1、 International Telecommunication Union ITU-T K.77TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2009) SERIES K: PROTECTION AGAINST INTERFERENCE Characteristics of metal oxide varistors for the protection of telecommunication installations Recommendation ITU-T K.77 Rec. ITU-T K.77 (01/2009) i Re
2、commendation ITU-T K.77 Characteristics of metal oxide varistors for the protection of telecommunication installations Summary Recommendation ITU-T K.77 gives the basic requirements to be met by metal oxide varistors (MOVs) for the protection of power circuits and signal circuits of telecommunicatio
3、n installations from surges. The purpose of this Recommendation is to provide technical guidelines for purchasers and manufacturers of MOVs to ensure their satisfactory operation in the applications for which they are intended. This Recommendation is intended to be used for the harmonization of exis
4、ting or future specifications issued by MOV manufactures, telecommunication equipment manufactures, administrations or network operators. Source Recommendation ITU-T K.77 was approved on 13 January 2009 by ITU-T Study Group 5 (2009-2012) under Recommendation ITU-T A.8 procedures. This version includ
5、es the corrections agreed upon by ITU-T Study Group 5 (2009-2012) on 29 May 2009. ii Rec. ITU-T K.77 (01/2009) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The
6、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 Standard
7、ization 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 te
8、chnology 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. Compl
9、iance 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 obli
10、gatory 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 implementati
11、on 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
12、 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
13、 consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 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.77 (01/2009) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4
14、 Abbreviations and acronyms 6 5 Storage conditions 6 6 Electrical requirements . 6 6.1 Varistor voltage 6 6.2 Maximum a.c. (d.c.) continuous operating voltage 7 6.3 Leakage current d.c. . 7 6.4 Leakage current a.c. 7 6.5 Capacitance . 7 6.6 Clamping voltage 7 6.7 Maximum discharge current . 10 6.8 E
15、SD impulse test 11 6.9 Rated dissipation (impulse life) 12 6.10 Rated impulse energy . 12 6.11 Impulse durability . 12 6.12 Endurance at maximum operating temperature 12 6.13 TOV withstanding capability . 12 6.14 Insulation resistance (for insulated MOV only) . 13 6.15 Voltage proof (for insulated M
16、OV only) 13 7 Test methods . 13 7.1 Varistor voltage 13 7.2 Maximum continuous a.c. (d.c.) voltage 13 7.3 Leakage current d.c. . 13 7.4 Leakage current a.c. 14 7.5 Capacitance . 15 7.6 Clamping voltage 15 7.7 Maximum discharge current . 15 7.8 ESD impulse test (for SMD type MOV only) 16 7.9 Rated di
17、ssipation (impulse life) 16 7.10 Rated impulse energy . 17 7.11 Impulse durability . 17 7.12 Endurance at maximum operating temperature 18 7.13 TOV withstanding 19 7.14 Insulation resistance . 20 7.15 Voltage proof 21 iv Rec. ITU-T K.77 (01/2009) Page 8 Environment tests . 21 8.1 Robustness of termi
18、nations . 21 8.2 Solderability . 22 8.3 Resistance to soldering heat . 23 8.4 Vibration . 23 8.5 Bump 23 8.6 Rapid changes of temperature 24 8.7 Climatic sequence . 24 8.8 Damp heat, steady state 24 8.9 Fire hazard 25 8.10 Solvent resistance of marking 25 8.11 Component solvent resistance 25 9 Infor
19、mative characteristics 25 9.1 V-I characteristic 25 9.2 Current peak de-rating curve 26 9.3 Volt-ampere characteristics of low field region . 28 10 Identification . 28 10.1 Marking 28 10.2 Documentation . 29 11 Ordering information 29 Annex A Impulses used in this Recommendation 30 A.1 Definition of
20、 T1/T2impulse 30 A.2 Tolerances for T1/T2impulse (Figures A.1 and A.2) 30 A.3 Tolerances for rectangular impulse (Figure A.3) . 31 A.4 ESD discharge current impulse (Figure A.4) . 31 Appendix I Mounting method for measurement of SMD type . 33 I.1 Recommended mounting method . 33 I.2 Wave soldering m
