recommendations posted here have historically included:
• Having a licensed electrician ensure that the power wires at your outlets are wired correctly. That would be a very Prudent thing to do, as well as inspecting the charger and wiring for any damage.
• A simple work-around is to purchase the Apple Power Adapter AC 'Extension Cord' with local wall plug for your area. It serves to "clean up" the generated low voltage power by providing an Earth/Ground reference for the electronics of the power adapter. (This ground is not required to be carried into the device, because this is not a line-power level appliance.)
it works like this US example:

Earth/Ground is connected from the 'extension cord' by the chromed lug in the power adapter body.
