ITU-T K 90-2012 Evaluation techniques and working procedures for compliance with exposure limits of network operator personnel to power-frequency electromagnetic fields (Study Grou.pdf

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1、 International Telecommunication Union ITU-T K.90TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2012) SERIES K: PROTECTION AGAINST INTERFERENCE Evaluation techniques and working procedures for compliance with exposure limits of network operator personnel to power-frequency electromagnetic field

2、s Recommendation ITU-T K.90 Rec. ITU-T K.90 (05/2012) i Recommendation ITU-T K.90 Evaluation techniques and working procedures for compliance with exposure limits of network operator personnel to power-frequency electromagnetic fields Summary Recommendation ITU-T K.90 provides evaluation techniques

3、and guidelines for compliance with safety limits for human exposure to electromagnetic fields (EMFs) of telecommunication network personnel (e.g., outside plant craft) at power frequencies (DC, 50 Hz and 60 Hz). This Recommendation does not set safety limits; it seeks to provide techniques and proce

4、dures for determining the need for any precautions at the work site. This Recommendation includes an electronic attachment containing the EMFACDC program. History Edition Recommendation Approval Study Group 1.0 ITU-T K.90 2012-05-29 5 ii Rec. ITU-T K.90 (05/2012) FOREWORD The International Telecommu

5、nication 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

6、 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 Recommend

7、ations 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 IEC. NOTE In this Recommendat

8、ion, 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., interoperabilit

9、y 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 complia

10、nce 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 o

11、r 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 t

12、o 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 2012 All rights reserved. No part of this publication may be reproduced, by

13、 any means whatsoever, without the prior written permission of ITU. Rec. ITU-T K.90 (05/2012) iii Table of Contents Page 1 Scope 1 2 References. 1 3 Terms and definitions . 2 4 Abbreviations and acronyms 2 5 General principles . 3 5.1 Field exposure limits 3 5.2 Exposure zones . 4 5.3 Sparkover 5 6

14、Magnetic and electric field calculations . 5 6.1 General procedure 5 6.2 Magnetic field . 6 6.3 Electric field . 7 7 Computer program 8 8 Examples of calculations 8 8.1 Simple geometries 8 8.2 Typical examples of power lines 10 9 Work procedures . 15 Appendix I MAD values for communication workers u

15、sed in North America 17 Appendix II Description of the program EMFACDC 18 Bibliography. 20 Electronic attachment: EMFACDC program Rec. ITU-T K.90 (05/2012) 1 Recommendation ITU-T K.90 Evaluation techniques and working procedures for compliance with exposure limits of network operator personnel to po

16、wer-frequency electromagnetic fields 1 Scope This Recommendation1aims to help with compliance of telecommunication network personnel working in vicinity of medium-voltage (MV) and high-voltage (HV) power lines with safety limits for human exposure to electromagnetic fields (EMFs) at power frequencie

17、s (DC, 50 Hz and 60 Hz). Also, it aims to provide practical work rules as one of the means of safeguarding network personnel that may need to work in close proximity to the MV and HV power lines. Where local or national laws, standards or guidelines on work safety or exposure limits to EMF exist and

18、 provide procedures that are at variance with this Recommendation, the pertinent local or national laws, standards or guidelines shall take precedence over the procedures provided in this Recommendation. This Recommendation does not cover exposure to electromagnetic fields at frequencies other than

19、DC, 50 Hz and 60 Hz. This Recommendation does not cover exposure to touch currents that arise as a result of coupling of electromagnetic fields generated by the power lines to other metallic objects, including telecommunication circuits. b-ITU-T K.52 aims to help with compliance of telecommunication

20、 installations and mobile handsets or other radiating devices used against the head with safety limits for human exposure to electromagnetic fields (EMFs). b-ITU-T Vol.VI covers safety issues related to people coming in contact with telecommunication circuits exposed to the induction of AC electric

21、power or AC electrified railway lines. 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 editions indicated were valid. All Recommendations and

22、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 valid ITU-T Recommendations is regularly published. The

23、 reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. IEC 61472 IEC 61472 (2004), Live working Minimum approach distances for a.c. systems in the voltage range 7.5 kV to 800 kV A method of calculation. ICNIRP 1 ICNIRP (2010),

24、 ICNIRP Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic and Electromagnetic Fields (1Hz-100 kHz), Health Physics, Vol. 99, No. 6; pp. 818-836. ICNIRP 2 ICNIRP (2009), ICNIRP guidelines on limits of exposure to static magnetic fields. Health Physics, Vol. 96, No. 4; pp. 504-514. _

25、 1This Recommendation includes an electronic attachment containing the EMFACDC program. 2 Rec. ITU-T K.90 (05/2012) 3 Terms and definitions This Recommendation defines the terms defined in this clause. The definitions are harmonized with those used in b-ITU-T K.52. 3.1 controlled/occupational exposu

26、re: Controlled/occupational exposure applies to situations where the persons are exposed as a consequence of their employment and in which those persons who are exposed have been made fully aware of the potential for exposure and can exercise control over their exposure. Occupational/controlled expo

27、sure also applies where the exposure is of transient nature as a result of incidental passage through a location where the exposure limits may be above the general population/uncontrolled limits, as long as the exposed person has been made fully aware of the potential for exposure and can exercise c

28、ontrol over his or her exposure by leaving the area or by some other appropriate means. 3.2 energized: Electrically connected to a source of potential difference or electrically charged so as to have a potential different from that of the earth. 3.3 exposed: Not isolated or guarded. 3.4 general publ

