1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU K.37 (02/99) SERIES K: PROTECTION AGAINST INTERFERENCE Low and high frequency EMC mitigation techniques for telecommunication installations and systems - Basic EMC Recommendation ITU-T Recommendation K.37 (Pr
2、eviously CClTT Recommendation) ITU-T K-SERIES RECOMMENDATIONS PROTECTION AGAINST INTERFERENCE For further details, please refer to ITU-T List of Recommendations. ITU-T RECOMMENDATION K.37 LOW AND HIGH FREQUENCY EMC MITIGATION TECHNIQUES FOR BASIC EMC RECOMMENDATION TELECOMMUNICATION INSTALLATIONS AN
3、D SYSTEMS - Summary This Recommendation defines mitigation techniques which the telecommunication operators may use to avoid disturbances, interference and damages caused by power and electrified railway plants, radio transmitters, both intentional and unintentional, and electrostatic discharges. Th
4、is Recommendation contains guidance for the telecommunications system normal operation: - use of telecommunications equipment fulfilling relevant EMC requirements; - proper installation practices such as well-controlled earthing and bonding networks and a.c. power distribution networks in buildings,
5、 avoidance of disturbing equipment close to telecommunications equipment, environmental control and well-designed cabling; telecommunications equipment and applying special precautions when handling electrostatic discharge sensitive devices; - proper working practices such as avoiding use of hand-he
6、ld radios close to - proper working practices in areas subject to high levels of low-frequency induction. Special mitigation methods like shielding and filtering are discussed for cases where EMC problems arise. This Recommendation does not include circuit or equipment design rules or guidelines for
7、 manufacturing - it is noted that this information is already widely available. Source ITU-T Recommendation K.37 was revised by ITU-T Study Group 5 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 26h of February 1999. Recommendation K.37 (02/99) 1 STD-ITU-T RECMN K-37-E
8、NGL 1999 4862591 0657358 848 D FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical,
9、operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in t
10、heir turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collabor
11、ative basis with IS0 and IEC. NOTE In this Recommendation the term recognized operating agency (ROA) includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms Administration, ROA and public correspondence are defined in the Co
12、nstitution of the ITU (Geneva, 1992). INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applic
13、ability 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, the ITU had not received notice of intellectual property, protected by patents, which may be required to im
14、plement 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 1999 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any mea
15、ns, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Il Recommendation K.37 (02/99) CONTENTS Page 1 S cope 2 References 3 Definitions 4 5 High frequency EMC . Low frequency EMC 6 Equipment specifications 7 Environment . 7.1 Distance to inter
16、ference sources . 7.2 Distance to radio transmitters . 7.3 Earthing and bonding network . 7.4 a.c. power network and electrical equipment . 7.5 Materials and humidity . 8 Installation 8.1 Equipment . 8.2 Cabling 8.3 Connectors 9 Working methods . 9.1 Restrictions to use disturbing equipment . 9.2 Av
17、oiding ESD in maintenance and repair 1 O Special mitigation measures . 1 O . 1 Screening 1 O . 1 . 1 Screening (high frequency) . 1 O . 1.2 Screening (low frequency) 1 0.2 Filtering . 10.2.1 Filtering (high frequency) . 1 0.2.2 Filtering (low frequency) 10.3 Common mode chokers 10.3.1 Common mode ch
18、okes (high frequency) 10.3.2 Common mode chokes (low frequency) . 10.4 Drainage coils (low frequency) 10.5 Active filters (low frequency) . 10.6 Neutralizing transformers (low frequency) 1 1 2 2 2 3 3 3 3 3 4 4 6 6 6 6 6 6 7 8 8 8 . Recommendation K.37 (02199) 111 10.7 Hybrid solutions (low frequenc
19、y) . 10.8 Isolation transfomers (high and low frequency) . 10.9 Optical components (high and low frequency) . 1 O . 1 O Capacitors (high frequency) . Appendix I - Troubleshooting and fixing high fiequency EMC problems . I . 1 Introduction I . 2 Source verification 1.3 Check-list for problem solution
20、 1.4 Bibliography . Appendix II - Troubleshooting and fixing low frequency EMC problems . 11.1 Introduction 11.2 Source verification 11.3 Check-list for problem solution Page 9 9 9 9 10 10 10 10 11 11 11 11 12 1 iv Recommendation K.37 (02/99) Introduction This Recommendation contains guidance for te
21、lecommunication operators on avoiding interference and damage caused by power and electrified railway plants, radio transmitters, both intentional and unintentional, and electrostatic discharges. The text is intentionally short, drawing the attention of the user to reference standards and documents
22、listed. Equipment, when used in an environment where it is intended to be installed, should be able to function properly and without disturbing other equipment. This is assured by environmental classification and EMC test requirements. Telecommunications equipment normally fulfils the EMC requiremen
23、ts when the doors of cabinets are closed and other covers are on. During installation and maintenance it is necessary to open the doors which require special precautions when handling Electrostatic Discharges (ESD) sensitive devices. Hand-held radios may also cause interference in such situations. M
24、itigation methods are also given for cases where interference exists due to fast transient or radio-frequency phenomena for some reason - e.g. the environment is harder than the class the equipment is designed for - or other power users are creating a harsh environment. Practical rules are given for
25、 situations where interference occurs, e.g. due to low frequency harmonic disturbance from an a.c. power system or user. This Recommendation is a basic EMC Recommendation for telecommunications. Recommendation K.37 (02/99) V STDnITU-T RECMN K-37-ENGL 1999 Recommendation K.37 LOW AND HIGH FREQUENCY E
26、MC MITIGATION TECHNIQUES FOR BASIC EMC RECOMMENDATION (revised in 1999) TELECOMMUNICATION INSTALLATIONS AND SYSTEMS - 1 Scope This Recommendation explains both low and high frequency EMC mitigation techniques in order to avoid disturbances and interference caused by low and high frequency interferen
27、ce and fast transient phenomena. This Recommendation applies to installation and maintenance of the telecommunications network. This Recommendation does not apply to protective measures due to dangerous levels of power noise. This Recommendation does not apply to Co-axial cables (i.e. no differentia
