1、INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU K.41 (05198) SERIES K: PROTECTION AGAINST INTERFERENCE Resistibility of internal interfaces of telecommunication centres to surge overvoltages ITU-T Recommendation K.41 (Previously CCITT Recommendation) STD-
2、ITU-T RECMN K.4L-ENGL 2998 YB62591 0649639 525 = ITU-T K-SERIES RECOMMENDATIONS PROTECTION AGAINST INTERFERENCE For further details, please refer to ITU-TList ofRecornmendations - STD.ITU-T RECMN K-4L-ENGL 1998 4862593 0649640 237 ITU-T RECOMMENDATION K.41 RESISTIBILITY OF INTERNAL INTERFACES OF TEL
3、ECOMMUNICATION CENTRES TO SURGE OVERVOLTAGES Summary This Recommendation specifies test methods and levels for the resistibility test against surge overvoltages on internal interface lines within a telecom centre interconnecting the several system blocks. The tests simulate surge overvoltages caused
4、 by magnetic fields from lightning strokes in or near the telecom building. Source ITU-T Recommendation K.41 was prepared by ITU-T Study Group 5 (1997-3000) and was approved under the WTSC Resolution No. 1 procedure on the 15th of May 1998. Recommendation K.41 (0998) i - STD-ITU-T RECMN K-LiL-ENGL 1
5、998 M 4862591 Ob49641 173 M FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommuni- cations, The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, o
6、perating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in th
7、eir tum, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborat
8、ive basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or impleme
9、ntation of this Recommendation may involve the use of a claimed Intellectual Property Right. The 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 proce
10、ss. As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore stro
11、ngly urged to consult the TSB patent database. O ITU 1998 All rights reserved. ho part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing froin the ITU. 11 Recommendation K.41 (0
12、5/98) STDmITU-T RECMN K*YL-ENGL 1998 W 4662591 Ob49b42 OOT W CONTENTS 1 Scope 2 References 3 Test conditions . 4 Test criterion . 5 Test requirements . 5.1 Test circuit . 5.2 Test levels . Appendix I . 1.1 1.2 General measures Shape of surge voltages on internal lines of telecom centres and their re
13、duction by shielding 1.3 Additional protection measures Recommendation K.41 (05/98) Page 1 2 7 . 111 Introduction External telecom lines entering a telecom building may be subjected to overvoltages due to induction by lightning currents. However, not only external cables are affected by lighming but
14、 also internal lines interconnecting telecom equipment installed inside a telecom building. The protection of ports connected to external lines is covered by Recommendation K.20 while that of ports connected to internai lines is covered in this Recommendation. The sources for overvoltages in interna
15、l lines are mainly magnetic fields caused by lightning currents penetrating the telecom building. The amplitude and waveshape of the overvoltages depend on several factors (see Appendix I). iv Recommendation K.41 (05/98) Recommendation K.41 Switching equipment RESISTIBILITY OF INTERNAL INTERFACES OF
16、 TELECOMMUNICATION CENTRES TO SURGE OVERVOLTAGES Transmission Transmission equipment 1 equipment 2 (Geneva, I998) 1 Scope The Recommendation relates to internal interfaces within a telecom building interconnecting several system blocks of this telecom centre, for example switching equipment, differe
17、nt transmission equipment, operation system and power supply (see Figure 1). D.C. power system Operation system Figure 1K.41 The tests of this Recommendation simulate overvoltages caused by magnetic fields from direct lightning strikes to the lightning protection system of the telecom building or fr
18、om lightning strokes nearby the telecom building. The internal cables, which includes symrnetncal and coaxial telecommunication lines, signal lines and DC power lines, may extend hundreds of meters but do not leave the building. The requirements of this Recommendation relate to the inherent resistib
19、ility of the input and output ports of the tested equipment. It is presumed that a Minimum Common Bonding Network has been installed according to Recommenda- tion K.40 and that the earthing and bonding network is either a Mesh-BN configuration or a Mesh-IBN with a bonding mat configuration as descri
