Faults that aren't there?

[Bob Geldoff1234]

Over the past couple of years i have been called to houses where the rcd has periodically tripped.I have carried out all insulation resistance tests and have been greater than 20m ohms across all conductors.I have then tested the rcd tripping times and ramp tests.
Everything is showing clear and working.I then might have been called back to the same job a couple of times with sometimes months in between tripping.I have asked the usual questions about if they had plugged anything in recently that they don't normally use and that usually draws a blank.
Eventually,on one such job,the customer said that when he reached down to switch the tv off at the socket the rcd had tripped.
I removed the socket and remade off the connections(no sleeving,grommets etc) and put a new socket front on and checked the plug tops.(I still couldn't really see any definite problem that could have caused it)
This has now finally cured the tripping rcd and they have had no problems since.
My question is how do other electricians try and trace such a fault when technically when you test there are no faults present?
My insulation resistance tester inserts a small current at 500v when testing and quite often this is enough to jump across the faulty item and show up on the meter.
Are there any meters on the market that might inject more current so that in these hard to find faults it might show up better?
In other words how do you trace a fault that isn't there?
Most of the faults i get called to show as a poor reading on the meter and you can set about fault finding,knowing that when you find it,the fault will be cleared.
Sorry for the long post but just interested what other do.
Also any stories of hard to find faults and what you did to find them would be most appreciated.

 

[NDG Elecs]

Finding intermittent faults can be tricky indeed. Sometimes it's a real fluke how you do find it. A had a mega fault once, I was flummoxed and nearly rang my mates Martin and Dale, and sometimes Robin gets a bell too! It was caused by a brown uPVC door frame that expanded after having a few hours of sun on it, just enough to crush down on a cable that shouldn't have been where it was. Took months on and off to find that one. Only found it because the customer could barely open the door on that particular visit, and clutching at straws I dug around.
8
I always try to explain that looking for intermittents can be a real needle in a haystack, and it certainly does no harm to test ccts regardless. Which is a good angle to approach it from I think. I would wager that a lot of the ccts I test have never seen a MFT before.