An interesting read

[sparkticus]

True, but in my exchanges with Matt, I've been working on the basis of his drawings - which show the clamp meter bewteen cutout and MET/CU/bonding. With that arrangement, I really don't think one should see even a decrease (probably a small increase), let alone a 'disappearance', of the current when one connects an earth spike to the MET (or CU)- which, again, is where Matt said the earth spike was attached.

Aha, I'm on my mobile at the moment so can't see the drawing well or the picture too well. But with what you describe I would agree with you. In fact the temp spike may offer such a low Ra (relative to the impedance of this unorthadox path) that you may see a significant increase in current.

But to add to the mix, is Matt working on the basis of finding the direction of flow? which would make all the difference if the flow was from the other direction.

 

[JohnW2]

Aha, I'm on my mobile at the moment so can't see the drawing well or the picture too well. But with what you describe I would agree with you. In fact the temp spike may offer such a low Ra (relative to the impedance of this unorthadox path) that you may see a significant increase in current.

That's what I've been suggesting all along, so maybe Matt and I have been talking somewhat at cross-purposes as regards the arrangement (although I might have to blame some of his drawings for that )

Kind Regards, John.

 

[andrew1210]

I'm sorry, I am now officially 100% lost! lol

 

[JohnW2]

I'm sorry, I am now officially 100% lost! lol

Don't worry, you're in good company - but I think there have just been some misunderstandings between us and that we are actually all essentially saying/thinking the same thing. What matters to you is that I think there is probably a consensus that it's difficult to imagine what could be causing your problem other than a problem with the supply neutral.

Kind Regards, John.

 

[andrew1210]

Yeah, I'm not kidding, Scottish Power engineers literally stare into space for 5/10mins at a time trying to get there heads round it, fail and go away and send another team lol!

We should be used as a problem solving training exercise :L maybe use this thread as support material lol

 

[sparkticus]

a problem with the supply neutral.

Absolutely.

 

[JohnW2]

Yeah, I'm not kidding, Scottish Power engineers literally stare into space for 5/10mins at a time trying to get there heads round it, fail and go away and send another team lol!

It's difficult to understand why they're making such a meal of it. Physically finding the fault may, of course, not be so easy, but I don't think it's really rocket science (and certainly shouldn't be for them) to work out the probable nature of the problem; I would have thought that 'neutral faults' would be amongst the more common things they have to deal with.

Kind Regards, John.
Edit: typo corrected.

 

[andrew1210]

Exactly my point! I'm beginning to wonder if they are electricians!

 

[sparkticus]

Exactly my point! I'm beginning to wonder if they are electricians!

One or more of them probably are electricians/electrical engineers but sometimes people don't think to go back to basics. Its also sometimes not easy to go back to basics on the first visit due to time pressure etc.

As the problem increases in profile then eventually someone declares " we need to go back to basics" It seems like they may well be at that point now. Pity it was not earlier

Poor record keeping (inability to establish whether its TN-C-S or TT) only serves to cloud the problem further.

 

[JohnW2]

Poor record keeping (inability to establish whether its TN-C-S or TT) ...

There they surely are being daft. Now we've seen a piccie of the service head, we know the answer to that without any records - so presumably they must as well!

Kind Regards, John.

 

[sparkticus]

Poor record keeping (inability to establish whether its TN-C-S or TT) ...

There they surely are being daft. Now we've seen a piccie of the service head, we know the answer to that without any records - so presumably they must as well!

TN-C-S now apparently from the picture but (and I'm not in any way a network engineer) what was it before? Was it TN-S or TT?

If it was TN-S before then I am surprised that the problem exists since there would be two paths back to the supply transformer -the original neutral and -the original earth. Admittedly one path may have failed years ago and we are now seeing the other conductor fail. But in this case (and I have no idea if the DNO would do such a thing) was it originally TT? If so, the current TN-C-S may not have a separate earth which is usually bonded to the neutral at the cut-out.

Again, I don't have any DNO experience so there may be other ways that they handle a TT to PME conversion. But the confusion over records really make me suspicious

 

[andrew1210]

The confusion over records is actually alarming!

I think it may actually still be TT and the council wired these houses up wrong when they installed the CU shown in '79......

Another little lead, out a walk earlier.... by the end of the road there is a concrete manhole, approx 3 quarters/ft sq. "EARTH --- ROD"

I don't know if this is maybe for the street lighting though as it is opposite the first Leccy pole.... but near the base of the first street light.

 

[sparkticus]

TN-C-S now apparently from the picture but (and I'm not in any way a network engineer) what was it before? Was it TN-S or TT?

If it was TN-S before then I am surprised that the problem exists since there would be two paths back to the supply transformer -the original neutral and -the original earth. Admittedly one path may have failed years ago and we are now seeing the other conductor fail. But in this case (and I have no idea if the DNO would do such a thing) was it originally TT? If so, the current TN-C-S may not have a separate earth which is usually bonded to the neutral at the cut-out.

Again, I don't have any DNO experience so there may be other ways that they handle a TT to PME conversion. But the confusion over records really make me suspicious

Just clarify where I was going because on reflection I badly worded the above. Are we looking at an illegal PME here? PMEd by mistake in good faith way back back when? Yes PME at the cut-out but was the neutral evaluated for PME before it was done? Worst case it may even have a circuit breaker in the neutral somewhere

 

[andrew1210]

To summarise - As SP see it "I *should* (but no drawings) be TT

BUT - All 150 houses (wired in 1979 by council as all council at that time) wired like in pics. . .

 

[sparkticus]

To summarise - As SP see it "I *should* (but no drawings) be TT

BUT - All 150 houses (wired in 1979 by council as all council at that time) wired like in pics. . .

Yes, this is really interesting and quite exiting, OK I don't get out much

Would like to see the DNO/network guys comments on this.