i recently re wired a house and am at the comissioning stage. everything working apart from 1 lighting circuit. the original problem was that the circuit breaker and rcd protection were on and working fine. however as soon as a light was turned on the rcd would trip. this was however only when a globe was in a light. i split the circuit and found the middle light was on working fine so the problem was down the line.
so i went to a light further down and found that a neutral was loose. i re connected this. however whilst this was now not tripping the rcd, as soon as i tried the same thing with putting a globe in and turning on the circuit breaker was now tripping. and when trying to reset it was popping but staying on
i have inspected all the connections and followed the cable and there is no visible thing that would be causing this.