1、 International Telecommunication Union ITU-T K.75TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (04/2008) SERIES K: PROTECTION AGAINST INTERFERENCE Classification of interface for application of standards on resistibility and safety of telecommunication equipment Recommendation ITU-T K.75 Rec. ITU-
2、T K.75 (04/2008) 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 the classification of the type o
3、f interface, i.e., external (subjected to a.c. surges or conducted lightning surges) or internal (subjected to short fall-time transients induced into building cabling). This Recommendation defines telecommunication overvoltage categories as a function of the inherent resistibility voltage of the eq
4、uipment 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 for insulation coordination purposes. Source Reco
5、mmendation ITU-T K.75 was approved on 13 April 2008 by ITU-T Study Group 5 (2005-2008) under Recommendation ITU-T A.8 procedure. Keywords Equipment interface, equipment port, external circuit, external port, impulse withstand voltage, injury to people, internal port, intra-building or indoor conduct
6、or, outdoor conductor, resistibility, safety, telecommunication overvoltage category. ii Rec. ITU-T K.75 (04/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs).
7、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 telecommunications on a worldwide basis. The World Telecommunication Stan
8、dardization 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 procedure laid down in WTSA Resolution 1. In some areas of informatio
9、n 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 used for conciseness to indicate both a telecommunication administration and a recognized operating agency. C
10、ompliance 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 are met. The words “shall“ or some other
11、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 any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implemen
12、tation 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. A
13、s 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 urge
14、d to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2009 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T K.75 (04/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions
15、 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. 3 6.2 Defining the transient . 4 7 Application of overvoltage categories 5 Annex A Classifying external and internal i
16、nterfaces 8 Appendix I Overvoltages on telecommunication network . 9 I.1 General . 9 I.2 Protection and risk assessment . 9 I.3 Telecommunication overvoltage categories. 10 I.4 Causes of overvoltage. 11 Bibliography. 13 iv Rec. ITU-T K.75 (04/2008) Introduction IEC TC 108 has traditionally used 1.5
17、kV as the maximum magnitude of transients occurring at equipment interfaces connected to network, or inter-building, cables, and 800 V as the maximum magnitude of transients occurring at the equipment interfaces connected to intra-building cables. ITU-T Study Group 5 (SG 5) introduced “enhanced“ req
18、uirements into Recommendations ITU-T K.20, K.21 and K.45 in the year 2000. There is now a range of resistibility levels for interfaces connected to inter- and intra-building cables. These enhanced requirements were introduced as a result of field failures and to enable an improvement in equipment re
19、liability. SG 5 also recognizes that it is sometimes difficult, expensive or impossible to correctly install primary protection on telecommunication lines. This can be due to old buildings being difficult to retrofit primary protection or for regulatory reasons. With the introduction of equipment in
20、stalled in customer premises deriving copper services, it is necessary to have clear guidelines on when to classify an interface as either “external“ (subjected to a.c. transients and conducted lightning surges) or “internal“ (subjected to transients induced into intra-building cables). The purpose
21、of this Recommendation is to: 1) achieve coordination of the test voltages used for safety testing with the test voltages used for resistibility testing; 2) to provide clear guidelines on classifying interfaces as external or internal. Rec. ITU-T K.75 (04/2008) 1 Recommendation ITU-T K.75 Classifica
22、tion 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, network operators and test houses on the classification of the type of interface, i.e., external (subjected t
23、o a.c. surges or conducted lightning surges) or internal (subjected to short fall-time transients induced into building cabling); information on the waveform of transients appearing at equipment interfaces for insulation coordination purposes. This Recommendation mainly applies to customer equipment
24、 due to safety being achieved in other ways for network equipment, e.g., earthing or powering from a safe supply, e.g., a supply voltage equal to or less than 60 V d.c. (Note, 60 V d.c. is an ES1 voltage.) However, the waveform of transients appearing at equipment interfaces is also provided for tel
25、ecommunication centres and access network sites in case it is needed in the future. This Recommendation assumes that the telecommunication equipment is either mains powered or powered from the telecommunication network, and is installed according to the earthing and bonding requirements relevant to
