1、 International Telecommunication Union ITU-T K.72TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (04/2008) SERIES K: PROTECTION AGAINST INTERFERENCE Protection of telecommunication lines using metallic conductors against lightning Risk management Recommendation ITU-T K.72 Rec. ITU-T K.72 (04/2008) i
2、 Recommendation ITU-T K.72 Protection of telecommunication lines using metallic conductors against lightning Risk management Summary Recommendation ITU-T K.72 gives the methodology for evaluating the need for protection measures against lightning of telecommunication lines using metallic conductors.
3、 This method is based on the risk assessment: protection measures are necessary when the risk is greater than the tolerable risk. Maximum value of the tolerable risks is suggested. This Recommendation considers the risk of loss of service of the telecommunication network. The risk is evaluated throu
4、gh the risk components caused by lightning, which is the source of damage on telecommunication line as a function of the striking point with respect to the telecommunication line (lightning flashes direct to the line, near the line, or directly to the structures connected at the ends of the line). T
5、his Recommendation shall be used together with Recommendation ITU-T K.47, which provides the risk assessment and the protection measures against lightning flashes direct to the telecommunication line and to structures connected at the ends of the telecommunication line, and Recommendation ITU-T K.46
6、, which provides the risk assessment and the protection measures against lightning flashes near the telecommunication line. Source Recommendation ITU-T K.72 was approved on 13 April 2008 by ITU-T Study Group 5 (2005-2008) under Recommendation ITU-T A.8 procedure. Keywords Lightning, node, protection
7、, risk, risk assessment, SPD, surge, telecommunication line. ii Rec. ITU-T K.72 (04/2008) 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
8、 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 Telecommunication Standardization Assembly (WTS
9、A), 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 information technology which fall w
10、ithin 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 operating agency. Compliance with this Recom
11、mendation 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“ or some other obligatory language such
12、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 RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommenda
13、tion 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 development process. As of the date of approval
14、 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 strongly urged to consult the TSB pate
15、nt database at http:/www.itu.int/ITU-T/ipr/. ITU 2009 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.72 (04/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations and ac
16、ronyms 3 5 Reference configuration 4 6 Explanation of terms. 5 6.1 Damage and loss. 5 6.2 Risk and risk components. 6 6.3 Composition of risk components related to a telecommunication network . 7 7 Risk management . 7 7.1 Basic procedure 7 7.2 Tolerable risk RT. 7 7.3 Specific procedure to evaluate
17、the need for protection 7 7.4 Protection measures 8 7.5 Selection of protection measures 8 iv Rec. ITU-T K.72 (04/2008) Introduction Lightning flashes to earth may be hazardous to telecommunication networks. The hazard to telecommunication networks can result in: injury of people inside the structur
18、es connected to the telecommunication line; physical damage (e.g., cable destruction) to the telecommunication line; failure (e.g., insulation breakdown) of the telecommunication line; failure of the associated electrical and electronic equipment inside the structure (i.e., exchange, customers build
19、ing, or remote electronic site). To reduce the loss due to lightning, protection measures may be required. Whether they are needed, and to what extent, should be determined by the risk assessment. The risk, defined in this Recommendation as the probable average annual service loss in a telecommunica
20、tion network due to lightning flashes, depends on: the annual number of lightning flashes influencing the telecommunication line; the probability of damage by one of the influencing lightning flashes; the mean amount of consequential loss. Lightning flashes influencing the telecommunication line may
21、 be divided into: flashes terminating on the telecommunication line; flashes terminating near the telecommunication line; flashes direct to a structure connected to the telecommunication line. Flashes to a telecommunication line may cause physical damage. Flashes near the telecommunication line, as
22、well as flashes to a structure connected to a telecommunication line, may cause failure of the telecommunication line and of electrical and electronic systems inside the structures due to overvoltages resulting from resistive and inductive coupling of these systems with the lightning current. The nu
23、mber of lightning flashes influencing the telecommunication network depends on the dimensions and the characteristics of the telecommunication network, on the environment characteristics, as well as on lightning ground flash density in the region where the telecommunication network is located. The p
24、robability of lightning damage depends on the telecommunication network, on the lightning current characteristics, as well as on the type and efficiency of applied protection measures. The annual mean amount of the consequential loss depends on the extent of damage and the consequential effects whic
25、h may occur as result of a lightning flash. The effect of protection measures results from the features of each protection measures and may reduce the damage probabilities or the amount of consequential loss. The assessment of risk due to all possible effects of lightning flashes to telecommunicatio
26、n networks is given in this Recommendation. The decision to provide lightning protection may be taken regardless of the outcome of any risk assessment where there is a desire that there be no avoidable risk. Rec. ITU-T K.72 (04/2008) 1 Recommendation ITU-T K.72 Protection of telecommunication lines
27、using metallic conductors against lightning Risk management 1 Scope This Recommendation deals with the risk management of lightning protection of telecommunication networks using cables with metallic conductors. The risk assessment is limited to physical damage and failure of insulation of telecommu
