ITU-T SERIES K SUPP 3-2015 ITU-T K 20 K 21 K 45 K 82 C Additional criteria to protect telecommunication cabling during a power cross event (Study Group 5)《ITU-T K 20 K 21 K 45 K 82.pdf

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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 Series K TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Supplement 3 (10/2015) SERIES K: PROTECTION AGAINST INTERFERENCE ITU-T K.20, K.21, K.45, K.82 Additional criteria to protect telecommunication cabling during a power

2、cross event ITU-T K-series Recommendations Supplement 3 K series Supplement 3 (10/2015) i Supplement 3 to ITU-T K-series Recommendations ITU-T K.20, K.21, K.45, K.82 Additional criteria to protect telecommunication cabling during a power cross event Summary Supplement to the ITU-T K-series Recommend

3、ations provides criteria that enable the implementation of power cross protection for telecommunication cabling connected to equipment compliant with ITU-T K.20, ITU-T K.21 and ITU-T K.45. This supplement aims to: Provide current-time limitations to protect telecommunication cabling from fusing and

4、wire insulation damage. Explain the evolution of physical wiring simulators and their drawbacks. Provide designers with the tools to extrapolate the supplement current-time limitations data to larger and smaller conductor sizes. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-

5、T K Suppl. 3 2015-10-23 5 11.1002/1000/12686 _ * To access the Recommendation, 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 K series Supplement 3 (10/2015) FOREWORD

6、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 tech

7、nical, 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,

8、 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-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IE

9、C. NOTE In this publication, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this publication is voluntary. However, the publication may contain certain mandatory provisions (to ensure, e.g

10、., interoperability or applicability) and compliance with the publication 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 sugge

11、st that compliance with the publication is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this publication may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, va

12、lidity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the publication development process. As of the date of approval of this publication, ITU had not received notice of intellectual property, protected by patents, which may be required

13、 to implement this publication. 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 2016 All rights reserved. No part of this publication may be reproduced, by

14、any means whatsoever, without the prior written permission of ITU. K series Supplement 3 (10/2015) iii Table of Contents Page 1 Introduction . 1 2 Wire current-time capability . 1 3 Wire current-time limits . 2 3.1 Insulation damage . 2 3.2 North American wiring simulation . 2 Appendix I Wire equati

15、ons and data . 4 I.1 Introduction 4 I.2 DC . 4 I.3 Transient current . 5 I.4 Results 5 Appendix II Evolution of North American wiring simulators 7 II.1 Power fault sources . 7 II.2 General . 7 II.3 ANSI/TIA/EIA-571 and ANSI/TIA/EIA-571A wiring simulator documents . 8 II.4 UL 1459-1998 14 II.5 UL 609

16、50-1 15 II.6 GR-1089-CORE, Issue 6 16 Bibliography. 18 K series Supplement 3 (10/2015) 1 Supplement 3 to ITU-T K-series Recommendations ITU-T K.20, K.21, K.45, K.82 Additional criteria to protect telecommunication cabling during a power cross event 1 Introduction ITU-T equipment Recommendations b-IT

17、U-T K.20, b-ITU-T K.21 and b-ITU-T K.45 have power cross tests with prospective currents ranging from 0.23 A to 23 A. These power cross tests do not include an assessment of equipment feed cable heating. This Supplement provides information on the equipment overcurrent protector operate values to co

18、mprehend wiring current limitations. Appendix I describes the tools and references a designer may use to define the overcurrent protector maximum time-current characteristic for specific wiring types. Appendix II covers the evolution of North American wiring simulators. 2 Wire current-time capabilit

19、y Figure 1 shows a typical wire current-time characteristic. The current capability for short durations is governed by an adiabatic i2t limitation, which results in the downward sloping portion current line. At longer durations (d.c.) a steady-state condition occurs resulting in a horizontal portion

20、 of the current line. This sort of curve is typically used to define the operate values of a single element fuse. Figure 1 Typical wire current-time curve A current-time curve such as that in Figure 1 might be for wire conductor fusing or the onset of the wire insulation damage, or some intermediate

21、 condition. The performance requirement for the equipment overcurrent protector would be to operate in the acceptable area of the figure over the range of expected power cross current levels. North America equipment standards have for many years included wiring simulators during a power fault event.