26、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 requirements such as test procedures and test criteria. This Recommendation does not describe mitigation measures or the various approaches used to determine the nee
27、d to provide additional protection external to the equipment (primary protection). This Recommendation does not address overvoltages caused by power contact with low-voltage or medium-voltage power lines. 2 References The following ITU-T Recommendations and other references contain provisions which,
28、 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 investigate the possibility of appl
29、ying 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 Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T
30、 K.20 Recommendation ITU-T K.20 (2003), Resistibility of telecommunication equipment installed in a telecommunications centre to overvoltages and overcurrents. ITU-T K.21 Recommendation ITU-T K.21 (2003), Resistibility of telecommunication equipment installed in customer premises to overvoltages and
31、 overcurrents. ITU-T K.27 Recommendation ITU-T K.27 (1996), Bonding configurations and earthing inside a telecommunication building. ITU-T K.35 Recommendation ITU-T K.35 (1996), Bonding configurations and earthing at remote electronic sites. 2 Rec. ITU-T K.75 (04/2008) ITU-T K.45 Recommendation ITU-
32、T K.45 (2003), Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages and overcurrents. ITU-T K.66 Recommendation ITU-T K.66 (2004), Protection of customer premises from overvoltages. ITU-T K.67 Recommendation ITU-T K.67 (2006), Expected surges on tel
33、ecommunications and signalling networks due to lightning. IEC 60664-1 IEC 60664-1 (2007), Insulation coordination for equipment within low-voltage systems Part 1: Principles, requirements and tests. IEC 60950-1 IEC 60950-1 (2005), Information technology equipment Safety Part 1: General requirements.
34、 IEC 62305-2 IEC 62305-2 (2006), Protection against lightning Part 2: Risk management. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined by IEC or currently under study in IEC. 3.1.1 basic insulation: Insulation to provide basic safeguard against electric
35、 shock. 3.1.2 double insulation: Insulation comprising both basic insulation and supplementary insulation. 3.1.3 equipotential bonding: Electrical connection putting various exposed conductive parts and extraneous conductive parts at a substantially equal potential. 3.1.4 external circuit: Circuit t
36、hat 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 for external interfaces. 3.1.5 reinforced insulation: Single insulation system that provides a degree of protection again
37、st electric shock equivalent to double insulation. 3.1.6 supplementary insulation: Independent insulation applied in addition to basic insulation to provide supplementary safeguard for fault protection against electric shock. 3.2 Terms defined in this Recommendation This Recommendation defines the f
38、ollowing 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 interface: Any port on the equipment which may be subjec
39、ted to a.c. surges and conducted lightning surges. 3.2.3 internal interface: Any port on the equipment which is only ever exposed to short duration induced transients. 3.2.4 person isolation voltage: Highest value of a specified overvoltage that does not cause breakdown of insulation between a telec
40、ommunication line and a person in contact with the equipment. Rec. ITU-T K.75 (04/2008) 3 3.2.5 telecommunication overvoltage category: A designation defining a transient overvoltage condition. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: ES Energy
41、Source GDT Gas Discharge Tube EPR Earth Potential Rise EUT Equipment Under Test LPS Lightning Protection System MET Main Earth terminal PE Protective Earth SELV Safety Extra Low Voltage SPD Surge Protective Device TNV Telecommunication Network Voltage 5 Conventions None. 6 Classification of interfac
42、es Two things 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 This is done by determining the types of overvo
43、ltages 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. If it is only exposed to short transients, due to induction into building wiring, it can be classified as an internal int
44、erface. 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 nodes in Figure 1. Figure 1 can b
45、e used for identifying 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 E-S, E-R, R-S, S-S shown in Figure 1 (s
46、ee 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 I-I and M-M shown in Figure 1 (see also Appendix I). 4 Rec. ITU-T K.75 (04/2008) A detailed method for class
47、ifying interfaces is given in Annex A. Figure 1 Reference configuration of telecommunication and signal lines 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 building, e.g., MDF.
48、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 exchanges building and the internal cabling. I Tran
49、sition between equipment interface inside the customers building and the internal cabling. 6.2 Defining the transient This Recommendation adopts an approach suggested by IEC 60664-1 by defining “telecommunications overvoltage categories“. Table 2 shows the overvoltage categories and overvoltage transient on mains according to IEC 60664-1. Rec. ITU-T K.75 (04/2008) 5 Table 2 Mains overvoltage categories and overvoltage transient on mains interfaces, according to IEC 60664-1 Mains overvoltage categories Lightning impulse transient