28、nication lines (buried or aerial cables, shielded or unshielded cables) which can cause the loss of service. This Recommendation provides a procedure for the evaluation of such a risk. Once an upper tolerable limit for the risk has been selected, this procedure allows the selection of appropriate pr
29、otection measures to be adopted to reduce the risk to a level at or below the tolerable limit. This Recommendation shall be used together with ITU-T K.47, which provides the risk assessment and the protection measures against lightning flashes to the telecommunication line and to structures connecte
30、d to the telecommunication line, and ITU-T K.46, which provides the risk assessment and the protection measures against lightning flashes near the telecommunication line. The protection need for line equipment (such as multiplexers, power amplifiers, optical network units) and line termination equip
31、ment is not considered in this Recommendation and it should be evaluated using the risk assessment applied to the structure where the equipment is located (i.e., exchange, customers building, or remote electronic site). The protection of persons using telecommunication equipment inside the customers
32、 structure, from dangerous situations caused by touch voltages is outside the scope of this Recommendation and it should be evaluated using the risk assessment applied to the customers structure. 2 References The following ITU-T Recommendations and other references contain provisions which, through
33、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 investigate the possibility of applying the
34、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 of a Recommendation. ITU-T K.46 Rec
35、ommendation 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 lightning discharges. ITU-T K.60 Reco
36、mmendation ITU-T K.60 (2008), Emission levels and test methods for wireline telecommunication networks to minimize electromagnetic disturbance of radio services. IEC 62305-2 IEC 62305-2 (2006), Protection against lightning Part 2: Risk management. 2 Rec. ITU-T K.72 (04/2008) 3 Definitions This Recom
37、mendation defines the following terms: 3.1 dangerous event: Lightning flash to or near the telecommunication line to be protected which causes a dangerous surge voltage due to lightning. 3.2 dangerous surge voltage due to lightning: A surge voltage whose peak value Upis greater than the equipment re
38、sistibility or the conductor insulation surge voltage withstand level of the telecommunication line. 3.3 electronic system: System incorporating sensitive electronic components such as communication equipment, computers, control and instrumentation systems, radio systems, power electronic installati
39、ons. 3.4 failure of electrical and electronic systems: Permanent damage of electrical and electronic systems due to surges. 3.5 lightning flash near a line: Lightning flash striking close enough to a line to be protected that it may cause dangerous surges. 3.6 lightning flash to a structure connecte
40、d to the line to be protected: Lightning flash striking the structure connected to the line to be protected. 3.7 line to be protected: Line connected to a structure for which protection is required against the effects of lightning in accordance with this Recommendation. 3.8 loss LX: Annual mean amou
41、nt of loss (humans and goods) consequent to a specified type of damage due to a dangerous event, relative to the total value (humans and goods) of the object to be protected. 3.9 metallic symmetric conductors: Transmission media consisting of a pair of twisted wires balanced with respect to earth, u
42、sually assembled in groups in order to form a telecommunication cable. 3.10 node: Point between sections of a telecommunication line. NOTE The list of nodes on a telecommunication installation is shown in the reference configuration (clause 5). 3.11 physical damage: Damage to a telecommunication lin
43、e due to mechanical and thermal effects of lightning. 3.12 protection measures: Measures to be adopted in the telecommunication installation to be protected to reduce the risk. 3.13 risk component RX: Partial risk depending on the source and the type of damage. 3.14 risk of loss of service R2: Value
44、 of probable average annual loss of service due to lightning, relative to the total value of service of the telecommunication installation to be protected. NOTE The risk R2, used by IEC 62305-2, refers to the risk of loss of service related to a structure. 3.15 risk R: Value of probable average annu
45、al loss (humans and goods) due to lightning, relative to the total value (humans and goods) of the object to be protected. 3.16 section of a telecommunication line SS: Part of a telecommunication line with homogeneous characteristics where only one set of parameters is involved in the assessment of
46、a risk component. 3.17 source of damage: The source of damage depends on the position of the point of strike relative to the considered line: Source of damage S1: Flashes to the structure (the exchange, the customers building, or remote site) where the telecommunication or the signalling line enters
47、; Rec. ITU-T K.72 (04/2008) 3 Source of damage S2: Flashes near the structure (the exchange, the customers building, or remote site) where the telecommunication or the signalling line enters; Source of damage S3: Flashes to the telecommunications line entering the structure (the exchange, the custom
48、ers building, or remote site); Source of damage S4: Flashes near the telecommunication line entering the structure (the exchange, the customers building, or remote site). 3.18 surge: Temporary excessive voltage or current, or both, coupled on a telecommunication line from an external electrical sour
49、ce. NOTE 1 Typical electrical sources are lightning and AC/DC power systems. NOTE 2 Electrical source coupling can be one or more of the following: electric field (capacitive), magnetic field (inductive), conductive (resistive), electromagnetic field. 3.19 surge due to lightning: A surge which is caused by lightning through any type of electromagnetic (conductive, inductive and capacitive) coupling. NOTE It is characterized by the following five parameters: peak value; front time, T1, and time to half value, T2(or time pa
