1、 International Telecommunication Union ITU-T L.70TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2007) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Managing active electronics in the outside plant Recommendation ITU-T L.70 Rec. ITU-T L.70 (11/
2、2007) i Recommendation ITU-T L.70 Managing active electronics in the outside plant Summary Recommendation ITU-T L.70 refers to the application of active electronics in outdoor environments. It covers mechanical and environmental protection as well as electrical powering and cooling. It also pays att
3、ention to maintenance, security and environmental aspects. Source Recommendation ITU-T L.70 was approved on 6 November 2007 by ITU-T Study Group 6 (2005-2008) under Recommendation ITU-T A.8 procedure. ii Rec. ITU-T L.70 (11/2007) FOREWORD The International Telecommunication Union (ITU) is the United
4、 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 studying technical, operating and tariff questions and issuing Recommendat
5、ions 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 groups which, in turn, produce Recommendations on these topics. The approv
6、al 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 with ISO and IEC. NOTE In this Recommendation, the expression “Administratio
7、n“ 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 provisions (to ensure e.g. interoperability or applicability) and compliance w
8、ith 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 such words does not suggest that compliance with the Recommendation is requi
9、red 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 position concerning the evidence, validity or applicability of claimed Intellect
10、ual 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, protected by patents, which may be required to implement this Recommendation. How
11、ever, 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 2008 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the p
12、rior written permission of ITU. Rec. ITU-T L.70 (11/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation. 2 4 Abbreviations and acronyms 2 5 Packaging for environmental and mechanical protection. 3 5.1 Environments 3
13、 5.2 Sealing against ingress of solids and fluids 3 5.3 Resistance to aggressive agents 3 5.4 Mechanical protection 4 6 Thermal management . 4 6.1 Thermal model 4 6.2 Operational temperature range of the electronics. 5 6.3 Enclosure design. 5 7 Electrical powering. 5 7.1 Connection to the power grid
14、 . 6 7.2 Remote line powering. 6 7.3 Backup power. 6 8 Maintenance aspects . 6 9 Safety and environmental aspects. 7 9.1 Electrical safety 7 9.2 Vandalism and accidental damage . 7 9.3 External temperature 8 9.4 Acoustical noise 8 9.5 Physical obstruction and visual integration in the environment. 8
15、 9.6 Electromagnetic compatibility 8 Annex A Environmental classification . 9 A.1 Basic outdoor environmental classes 9 A.2 Special conditions. 9 Appendix I Thermal design of above ground enclosures . 11 I.1 Single wall, natural convection 11 I.2 Vented dual wall, natural convection . 12 I.3 Forced
16、convection 12 I.4 Air-to-air heat exchangers 13 I.5 Natural and forced ventilation 13 iv Rec. ITU-T L.70 (11/2007) Page I.6 Active cooling (“chillers“) 15 I.7 Heaters 15 Appendix II Thermal properties of underground enclosures 16 II.1 Free or forced convection inside 16 II.2 Heat exchanger . 17 Appe
17、ndix III Example of performance specification for active street cabinets (ground level and above ground, OG and OA) 18 III.1 Evaluation criteria 18 III.2 Test program. 19 Appendix IV Example of performance specification for underground level (OS). 21 IV.1 Evaluation criteria 21 IV.2 Test program. 21
18、 Bibliography. 27 Rec. ITU-T L.70 (11/2007) v Introduction In order to obtain maximum reliability at a minimal cost, network electronics are generally centralized in locations with controlled environments. This is also typical for the initial lay out of copper networks for plain old telephone servic
19、e (POTS). However, with the increasing demand for connections and bandwidth, operators often face the need to apply active electronics at remote locations. These active nodes cannot always be located inside buildings. This Recommendation focuses on the aspects of active electronics, located at outsi
20、de plant locations. Active network nodes in outside plant have a number of characteristics that make their design and maintenance more complex than that of passive nodes: active nodes perform a transformation between input and output signal; active nodes require electrical powering; active nodes dis
21、sipate heat. Rec. ITU-T L.70 (11/2007) 1 Recommendation ITU-T L.70 Managing active electronics in the outside plant 1 Scope This Recommendation lists the elements to consider when applying network electronics in outside plant locations (both in above ground and in underground applications): mechanic
22、al and environmental protection and related sealing requirements; thermal management; electrical powering; safety and environmental aspects; maintenance aspects. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute
23、 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 most recent edition of the Recomme
24、ndations 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.34 Recommendation ITU-T K.34 (2003), Cla
25、ssification of electromagnetic environmental conditions for telecommunication equipment Basic EMC Recommendation. 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 telecomm
26、unication equipment exposed to overvoltages and overcurrents Basic Recommendation. ITU-T K.45 Recommendation ITU-T K.45 (2008), Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages and overcurrents. ITU-T K.48 Recommendation ITU-T K.48 (2006), EMC r
27、equirements for telecommunication equipment Product family Recommendation. ITU-T K.50 Recommendation ITU-T K.50 (2000), Safe limits of operating voltages and currents for telecommunication systems powered over the network. ITU-T K.51 Recommendation ITU-T K.51 (2000), Safety criteria for telecommunic
28、ation equipment. ITU-T K.55 Recommendation ITU-T K.55 (2002), Overvoltage and overcurrent requirements for insulation displacement connectors (IDC) terminations. ITU-T K.64 Recommendation ITU-T K.64 (2004), Safe working practices for outside equipment installed in particular environments. ITU-T K.65
