Real-life Applications of ICNIRP Guidelines to Various Human EMF Exposure Issues

Transcription

1 Technical Forum Overview and Latest Development of Standards in Human Exposure to Electromagnetic Fields (EMF) Real-life Applications of ICNIRP Guidelines to Various Human EMF Exposure Issues Dr. Brian K H Chan Department of Electronic Engineering City University of Hong Kong brian_chan@ieee.org 28 May 2010 Hong Kong Chapter Hong Kong Chapter 1

2 Outline Background ICNIRP Guidelines Current Density, SAR, Power Density, E/H-field Applications of ICNIRP Guidelines Power Delivery Substation, OverHead line & Cable (in power Freq range) Mobile Communication Base Station, Mobile Phone (in MHz/GHz Freq Range) Wireless Communication Wifi, RFID (in MHz/GHz Freq Range) 2

3 ICNIRP Guidelines Guidelines for limiting exposure to time varying electric, magnetic, and electromagnetic fields (up to 300 GHz) by International Commission on Non-Ionizing Radiation Protection Published in Health Physics volume 74, number 4, page , in Objective : To establish guidelines for limiting EMF exposure that will provide protection against known adverse health effects. 3

4 ICNIRP Guideline Two classes of guidance Basic Restrictions Restrictions on time-varying electric, magnetic, and electromagnetic fields that are directly established health effects Specified physical quantities: Current density (J), specific energy absorption rate (SAR), power density (P). Reference levels Provide for practical exposure assessment propose to determine whether the basic restrictions are likely to be exceeded. By measurement and computation. Derived quantities: Electric field density (E), magnetic field density (H), magnetic flux density (B), power density (P). 4

5 Current Density, Specific Absorption Rate, and Power Density Current Density A vector of which the integral over a given surface is equal to the current flowing through the surface. (A/m 2 ) J E Specific Absorption Rate The rate at which energy is absorbed in body tissues. (W/kg 2 ) SAR 2 E Power Density the power per unit area normal to the direction of propagation. (W/m 2 ). 10GHz to 300GHz. E.g. in far field S E H or S 2 E 377 or S 377H 5 2

6 Near field and Far Field expsoures Near field exposure (e.g. Mobile phone, handheld devices) E.g. Specific absorption rate, SAR (W/kg) E (V/m) is the rms value of electric field strength, σ (S/m) and ρ(g/cm3) are the conductivity and the mass density of human tissue. Far field exposure Electric field density, E (V/m) Magnetic field density, H (A/m) Magnetic flux density, B (T) Power density, S (W/ m 2 ) 6

7 Safety limits Current density, SAR, and Power density Example of Current density SAR limit in ICNIRP Guideline 7

8 Safety Limits E, H, B and S ICNIRP Occupational & General public Example of E field limit in ICNIRP Guideline 8

9 The Electromagnetic Spectrum Non-ionizing radiation Relative lower energy Confirmed health effect is thermal in nature Non-ionizing radiation Ionizing radiation Relative lower energy Sufficient energy to cause alteration Confirmed health effect is in atomic structure thermal in nature Confirmed adverse effect is genetic damage Reference : 9

10 Applications of ICNICP Guidelines covered in this talk Power Delivery 1. Substation 2. Overhead Line & Power Cable Mobile Communications 3. Base Station 4. Mobile Phone Wireless Communications 5. Wi-Fi 6. RFID 10

11 APPLICATION OF ICNIRP GUIDELINE POWER DELIVERY 1. SUBSTATION 2. OVERHEAD LINE & POWER CABLE 11

12 Review on Power Delivery Systems Example for IFC Hong Kong Power Generating Station Substation Overhead line, 50 Hz Underground Cable (e.g. 400 kv or 132 kv) (e.g. 11 kv )

13 Case 1 : Power frequency magnetic field radiation in power substation Zone station Substation 13

14 Case 1: Common 3-Phase Cable Configurations 120 B 240 B Cable Trefoil configuration Flat configuration Reference: Federico Moro and Roberto Turri, Fast Analytical Computation of Power-Line Magnetic Fields by Complex Vector Method, IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 23, NO. 2, APRIL 2008, pp

15 Case 1: Power frequency magnetic field radiation in power substation 1/F Office Magnetic field pick up coil Ground floor Transformer Substation 3 phase busbars 15

16 ICNIRP Guidelines on Human Exposure under Power Frequency Magnetic Field Radiations At 50Hz, B-field limit =100μT Reference: ICNIRP Safety Guideline, Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic, and Electro- magnetic fields (up to 300 GHz), Health Physics, Vol. 74, no. 4., pp , April 1998.

