - 30 July 2017 11:00 AM  
 Application of the proposed regulation 542.1.201   - Zoomup - 30 July 2017 11:09 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 30 July 2017 11:29 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 30 July 2017 02:00 PM  
 Application of the proposed regulation 542.1.201   - Angram - 30 July 2017 02:55 PM  
 Application of the proposed regulation 542.1.201   - Zoomup - 30 July 2017 11:20 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 19 November 2017 07:08 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 19 November 2017 07:43 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 30 July 2017 12:28 PM  
 Application of the proposed regulation 542.1.201   - Zoomup - 30 July 2017 06:37 PM  
 Application of the proposed regulation 542.1.201   - Legh - 31 July 2017 11:13 AM  
 Application of the proposed regulation 542.1.201   - Zoomup - 04 August 2017 05:53 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 30 July 2017 12:35 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 30 July 2017 04:43 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 30 July 2017 05:21 PM  
 Application of the proposed regulation 542.1.201   - Zoomup - 30 July 2017 06:58 PM  
 Application of the proposed regulation 542.1.201   - Zoomup - 30 July 2017 07:31 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 30 July 2017 08:06 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 30 July 2017 10:06 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 30 July 2017 11:15 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 30 July 2017 11:28 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 31 July 2017 11:40 AM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 31 July 2017 12:36 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 31 July 2017 01:34 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 31 July 2017 01:45 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 31 July 2017 03:01 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 31 July 2017 05:16 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 31 July 2017 07:05 PM  
 Application of the proposed regulation 542.1.201   - Zs - 31 July 2017 09:45 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 31 July 2017 11:17 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 01 August 2017 09:05 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 01 August 2017 01:52 PM  
 Application of the proposed regulation 542.1.201   - OMS - 01 August 2017 07:02 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 01 August 2017 07:05 PM  
 Application of the proposed regulation 542.1.201   - Parsley - 01 August 2017 08:57 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 01 August 2017 09:59 PM  
 Application of the proposed regulation 542.1.201   - MWalker86 - 01 August 2017 06:54 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 01 August 2017 10:34 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 01 August 2017 11:07 PM  
 Application of the proposed regulation 542.1.201   - OMS - 02 August 2017 12:20 PM  
 Application of the proposed regulation 542.1.201   - OMS - 02 August 2017 12:22 PM  
 Application of the proposed regulation 542.1.201   - rocknroll - 02 August 2017 02:45 PM  
 Application of the proposed regulation 542.1.201   - OMS - 02 August 2017 04:56 PM  
 Application of the proposed regulation 542.1.201   - rocknroll - 02 August 2017 05:04 PM  
 Application of the proposed regulation 542.1.201   - OMS - 02 August 2017 05:12 PM  
 Application of the proposed regulation 542.1.201   - rocknroll - 02 August 2017 05:16 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 02 August 2017 06:17 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 03 August 2017 08:34 AM  
 Application of the proposed regulation 542.1.201   - OMS - 02 August 2017 06:47 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 02 August 2017 07:25 PM  
 Application of the proposed regulation 542.1.201   - dustydazzler - 02 August 2017 07:06 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 02 August 2017 09:11 PM  
 Application of the proposed regulation 542.1.201   - Zoomup - 03 August 2017 08:31 AM  
 Application of the proposed regulation 542.1.201   - weirdbeard - 03 August 2017 07:07 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 03 August 2017 10:02 PM  
 Application of the proposed regulation 542.1.201   - AJJewsbury - 03 August 2017 07:37 PM  
 Application of the proposed regulation 542.1.201   - weirdbeard - 03 August 2017 08:18 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 03 August 2017 10:10 PM  
 Application of the proposed regulation 542.1.201   - whjohnson - 04 August 2017 10:53 AM  
 Application of the proposed regulation 542.1.201   - Parsley - 04 August 2017 11:48 AM  
 Application of the proposed regulation 542.1.201   - weirdbeard - 04 August 2017 05:49 PM  
 Application of the proposed regulation 542.1.201   - whjohnson - 03 August 2017 08:06 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 04 August 2017 03:49 PM  
 Application of the proposed regulation 542.1.201   - weirdbeard - 04 August 2017 04:30 PM  
 Application of the proposed regulation 542.1.201   - weirdbeard - 04 August 2017 06:00 PM  
 Application of the proposed regulation 542.1.201   - weirdbeard - 04 August 2017 08:18 PM  
 Application of the proposed regulation 542.1.201   - whjohnson - 05 August 2017 12:05 AM  
 Application of the proposed regulation 542.1.201   - MWalker86 - 05 August 2017 03:04 AM  
 Application of the proposed regulation 542.1.201   - Zoomup - 05 August 2017 09:09 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 05 August 2017 11:49 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 05 August 2017 12:55 PM  
 Application of the proposed regulation 542.1.201   - weirdbeard - 05 August 2017 03:57 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 05 August 2017 06:59 PM  
 Application of the proposed regulation 542.1.201   - Zoomup - 05 August 2017 08:28 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 06 August 2017 12:21 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 06 August 2017 12:27 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 06 August 2017 09:18 PM  
 Application of the proposed regulation 542.1.201   - whjohnson - 06 August 2017 08:10 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 06 August 2017 09:13 PM  
 Application of the proposed regulation 542.1.201   - iie63674 - 07 August 2017 08:45 PM  
 Application of the proposed regulation 542.1.201   - psychicwarrior - 07 August 2017 09:10 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 07 August 2017 10:47 PM  
 Application of the proposed regulation 542.1.201   - MWalker86 - 07 August 2017 10:51 PM  
 Application of the proposed regulation 542.1.201   - whjohnson - 07 August 2017 11:54 PM  
 Application of the proposed regulation 542.1.201   - iie63674 - 10 August 2017 09:13 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 12 August 2017 12:34 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 03 October 2017 11:11 AM  
 Application of the proposed regulation 542.1.201   - weirdbeard - 12 August 2017 01:42 PM  
 Application of the proposed regulation 542.1.201   - whjohnson - 12 August 2017 02:22 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 12 August 2017 04:40 PM  
 Application of the proposed regulation 542.1.201   - dustydazzler - 12 August 2017 02:25 PM  
 Application of the proposed regulation 542.1.201   - weirdbeard - 12 August 2017 04:13 PM  
 Application of the proposed regulation 542.1.201   - geoffsd - 12 August 2017 07:29 PM  
 Application of the proposed regulation 542.1.201   - leckie - 12 August 2017 09:29 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 13 August 2017 12:11 AM  
 Application of the proposed regulation 542.1.201   - geoffsd - 13 August 2017 12:24 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 13 August 2017 12:42 AM  
 Application of the proposed regulation 542.1.201   - MWalker86 - 13 August 2017 12:56 AM  
 Application of the proposed regulation 542.1.201   - iie63674 - 13 August 2017 06:46 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 13 August 2017 01:00 AM  
 Application of the proposed regulation 542.1.201   - whjohnson - 13 August 2017 01:30 PM  
 Application of the proposed regulation 542.1.201   - geoffsd - 13 August 2017 07:06 PM  
 Application of the proposed regulation 542.1.201   - iie63674 - 13 August 2017 07:32 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 02 October 2017 11:25 PM  
 Application of the proposed regulation 542.1.201   - mapj1 - 19 November 2017 09:40 PM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 19 November 2017 10:37 PM  
 Application of the proposed regulation 542.1.201   - mapj1 - 20 November 2017 09:30 AM  
 Application of the proposed regulation 542.1.201   - sparkingchip - 21 November 2017 10:54 PM  
 Application of the proposed regulation 542.1.201   - mapj1 - 22 November 2017 07:50 AM  
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 29 July 2017 12:35 PM
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sparkingchip

Posts: 10196
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Here is the proposed new regulation:

542.1.201 The main earthing terminal shall be connected with Earth by one of the methods described in Regulations 542.1.2.1 to 3 , as appropriate to the type of system of which the installation is to form a part and in compliance with Regulations 542.1.3.1 and 542.1.3.2 . Additionally, there shall be an earth electrode, supplementing any earthing facility provided by the distributor, in accordance with one of the requirements of Regulation 542.2.3, to prevent the appearance of a dangerous touch voltage in the event of the loss of the main connection to Earth.

I would like to see some worked examples of the application of this proposed regulation, let's start with an installation I completed around nine years ago that is currently considered safe being earted to the DNO TNCS-PME earth terminals, but will no longer be considered so if the installation work were to be undertaken after the implementation of the 18th edition of BS7671.

The project was a conversion and extension of a large Victorian house into seven flats with a landlord supply to the common areas.

Central Networks ran in a new supply from the road, they installed a new PME electrode at the joint in the road, then around 60 metres of new cable to a joint with another PME electrode. From this joint there is a 10 metre branch cable to two single phase intakes at the side of the building for single flats and the main cable runs on to a Ryfield three phase head that belongs to the DNO this supplies five flats and the landlords supply, this three phase head has a single shared DNO earth terminal.

Three of the flats have gas supplies maximum demand 40 amps and have a single rate meter as does the landlords supply with a minimal demand, the other four flats are all electric with storage heaters and a maximum of 80 amps on dual rate E7 meters.

To comply with this new regulation does it have to have three installation electrodes or can the installer interlink the three DNO earth terminals to one electrode system? What is the maximum permissible Ra of the electrode system to be installed and what specification would you anticipate for this site with sandy soil?

The three phase Ryfield with the shared DNO earth terminal has a maximum demand of 120 A / 120 A / 85 A across the three phases, the two separate single phase intakes have a maximum demand of 80 A each.

Andy B

Edited: 29 July 2017 at 12:45 PM by sparkingchip
 29 July 2017 12:54 PM
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dustydazzler

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one rod per application one would presume , correctly labelled at the stake and the corresponding terminal
 29 July 2017 01:00 PM
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sparkingchip

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Originally posted by: dustydazzler

one rod per application one would presume , correctly labelled at the stake and the corresponding terminal


Maximum resistance Ra and expected length for a site with sandy soil, also the maximum permissible touch voltage?

Andy B
 29 July 2017 01:42 PM
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sparkingchip

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Originally posted by: dustydazzler

one rod per application one would presume , correctly labelled at the stake and the corresponding terminal


If it were a new building then they could share the foundation earthing system, couldn't they?

Andy B
 29 July 2017 03:10 PM
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Parsley

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My guess is one supplementary electrode is required per DNO cut-out or DNO owned Ryefield DB if that's where the PME N-E link is.
If this was a new install and building was steel framed the DNO would only supply one cut-out that was PME all the other services would be SNE supplied ideally from one intake position, to prevent diverted neutral currents joining all PME supplies to one common additional electrode might not be the best idea in your example.

The reg doesn't seem to have been probably thought out, it refers to the 542.2.3 which only mentions foundation electrodes.
I added my comments to BSI site yesterday, there were only 20 other comments on this reg proposal.

I personally think it can only benefit new installs and the reg needs to reflect that. I don't believe a resistance value will be given.

