9.5 Lightning and surge protection for cable networks and
antennas for TV, sound signals and interactive services
IEC 60728-11: 2005 complies with the state of the
art and offers easy, standardised and effective protective mechanisms against the effects of lightning
strikes into antennas.
Antennas installed according to this standard do
not increase the probability of lightnings to strike
the object under consideration. Nor is an antenna
system installed according to this standard a substitute for a lightning protection system of a building or structure. This standard deals with the safety requirements for stationary systems and devices
and is, if applicable, also valid for mobile and temporary systems (e.g. campers, recreational vehicles). The range of validity comprises cable TV networks (CATV networks) and satellite community
antenna television systems as well as individual
receiving networks.
Outside antennas which are installed at a level of
more than 2 m below the roofing or the roof-edge
and at distance of less than 1.5 m from the building (Figure 9.5.1) as well as antenna systems inside
a building are excepted from the following measures. However, at least the connection of the coaxial cable shields to an equipotential bonding conductor is urgently recommended. All interconnect-
ed, conductive and touchable components of the
installation should be integrated into the equipotential bonding as well.
Antennas must not be installed on buildings with
easily inflammable roofing (e.g. thatch or similar
materials). Antenna cables and earthing conductors must not lead through those sections of rooms
where easily inflammable materials like hay, straw
or alike are stored, or in which there is a potential
risk of explosive atmosphere to arise.
An equipotential bonding conductor has to be
mechanically solid with a copper cross section of
minimum 4 mm2. The shields of the coaxial cables
going in or out of the building have to be connected with an equipotential bonding conductor and
by the shortest route with a common equipotential bonding bar.
An earthing conductor being capable of carrying
lightning current can be a single solid wire having
a minimum cross section of 16 mm2 of insulated or
bare copper, or of insulated 25 mm2 aluminium or
of 50 mm2 aluminium wrought alloy (not to be
directly installed on or in plaster nor on or in concrete), or of steel 50 mm2, preferably for external
installation.
Natural components which can be used, are for
example,
equipotential bonding conductor
4 mm2 Cu
⇒ the metal frame of the building or structure,
⇒ the interconnected reinforcement steel of the
building or structure,
⇒ facades, railings and substructures of metal
facades,
provided that
min. 2 m
⇒ their dimensions meet the requirements of
down-conductor systems and their thickness is
not less than 0.5 mm,
⇒ their electrical conductivity in vertical direction is ensured (these permanent connections
have to be carried out by brazing, welding,
pressing, screwing or riveting), or that the
distance between metal structures does
not exceed 1 mm and the overlapping of
two structural elements is at least 100 cm2.
max. 1.5 m
Fig. 9.5.1 Horizontal and vertical distances of antenna arrangements requiring no earthing connection
250 LIGHTNING PROTECTION GUIDE
IEC 62305-3 does no longer stipulate this possibility of overlapping sheet metal, except the
substructure is continuously conductive in vertical direction. If not, the overlapping sheet
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0.5 m
1m
α > 60°
foundation earth electrode
α
2.5
m
flat shaped earth electrode
2.5 m
.5 m
2
1m
earth rod
earthing connection
1m
1.5 m
building foundation
3m
1.5 m
earth rod
steel skeleton, reinforced concrete buildings
metals have to be safely interconnected according to the requirements of IEC 62305-3.
Attention: Forming of loops has to be avoided.
The earth-termination system has to be designed
according to one of the following manners (Figure
9.5.2):
⇒ Connection with the external lightning protection system of the building or structure.
⇒ Connection with the earth-termination system
of the building or structure.
⇒ Connection with at least two horizontal earth
electrodes having a minimum length of 2.5 m,
being installed in an angle > 60 °, at least 0.5 m
deep and not closer than 1 m to the foundation, or connected with one vertical or slanted
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Fig. 9.5.2 Examples of permitted earth
electrodes
earth electrode not shorter than 2.5 m or two
vertical earth electrodes not shorter than
1.5 m, installed at a distance of 3 m from each
other and not closer than 1 m to the foundation.
Minimum cross section of each earth electrode to
be 50 mm2 copper or 80 mm2 steel.
Natural components such as interconnected reinforcement of concrete or other suitable underground metal constructions embedded into the
foundation of the building the dimensions of
which complying with the above limit values, can
be used as well.
Other earth-termination system according to
IEC 62305-3 are also permitted. If a supplementary
earth electrode is installed adjacent to the earth-
LIGHTNING PROTECTION GUIDE 251
equipotential
bonding conductor
4 mm2 Cu
earthing conductor
16 mm2 Cu
equipotential bonding conductor
protective
angle
DEHNiso Distance Holder
e.g. with pipe clamp
Part No. 106 225
highly insulating
distance holder
equipotential
bonding bar
equipotential
bonding bar
multiswitch
without mains
connection
earth
connection
EBB
Fig. 9.5.3 Earthing and equipotential bonding of antennas on
buildings without external lightning protection system
equipotential bonding
Potentialausgleichsleiter
conductor
protective angle
4 mm2 Cu
Air-termination rod, e.g. 1500 mm
Part No. 104 150
Concrete base, e.g. 17 kg
Part No. 102 010
Fig. 9.5.5 Antenna with air-termination rod and highly insulating
distance holder on pitched roofs with external lightning
protection system
connection of isolated airtermination system to external lightning protection system
equipotential
bonding conductor
s
4 mm2 Cu
surge arrester
equipotential
bonding bar
EB terminal
1
Fig. 9.5.4 Antenna with air-termination rod on a flat roof of
buildings with external lightning protection system
multiswitch
metal
DIN rail
2
1
termination system of the building, the earth electrodes have to be interconnected.
