ITU-T K.21-2008 用户终端电信设备耐过电压和过电流的能力 Resistibility of telecommunication equipment installed in customer premises to overvoltages and over

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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 ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU U n i o n K.21 (04/2008) SERIES K: PROTECTION AGAINST INTERFERENCE Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents Recommendation ITU-T K.21 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 equipment that is installed in or on a customer premises building. Overvoltages or overcurrents covered by this Recommendation include surges due to lightning on or near the line plant, short-term induction from adjacent a.c. power lines or railway systems, earth potential rise due to power faults, direct contacts between telecommunication lines and power lines and electrostatic discharges. The sources for overvoltages in internal lines are mainly inductive coupling caused by lightning currents being conducted in nearby lightning strokes or lightning currents being conducted in nearby conductors. Major changes compared with the 2003 version of this Recommendation include: • removing the power induction test requirement for antenna ports where the installation is within the scope of Recommendation ITU-T K.71; • clearer definition of when the internal and external port classification applies to antenna ports. Source Recommendation ITU-T K.21 was approved on 13 April 2008 by ITU-T Study Group 5 (2005-2008) under Recommendation ITU-T A.8 procedure. Rec. ITU-T K.21 (04/2008) i FOREWORD The International Telecommunication Union (ITU) is the United 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 Recommendations 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 approval 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-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 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 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 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. ii Rec. ITU-T K.21 (04/2008) CONTENTS Page 1 Scope ............................................................................................................................ 1 2 References..................................................................................................................... 1 3 Definitions and abbreviations ....................................................................................... 3.1 Definitions ...................................................................................................... 1 1 4 Tests................................................

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