1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TE LEC0 MM UN I CATI0 N STANDARDIZATION SECTOR OF ITU L.44 (1 0/2000) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Electric power supply for equipment installed as outside plant ITU-T Recommendation L.44
2、 (Formerly CCITT Recommendation) ITU-T Recommendation L.44 Electric power supply for equipment installed as outside plant Summary This Recommendation describes the provision of electric power supply for outside plants of telecommunication networks. It deals with the methods of power feeding and back
3、up systems. Source ITU-T Recommendation L.44 was prepared by ITU-T Study Group 6 (1997-2000) and approved by the World Telecommunication Standardization Assembly (Montreal, 27 September - 6 October 2000). ITU-T L.44 (10/2000) i FOREWORD The International Telecommunication Union (ITU) is the United N
4、ations specialized agency in the field of telecommunications. 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 telecommuni
5、cations 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 approval of ITU-T Recommendations is covered by the procedu
6、re 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 IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecom
7、munication administration and a recognized operating agency. 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, val
8、idity 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, protected by patents, which may be req
9、uired to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or
10、 by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. CONTENTS Page 1 2 3 3.1 3.2 3.3 4 4.1 4.2 4.3 5 5.1 5.2 5.3 6 6.1 6.2 7 7.1 7.2 7.3 Introduction References Power supply methods Power supply from central office . 3.1.1 Metallic tr
11、ansmission 3.1.2 Optical transmission Local power supply 3.2.1 Metallic transmission 3.2.2 Optical transmission Individual power supply . 3.3.1 Metallic transmission 3.3.2 Optical transmission Power sources for usual operation Power company Generator Battery Power wiring Individual power cable . Sup
12、erimposition method . Composite cable (combined power and communication cable) . Power sources for backup . Generator Battery Temperature condition Humidity . Environment for each equipment . Others . Appendix I . ITU-T L.44 (10/2000) 1 1 1 2 2 2 10 . 111 Introduction Some equipment (e.g. repeaters)
13、 needing a power supply had existed before optical fibres were installed. At that time, electrical power had been mainly supplied from the central office by using a superimposition technique or by having insulated communication and power conductors in the same cable. After optical fibres were introd
14、uced, many kinds of optical/electrical equipment which require a power supply system were installed into a telecommunication network, in order to increase capacity. The problem is that optical fibre cannot be used to directly transmit electrical power. Power is supplied by one of three ways: - to fe
15、ed power from the central office by using metallic wires. To connect the power supply between the central office and the equipment, individual metallic cables or cables with both fibres and copper conductors may be used; to use a local power supply. In this method, one power supply provides power to
16、 all the equipment located within its area by using metallic cables or cables with both fibres and copper conductors. The numbers of equipment that can be supported in this way may be from two to several tens; each equipment has its own power supply. - - This Recommendation deals with the methods of
17、 the power feeding and back-up systems. iv ITU-T L.44 (10/2OOO) ITU-T Recommendation L.44 Electric power supply for equipment installed as outside plant 1 Introduction Some equipment (e.g. repeaters) needing a power supply had existed before optical fibres were installed. At that time, electrical po
18、wer had been mainly supplied from the central office by using a superimposition technique or by having insulated communication and power conductors in the same cable. After optical fibres were introduced, many kinds of optical/electrical equipment which require a power supply system were installed i
19、nto a telecommunication network, in order to increase capacity. The problem is that optical fibre cannot be used to directly transmit electrical power. Power is supplied by one of three ways: - to feed power from the central office by using metallic wires. To connect the power supply between the cen
20、tral office and the equipment, individual metallic cables or cables with both fibres and copper conductors may be used; to use a local power supply. In this method, one power supply provides power to all the equipment located within its area by using metallic cables or cables with both fibres and co
21、pper conductors. The numbers of equipment that can be supported in this way may be from two to several tens; each equipment has its own power supply. - - This Recommendation deals with the methods of the power feeding and back-up systems. 2 References The following ITU-T Recommendations and other re
22、ferences 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
23、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. i 2 ITU-T Recommendation K.50 (2000), Safe limits of operating voltages and currents for telecommunica
24、tion systems powered over the network. ITU-T Recommendation K.5 1 (2000), Safety criteriafor telecommunication equipment. 3 Power supply methods In order to select a power supply method, telecommunication companies should consider: 1) 2) 3) Based on the suitability of the electric power supplies in
25、each country, telecommunication companies should select a power supply method from the following. the outage rate of commercial power suppliers; the cost when using commercial power suppliers; the time to repair power source failure. ITU-T L.44 (10/2000) 1 3.1 Power supply from central office 3.1.1
26、Metallic transmission In case of transmission with copper conductors, the superimpose method may be used in order to feed the electrical power. The basic configuration of this method is shown in Figure 1. Communication signals and electrical power are combined and launched on the same conductors or
27、alternatively communication copper pairs and power copper wires (insulated conductors) are combined into one cable at the central office. The sent signal and power are divided at the electrical network unit (Em). Central office ELT I ENU YI I I Power Source I I I - T0604760-00 - Metallic cable ELT E
28、lectrical Line Terminal ENU Electrical Network Unit Figure UL.44 - Structure of power supply from central office (Metallic transmission) 3.1.2 Optical transmission When optical transmission is used, the basic structure of power supplies from the central office is shown in Figure 2. The power source
