RCCB tripped when neutral - earth touching

[huhimafi]

Hello

When replacing a light housing, I found the RCCB was somehow tripped. I first used a pen tester to check the wires and found them normal (no voltage). I then used a multimeter to test again. Here are the results:

L-N 7.4 v
L-E 6.8 v
N-E 3 V

After the RCCB was tripped, the readings were zero. So, I think the readings were real.
Only N-E would trip the RCCB, other combinations wouldn't.

Any guess what's going on here?

 

[tom baker]

This is a forum on the NEC, most here don’t know what an RCCB is. You may get a few answers.

 

[winnie]

RCCB is residual current circuit breaker. These provide ground fault protection but ar much less sensitive than North American GFCI breakers.

They are common as main breakers in European installations.

The question is not clear.
When were the different voltage readings taken, and what was the RCCB state at these times?
What sort of meter was used?
A L-E fault should trip an RCCB, why do you think it shouldn't?

Jon