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.75 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2016) SERIES K: PROTECTION AGAINST INTERFERENCE Classification of interface for application of standards on resistibility and safety of telecommunication equipment Re
2、commendation ITU-T K.75 Rec. ITU-T K.75 (06/2016) i Recommendation ITU-T K.75 Classification of interface for application of standards on resistibility and safety of telecommunication equipment Summary Recommendation ITU-T K.75 provides guidance to manufacturers, network operators and test houses on
3、 the classification of the type of interface, i.e., external subject to alternating current (a.c.) surges or conducted lightning surges or internal (subject to short fall-time transients induced in building cabling). This Recommendation defines telecommunication overvoltage categories as a function
4、of the inherent resistibility voltage of the equipment port or interface. For each category, the impulse withstand voltages between the telecommunication interface and the person or hazardous circuit have been defined (peak value and waveshape). These peak values and waveshapes should be suitable fo
5、r insulation coordination purposes. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T K.75 2008-04-13 5 11.1002/1000/9412 2.0 ITU-T K.75 2016-06-29 5 11.1002/1000/12875 Keywords Classification, overvoltage, safety, telecommunication, transient, resistibility. * To access the R
6、ecommendation, 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.75 (06/2016) FOREWORD The International Telecommunication Union (ITU) is the United Nations
7、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 Recommendations on t
8、hem 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 approval of ITU
9、-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“ is use
10、d 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
11、 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 required of
12、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 Intellectual Prop
13、erty 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, im
14、plementers 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 2016 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior wri
15、tten permission of ITU. Rec. ITU-T K.75 (06/2016) iii Table of 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 3 5 Conventions 3 6 Classification of interfaces . 3 6.1 Type of interface
16、 . 3 6.2 Specifying the transient 5 7 Application of overvoltage categories 5 Annex A Classifying external and internal interfaces 9 Appendix I Overvoltages on telecommunication network . 10 I.1 General . 10 I.2 Protection and risk assessment . 10 I.3 Telecommunication overvoltage categories . 11 I.
17、4 Causes of overvoltage . 12 Bibliography. 14 Rec. ITU-T K.75 (06/2016) 1 Recommendation ITU-T K.75 Classification of interface for application of standards on resistibility and safety of telecommunication equipment 1 Scope The purpose of this Recommendation is to provide: guidance to manufacturers,
18、 network operators and test houses on the classification of the type of interface, i.e., external subject to alternating current (a.c.) surges or conducted lightning surges or internal (subject to short fall-time transients induced in building cabling); information on the waveform of transients appe
19、aring at equipment interfaces for insulation coordination purposes. This Recommendation mainly applies to customer equipment due to safety being achieved in other ways for network equipment, e.g., earthing or powering from a safe supply, such as a supply voltage equal to or less than 60 V direct cur
20、rent (d.c.). NOTE 60 V d.c. is a class 1 energy source (ES1) voltage. However, the waveform of transients appearing at equipment interfaces is also provided for telecommunication centres and access network sites, in case it is needed in the future. This Recommendation assumes that the telecommunicat
21、ion equipment is either mains powered or powered from the telecommunication network, and is installed according to the earthing and bonding requirements relevant to each different environment (i.e., ITU-T K.27, ITU-T K.35 and ITU-T K.66). This Recommendation does not provide safety or resistibility
22、requirements such as test procedures and test criteria. This Recommendation does not describe mitigation measures or the various approaches used to determine the need to provide additional protection external to the equipment (primary protection). This Recommendation does not address overvoltages ca
23、used by power contact with low-voltage or medium-voltage power lines. 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
24、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 Recommendations and other references listed below. A list of the currently valid ITU-T Recommendati
25、ons 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.20 Recommendation ITU-T K.20 (2016), Resistibility of telecommunication equipment installed in a telecommunications centre to overvo
26、ltages and overcurrents. ITU-T K.21 Recommendation ITU-T K.21 (2016), Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents. ITU-T K.27 Recommendation ITU-T K.27 (2015), Bonding configurations and earthing inside a telecommunication building. 2
27、Rec. ITU-T K.75 (06/2016) ITU-T K.35 Recommendation ITU-T K.35 (1996), Bonding configurations and earthing at remote electronic sites. ITU-T K.45 Recommendation ITU-T K.45 (2016), Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages and overcurrents
28、. ITU-T K.66 Recommendation ITU-T K.66 (2011), Protection of customer premises from overvoltages. ITU-T K.67 Recommendation ITU-T K.67 (2015), Expected surges on telecommunications and signalling networks due to lightning. IEC 60664-1 IEC 60664-1 (2007), Insulation coordination for equipment within
29、low-voltage systems Part 1: Principles, requirements and tests. IEC 60950-1 IEC 60950-1 (2005) + AMD1 (2009) + AMD2 (2013), Information technology equipment Safety Part 1: General requirements. IEC 62305-2 IEC 62305-2 (2010), Protection against lightning Part 2: Risk management. 3 Definitions 3.1 Te
30、rms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 basic insulation IEC 60950-1: Insulation to provide basic protection against electric shock. 3.1.2 double insulation IEC 60950-1: Insulation comprising both basic insulation and supplementary insulation. 3.1.
