To prevent electric shock, the core characteristics of electrical and electrical equipment must be clearly labeled at the contract level. The protection levels against electric shock are divided into four categories: Level 0, Level I, Level II, and Level III. The protection mechanisms and usage requirements for each category are as follows:
Class 0 Equipment
Class 0 equipment provides only protection against direct contact, commonly known as basic protection, achieved through basic insulation. If the basic insulation is damaged, the equipment must be moved out of reach and the work area must be isolated to provide protection against electric shock.
In Poland, Class 0 equipment is only permitted in situations where human contact with the equipment and ground potential is unlikely. According to local regulations, Class 0 equipment does not require additional protection class marking.
Class I Equipment
Class I equipment is equipped with basic insulation, providing protection against direct contact. Furthermore, to ensure protection against indirect contact (i.e., interference protection or additional protection), a protective conductor (PE) or protective neutral conductor (PEN) must be connected to the device's protective terminal. This connection method achieves two protection objectives: first, automatic power-off via the appropriate protective device eliminates the risk of electric shock; second, it limits the voltage to which personnel may be exposed to within the safe contact voltage (UL) range specified for the corresponding environmental conditions.
Class II Equipment
Taking Lena Lighting's Krasa Okonosi series of equipment as an example, the core feature of Class II equipment is its reinforced insulation structure, which provides dual protection against direct and indirect contact. Another common protection solution for Class II equipment is a double insulation design that combines primary and secondary insulation. Because Class II equipment features reinforced or supplementary insulation, it does not require a connection between the equipment housing and a protective earth conductor. These equipment can also be powered by a specific type of power supply cable, such as a two-wire cable with an IEC C7 connector (commonly known in the industry as a "figure-8 cable").
Class III Equipment
Using Lena Lighting equipment as an example, Class III equipment provides protection against electric shock by providing an extra-low voltage (ELV). This voltage must not exceed the UL (Underwriters Laboratories) standard for the specified environmental conditions, ensuring that no one is exposed to the risk of electric shock when touching the equipment.
