Additional protection is protection against electric shock in addition to basic protection and/or fault protection (source: IEC 60050-195-2021).
Note: Additional protection may be specified with the protective measure under certain conditions of external influence and in certain special locations (see the corresponding Part 7 of IEC 60364).
If the intended use implies an increased inherent risk, e.g. for areas with a low-impedance contact of persons with earth potential, technical committees shall consider the possible need to specify additional protection. Such additional protection may be provided in the installation, in the system or in the equipment.
The use of RCDs with a rated residual operating current not exceeding 30 mA, is recognized in a.c. systems as additional protection in the event of failure of the provision for basic protection and/or the provision for fault protection or carelessness by users.
An RCD with IΔn ≤ 30 mA is used in addition to:
- basic protection by basic insulation and/or
- fault protection.
The RCD for additional protection shall be suitable for isolation.
Note: In Hungary RCDs with rated operating current not exceeding 100 mA can be used as additional protection in installations situated outside.
The use of such devices is not recognized as a sole means of protection and does not obviate the need to apply one of the protective measures specified in the articles:
Note: Where installed at the origin of a final circuit or a group of final circuits, an RCD with a rated residual current not exceeding 30 mA may provide fault protection and additional protection simultaneously.
Residual current monitoring devices (RCMs) are not considered to be protective devices.
See this subclause here: What Is an Equipotential Bonding? Definition, Meaning, Requirements, Examples
Figure 1 shows the relationship between protective measures for additional protection and their respective provisions.
Figure 1 – Protective measure: additional protection (in addition to basic and/or fault protection)