21、ethod 33 I.3 Reflow soldering method . 33 Appendix II Response of MOV to 8/20 impulse current and clamping voltage test 35 II.1 Double peaks on the voltage waveform . 35 II.2 Instantaneous volt-ampere characteristic . 36 II.3 Voltage limiting characteristics 38 II.4 Methods for avoiding interference
22、 during clamping voltage measurement . 40 Bibliography. 43 Rec. ITU-T K.77 (01/2009) v Introduction Two types of metal oxide varistor (MOV) may be differentiated by their constructions: leadless surface mounting device (SMD)-type MOVs and leaded disc-type MOVs (including wire-terminations and strap
23、terminations), while by their application fields the MOV may be divided into MOVs for power circuit use and MOVs for signal circuit use. Table 1 gives the applicable test items for various type MOVs. Rec. ITU-T K.77 (01/2009) 1 Recommendation ITU-T K.77 Characteristics of metal oxide varistors for t
24、he protection of telecommunication installations 1 Scope This Recommendation: gives the characteristics of metal oxide varistors (MOVs) used in accordance with b-ITU-T K.11 for the protection of power supply circuits and signal circuits of telecommunication installations against overvoltages; does n
25、ot deal with combinations of several MOVs connected in series and/or in parallel, nor combinations of MOV with other components; does not deal with mountings and their effect on MOV characteristics, the characteristics apply to MOV as a component, mounted only in the ways described for the tests; do
26、es not deal with mechanical dimensions; does not deal with quality assurance requirements. 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 edi
27、tions indicated were 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 val
28、id 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. IEC 60060-1 IEC 60060-1 (1989), High-voltage test techniques Part 1: General definitions and test requirements. IEC 600
29、60-2 IEC 60060-2 (1994), High voltage test techniques Part 2: Measuring systems. IEC 60068-1 IEC 60068-1 (1988), Environmental testing Part 1: General and guidance. IEC 60068-2-1 IEC 60068-2-1 (2007), Environmental testing Part 2-1: Tests Test A: Cold. IEC 60068-2-2 IEC 60068-2-2 (2007), Environment
30、al testing Part 2-2: Tests Test B: Dry heat. IEC 60068-2-6 IEC 60068-2-6 (1995), Environmental testing Part 2-6: Tests Test Fc and guidance: Vibration (sinusoidal). IEC 60068-2-13 IEC 60068-2-13 (1983), Environmental testing Part 2: Tests Test M: Low air pressure. IEC 60068-2-14 IEC 60068-2-14 (1984
31、), Environmental testing Part 2: Tests Test N: Change of temperature. IEC 60068-2-20 IEC 60068-2-20 (1979), Environmental testing Part 2: Tests Test T: Soldering. IEC 60068-2-21 IEC 60068-2-21 (2006), Environmental testing Part 2-21: Tests Test U: Robustness of terminations and integral mounting dev
32、ices. IEC 60068-2-27 IEC 60068-2-27 (1987), Environmental testing Part 2: Tests Test Ea and guidance: Shock. 2 Rec. ITU-T K.77 (01/2009) IEC 60068-2-29 IEC 60068-2-29 (1987), Environmental testing Part 2: Tests Test Eb and guidance: Bump. IEC 60068-2-30 IEC 60068-2-30 (2005), Environmental testing P
33、art 2-30: Tests Test Db: Damp heat, cyclic (12 h + 12 h cycle). IEC 60068-2-45 IEC 60068-2-45 (1980), Environmental testing Part 2: Tests Test XA and guidance: Immersion in cleaning solvents. IEC 60068-2-54 IEC 60068-2-54 (2006), Environmental testing Part 2-54: Tests Test Ta: Solderability testing
34、of electronic components by the wetting balance method. IEC 60068-2-58 IEC 60068-2-58 (2004), Environmental testing Part 2-58: Tests Test Td: Test methods for solderability, resistance to dissolution of metallization and to soldering heat of surface mounting devices (SMD). IEC 60068-2-69 IEC 60068-2
35、-69 (2007), Environmental testing Part 2-69: Tests Test Te: Solderability testing of electronic components for surface mounting devices (SMD) by the wetting balance method. IEC 60068-2-78 IEC 60068-2-78 (2001), Environmental testing Part 2-78: Tests Test Cab: Damp heat, stead state. IEC 60099-4 IEC
36、60099-4 (2006), Surge arresters Part 4: Metal-oxide surge arresters without gaps for a.c. systems. IEC 60695-11-5 IEC 60695-11-5 (2004), Fire hazard testing Part 11-5: Test flames Needle-flame test method Apparatus, confirmatory test arrangement and guidance. IEC 61000-4-2 IEC 61000-4-2 (2001), Elec
