What is ”substantially zero“?

Is it possible to differentiate between TN-S and TN-C-S using a test meter?

A bit more of a challenge from a couple of weeks ago ?

External. 

Looks like there's a wire that's been cut off and just left hanging hope it's not still live. Also what's that around the middle wire in the bottom picture?

The 3 wire overhead screams split phase TT, but the cut out says single phase, and perhaps smacks of previous overload when it was a hot wire fuse,  so the flying tail may have been the earth of over head TNS. I share your “ what on earth ?” moment.

I also wonder how the PVC fascia was installed under the insulator bracket. Well no not really, I imagine something was carefully dangled for the duration.

What does the meter suggest, in the sense of volts between the wires, apart from ‘are you wearing your running shoes?’ If that flying tail is another phase it is time to make a call.

Still someone installed that cut-out and thought the job good enough to seal up. After a pub lunch perhaps.

Mike.

Overhead TN-S in South Wales, I posted some pictures of a different installation where the earth wire was being used, at this one someone decided it would be a far better idea to make it TT and install an earth rod.

Thanks everyone for useful feedback. The Ze is 0.1R and Ipf is 2.4kA on the old EICR (I'll measure when I'm in next week as that seems suspiciously accurate), which would indeed indicate a N-E link outside somewhere close? Also I've asked WPD what they classify it as.

The CT is for a battery solar storage system in the loft.

MrFox: 
 

The CT is for a battery solar storage system in the loft.

Not always a good place for them (weight, temperature, fire safety, access for maintenance). BS 5839-6 recommends detection connected to interlinked system is installed if you do put batteries and/or power converting equipment in places like lofts.

MrFox: 
 

Thanks everyone for useful feedback. The Ze is 0.1R and Ipf is 2.4kA on the old EICR (I'll measure when I'm in next week as that seems suspiciously accurate), which would indeed indicate a N-E link outside somewhere close? Also I've asked WPD what they classify it as.

Sounds like it could well be PNB, especially given the DNO earthing terminal clue - if that is the case, PME conditions would apply.

@gkenyon I wouldn't have put it in the loft either, but hey. I've mentioned it already to the customer.
WPD came back with ‘It’s TN-S, that is what should be on the certificate'.