Regards
 29 July 2017 03:26 PM
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dustydazzler

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Originally posted by: Parsley

My guess is one supplementary electrode is required per DNO cut-out or DNO owned Ryefield DB if that's where the PME N-E link is.

If this was a new install and building was steel framed the DNO would only supply one cut-out that was PME all the other services would be SNE supplied ideally from one intake position, to prevent diverted neutral currents joining all PME supplies to one common additional electrode might not be the best idea in your example.



The reg doesn't seem to have been probably thought out, it refers to the 542.2.3 which only mentions foundation electrodes.

I added my comments to BSI site yesterday, there were only 20 other comments on this reg proposal.



I personally think it can only benefit new installs and the reg needs to reflect that. I don't believe a resistance value will be given.



Regards


THIS ^^^
Reserve this new fandango earth spike stipulation for brand new installs
Leave us poor saps to continue merrily using the suppliers provided earth provision
 29 July 2017 01:06 PM
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dustydazzler

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I'm going to have to tag in one of the masterminds on this one
Too many variables and not enough experience installing earth electrodes in sandy conditions
 29 July 2017 03:16 PM
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Parsley

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The IET are advertising for a senior engineer at the moment, the role involves supporting JPEL 64.

Regards
 29 July 2017 04:44 PM
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psychicwarrior

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..and I thought there was only a very rare chance that the supplier N would be lost (thinking about all the discussion relating to TN-C-S (im leaving out the is it PME but :-) ). Is it now the case that this (loss of connection to earth) is not as rare as it first came across to me !
 29 July 2017 06:49 PM
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Alcomax

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The recent and proposed amendments appear to contain a subtle shift of risk from DNO to electrician. First the model forms were adapted to include a pass/ fail on suppliers equipment and , indeed, "distributors earthing arrangement". Now the existing risk latent defects of the network and the efficacy of "supplier earth facility " are potentially being further shifted.

Someone asked a question in the last few weeks regarding metal service heads, not sure if it was answered. Anyhow, these were routinely changed and pretty damn quick when highlighted by an electrician and/or inspector. The last couple of years this has changed and appear not bothered anymore. On PILC service cables below the head, in the past would sometimes observe significant bulges in the cabling. These were actioned PDQ, not anymore...will send a jointer who will say "that's okay" , but will not put anything in writing. For clients it is a problem, particularly commercial. As there is this element of doubt. There is "no sign off" of risk.
 29 July 2017 08:07 PM
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sparkingchip

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The reference documents I am using for this design exercise are:

IET Guidance Note 5. Protection against electric shock. IET 17th edition wiring regulations BS7671:2008 incorporating amendment number 1:2008. 14.5 Additional earth electrode for PME supplies. Page 100.

IET Code of practice for electric vehicle charging equipment installation 2nd edition fully updated to BS 7671:2008+A3:2015. Section 6.8.3 Installing an earth electrode system. Page 40.

Both have the identical figure illustrating the open PEN situation, however GN5 considers the Ra of casual earth connections and includes water and gas pipes with touch voltages of 50 V and 100 V. The EV code of practice considers the Ra of an additional electrode connected to the main earth terminal with a touch voltage of 70 V.

In the project I have detailed all the gas and water supply pipes are plastic, so do not help to lower Ra.

Before the design can really get underway we have to agree what constitutes a dangerous voltage, despite years of considering that maximum touch voltage should be 50 volts I think we are going to have to agree that we are going to consider a maximum safe touch voltage can be 70 volts inline with the guidance within the EV code of practice.

So to get the ball rolling can we agree that a dangerous touch voltage is a voltage in excess of 70 volts?

Andy B.

Edited: 29 July 2017 at 08:20 PM by sparkingchip
 29 July 2017 08:16 PM
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sparkingchip

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Originally posted by: Alcomax

The recent and proposed amendments appear to contain a subtle shift of risk from DNO to electrician. First the model forms were adapted to include a pass/ fail on suppliers equipment and , indeed, "distributors earthing arrangement". Now the existing risk latent defects of the network and the efficacy of "supplier earth facility " are potentially being further shifted.



Someone asked a question in the last few weeks regarding metal service heads, not sure if it was answered. Anyhow, these were routinely changed and pretty damn quick when highlighted by an electrician and/or inspector. The last couple of years this has changed and appear not bothered anymore. On PILC service cables below the head, in the past would sometimes observe significant bulges in the cabling. These were actioned PDQ, not anymore...will send a jointer who will say "that's okay" , but will not put anything in writing. For clients it is a problem, particularly commercial. As there is this element of doubt. There is "no sign off" of risk.


I agree completely, for some years now in the Central Networks, now Western Power area where I am, new DNO TNCS customer earth terminals have come with a disclaimer saying they have not been tested by the DNO and it is the customers responsibility to engage a qualified electrician to check that the earth terminal is suitable for use by testing it; and the electrician should make the final connection of the installation main earth conductor to the DNO earth terminal with metering services only connecting the live and neutral tails into a isolation switch, leaving the electrician to make the final connections of the live and neutral tails along with the main earth conductor, with the electrician absolving both the DNO and metering services of responsibility for ensuring there is correct polarity and a sound earth connection.

Andy B.
 29 July 2017 08:14 PM
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AJJewsbury

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So to get the ball rolling can we agree that a dangerous touch voltage is a voltage in excess of 70 volts?

For the sake of debate, I'd say yes. (I'd prefer 50V, but the result will be almost as ridiculous anyway it makes no difference).

I'd suggest the next step is to establish what sort of current the electrode will be required to sink - which depends on where the break in the CNE is assumed to be and the connected loads downstream of the break. For the sake of an initial debate, I'd suggest assuming that the break will affect only your individual installation (or equivalently that all other installations have equally effective electrodes).

- Andy.

Edited: 29 July 2017 at 08:22 PM by AJJewsbury
 29 July 2017 09:22 PM
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AJJewsbury

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Some interesting notes from a DNO about earthing here - http://library.ukpowernetworks...on+Earthing+Design.pdf especially tables B-2 and B-3 on page 50 which give likely resistances for differing number of driven electrodes and lengths of buried conductor/mats in various soil resistances.
- Andy.
 29 July 2017 09:59 PM
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sparkingchip

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Originally posted by: AJJewsbury

Some interesting notes from a DNO about earthing here - http://library.ukpowernetworks...on+Earthing+Design.pdf especially tables B-2 and B-3 on page 50 which give likely resistances for differing number of driven electrodes and lengths of buried conductor/mats in various soil resistances.

- Andy.


The IET GN5 gives that substation earth as RB the resistance to earth of the neutral point of the power supply, it advises we can neglect it in our calculation as this errs on the safe side, we can also neglect Re, the external line supply resistance as it is small compared with RL and RA.

I will have a go at typing the formula tomorrow, trying to type them out on this forum is too much of a challenge for this time of night.

Andy B.
 30 July 2017 10:25 AM
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AJJewsbury

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That's a point. The supplier's substation electrode will also have some resistance - typically next to nothing for a substantial urban distribution system perhaps, but for two or three rural customers fed from a pole pig transformer fed from overhead HV lines, it could well be in the region of 20 Ohms. So even if we somehow got the customer's electrode down to some sub-Ohm values to keep touch/step voltages around the home within safe values, we'd be creating a potentially dangerous situation around the transformer's electrode - and not for the few seconds that rise of earth potential calculations are normally based on, but for many hours perhaps even days; and that potential would be transferred to exposed-conductive-parts upstream of the break too.
- Andy.
 30 July 2017 11:08 AM
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sparkingchip

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Originally posted by: AJJewsbury

That's a point. The supplier's substation electrode will also have some resistance - typically next to nothing for a substantial urban distribution system perhaps, but for two or three rural customers fed from a pole pig transformer fed from overhead HV lines, it could well be in the region of 20 Ohms. So even if we somehow got the customer's electrode down to some sub-Ohm values to keep touch/step voltages around the home within safe values, we'd be creating a potentially dangerous situation around the transformer's electrode - and not for the few seconds that rise of earth potential calculations are normally based on, but for many hours perhaps even days; and that potential would be transferred to exposed-conductive-parts upstream of the break too.

- Andy.


If we refer to the Introduction of the IET On-Site Guide BS 7671:2008+A3:2015. 1.1(d) page 11 it says:

"For a TT arrangement, 21 ohms is the usual stated maximum resistance of the distributor's earth electrode at the supply transformer."

So that pole transformer supply installed as TNCS-PNB with a single DNO electrode or indeed TNCS-PME with only one DNO electrode left connected to the Tx may presumably have relatively high earth resistance that may cause issues when trying to comply with 542.1.201.

However for the purposes of this calculation and design we can ignore the resistance of the DNO electrode.

Andy B.
 30 July 2017 11:00 AM
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Zoomup

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The idea of a reliably large earth fault current being carried through the ground at low Voltage is bonkers. It can never be assured to be reliable with large loads. It can never be assured to be large enough to operate a fuse or circuit breaker. The whole idea is flawed. Bring back some common sense. Ground soil is varying in its conductivity and is unreliable as a conductor at low Voltage. This whole idea of additional earth electrodes replacing the safety of a P.E.N. conductor if it fails is completely nuts. It can never work in most cases.

GGGGRRRRRrrrrrrr. Mumble ,mumble

Z.
 30 July 2017 11:09 AM
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Zoomup

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If the soil was such a good electrical conductor we would not need metal cables to distribute electricity at low Voltage. The ground is unreliable as a conductor at low Voltage. Why can't the electrical engineers understand that simple premise? Metal reliably conducts. Soil does not reliably consistently conduct. A primary school child could tell us that. Blinkin Ek!

Z.
 30 July 2017 11:29 AM
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sparkingchip

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We need to determine RL the load resistance, so we need to know the loading in watts.

Let's keep this simple and consider one of the flats connected to a single phase incomer that has a E7 supply.

There is a number of loads and varied usage, so let's take one specific daily event that occurs every winter night, that is the radio teleswitch turning on the off peak supply. These are two bedroom flats and have three 3.4 Kw and one 2.5 Kw storage heaters totalling 12.7 Kw. These come on at night so other loads are minimal.

Therefore for the purpose of this project I suggest a total of 13 kilowatts as the load for one flat with a E7 supply.

The load resistance RL is Vs2/ wattage

Therefore:

RL = (230x230) / 13000 = 4.07 ohms

Does that sound sensible?

Andy B.
 30 July 2017 02:00 PM
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sparkingchip

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Here is the diagram from GN5 from the Voltimum website featuring an article on swimming pools originally published in the IET Wiring Matters magazine.

The casual earth connection has to become a correctly installed earth electrode with the introduction of 542.1.201 that will prevent a dangerous touch voltage.

Andy B.

Edited: 30 July 2017 at 02:11 PM by sparkingchip
 30 July 2017 02:55 PM
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Angram

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Is there any guidance on how to achieve 1.78 ohms Ra in Camberley, Surrey where there is only sand, not soil, in which to plant an earth electrode of any kind?

