Reviewed by Dominic Hopkins
The practical answer
Possible causes include a faulty appliance, moisture, damaged wiring, an external circuit problem or combined leakage from several items. Unplugging recently connected portable appliances may identify an obvious cause, but repeatedly resetting a device that will not hold is not a repair. Burning smells, water or visible damage mean the circuit should remain isolated pending professional attention.
This guidance is general and cannot replace inspection or testing of the actual installation. If there are signs of danger, isolate the affected circuit where safe and seek professional help.