Is running over your extension cable with an electric lawn mower dangerous?
Minimal protection when using a corded electric lawnmower is to power it from a GFCI protected outlet/circuit. If your outdoor outlets do not have GFCI built in, or if you are running your extension from a regular indoor outlet, you can purchase standalone GFCI devices to go between the extension cord and the power source.




To answer your question directly - the lawnmower itself should be double-insulated, meaning the handle bar should be electrically insulated from the mower blade and the motor components. But if you run over the cord you still have the problem of severed cable ends supplying full mains voltage to whatever they touch, which is why using a GFCI is so important.