- protection of people against defeat by electric current at a casual touch to the open carrying-out parts of electroinstallations;
- protection of EO at damage of isolation of conductors and malfunctions of EO;
- prevention of the ignitions and the fires arising owing to course of the currents of leak and developing from them short circuits, short circuits on the case and short circuits on the earth;
- automatic shutdown of a site of an electric network at an overload and current of short circuit.
Guards are equipped with two sockets with the grounding contacts everyone and have two instrument plugs for connection of cases of stationary electric equipment to a contour of protective grounding by means of separate protective conductors. Guards are executed in the form of wall devices.