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.21 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2017) SERIES K: PROTECTION AGAINST INTERFERENCE Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents Recommend
2、ation ITU-T K.21 Rec. ITU-T K.21 (07/2017) i Recommendation ITU-T K.21 Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents Summary Recommendation ITU-T K.21 specifies resistibility requirements and test procedures for telecommunication equipme
3、nt that is attached to or installed within a customers premises. Overvoltages or overcurrents covered by this Recommendation include surges due to lightning on or near the line plant, short-term induction from adjacent alternating current (a.c.) power lines or railway systems, earth potential rise d
4、ue to power faults, direct contact between telecommunication lines and power lines, and electrostatic discharges (ESDs). The sources for overvoltages in internal lines are mainly inductive coupling caused by lightning currents being conducted in nearby lightning strikes or lightning currents being c
5、onducted by nearby conductors. Major changes compared with Recommendation ITU-T K.21 (2008) include: updated references; added information on which universal serial bus (USB) ports should be tested; added information on when to add protection to untested ports; added test requirements for external c
6、oaxial cable ports; added test requirements for multiple conductor internal unshielded cable ports. Major changes compared with Recommendation ITU-T K.21 (2011) include: added test requirements for Ethernet unshielded twisted pair (UTPE); added test requirements for Ethernet shielded twisted pair (S
7、TPE); added test requirements for power over Ethernet (PoE); added STPE shield testing. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T K.21 1988-11-25 11.1002/1000/1390 2.0 ITU-T K.21 1996-10-18 5 11.1002/1000/3881 3.0 ITU-T K.21 2000-10-06 5 11.1002/1000/5153 4.0 ITU-T K.2
8、1 2003-07-29 5 11.1002/1000/6493 5.0 ITU-T K.21 2008-04-13 5 11.1002/1000/9401 6.0 ITU-T K.21 2011-11-13 5 11.1002/1000/11421 7.0 ITU-T K.21 2015-04-22 5 11.1002/1000/12404 8.0 ITU-T K.21 2016-06-29 5 11.1002/1000/12868 9.0 ITU-T K.21 2016-12-14 5 11.1002/1000/13127 10.0 ITU-T K.21 2017-07-29 5 11.1
9、002/1000/13273 Keywords 1.2/50-8/20, 10/700, customer premises equipment, Ethernet, external port, internal port, overvoltage, overcurrent, power over Ethernet (PoE), power contact, power induction, resistibility, surges, telecommunication equipment, transverse, universal serial bus (USB). * To acce
10、ss the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T K.21 (07/2017) FOREWORD The International Telecommunication Union (ITU) is the United
11、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 Recommendati
12、ons 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 approva
13、l 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 “Administration
14、“ 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
15、with 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 requ
16、ired of any party. INTELLECTUAL PROPERTY RIGHTSITU 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
17、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
18、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 2017 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the p
19、rior written permission of ITU. Rec. ITU-T K.21 (07/2017) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 1 4 Abbreviations and acronyms 2 4.1 Symbols 2 5 Conventions 2 6 Tests 2 Bibliography. 28 Rec. IT
20、U-T K.21 (07/2017) 1 Recommendation ITU-T K.21 Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents 1 Scope This Recommendation specifies resistibility requirements and test procedures for telecommunication equipment that is attached to or inst
21、alled within a customers premises. The requirements of this Recommendation assume that earthing and bonding is in accordance with ITU-T K.66. The types of equipment covered by this Recommendation include all types of telecommunication equipment, e.g., modems, telephones, routers, implementations of
