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详细说明：K.21 Version 201707, the newest K.21 specification.Recommendation itu-t K21
Resistibility of telecommunication equipment installed in
customer premises to overvoltages and overcurrents
Summary
Recommcndation ITU-T K 21 specifics resistibility rcquircmcnts and tcst proccdurcs for telecommunication
cquipment that is attached to or installed within a customcr's 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 due 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 conducted
by nearby conductors
Major changes compared with Recommendation ItU-TK 21(2008)include
updated references
added information on which universal scrial bus(USB)ports should bc tested
added information on when to add protection to untested ports
added test requirements for external coaxial cable ports
added test requirements for multiple conductor internal unshielded cable ports
Major changes compared with Recommendation ItU-TK21(201 1)include:
added test requirements for ethernet unshielded twisted pair (UTPe)
added test requirements for Ethernet shielded twisted pair(StPe)
added test requirements for power over Ethernet(Poe)
added STPe shield testing
History
Edition Recommendation Approval Study Group
Unique ID
1.0 ITU-TK21
1988-11-25
11.1002/1000/1390
2.0 TU-T K21
1996-10-18
11.1002/1000/3881
3.0 ITU-T K21
2000-10-06
11.1002/1000/5153
4.0 ITU-T K21
2003-07-29
11.1002/1000/6493
5.0 ITU-T K21
2008-04-13
55555555
11.1002/1000/940
6.0 ITU-T K21
2011-11-13
11.1002/1000/1142
7. 0 ITU-TK21
2015-04-22
11.1002/1000/12404
8.0 ITU-T K21
2016-06-29
11.1002/1000/12868
9. 0 ITU-TK21
2016-12-14
1002/1000/13127
10.0 ITU-T K.21201707-29
11.1002/1000/13273
Keywords
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)
ToacccsstheRecommendationtypctheUrlhttp://handlc.ituint/intheaddressficldofyourwcb
browserfollowedbytheRecommendationsuniqueId.Forexampleshttp://handle.itu.int/11.1002/1000/11
0
en
Rec, ITU-TK,21(07/2017
FOREWORD
The International Telecommunication Union (ITU) is the United Nations specialized agency in the ficld of
telecommunications, information and communication technologics(ICTs). The ITU Tclccommunication
Standardization Scctor(ITU-T)is a permancnt organ of ITU. ItU-T is responsible for studying technical
opcrating and tariff qucstions and issuing Recommendations on them with a vicw to standardizing
telecommunications on a worldwide basis
The World Tclccommunication Standardization Assembly (WTSA), which mccts cvcry four ycars, 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 I
In some areas of information technology which fall within ITU-T's 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 recommendation 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 arc mct The words"shall "or somc other
obligatory language such as"must"and thc negative equivalents arc used to express rcquircmcnts. Thc usc of
such words docs not suggest that compliance with the recommendation is rcquircd 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 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 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
patentdatabaseathttp://www.ituint/itu-t/Ipr/
CITU 2017
All rights rescrved. No part of this publication may be reproduced, by any mcans whatsoever, without the prior
written permission of ITU
Rec.rTU-TK.21(072017)
Table of contents
Page
References
Definitions
·…·······
3. 1 Terms defined elsewhere
3. 2 Terms defined in this recommendation
Abbreviations and acronyms
4.1
Symbols…
中····.··.4·
非和串
Conventions
■看
翻日D国春国
Tests
中“····中··中···
申·中·申·中中·中··申·申申
2
Bibliograph .
28
Ree.ITU-TK.21(07/2017)
Recommendation itu-t K21
Resistibility of telecommunication equipment installed in customer
premises to overvoltages and overcurrents
Scope
This recommendation specifies resistibility requirements and test procedures for telecommunication
cquipment that is attached to or installed within a customers' premises. The requirements of this
Recommendation assume that earthing and bonding is in accordance with [ITU-T K66]
The types of equipment covered by this recommendation include all types of telecommunication
equipment, e.g., modems, telephones, routers, implementations of 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 K66] and [b-ITU-TK.85] for methods of protection
This recommendation applies to both extemal and internal ports ITU-TK44 covering basic test
methods and test circuits, is an integral part of this recommendation. This Recommendation should
be read in conjunction with [iTu-TK. 11] and [iTU-TK39]
References
The following ITU-T Recommendations and other references contain provisions which through
refcrence 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
