Cotonou, Benin, 19 July 2012 Relevant ITU-T Recommendations for the Protection of Base Stations Ahmed ZEDDAM Ahmed ZEDDAM, ITU-T SG5 Chair France Telecom.

Cotonou, Benin, 19 July 2012

Relevant ITU-T Recommendations for the Protection of Base Stations

Ahmed ZEDDAMAhmed ZEDDAM,ITU-T SG5 Chair

France Telecom Orange

ITU Workshop on “Tackling climate change and Specific Absorption

Rate (SAR) Measurement”

(Cotonou, Benin, 19 July 2012)

Cotonou, Benin, 19 July 2012 2

INTRODUCTION

LIGHTNING PROTECTION

RECOMMENDATION ITU-T K.56 Need of Protection

Earthing and Bonding procedures

Use of SPDs

DECOUPLING WITH POWER NETWORK CONCLUSION

Outline

3 Cotonou, Benin, 19 July 2012

Introduction

Protection 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

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

5


Resistibility and protection

Preventing equipment damage may require a combination of resistibility and protection

Resistibility isThe ability of the equipment to withstand an overvoltage or overcurrent

Protection isThe addition of primary protection to prevent damage from larger surges

Need to check that the protector operates and protects the equipment

6Cotonou, Benin, 19 July 2012

Lightningdischargescan reach a

telecommunicationsystem by the

followingmechanisms:

Lightning Protection

7 Cotonou, Benin, 19 July 2012

Direct strikes



Coupling throughthe earth



Coupling throughelectromagnetic fields



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:


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 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 frames


Need of protection

The risk assessment of the RBS shall be performed according to [IEC 62305-2] 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.

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Parameter Unit

LPL

I II III IV

Maximum peak current kA 200 150 100 100

Maximum current rate of rise kA/s 200 150 100 100

Radius of electro-geometric sphere m 20 30 45 60

Probability of flash % 99 98 95 90

Table 1 – Lightning flash parameters from [IEC 62305-1]

Earthing and bonding procedures applied to the external area


Figure 1 – General view of earthing and bonding procedures in the external area

Earthing configuration


K.56(10)_F05

Fence earthing ring Fence Bonding betweenfence and ring

Buildingearthing ring Feeder tray

Tower earthing ring

Verticalrod

Power meterstation

RBS building

Gateearthing

Figure 5 – Earthing system of the RBS

Earthing 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 1.0 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

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Bonding at the feed-through window


Figure 6 – Example of earthing the feeder cable at the feed-through window

Use of SPDs

Cotonou, Benin, July 2012 17Figure 7 – Diagram of the electric board

Installation of SPD in the electric board


Figure 8 – Scheme for SPD installation on TT power systems

The 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 IEC 61643-12 for coordination]

Annex A of [ITU-T K.66] gives information on SPD installation for different power systems.

Protection of telecommunication lines


K.56(10)_F11

Telecommunication cable

To the equipment

SPD

Fail safe

To the mainearthing bar

Distribution frameearthing bar

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].

Figure 11 – Installation of SPD in the distribution frame

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

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

Decoupling with power network


CONCLUSION

Protection of Base Stations is based on the combination of :

Lightning protection Lightning protection for the buildingProtection on incoming lines (SPDsSPDs)

ResistibilityResistibility of equipment

Earthing and bonding Earthing and bonding of installation

DecouplingDecoupling with power network

Recommendation ITU-T K.56 ITU-T K.56 provides useful information for the protection of RBS and refers to other relevant Recommendations



Thank you

Cotonou, Benin, 19 July 2012 Relevant ITU-T Recommendations for the Protection of Base Stations Ahmed ZEDDAM Ahmed ZEDDAM, ITU-T SG5 Chair France Telecom.

Documents

protection of equipment

protection procedures

protection resistibility

building protection

external protection

need of protection

protection techniques

earth lightning protection