22、digital subscriber lines and personal computers. NOTE Associated equipment containing ports with a low surge impedance to earth connected by short cables, e.g., printers using universal serial bus (USB) cables, may be susceptible to damage due to circulating earth currents. Refer to ITU-T K.66 and b
23、-ITU-T K.85 for methods of protection. This Recommendation applies to both external and internal ports. ITU-T K.44, covering basic test methods and test circuits, is an integral part of this Recommendation. This Recommendation should be read in conjunction with ITU-T K.11 and ITU-T K.39. 2 Reference
24、s 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 to revision; users of
25、 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. The reference to a document within this Recommendatio
26、n does not give it, as a stand-alone document, the status of a Recommendation. ITU-T K.11 Recommendation ITU-T K.11 (2009), Principles of protection against overvoltages and overcurrents. ITU-T K.39 Recommendation ITU-T K.39 (1996), Risk assessment of damages to telecommunication sites due to lightn
27、ing discharges. ITU-T K.44 Recommendation ITU-T K.44 (2017), Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents Basic Recommendation. ITU-T K.66 Recommendation ITU-T K.66 (2011), Protection of customer premises from overvoltages. IEC 61000-4-2 IEC 61000-4-2
28、(2008), Electromagnetic compatibility (EMC) Part 4-2: Testing and measurement techniques Electrostatic discharge immunity test. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses terms defined in ITU-T K.44. 3.2 Terms defined in this Recommendation None. 2 Rec. ITU-T K.21 (07/2017) 4
29、 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: a.c. alternating current CWG Combination Wave Generator d.c. direct current dpf dedicated power feed ESD Electrostatic Discharge n/a not applicable PE Protective Earth PoE Power over Ethernet STP Special T
30、est Protector STPE Ethernet Shielded Twisted Pair USB Universal Serial Bus UTPE Ethernet Unshielded Twisted Pair Ethernet 4.1 Symbols This Recommendation uses the following symbols: f frequency I current R resistance t duration Ua.c. alternating current voltage Ua.c.(max) maximum alternating current
31、 voltage Uc charging voltage Uc(max) maximum charging voltage Urms root mean square voltage Wsp(max) maximum specific energy 5 Conventions Conventions and symbols used in this Recommendation are defined in ITU-T K.44. 6 Tests A summary of the tests applicable to equipment installed in a customers pr
32、emises is given in Table 1. The numbers given in the “Port type“ columns, e.g., 2.2.1a, refer to the “Test No.“ of Tables 2 to 5. The words “under study“ mean that ITU-T is still studying this test. The test conditions applicable to the four ports symmetric, coaxial, dedicated power feed and mains p
33、ower are given in Tables 2 to 5. The test conditions for electrostatic discharge (ESD) are given in Table 6. The test conditions for internal cable ports are given in Table 7. For information on the headings and terms used in the tables, refer to clause 10 of ITU-T K.44. Refer to clause 5.2 of ITU-T
34、 K.44 on selecting the enhanced resistibility requirement. Rec. ITU-T K.21 (07/2017) 3 NOTE 1 The port to external port test for the basic test level does not apply when the equipment is designed to always be used with a connection to earth. NOTE 2 The external port test applies to ports used to con
35、nect externally attached equipment to equipment installed within the same building. The mains power contact test does not apply in this situation. Where the equipment external to the building is installed in the “inherently protected“ area shown in Figure 3 of b-ITU-T K.71, the internal port test ca
36、n be applied. NOTE 3 The power induction test does not apply to ports used to connect to antennas installed within the scope of b-ITU-T K.71. NOTE 4 The internal port tests in Table 7 apply to ports connected by short cables, e.g., USB and printer cables. Table 7 does not apply to ports connected in
