International Telecommunication Union

Cotonou, Benin, 19 July 2012Relevant ITU-T Recommendations for the Protection of Base StationsAhmed ZEDDAM,ITU-T SG5 Chair France Telecom OrangeITU Workshop on Tackling climate change and Specific Absorption Rate (SAR) Measurement

(Cotonou, Benin, 19 July 2012)

1Cotonou, Benin, 19 July 20122INTRODUCTION LIGHTNING PROTECTION RECOMMENDATION ITU-T K.56Need of ProtectionEarthing and Bonding proceduresUse of SPDsDECOUPLING WITH POWER NETWORK

CONCLUSION

Outline23Cotonou, Benin, 19 July 2012

IntroductionProtection of an installation may require a combination of:Lightning protection for the buildingProtection on incoming linesResistibility of equipmentEarthing and bonding of installation

This presentation is about the protection of equipment within a base station 4Cotonou, Benin, 19 July 2012

SG 5 role in equipment protectionSG 5 is unique SDO in overvoltage protection

Ensures coordination of the equipment and external protection

Considers installation practices and their effect on resistibility requirements5Cotonou, Benin, 19 July 2012

Resistibility and protectionPreventing equipment damage may require a combination of resistibility and protectionResistibility isThe ability of the equipment to withstand an overvoltage or overcurrent

Protection isThe addition of primary protection to prevent damage from larger surgesNeed to check that the protector operates and protects the equipment

6Cotonou, Benin, 19 July 2012

Lightningdischargescan reach atelecommunicationsystem by thefollowingmechanisms: Lightning Protection67Cotonou, Benin, 19 July 2012

Direct strikesLightning Protection8Cotonou, Benin, 19 July 2012

Coupling throughthe earthLightning Protection9Cotonou, Benin, 19 July 2012

Coupling throughelectromagnetic fields

Lightning Protection10Cotonou, Benin, 19 July 2012 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:

Lightning Protection10Recommendation ITU-T K.56 : Protection of radio base stations against lightning dischargesPresents the techniques applied to a telecom. radio base station in order to protect it against lightning dischargesThe need of protection is obtained from the methodology contained in IEC 62305-2, which is used to determine the relevant lightning protection level (LPL) for the installationThe 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 stationThe 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 framesCotonou, Benin, 19 July 201211Need of protectionThe risk assessment of the RBS shall be performed according to [IEC62305-2] in order to determine a Lightning Protection Level (LPL) for the design of the protection procedures. Table1 shows some lightning flash parameters associated with each LPL.

Cotonou, Benin, July 201212ParameterUnit LPLIIIIIIIVMaximum peak currentkA200150100100Maximum current rate of risekA/s200150100100Radius of electro-geometric spherem20304560Probability of flash%99989590Table 1Lightning flash parameters from [IEC62305-1] Earthing and bonding procedures applied to the external areaCotonou, Benin, July 201213

Figure 1 General view of earthing and bonding procedures in the external areaEarthing configuration Cotonou, Benin, July 201214

Figure 5 Earthing system of the RBSEarthing configurationA 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 1.0m, and the depth of the conductor shall be at least 0.5m.Vertical rods should be installed along the ring electrode, as shown in Figures 1 and5. 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 and5).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 50mm2 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 201215Bonding at the feed-through windowCotonou, Benin, July 201216

Figure 6 Example of earthing the feeder cable at the feed-through windowThe cable manufacturers usually provide appropriate earthing kits for these connectionsUse of SPDsCotonou, Benin, July 201217

Figure7 Diagram of the electric boardInstallation of SPD in the electric boardCotonou, Benin, July 201218

Figure8 Scheme for SPD installation on TT power systemsThe SPDs shall comply with [IEC 61643-11] The SPD installed in the electric board shall coordinate with the SPD installed in the power meter station [see IEC61643-12 for coordination] Annex A of [ITU-TK.66] gives information on SPD installation for different power systems.Protection of telecommunication lines Cotonou, Benin, July 201219

The procedures for the protection of telecommunication lines against direct and indirect lightning discharges can be found in [ITU-TK.47] and [ITU-TK.46], respectively, taking into account [ITU-T K.72].Figure11 Installation of SPD in the distribution frameExample of earthing and bonding configuration inside an RBS Cotonou, Benin, July 201220

More information on the implementation of earthing and bonding configurations can be found in [ITU-TK.27] and [ITUTK.35 Decoupling with power networkCotonou, Benin, July 201221

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 Decoupling with power networkCotonou, Benin, July 201222

CONCLUSIONProtection of Base Stations is based on the combination of : Lightning protection for the buildingProtection on incoming lines (SPDs)Resistibility of equipmentEarthing and bonding of installationDecoupling 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 201223Cotonou, Benin, 19 July 201224Thank you24