1 Lightning discharges
(LEMP: Lightning Electro Magnetic Impulse)
The international lightning protection standard IEC
62305 describes how direct lightning strikes to
200 are safely arrested. The current coupled in-
to the earthing system and, due the voltage drop at
the earthing resistor, half the lightning current is
coupled into the internal installation. According IEC
62305, lightning strikes are simu-
lated with lightning surge currents
of 200 (10/350 μs). Even from
several hundred metres away, lightning currents can
also cause impermissible surge voltages conductor
loops, through either capacitive, inductive galvanic
coupling. 200 (IEC 62305)
Earthing system 50% 100 (50%)
Electrical installation 50% 100 (50%)
Data cable (5%)
Typical distribution lightning current
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Chapter The internal lightning protection system
. For further
information types damage (S1–S4) see Chapter
1.3 (starts 15). This then the potential
difference between the local earth (equipotential bond-
ing) and the active cables, which are earthed some
distance away.
3.
The highest surges are caused by
lightning strikes. The partial light-
ning current then divides itself among the power lines
entering the building (number cores power line
entering building), while around enters data
cables.3.2. Switching operations involving in-
ductive loads create dangerous surge voltages the
medium and low-voltage power networks.
The voltage drop the earthing resistor calculated
from the product the partial lightning current (i) and
the earthing resistance (R). Large surge voltages are coupled over ra-
dius km.
Lightning strike 100% Iimp
= max.2 Surge protection system for en-
ergy systems
Very large surge voltages are caused mainly light-
ning strikes close energy systems
