Safe insulation is the central protective measure to ensure electrical safety. It ensures that the user does not touch live conductors and that no short circuit can occur between the conductors or to the housing of the equipment. Because if it did occur, a life-threatening current could flow through the user if he or she touched the housing. Obviously, the protective earth conductor should ensure that this does not happen. But in the worst case it could also be defective. And it would also only be an evasion of the effect, not of the cause.