1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T K.111 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2015) SERIES K: PROTECTION AGAINST INTERFERENCE Protection of surrounding structures of telecommunication towers against lightning Recommendation ITU-T K.111 Rec. IT
2、U-T K.111 (11/2015) i Recommendation ITU-T K.111 Protection of surrounding structures of telecommunication towers against lightning Summary Recommendation ITU-T K.111 considers the protection of structures in the area surrounding telecommunication towers (including masts and poles) against damage an
3、d injury derived from direct lightning flashes to the towers. The assessment and protection measures intend to reduce the possible risk derived from the erection of towers, but not to improve the overall lightning protection for every surrounding structure. This Recommendation considers towers whose
4、 height is less than 100 m from ground level, which rarely meets the initiation condition of upward flashes, so that the presence of the tower does not significantly influence the incidence of lightning flashes. Based on the analyses of sources of damage for an individual surrounding structure refer
5、ring to IEC 62305-2, the risk components mostly include the possible influence in the close vicinity of a tower due to earth potential rise (EPR) and the transferred transients through common power feeds. For the former risk component, the hazard resulting from the occurrence of sparking and the inj
6、ury to living beings are under consideration. For the latter, a series of exemption criteria and the corresponding protection (mitigation) measures are recommended. The requirements detailing the implementation of protection measures are also introduced. History Edition Recommendation Approval Study
7、 Group Unique ID* 1.0 ITU-T K.111 2015-11-29 5 11.1002/1000/12668 Keywords Earth potential rise, lightning protection, surrounding structures, telecommunication tower, transferred surge. * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, foll
8、owed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T K.111 (11/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologi
9、es (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommuni
10、cation Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups 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
11、 information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operatin
12、g agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (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“ o
13、r some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice
14、 or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation developmen
15、t process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected 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 s
16、trongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2016 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T K.111 (11/2015) iii Table of Contents Page 1 Scope . 1 2 Ref
17、erences . 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Conventions 3 6 Reference configuration 3 7 Protection of tower vicinity 3 7.1 Need of protection 3 7.2 The assessment of the safety distance 5 7.3 Protection measu
18、res 6 7.4 Protection measures against injury to living beings due to touch and step voltages . 8 8 Protection of local community with common power feed 8 8.1 Need of protection 8 8.2 Protection measures 9 9 Implementation of protection measures 10 Annex A Influence on the lightning risk of the surro
19、unding structures due to the presence of a tower . 11 A.1 Possible lightning risk components derived from erection of a tower . 11 A.2 Risk from EPR on the close vicinity of a tower . 12 A.3 Risk from transferred surge through common power feed . 13 Annex B Determination of parameters for the assess
20、ment of safety distance 16 B.1 Lightning parameters according to LPL . 16 B.2 Reference values of Esoil . 16 B.3 Reference values of typical earthing impedance 17 B.4 Reference values of tower inductance 17 Appendix I Influence of the tower on the ground flash density 18 I.1 Downward flash 18 I.2 Up
21、ward flash 18 Bibliography. 20 Rec. ITU-T K.111 (11/2015) 1 Recommendation ITU-T K.111 Protection of surrounding structures of telecommunication towers against lightning 1 Scope This Recommendation considers the protection of structures in the neighbourhood of telecommunication towers (including mas
22、ts and poles) against damage and injury derived from direct lightning flashes to the towers. These protection measures intend to reduce the possible risk derived from the erection of towers, but not to improve the overall lightning protection for every surrounding structure. The systemic protection
23、for these structures should refer to the IEC 62305-x series. This Recommendation only considers towers whose heights are less than 100 m from ground level. Towers higher than 100 m or those situated on mountain ridges or high hills are not considered in this Recommendation. The lightning protection
24、of telecommunication sites attached to the tower, such as a radio base station (RBS) and a dedicated telecommunication building, is not included in this Recommendation. To this aim, the user should refer to the corresponding Recommendations, such as b-ITU-T K.27, b-ITU-T K.35, b-ITU-T K.56 and b-ITU
25、-T K.97. The lightning protection of service lines, such as power lines and telecommunication lines, is not included in this Recommendation. The information about telecommunication lines is given in b-ITU-T K.46 and b-ITU-T K.47. 2 References The following ITU-T Recommendations and other references
26、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 revision; users of this Recommendation are therefore encouraged to investigat
27、e 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 Recommendation does not give it, as a stand-alone document, the status o
28、f a Recommendation. ITU-T K.39 Recommendation ITU-T K.39 (1996), Risk assessment of damages to telecommunication sites due to lightning discharges. ITU-T K.66 Recommendation ITU-T K.66 (2011), Protection of customer premises from overvoltage. IEC 62305-1 IEC 62305-1 (2010), Protection against lightn
