Page 9 - DS225 Modern-buildings

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External lightning protection Coping with direct lightning strikes

Conventional and isolated lightning protection

Lightning protection is protection against fire and, above all, personal injury. Lightning
protection systems form a protective sheath around the building by intercepting direct
A A lightning strikes and discharging them to the ground.
C

External lightning protection is set out in the IEC 62305 standard and protects buildings from the effects of a direct lightning
strike. A complete lightning protection system consists of the following elements: air-termination system, down conductor
system, earth-termination system, lightning equipotential bonding or separation distances.

B The lightning current flows into the down conductors via the air-termination system and is conducted to the ground in a
controlled manner. The important thing here is that the separation distances from conductive metal parts are maintained.
Otherwise, dangerous flashover can occur which may cause sparking and start a fire. Lightning equipotential bonding reduces
the potential differences caused by the lightning current. This is achieved by connecting all isolated conductive system parts
directly by means of conductors or by means of surge protective devices (SPDs).
There are two types of external lightning protection system for a building:

Conventional lightning protection system

If the separation distances from metal and/or earthed installations is maintained con-
sistently, the air-termination and down-conductor systems – for example round wires
or air-termination rods – can be installed on the surface of the building.
Please note: Special requirements must be observed for buildings with thatched roofs!

Product examples for conventional lightning protection can be found on page 8.
If separation distances cannot be maintained due to the properties of the building,
consistent lightning equipotential bonding is required. As an alternative, an isolated
lightning protection system can be installed.
External lightning protection

A Air-termination system Product examples Part No.
Isolated lightning protection
Correctly dimensioned air-termination Self-supporting air- 105 530
systems prevent direct lightning strikes to a termination rod
building. They consist of rods, spanned wires / Roof conductor holder 253 050 In case of an isolated lightning protection system, air-termination rods, air-termination masts or masts spanned with cables
cables and intermeshed conductors and can Air-termination rod 103 220 protect the entire building against the effects of a direct lightning strike. The separation distance s between the lightning
be combined as needed. DEHNiso spacer 106 115 protection system, the building and installations as pipes, chimnies, coolers, wires and antennas etc. must be maintained.

HVI Lightning Protection
HVI Lightning Protection comprises a high-voltage-resistant insulated down conductor
B Down conductor Product examples Part No. which, in combination with the relevant supporting tubes and air-terminations rods,
A down conductor is a conductive connection DEHNalu wire 840 028 forms the isolated lightning protection system. The special feature is that the lightning
between the air-termination system and the Screw, plastic base 207 109 current carrying conductor is wrapped in semi-conductive insulating material so that
earth-termination system. It discharges the and dowel the necessary separation distance – be it from other conductive parts of the building
intercepted lightning current to the earth- Round wire 860 115 or electrical lines and pipes – can be easily maintained. Consequently, further meas-
termination system without damaging the Number plate 490 110 ures such as the additional connection of a braided shielded are not required.
building, e.g. as a result of excessive heat.
HVI Conductors also cater to the desire for a modern appearance and design. The
C Connection components (clamps) Product examples Part No. conductors can be painted to match the colour of the building or even installed
Clamps interconnect conductors or connect MV clamp 390 051 behind the façade. The system can thus be optimally adapted to the architecture of a
them to the installation. They must be subjec- UNI disconnecting clamp, 459 129 building and offers entirely new design possibilities.
ted to a lightning current test according to stainless steel
IEC 62561-1. DEHN components fully meet Saddle clamp, 365 031 Glass-fibre reinforced plastic (GRP)
this requirement and are reliably tested. aluminium
Downpipe clamp 423 019 As an alternative, air-termination and down-conductor systems made of electrically insulating material such as GRP can be
mounted on the object to be protected.

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