1、 International Telecommunication Union ITU-T K.56TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2010) SERIES K: PROTECTION AGAINST INTERFERENCE Protection of radio base stations against lightning discharges Recommendation ITU-T K.56 Rec. ITU-T K.56 (01/2010) i Recommendation ITU-T K.56 Protecti
2、on of radio base stations against lightning discharges Summary Recommendation ITU-T K.56 presents the techniques applied to a telecommunication radio base station in order to protect it against lightning discharges. The need of protection is obtained from the methodology contained in IEC 62305-2, wh
3、ich 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. T
4、he 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. This Recommendation also provides guidelines in order to achieve ade
5、quate protection of the telecommunication equipment based on the coordination between equipment resistibility, SPD protection level and installation characteristics. History Edition Recommendation Approval Study Group 1.0 ITU-T K.56 2003-07-29 5 2.0 ITU-T K.56 2010-01-13 5 ii Rec. ITU-T K.56 (01/201
6、0) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for s
7、tudying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study g
8、roups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis wit
9、h ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provi
10、sions (to ensure e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of su
11、ch words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no positi
12、on concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protect
13、ed by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 All rights reserved. No part of
14、this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T K.56 (01/2010) iii CONTENTS Page 1 Scope and purpose 1 2 References. 1 3 Definitions 2 4 Abbreviations and acronyms 2 5 Need of protection 2 6 External area . 3 6.1 Lightning protecti
15、on system (LPS) 3 6.2 Bonding in the tower 4 6.3 Earthing 7 6.4 Power meter station 8 7 Equipment building 9 7.1 Feeder and lighting cables 9 7.2 Power conductors . 11 7.3 Telecommunication conductors 14 7.4 Earthing and bonding of metallic elements 16 8 Protection of RBS equipment . 18 8.1 Inductiv
16、e voltage drop across the SPD connecting leads . 20 8.2 Voltage induced in the internal cabling 20 Annex A Shielding factor () of cable trays . 22 Annex B Shielding factor () of building walls 24 Annex C Example of earthing and bonding configuration inside an RBS . 25 Appendix I Results of tests wit
17、h rocket-triggered lightning on a radio base station 26 I.1 Introduction 26 I.2 Description of the test site 26 I.3 Recordings of the lightning current 27 I.4 Shielding factor of tower and feeder tray . 27 I.5 Bonding the feeder to the tower at ground level 28 I.6 Current flowing through service con
18、ductors 29 I.7 Inductive voltage drop in the SPD connecting leads 30 Bibliography. 31 Rec. ITU-T K.56 (01/2010) 1 Recommendation ITU-T K.56 Protection of radio base stations against lightning discharges 1 Scope and purpose This Recommendation addresses radio base stations (RBSs) made of a shelter or
19、 small building to house the equipment and a nearby tower to hold the antennas. The purpose of this Recommendation is to provide a set of procedures to protect the RBS against lightning discharges. ITU-T K.71 gives information on the protection of antenna installations in or on a customer building.
20、2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revisio
21、n; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Re
22、commendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T K.12 Recommendation ITU-T K.12 (2006), Characteristics of gas discharge tubes for the protection of telecommunications installations. ITU-T K.27 Recommendation ITU-T K.27 (1996), Bonding configurations an
23、d earthing inside a telecommunication building. ITU-T K.35 Recommendation ITU-T K.35 (1996), Bonding configurations and earthing at remote electronic sites. ITU-T K.44 Recommendation ITU-T K.44 (2008), Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents Basic
24、 Recommendation. ITU-T K.46 Recommendation ITU-T K.46 (2008), Protection of telecommunication lines using metallic symmetric conductors against lightning-induced surges. ITU-T K.47 Recommendation ITU-T K.47 (2008), Protection of telecommunication lines using metallic conductors against direct lightn
25、ing discharges. ITU-T K.66 Recommendation ITU-T K.66 (2004), Protection of customer premises from overvoltages. ITU-T K.71 Recommendation ITU-T K.71 (2007), Protection of customer antenna installations. ITU-T K.72 Recommendation ITU-T K.72 (2008), Protection of telecommunication lines using metallic
26、 conductors against lightning Risk management. IEC 61643-1 IEC 61643-1 (2005), Low-voltage surge protective devices Part 1: Surge protective devices connected to low-voltage power distribution systems Requirements and tests. IEC 61643-11 IEC 61643-11 (2004), Low-voltage surge protective devices Part
27、 11: Surge protective devices connected to low-voltage power distribution systems Performance requirements and testing methods. IEC 61643-12 IEC 61643-12 (2008), Low-voltage surge protective devices Part 12: Surge protective devices connected to low-voltage power distribution systems Selection and a
28、pplication principles. 2 Rec. ITU-T K.56 (01/2010) IEC 61643-22 IEC 61643-22 (2004), Low-voltage surge protective devices Part 22: Surge protective devices connected to telecommunications and signalling networks Selection and application principles. IEC 62305-1 IEC 62305-1 (2006), Protection against
29、 lightning Part 1: General principles. IEC 62305-2 IEC 62305-2 (2006), Protection against lightning Part 2: Risk management. IEC 62305-3 IEC 62305-3 (2006), Protection against lightning Part 3: Physical damage to structures and life hazard. 3 Definitions The definitions contained in the references a