In case of buildings without lightning protection
system (LPS), the mast with an earthing conductor
has to be connected by the shortest route with the
earth electrode. The earthing conductor has to be
installed straightly and vertically. The coaxial cable
shields have to be connected with the mast by
equipotential bonding conductors (Figure 9.5.3).
In case of buildings with lightning protection
system (LPS), the antennas preferably shall be
installed within the protective range of an air-termination system, which means in the range of
252 LIGHTNING PROTECTION GUIDE
earth
connection
1
DEHNgate DGA FF TV 2 DEHNflex DFL M 255
Part No. 909 703
Part No. 924 396
EBB
Fig. 9.5.6 Surge protective devices downstream the equipotential
bonding bar for the coaxial cable shields in case of antenna systems with external lightning protection system and
isolated air-termination system
existing protective zones or by isolated air-termination systems. Only if this is not possible, a direct
connection with the external lightning protection
system shall be implemented. In this case the aris-
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equipotential
bonding conductor
4 mm2 Cu
earthing conductor 16
mm2
Cu
equipotential
bonding conductor
4 mm2 Cu
earthing conductor
16 mm2 Cu
combined lightning current
and surge arrester
surge arrester
surge arrester
equipotential
bonding bar
equipotential
bonding bar
EB terminal
1
EB terminal
1
multiswitch
3
multiswitch
metal
DIN rail
2
1
EBB
1 DEHNgate DGA FF TV 2 DEHNflex DFL M 255
Part No. 909 703
Part No. 924 396
earth
connection
2
DEHNgate DGA GFF TV
Part No. 909 705
2 DEHNgate DGA FF TV
Part No. 909 703
3 DEHNflex DFL M 255
Part No. 924 396
metal
DIN rail
1
EBB
earth
connection
Fig. 9.5.7 Surge protective devices downstream the equipotential
bonding bar for the coaxial cable shields in case of antenna systems without external lightning protection system
and with isolated air-termination system
Fig. 9.5.8 Combined lightning current and surge arresters downstream the equipotential bonding bar for the coaxial cable
shields in case of antenna systems without external lightning protection system
ing partial lightning currents via the coaxial conductors have to be taken into account individually.
Lightning equipotential bonding has to be performed for the conductors going into the building.
the protective zone of the protective angle
(according to the applicable class of LPS) (Figure 9.5.5). Also here the antenna arrangement
is no longer in lightning protection zone
LPZ 0A (risk of direct lightning currents), but in
lightning protection zone LPZ 0B (risk of indirect impulse currents and of the unattenuated
electromagnetic field of lightning).
If an antenna is protected by isolated air-termination systems it means
⇒ that in the area of flat roofs an air-termination
rod will be installed with the required separation distance s, putting the whole antenna
arrangement (mast and antennas) in the protective zone of the protective angle (Figure
9.5.4). Now the antenna arrangement is no
longer in lightning protection zone LPZ 0A (risk
of direct lightning currents) but lightning protection zone LPZ 0B (risk of indirect impulse
currents and of the unattenuated electromagnetic field of lightning.
⇒ that in the area of pitched roofs an air-termination rod will be installed with the required
separation distance s using highly insulating
distance holders (DEHNiso distance holders) to
fix it at the antenna mast, putting the whole
antenna arrangement (mast and antenna) into
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Protection against surges, irrespective of an
installed isolated air-termination system, has to be
provided for the coaxial cable shields by surge protective devices, to be installed downstream the
equipotential bonding bar (Figure 9.5.6). These
surge protective devices to be used both as single
devices and for rail mounting protect the downstream devices against inductive and / or capacitive
inputs of waveform 8/20 μs, arising from cloud /
cloud flashes, distant strikes or direct strikes into
the isolated air-termination system.
Surge protective devices Type 3 have to be provided for any electrical equipment with 230/50 Hz
downstream the equipotential bonding bar, which
LIGHTNING PROTECTION GUIDE 253
equipotential
bonding conductor
4 mm2 Cu
...
combined lightning current
and surge arrester
surge arrester
2
amplifier
3
junction box
terminal
block
1 DEHNgate DGA GFF TV
Part No. 909 705
2 DEHNgate DGA FF TV
Part No. 909 703
1
3 DEHNflex DFL M 255
Part No. 924 396
equiptential
bonding bar
Fig. 9.5.9 Combined lightning current and surge arresters downstream the equipotential bonding bar for the coaxial cable shields in case of
underground cable networks
is installed for the coaxial cable shields. Care has to
be taken that the lightning equipotential bonding
is carried out for all systems leading into the building.
A lightning protection system not being installed,
the following is recommended:
⇒ An air-termination rod mounted with insulated distance holders prevents from a direct
strike to the antenna. For this the air-termination rod has to be connected with the earth
electrode by a separately installed earthing
conductor (Figure 9.5.7) to be guided preferably on the outside of the building and to be
connected with the earth electrode at ground
level. Antenna mast and equipotential bond-
254 LIGHTNING PROTECTION GUIDE
ing bar have to be connected with the earth
electrode via an equipotential bonding conductor.
⇒ If the antenna mast is earthed directly, combined lightning current and surge arresters
have to be provided (Figure 9.5.8), because
partial lightning currents, which the surge
arresters are not able to control, will be conducted in this case through the coaxial cables.
The antenna mast has to be connected with
the earth electrode by an earthing conductor.
Underground utility lines of systems require combined lightning current and surge arresters being
able to carry lightning currents. They also have to
be mounted near the point of entrance into the
building (Figure 9.5.9).
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