If by some measure, not yet known to science, it becomes possible to achieve 1.78 ohms Ra with a rod, how do we protect the earth conductor from causing a fire when the local distributed load finds this new route back to the 21 ohm TX under a broken neutral ?

One thing the proposed regulation will achieve is harmonisation with Europe just prior to Brexit. Earth rods are the norm there I think. No PME.

Fast disconnection with a rod and RCD yes, but voltage rise prevention appears to be a fantasy as the Guidance Note calculations have demonstrated for some years now.

It is a digression to mention here that the cancellation of railway electrification projects, due to escalating costs, was caused by new harmonised european standards being applied to overhead line clearances after costing the projects. BS7671 rules on projects in hand not being allowed even where bridges and tunnels had been built one hundred or so years ago.

We live in interesting times.

Angram.
 30 July 2017 11:20 AM
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Zoomup

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The old system of "earthing" in towns and cities years ago when we used underground water pipes as an earth return was not "earthing", it was "water piping". That allowed us a solid metal "earth" return to the supply transformers. The only part of the term "earthing" that was true was that the metal water pipes were buried in the ground, or earth.

Most people do not understand just what "earthing" means. It is very much misunderstood.

"In contact with the general mass of earth" should read "in contact with an unreliable inconsistent generally electrically insulating dry or wet soil-like substance of unknown or unreliable electrical conductivity".

Z.
 19 November 2017 07:08 PM
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sparkingchip

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Mike Holt YouTube video

It's nearly half an hour long, but stick with it, there is a touch voltage test with the neutral disconnected at the intake and a hair dryer connected as the installation load using the earth rods as a neutral return path.

Andy B.
 19 November 2017 07:43 PM
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sparkingchip

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Here's another one, just to make you think.

Remember currently we install earth electrodes such as rods for use together with RCD devices to limit the risk of electric shock, not as a standalone method.

Mike Holt video on YouTube

Andy B
 30 July 2017 12:28 PM
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AJJewsbury

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However for the purposes of this calculation and design we can ignore the resistance of the DNO electrode.

Agreed - I was just looking at the wider implications of the general approach. (I'm still favouring a different strategy - i.e. detect the problem and disconnect the installation.)

The idea of a reliably large earth fault current being carried through the ground at low Voltage is bonkers. It can never be assured to be reliable with large loads. It can never be assured to be large enough to operate a fuse or circuit breaker.

Just to be clear, it's the normal load currents we're worrying about at the moment, rather than fault currents. (With the CNE open circuit the MET can go up to something towards line voltage, even with no faults present). I think they're ignoring earth faults during a broken CNE condition (as it would still require two faults to danger - the broken CNE being the 1st fault and the internal L-PE fault the second).

- Andy.
 30 July 2017 06:37 PM
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Zoomup

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Originally posted by: AJJewsbury

However for the purposes of this calculation and design we can ignore the resistance of the DNO electrode.


Agreed - I was just looking at the wider implications of the general approach. (I'm still favouring a different strategy - i.e. detect the problem and disconnect the installation.)



The idea of a reliably large earth fault current being carried through the ground at low Voltage is bonkers. It can never be assured to be reliable with large loads. It can never be assured to be large enough to operate a fuse or circuit breaker.


Just to be clear, it's the normal load currents we're worrying about at the moment, rather than fault currents. (With the CNE open circuit the MET can go up to something towards line voltage, even with no faults present). I think they're ignoring earth faults during a broken CNE condition (as it would still require two faults to danger - the broken CNE being the 1st fault and the internal L-PE fault the second).



- Andy.


Yes indeed Andy I agree with you. I was illustrating the unreliability of the use of earth electrodes in varying soil conditions as a method of preventing dangerous Voltages on earthed metalwork. This preventative method will include the event of a broken P.M.E. C.E.N. conductor carrying a healthy normal load current as you correctly point out, where that normal current tries to route via the earthing electrode and/or bonded underground metalwork. If a sustained current flows for some time the earth electrodes may dry out surrounding soil and increase their resistance to "true" earth.

Some sort of detecting device may need to be installed that cuts off the supply if dangerous Voltages appear on exposed conductive parts.

Just what might that device be?

Bye,

Z.
 31 July 2017 11:13 AM
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Legh

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some sort of detecting device may need to be installed that cuts off the supply if dangerous Voltages appear on exposed conductive parts. Just what might that device be?


You could try This method. However, some other regulations would have to also change to accommodate switching an earthing conductor.....

Legh

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http://www.leghrichardson.co.uk

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 04 August 2017 05:53 PM
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Zoomup

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Originally posted by: Legh

some sort of detecting device may need to be installed that cuts off the supply if dangerous Voltages appear on exposed conductive parts. Just what might that device be?




You could try This method. However, some other regulations would have to also change to accommodate switching an earthing conductor.....



Legh


Hello Legh,
could you run me through the theory behind your 300mA three pole R.C.D. system design please?

Thanks,

Z.
 30 July 2017 12:35 PM
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AJJewsbury

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Therefore:

RL = (230x230) / 13000 = 4.07 ohms

Does that sound sensible?

Adds up for me!

So the next stage, what resistance in series with that would have 70V across it when the whole lot is fed by 230V.

If we're to have 70V across the electrode then there should be 230-70=160V across the installation - so current through the 4.07 Ohms would be about 39.3A. Our electrode would therefore have to have a resistance to the general mass of the earth of 70V/39.3A = 1.78 Ohms.

- Andy.
 30 July 2017 04:43 PM
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sparkingchip

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Originally posted by: AJJewsbury

Therefore:



RL = (230x230) / 13000 = 4.07 ohms



Does that sound sensible?


Adds up for me!



So the next stage, what resistance in series with that would have 70V across it when the whole lot is fed by 230V.



If we're to have 70V across the electrode then there should be 230-70=160V across the installation - so current through the 4.07 Ohms would be about 39.3A. Our electrode would therefore have to have a resistance to the general mass of the earth of 70V/39.3A = 1.78 Ohms.



- Andy.


Very succinct.

I was going run through the GN5 equation referring to the figure above from GN5 and the IET Wiring Matters article.



Us is the nominal supply (source) voltage, which for this single phase supply is 230 V.

Up is the touch voltage, Andy J and myself agreed on 70 V for this flat in the project, you may disagree.

Re is the external line supply resistance and GN5 says we can ignore it.

RL is the load resistance (Vs2 / wattage), Andy J and myself agreed on 13 Kw for this flat in the project, giving 4.07 ohms at 230 V.

RA is the resistance of the additional earth electrode and the answer we are looking for.

RB is the resistance to earth of the neutral point of the power supply, which GN5 says we can ignore.

Which gives the answer that the RA of the additional earth electrode needs to be 1.78 ohms or less, as Andy J said above.

So now we need to design an electrode system that is likely to have a RA of 1.78 ohms or less.

Remember this is just for one of the seven flats and the landlords supply, so will still have to deal with the other parts of the project.

Andy
 30 July 2017 05:21 PM
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sparkingchip

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Keison.co.uk

So based on table 6.1 and 6.2 in the EV COP we may, if the soil resistivity is exceptionally low, get away with installing three 2.4 metre rods spaced at 3 metres or five 1.2 metre rods spaced at 3 metres, but that is optimistic.

To quote the EV COP:

"Tables 6.1 and 6.2 demonstrate that, in many installations, it will not be reasonably practicable to achieve the required the required electrode system resistances to earth.

However it is recommended that a minimum of two 2.4 m or three 1.2 m electrodes separated by 3 m are installed. If this practice is followed, whilst many installations will not have touch voltages below 70 V, the risk of injury will be reduced."

Given the precise wording of the proposed regulation 542.1.201 is banging in a few rods knowing they may not really to the job acceptable or do we need to go for the full gold plated job?

Andy B

Edited: 30 July 2017 at 05:42 PM by sparkingchip
 30 July 2017 06:58 PM
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Zoomup

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Then we have to add a "corrosion factor" that allows for loss of efficiency of the earth electrodes due to deterioration and decay, or soil drying. Most domestic earth electrodes are never inspected or tested for efficiency or condition. I recently saw one on the coast that was originally galvanized but now was nicely rusting away with no zinc coat at all above the soil. The copper earth conductor was clamped between two rusty washers. Sub two Ohms? Never. Not originally and certainly not now. More like 50 Ohms or above.

A U.S. earth rod corrosion technical report http://www.erico.com/catalog/literature/LT0540.pdf

Z.

Edited: 30 July 2017 at 07:13 PM by Zoomup
 30 July 2017 07:31 PM
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Zoomup

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A technical report referring to copper, earthing, bonding, electrodes etc. Very informative. http://copperalliance.org.uk/d...hing-practice-pdf.pdf

Z.
 30 July 2017 08:06 PM
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sparkingchip

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So, sizing the earth conductor to the rods, I am guessing if there are 25 mm tails it should be a 25 mm earth conductor, but I think most DNO earth terminals in domestic properties are designed for 16 mm. If it goes in as a bare buried conductor it will have to be 25 mm and that will improve the Ra of the earth electrode system.

So where do we locate the electrode earth terminal, can it go in an external meter box?

Will it be linked to the DNO terminal with 16 mm even if the earth conductor is 25 m?

Do we have to use the Adiabatic equation to size the earth electrode conductor rather than the tables?

Andy B.
 30 July 2017 10:06 PM
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AJJewsbury

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Some sort of detecting device may need to be installed that cuts off the supply if dangerous Voltages appear on exposed conductive parts.

Just what might that device be?

I think I mentioned a possibility in another thread - voltage monitoring relays (starting at about £30 for a single phase one) - either monitor the N-true earth voltage (via a rod with an arbitrary resistance to earth) or just monitor L-N voltage (since if the installation's load is increasing the voltage on the broken CNE, the installation will see a corresponding drop in L-N voltage) so no extra electrode needed at all - the statutory supply limits (216.2 to 253V) would be a good starting point - anything outside that disconnects the installation. A suitable delay (say just over 5s on undervoltage) would ensure that normal earth fault clearance times aren't compromised. As a side effect such an arrangement would also provide some protection from equipment damage and fire risks due to overvoltages in all installations (not just PME) from general broken N (not just CNE) problems. Better still, build the functionality into the new smart meters - as we're about to roll out millions of them - you'd get many more installations protected far more quickly than if you wait for existing installations to get an overhaul - plus the responsibility for providing a supply within spec. then remains with the supply industry, which sort of feels appropriate somehow.

Do we have to use the Adiabatic equation to size the earth electrode conductor rather than the tables?

No chance, as the disconnection time will be well over 5s (maybe several days over...). You could use the minimum electrode resistance to deduce the maximum possible current that could flow and look that up in the normal tables (although that might not help a lot). Applying the same logic to main bonding (if you still have metallic services, also bonded in other installations, the resistance could well be a fraction of an Ohm) you could well find that the normal table 54.8 looks significantly undersized too - as that never considered a broken CNE - just diverted N currents in normal service.

What's that Latin phrase about reducing to absurdity?

