Measures of protection against direct contact
From Electrical Installation Guide
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IEC and national standards frequently distinguish two protections:
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Protection by the insulation of live parts
This protection consists of an insulation which complies with the relevant standards (see Fig. F4). Paints, lacquers and varnishes do not provide an adequate protection.
Fig. F4: Inherent protection against direct contact by insulation of a 3-phase cable with outer sheath
Protection by means of barriers or enclosures
This measure is in widespread use, since many components and materials are installed in cabinets, assemblies, control panels and distribution boards (see Fig. F5).
Fig. F5: Example of isolation by envelope
To be considered as providing effective protection against direct contact hazards, these equipment must possess a degree of protection equal to at least IP 2X or IPXXB (see chapter E sub-clause 3.4).
Moreover, an opening in an enclosure (door, front panel, drawer, etc.) must only be removable, open or withdrawn:
- By means of a key or tool provided for this purpose, or
- After complete isolation of the live parts in the enclosure, or
- With the automatic interposition of another screen removable only with a key or a tool. The metal enclosure and all metal removable screen must be bonded to the protective earthing conductor of the installation.
Partial measures of protection
- Protection by means of obstacles, or by placing out of arm’s reach
This protection is reserved only to locations to which skilled or instructed persons only have access. The erection of this protective measure is detailed in IEC 60364-4-41.
Particular measures of protection
- Protection by use of extra-low voltage SELV (Safety Extra-Low Voltage) or by limitation of the energy of discharge.
These measures are used only in low-power circuits, and in particular circumstances.
