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soil and the feet. However, these resistances are not to be rings and the step voltage resulting from the reaction of the ob-
mistaken for other resistances such as shoe soles. According ject to this step voltage is calculated (Figure 5.7.2.5).
to Neuhaus, these earth resistances act in series with the in- Figure 5.7.2.6 shows the arising step voltages U S,with with re-
ternal resistance of the human body, form a voltage divider action of the human body, the step voltages U S,without without
and reduce the step / body voltage actually applied to a person reaction of the human body as well as the quotient obtained
compared to the pure step voltage on the soil. from both values for soil models without ionising effect and an
To be able to verify this reaction also in the simulation, a highly electrical conductivity of σ = 0.001 S/m.
simplified object in the form of an arc was developed, the two Table 5.7.2.2 compares the results of further simulations
bases of which correspond to the area of a foot assumed by with the factors analytically assessed by Neuhaus.
Neuhaus (D = 0.15 m). The electrical conductivity is selected so Figure 5.7.2.6 shows that the factor U S,without / U S,with is ap-
that the resistance of the arc is 1 kΩ. Extensive research has proximately constant over the entire calculation period at a
shown that this value is the most critical case to be assumed given soil conductivity. If the soil conductivity varies, the fac-
with regard to the resulting electric shock. The arc is positioned tor U S,without / U S,with also changes (Table 5.7.2.2). The factors
on the soil surface above an earth-termination system with four determined in the simulation are in good agreement with the
factors analytically assessed by Neuhaus. For these reasons,
the factors described before can be used to directly convert the
simulation results of step voltages into the arising step / body
U S in kV U S, without / U S, with voltages without performing time-consuming individual simu-
80 16
lations with a replacement body for each earth electrode
70 U S, without 14 configuration to be simulated. Figure 5.7.2.7 shows the
U S, with
60 U S, without / U S, with 12
50 10 U S, without / Factor acc.
ρ in Ωm σ in S/m
40 8 U S, with to Neuhaus
30 6 100 0.01 1.64 1.66
20 4 200 0.005 2.3 2.3
10 2 500 0,002 4.1 4.3
0 0 1000 0.001 7.2 7.6
0 2 4 6 8 10 12 14 16 18 20
r in m 0.001 ... 0.01
– 7 –
(non-linear)
Figure 5.7.2.6 Reaction of a human body to the arising step voltage Table 5.7.2.2 Simulation results with and without consideration of
the reaction of the human body to the step voltage

U S in kV U S in kV
120 1 ring 50 1 ring
2 rings 35 2 rings
100 3 rings 40 3 rings
4 rings 4 rings
Limit value 35 Limit value
80
30
60 25
20
40 15
10
20
5
0 0
0 2 4 6 8 10 12 14 16 18 20 0 2 4 6 8 10 12 14 16 18 20
r in m r in m
Figure 5.7.2.7 Comparison of step voltages in the reference model of several ring earth electrodes considering the correction factor for the
reaction of a human body: Soil ionisation is not considered (left), soil ionisation is considered (right)

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