- Andy.
 30 July 2017 11:15 PM
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sparkingchip

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In a single phase TNCS installation if the PEN fails and the neutral voltage is raised along with that of the earth terminal along with conductive parts etc. the lights will dim and if the voltage rises enough they will go out.

So, if we permanently connect a green lamp between live and neutral if the neutral voltage rises along with that of the earth it will go out indicating there is a problem, just like some of the cheap extension leads on the market.

B&Q extension lead with power and earth indicators

Job done!

Andy B
 30 July 2017 11:28 PM
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sparkingchip

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It looks like the the earth electrode system conductor needs to be the same size as the tails, but 25 mm conductors may not fit into the DNO earth terminal. Though as a bonus, 25 mm bare buried conductors will improve the Ra.

Andy B.
 31 July 2017 11:40 AM
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sparkingchip

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Let's not get bogged down with the groundwork at the moment. There are two single phase intakes at the side of the building, each needs electrodes, so let's assume that up the alleyway at the side of the flats we will install a total of six 2.4 metre rods spaced at 3.0 metres in two systems separated by 3.0 metres, so a total system length of 15.0 metres connected with 25 mm buried bare copper cable.

We can detail those installations further when we know what we are doing around the front of the building where the shared Ryfield is.

So, in the main entrance hall cupboard there is the three phase Ryfield with the shared DNO earth terminal that have a maximum demand of 120 A / 120 A / 85 A across the three phases.

Let's take that as 20 Kw / 20 Kw / 14 Kw as those figures seem reasonable for he design purposes.

What earth electrode system Ra do we need to keep the Shared Ryfield DNO earth terminal down to a 70 V touch voltage if there is a failed PEN conductor?

Andy B
 31 July 2017 12:36 PM
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AJJewsbury

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Let's take that as 20 Kw / 20 Kw / 14 Kw as those figures seem reasonable for he design purposes.

What earth electrode system Ra do we need to keep the Shared Ryfield DNO earth terminal down to a 70 V touch voltage if there is a failed PEN conductor?

For 3-phase systems I think you need only worry about the neutral current - i.e. the worst case unbalanced situation - which is presumably 20kW - so treat the same as one 20kW single phase installation (I think that comes out at about 1.16 Ohms).

- Andy.
 31 July 2017 01:34 PM
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sparkingchip

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If the neutral and earth is at 70 volts, what happens to the voltage across connected single phase equipment, is it 160 volts?

I remember sitting in evening classes at the old Kidderminster College that has now been demolished with a geometry set drawing three phase vector diagrams, out of the window we could see quite some way away in the darkness a huge pyre withhe rbodies of cattle shot to prevent the spread of foot and mouth disease being burnt. Needless to say I remember the cattle being burnt better than how to do three phase vector diagrams and calculations.

Andy B.
 31 July 2017 01:45 PM
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sparkingchip

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 31 July 2017 03:01 PM
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sparkingchip

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If one winter night I got a phone call to say someone had a electric shock of one of the storage heater cases and due to a lost PEN, if I started turning the main switches off in the hallway to the flats and got to the point where the landlords supply to the lights in the communal area were connected on one phase (0.180 kw) and one of the other phases still had both flats it supplies connected (20 kw), what would the voltage be at the DNO earth terminal that we need to bring down to 70 volts?

Andy B.
 31 July 2017 05:16 PM
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sparkingchip

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Originally posted by: sparkingchip

If one winter night I got a phone call to say someone had a electric shock of one of the storage heater cases and due to a lost PEN, if I started turning the main switches off in the hallway to the flats and got to the point where the landlords supply to the lights in the communal area were connected on one phase (0.180 kw) and one of the other phases still had both flats it supplies connected (20 kw), what would the voltage be at the DNO earth terminal that we need to bring down to 70 volts?



Andy B.


Would there be in the region of 411 volts on the DNO earth terminal?

That's assuming all the LED lamps on the landlords supply have not burnt out.
 31 July 2017 07:05 PM
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sparkingchip

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Originally posted by: sparkingchip

If one winter night I got a phone call to say someone had a electric shock of one of the storage heater cases and due to a lost PEN, if I started turning the main switches off in the hallway to the flats and got to the point where the landlords supply to the lights in the communal area were connected on one phase (0.180 kw) and one of the other phases still had both flats it supplies connected (20 kw), what would the voltage be at the DNO earth terminal that we need to bring down to 70 volts?



Andy B.



If the loads are balanced and the isn't any casual earth connections, then the DNO earth terminal would be around 208 volts, if the loads aren't balanced then it could go up to over 400 volts if I am figuring this out correctly.

However presumably as Andy J said above, so long as an additional earth electrode will clear sufficient current from the heaviest loaded phase it will tie the touch voltage down.

So the maximum Ra of the Ryfield additional earth electrode is 1.16 ohms. We might just do that with five 2.4 metre long earth electrodes spaced at 3 metre intervals, if the soil resistance is particularly low.

Time to put to all together all write a specification.

On this job there are some particularly long trenches to be excavated to put the new DNO supply cables in within the property boundaries, can we use these trenches for he DNO cables to bury some of he new earthing systems in?

Andy B.
 31 July 2017 09:45 PM
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Zs

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I am watching you both with the utmost admiration.

So, not bringing this down to earth but instead taking it above ground..

I take you to a block of flats, some 17 stories high, situated in the east end of London and of which I have intimate knowledge of the riser cupboards.

One of the supplies comes in at ground level. One comes in on the 5th floor and another even higher up. Yes, this can be seen in the variation in the voltages by the way.

How is this new demand going to be achieved when rewiring a flat on the 11th floor?

As Alcomax so eloquently put it on 29th July;
'The recent and proposed amendments appear to contain a subtle shift of risk from DNO to electrician. First the model forms were adapted to include a pass/ fail on suppliers equipment and , indeed, "distributors earthing arrangement". Now the existing risk latent defects of the network and the efficacy of "supplier earth facility " are potentially being further shifted.'

We have had several discussions on here in that past on the subject of farms and stables connected with a TNCS/PME arrangement which is probably inappropriate. We have discussed how best to protect the livestock from possible failure of the supply neutral and thus the path to earth. Whilst this proposed method of a combination of the supply earthing and a belt and braces provided by us, the installers, may have been a useful solution if available, it now seems to be a viable solution. Anyone want to go and tell my local farmer who had half of his neighbourhood dug up for the daisy chain of rods? and so on.

As I have said on here before; every time the regs change the earthing regulations change. That tells me that even the great and the good still haven't got to grips with it.

Are Furse seated on JPEL64 by any chance? I bet you 50p they are.

I have comments on the RCDs and on section 8 (shocking) as well but I will be saving those for a day or so and will start another thread for those.

Zs
 31 July 2017 11:17 PM
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sparkingchip

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We might as well see this discussion through with a specification, materials list and job costing.

Then we need to consider what the risks of using the DNO earth terminal is and also of not using it, for example by trying to make one flat in a building TT direct earthed, when the rest of the flats and communal areas in the block are earthed to the DNO TNCS earth terminal. I suspect by the first amendment of the 18th edition of BS7671 we will be told to do a risk assessment for the choice of earthing system!

Finally when we have a understanding of the requirements and castings we can discuss how we are going to persuade clients that this work is vital and has to be done if the DNO earth terminal is to be used or else we will have to TT everything, which means we will still have to install a earth electrode, but to a much less demanding standard.

The project I have described is a real building, it is owned by a guy who worked in nuclear power station design teams around the world, he isn't someone suffer fools gladly, I will email him the spec and costing with an explanation of what is required and why. I'll pass on his response, edited as required!

Back when the 16th edition was introduced I was working on a new housing site in Gloucestershire and the electrician came in fuming, metering services had refused to install the meter and connect the supply because of the lack of equipotential bonding to the aluminium patio door, the lead flashing on the roof and shower tray, apparently the plastic shower tray was supposed to have the metal waste fitting bonded despite being connected to a plastic waste pipe.

All of those "requirements" turned out to be a lack of understanding, this time however this time around we will be trying to explain the requirements to clients and they won't believe the truth.

That is of course assuming I haven't got it all completely wrong and a installation that is already completed and considered to have perfectly safe earthing, it was the project inspected for my Competent Person Registration the year it was completed, won't need at least eleven 2.4 metre long earth electrodes after next year to be considered safe.

Andy B.
 01 August 2017 09:05 AM
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AJJewsbury

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If the neutral and earth is at 70 volts, what happens to the voltage across connected single phase equipment, is it 160 volts?

For the loaded phase, yes, 160V.

For any equipment on the other two phases the (if my back of an envelope calculation is correct) it would be closer to 271V.

- Andy.
 01 August 2017 01:52 PM
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sparkingchip

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Please, please, PLEASE,

Can someone post as to why they think this proposed regulation is a sensible and viable option to improve electrical safety in the UK.

Someone, somewhere must support this idea or else it would not have made it into the draft.

Andrew Betteridge

betteridgeandrew@hotmail.com
 01 August 2017 07:02 PM
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OMS

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Originally posted by: sparkingchip

Please, please, PLEASE,

Can someone post as to why they think this proposed regulation is a sensible and viable option to improve electrical safety in the UK.

Someone, somewhere must support this idea or else it would not have made it into the draft.

Andrew Betteridge

betteridgeandrew@hotmail.com


Basically, Andy - we are just following what our continental chums do as a matter of course - the idea of a foundation electrode and supplemented by a perimeter electrode is pretty common practice

In many buildings there will be a LPS system so this "electrode" we are all worrying about already exists

What doesn't translate well is how we apply it to:

1 - New dwellings (not usually provided with LPS

2 - Existing Buildings generally

I do sympathise with JPEL64 on this particular issue - harmonization with CENELEC is going to be a nightmare to implement - but they have to start somewhere

I thinks that's basically why they haven't stated a limiting touch voltage - absolutely dare not - and hence we have total confusion in the drafting of the regulation.

Regards

OMS

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 01 August 2017 07:05 PM
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sparkingchip

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Originally posted by: OMS

Originally posted by: sparkingchip



Please, please, PLEASE,



Can someone post as to why they think this proposed regulation is a sensible and viable option to improve electrical safety in the UK.



Someone, somewhere must support this idea or else it would not have made it into the draft.



Andrew Betteridge



betteridgeandrew@hotmail.com




Basically, Andy - we are just following what our continental chums do as a matter of course - the idea of a foundation electrode and supplemented by a perimeter electrode is pretty common practice



In many buildings there will be a LPS system so this "electrode" we are all worrying about already exists



What doesn't translate well is how we apply it to:



1 - New dwellings (not usually provided with LPS



2 - Existing Buildings generally



I do sympathise with JPEL64 on this particular issue - harmonization with CENELEC is going to be a nightmare to implement - but they have to start somewhere



I thinks that's basically why they haven't stated a limiting touch voltage - absolutely dare not - and hence we have total confusion in the drafting of the regulation.



Regards



OMS


But how common is TNCS-PME earthing in the rest of Europe, TT electrodes are a different all game.

