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Direct and indirect 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

Direct contact

Two measures of protection against direct contact hazards are often required, since, in practice, the first measure may not be infallible

A direct contact refers to a person coming into contact with a conductor which is live in normal circumstances (see Fig. F2). IEC 61140 standard has renamed “protection against direct contact” with the term “basic protection”. The former name is at least kept for information.


FigF02.jpg

Fig. F2: Direct contact


Indirect contact

Standards and regulations distinguish two kinds of dangerous contact,

  • Direct contact
  • Indirect contact

 and corresponding protective measures


An indirect contact refers to a person coming into contact with an exposed-conductive-part which is not normally alive, but has become alive accidentally (due to insulation failure or some other cause).
The fault current raise the exposed-conductive-part to a voltage liable to be hazardous which could be at the origin of a touch current through a person coming into contact with this exposed-conductive-part (see Fig. F3).IEC 61140 standard has renamed “protection against indirect contact” with the term “fault protection”. The former name is at least kept for information.


FigF03.jpg

Fig F3: Indirect contact