9.17 Surge protection for transmitting / receiving systems
(mobile radio stations)
According to the requirements of IEC 60728-11
(EN 60728-11), DIN VDE 0855-300 (Germany) radio
frequency transmitting / receiving systems are
designed in such a way that induced lightning currents are safely discharged to the earth electrode
via the earth conductor. This means that transmitting / receiving systems (Radio Base Stations (RBS))
must be protected against surges due to lightning
currents. The radio base station (RBS) comprises
the power supply unit (PSU), the system technology in the cabinet or service room as well as the
remote radio heads (RRH) and the sector antennas
(Figure 9.17.1).
Power supply 230V/400 V AC
Power supply of the RBS has to be separate and
independent from the power supply unit of the
building. Supplying the mobile radio station via
the power sub-distribution board / floor distribution board inside the building shall be avoided.
The energy meter shall be installed near the service entrance box. According to the standard each
sub-distribution board shall be equipped with
surge protective devices (Type 1 and 2). A combined lightning current and surge arrester (Type 1
and 2) shall be additionally installed in the downstream area of the meter, i.e. downstream of the
meter fuse. For reasons of energy coordination
surge protective devices of the same producer shall
be installed at both installation sites. Comprehensive laboratory tests at DEHN + SÖHNE on power
supply units of different producers prove the coordination of the DEHNvap CSP 3P 100 FM with integrated PSU input protections.
Depending on the system technology such as
indoor or outdoor base stations, different types of
the a.c. sub-distribution board are used. Either
compact All In One power supplies (AIO) with integrated SPDs or usual separate wall-mounted distribution boards supplying all components installed
in the service room, irrespective of the system configuration.
For the protection of a base station power supply
unit (PSU) combined spark-gap-based lightning
current and surge arresters of type DEHNvap CSP
3P 100 FM are used. This Type 1 arrester (CSP = Cell
Site Protection) have been particularly designed to
protect power supply units in radio frequency
transmitting / receiving systems. Via the protective
device in the sub-distribution board there is a
selected input of lightning current and a selected
output in the service entrance area. Figure 9.17.2
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Fig. 9.17.1
T-Mobile (Brandenburg), LTE (Long Term Evolution) configuration; Source: obs/Deutsche Telekom AG
shows the basic circuit diagram with a DEHNvap
CSP 3P 100 FM combined arrester.
In order to ensure consistent surge protection at
all sites of an operator and to be independent in
designing with regard to the different system configurations, the DEHNvap CSP 3P 100 FM, a protective device with "3+1“ circuit, provides a universal
solution for TN-C, TN-S and TT systems (Figure
9.17.3). A quality characteristic of special importance for using combined lightning current and
surge arresters, is a sufficient follow current extinguishing capability and follow current limitation /
selectivity. Thus, false tripping of the system fuses
and the disconnection from power supply is avoided. This quality characteristic of the combined
lightning current and surge arresters called “selectivity” is necessary. If applied in transmitting /
receiving systems, a selectivity according to Table
9.17.1 is required.
LIGHTNING PROTECTION GUIDE 295
Remote Radio Head (RRH), 48V DC, for
LTE (Long Term Evolution, 4G)
With Remote Radio Head the 3rd generation of mobile radio technology (3G,
UMTS) has been developed. The actual
system technology is still located in the
operation room or in the cabinet. Only
the RRHs with the HF module are installed
in close vicinity of the antennas. For communication between the HF heads and
system technology, the coaxial cables
have been replaced by glass fibre cables.
For the operation of the RRHs (active system technology), however, a separate 48
V d.c. voltage supply from the service
room is needed, realised by a cable of
type NYCWY 2x16/16 mm². The shielded
cable has to be earthed as required in the
standard IEC 60728-11 (EN 60728-11), DIN
VDE 0855-300 (Germany). If there is a
building lightning protection system it
has to be integrated in accordance with
IEC 62305-3 (EN 62305-3). Already
installed feeder cables may be also used
for the d.c. supply of the RRHs as well as
for communication between RRHs and
system technology by means of special
coaxial copper converters.
