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Measures of protection against direct contact

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General rules of electrical installation design
Connection to the MV utility distribution network
Connection to the LV utility distribution network
MV and LV architecture selection guide
LV Distribution
Protection against electric shocks
Sizing and protection of conductors
LV switchgear: functions and selection
Overvoltage protection
Energy Efficiency in electrical distribution
Power Factor Correction
Power harmonics management
Characteristics of particular sources and loads
PhotoVoltaic (PV) installation
Residential and other special locations
ElectroMagnetic Compatibility (EMC)


Contents


IEC and national standards frequently distinguish two protections:

  • Complete (insulation, enclosures)
  • Partial or particular


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.


FigF04.jpg

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).


FigF05.jpg

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 must only be removable, open or withdrawn: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.