20、bed in Recommendation K.27. In cases which do not fulfil these conditions, additional protection measures or equipment with higher resistibility levels may be necessary. Peripheral equipment which is not defined to be telecommunication equipment (e.g. personal computers and printers) is not within t
21、he scope of this Recommendation, This Recommendation only covers the situation where one of the power supply inputs is earthed at the equipment under test. Recommendation K.41 (05/98) 1 STDsITU-T RECMN KmrlL-ENGL 1998 4862593 Ob49645 819 2 References The following ITU-T Recommendations and other ref
22、erences contain provisions which, through referenced 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; all users of this Recommendation are therefore encouraged
23、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 Recommendations is regularly published. - - ITU-T Recommendation K.27 ( 1996), Bonding configurations and earthing inside a telecommunicati
24、on building. ITU-T Recommendation K.40 (1 996), Protection against LEW in telecommunications centres. - IEC Standard 61000-4-5: 1995, Electromagnetic Compatibility (EMC) - Part 4: Testing and measurement techniques, Section 5: Surge immunity test. 3 Test conditions Following test conditions are vali
25、d: - - - The tests are type tests. The equipment shall be powered and fully operational at the time the test pulse is applied. The input and output ports of the equipment at which the test is to be applied should be identified by the manufacturer. - - - The untested ports are terminated as agreed by
26、 the manufacturer and the operator. The normal operation of the equipment is examined after the test. In all cases where a maximum voltage (U(max) is specified, tests should also be made at lower voltages if this is necessary to confirm that the equipment will resist any voltage up to the maximum va
27、lue specified. - Each test should be applied at least five times in positive and in negative polarity. The time interval between two pulses shall be at least 1 minute. - - The test should be carried out at ports as described in Table 1. The length of the interface cable used for tests applied to shi
28、elded lines shall be 20 m. The type of the cable shall be agreed by the manufacturer and the operator. EMC performance will usually be the major consideration. - 4 Test criterion The equipment under test shall withstand the test without damage or other disturbance (such as corruption of software, da
29、ta held in memory or misoperation of fault protection facilities) and shall operate properly within the specified limits after the test. It is not required to operate correctly while the test condition is present. 5 Test requirements 5.1 Test circuit The circuit diagram, waveform and other parameter
30、s of the hybrid generator are defined in the Standard IEC 6 1000-4-5. The test generator is connected with the tested ports as shown in Figure 2. Measures may need to be taken during telecommunication and signal port tests to ensure that normal operation of the equipment is not interfered with. For
31、the test of the DC power port, coupling/decoupling elements according to Figure 2 c) are used. An example of a Decoupling network can be found in the standard mentioned above. 2 Recommendation K.41 (0398) STD-ITU-T RECMN K-4L-ENGL 1998 4862571 0649646 755 generator (Ri = 2 Q) 1.2150 PS- 8/20 ps ) -
32、- hybrid I 8120 ps hybrid generator (Ri = 2 Q) oA OB EUT PE - - 9 PF II TI 1.2/50 IJS- 8120 ps hybrid a) Telecommunication and signal-ports for unshielded cables EUT oA OE I=20m f I EUT generator (Ri = 2 Q) o T 0 For repeatability of measurement, it is recommended that the test be performed on an ea
33、rth reference plane, with the cable laid on the ground plane in a snake pattern. All conductors are connected together and with the shield. (Reason: in worst case, inserted protective elements in the counterpart equipment - not included in this test Set-up - can cause short circuit termination.) b)
34、Telecommunication and signal-ports for shielded cables Decoupling network D.C. power supply c) D.C. power-interfaces Figure 2K41 - Test circuits Recommendation K.41 (0.998) 3 STD-ITU-T RECMN K-41-ENGL 1998 4Bb2591 Ob49b47 691 No. interface Test circuit I Unshieided with Figure 2 a) signai line R=IOR
35、 unsymmetrical 2 Unshielded with Figure 2 a) signal line R=lOR symmetrical 3 Shielded with Figure 2 b) signal line unsymmetrical or symmetrical 4 D.C. power line Figure 2 c) 5.2 Test levels Differential mode Common mode U(Illax) Terminal U(Inz) connections 500 V T, and A N.A. N.A. N.A. 500 V N.A. N.
