Neutral potential on TT system

[binky]

that isn't too unusual, inverters don't really like TT systems and often report a fault that isn't there. No doubt the recent dry weather has increased the rod reisistance as the ground dries out. No easy soultion to this issue, but banging a bigger rod in or some other improvements of that nature may well solve that problem. Be a liitle cautious handling the earthing, inverters tend to discaharge capacitors when shut down, which may explain the 30V you are seeing on the rod, given a highish resistance it can take time to disspate the dischareged energy from the capacitors

 

[Warwick]

The PV system is on a barn that is 25metres away from the house and thirty away from the domestic incomer and consumer unit, the inverter has been shut down for a while now until this problem is sorted out. I have also isolated the PV cables coming off the roof. Besides that if there was leakage from the inverter it would show in the consumer unit as DC, I have had that before with Fronius inverters. I take on what you say about the ground becoming less conductive, but I have put another rod in and looped the earth on to that, but there is no change. What is puzzling is that the voltage on the neutral side is consistent no matter what I do. The mains coming from the transformer which is down a field about 100 metres comes up poles to within ten metres of next doors property then splits at the pole and goes underground to feed next door and Norman's property which is ab out eighty metres from the pole. 

 

[Murdoch]

I’m reading as Warwick is Normanw sparks? 

So why didn't he write the response inn the first person.

I.e. I did ....

Still think it's all a bit odd that the dno says there is not a problem, yet the spark says there is .

Wonder where the dno used his tester and probes?

 

[Warwick]

I have not been there when the DNO's operatives have turned up, I am based about 40 miles from the property and they do not give a time when they can get there. I believe from Norman that they have tested at the incomer next to the meter at his property and they have tested at the transformer down in the field. At the transformer the reading was normal, at the meter the reading was the same as mine, and that was with the property disconnected. It all leads me to believe that there is a problem with the underground cables leading to the property, it is a difficult one to prove though.

 

[steptoe]

What's your Ra,?

And, you don't need a Neutral to test Ze,

 

[binky]

With regards to the PV, DC at CU - not what I am on about, When you shut the inverter down it will discharge capacitors down the earth to make safe. But if you have had it shut down for a while, it is unlikely to be linked to this problem.

 

[Normanw]

problem identified by DNO as L to N leak in supply cable between supply pole and house. Problem circumvented by switching to TNTS - new G wire fitted to supply pole and N &G tied together at house. PV system operating. DNO to further advise next steps - dig and repair cable or possibly a new supply. 

To be clear Warwick is my electrician but I didn’t realise it was him as I know him by another name!

So, DNO has concluded it is their issue over two weeks after categorically telling me it was mine, and “Warwick” was right.

Thanks for all your inputs and hope the feedback might be useful!

 

[binky]

we like feed-back, thank you.

 

[Murdoch]

Good feedback.... But you could have stated that the dno was coming back today!

 

[Normanw]

I didn’t know they were coming back! They just turned up. At least there are some conscientious people out there

 

[Murdoch]

I didn’t know they were coming back! They just turned up. At least there are some conscientious people out there

Maybe the chaps had had second thoughts about what they found ............. still all sounds very odd

 

[Andy™]

As I said above, the Supplier (electric board as they used to be called) checked incoming service cables with house disconnected when he was here, found 235 L-N and concluded it was my problem. Or did I misunderstand what you said, I’m a nuts and bolts engineer, not a sparky?

This is a rural location, we have no shared pipes or whatever with the neighbours. 

Thanks

I am being told the Ze cannot be measured because ther

I am being told the Ze cannot be measured because there is a live neutral???

L-N being 235 would be correct. however that still doesnt mean that the earth voltage is coming from inside your property

 

[binky]

if cable is damaged it could be I suppose?

 

[Normanw]

Ok, it’s drum roll time - and a round of applause for Andy! 

DNO back again today, having had animated discussions at the office, disconnected next door, no change. Disconnected next door but one - eureka, problem disappeared! 

Further investigation on their property revealed a bore hole pump issue. The tenant had been complaining to the owner for some time that there was an issue as it kept tripping out, but the owner told him to keep switching it back on!

So I am keeping the TNCS system, and hopefully the bore hole pump issue will be resolved, but apparently the DNO have no power to force a repair. I will try via my insurer to claim for electricians bills and loss of solar production, but I’m not holding my breath.

Thanks again all

Norman

 

[Tony S]

They have the power to disconnect a dangerous installation.