29、 Recommendation ITU-T K.65 (2004), Overvoltage and overcurrent requirements for termination modules with contacts for test ports or SPDs. 2 Rec. ITU-T L.70 (11/2007) ITU-T K.69 Recommendation ITU-T K.69 (2006), Maintenance of protective measures. ITU-T L.51 Recommendation ITU-T L.51 (2003), Passive
30、node elements for fibre optic networks General principles and definitions for characterization and performance evaluation. IEC 60529 IEC 60529 (2001), Degrees of protection provided by enclosures (IP Code) . IEC 60950-1 IEC 60950-1 (2005), Information technology equipment Safety Part 1: General requ
31、irements. IEC 60950-21 IEC 60950-21 (2002), Information technology equipment Safety Part 21: Remote power feeding. IEC 62262 IEC 62262 (2002), Degrees of protection provided by enclosures for electrical equipment against external mechanical impacts (IK code). 3 Definitions 3.1 Terms defined elsewher
32、e This Recommendation uses the following terms defined elsewhere: 3.1.1 IP 55 IEC 60529: Enclosures protected against dust and resistant to jets of water. 3.1.2 IP 68 IEC 60529: Enclosures suitable for permanent submersion. 3.2 Terms defined in this Recommendation This Recommendation defines the fol
33、lowing terms: 3.2.1 active electronics: Electronics requiring a source of electricity (other than the actual signal) in order to execute its function. 3.2.2 active node: Network node, including active electronics as well as the packaging required to protect it sufficiently from external influences a
34、s they occur in the environment in which it resides. 3.2.3 temperature-hardened equipment: Electronic equipment that has been designed or adapted to operate in outdoor temperature conditions (e.g., from 40C to +65C). 4 Abbreviations and acronyms This Recommendation uses the following abbreviations a
35、nd acronyms: DSLAM Digital Subscriber Line Access Multiplexer EMC Electromagnetic Compatibility IDC Insulation Displacement Connector IP Ingress Protection (rating) OA Outdoor Above ground level (aerial) OG Outdoor Ground level OS Outdoor Below ground level (subterranean) SPD Surge Protective Device
36、 Rec. ITU-T L.70 (11/2007) 3 5 Packaging for environmental and mechanical protection Any node in the outside plant needs to be packaged properly to protect its content from the influences of the environment. 5.1 Environments Active nodes in outside plant may be located in three typical locations: OA
37、: Outdoor above ground level (aerial), mounted on a wall or pole or hanging from an aerial cable. OG: Outdoor at ground level, stored in a cabinet or pedestal, standing on the ground, with a base that may reside partially underground. OS: Outdoor below ground level (subterranean), stored in an under
38、ground man-hole, hand-hole or directly buried. The typical properties of these environments can be found in Annex A. Compared to passive network nodes (e.g., as described in ITU-T L.51 on passive optical nodes), a certain amount of heat is generated inside the enclosure by the electronics. Hence, a
39、more detailed approach concerning operating temperatures is required. This is covered in more detail in clause 6 and in Appendices I and II. 5.2 Sealing against ingress of solids and fluids For nodes above or at ground level (OA and OG), the minimum recommended protection level against ingress of ob
40、jects and water is IP 55 according to IEC 60529 (protected against dust and resistant to jets of water). For nodes at ground level (OG), it is recommended to provide a separation plate with cable entrance seals to avoid intrusion of dirt, water, rodents or insects via the bottom. For nodes below gro
41、und level (OS), the recommended sealing level is IP 68 according to IEC 60529 (suitable for permanent submersion). Required submersion depth should be at least 1 m above the top of the enclosure, but may be more if applied in deep manholes (in this case, the maximum required submersion depth is to b
42、e agreed explicitly between user and supplier in order to obtain proper sealing performance and structural strength). 5.3 Resistance to aggressive agents The enclosure containing the electronics should be resistant to the most common aggressive agents as they may occur in the outdoor environments. F
43、or all outdoor environments (OA, OG and OS): all materials (metals) should be resistant to corrosion; all materials should be resistant to micro organisms (fungi/bacteria). For nodes above or at ground level (OA and OG): all external (polymeric) materials, including surface coatings, should be resis
44、tant to UV radiation. For underground nodes (OS): all external materials should be resistant to accidental exposure chemical agents that may occur in underground along side roads, such as oil, diesel, kerosene, acids, bases and surfactants (detergents). 4 Rec. ITU-T L.70 (11/2007) 5.4 Mechanical pro
45、tection The enclosure should be resistant to the mechanical loads and influences that it may encounter in the outdoor environment. For nodes above or at ground level (OA and OG): a minimum recommended protection level against impact of IK 10 according to IEC 62262; the enclosures, including fixation
46、 system, should resist loads induced by wind. For underground nodes (OS): Enclosure should be resistant to accidental impact from above. Enclosure should be resistant to a static load on top equivalent to the weight of at least one installer. Node should be resistant to vibration and shock. Cables m
47、ust be properly attached to resist axial tension, flexure and torsion loads that may occur during typical installation and maintenance. 6 Thermal management The temperature inside the enclosure (Tinside) must be kept within the operational temperature range of the electronics. 6.1 Thermal model The
48、temperature inside an above ground active enclosure will be determined by a number of factors: the air temperature of the environment (Tair) (as measured in a thermometer hut); solar radiation; the heat dissipated by the electronics (Q); the construction of the enclosure. Figure 6-1 Above ground act
49、ive node Rec. ITU-T L.70 (11/2007) 5 For underground nodes, a similar model is applicable, however, there will be no direct solar exposure to the enclosure, while the dissipated heat is transferred via the hand-hole and the surrounding soil. Figure 6-2 Underground active node 6.2 Operational temperature range of the electronics Electronic equipment is typically qualified to an operational temperature range of 0C to +40C, corresponding to an indoor controlled envi
