1. Relevant ITU-T Recommendations for the Protection of Base Stations
ITU Workshop on
“Tackling climate change and Specific Absorption Rate (SAR) Measurement”
(Cotonou, Benin, 19 July 2012)
Relevant ITU-T Recommendations for the Protection of Base Stations
Ahmed ZEDDAM,
ITU-T SG5 Chair
France Telecom Orange
Cotonou, Benin, 19 July 2012

2. RECOMMENDATION ITU-T K.56
Outline
INTRODUCTION
LIGHTNING PROTECTION
RECOMMENDATION ITU-T K.56
Need of Protection
Earthing and Bonding procedures
Use of SPDs
DECOUPLING WITH POWER NETWORK
CONCLUSION
Cotonou, Benin, 19 July 2012

3. Protection of an installation may require a combination of:
Introduction
Protection of an installation may
require a combination of:
Lightning protection for the building
Protection on incoming lines
Resistibility of equipment
Earthing and bonding of installation
This presentation is about the protection of equipment within a base station
Cotonou, Benin, 19 July 2012

4. SG 5 role in equipment protection
SG 5 is unique SDO in overvoltage protection
Ensures coordination of the equipment and external protection
Considers installation practices and their effect on resistibility requirements
Cotonou, Benin, 19 July 2012

5. Resistibility and protection
Preventing equipment damage may require a combination of resistibility and protection
Resistibility is
The ability of the equipment to withstand an overvoltage or overcurrent
Protection is
The addition of primary protection to prevent damage from larger surges
Need to check that the protector operates and protects the equipment
Cotonou, Benin, 19 July 2012

6. Lightning Protection Lightning discharges can reach a
telecommunication
system by the
following
mechanisms:
Cotonou, Benin, 19 July 2012

7. Lightning Protection
Direct strikes
Cotonou, Benin, 19 July 2012

8. Lightning Protection Coupling through the earth
Cotonou, Benin, 19 July 2012

9. electromagnetic fields
Lightning Protection
Coupling through
electromagnetic fields
Cotonou, Benin, 19 July 2012

10. Lightning Protection
 If adequate protection is missing, the lightning
surges can be very dangerous to telecommunications
systems, threatening :
Terminal equipment
Station equipment
And even human beings
 In order to protect the telecommunications systems
against the effects of lightning discharges, the ITU-T
SG-5 produced Handbooks and a set of Series K
Recommendations:
Cotonou, Benin, 19 July 2012

11. Recommendation ITU-T K
Recommendation ITU-T K.56 : Protection of radio base stations against lightning discharges
Presents the techniques applied to a telecom. radio base station in order to protect it against lightning discharges
The need of protection is obtained from the methodology contained in IEC , which is used to determine the relevant lightning protection level (LPL) for the installation
The protection techniques for the external area cover the lightning protection system (LPS), bonding procedures, earthing and the installation of surge protective devices (SPDs) at the power meter station
The protection techniques for the equipment building cover the feeder and lighting cables, the electric power conductors, the telecommunication cabling and the earthing/bonding procedures applied to cable trays and equipment frames
Cotonou, Benin, 19 July 2012

12. Need of protection
The risk assessment of the RBS shall be performed according to [IEC  ] in order to determine a Lightning Protection Level (LPL) for the design of the protection procedures.
Table 1 shows some lightning flash parameters associated with each LPL.
Parameter
Unit
LPL I II
III IV
Maximum peak current kA
200
150
100
Maximum current rate of rise
kA/s
Radius of electro-geometric sphere m 20 30 45 60
Probability of flash % 99 98 95 90
Table 1 – Lightning flash parameters from [IEC  ]
Cotonou, Benin, July 2012

13. Earthing and bonding procedures applied to the external area
Figure 1 – General view of earthing and bonding procedures
in the external area
Cotonou, Benin, July 2012

14. Earthing configuration
Figure 5 – Earthing system of the RBS
Cotonou, Benin, July 2012

15. Earthing configuration
A bare conductor forms a ring electrode around the building and another ring around the tower. Multiple earthing conductors are used to interconnect the two rings (three, in the figure).
The distance of the buried conductor from the associated structure shall be approximately 1.0 m, and the depth of the conductor shall be at least 0.5 m.
Vertical rods should be installed along the ring electrode, as shown in Figures 1 and 5. These rods should be made of steel covered with copper or made of galvanized steel, and they shall be attached to the earth electrode by appropriate connectors.
The legs of a metallic tower (or the down conductors of a non-metallic tower) shall be bonded through short connections to the tower's earthing ring. The steel reinforcement of the tower's basement, if any, shall also be connected to the earthing ring (see Figures 1 and 5).
The steel reinforcement of the building's structure shall be bonded to the earthing ring at least at its four corners. If the building is metallic, its feet shall be bonded to the earthing ring.
The earthing ring of the building shall be connected to the main earthing bar (MEB) located inside the building, preferably on the wall that faces the tower. The earthing conductor shall be as short as possible and have 50 mm2 as the minimum cross-section area.
All conductors in contact with the earth should be made of copper or steel covered with copper and have 50 mm2 as the minimum cross-section area. Galvanized steel conductors could also be used, with 90 mm2 as the minimum cross-section area.
A fence usually surrounds the terrain where the RBS is located. If the fence is metallic, some precautions have to be taken in order to minimize the hazard due to the voltages transferred by the fence.
Cotonou, Benin, July 2012

16. Bonding at the feed-through window
The cable manufacturers usually provide appropriate earthing kits for these connections
Figure 6 – Example of earthing the feeder cable at the feed-through window
Cotonou, Benin, July 2012

17. Use of SPDs Figure 7 – Diagram of the electric board
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18. Installation of SPD in the electric board
Figure 8 – Scheme for SPD installation on TT power systems
The SPDs shall comply with [IEC ]
 The SPD installed in the electric board shall coordinate with the SPD
installed in the power meter station [see IEC  for coordination]
Annex A of [ITU-T K.66] gives information on SPD installation
for different power systems.
Cotonou, Benin, July 2012

19. Protection of telecommunication lines
Figure 11 – Installation of SPD in the distribution frame
 The procedures for the protection of telecommunication lines
against direct and indirect lightning discharges can be found
in [ITU-T K.47] and [ITU-T K.46], respectively, taking into
account [ITU-T K.72].
Cotonou, Benin, July 2012

20. Example of earthing and bonding configuration inside an RBS
 More information on the implementation of earthing and bonding
configurations can be found in [ITU-T K.27] and [ITU‑T K.35
Cotonou, Benin, July 2012

21. Decoupling with power network
 D1 : Distance entre la prise de terre des masses du poste de transformation HTA/BT et la prise de terre du Neutre BT,
 D2 : La distance entre a prise de terre des masses du poste de transformation HTA/BT et la prise de terre du Site de Radiocommunication,
 D3 : Distance entre a prise de terre du Neutre BT et la prise de terre du Site Radiocommunication
Cotonou, Benin, July 2012

22. Decoupling with power network
Cotonou, Benin, July 2012

23. Protection of Base Stations is based on the combination of :
CONCLUSION
Protection of Base Stations is based on the combination of :
Lightning protection for the building
Protection on incoming lines (SPDs)
Resistibility of equipment
Earthing and bonding of installation
Decoupling with power network
Recommendation ITU-T K.56 provides useful information for the protection of RBS and refers to other relevant Recommendations
Cotonou, Benin, July 2012

24. Thank you
Cotonou, Benin, 19 July 2012