UK Interesting Problem !!

[Madhatter2]

I’d be keen to hear your thoughts on 1 of my customers problem.
Split board, TT system. Located in a village, neighbours report no problems.
Customer getting random tripping of sometimes 1, sometimes both RCCD’s. Totally random, no particular reason. I’ve tested the installation, nothing showing up out of the ordinary. Customer keeps a log of when these events occurs.
Tested both RCCB’s numerous times, nothing untoward. Replaced 1 with another known good 1, no difference. Moved some circuits around to try and find what’s tripping, and added another board with RCBO’s, fed from MCB from main board ( after main switch, before RCCB’s). These trip very occasionally.
Nw I’m starting to think that this maybe a supply fault, as sometimes the customer says the power comes back on without him resetting anything. Have known RCCBs to trip when power is restored, especially after a very small outage.
Ze is low for a TT around .14, measured many times.
Your thoughts gentlemen please.

 

[buzzlightyear]

If there is a supply fault then you should speak to the DNO.

 

[James]

when you say you have tested the installation, have you done any checks to see if there could be a N to E fault?

 

[timhoward]

Ze is low for a TT around .14, measured many times

That's not low it's exceptional! Unlikely to be related to the problem but is that with no parallel paths at all, just the Live and the isolated Electrode?
It makes me wonder if the electrode has hit or touched a service pipe!

 

[DefyG]

Could be DNO problem;
Got called to investigate same problem, no obvious faults within premises.
Later that night my client was witness to a 'wonderful firework display' as they called it when a pole transformer exploded and caught alight.
Tripping fault disappeared after transformer replaced! and been ok since (approx 7years ago).

 

[littlespark]

Trying the basics, here… but have you checked any appliances still plugged in?

Number of times it’s been: “yes, everything’s unplugged…” but either it’s just turned off at the wall, or there’s an old freezer in the garage

 

[Madhatter2]

Bit of an update, meeting tomorrow with customer and DNO...let’s see what the outcome is. Going up a bit early to do some more testing .......

 

[Deleted account]

Had exactly the same issue. pulled my hair out trying to find it.

it was a loose connection in the supply intake. Call DNO.

 

[diditrain]

What was your Earth leakage values like?

 

[Madhatter2]

So DNO attended today, confirmed supply issue, could be possibly a dodgy joint on the overheads, or an issue with sewage pumping station further down the lane on the same phase.