User:LMischler/Images-2016-chapter-F

DB422220_EN - F1

AC-1 zone: Imperceptible
AC-2 zone: Perceptible
AC-3 zone: Reversible effects: muscular contraction
AC-4 zone: Possibility of irreversible effects
AC-4-1 zone: Up to 5% probability of heart fibrillation
AC-4-2 zone: Up to 50% probability of heart fibrillation
AC-4-3 zone: More than 50% probability of heart fibrillation
A curve: Threshold of perception of current
B curve: Threshold of muscular reactions
C₁ curve: Threshold of 0% probability of ventricular fibrillation
C₂ curve: Threshold of 5% probability of ventricular fibrillation
C₃ curve: Threshold of 50% probability of ventricular fibrillation

Fig. F1 – Zones time/current of effects of AC current on human body when passing from left hand to feet

DB422221_EN - F2

Fig. F2 – Direct contact

DB422222_EN - F3

Fig. F3 – Indirect contact

DB422223 - F4

Fig. F4 – Inherent protection against direct contact by insulation of a 3-phase cable with outer sheath

PB116740 - F5

Fig. F5 – Example of isolation by envelope

PB116741 - F6

Fig. F6 – High sensitivity RCD

DB422224_EN - F7

Fig. F7 – Illustration of the dangerous touch voltage Uc

DB422225_EN - F9

Fig. F9 – Automatic disconnection of supply for TT system

DB422226_EN - F12

Fig. F12 – Automatic disconnection in TN system

DB422227_EN - F14

Fig. F14 – Disconnection by circuit breaker for a TN system

DB422228_EN - F15

Fig. F15 – Disconnection by fuses for a TN system

PB116742 - F16

Fig. F16 – Phases to earth insulation monitoring device obligatory in IT system

DB422229_EN - F17

Fig. F17 – Fault current path for a first fault in IT system

DB422230_EN - F18

Fig. F18 – Circuit breaker tripping on double fault situation when exposed-conductive-parts are connected to a common protective conductor

DB422231_EN - F20

Fig. F20 – Application of RCDs when exposed-conductive-parts are earthed individually or by group on IT system

DB422232 - F21

Fig. F21 – Low-voltage supplies from a safety isolating transformer

DB422233 - F22

Fig. F22 – Safety supply from a class II separation transformer

DB422234_EN - F23

Fig. F23 – Principle of class II insulation level

DB422235_EN - F24

Fig. F24 – Protection by out-of arm’s reach arrangements and the interposition of non-conducting obstacles

DB422236_EN - F25

Fig. F25 – Equipotential bonding of all exposed-conductive-parts simultaneously accessible

DB422237_EN - F26

Some tests have shown that a very low leakage current (a few mA) can evolve and, from 300 mA, induce a fire in humid and dusty environment.

Fig. F26 – Origin of fires in buildings

DB422239_EN - F29

Fig. F29 – Distribution circuits

DB422240_EN - F30

Fig. F30 – Separate earth electrode

DB422241 - F31

Fig. F31 – Circuit supplying socket-outlets

DB422242_EN - F32

Fig. F32 – Fire-risk location

DB422243 - F33

Fig. F33 – Unearthed exposed conductive parts (A)

DB422244_EN - F34

Fig. F34 – Total discrimination at 2 levels

DB422245_EN - F35

Fig. F35 – Total discrimination at 2 levels

DB422246_EN - F36

Fig. F36 – Total discrimination at 3 or 4 levels

DB422247_EN - F37

Fig. F37 – Typical 3-level installation, showing the protection of distribution circuits in a TT-earthed system. One motor is provided with specific protection

DB422248_EN - F38

Notes:
- The TN scheme requires that the LV neutral of the MV/LV transformer, the exposed conductive parts of the substation and of the installation, and the extraneous conductive parts in the substation and installation, all be earthed to a common earthing system.
- For a substation in which the metering is at low-voltage, a means of isolation is required at the origin of the LV installation, and the isolation must be clearly visible.
- A PEN conductor must never be interrupted under any circumstances.
Control and protective switchgear for the several TN arrangements will be:
- 3-pole when the circuit includes a PEN conductor,
- Preferably 4-pole (3 phases + neutral) when the circuit includes a neutral with a separate PE conductor.

Fig. F38 – Implementation of the TN system of earthing