Andy Betteridge
 01 August 2017 08:57 PM
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Parsley

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The text below is the conclusion of the Cahier Technique Merlin Gerin n° 173 1995. I have previously stated that its well worth a read.


The three earthing systems (TN - IT - TT) and their implementation are clearly defined in installation standards (IEC 364). Their respective use varies from country to country: c mainly TN in Anglo-Saxon countries; c TT often used in the other countries; c IT used when safety of persons and property, and continuity of service are essential. All three systems are considered to guarantee personnel protection. Two major changes have had a considerable effect on choice of earthing systems: c search for optimum continuity of service;
c proliferation of high current (disturbers) and low current (disturbed) electronic devices, which are increasingly set up in communicating systems. Thus the general tendency for earthing systems, in both MV and LV, is to limit insulation fault currents. At present, the fault currents of traditional LV earthing systems have the following standard values: c IT (1st fault): Id < 1 A; c TT: Id ? 20 A; c TN: Id ? 20 kA; c IT (2nd fault): Id ? 20 kA. Limiting fault currents: c simplifies maintenability of the electrical installation, thus increasing availability;
c minimises the fire hazard; c can reduce contact voltage; c and, for sensitive systems, minimises disturbance due to electromagnetic radiation and common impedance. Moreover, in view of the proliferation of communicating digital systems (computers, video, automation, TBM etc., it is vital that earthing systems provide a potential reference which is not disturbed by high fault currents and harmonics. Consequently, future evolution should favour earthing systems generating fault currents which do not exceed a few dozen amps. TT earthing systems should therefore be increasingly
used.

Regards
 01 August 2017 09:59 PM
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sparkingchip

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We had a discussion about the risk of a PEN conductor failing at the start of last year.

Lost neutral.

Regards the sheep comments, I was in Italy last week and one of the shops had a apron with a ewe on it that I suggested I could buy for one of my farmer customers, however I was told it was inappropriate!
 01 August 2017 06:54 PM
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MWalker86

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So can I just sum up the gist of this regulation in simpler terms;

Basically wherever we have a main earthing terminal, so basically any distribution board/consumer unit, we are supposed to have an earth electrode pretty much right next to it.

Have I got that right?
 01 August 2017 10:34 PM
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AJJewsbury

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Basically, Andy - we are just following what our continental chums do as a matter of course - the idea of a foundation electrode and supplemented by a perimeter electrode is pretty common practice

In many buildings there will be a LPS system so this "electrode" we are all worrying about already exists

What doesn't translate well is how we apply it to:

1 - New dwellings (not usually provided with LPS

2 - Existing Buildings generally

I do sympathise with JPEL64 on this particular issue - harmonization with CENELEC is going to be a nightmare to implement - but they have to start somewhere

While I can see the value in harmonizing requirements, there's little point harmonising the detail of techniques if the environment isn't comparable. The UK differs in a number of other ways too:

We have higher current supplies - typically up to 100A single phase - whereas continental practice I think tends to go 3-phase at a much lower level - maybe 32 or 40A - with the result that they typically have much lower N currents per installation (at least domestic), so even when a CNE is used (Germany?), a much higher resistance electrode might be successful at keeping touch voltages down.

Our moist climate means simple rods are usually quite sufficient for TT earthing - I guess the same may not be true for the more arid areas of southern Europe - so maybe they'd need foundation electrodes and/or perimeter tapes to get a reliably low-enough-for-TT resistance.

Continental building practices I believe make much more use of steel reinforcement for foundations (not sure if it's for seismic reasons or just a drier climate means there are fewer worries about corrosion below d.p.c. level) - so it's often convenient to use the steel as an electrode as it's already there. In the UK I've never seen steel reinforcement on ordinary domestic foundations - it's all just plain concrete. I'm sure it must be used for some difficult sites even for domestic and of course in bigger 'civil' stuff, but I doubt that the traditional UK housebuilder - especially the smaller ones - is going to be easily persuaded to put corrodible steel into the very foundations of their work.

Our tradition of DNO supplied earthing facility usually means that the "equipotential zone" (i.e. the high voltage during an earth fault) could be constrained within the building - so an earth fault within the building on a TN supply typically meant that there wasn't a significant step voltage imposed on the ground surrounding the building - so no need for additional perimeter electrodes (assuming of course any metallic service pipework is buried reasonably deeply). Presumably the same couldn't be said for regions that have used a version of TT since before the advent of RCDs,

- Andy.
 01 August 2017 11:07 PM
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sparkingchip

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Regulation 542.2.2
Another significant change to Part 5 is a new note that strongly recommends the provision of a foundation earthing system in new buildings. Regulation 542.2.3 requires that, where foundation earthing earth electrodes are installed, the materials and dimensions of the earth electrodes are to be selected so that they can withstand corrosion and have adequate mechanical strength.
The installation of a foundation earthing system has been a requirement in a number of other countries around the world for some time. In Germany the primary purpose behind installing foundation earthing systems is to improve earth fault loop impedance for TT systems. However, there are some other benefits, including the reduction of potential difference between the general mass of Earth and any exposed- or extraneous-conductive-parts in the event of a PEN conductor failure.
This means that electrical installers will have to consider installing a foundation earthing system in new installations, if it is reasonably practicable to do so.
Impact of he 18th edition. Wiring Matters July 2017.

No mention of 542.1.201

Andy Betteridge
 02 August 2017 12:20 PM
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OMS

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Agreed AJ - this is JPEL64 "having a go" at implementing commonality of solution across the EU without being absolutely clear and robust about what's required - as I said, the daren't put values to this as the impacts will be enormous across sectors that probably aren't intended to fall into the requirements

I think this is an attempt to introduce into regulations what IEE have provided as guidance for a number of years - ie bang in a rod when you have PME - it'll be safer (but not by much) and we don't lose the PEN conductor that often (and it's against the law for a distributor to allow it to happen anyway)

From a practical perspective, getting down to the impedances required to limit touch voltages to 50V is a very onerous task

As an example, I've just looked back at my earthing design for a twin transformer 1.5MVA (firm substation) - typically I have a mass of reinforced concrete giving about 6 Ohms and a perimeter tape system with 3.6m driven electrodes connected to the slab edges and collectively we have about 4.7 Ohms - that's more than enough to get the impressed voltages from an 11kV fault down under 430V (the system has a parallel set of 4Ohm LER's at the 132kV intake and has a cabled earth running with the HV supply cabling (x2)

This is in reasonably difficult ground at around 200 Ohm - metres

If you apply that amount of earthing to a single phase 100A supply to a dwelling, you are still miles adrift of the values required for 50V

This is the reason why we don't (currently) state a limiting voltage - in practice 100V or 120V is a "bit" safer than no local electrode - but it's not "safe" by any means

Personally I've no problem with foundation (and perimeter ditch tapes) as supplementary earthing on new builds - but I wouldn't want to guarantee the outcome is under 50V without getting into a ridiculous extent of electrode

In practice, we could achieve much the same level of safety by two means:

1 - Move to TT systems or TN-S systems

2 - Provide lost neutral detectors with a second RCD when we use Ariel or UG PME systems - we've discussed this before with particular reference to deployment by ESKOM in SA when they were getting appalling problems with lost neutrals due to ANC activity, weather etc

I think 2 would need legislative intervention to force the supply side to install and maintain these - or if not some arrangement that allowed connection prior to the N_E link at the cutout (and then we have all the issues of switching a PEN conductor to resolve)

It's not credible we are going to abandon PME at this point

Regards

OMS

-------------------------
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 02 August 2017 12:22 PM
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OMS

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But how common is TNCS-PME earthing in the rest of Europe, TT electrodes are a different all game.


Pretty common in many built up areas - particularly in Germany

Regards

OMS

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 02 August 2017 02:45 PM
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rocknroll

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Originally posted by: OMS

Agreed AJ - this is JPEL64 "having a go" at implementing commonality of solution across the EU without being absolutely clear and robust about what's required - as I said, the daren't put values to this as the impacts will be enormous across sectors that probably aren't intended to fall into the requirements

I think this is an attempt to introduce into regulations what IEE have provided as guidance for a number of years - ie bang in a rod when you have PME - it'll be safer (but not by much) and we don't lose the PEN conductor that often (and it's against the law for a distributor to allow it to happen anyway)

From a practical perspective, getting down to the impedances required to limit touch voltages to 50V is a very onerous task

As an example, I've just looked back at my earthing design for a twin transformer 1.5MVA (firm substation) - typically I have a mass of reinforced concrete giving about 6 Ohms and a perimeter tape system with 3.6m driven electrodes connected to the slab edges and collectively we have about 4.7 Ohms - that's more than enough to get the impressed voltages from an 11kV fault down under 430V (the system has a parallel set of 4Ohm LER's at the 132kV intake and has a cabled earth running with the HV supply cabling (x2)

This is in reasonably difficult ground at around 200 Ohm - metres

If you apply that amount of earthing to a single phase 100A supply to a dwelling, you are still miles adrift of the values required for 50V

This is the reason why we don't (currently) state a limiting voltage - in practice 100V or 120V is a "bit" safer than no local electrode - but it's not "safe" by any means

Personally I've no problem with foundation (and perimeter ditch tapes) as supplementary earthing on new builds - but I wouldn't want to guarantee the outcome is under 50V without getting into a ridiculous extent of electrode

In practice, we could achieve much the same level of safety by two means:

1 - Move to TT systems or TN-S systems

2 - Provide lost neutral detectors with a second RCD when we use Ariel or UG PME systems - we've discussed this before with particular reference to deployment by ESKOM in SA when they were getting appalling problems with lost neutrals due to ANC activity, weather etc

I think 2 would need legislative intervention to force the supply side to install and maintain these - or if not some arrangement that allowed connection prior to the N_E link at the cutout (and then we have all the issues of switching a PEN conductor to resolve)

It's not credible we are going to abandon PME at this point

Regards

OMS


LOL If you remember we put all these proposals before your aged friends in Aug 1982 who rejected it, but we got there eventually, took a while.

Regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 02 August 2017 04:56 PM
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OMS

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LoL - they were never my friends, RnR

In '82 I was more interested in listening to the Smiths, wondering which of the Scottish isles were called the "Falklands" and shaking my head at my Aunt, who was at Greenham Common and, of course, beer and girls. I think the key phrase was "Get in line, son - there's 3 million waiting"

Although I do know of the proposals recommended by the "PME" working group to which you refer

Millbank never really clicked with DTI as far as I could tell

Still, better never than far too late, eh

Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 02 August 2017 05:04 PM
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rocknroll

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Originally posted by: OMS

LoL - they were never my friends, RnR



In '82 I was more interested in listening to the Smiths, wondering which of the Scottish isles were called the "Falklands" and shaking my head at my Aunt, who was at Greenham Common and, of course, beer and girls. I think the key phrase was "Get in line, son - there's 3 million waiting"

Although I do know of the proposals recommended by the "PME" working group to which you refer

Millbank never really clicked with DTI as far as I could tell

Isn't that the truth, on reflection perhaps it was me and my naivety as a keen youngster being thrown in amongst the old wolves who had some very long teeth that they loved to bare.