22、 These wiring simulators were developed to be part of a power fault test and are used as indicators of whether wiring would be damaged in an actual power fault event. Because of the country of origin of the wiring simulators, most of the data is referenced to American Wire Gauge (AWG) wire sizing. T

23、o relate the AWG to metric sizing, metric diameter equivalents are given in this supplement. For telecommunication cabling, for a given AWG, n, the wire diameter d mm can be calculated from: 2 K series Supplement 3 (10/2015) 39/3696*127.0 nd 3 Wire current-time limits 3.1 Insulation damage Figure 2

24、shows the limit curves for 0.4 mm and 0.2 mm diameter copper wire based on the b-P-32-382 i2t values and the b-IEC 60950 equivalent DC values from Table I1 in Appendix I. Figure 2 Insulation damage limit current-time curve for 0.2 mm and 0.4 mm copper wire In the steady state, long-term condition, t

25、he maximum allowed current for 0.4 mm diameter copper wire is 1.3 A and 0.2 mm wire is 0.53 A based on b-IEC 60950 and b-IEC 62368. The ITU-T equipment Recommendations b-ITU-T K.20, b-ITU-T K.21 and b-ITU-T K.45 power cross generator will only apply a maximum prospective current of 23 A. 3.2 North A

26、merican wiring simulation As shown in Appendix II, the wiring simulator used depends on the standard being complied with. Furthermore, the simulator that can be used may be a current-time curve, a physical simulation or both. A physical simulation can be a specified fuse or a length of AWG wire. Non

27、e of the physical simulations are precision indicators, hence the move towards current-time templates. Any “universal“ simulator curve should add a safety margin to cover the possible use of physical simulators. The biggest variability occurs in the steady state region b-Lindquist. The most popular

28、wiring simulation fuse is the MDL-2. Here “2“ indicates that the rated current is 2 A. In US standards, the MDL-2 fuse must conduct 1.1*2 = 2.2 A for four hours b-Lindquist. Figure 3 shows the published MDL-2 curve adjusted down to 2.2 A from the typical 2.6 A at 1000 s. K series Supplement 3 (10/20

29、15) 3 Figure 3 MDL-2 limit current-time curve (derated to 85% of its typical value) Points to note here are: The Figure 3 MDL-2 curve (derated to 85% of its typical value) falls below the 0.4 mm Figure 2 insulation damage curve for times less than 10 s. Conversely, for times greater than 20 s, the F

30、igure 3 curve allows more current than the Figure 2 curve. The Figure 3 curve has a variable i2t. At 0.01 s i2t is 13 A2s, 0.1s is 45 A2s and 1 s is 65 A2s. 4 K series Supplement 3 (10/2015) Appendix I Wire equations and data I.1 Introduction This appendix describes the tools and references that a d

31、esigner may use to define the overcurrent protector maximum time-current characteristic for specific wiring types. Historical information on the b-Preece and b-Stauffacher referenced equations given in b-Adams et al. I.2 DC The Preece equation b-Preece is used to predict the DC fusing current of wir

32、es in free air: 5.1*dAI Where I is the wire fusing current, d is the wire diameter and A is a constant, dependent of units system and the wire material. For a copper wire of diameter of d mm, the equation becomes: 5.1*80 dI For example, AWG 32 has a diameter of 0.2019 mm, making I = 80*0.20191.5 = 7

33、.3 A. There have been other values of multiplier and power reported see b-Babrauskas et al. In practice, a more desirable limitation is the prevention of wire insulation damage rather than wire fusing. One reference often used is section 3.16 of b-MIL-STD-975, Wire and Cable Derating Criteria. Figur

34、e I.1 plots the 3.16 table data for wire diameters of 0.2 mm to 2 mm. The table data is for an ambient temperature of 70 C and various insulator maximum temperatures (Teflon at 200 C down to types of PVC at 105 C). For cable bunches, a derating factor of (28-N)/27 should be applied, where N is the n

35、umber of conductors. The derating factor is taken as a constant value once the bundle exceeds fifteen conductors. Figure I.1 MIL-STD-975 derated current versus wire diameter K series Supplement 3 (10/2015) 5 The green line in Figure I.1 is the MIL-STD-975 current curve set to 1.3 A for a wire diamet

36、er of 0.4 mm, the value specified in b-IEC 60950-1 and b-IEC 62368-1 safety standards. I.3 Transient current The Onderdonk equation referenced by b-Stauffacher is for adiabatic conditions and is used to predict the I2t for a given wire temperature change for periods up to about 1 s. The I2t value is

37、 dependent on the fourth power of the conductor diameter, d. The metric version of the equation is shown below: 1274*10*28.7 442 TL O GdtI where: I (A) is the wire current d (mm) is the wire diameter t (s) is the current flow time, and T is the temperature difference (C) between the wire and ambient