17 B-field (db/ut) Case 1: Power frequency magnetic field radiation in power substation ICNIRP limit at 50 Hz 100μT Over the limit by 2.77 times Measured B-field at Location Frequency (Hz) Maximum magnetic flux is 277μT at location 16 Location 16 is just above the power substation at the ground floor 17

18 Case 2: Magnetic Field Radiation of 3-phase cable in High-rise building Aspects of high voltage cables in OverHead Lines as compared to in High-rise Building Over head Lines High-rise Building Cable Characteristics Extremely High Voltage e.g. 400kV, 132kV High voltage & High current e.g. 11kV & up to 1000A Radiations Electric Field Magnetic Field ( due to high current) Orientation Horizontal Vertical

19 Case 2 - Cable Arrangement & Human Body Model Different arrangements of the current conductor Figure of Case 1

20 Case 2: Free Space induced B-field for different configurations of 3-phase cable Based on Biot-Savart Law and Superposition theorem. When d increase, B-field decrease Flat configurations induce higher radiated B-field than that of Trefoil Arrangement. Minimum Safety Distance for satisfying the ICNIRP limit Flat configuration =1.6m Trefoil configuration = 1m Reference: K. H. Chan and S. W. Leung A Study on Human Exposure to Power Frequency Radiation in High-Rise Buildings 2011 Asia-Pacific Symposium on EMC, Jeju Island, Korea

21 Case 2: Magnetic field distribution Case Max B-field 230 T (170) 130 T(105) 46 T(96) 70 T(96) Flat Configuration Trefoil Configuration Over the ICNIRP Limit at when 1m away from the 3-phase cable

22 Case 2: Typical Measurement of H-field inside a typical high-rise building in Hong Kong Office floor, 1 floor below the transformer room Location Magnetic-field Strength ( μt ) Floor level 1m above floor level / Measured maximum B-field strength = 44.7μT at 1.3m away from the VCB It is below the recommended limit by ICNIRP Guideline!! Reference: S. W. Leung, K. H. Chan and L. C. Fung Investigation of power frequency magnetic field radiation in typical high-rise building To be published in European Transactions on Electric Power

23 APPLICATION OF ICNIRP GUIDELINE MOBILE COMMUNICATIONS 3. BASE STATION 4. MOBILE PHONE 23

24 Case 3. Base Station: Far Field Radiation from mobile phone base station 24

25 Case 3. RFI from Base Stations Feb Feb

26 Case 3. RF radiation from mobile phone base station A Real Case Mobile base stations are located next to a residential building. Concern of RF exposure. 26

27 Radiation E-field measurement from Mobile Phone Base Station Various locations in the residual building Maximum E-field < 0.4V/m from GSM900 BS < 0.6 V/m from PCS1800 BS Only 1 % of the ICNIRP limit. 27

28 Case 3. Estimation on Radiation from 20 Channels 10 Watts/Channel Base Station Tower 40 m Distance from 3 m 15 m 30 m 124 m 300 m transmission source Power density mw mw mw mw mw per square meter* Number of times below 13,750 9,167 13,750 27,500 4,230 internationally recognized safety standards** *1 milliwatt (mw) = 1/1,000 watt **The ANSI/IEEE and NCRP safety standards for the general public in the environment depicted above are.550 milliwatts per square centimeter (5.5 watts per meter). ICNIRP limit = 2 watts per meter. Abstract from RF Bioeffect Research To Address Human Safety Concerns By Dr. C K Chou, 6 Nov 2007

29 Case 4. Mobile phone SAR of Mobile Phone in Hong Kong Maximum S.A.R. Values in W/kg ** (based on ICNIRP Guideline) Safety limit = 2 W/kg (based on ANSI/IEEE Standard) Safety limit = 1.6 W/kg ** The maximum S.A.R. values are extracted from the relevant test reports provided by the equipment suppliers. The SAR induced in the human body can be changed under different environment. 29

