1、BRITISH STANDARDBS EN 50475:2008Basic standard for the calculation and the measurement of human exposure to electromagnetic fields from broadcasting service transmitters in the HF bands (3 MHz 30 MHz)ICS 13.280; 17.220.20; 33.170g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40
2、g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 50475:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 September 2008 BSI 2008ISBN 978 0 580 56858 9N
3、ational forewordThis British Standard is the UK implementation of EN 50475:2008.The UK participation in its preparation was entrusted to Technical Committee GEL/106, Human exposure to low frequency and high frequency electromagnetic radiation.A list of organizations represented on this committee can
4、 be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments/corrigenda issued since publ
5、icationDate CommentsEUROPEAN STANDARD EN 50475 NORME EUROPENNE EUROPISCHE NORM June 2008 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050
6、Brussels 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 50475:2008 E ICS 13.280 English version Basic standard for the calculation and the measurement of human exposure to electromagnetic fields from broadcasting service tra
7、nsmitters in the HF bands (3 MHz - 30 MHz) Norme de base pour le calcul et la mesure de lexposition humaine aux champs lectromagntiques des metteurs de service de radiodiffusion dans les bandes HF (3 MHz 30 MHz) Grundnorm fr die Berechnung und Messung der Exposition von Personen gegenber elektromagn
8、etischen Feldern von Rundfunksendern in den KW-Bndern (3 MHz bis 30 MHz) This European Standard was approved by CENELEC on 2008-04-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a nation
9、al standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in
10、any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czec
11、h Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. EN 50475:2008 2 Foreword This European St
12、andard was prepared by the Technical Committee CENELEC TC 106X, Electromagnetic fields in the human environment. The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50475 on 2008-04-01. The following dates were fixed: latest date by which the EN has to be impleme
13、nted at national level by publication of an identical national standard or by endorsement (dop) 2009-04-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2011-04-01 _ BS EN 50475:2008 3 EN 50475:2008 Contents 1 Scope . 5 2 Normative references. 5 3 Ter
14、ms and definitions 5 4 Physical quantities and units 7 5 Applicability of compliance assessment methods . 8 5.1 Reference level or action level values . 8 5.2 SAR and current density 8 6 SAR measurement and calculation (local and average SAR) . 9 6.1 Approximate method for SAR calculation for freque
15、ncies below body resonance 9 6.2 Exposure situation . 9 6.3 Polynomial expansion of “static” component values with frequency .10 7 Current density (3 MHz 10 MHz) 11 8 Measurement of electric and magnetic field .12 9 Calculation of electric and magnetic field .12 10 Contact currents measurement and c
16、alculation .12 10.1 Generalities 12 10.2 Constraints .12 10.3 Equipment 13 10.4 Equivalent body impedance .13 11 Induced current calculation and measurement (10 MHz 30 MHz) 14 11.1 Induced current calculation 14 11.2 Relation between induced current and local SAR .14 11.3 Induced current measurement
17、 .14 Annex A (informative) Data for absorption by the Visible Human body model .15 Annex B (informative) Compliance boundary examples .19 Bibliography 21 BS EN 50475:2008EN 50475:2008 4 Figures Figure 1 Contact current measurement 13 Figure 2 Equivalent body impedance . 13 Figure A.1 Calculated whol
18、e-body SAR values for the displayed polarisation for the inhomogeneous Visible Human body model on conducting ground using currently-accepted values for relative permittivity and conductivity at each frequency 15 Figure A.2 Corresponding polarised E- and H-component parts of the whole-body SAR . 15
19、Figure A.3 Model of the antenna considered . 17 Figure A.4 Plot of the SAR calculated on the basis of the model of Visible Human on the basis of calculated field strengths of the electric and magnetic field in front of the studied short wave curtain antenna 18 Figure B.1 Model of the antenna conside
20、red . 19 Figure B.2 Plot of the E-field strength calculated on NEC-2 basis in front of a short wave curtain antenna . 20 Figure B.3 Plot of the H-field strength calculated on NEC-2 basis in front of a short wave curtain antenna . 20 Tables Table 1 Assessment methods for each antenna region 8 Table 2
21、 Assessment methods for each antenna region 8 Table A.1 Whole-body specific absorption rate for the inhomogeneous Visible Human body model on conducting ground for the different plane-wave polarisation orientations 16 Table A.2 “Static” components of the whole-body specific absorption rate for the i
22、nhomogeneous Visible Human body model on conducting ground for the different plane-wave polarisation orientations. 16 Table A.3 Polynomial expansion coefficients with respect to frequency for the static components of the whole-body specific absorption rate for the inhomogeneous Visible Human body mo
23、del on conducting ground . 17 BS EN 50475:2008 5 EN 50475:2008 1 Scope This standard applies to short wave broadcast transmitters and installations operating in the frequency range 3 MHz to 30 MHz. The objective of the standard is to specify, for such a frequency band, basic information allowing the
24、 definition of a method for assessment of compliance related to human exposure to radio frequency electromagnetic fields. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undate
25、d references, the latest edition of the referenced document (including any amendments) applies. EN 50413, Basic standard on measurement and calculation procedures for human exposure to electric, magnetic and electromagnetic fields (0 Hz 300 GHz) EN 55016 series, Specification for radio disturbance a
26、nd immunity measuring apparatus and methods (CISPR 16 series) ENV 13005:1999, Guide to the expression of uncertainty in measurement 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 action values the magnitude of directly measurable parameters,
27、 provided in terms of electric field strength (E), magnetic field strength (H), magnetic flux density (B) and power density (S), at which one or more of the specified measures in 2004/40/EC 2 must be undertaken. Compliance with these values will ensure compliance with the relevant exposure limit val