Still, better never than far too late, eh

Regards

OMS


-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 02 August 2017 05:12 PM
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OMS

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I think we used to describe it as "Character Building" in those days, Rock - or so they told us anyway

Weakness was LoMF - complaint was LoMF - explanations were never forthcoming (need to know, old son - and you don't need to know)

What a bloody circus

OMS

-------------------------
Let the wind blow you, across a big floor.
 02 August 2017 05:16 PM
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rocknroll

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Originally posted by: OMS

I think we used to describe it as "Character Building" in those days, Rock - or so they told us anyway

Weakness was LoMF - complaint was LoMF - explanations were never forthcoming (need to know, old son - and you don't need to know)

What a bloody circus

OMS


Yes, that about sums it up Grasshopper!

Regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 02 August 2017 06:17 PM
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sparkingchip

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I presume the Australian and New Zealand approach of using MEN isn't or never was on the agenda.

Andy B.
 03 August 2017 08:34 AM
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sparkingchip

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Don't forget that there is always some voltage on the majority of DNO PME earth terminals.

Voltage on PME discussion December 2014

With the Australian MEN I would guess there my be four times the number of electrodes compared to the UK system, but it still won't achieve the requirements of this new regulation.

Andy B
 02 August 2017 06:47 PM
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OMS

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Quite the opposite - basically what they call a Multiple Earthed Neutral (MEN) system is the same as a Protective Multiple Earthed (PME) system

Regards

OMS

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 02 August 2017 07:25 PM
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sparkingchip

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Originally posted by: OMS

Quite the opposite - basically what they call a Multiple Earthed Neutral (MEN) system is the same as a Protective Multiple Earthed (PME) system



Regards



OMS


If we were in Australia my understanding is that my installation would have a earth conductor taken from the DNO terminal and looped unbroken through the installation main earth terminal to a installation electrode, as would every one of my neighbours. So we would benefit from the abundance of electrodes with one at every installation, whereas here in the UK four installations could be sharing one DNO electrode buried at a joint.

Doing it that way in Australia they don't need to achieve the exceptionally low Ra on each installation earth electrode as there is the assumption you will benefit from the proximity of your neighbours electrodes. Using a loop tester 10 to 50 ohms is expected as a likely result.

https://www.southernshores.org/wp-content/uploads/2017/02/Australian-standards.pdf

Andy B
 02 August 2017 07:06 PM
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dustydazzler

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One is using the neutral as the earlth and the other one is using the neutral as the earth. Sounds similar to me.
What is the one where if you haven't got a neutral they whack it in with the earth terminal on final circuits and the like ??
 02 August 2017 09:11 PM
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AJJewsbury

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Doing it that way in Australia they don't need to achieve the exceptionally low Ra on each installation earth electrode as there is the assumption you will benefit from the proximity of your neighbours electrodes.

All depends on where the break in the CNE is - if it's on your own feeder then it's your load vs your electrode alone - just like we've been calculating for. If the break upstream of several installations then you have the benefit of several electrodes, but they've got to deal with the load of several installations, so only a little better in that it's a little less likely that all the installations will be drawing max demand at the same time. What makes it work at lot better is 3-phase distribution so that under max load conditions the N will naturally hover around zero automatically and worst case unbalanced is only about a 3rd of the load of the single phase situation (provided you've not set fire to the installations on the lower loaded phases by that point of course)..

- Andy.
 03 August 2017 08:31 AM
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Zoomup

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"As I have said on here before; every time the regs change the earthing regulations change. That tells me that even the great and the good still haven't got to grips with it."

Yes Zog, the Earthlings are trying to make their varying types of Earth dust reliably electrically conductive at their low Voltage. Foolish creatures. Only on Planet Xenontium does the ground dust conduct electricity. The Earthlings have no chance. They are hitting their carbon based heads against a brick Earth wall.

Celuss.
 03 August 2017 07:07 PM
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weirdbeard

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Andy B, when the suppliers or whatevers main earth connection fails on the non BS7671 side of things, the BS7671 installation would default to a TT earthing arrangement, so the preferred method of earth fault protection is an RCD?

-------------------------
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 03 August 2017 10:02 PM
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sparkingchip

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Originally posted by: weirdbeard

Andy B, when the suppliers or whatevers main earth connection fails on the non BS7671 side of things, the BS7671 installation would default to a TT earthing arrangement, so the preferred method of earth fault protection is an RCD?



Yes, if it is TNS.

No, if it is TNCS, then the DNO earth terminal and everything connected to it gets livened up without tripping the RCD.

Andy B.
 03 August 2017 07:37 PM
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AJJewsbury

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when the suppliers or whatevers main earth connection fails on the non BS7671 side of things, the BS7671 installation would default to a TT earthing arrangement

Not really - because the suppliers use a combined neutral & earth (a.k.a. PEN) - if the earth is lost then so in neutral and the severed N is still connected to the MET at the consumer's end and so livened up by the connected loads - all very un TT like (other than a TT system with a broken supply N, a N-PE fault and no RCD upstream of the fault)
- Andy.
 03 August 2017 08:18 PM
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weirdbeard

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Originally posted by: AJJewsbury

when the suppliers or whatevers main earth connection fails on the non BS7671 side of things, the BS7671 installation would default to a TT earthing arrangement


Not really - because the suppliers use a combined neutral & earth (a.k.a. PEN) - if the earth is lost then so in neutral and the severed N is still connected to the MET at the consumer's end and so livened up by the connected loads - all very un TT like (other than a TT system with a broken supply N, a N-PE fault and no RCD upstream of the fault)



Hi AndyJ, to quote AndyBs OP the issue is the failure of the connection between the supplied earth terminal and the BS7671 installation "in the event of the loss of the main connection to Earth. "

The failure of the suppliers neutral connection is an entirely different matter?

-------------------------
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 03 August 2017 10:10 PM
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sparkingchip

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Originally posted by: weirdbeard

Originally posted by: AJJewsbury



when the suppliers or whatevers main earth connection fails on the non BS7671 side of things, the BS7671 installation would default to a TT earthing arrangement




Not really - because the suppliers use a combined neutral & earth (a.k.a. PEN) - if the earth is lost then so in neutral and the severed N is still connected to the MET at the consumer's end and so livened up by the connected loads - all very un TT like (other than a TT system with a broken supply N, a N-PE fault and no RCD upstream of the fault)







Hi AndyJ, to quote AndyBs OP the issue is the failure of the connection between the supplied earth terminal and the BS7671 installation "in the event of the loss of the main connection to Earth. "



The failure of the suppliers neutral connection is an entirely different matter?


The is a diagram in this Presentation by Charles Tanswell

Which appears to be the only information available on the internet regarding this proposed regulation.

Andy B.
 04 August 2017 10:53 AM
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whjohnson

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One thing which is being overlooked.
The actual practicalities & extra costs associated with fitting spikes.

It's fine to theorise about the numbers/values etc, but how practical would it really be unless the job was a new-build with metalwork already present? (and exposed via a purposely welded-on lug ready to connect to)

To me, this is just treating one symptom of the DNOs not spending enough on maintaining their networks, and not the root cause - if the frequency of 'lost neutrals' has actually increased as reported in the article posted by sparkingchip.

If a neutral is lost, then surely this suggests that the condition of the line conductor won't be far behind, so why not do a bit of preventative maintenance instead.. After all, they wallop everyone with a 'standing charge' on our electricity bills for such purposes don't they?

I agree with the sentiment expressed earlier in the thread.
This is about yet another risk (and costs) transfer to the Little Man at the bottom of the inverted pyramid.

Oh they say we have to inspect & report upon the condition of their equipment but they won't allow us to pull the fuse, then they want £160 to fit an isolator - I requested that one be fitted last week whilst the customer was having a 'not-so-smartmeter' fitted, yet the guy said although he had some in the van he couldn't fit one without official say-so and a separate visit would have to be made!

And now it would appear that they are transferring their responsibilities for maintaining/checking/supplementing their earthing terminals.

I suppose the next thing will be that we'll have to go out and take high access courses so that we can safely climb their pylons to check those too.

Madness! Absolute madness. I hope that this one is headed off at the pass well before it makes it into the next bumper book of fun.
At 57, I'm too young to retire, yet too old and wise to put up with much more of this impractical nonsense.

-------------------------
Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.

Edited: 04 August 2017 at 11:06 AM by whjohnson
 04 August 2017 11:48 AM
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Parsley

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I found a NAPIT youtube 18th draft presentation.
They very briefly mentioned 542.1.201 about 14 mins in, but made no comment about how they believe it will be implemented or difficulties in installing electodes in existing installations.

Regards
 04 August 2017 05:49 PM
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weirdbeard

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Originally posted by: sparkingchip

Originally posted by: weirdbeard

Originally posted by: AJJewsbury

when the suppliers or whatevers main earth connection fails on the non BS7671 side of things, the BS7671 installation would default to a TT earthing arrangement


Not really - because the suppliers use a combined neutral & earth (a.k.a. PEN) - if the earth is lost then so in neutral and the severed N is still connected to the MET at the consumer's end and so livened up by the connected loads - all very un TT like (other than a TT system with a broken supply N, a N-PE fault and no RCD upstream of the fault)



Hi AndyJ, to quote AndyBs OP the issue is the failure of the connection between the supplied earth terminal and the BS7671 installation "in the event of the loss of the main connection to Earth. "

The failure of the suppliers neutral connection is an entirely different matter?


The is a diagram in this Presentation by Charles Tanswell



Which appears to be the only information available on the internet regarding this proposed regulation.



There are at least two connections that can fail within the DNOs typical grey 100A sealed PME supply head that could cause the main earth to the installation to fail without the neutral supply being compromised.

Failure of the neutral where PME conditions apply has traditionally been dealt with by fitting an insulating insert between the PME connected pipes and the outside tap, or similar, and inside we have bonding.

What has changed that has increased the danger?

-------------------------
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 03 August 2017 08:06 PM
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whjohnson

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Well, regardless of whatever the numbers are, this one is wholly impractical to implement.
I strongly suspect that this reg won't be implemented in many cases, simply because it is not practical to do so.

How the hell can you go round banging 1 metre+ long metal spikes everywhere in a heavily urban environment?

I can see thousands of insurance claims going in for ruptured gas/water mains/sewage pipes/fibre optic cables et al.

In my locale, it is nigh on impossible to get rods in anywhere due to the rocky ground, hence why I get every TT supply I encounter converted to PME.

Finally, why? (if true) is a UK regulating body attempting to 'harmonize' with an entity whose regime we have elected to depart from via BREXIT?

-------------------------
Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.

Edited: 03 August 2017 at 08:48 PM by whjohnson
 04 August 2017 03:49 PM
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sparkingchip

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One question I should have asked a few weeks ago, it this proposed regulation is harmonisation, what does the regulation it is harmonising with actually say; and exactly which regulation is it?