As shown for the system power supply
(main and sub-distribution board), there
is a selected input of lightning current
also in the d.c. box (mast) and a selected
output in the OVP box (overvoltage protection box, service room). In both d.c.
boxes (indoor and outdoor) d.c. Type 1
arresters with a low protection level are
used which especially have been developed for use at RRH. In the d.c. box at
the mast a "1+1“ circuit is implemented,
the positive pole (0V) and the cable
shield being indirectly connected via a
so-called "total spark gap" due to the
corrosion currents. Figure 9.17.4 shows
the basic circuit diagram of Remote
Radio Heads in case of spatially separated functional equipotential bonding
levels. The surge protective devices
used are shown in Table 9.17.1.
antenna
RRH
(remote radio head)
d.c. Box
(outdoor box)
socket outlet
RBS
(radio base station)
airconditioning
lighting
power
distribution
cabinet
upper floor
EBB
basement area
kWh
power
distribution
cabinet
MEB
existing earth electrode
Fig. 9.17.2
Fixed network connection
Either fixed network links via copper cable or radio
links are chosen to connect the base stations with
296 LIGHTNING PROTECTION GUIDE
EBB
roof area
Electrical circuit diagram
the primary switching technology. In case of a
fixed network connection, partial lightning currents will also flow through the telecommunica-
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Fig. 9.17.2 Protection for...
Type
Part No.
DEHNvap CSP 3P 100 FM
900 360
DEHNguard Modular DG M TT 275 FM
952 315
Remote Radio Head OVP box (indoor)
DEHNsecure Modular DSE M 160 FM
971 126
Remote Radio Head d.c. box (outdoor)
DEHNsecure Modular DSE M 2P 60 FM
971 226
LSA-Plus, series 2
DEHNrapid DRL 10 B 180 FSD
907 401
Screw terminal
(recommendation DEHN + SÖHNE)
BLITZDUCTOR XT BXT BD 180
+ base part BXT BAS
920 347
920 300
GSM, UMTS, LTE / 876 ... 960 +
GSM, UMTS, LTE / 2000 ... 6000
DEHNgate DGA L4 7 16 B or
DEHNgate DGA L4 N EB
929 048
929 059
RiFu/2400
DEHNgate DGA G N
929 044
WLAN/2400
DEHNgate DGA G BNC
929 042
TETRA/380 ... 512
DEHNgate DGA L4 7 16 S
929 047
l. v. supply
Combined arrester (Type 1 and Type 2)
for power supply units
l. v. supply of RBS
Surge protection
d.c. protection, 48 V supply of RRH
Fixed network
Transmission technology
Table 9.17.1
Surge protection for mobile radio stations
tion cable if a direct lightning strike hits the antenna system. In this case, combined SPDs also provide
sufficient protection. Surge protective devices
according to Table 9.17.1 are used.
Radio transmission technology
The radio transmission band and the connection
mechanics are the decisive factors concerning the
selection of suitable surge protective equipment
for the protection of the radio transmission technology. Sufficient discharge capability, remote supply voltages of PTP radio systems, and depending
on the application, also low passive intermodulation (PIM) have to be taken into account. Table
9.17.1 shows the DEHN + SÖHNE products for protection.
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Lightning protection, earthing, equipotential
bonding
With regard to earthing, equipotential bonding,
lightning and surge protection mainly IEC 6072811 (EN 60728-11), DIN VDE 0855-300 (Germany) as
well as IEC 62305-3 (EN 62305-3) are applicable for
design and installation of transmitting / receiving
systems. A distinction has to be made whether a
transmitting / receiving system must be installed on
a building or structure with lightning protection
system according to IEC 62305-3 (EN 62305-3) or
without lightning protection system. Then, corresponding earthing and equipotential bonding
measures have to be taken according to IEC 6072811 (EN 60728-11), DIN VDE 0855-300 (Germany) or
IEC 62305-3 (EN 62305-3). Chapter 5.2.4.2 of the
Lightning Protection Guide describes possible
lightning protection measures for mobile radio
stations.
LIGHTNING PROTECTION GUIDE 297
Fig. 9.17.3
Basic structure of a RBS with DEHNvap CSP 3P 100 FM
Fig. 9.17.4
Basic diagram of Remote Radio Heads (RRHs) in case of spatially separated functional equipotential bonding levels with d.c. box
(mast) and DEHNsecure DSE M 2P 60 FM as well as OVP box (service room) with DEHNsecure DSE M 1 60 FM
298 LIGHTNING PROTECTION GUIDE
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