Hi, I'm new but read these forums a lot. Recently, the RCD on one side of the fuseboard went and after elimination it was the cooker circuit that caused it to trip. The oven and electric hob are connected into a terminal box after the main switch, so I disconnected both, the circuit was ok, but tripped when adding the load of either. I put a meter on the empty connector and found that there was still low resistance between two of the connectors where live and earth had been. There were some slugs about and I noticed some mush across the two connectors. I cleaned them and all is ok, so it was fried slug that caused the problem. Next step is to stop the slugs.
I used to subbie for Railtrack/Network Rail. There was an incident where the Bristol-Gloucester main line signalling all went pop. The fault was eventually traced to a 400v cable in a metal box near Wickwar. It became known as the "Wickwar Wet Weasel" incident.
We are very lucky in the UK (apart from the odd mice) we don’t have a major vermin/wildlife problems that other countries have. It’s said the 8.5% of power outages in NE USA are caused by squirrels. In other parts of the world everything from fire ants, birds, snakes and even elephants can cause an outage although you won’t find the last hiding behind your oven !
I went to an MCB tripping problem, after letting the resident take up his laminated floor, found a slug in a TV amp under the floor