Sitting at my PC this evening, suddenly electricity goes off. <deleted> PEA, right?

I step out of my office and see the kitchen still has lights on, so time to check the consumer unit.

I have 3 circuits in the CU and the RCCB from 1 circuit has tripped. Close it again and after 5 seconds trips again, second time same story.

I open all MCB's on the circuit, but RCCB still trips after about 5 seconds.

Then I remove the cover from the CU to see if there is anything visible, but all looks normal.

In the meantime probably 5 minutes have passed, so I close the RCCB again and now it doesn't trip anymore, so I start closing the MCB's one by one, but nothing happens.

We're now about 20 minutes, all MCB's closed and electricity stays on. This is the first time ever this RCCB trips.

Any ideas?

Found the culprit already.

It are the lights on the perimeter wall, which are disconnected for years already, bur somehow I must have pressed the switch in the dark.

Has the switch gone bad from environment or critters ?

 

19 minutes ago, degrub said:

Has the switch gone bad from environment or critters ?

 

 

Nope I removed the lights on the perimeter wall, but never disconnected the switch. And there are 9 switches next to each other, with the switch in question somewhere in the middle.
So I must have switched it on, and something in the perimeter wall make the RCCB trip