28、l mode). 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 t
29、o revision; all 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. ITU-T Recommendation K.34 (1
30、996), ClassiJication of electromagnetic environmental conditions for telecommunications equipment - Fast transient and radio JFequency phenomena. ITU-T Recommendation K.32 (1995), Immunity requirements and test methods for electrostatic discharge to telecommunication equipment - Generic EMC Recommen
31、dation. CCITT Recommendation K. 15 (1972), Protection of remote-feeding systems and line repeaters against lightning and interference $-om neighbouring electricity lines. CISPR 22, Limits and methods of measurement of radio disturbance characteristics of information technology equipment. ITU-T Recom
32、mendation K.27 (1996), Bonding configurations und earthing. inside a telecommunication building. ITU-T Recommendation K.3 1 (1993), Bonding conJgurations and earthing of telecommunication installations inside a subscriber S building. ITU-T Recommendation K.35 (1996), Bonding confzgurations and earth
33、ing at remote electronic sites. IEC 61000-5-2 (1997), Electromagnetic Compatibility (EMC) - Part 5: Installation and mitigation guidelines - Section 2: Earthing and cabling. ETSI Technical Report ETR 127 (1 994), Equipment Engineering (EE); Electrostatic environment and mitigution measures for Publi
34、c Telecommunications Network (PTN). Recommendation K.37 (02/99) 1 1 O ITU-T Recommendation K. 10 (1 996), Low fiequency interference due to unbuZance about earth of telecornmunication equipment. C1 13 IEC 60096-1 (1986), Radio-Pequency cables. Part I: General requirements and measuring methods. C121
35、 ETSI Technical Report ETR 151 (1995), Equipment Engineering (E; ElectroMagnetic Compatibility (EMC) testing of telecommunication equipment above I GHz. 131 IEC 60050- 16 1 (1 990), International Electrotechnical Vocabulary. Chapter 161: Electromagnetic compatibility. 3 Definitions The definitions o
36、f IEC 60050-1 61 apply: ISDN Integrated Services Digital Network PSTN Public Switched Telephone Network xDSL Digital Subscriber Loop x = A Asymmetric V Very High Speed 4 High frequency EMC High frequency EMC in telecommunications includes control of both emission and immunity in telecommunication eq
37、uipment and installations. High frequency emission is mainly caused by harmonics of clock frequencies of digital circuits which propagate by conduction or radiation. Spurious emissions from radio equipment can also be considered to belong under EMC. Emission control is performed by equipment design
38、and correct installation. Immunity problems may be caused by such high frequency and fast transient phenomena as radio-frequency fields of different radio systems, radio-frequency currents induced to telecommunication and power lines, fast transients caused by switches in equipment connected to main
39、s or d.c. power and discharges of the static electricity. Immunity is controlled by designing equipment to meet standardized test requirements, by network design, proper installation, environmental control and maintenance and correct working methods. 5 Low frequency EMC Low frequency EMC in telecomm
40、unications includes control of both emission and immunity in telecommunication equipment and installations. Low frequency emission by telecommunication equipment and systems is not normally a problem and will not be considered in this Recommendation. When problems do occur they are normally symptoma
41、tic of a greater problem. Immunity problems may be caused by low frequency phenomena such as a.c. power distribution systems, electrified railways, electrified fences (e.g. for animal containment), welding equipment and other high-power industrial systems causing induction to telecommunication lines
42、. Some industrial systems also cause fast transient impulses to be induced onto the telecommunications system. LF 2 Recommendation K.37 (02/99) STD-ITU-T RECMN K-37-ENGL 3997 m 48b2593 Ob573b4 041 D interference is generally coupled into system cables serving the equipment. Whilst the majority of LF
43、 noise problems are conductive or inductive, there are instances of coupling by radiation Immunity is initially controlled by designing equipment to meet standardized test requirements, by network design, proper installation, environmental control, and maintenance and correct working methods. The co
44、ntrol of such emissions is the responsibility of the interferer, and in some instances a national authority. Generally, it is always most cost-effective for all parties concerned to solve the problem at source. In some instances, it may not be economical to design equipment to meet all circumstances
45、 and, as such, external mitigation techniques have to be used. 6 Equipment specifications The equipment shall be able to work without EMC problems in the environment where it is intended to be installed. For this reason the electromagnetic environment of telecommunications equipment has been classif
46、ied in to four classes l. This classification has been used in specifying test requirements for different telecommunications equipment 2 and 3. Emission requirements shall also be specified 4. The operator should specify the requirements by reference to the relevant ITU-T Recommendation or correspon
47、ding document and either check with the manufacturer or test himself that the equipment flfils the requirements. When considering low frequency aspects, the equipment shall generally be able to work without LF interference problems in the environment where it is intended to be installed (e.g. 200 mV
48、 common mode, psophometric noise should not cause a problem for voice circuits as per Recommendation K. 1 O). Recommendation K.34 11 defines the various classes of electromagnetic environment of telecommunications equipment. It is acknowledged that there will be circumstances when the interference l
49、evels are high enough to cause interference problems without resorting to uneconomical equipment designs for either party. This is generally a low fiequency interference problem, and other measures need to be considered in these circumstances. 7 Environment 7.1 Distance to interference sources It is not always practical to position telecommunication systems away from low frequency interference sources; in fact, the interferer may arrive at a later date and have an influence over a distance of a few kilometres. If no standard or Recommendation is being applied to the problem