31、3 equipotential bonding b-IEC 60050-826): Electrical connection putting various exposed conductive parts and extraneous conductive parts at a substantially equal potential. 3.1.4 reinforced insulation IEC 60950-1: Single insulation system that provides a degree of protection against electric shock e
32、quivalent to double insulation under the conditions specified in IEC 60950-1. 3.1.5 supplementary insulation b-IEC 62368-1: Independent insulation applied in addition to basic insulation to provide a supplementary safeguard for fault protection against electric shock. 3.2 Terms defined in this Recom
33、mendation This Recommendation defines the following terms: 3.2.1 circuit isolation voltage: Highest value of a specified overvoltage that does not cause breakdown of insulation or other safeguards between a telecommunication line and another circuit within the equipment. 3.2.2 external circuit: Circ
34、uit that is, in whole or in part, external to the equipment and is neither a mains nor a d.c. power distribution system. NOTE This definition is different to the ITU-T SG 5 definition in the context of external interfaces. 3.2.3 external interface: Any port on the equipment that may be subject to a.
35、c. surges and conducted lightning surges. 3.2.4 internal interface: Any port on the equipment which is only ever exposed to short duration induced transients. Rec. ITU-T K.75 (06/2016) 3 3.2.5 person isolation voltage: Highest value of a specified overvoltage that does not cause breakdown of insulat
36、ion between a telecommunication line and a person in contact with the equipment. 3.2.6 telecommunication overvoltage category: A designation defining a transient overvoltage condition. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: a.c. alternating cu
37、rrent d.c. direct current ES1 Energy Source - class 1 EPR Earth Potential Rise EUT Equipment Under Test GDT Gas Discharge Tube L Line MDF Main Distribution Frame MET Main Earth Terminal N Neutral PC Personal Computer PE Protective Earth POTS Plain Old Telephone Service rms root mean square SPD Surge
38、 Protective Device USB Universal Serial Bus VDSL Very high-speed Digital Subscriber Line VTU-O Very high speed digital subscriber line Transceiver Unit, Operator end VTU-R Very high speed digital subscriber line Transceiver Unit, Remote end 5 Conventions None. 6 Classification of interfaces Two thin
39、gs are needed to classify an interface. Firstly, an interface has to be classified as either “internal“ or “external“. Secondly, it is necessary to define the interface in terms of the magnitude of the likely transient. 6.1 Type of interface An interface is classified by determining the types of ove
40、rvoltages that the interface is exposed to. If the interface is exposed to a.c. surges or to lightning surges conducted by an outdoor or external cable, it is an external interface. 4 Rec. ITU-T K.75 (06/2016) If it is only exposed to short transients, due to induction in building wiring, it can be
41、classified as an internal interface. Figure 1 shows a reference configuration for the telecommunication lines with metallic symmetric conductors where the reference nodes (IEC 62305-2 uses the term “transition points“) and the cable sections between them can be seen. Table 1 defines the various node
42、s in Figure 1. Figure 1 can be used to identify parts of the telecommunication network to be classified as either “internal“ or “external“: a) External conductors External or outdoor conductors, subject to power induction and lightning-caused overvoltages, are conductors between nodes ES, ER, RS, SS
43、 shown in Figure 1 (see also Appendix I). b) Internal conductors Internal or intra-building or indoor conductors, not subject to the electromagnetic interference due to power systems, are conductors between nodes II and MM shown in Figure 1 (see also Appendix I). A detailed method for classifying in
44、terfaces is given in Annex A. Figure 1 Reference configuration of telecommunication and signal lines Rec. ITU-T K.75 (06/2016) 5 Table 1 Description of nodes Node Description L Transition between equipment interface inside the exchange building and the external cabling. E Entrance of the exchange bu
45、ilding, e.g., main distribution frame (MDF). R Transition between line and equipment inside a remote site. S Entrance of the customers building. A Transition between equipment interface inside the customers building and the external cabling. M Transition between equipment interface inside the exchan
46、ges building and the internal cabling. I Transition between equipment interface inside the customers building and the internal cabling. 6.2 Specifying the transient This Recommendation adopts an approach suggested by IEC 60664-1 by specifying “telecommunications overvoltage categories“. Table 2 show
47、s the overvoltage categories and overvoltage transient on mains according to IEC 60664-1. Table 2 Mains overvoltage categories and overvoltage transient on mains interfaces, according to IEC 60664-1 Mains overvoltage categories Lightning impulse transient (1.2/50 s) IV 6 000 V III 2 500 V II 2 500 V
48、 I 1 500 V Each overvoltage category relates to a set of network design and protection practices that correspond to a particular resistibility level of the equipment in terms of transient overvoltages. The relevant values of the impulse overvoltage at the equipment input, taking into account the dif
49、ferent installation environments, are specified in: ITU-T K.20 for the exchange environment; ITU-T K.45 for the access network environment; and ITU-T K.21 for the customers environment. The inherent equipment impulse resistibility requirements, based on the data in these Recommendations, are used in Tables 3 and 4 to define the telecommunication overvoltage categories for telecommunication circuits. 7 Application of overvoltage categories Three types of insulation are generally use
