1.4.2.
For a. The sign 95%, 50%, the curves mean that the values given
with the relevant curve are not exceeded for percentage 95%, 50% and the human
. Resistance (impedance) the human body
The safety limits currents (or the time current zones Figures 4. The relationship of
current voltage not linear because body impedance varies with the touch voltage.1 which organic
damage expected. the designer is
more useful safey requirements are specified terms voltage function time. The document
IEC 479 implemented Czech standard ČSN IEC 479 (33 2010).1 and 4.2) are
inconvenient for direct application the practical design installations. Safety limits current passing through the human body
Nowadays safety limits current are not prescribed Czech standards.
Conventional conditions this respect mean situation where the most probable accident is
hand hand hand foot.1.2.2. Equipment assigned in
relevant ČSN standard
permanent 3,5 10
3.EFFECTS CURRENT PASSING THROUGH THE HUMAN BODY
26
4.1 the dependence the total body impedance to
the touch voltage can seen. The informative limits
which, according this standard, can used for electrical equipment are shown table 4. The curve considered reasonable for the establishment the
disconnecting times function prospective touch voltage for the measure for protection by
automatic disconnection supply. placed with certain margin safety below zone in
which the risk ventricular fibrillation arises, which the main cause death electricity,
the probability which increased with the intensity the current and the duration flow.3.c. For this
purpose, certain values body impedance must taken into consideration. (15 100 Hz), the curve situated zone (Fig. the Figure 4. All equipment (except
medical equipment)
permanent 0,5 2
2.1.1. Industrial equipment
according relevant
ČSN, not possible
to fulfill limits for point 2
5
(exceptionally
permanent)
10 30
4.1 Informative safety limits current passing through the human body according to
new standards
Type equipment The longest duration
of current
(s)
Safety limits current
(mA)
for
alternating current direct current
1.
Table 4.1.
4.1 Requirements for characteristics protective devices.3