30、pply to this Recommendation. Additional definitions needed for the protection of radio base stations (RBSs) are as follows: 3.1 cable tray: Rigid structural system used to securely fasten or support cables. 3.2 feeder cable: Wave-guide or coaxial cable that conducts signals to an antenna. 3.3 lightn
31、ing protection system (LPS) rod: Metallic rod that makes part of the LPS and is intended to intercept a lightning strike. It is also designated as “lightning air termination“ or “lightning finial“. 3.4 radio base station: Installation intended to provide access to the telecommunication system by mea
32、ns of radio waves. 3.5 shielding factor: Factor that represents the attenuation of the voltage or current in a conductor due to the presence of a nearby shielding conductor. 3.6 single-pulse peak current: Rated maximum current value which may be applied for a single impulse of specified waveshape, w
33、ithout causing surge protective device (SPD) failure. Typically, this rating is defined using either an 8/20 or 10/350 impulse current waveshape. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: GDT Gas Discharge Tube LPL Lightning Protection Level LPS
34、Lightning Protection System MEB Main Earthing Bar PE Protective Earth RBS Radio Base Station SPD Surge Protective Device 5 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 prot
35、ection procedures. Table 1 shows some lightning flash parameters associated with each LPL. Rec. ITU-T K.56 (01/2010) 3 Table 1 Lightning flash parameters from IEC 62305-1 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 100Radius of
36、 electro-geometric sphere m 20 30 45 60 Probability of flash % 99 98 95 90 NOTE The risk assessment may indicate an LPL for the design of the LPS that is different from the LPL considered for the design of the other protection procedures. 6 External area Figure 1 shows the main earthing and bonding
37、procedures applied to the external area. These procedures, as well as others not shown in the figure, are detailed in the subsequent clauses. 6.1 Lightning protection system (LPS) In order to protect the antennas and auxiliary equipment from a direct strike, it may be necessary to install an LPS in
38、the tower. If the nearby tower does not protect the shelter, it may be necessary to install an LPS in the shelter too. The assessment of the need for an LPS and the determination of its positioning shall be performed with the rolling sphere method described in IEC 62305-3. The following clauses give
39、 some procedures for the installation of the LPS. 6.1.1 Metallic tower The LPS rod(s) shall be connected directly to the structure of the metallic tower. Therefore, the structure of the metallic tower will conduct the stroke current to ground and there is no need to install lightning down conductors
40、. NOTE If the total cross-section of the tower structure is less than 125 mm2, then the tower shall be treated as a non-metallic tower, as described in clause 6.1.2. 6.1.2 Non-metallic tower If the structure that supports the antennas is not metallic (e.g., wood pole) or if it is metallic but its cr
41、oss-section is less than 125 mm2, it is necessary to install two down-conductors to earth the LPS rod(s). The down conductors shall not be insulated from the tower and they shall have a minimum cross-section of 50 mm2each. The down conductors shall be installed on opposite sides of the tower. 6.1.3
42、Building In the majority of the cases, the nearby tower will protect the building against direct strikes. However, the need for an LPS in the building shall be investigated with the rolling sphere method described in IEC 62305-3. If the building requires an LPS, it shall be earthed in the earthing s
43、ystem of the RBS, which is described in clause 6.3. 4 Rec. ITU-T K.56 (01/2010) Figure 1 General view of earthing and bonding procedures in the external area 6.2 Bonding in the tower 6.2.1 Feeder cables The wave-guide and the external conductor of coaxial cables, henceforth referred as feeder cables
44、, shall be bonded to the metallic tower (or to the feeder tray) near the antenna, as shown in Figure 1. A weatherproof connector shall make the connection to the feeder cable in order to avoid corrosion, and the connection to the tower (or feeder tray) structure shall also be protected to avoid ingr
45、ession of moisture. Usually, the cable manufacturers provide appropriated earthing kits for these connections. The earthing kits shall have a connector to be attached on the bare outer surface of the feeder (the feeder plastic outer jacket shall be removed), another connector to be attached to the t
46、ower structure (paint shall be removed) and a conductor bonding the two connectors. The earthing kit shall also contain protective coatings to be applied on the connections. Figure 2 shows schematically the installation of an earthing kit before the application of the protective coating. NOTE 1 For
47、non-metallic towers or metallic towers with a cross-section smaller than 125 mm2, the bonding shall be made to the lightning down conductor. NOTE 2 Some types of antenna are inherently connected to the tower by design. In this case, it is not necessary to use an earthing kit to bond the feeder to th
48、e tower (or feeder tray), as it is already bonded through the antenna structure. Rec. ITU-T K.56 (01/2010) 5 Figure 2 Example of installation of earthing kit on feeder cable (protective coating not shown) Depending on the length of the horizontal section of the feeder tray (from the tower to the equ
49、ipment building), it is recommended to bond the feeder cables to the tower (or to the feeder tray) at the point where they leave the tower (bending point). The minimum length of the horizontal section that requires this bonding is given in Table 2. Table 2 Minimum length of the horizontal section of the feeder tray that requires bonding of feeders at the bending point LPL I II III-IV Feeder tray length 10 m 15 m 20 m NOTE Regardless of the bonding at the bending point, the
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