28、ues of 2004/40/EC 2 3.2 antenna device that serves as a transducer between a guided wave (e.g. coaxial cable) and a free space wave, or vice versa 3.3 basic restriction restrictions on exposure to time-varying electric, magnetic, and electromagnetic fields that are based directly on established heal
29、th effects as given in 1999/519/EC 1 3.4 broadcasting service radio communication service in which the transmissions are intended for direct reception by the general public. This service may include sound transmissions, television transmissions or other types of transmission 3.5 compliance distance
30、minimum distance from the antenna to a point of investigation where field level is deemed to be compliant to the limits BS EN 50475:2008EN 50475:2008 6 3.6 compliance boundary surface around the antenna outside of which all field levels are deemed to be compliant to the limits 3.7 contact current (I
31、C) contact current between a person and an object exposed to the field, is expressed in amperes (A). A conductive object in an electric field can be charged by the field 3.8 current density (J) current density is defined as the current flowing through a unit cross section perpendicular to its direct
32、ion in a volume conductor such as the human body or part of it, expressed in amperes per square meter (A/m) 3.9 electric field strength (E) magnitude of a field vector at a point that represents the force (F) on a positive small charge (q) divided by the charge qFE = Electric field strength is expre
33、ssed in units of volt per meter (V/m) 3.10 exposure limit values limits on exposure to electromagnetic fields as given in 2004/40/EC 2 which are based directly on established health effects and biological considerations. Compliance with these limits will ensure that workers exposed to electromagneti
34、c fields are protected against all known adverse health effects 3.11 induced current current induced inside the body as a result of direct exposure to electromagnetic fields, expressed in the unit ampere (A) 3.12 installation a particular combination of several types of apparatus and, where applicab
35、le, other devices, which are assembled, installed and intended to be used permanently at a predefined location. In this standard, installation includes at least one short wave transmitter 3.13 magnetic field strength (H) vector quantity obtained at a given point by subtracting the magnetization M fr
36、om the magnetic flux density B divided by the permeability of free space 0BH M=0Magnetic field strength is expressed in the unit ampere per metre (A/m) NOTE In vacuum, the magnetic field strength is at all points equal to the magnetic flux density divided by the permeability of free space: H = B / 0
37、3.14 modulation process by which a quantity that characterises an oscillation or wave is constrained to follow the values of a characteristic quantity of a signal NOTE Two modulations, in particular, are used for this standard: AM (Amplitude Modulation) and COFDM (Coded Orthogonal Frequency Division
38、 Multiplex); it must also be taken into consideration when carrying out measurements and calculations to determine whether or not the limits are being exceeded by adding the modulation factor to the carrier r.m.s. value. BS EN 50475:2008 7 EN 50475:2008 3.15 reference levels reference levels of expo
39、sure are provided by 1999/519/EC 1 for comparison with measured values of physical quantities; compliance with all reference levels will ensure compliance with basic restrictions. If measured values are higher than reference levels, it does not necessarily follow that the basic restrictions have bee
40、n exceeded, but a more detailed analysis is necessary to assess compliance with the basic restrictions 3.16 root-mean-square (r.m.s.) r.m.s. value is obtained by taking the square root of the average of the square of the value of the periodic function taken throughout one period 3.17 shortwave broad
41、casting the frequency band between 3 MHz and 30 MHz is called the short wave band. Broadcast transmission in this frequency range is therefore called shortwave broadcasting 3.18 site area including a short wave installation and with restricted access for public 3.19 specific absorption rate (SAR) ti
42、me derivative of the incremental energy (dW) absorbed by (dissipated in) an incremental mass (dm) contained in a volume element (dV) of given mass density (): =dVdWdtddmdWdtdSAR SAR is expressed in units of watt per kilogram (W/kg) 3.20 transmitter device to generate radio frequency power for the pu
43、rpose of communication 4 Physical quantities and units The internationally accepted SI-units are used throughout the standard. Quantity Symbol Unit Dimensions Current density J ampere per square meter A/m Electric field strength E volt per meter V/m Frequency f hertz HzMagnetic field strength H ampe
44、re per meter A/m Specific absorption rate SAR watt per kilogram W/kg Wavelength meter mElectric conductivity siemens per meter S/m Mass density kilogram per cubic meter kg/m BS EN 50475:2008EN 50475:2008 8 5 Applicability of compliance assessment methods In short wave broadcasting services, horizont
45、ally polarized, there are two field regions at the ground level (the far field region does not exist at ground level): the reactive near-field region; this region is defined by r /4 where r is the distance from the antenna to the point of investigation; the radiating near-field; this region is defin
46、ed by r /4 where r is the distance from the antenna to the point of investigation. This standard describes measurement and calculation methods to define the exposure areas and the next tables (Table 1 and Table 2) will help to select an appropriate method. Compliance of the results of the assessment
47、 with the appropriate reference level or action value will ensure compliance with the relevant limit (basic restriction or exposure limit value). However, it is always possible to test compliance directly with regards to basic restriction or exposure limit values, both expressed in SAR and current d
48、ensity. 5.1 Reference level or action level values Table 1 Assessment methods for each antenna region Assessment methods for each antenna region Reactive near field Radiating near field E and H field calculation Induced currents calculation aContact current calculation H field calculation Induced cu
49、rrents calculation aE and H field measurement Induced currents measurement aContact current measurement H field measurement Induced currents measurement aaCompliance of maximum value of E or H field to relevant level, without spatial averaging, gives conformity to induced current. 5.2 SAR and current density Table 2 Assessment methods for each antenna region Assessment methods for each antenna region Reactive near field Radiating near field SAR and