36、A. 500 V (5 250 A) 500 V T, with A N.A. See Table 1. Table 1K.41 Terminal I I connections Tl and A; T? and B I Tl with shield and all conductors N.A. 1 N.A. Not applicable I Appendix I 1.1 Shape of surge voltages on internal lines of telecom centres and their reduction by shielding For establishing
37、resistibility test for equipment connected to internal lines, the magnitude and shape of induced lightning surges to be expected has to be known. The overvoltage in unshielded lines caused by lightning currents penetrating the telecom building is proportional to the differential quotient of the ligh
38、tning current versus time and to the mutual inductivity between the line and the bonding network: U = M - diidt This means that the overvoltage is strongly depending on the rise time of the lightning current. The rise time determines mainly the duration and the amplitude of the surge voltage. Short
39、and high surge voltages are generated by lightning surge currents with a very short front time. However, the energy content of these surges may be comparatively low. Bonding networks with a mesh-structure are most effective in reducing surge voltages caused by lightning currents on the earthing syst
40、em. By using a mesh structure, the lowest effective inductiviw of the bonding network can be achieved. Therefore it is assumed that the earthing and bonding configurations of the telecom centre fulfil the requirements of Recommendation K.27. For shielded lines, a pari of the lightning current flows
41、over the shield. The overvoltage on the shielded lines begins delayed and the rise time is longer. 4 Recommendation K.41 (05/98) STD-ITU-T RECMN KmYL-ENGL 1998 = Y862591 0649648 528 = The overvoltages on internal lines are reduced effectively by using appropriate shields. It is assumed that the shie
42、lds are earthed at both ends. In principle, two types of cables shields with quite different shielding performance are used: 0 One type is less expensive and widely used. The screen consists of a thin metal tape around the cable core, the conductivity of which is improved by a longitudinal wire. Wit
43、h this type of cables, the overvoltages can be reduced at least by a factor 2. Cables with a braided screen reduce the values of surge voltages by a factor 1 O. o 1.2 General measures The amplitude of the surge overvoltage can vary by a factor 100 and more depending on the shielding of the building,
44、 on the size of the effective loops (take into account also the loops between telecommunication lines and power lines), on the length of the internal cables and on the kind of used cable ducts. As mentioned in the main part of this Recommendation, the test levels were established for equipment insta
45、lled in a telecom building with a Minimum Common Bonding Network (MCBN). MCBN means according to Recommendation K.40 that: - - A ring conductor is along the inside perimeter of the building at each floor. There are connections between the ring conductor of each floor with vertical bonding conductors
46、, approximating a Faraday cage; the distance between the vertical conductors should not be greater than 5 m. At the ground floor is a connection of the ring conductor to the ring earth electrode. - 1.3 Additional protection measures Additional protection measures are under study in Study Group 5. Re
47、commendation K.41 (05198) 5 Series A Series B Series C Series D Series E Senes F Series G Series H Series 1 Series J Series K Series L Series M Series N Series O Series P Series Q Series R Series S Series T Series U Series V Series X Series Y Series Z ITU-T RECOMMENDATIONS SERIES Organization of the
48、 work of the ITU-T Means of expression: definitions, symbols, classification General telecommunication statistics General tariff principles Overall network operation, telephone service, service operation and human factors Non-telephone telecommunication services Transmission systems and media, digit
49、al systems and networks Audiovisual and multimedia systems Integrated services digital network Transmission of television, sound programme and other multimedia signals Protection against interference Construction, installation and protection of cables and other elements of outside plant TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits Maintenance: international sound programme and television transmission circuits Specifications of measuring equipment Telephone transmissi