Andy Betteridge.
 04 August 2017 04:30 PM
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weirdbeard

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Originally posted by: sparkingchip

One question I should have asked a few weeks ago, it this proposed regulation is harmonisation, what does the regulation it is harmonising with actually say; and exactly which regulation is it?



Regs of the 200 series apply to the UK only, and not to other countries that use bs7671.... Doesn't seem very harmonisational?

-------------------------
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 04 August 2017 06:00 PM
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weirdbeard

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We are still waiting for the IET guide to consumer units following bs7671 amendment 3, and the ESF guidance made a mockery of the regulation in their related Best practice guide, Charles tans well is a director of ESF......

-------------------------
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 04 August 2017 08:18 PM
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weirdbeard

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 05 August 2017 12:05 AM
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whjohnson

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Well folks,
Having had access to some info not available in the public domain, it seems that the principle driver behind this one is undersized supply cables and increased demand - hence the increase in burnt off neutrals.
Not at liberty to disclose further, but suffice to say that the info has endorsed my earlier suspicions about the lack of will to invest in the network infrastructure.
So there we have it - risk transfer at work from the Big Boys to the smallest kids in the pack.

-------------------------
Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
 05 August 2017 03:04 AM
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MWalker86

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Originally posted by: whjohnson

Well folks,

Having had access to some info not available in the public domain, it seems that the principle driver behind this one is undersized supply cables and increased demand - hence the increase in burnt off neutrals.

Not at liberty to disclose further, but suffice to say that the info has endorsed my earlier suspicions about the lack of will to invest in the network infrastructure.

So there we have it - risk transfer at work from the Big Boys to the smallest kids in the pack.


OOOoohhhhoohh
 05 August 2017 09:09 AM
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Zoomup

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Originally posted by: whjohnson

Well folks,

Having had access to some info not available in the public domain, it seems that the principle driver behind this one is undersized supply cables and increased demand - hence the increase in burnt off neutrals.

Not at liberty to disclose further, but suffice to say that the info has endorsed my earlier suspicions about the lack of will to invest in the network infrastructure.

So there we have it - risk transfer at work from the Big Boys to the smallest kids in the pack.


So then, what will happen when a lot of us have shiny new electric vehicles and install nice new 30 to 50 Amp. chargers at our homes?
Perhaps we should let the train take the strain?

Z.
 05 August 2017 11:49 AM
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sparkingchip

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There is legislation covering the DNO installation.

9.2.b is written into law in The Electricity Safety, Quality and Continuity
Regulations 2002 , the proposed BS 7671 regulation 542.1.201 is an entry in a code of practice for electrical installation designers and installers. It is totally impractical for installation electricians to start trying install sufficient earth electrodes to meet the design requirements of 542.1.201.

So what happens if this is tested in a court of law if there is a fatality due to someone being electrocuted within their home following the failure of the DNO PEN conductor?

General requirements for connection with earth
8. - (1) A generator or distributor shall ensure that, so far as is reasonably practicable, his network does not become disconnected from earth in the event of any foreseeable current due to a fault.

Protective multiple earthing
9. - (1) This regulation applies to distributors' low voltage networks in which the neutral
and protective functions are combined.
(2) In addition to the neutral with earth connection required under regulation 8(3)(b) a distributor shall ensure that the supply neutral conductor is connected with earth at -
(a) a point no closer to the distributor's source of voltage (as measured along the distributing main) than the junction between that distributing main and the service line which is most remote from the source; and
(b) such other points as may be necessary to prevent, so far as is reasonably practicable, the risk of danger arising from the supply neutral conductor becoming open circuit.
(3) Paragraph (2)(a) shall only apply where the supply neutral conductor of the service line referred to in paragraph (2)(a) is connected to the protective conductor of a consumer's installation.
(4) The distributor shall not connect his combined neutral and protective conductor to any metalwork in a caravan or boat.

Andrew Betteridge
 05 August 2017 12:55 PM
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sparkingchip

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I am not convinced that, although the introduction of this regulation has a claim of being harmonisation, that it is generally done on TNCS- PME systems in German electrical installations in a manner that would fulfill the wording of 542.1.201; which as pointed out above is a UK specific regulation being a 200 series regulation.

SUPPLY
May be single phase (230 V-50 Hz) or - in the majority of cases -
3 phases (400 / 230 V-50 Hz).
Max. Tolerance (voltage): + 6% / -10%. TN- and TT- systems are
in use. TT- systems are the most common in domestic installations. There is usually one meter. Facilities are provided with
a second meter for special
tariffs, etc.
A fuse isolator unit allows all phases to be cut-off, isolating
the whole domestic installation.

Legrand


Andrew Betteridge
 05 August 2017 03:57 PM
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weirdbeard

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Originally posted by: sparkingchip

I am not convinced that, although the introduction of this regulation has a claim of being harmonisation, that it is generally done on TNCS- PME systems in German electrical installations in a manner that would fulfill the wording of 542.1.201; which as pointed out above is a UK specific regulation being a 200 series regulation.



SUPPLY

May be single phase (230 V-50 Hz) or - in the majority of cases -

3 phases (400 / 230 V-50 Hz).

Max. Tolerance (voltage): + 6% / -10%. TN- and TT- systems are

in use. TT- systems are the most common in domestic installations. There is usually one meter. Facilities are provided with

a second meter for special

tariffs, etc.

A fuse isolator unit allows all phases to be cut-off, isolating

the whole domestic installation.



Legrand


Andrew Betteridge


How about requesting a disjoncture differential from the supplier if we are harmonising with France?

-------------------------
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 05 August 2017 06:59 PM
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sparkingchip

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From the Legrand website it appears not all circuits are protected by an 30 mA RCD, just a upfront 500 mA RCD.

It does say this though, which if it is referring to TT makes it MEN:

t EARTHING
Earthing is local, usually through
a foundation earthing arrangement. All metallic services shall be bonded (gas and water pipe, heating, waste systems, etc.) with
a 10 mm2. In bathrooms the local equipotential bonding could have
a cross sectional area of 4 mm2. Neutral is re-earthed in the control panel. A protective conductor
is distributed to all socket outlets.
 05 August 2017 08:28 PM
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Zoomup

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+ 6% -10%? Really?

Z.
 06 August 2017 12:21 AM
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sparkingchip

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Originally posted by: Zoomup

+ 6% -10%? Really?



Z.


No, that may not be right.

Andy B
 06 August 2017 12:27 AM
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sparkingchip

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Originally posted by: sparkingchip

Originally posted by: Zoomup



+ 6% -10%? Really?







Z.




No, that may not be right.



Andy B


Or maybe it is as they stated the voltage at 230 V not 220V.

Time for bed!
 06 August 2017 09:18 PM
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sparkingchip

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Originally posted by: sparkingchip

Originally posted by: sparkingchip



Originally posted by: Zoomup







+ 6% -10%? Really?















Z.








No, that may not be right.







Andy B




Or maybe it is as they stated the voltage at 230 V not 220V.



Time for bed!


Classic harmonisation.

We'll say that voltage is 230 volts all across Europe, even though no one supplies electricity at 230 volts, then alter the permitted parameters to suit.

Andy B.
 06 August 2017 08:10 PM
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whjohnson

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In case I missed it, no one has answered the question as to why we are trying to harmonize with an entity we are departing from?

I am hoping that we tell the likes of CENLEC to do one post-BREXIT, and revert back to our own way of doing things.

-------------------------
Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
 06 August 2017 09:13 PM
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sparkingchip

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Originally posted by: whjohnson

In case I missed it, no one has answered the question as to why we are trying to harmonize with an entity we are departing from?



I am hoping that we tell the likes of CENLEC to do one post-BREXIT, and revert back to our own way of doing things.


As pointed out above, this is a 200 series UK only regulation, but then Germany and harmonisation is mentioned in the same breath as foundation earthing.

So I am unclear where harmonisation starts and finishes.

Andy B.
 07 August 2017 08:45 PM
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iie63674

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Originally posted by: whjohnson

In case I missed it, no one has answered the question as to why we are trying to harmonize with an entity we are departing from?



I am hoping that we tell the likes of CENLEC to do one post-BREXIT, and revert back to our own way of doing things.


CENELEC is not part of the EU. The UK was a member of CENELEC before the EU existed, and will remain a member after Brexit.
 07 August 2017 09:10 PM
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psychicwarrior

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@whjohnson "...but suffice to say that the info has endorsed my earlier suspicions about the lack of will to invest in the network infrastructure...."

Oh... and electric prices are rising because [mainly] transmission costs are increasing [re:Brit.Gas/Centrica]. Lack of will in favour of executive bonus and profits, or that it really is [the network] past its sell by date (or both).
 07 August 2017 10:47 PM
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sparkingchip

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So why not be honest and say it is recommended that all new installations should be direct TT earthed and it is recommended that existing installations are converted to TT?

Possibly because the DNO have a legal requirement to maintain the PME earthed network in a safe condition and questions could be asked as to whether they have fulfilled their legal requirement.

Or would be be an admission that in the past substandard materials have been used and maybe it was a mistake converting some TNS systems to PME?

Andy Betteridge
 07 August 2017 10:51 PM
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MWalker86

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I do wonder how much copper a TN-C-S system really saves. That is really the only reason I can see for doing it.
 07 August 2017 11:54 PM
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whjohnson

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CENELEC is not part of the EU. The UK was a member of CENELEC before the EU existed, and will remain a member after Brexit.


So, are you saying that european companies such a Legrand, Schneider etc don't lobby the eu depts concerned for new directives which favour their industries/products via CENLEC?

-------------------------
Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
 10 August 2017 09:13 PM
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iie63674

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Originally posted by: whjohnson

CENELEC is not part of the EU. The UK was a member of CENELEC before the EU existed, and will remain a member after Brexit.




So, are you saying that european companies such a Legrand, Schneider etc don't lobby the eu depts concerned for new directives which favour their industries/products via CENLEC?


No, I'm not saying anything about lobbying or EU Directives, just pointing out that CENELEC membership does not depend on membership of the EU.
Why would Legrand, Siemens, etc lobby for EU Directives when they can just propose changes to the CENELEC standards?
 12 August 2017 12:34 PM
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sparkingchip

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I think this discussion has covered virtually every aspect of the proposed regulation, some particularly relevant and some less so.

Not one person has come out and said it is a viable option to leave this regulation in the bode of practice BS 7671 as it has been written. This begs the question, how did it make it into the draft as it is written at present?

It should be safe to assume that it won't stand up to scrutiny as a proposal as the engineering required is not practical from a installation or cost perspective. But the committee that has to do the final scrutiny are presumably the same committee that let it get into the draft in the first place.

I commented on the BSI website that it should be dropped as it is ridiculous. Presumably having seen a IET comment on how to submit your opinions, my comment that it is ridiculous will not be considered as it is not constructive.

However I am leaving it at that and not contacting them again, as I feel that my comment is justified and I should not as a local jobbing electrician have to explain the practicality of installing an earth electrode system to comply with the proposed regulation to the engineers on the JPEL64 committee.

