Protection classes

The protection classes in electrical engineering are defined for all electrical equipment in DIN EN 61140 VDE 0140-0. It is divided into four different protection classes (protection class 0, I, II, III). The respective protection classes differ in the type of protection. Symbols are provided for each protection class to identify the equipment with the respective protection classes. The symbols for the protection classes are also defined in DIN EN 61140 VDE 0140-0. The protection classes describe the different types of protection of equipment and its measures against dangerous body currents.

Protection class 0 no special protection against electric shock in addition to the basic insulation. There is no connection to a protective conductor system. Protection must be ensured by the environment of the equipment. Devices of this protection class and type of protection are not approved in Germany and Austria.

Protection class I (protection by protective conductor) Device with protective conductor connection and basic insulation. In protection class I, electrical appliances have a plug connection with the protective conductor contact as a protective measure. The protective conductor connection for protection class I is set so that it is the first to be connected to the plug and the last to be disconnected in the event of danger in order to comply with the standard against dangerous body currents. The connecting cable into the appliance must be strain-relieved so that the protective conductor is the last to be mechanically stressed and thus torn off when the cable is torn off. If a current-carrying conductor touches the housing connected to the protective conductor in the event of danger, a short circuit occurs which triggers the fuse or a residual current circuit breaker and disconnects the circuit from the power supply.

Protection class II (protection through protective insulation) Device without protective conductor connection with double or reinforced insulation. Electrical systems with protection class II have double or reinforced insulation between the mains circuit and the output circuit and do not have a protective conductor connection. In electrical engineering, this type of protection is referred to as protective insulation. Conductive parts, such as conductive surfaces of electrical appliances, are protected from contact with live parts by the reinforced insulation. Devices or electrical installations of protection class II do not have earthing contact plugs. Protection class II uses either Euro plugs or contour plugs for electrical installations.

Protection class III (protection by safety extra-low voltage) Device in which the protection against electric shock is based on the supply with SELV and in which no voltages higher than the SELV are generated. Protection class III is characterized by the safety extra-low voltage and requires double insulation in mains operation, similar to protection class 2.