High Ze on tns supply

[Dave123]

That's not how it came across in your post, it read as though you were saying that it is not unreasonable for it to be left on as it has all RCBO's.

This comes across as you saying that nothing needs to be done about the high Ze at all because the RCBO's provide fault protection. It comes across this way as we all know that you simply cannot just turn a customers power off, regardless of what fault you have found,

Sorry I had meant for the time waiting for the DNO to arrive, I hadn't called then straight away as I wanted to check tester. As I hadn't contacted before so I expected it to take longer for them to attend.

Thanks

 

[UNG]

You may feel I overreacted but in recent years there is a growing reluctance with some electricians to contact the DNO when they find something like this which has the potential to be a bigger fault or issue in the local network which the DNO will have no knowledge of unless they are informed of issues that we find when we are at customers premises

Over the last 10 years I have been to a number of jobs where a high Ze has been previously "repaired" by others who not wanting to contact the DNO knocked an earth rod in and connected it to the MET. When found it can throw up some interesting results on one property a Zs test gave 37Ω on the rod connected to the MET the supply was looped from nextdoor so a knock nextdoor a another Zs check there was 37Ω so onto nextdoor and again you've guessed it 37Ω turns out the electrician who thought it less effort to knock a rod in had by connecting to the MET earthed another 6 - 8 houses which had also lost the DNO earth. So your "isolated" fault may have identified a fault that was affect any number of other properties nearby

 

[Dave123]

That’s fair enough. I genuinely didn’t know how quick they would come to a reading like that if at all, much better than expected.
Still seems weird to deteriorate over a few weeks that happened to be between my tests.

 

[UNG]

Still seems weird to deteriorate over a few weeks that happened to be between my tests.

That is how faults develop it can be ok one day and not the next
If it requires a dig to repair the fault you have found then there are any number of external influences could have caused or contributed to the fault as it is it looks likely you have found the fault in the early stages before a possible complete failure of the earth it is even possible that the fault you have found may be present in a number of ajacent properties

It is all part of the learning process and gaining experience the outcome here sounds like you have had a positive experience in dealing with the DNO which helps when you are in a similar situation in the future