If it is a practical solution to a problem electricians would have been doing it for many years.

So perhaps it is time to stand back and see what sort of a silk purse they can make out of a sows ear!

I await the first article in the IET and trade magazines telling us how to implement this regulation if it is brought in with great interest to see what compromises are made for the realities of life and electrical engineering.

Andrew Betteridge
 03 October 2017 11:11 AM
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sparkingchip

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Cable Talk Magazine

Chapter 54: Earthing arrangements and protective conductors
As mentioned earlier in this article, Regulation 542.1.201 now requires an earth electrode supplementing any earth facility provided by the distributor (TN-S or TN-C-S systems) to prevent dangerous touch voltages in the event of the loss of the main connection to earth.

Regulation 542.2.2, which provides requirements for earth electrodes, is planned to be amended with a note advising that for new buildings, the provision of a foundation earth electrode is strongly recommended.

This proposal appears to be a simple solution to the problems that can occur during faults where loss of neutral in PME supplies
has occurred.

However, very low earth electrode resistance values will need to be achieved to keep the touch voltage at a safe value and this may not be so easy to achieve.
 12 August 2017 01:42 PM
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weirdbeard

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AndyB, looks like there was a Paul Cook wiring matters article in autumn 2002? on this topic, according to this past topic:

http://www.theiet.org/forums/f...tid=205&threadid=16985

-------------------------
:beer)
 12 August 2017 02:22 PM
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whjohnson

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It should be safe to assume that it won't stand up to scrutiny as a proposal as the engineering required is not practical from a installation or cost perspective.


Wholly agree - the cost/benefits do not stand up to scrutiny at any level, other than that of the DNOs divorcing the cost of responsibility for the maintenance of their earthing facilities.

It should be dropped forthwith, and the numpties who dreamed up the idea should be taken outside and beaten to death with a 'stupid-stick'!

-------------------------
Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
 12 August 2017 04:40 PM
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sparkingchip

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Originally posted by: weirdbeard

AndyB, looks like there was a Paul Cook wiring matters article in autumn 2002? on this topic, according to this past topic:



http://www.theiet.org/forums/f...tid=205&threadid=16985


I see the link no longer works, I assume it would be similar in content to the Article I referenced earlier in these discussions.

I saw a IET Wiring Matters article on Multiple earth rods for TT installations but they rely on a RCD for disconnecting the supply.

Andy B
 12 August 2017 02:25 PM
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dustydazzler

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I would bury the stupid idea in a big hole along with every tin (sorry fire proof) domestic consumer boards and chuck partpee in the hole for good measure
All are a complete waste of time and money
Rant Over
 12 August 2017 04:13 PM
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weirdbeard

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Originally posted by: dustydazzler

I would bury the stupid idea in a big hole along with every tin (sorry fire proof) domestic consumer boards and chuck partpee in the hole for good measure

All are a complete waste of time and money

Rant Over


It will probably just become a domestic only requirement, like the biscuit tin amd3 boards did after the DPC for that reprint, dumped on the shoulders of the small installers and end customers, with conflicting advice given in dribs and drabs from the various guidance experts, such as that given in the ESF BPG4 and the IETs own guide to consumer units :

http://electrical.theiet.org/b...no3/consumer-units.cfm

-------------------------
:beer)
 12 August 2017 07:29 PM
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geoffsd

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Originally posted by: weirdbeard

with conflicting advice given in dribs and drabs from the various guidance experts, such as that given in the ESF BPG4 and the IETs own guide to consumer units :


 12 August 2017 09:29 PM
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leckie

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Originally posted by: geoffsd

Originally posted by: weirdbeard



with conflicting advice given in dribs and drabs from the various guidance experts, such as that given in the ESF BPG4 and the IETs own guide to consumer units :


[IMG][/IMG]


Well of course you would mock such guidance Geoff
 13 August 2017 12:11 AM
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sparkingchip

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Considering that all that BS7671 said was that plastic consumer unit enclosures were no longer permitted in domestic installationse, so metal enclosures have to be used instead, there has been a huge amount of varied advice on what is actually required.

Andrew Betteridge
 13 August 2017 12:24 AM
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geoffsd

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Originally posted by: sparkingchip

Considering that all that BS7671 said was that plastic consumer unit enclosures were no longer permitted in domestic installationse, so metal enclosures have to be used instead, there has been a huge amount of varied advice on what is actually required.

It did not say that.

It said CUs must be of non-combustible material (or enclosed in) and stated that steel was an example of this.

No definition of non-combustible was given and all the manufacturers instantly started to make steel ones.

Quite odd.
 13 August 2017 12:42 AM
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sparkingchip

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Originally posted by: geoffsd

Originally posted by: sparkingchip



Considering that all that BS7671 said was that plastic consumer unit enclosures were no longer permitted in domestic installationse, so metal enclosures have to be used instead, there has been a huge amount of varied advice on what is actually required.


It did not say that.



It said CUs must be of non-combustible material (or enclosed in) and stated that steel was an example of this.



No definition of non-combustible was given and all the manufacturers instantly started to make steel ones.



Quite odd.


Quite true. I should have worded that correctly, though that was apparently the intended outcome according to the manufacturers.

Better quality plastic enclosures are not available, though die cast aluminium are, along with steel.

Andy B
 13 August 2017 12:56 AM
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MWalker86

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Originally posted by: geoffsd


No definition of non-combustible was given and all the manufacturers instantly started to make steel ones.


Because from a manufacturing perspective that is by far the simplest and most cost effective way to make something non-combustible.
 13 August 2017 06:46 PM
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iie63674

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Originally posted by: geoffsd




It said CUs must be of non-combustible material (or enclosed in) and stated that steel was an example of this.



No definition of non-combustible was given and all the manufacturers instantly started to make steel ones.



Quite odd.


Some manufacturers continued for a while to state that their plastic CUs met the flammability requirements of 61439-3 and so were sufficiently non-combustible, but the marketplace seemed to demand metal.
 13 August 2017 01:00 AM
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sparkingchip

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Again the IET and BSI committee have stated a outcome without stating a method, the result will be a shambolic message.

Andy Betteridge
 13 August 2017 01:30 PM
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whjohnson

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No change there then!

Is it just me, or has anyone else noticed that nothing in this country seems to work properly any more?

A sceptic might be forgiven for thinking that all of this nonsense is by design....

-------------------------
Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
 13 August 2017 07:06 PM
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geoffsd

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That was/is the trouble with the regulation.

It says CUs must comply with 61439-3 and be non-combustible.
 13 August 2017 07:32 PM
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iie63674

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Indeed, thus implying something over and above the requirements of the product standard.
 02 October 2017 11:25 PM
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sparkingchip

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I had a coffee this afternoon with someone who went to the Elex show at Coventry, so I casually enquired if he had sat in on the forum discussion and if earth electrodes had been discussed.

Unfortunately he hadn't sat in on the forum, so I am none the wiser, so can anyone else advise me as to whether the experts gave guidance on how to successfully achieve the requirements of the proposed regulation 542.1.201?

Andy Betteridge
 19 November 2017 09:40 PM
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mapj1

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Interesting and backs up other things I have seen, in that it points up that resistance does not improve in a predictable way with rod length, and you need to get a lot further away in terms of rod lengths to get the 3 point readings not to be confusing.
And any idea that the UK electrode practice of a single 4 foot rod in the front flower bed is good for much more than RCD tripping is fantasy in many soil types.

Must admit for the equivalent 230V test I'd not be kneeling that close to a live electrode and waving my arms like Kermit and nearly touching it, but it gives good a feel for how small an area is the "equipotential" zone around the top of the electrode, probably a meter diameter or so, and nearly all the voltage drop has happened.

-------------------------
regards Mike
 19 November 2017 10:37 PM
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sparkingchip

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I must admit there is a new carvery pub opening locally tomorrow and we had a free meal today as part of their staff training weekend. The plans to do alsorts of things this afternoon turned into a doze on the settee, then watching a few videos and reading.

I watched this one before the Mike Holt videos, rather different to our four foot rods in the flower bed regime.

25 ohms Ra appears to meet the code requirement, I'm not sure what I think about the phone and cable TV being connected to the pole earth conductor in the way they are. I do like the truck mounted rod driver, very similar to the fencing contractors crawler mounted post and stake driving gear.

I also like the comments about just attaching a earth electrode rod to the mains supply to see how much current will flow through it and people being wary of throwing the switch and then being surprised when there is not a flash and a bang as the circuit protective device blows, with the current merely flowing to earth without any drama. Not something to try at home!

Andy B.
 20 November 2017 09:30 AM
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mapj1

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It is interesting to see the relaxed attitude to the use of linear driven 50 odd feet of rods to achieve resistances that are probably still a factor of ten too high for the purposes of the new UK reg to be . Our water tables may tend to be higher, and it may well work in London or on Essex clay, but certainly not everywhere .
Note that in both this one and the Mike Holt video the resistances of 2 lengths one above the other are not anything like half the resistance of one length, more like 80% - this is partly (I think, based on messing with earths for Radio and things) due to dry topsoil and the use of joiners that are significantly fatter than the main rod. The hole above the joint is a much looser "fit" to the upper half of the electrode as the hole has been opened out by the joiner passing through. Actually if you wait for it to rain and the soil to close it improves the contact quite a bit This is less of a problem rodding into wetter ground, where the soil squelches shut much sooner after the joiner passes.

-------------------------
regards Mike
 21 November 2017 10:54 PM
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sparkingchip

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Connection

Maximum 1-phase load, or, for unbalanced load maximum overall load unbalance
Maximum customer earth electrode resistance bonded to the customer Main Earth Terminal
1-phase, unbalanced split- phase or unbalanced 3- phase

Less than or equal to 500W. 100 ohms

1kW. 50

2kW. 20

3kW. 18

4kW. 14

5kW. 11

6kW. 9

7kW. 7

Table 1 - Required Customer Earth Electrode Earth Resistance Versus Load

Western Power 2017
 22 November 2017 07:50 AM
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mapj1

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Well spotted, I did not have much of the WPD stuff, being out of area.

Seems to be based on accepting a maximum possible touch voltage of about half mains voltage exposed to touch without ADS.
That feels rather high compared to what BS7671 allows, especially if outdoors. Also assumes load is simple resistive, and not electronic and likely to try and draw more current as the voltage collapses.

1kW. 50ohms
the 1kW implies a load of 52 ohms, if division is resistive between load and earth electrode, a non cleared touch voltage of ~ 120V
....

7kW. 7ohms
7kW is a load of 7.5 ohms and again if division is resistive between load and electrodes, touch voltage of ~ 120V

Also of course no guarantee that the resistance on installation day will be maintained, it could go up or down over time.

Most houses have at least a 60A fuse, so should we call that a 14kW supply, (3.5 ohms) and often 100A = 23kW (~ 2 ohms).
And that is at rather more than the 50V touch voltage we normally allow. How many rods to reach an ohm or an ohm and a half anyone?

-------------------------
regards Mike


Edited: 22 November 2017 at 04:44 PM by mapj1
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