29、is located in the central office. Power is fed by power cables or composite cables (power conductors and optical fibres). This method allows telecommunication companies to control the quality of electrical power (that is, those technical issues covering the stability of the current, voltage and freq
30、uency, and the outage rate). However, the telecommunication companies then have the duty to operate and manage power networks. 2 ITU-T L.44 (10/2000) 1 ntral office c r- - -i vlyu I _- _- ONU Power Source I -_ ONU I Optical cable Power cable I I OLT Optical Line Terminal ONU Optical Network Unit a)
31、Individual cables for optical transmission and power feeding T0604770-00 Optical fibre - - - -. Power conductor OLT Optical Line Terminal ONU Optical Network Unit b) Power feeding through composite cable T0604780-00 Figure 2/L.44 - Structure of power supply from central office (Optical transmission)
32、 3.2 Local power supply 3.2.1 Metallic transmission This type of power supply is not usual. The principle of this method is shown in Figure 3. Communication signals and electric power are combined either by superimposition or on separate conductors in the same cable between the local station and the
33、 ENU. Power is fed into the cables at the local station. ITU-T L.44 (10/2000) 3 - ENU ENU Power Source ENU I Central office Local station - ELT Electrical Line Terminal ENU Electrical Network Unit Metallic cable (communication signal only) Metallic cable (communication signal and electrical power) I
34、 I T0604790-00 Figure 3/L.44 - Structure of local power supply (Metallic transmission) 3.2.2 Optical transmission Using optical transmission, the basic structure of local power supplies is shown in Figure 4. Power sources are set up near the ONU locations. Power can be supplied to several ONUs from
35、each power source. The number of ONUs which are covered by one power source is dependent upon supplied power from the power source, the power consumption of ONUs and the power losses in the power cables. Power is fed by power cables or composite cables (combined power and communication cables). To c
36、ontrol the local power supplies, monitoring systems or alarm systems are set up in the central office in order to obtain information about the condition of the power sources. Usually, the duty to operate and manage the power sources belongs to telecommunication company. However, when the power sourc
37、es are located in the customer premises, then customers may operate and manage the power sources themselves. The supply of electrical power from other customers power sources should be avoided. 4 ITU-T L.44 (10/2000) Optical cable Power cable - - - -. OLT Optical Line Terminal ONU Optical Network Un
38、it a) Individual cables for optical transmission and power feeding Power Source I T0604800-00 I Power I Optical fibre Power conductor OLT Optical Line Terminal ONU Optical Network Unit T0604810-00 b) Power feeding through composite cable Figure 4/L.44 - Structure of local power supply (Optical trans
39、mission) 3.3 Individual power supply 3.3.1 Metallic transmission In case of transmission with metallic wire, this type of power supply method would be used for digital or high speed transmission. The basic configuration of this method is shown in Figure 5. Electric power is fed to each ENU from each
40、 power source. Usually, the duty to operate and manage the power source belongs to the customers. ITU-T L.44 (10/2000) 5 Central office 271 - - - -q n I ENU t-I PS I - Metallic cable - - - -. Power cable ELT Electrical Line Terminal ENU Electrical Network Unit pS Power Source 7 ENU /-I PS I Figure 5
41、/L.44 - Individual power supply (Metallic transmission) 3.3.2 Optical transmission The basic configuration of this method is shown in Figure 6. Electrical power is fed to each Optical Network Unit (ONU) from each power source. Usually, the duty to operate and manage the power source belongs to the c
42、ustomers. 1 n OLT I ONU t-w I I - n Optical cable Power cable OLT Optical Line Terminal ONU Optical Network Unit pS Power Source yq - - - - 1-q T0604830-00 Figure 6/L.44 - Individual power supply (Optical transmission) 4 In order to select a power source for usual operation, the following should be
43、considered: - capacity; - stability of power feeding; - quality of electrical power; - operating cost. Power sources for usual operation 6 ITU-T L.44 (10/2000) 4.1 Power company Where the electrical power is supplied by a power company, a telecommunication company should condition the electrical pow
44、er in order for it to be suitable for the telecommunication equipment. When conditioning electrical power, a telecommunication company should consider the power quality supplied by a power company. Poor power quality may affect the quality of transmission or in the worst case damage telecommunicatio
45、n equipment. In order to design a backup system, a telecommunication company should know the outage rate of the power supply. NOTE - A separation (disconnection) point (e.g. switch) in the cabinets is provided in order to separate the competence of power and telecommunication companies as well as to
46、 allow safe maintenance of the telecommunication equipment. 4.2 Generator Where the electrical power is produced by a generator, a telecommunication company should condition the electrical power in order for it to be suitable for the telecommunication equipment. When conditioning electrical power, a
47、 telecommunication company should consider the power quality produced by a generator. Poor power quality may affect the quality of transmission, or may damage telecommunication equipment in the worst case. In order to design a backup system, a telecommunication company should know the failure rate (
48、such as MTBF) of the generator. 4.3 Battery When using batteries, a telecommunication company may condition the electrical power in order for it to be suitable for the telecommunication equipment. In this case, the capacity of a battery is most important. Use of a battery for equipment with high pow
49、er consumption should be carefully evaluated. 5 Power wiring In order to select power wiring, the following should be considered: 1) failure rate of the cable network (usually determined by failure caused by other 2) required power; 3) cable network environment; 4) safety issues for workers. contractors); 5.1 Individual power cable Where power is supplied by individual power cables, the construction cost will be higher because two different kinds of cable have to be installed. The two cables can be operated and managed separately. This allows any maintenanc
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