f 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 refcrence to a document within this
Recommendation does not give it. as a stand-alone document. the status of a recommendation
[ITU-TK11
Recommendation ITU-TK11(2009), Principles of protection against
overvoltages and overcurrents
[ITU-TK39 Recommendation ITU-TK39(1996), Risk assessment of damages to
telecommunication sites due to lightning discharges
ITU-TK 44
Recommendation ITU-TK 44(2017), Resistibility tests for telecommunication
equipment exposed to overvoltages and overcurrents- Basic Recommendation
IITU-TK66
Recommendation ITU-TK66(2011), Protection of customer premises from
overvoltages
[EC 61000-4-2] IEC 61000-4-2(2008), Electromagnetic compatibility(EMc)- Part 4-2
Testing and measurement techniques- Electrostatic discharge immunity test
Detinitions
3.1
Terms defined elsewhere
This recommendation uses terms defined in [ITU-T K44
3. 2 Terms defined in this recommendation
Ree.ITU-TK.21(07/2017)
Abbreviations and acronyms
This recommendation uses the following abbreviations and acronyms
a c
alternating current
CWG
Combination wave generator
d. c
direct
dpf
dedicated power feed
ESD
Electrostatic Discharge
n/a
not applicable
PE
Protective earth
POE
Power over ethernet
STP
Special Test Protector
STP
Ethernet shielded Twisted pair
USB
Universal scrial Bus
UTP
Ethernet unshielded Twisted pair ethernet
Symbols
This recommendation uses the following symbols
fire
equency
current
R
resistance
duration
alternating current voltage
a.c. (max)
maximum alternating current voltage
charging voltage
c(max)
maximum charging voltage
root mcan square voltage
maximum specific energy
Conventions
Conventions and symbols used in this recommendation are defined in [ITU-TK 44
Tests
A summary of the tests applicable to equipment installed in a customer's premises is given in table
The numbers given in the"Port type"columns, e.g., 2.2.1 a, 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 power- are given in Tables 2
to 5. The test conditions for electrostatic discharge(esd)are given in table 6. The test conditions
for intcrnal cable ports are given in Tablc 7. For information on the headings and tcrms used in the
tables, refer to clause 10 of[ITU-TK44
Refer to clause 5.2 of [ITU-T K 44] on selecting the enhanced resistibility requirement
Rec.rTU-TK.21(072017)
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 carth
NOTE 2-The external port test applies to ports used to connect extenally 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
Tb-ITU-TK.71], the internal port test can 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-TK.71]
noTE 4- Thc intcrnal port tests in Tablc 7 apply to ports connccted by short cables, c g. USB and printer
cables. Table 7 does not apply to ports connected infrequently, e. g. for maintenance ports
Table la- applicable tests for external ports
Port typ
No of pail
Primary
Test type simultancously
Dedicated
Mains
connections
protection
Symmetric
r fecd
po
Po
pe
DOR
ngle
Transverse
2.1.la
31.1411a
5.l.1a
voltage
differential
Port to carth
No
2.1.1b
4.1.1b
5.1.1b
N
1.Ic
4.1.1c
5.1.1
cxtcrnal port
Coordination/
2.1.2a
3.1.2
4.1.2a
5.1.2a
Transverse/
differential
Coordi
2.1.2b
n, a
1.21
Port to earth
Coordinati
Yes
2.1.2c
n/a
4.1.2
5.1
external port
Multiple
Port to earth
N
2.1.3a
n
n/a
n/a
N
2.1.3b
a
cxtcrnal port
Por
th
Ycs
n/a
n/a
Ye
n/a
n/a
sternal port
Ethernet
Port to carth
No
n, a
n/a
n/a
unshielded
Transver
0
n/a
n/a
n/a
twisted pair
(UTPE
0
2.1.10
nia
n/a
pulse test
Power
n/a
a
Ethernet(PoE)
Ethernet shielded Shield to earth
No
n/a
n/a
Port to
2.1.8
n/a
n/ a
(STPE)
Ree.ITU-TK.21(07/2017)
Table 1a- Applicable tests for external ports
Port type
No of pairs
Test
Prim
Test type simultancously
C
Dedicated Mains
connections protection
Symmetric
axial power feed powe
p
port
port
htning
Singlc
Port to carth
No
2.1.5a
n
4.1.5a
n/a
current
Port to
2.1.5b
4.1.5b
external port
Multiple
Port to carth
N
21.6a,2.1.10n/a
n/a
n/a
No
2.1.6b
n/a
n/a
external port
Differential
n/a
3.1.3
n/a
a
Shield to earth
n/a
3.14
n/a
n/a
Shield to
n/a
n/a
3.1.5
n/a
n/a
external port
Power
Single
Transverse
No
2.2.1a
Under
4.2.a
n'a
induction
study
and carth
Port to earth
No
2.2.1b
42.1b
5,2.1
potential
No
2.2.1c
n/a
4.2.lc
5.2.
cxtcrnal port
stud
Coordination
Ye
2.2.2
Under
4.2.2a
Transverse
study
Coordination
n/a
4.2.2b
n/a
Port to carth
Coordination
Ye
2.2.2c
n/a
4.2.2c
n/a
cxtcrnal port
Port to carth
No
n/a
a
n
5.2.2a
pe
No
/a
n/ a
n/a
5.2.2b
ternal port
Mains
Single
Transverse
No
2.3.la
n/a
4.3.la
n/a
Port to earth
N
2.3.1b
4.3.1b
n/a
contact
N
2.3.1
external port
4.3.lc
n/a
n/a: not applicable.
Rec.rTU-TK.21(072017)
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