38、. For an ambient temperature of 30 C and the copper melting temperature of 1083 C, the equation becomes: 442 *10*5 dtI The b-P-32-382 standard uses the Onderdonk equation to predict the maximum wire I2t value for no insulation damage by using the insulation damage temperature to ambient temperature

39、difference. For PVC insulation the insulation I2t is about 15% of the wire fusing I2t. The reduction factor can rise to about 30% for 250 C cable insulation. I.4 Results Underwriters Laboratories Inc. produced the document An Investigation of the Use of 16 and 18 AWG Conductors for Power Branch Circ

40、uits in Industrial Machinery Applications for the NFPA79 Small Wire Working Group b-UL E4273. Clause Thermal Withstand Ratings for Insulated Conductors covers equations from b-P-32-382 (Onderdonk for no insulation damage), research conducted by b-Middendorf (50% insulation voltage loss), data from b

41、-Soares (lug tightness lost) and the Onderdonk b-Stauffacher wire melting point equation. With reference to 26 AWG wire melting I2t b-Stauffacher the other condition factors were 14% P-32-382, 37% Middendorf and 29% Soares. Table I.1 lists the b-UL E4273 wire electrical parameters for 18 AWG to 32 A

42、WG with PVC insulation. 6 K series Supplement 3 (10/2015) Table I.1 b-UL E4273 Parameters for 18 to 32 AWG Wire AWG Dia (mm) Preece DC Fusing (A) Onderdonk transient melting i2t (A2s) Onderdonk Preece knee (s) Middendorf (50% insulation voltage loss) i2t (A2s) ICEA standard P-32-382 i2t (A2s) IEC DC

43、 Figure I.1 (A) 18 1.0237 82.7 64787 9.1 23971 8881 4.99 19 0.9116 69.5 40745 8.1 15076 5588 4.19 20 0.8118 58.4 25625 7.2 9481 3516 3.53 21 0.7229 49.1 16116 6.4 5963 2212 2.98 22 0.6438 41.2 10135 5.7 3750 1392 2.51 23 0.5733 34.7 6374 5.1 2358 876 2.13 24 0.5106 29.1 4009 4.6 1483 551 1.81 25 0.4

44、547 24.5 2521 4.1 933 347 1.54 26 0.4049 20.6 1586 3.6 587 218 1.32 27 0.3606 17.3 997 3.2 369 137 1.14 28 0.3211 14.5 627 2.9 232 86.3 0.98 29 0.2859 12.2 394 2.6 146 54.3 0.85 30 0.2546 10.3 248 2.3 92 34.2 0.73 31 0.2268 8.61 156 2.0 58 21.5 0.63 32 0.2019 7.24 98 1.8 36 13.5 0.53 Common AWG size

45、s have these values b-UL E4273: 26 AWG: 0.4049 mm diameter, 20.6 A DC fusing current, 1586 A2s melting I2t, 587 A2s insulation damage I2t, 218 A2s no insulation damage I2t and IEC DC 1.32 A. 28 AWG: 0.3211 mm diameter, 14.5 A DC fusing current, 627 A2s melting I2t, 232 A2s insulation damage I2t, 86.

46、3 A2s no insulation damage I2t and IEC DC 0.98 A. 32 AWG: 0.2019 mm diameter, 7.24 A DC fusing current, 2.2 A DC no insulation damage, 98 A2s melting I2t, 36 A2s insulation damage I2t, 13.5 A2s no insulation damage I2t and IEC DC 0.53 A. K series Supplement 3 (10/2015) 7 Appendix II Evolution of Nor

47、th American wiring simulators II.1 Power fault sources According to US standards, to prevent wire damage, a wiring network of traditional (0.1 mm diameter X 4 32 AWG (0.2 mm),) phosphor bronze tinsel conductor telephone line cord feeding two pieces of terminal equipment should have its maximum curre

48、nt limited to: 2.2 A (long duration), 7 A for 5 s, and I2t = 100 A2s for short durations. A single wire of 26 AWG (0.4 mm diameter) has limits of: 5 A (long duration), and I2t = 1200 A2s for short durations. The maximum applied power fault stress levels are: 1) 600 Vrms, 40 Arms for 1.5 s: b-UL 6095

49、0-1 resulting from a high voltage power line contact to a telephone shielded cable (I2t = 2400 A2s) or 425/600 Vrms, 40 Arms for 1.5 s: b-GR-1089-CORE resulting from a high voltage power line contact to a telephone shielded cable (I2t = 2400 A2s) 2) 600 Vrms, 7 Arms for 5 s: b-UL 60950-1 Power induction or from a ground potential rise after a power line fault to a multi-grounded neutral condu