29、ing Part 1: General principles. IEC 62305-2 IEC 62305-2 (2010), Protection against lightning Part 2: Risk management. IEC 62305-3 IEC 62305-3 (2010), Protection against lightning Part 3: Physical damage to structures and life hazard. IEC 62305-4 IEC 62305-4 (2010), Protection against lightning Part
30、4: Electrical and electronic systems within structures. 2 Rec. ITU-T K.111 (11/2015) 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 conventional earthing impedance IEC 62305-1: Ratio of the peak values of the earth-termination voltage
31、and the earth-termination current which, in general, do not occur simultaneously. 3.1.2 coordinated SPD system IEC 62305-1: SPDs properly selected, coordinated and installed to form a system intended to reduce failures of electrical and electronic systems. 3.1.3 dangerous event IEC 62305-2: Lightnin
32、g flash to or near the structure to be protected, or to or near a line connected to the structure to be protected that may cause damage. 3.1.4 downward flash IEC 62305-1: Lightning flash initiated by a downward leader from cloud to earth. NOTE A downward flash consists of a first impulse, which can
33、be followed by subsequent impulses. One or more impulses may be followed by a long stroke. 3.1.5 lightning protection level (LPL) IEC 62305-1: Number related to a set of lightning current parameters values relevant to the probability that the associated maximum and minimum design values will not be
34、exceeded in naturally occurring lightning. NOTE Lightning protection level is used to design protection measures according to the relevant set of lightning current parameters. 3.1.6 radio base station b-ITU-T K.56: Installation intended to provide access to the telecommunication system by means of r
35、adio waves. 3.1.7 surge protective device (SPD) IEC 62305-1: Device intended to limit transient overvoltages and divert surge currents; contains at least one non-linear component. 3.1.8 upward flash IEC 62305-1: Lightning flash initiated by an upward leader from an earthed structure to cloud. NOTE A
36、n upward flash consists of a first long stroke with or without multiple superimposed impulses. One or more impulses may be followed by a long stroke. 3.2 Terms defined in this Recommendation This Recommendation defines the following term: 3.2.1 common power feed: A low voltage distribution system wh
37、ich makes the powered buildings and installations interconnected through the same low voltage line. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: EPR Earth Potential Rise LPL Lightning Protection Level LPS Lightning Protection System LV Low Voltage M
38、V Medium Voltage RBS Radio Base Station SPD Surge Protective Device Rec. ITU-T K.111 (11/2015) 3 5 Conventions None. 6 Reference configuration Figure 1 shows the typical layout scenario consisting of the telecommunication tower and the affected surrounding structures (area) in the neighbourhood. In
39、this figure, the possibly affected items are divided into two parts according to the corresponding risk components introduced in Annex A. These two parts can be classified as tower vicinity and local community and are defined as follows: tower vicinity: Includes the close vicinity around the tower w
40、ithin a limited distance from the edge of the telecommunication site. In this area, the current density and the voltage gradient is much larger than that of the far vicinity. There is the possible risk of injury to living beings by electric shock due to step and touch voltages and/or the hazard resu
41、lting from the occurrence of sparking between the tower and the metal parts of adjacent structures. local community: Includes the premises and installations connected with the telecommunication site through common low voltage (LV) power feeds, which suffer the influence of transferred surge from the
42、 interconnected LV power lines. If the telecommunication site is supplied by a dedicated transformer, the influence of transferred surge through medium voltage (MV) power lines can be negligible. NOTE 1 The earth-termination system of the tower shall comply with IEC 62305-3 and b-ITU-T K.56. NOTE 2
43、There may be other interconnected lines, such as telecommunication lines, and their influence is under study. NOTE 3 If the tower is erected on a rented building, the overall risk re-assessment and protection are needed for the rented building according to the IEC 62305-x series. Figure 1 Reference
44、configuration 7 Protection of tower vicinity 7.1 Need of protection The risk assessment shall be performed in order to determine a lightning protection level (LPL) for the determination of safety distances and the design of protection measures. 4 Rec. ITU-T K.111 (11/2015) For the particular applica
45、tion, this Recommendation presents a simplified approach for the evaluation of the protection need based on IEC 62305-2. In this approach, the protection needs can be evaluated by considering the frequency of damage (F), as described in ITU-T K.39. F = ND Pdis (1) where: ND is the number of direct f
46、lashes to the tower per year Pdis is the protection factor of the safety distance. When the frequency of damage is greater than the tolerable value (F FT), then protection measures are necessary. The tolerable frequency of damage value should be defined by the owner of the tower or the authority hav
47、ing jurisdiction according to the hazard level resulting from the occurrence of sparking. For example, FT = 0.05 means that, on average, 1 damage in 20 years (1/20) is acceptable. NOTE 1 Each surrounding structure in the close vicinity of the tower may have different tolerable values. NOTE 2 In some
48、 countries, the relative authority having jurisdiction may specify the safe separation between the dangerous structures (e.g., gas station, explosive storage building) and the tower directly. The expected number of direct flashes to the tower per annum (ND) can be evaluated by: ND = NG (3H)2 CD 106
49、(2) where: NG is the lightning ground flash density (1/km2 year) H is the height of the tower (m) CD is the location factor of the tower considering the relative height of the tower with respect to the surrounding objects or the ground within a distance of 3 H from the tower (see Table 1). Table 1 Structure location factor CD Relative location CD Tower surrounded by higher objects 0.25 Tower surrounded by objects of the same height or shorter 0.5 Isolated tower: no
