RCCB tripping randomly

[blueribbon]

At my home there's a RCCB that keeps randomly tripping, ranging from once every month, to two times in a week. We couldn't identify any pattern. The only thing that seems to be related, is that it seems to happen more frequently after setting up the microwave clock, but it's not an immediate effect (some days may go by). Two electricians have been here (not sure about their qualification), but they couldn't find the issue, they said that the only thing that they could do is measure the current/ground of each electrical outlet, but that would take hours and even then they weren't sure they could find the issue.
Is there any reasonable approach to solve this?

 

[Calebp43]

So if this was my house I would use my earth clamp to check earth leakage on the circuits being supplied by the RCCB. You're most likely gonna find that one of your ring mains with computers and tv's etc is gonna have a lot of earth leakage. If your kitchen which has a lot of things for example fridges and microwaves that naturally produce earth leakage is on the same RCCB as your ring main which also has a lot of things with earth leakage is supplied by that RCCB then that could be your problem.
Does your house have two RCCB's or one? And if one, is the one that is tripping supplying the kitchen ring and other rings in the house?

 

[Sparkgap]

Is it a particular circuit? Does it still happen if you leave the microwave unplugged? Could it be combined earth leakage from plugged in electronic equipment? There's another post where the OP had a similar fault which turned out to be neutral wire snagged in a socket.

 

[blueribbon]

earth clamp to check earth leakage on the circuits being supplied by the RCCB

I'm pretty sure that both electricians that came here did that, but didn't find anything out of the ordinary.

Does your house have two RCCB's or one? And if one, is the one that is tripping supplying the kitchen ring and other rings in the house?

It had only one. Since this happened we installed another one just for the fridge (and related outlets), so that at least it could be kept on when the other RCCB tripped.

 

[blueribbon]

Is it a particular circuit? Does it still happen if you leave the microwave unplugged? Could it be combined earth leakage from plugged in electronic equipment? There's another post where the OP had a similar fault which turned out to be neutral wire snagged in a socket.

Not sure if it happens if I leave the microwave unplugged, because it is quite hard to unplug it (it's fitted) but when I suspected that it could have something to do with it the electrician that came here checked the outlet, but it seemed ok.

It's really strange, sometimes weeks go by without any trip.

 

[Calebp43]

Unfortunately I don't think there is any easy approach. If they checked circuits with an earth clamp and also tested the circuits with either Insulation resistance tests or continuity testing to see that the cables are all okay and they all came up fine then yeah could be any of your electrical items.
Intermittent faults are the worst!