37、frequently, e.g., for maintenance ports. Table 1a Applicable tests for external ports Test type No. of pairs simultaneously tested Test connections Primary protection Port type Symmetric port Co-axial port Dedicated power feed port Mains power port Lightning/ voltage Single Transverse/ differential
38、No 2.1.1a 3.1.1 4.1.1a 5.1.1a Port to earth No 2.1.1b n/a 4.1.1b 5.1.1b Port to external port No 2.1.1c n/a 4.1.1c 5.1.1c Coordination/Transverse/ differential Yes 2.1.2a 3.1.2 4.1.2a 5.1.2a Coordination/Port to earth Yes 2.1.2b n/a 4.1.2b 5.1.2b Coordination/Port to external port Yes 2.1.2c n/a 4.1
39、.2c 5.1.2c Multiple Port to earth No 2.1.3a n/a n/a n/a Port to external port No 2.1.3b n/a n/a n/a Port to earth Yes 2.1.4a n/a n/a n/a Port to external port Yes 2.1.4b n/a n/a n/a Ethernet unshielded twisted pair (UTPE) Port to earth No 2.1.8 n/a n/a n/a Transverse No 2.1.7 n/a n/a n/a Voltage imp
40、ulse test No 2.1.10 n/a n/a n/a Power over Ethernet (PoE) No 2.1.11 n/a n/a n/a Ethernet shielded twisted pair (STPE) Shield to earth No 2.1.9 n/a n/a Port to earth No 2.1.8 n/a n/a 4 Rec. ITU-T K.21 (07/2017) Table 1a Applicable tests for external ports Test type No. of pairs simultaneously tested
41、Test connections Primary protection Port type Symmetric port Co-axial port Dedicated power feed port Mains power port Lightning current Single Port to earth No 2.1.5a n/a 4.1.5a n/a Port to external port No 2.1.5b n/a 4.1.5b n/a Multiple Port to earth No 2.1.6a, 2.1.10 n/a n/a n/a Port to external p
42、ort No 2.1.6b n/a n/a n/a Differential n/a n/a 3.1.3 n/a n/a Shield to earth n/a n/a 3.1.4 n/a n/a Shield to external port n/a n/a 3.1.5 n/a n/a Power induction and earth potential rise Single Transverse No 2.2.1a Understudy 4.2.1a n/a Port to earth No 2.2.1b n/a 4.2.1b 5.2.1 under study Port to ext
43、ernal port No 2.2.1c n/a 4.2.1c 5.2.1 under study Coordination Transverse Yes 2.2.2a Understudy 4.2.2a n/a Coordination Port to earth Yes 2.2.2b n/a 4.2.2b n/a Coordination Port to external port Yes 2.2.2c n/a 4.2.2c n/a Neutral potential rise Single Port to earth No n/a n/a n/a 5.2.2a Port to exter
44、nal port No n/a n/a n/a 5.2.2b Mains power contact Single Transverse No 2.3.1a n/a 4.3.1a n/a Port to earth No 2.3.1b n/a 4.3.1b n/a Port to external port No 2.3.1c n/a 4.3.1c n/a n/a: not applicable. Rec. ITU-T K.21 (07/2017) 5 Table 1b Lightning test conditions for ports connected to internal cabl
45、es No. of pairs simultaneously tested Test connection Primary protection Unshielded cable Shielded cable PoE feed Floating DC powering Earthed DC powering Single Shielded cable to earth No 7.2 USB shielded cable to earth No 7.3 STPE simultaneous port to earth No 7.4 UTPE/STPE transverse No 7.7 7.7 E
46、arthed direct current (d.c.) power interface No 7.9 Multiple Unshielded cable with symmetric pairs No 7.1 PoE Mode A and Mode B transverse testing No 7.5 UTPE port rated impulse voltage No 7.6 Floating d.c. power interface No 7.8 6 Rec. ITU-T K.21 (07/2017) Table 2a Lightning test conditions for por
47、ts connected to external symmetric pair cables Test No. Test description Test circuit and waveform (see figures in Annex A of ITU-T K.44) Basic test levels (also see clause 7 of ITU-T K.44) Enhanced test levels (also see clauses 5 and 7 of ITU-T K.44) Number of tests Primary protection (see clause 8
48、 of ITU-T K.44) Acceptance criteria (see clause 9 of ITU-T K.44) Comments 2.1.1a Single pair, lightning, inherent, transverse A.3-1 and A.6.1-1 (a and b) 10/700 Uc(max) = 1.5 kV R = 25 Uc(max) = 1.5 kV R = 25 Alternating 5 surges (60 s between successive surges) None A Test 2.1.1 does not apply when
49、 the equipment is designed to always be used with primary protection and the operator agrees. If this test is not performed, the appropriate test from Table 7 applies. If the inherent protection of the port under test contains surge protective devices (SPDs) that are connected to a protective earth (PE), a Uc(max) of 1.5 kV shall be used instead of 6 kV. If the equipment has an insulated case, the 6 kV test is applied with the equipment wrapped in conductive foil and t
