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conductive connection into the building can be replaced by an tural parts. In order to protect structures on the nacelle such
insulating joint (e.g. a GRP tube) to prevent hazardous spark- as anemometers in the event of a lightning strike, air-termi-
ing in parts of the external lightning protection system. nation rods or “air-termination cages” are installed (Figure
5.1.10.2).
In more modern churches made of reinforced concrete, the re-
inforcing steels can be used as down conductors if they have The metal tower or, in case of a prestressed concrete tower,
a permanently conductive connection. If pre-cast reinforced round wires (St/tZn, Ø 8 ...10 mm) or flat strips (St/tZn, 30 mm x
concrete parts are used, the reinforcement may be used as a 3.5 mm) embedded in the concrete are used as a down conduc-
down conductor if connection points are provided on the pre- tor. The wind turbine is earthed by means of a foundation earth
cast concrete parts to continuously connect the reinforcement. electrode in the tower base and the meshed connection to the
foundation earth electrode of the operations building or other
According to the Supplement 2 of the German DIN EN 62305-3 wind turbines. This creates an “equipotential surface” which
standard, lightning equipotential bonding / surge protection prevents potential differences in the event of a lightning strike.
of the electrical equipment (power installation, telephone and
loudspeaker system, etc.) is implemented at the entrance point
into the building and for the bell controller in the steeple and
at the control system.

5.1.10 Air-termination systems for wind
turbines receptor
Lightning protection
The continuous further development of modern wind turbines wire mesh
with tower heights of more than 100 m considerably increases
the risk of lightning strikes to a wind turbine. Moreover, the
value of wind turbines is increased as a result of the higher
generator outputs. Due to the global use of wind turbines, this
technology is increasingly used in areas with a high lightning
activity. At these heights, fire caused by lightning effects can
rarely be extinguished by means of conventional fire-fighting
equipment.
International standards follow this trend. The IEC 61400-24
(EN 61400-24) standard (Wind turbines: Lightning protection)
requires class of LPS I and therefore, wind turbines must be
designed for lightning currents of 200,000 A.
Principle of an external lightning protection system Figure 5.1.10.1 Wind turbine with integrated receptors in the rotor
for wind turbines blades
An external lightning protection system consists of air-termi-
nation systems, down conductors and an earth-termination
system and protects against mechanical destruction and fire.
Since lightning typically strikes the rotor blades of wind tur-
bines, e.g. receptors are integrated in the rotor blades to pro-
vide defined points of strike (Figure 5.1.10.1).

In order to discharge the injected lightning currents to earth
in a controlled way, the receptors in the rotor blades are con-
nected to the hub via a metal connecting cable (flat strip,
2
St/tZn, 30 mm x 3.5 mm, or copper cable, 50 mm ). Carbon
fibre brushes or spark gaps in air bridge the ball bearings in Figure 5.1.10.2 Lightning protection for the anemometers of a wind
the head of the nacelle to avoid welding of the rotating struc- turbine

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