37、tromagnetic compatibility (EMC) Part 4-2: Testing and measurement techniques Electrostatic discharge immunity test. IEC 61000-4-5 IEC 61000-4-5 (2005), Electromagnetic compatibility (EMC) Part 4-5: Testing and measurement techniques Surge immunity test. IEC 61051-1 IEC 61051-1 (2007), Varistors for
38、use in electronic equipment Part 1: Generic specification. IEC 61643-1 IEC 61643-1 (2005), Low-voltage surge protective devices Part 1: Surge protective devices connected to low-voltage power distribution systems Requirements and tests. IEC 61643-21 IEC 61643-21 (2000), Low voltage surge protective
39、devices Part 21: Surge protective devices connected to telecommunications and signalling networks Performance requirements and testing methods. IEC 61643-331 IEC 61643-331 (2003), Components for low-voltage surge protective devices Part 331: Specification for metal oxide varistors (MOV). 3 Definitio
40、ns This Recommendation defines the following terms: 3.1 applied voltage ratio (Rap): Ratio of d.c. voltage or peak of a.c. voltage applied on the MOV to the varistor voltage UN. 3.2 clamping voltage (Ucla): Maximum peak voltage across the MOV measured under conditions of a specified waveform impulse
41、 with current peak IP. If there is both a front peak and rear peak on the voltage waveform, the rear peak voltage is defined as the clamping voltage. Rec. ITU-T K.77 (01/2009) 3 NOTE For an individual MOV, peak voltages shall be measured in two directions, and the larger value of the two is referred
42、 to as the clamping voltage of this MOV. 3.3 clamping voltage ratio (Rcla): Ratio of the clamping voltage Uclato the varistor voltage UN(Rcla= Ucla/UN). 3.4 combination impulse (1.2/50-8/20): Impulse with open-circuit voltage of 1.2/50 s (T1/T2) and short-circuit current of 8/20 s (T1/T2), which is
43、expressed by “voltage peak/current peak“. NOTE Unless otherwise specified, the effective impedance shall be 2 , which is the quotient of the open-circuit voltage peak UPand the short-circuit current peak IP. 3.5 current peak de-rating curve: Curves expressing the relationship of the three variables
44、of IP, n, , where IPis impulse current peak, is the impulse width, and n is average application numbers of the impulse that the MOV can withstand in terms of specified pass criterion. The current IPshall be de-rated with the increasing of and/or n , that may be represented by equations 3-1 and 3-2.
45、lg Ig= A a lg n ( = constant) (3-1) lg Ig= B b lg (n = constant) (3-2) Where A, a, B and b are four constants which depend on the type and manufacturing of the MOV, also A and a depend on values, B and b depend on n values. NOTE Equations 3-1 and 3-2 agree well with the actual characteristics of MOV
46、 when n 10, while for n less than 10, PI deviated from these equations. 3.6 current de-rating fraction (FI): Ratio of impulse current peak IP(n, ) to the maximum discharge current Imax. IF = ),( nIP/maxI 3.7 effective resistance: Ratio of the rear peak voltage to the applied impulse current peak of
47、the specified waveform, unless otherwise specified, 8/20 impulse current shall be used. 3.8 effective linear resistance (RV): Linear component of the effective resistance determined by the high-impulse-current method. NOTE The linear resistance of the MOV may be determined by the high-frequency-sign
48、al method, infrared method and high-impulse-current method, but they may give different results. 3.9 effective non-linear resistance (RZ): Non-linear component of the effective resistance which can be expressed by equation 3-3 )1(1=PZIAR (3-3) Where: 1A is the virtual clamping voltage at 1 A of spec
49、ified impulse; is the non-linearity current index. 3.10 endurance at maximum operating temperature: Property to operate at maximum operating temperature and maximum continuous operating voltage (MCOV) for 1000 h. NOTE Unless otherwise specified, the maximum operating temperature shall be 85C. 3.11 front peak voltage (UF): Maximum voltage across the MOV occurri
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