TNS Hybrid with PNB strap

I'm not seeing a obvious N-PE link in the pictures either - but as Mike say such things aren't uncommon - and most DNOs these say will say if asked "PME conditions apply" to just about any earthing facility they provide, whether it was originally TN-S or not.

   - Andy.

AJJewsbury said:

most DNOs these say will say if asked "PME conditions apply" to just about any earthing facility they provide, whether it was originally TN-S or not.

As Figure 2.1 of the OSG clearly shows, if the N-PE link is in the service head, the earthing conductor will emerge from the latter; whereas if there is no N-PE link, it is connected to the supply cable.

For SIGINT's benefit (as I have mentioned previously), my earthing at home looks very similar. However, Ze was excessive a few years ago. This is, apparently, normally due to deterioration in the connection between the street main and the supply cable. Rather than digging a hole in the highway and fixing the problem there, the DNO dug a hole in my lawn and linked N and PE there. So whilst the installation appears to be TN-S, it is in fact TN-C-S. (Or perhaps that should be TN-S-C-S?)

ETA: JP beat me to it whilst I was typing.

As Figure 2.1 of the OSG clearly shows, if the N-PE link is in the service head, the earthing conductor will emerge from the latter; whereas if there is no N-PE link, it is connected to the supply cable.

I fear the real world is a little messier than the OSG might suggest. E.g. series 6 cut-outs (e.g. https://www.wt-henley.com/pdf/14688_series_6_house_service_cut_outs_2.pdf) had a removable link within the cut-out - so without opening things you're not supposed to open you can't tell if there's a link in there or not - hence it could be either combined N/E (CNE) or separate earth wire (SEW) as the DNOs say (or SEW to the premises but CNE to some common point outside, as is apparently now the fashion for multiple supplies to steel frame buildings).

   - Andy.

Hi Andy!

Thank you for your reply!

The NPE is mechanically attached to both of the sheaths of the looped supply. The bitumen I am guessing has started to leak or is leaking hence the lead sheaths colour of a dark gray or black look. I’ve also found a rod outside the property. It’s corroded (obvious reasons) that is also connected to the MET Earth terminal block.

The “pine green” looking Earth from what I can tell is either 4mm2 or 6mm2 is also connected to something below the property where the PILC/PILS cable enters the property…I can’t verify because it’s very deep down and probably dangerous as it could damage the cable even further. 

The neutral is the same either 4mm2 or 6mm2. But it’s been wrapped around the mechanical strap of the sheath of both the looped supply and is connected to the same MET.

Theres parallel earth connects and a neutral altogether connected to the MET from my observation 

Hi Andy!

Thank you for your reply!

The NPE is mechanically attached to both of the sheaths of the looped supply. The bitumen I am guessing has started to leak or is leaking hence the lead sheaths colour of a dark gray or black look. I’ve also found a rod outside the property. It’s corroded (obvious reasons) that is also connected to the MET Earth terminal block.

The “pine green” looking Earth from what I can tell is either 4mm2 or 6mm2 is also connected to something below the property where the PILC/PILS cable enters the property…I can’t verify because it’s very deep down and probably dangerous as it could damage the cable even further. 

The neutral is the same either 4mm2 or 6mm2. But it’s been wrapped around the mechanical strap of the sheath of both the looped supply and is connected to the same MET.

Theres parallel earth connects and a neutral altogether connected to the MET from my observation 

I'm still missing something I think... traditionally the lead sheaths were just PE. N was a separate core inside (just like L). I can see the two cable sheaths strapped together (which would ensure next door's cable is Earthed) and to your MET - but that's all typical of a traditional TN-S arrangement (when looped).

    - Andy.

When the DNO technician came, one the first attempt. He removed the neutral cover of the cutout. I noticed two neutrals connected in There’s only room for two connections inside the cutout of the neutral brass terminal. Since it’s a looped supply neighbours and mine have consumed both screw terminals. So from what I’ve gathered they must of realised they can’t connect an earth to the brass terminal because of the looped supply. 

And what they’ve done is connected an Neutral to Earth bond using an mechanical connection to both of the sheaths of the looped and attached an 4/6mm2 neutral and earth “pine green tinned copper” and wired it back to the MET like a makeshift fix or TNCS conversion?

Thats what I’ve gathered from seeing him remove the neutral cover to replace the meter tails from the cutout side. But then again it makes an strange buzzing sound Low frequency arc like sound for 5-10 seconds then disappears… but like I’ve mentioned above I’ve had them out to the property 4x times and each time they don’t seem to be interested or wanting to fix or modernise their equipment. 

I do understand from a financial point of view probably cost them more than £10,000 to replace the PILC/PILS with an SNE Waveform or CNE concentric cable. It will eventually need to be replaced…Luckily I don’t have an electrical car or EV or Solar stuff…

SIGINT said:

And what they’ve done is connected an Neutral to Earth bond using an mechanical connection to both of the sheaths of the looped and attached an 4/6mm2 neutral and earth “pine green tinned copper” and wired it back to the MET like a makeshift fix or TNCS conversion?

Did you see them do it? That earthing conductor looks very old.

And what they’ve done is connected an Neutral to Earth bond using an mechanical connection to both of the sheaths of the looped and attached an 4/6mm2 neutral and earth “pine green tinned copper” and wired it back to the MET like a makeshift fix or TNCS conversion?

I'm probably being daft. but I'm still not seeing a link from your MET to the supply N ... (usually there are room for two outgoing Ns at the top - so they could perhaps have used one of those?) Might be they talked about adding a N-PE link but in the end just improved the straight PE connections?

    - Andy.