29、ic: All non-workers (see definition of workers in clause 3.9) are defined as the general public. 3.5 general population/uncontrolled exposure: General population/uncontrolled exposure applies to situations in which the general public may be exposed or in which persons who are exposed as a consequenc

30、e of their employment may not be made fully aware of the potential for exposure or cannot exercise control over their exposure. 3.6 minimum air insulation distance (MAID) (DU): The shortest distance between an energized electrical apparatus and/or workers body at different potential. With a floating

31、 electrode in the gap, it is equal to or greater than the sum of the individual maximum air insulation distance. This is an electrical quantity and does not include an ergonomic factor for inadvertent movement. 3.7 minimum approach distance (MAD) (DA): The minimum air insulation distance plus an erg

32、onomic distance to account for inadvertent movement. 3.8 sparkover: A disruptive discharge between preset electrodes in either a gaseous or a liquid dielectric. 3.9 workers: Persons employed by an employer, including trainees and apprentices but excluding domestic servants. 4 Abbreviations and acron

33、yms This Recommendation uses the following abbreviations and acronyms: AC Alternating Current DC Direct Current EMF Electromagnetic Field MAD Minimum Approach Distance MAID Minimum Air Insulation Distance NESC National Electrical Safety Code RMS Root Mean Square Rec. ITU-T K.90 (05/2012) 3 5 General

34、 principles There are three hazards to workers working near energized power lines. They are: 1 exposure to power-frequency magnetic fields; 2 exposure to power-frequency electric fields; 3 possibility of sparkover between the exposed energized conductor and the workers body or tool held by the worke

35、r. Typically, the risk from these hazards recedes rapidly as the separation between the worker and the power conductor increases. The following subclause describes these in more detail. 5.1 Field exposure limits The relevant quantities for the power frequency exposure limit for human beings are the

36、electric field and the magnetic field. Electric field is expressed in units of V/m. Magnetic field can be expressed as a magnetic flux density B or as magnetic field strength H. In vacuum and in air they are related by the expression: HB0= where 70104= H/m is the permeability of free space. One set

37、of limits for electric and magnetic field exposure at power frequencies have been provided by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) (ICNIRP 1, ICNIRP 2). In certain cases local or national regulatory agencies or standards bodies may promulgate magnetic field and

38、electric field exposure limits at power frequencies. If such limits exist they should be used. If local or national limits at power frequencies do not exist, ICNIRP guidelines limits should be used. The majority of documents providing guidelines to EMF exposure limits, including ICNIRP, use a two-ti

39、er limit structure where lower levels are specified for uncontrolled/general public exposure and upper levels for controlled/occupational exposure. ICNIRP and other similar documents provide safety limits in terms of basic restrictions and reference (or derived) levels. The basic restrictions addres

40、s the fundamental quantities that determine the physiological response of the human body to electromagnetic fields. Basic restrictions apply to a situation with the body present in the field. As the basic quantities are difficult to measure directly, most documents provide derived (reference) levels

41、 for electric field, magnetic field and power density. Reference levels may be exceeded if the exposure condition can be shown to be within the basic restrictions. The reference levels apply to a situation where the electric or magnetic field is not influenced by the presence of a body. 5.1.1 ICNIRP

42、 limits 5.1.1.1 DC limits Whole-body continuous occupational exposure during the work-day should be limited to a time-weighted average magnetic flux density not exceeding 200 mT (approximately 160 kA/m in free space). Continuous exposure of the general public should not exceed a magnetic flux densit

43、y of 40 mT (approximately 32 kA/m in free space). People with cardiac pacemakers and implantable defibrillators should avoid locations where magnetic flux density exceeds 0.5 mT (approximately 400 A/m in free space) ICNIRP 2. The magnetic fields are assumed to emanate from power system conductors. S

44、ince network operator personnel are not employees of the power system operator, the exposure limits for the general public should be applied to network operator personnel. 4 Rec. ITU-T K.90 (05/2012) 5.1.1.2 Limits at 50/60 Hz The basic restrictions for occupational and for general public exposure a

45、t 50/60 Hz are defined in ICNIRP 1 concerning the frequency range 1 Hz-100 kHz. They are based on the analysis of the risks coming from transient nervous system responses including peripheral (PNS) and central nerve stimulation (CNS), the induction of retinal phosphenes and possible effects on some

46、aspects of brain function. In the document the basic restrictions are given in terms of internal electric field and constitute the basis for establishing the reference levels. Reference levels for occupational exposure to time-varying magnetic fields in the frequency range 25-300 Hz are 1.0103T (8.0

47、102Am1). The corresponding limit for the electric field is 5.0102/f kVm1, where f is the frequency in Hz. The relevant values for reference levels at power frequencies are given in Table 1. Reference levels for general public exposure to time-varying magnetic and electric fields in the frequency ran

48、ge 50-400 Hz are, respectively, 2.0104 T (1.6102Am1) and 2.5102/f kVm1, where f is the frequency in Hz. The relevant values for reference levels at power frequencies are given in Table 2. Table 1 Reference levels for occupational exposure Frequency B limit (H limit) mT (Am1) E limit kVm1 50 Hz 1.0 (

49、800) 10 60 Hz 1.0 (800) 8.3 Table 2 Reference levels for general public exposure Frequency B limit (H limit) mT (Am1) E limit kVm150 Hz 0.2 (160) 5 60 Hz 0.2 (160) 4.2 5.2 Exposure zones The area surrounding the current-carrying power conductors can be classified into one of the three following zones. 1) Compliance zone: In the compliance zone, potential exposure to EMF is below the applicable limits for both controlled/occupational exposure and uncontrolled/general public exposure. 2) Occupational zone: I