30 Case 4. Human exposure inside metallic elevator from mobile phone radiation simulation model In the FDTD models, non-uniform meshing is applied to reduce the simulation space and also the computational resources and time. FDTD models Human model Mobile phone model Elevator model Total cells Million ~16 hours of simulation time Time step x s Simulation boundary Perfect Matching Layer (PML) 2nd Order Mur Absorbing Boundary Condition (ABC) C. K. Tang, K. H. Chan, L. C. Fung, and S. W. Leung, Effect on Radio Frequency human exposure of mobile phone inside an enclosed metallic elevator, Microwave and Optical Technology Letters, vol. 50, no. 8, pp , August Simulation boundary 30

31 Case 4. Human exposure inside metallic elevator from mobile phone radiation Electric field distribution Time-domain electric field animation Free space Type I Type II Type III Full enclosure31 31

32 Human exposure inside metallic elevator from mobile phone radiation - SAR Localized Peak SAR and Whole body average SAR values This brings safety out the importance of whole-body exposure in human inside an elevator which usually has not been considered for mobile phone application. Over the safety limit of 0.08 W/kg by 3.8% 32

33 Human exposure inside Vehicle from mobile phone radiation simulation model The Vehicle is mainly made of metallic materials, and glasses The FDTD modeling consists of 227 x 299 x 189 = 12,827,997 cells Cell Size The largest cell is 8mm x 8mm x 8mm The smallest cell is 0.5mm x 0.5mm x 1mm Front and Rear parts of the vehicle are omitted Casing Window Head Body Mobile Casing (copper) Window (glass) Relative Permittivity (εr) 1 8 Conductivity (σ) 1 x 10 7 S/m 0 S/m

34 Human exposure inside Vehicle from mobile phone radiation Field Distributions E.g. Five Passengers Max SAR: 0.030W/kg (0.68%) 0.062W/kg (1.39%) 0.149W/kg (3.35%) 0.044W/kg (1.39%) 0.050W/kg (1.09%) 0.044W/kg (0.96%) W/kg 4.443W/kg (4.94%) Left Hand User 0.082W/kg (1.79%) Right Hand User 4.590W/kg K.H. Chan, S. W. Leung, Y. M. Siu, Specific absorption rate evaluation for people using wireless communication device in vehicle 2010 IEEE International Symposium on Electromagnetic Compatibility, pp

35 APPLICATION OF ICNIRP GUIDELINE WIRELESS COMMUNICATIONS 5. WIFI 6. RFID 35

36 Case 5. RFI Wi-Fi systems Feb

37 Case 5. Measurement of WIFI Radiations in General Public Locations Freq (GHz) E (V/m) S ( W/m 2 ) Lan Kwai Fong Café Wellington Street Café Admiralty Food Court Causeway Bay Shopping Mall Café Departure Hall, Aiport Public Area Café PolyU Canteen CityU Podium Residential area Living Room 50cm away from router ICNIRP Limit x 10 6 Less than 1 % of ICNIRP Limit!! 37

38 Case 6. RFI - RFID systems Feb

39 Case 6. RF radiation from RFID systems RFID systems at Chek Lap Kok Airport was installed in RFID systems for reading tags on luggage >200 RFID readers >500 RFID antennas Frequency MHz Max. EIRP of 4W The systems located close to the workers (~0.3 to 5 m) Human safety concern L. C. Fung, K. H. Chan, W. K. Lam, S. W. Leung, Y. F. Wong, P. W. K. Wu, and C. K. Tang, Electromagnetic Assessment on Human Safety of RFID system at Hong Kong International Airport, Microwave and Optical Technology Letters, vol. 49, no. 4, pp , April

40 Case 6. RF radiation from RFID systems ICNIRP guidelines Occupational 91 V/m at 920 MHz General public 41.7 V/m at 920 MHz Max. E-field recorded V/m at MHz 0.003% of occupational exposure limit 0.007% of general public exposure limit V/m L. C. Fung, K. H. Chan, S. W. Leung, Y. F. Wong, P. W. K. Wu, and C. K. Tang, Electromagnetic assessment on human safety of RFID system at Hong Kong International Airport, Microwave and Optical Technology Letters, vol. 49, issue. 4, pp , Apr

41 Conclusions The ICNIRP guidelines is to protect any adverse health effect, based on the scientific literature review. The ICNIRP guidelines has already applied in various aspects in our daily lives. e.g. power line, substations, mobile phone and station, wifi systems, etc 41

42 Thank you! 42