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

Email: brian_chan@ieee.org 28 May 2010

Technical ForumOverview and Latest Development of Standards in Human Exposure to Electromagnetic Fields (EMF)

1Hong Kong Chapter Hong Kong Chapter

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)

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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. 494-522, in 1998.

• Objective : To establish guidelines for limiting EMF exposure that will provide protection against known adverse health effects.

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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).

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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/m2)

• Specific Absorption Rate– The rate at which energy is absorbed in body tissues. (W/kg2)

• Power Density – the power per unit area normal to the direction of propagation.

(W/m2). 10GHz to 300GHz. E.g. in far field

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2ESAR

EJ

22

377377

HSorE

SorHES

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Near field and Far Field expsoures

• Near field exposure (e.g. Mobile phone, handheld devices)

– E.g. Specific absorption rate, SAR (W/kg)

• Far field exposure

– Electric field density, E (V/m)

– Magnetic field density, H (A/m)

– Magnetic flux density, B (T)

– Power density, S (W/ m2)

|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.

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Safety limitsCurrent density, SAR, and Power density

Example of Current density SAR limit in ICNIRP Guideline

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Safety Limits E, H, B and S

• ICNIRP

– Occupational & General public

Example of E – field limit in ICNIRP Guideline

The Electromagnetic Spectrum

• Non-ionizing radiation

Relative lower energy

Confirmed health effect is thermal in nature

9Reference : http://dev2.real.co.za/Content/images/electro_diag.jpg

Non-ionizing radiation

Relative lower energy

Confirmed health effect is thermal in nature

Ionizing radiation

Sufficient energy to cause alteration in atomic structure

Confirmed adverse effect is genetic damage

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

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APPLICATION OF ICNIRP GUIDELINE

POWER DELIVERY1. SUBSTATION

2. OVERHEAD LINE & POWER CABLE

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Review on Power Delivery Systems

(e.g. 400 kV or 132 kV)

(e.g. 11 kV )

Example for IFC Hong Kong• Power Generating Station

• Substation

• Overhead line, 50 Hz

• Underground Cable

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Case 1 : Power frequency magnetic field radiation in power substation

Zone station

Substation

Case 1: Common 3-Phase Cable Configurations

Trefoil configuration Flat configuration

B

B

0

120

240

240

120

0

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. 1042-1048.

Cable

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Case 1: Power frequency magnetic field radiation in power substation

Ground floor

Transformer Substation

3 phase busbars

1/F Office

Magnetic field pick up coil

ICNIRP Guidelines on Human Exposure under Power Frequency Magnetic Field Radiations

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. 494-552, April 1998.

At 50Hz, B-field limit =100μT

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Case 1: Power frequency magnetic field radiation in power substation

• ICNIRP limit at 50 Hz

– 100μT

Location 16 is just above the power substation at the ground floor

Maximum magnetic flux is 277μT at location 16

Measured B-field at Location 16

0

50

100

150

200

250

300

0 100 200 300 400 500 600

Frequency (Hz)

B-f

ield

(dB

/uT

)

Over the limit by 2.77 times

Case 2: Magnetic Field Radiation of 3-phase cable in High-rise building

Over head Lines High-rise Building

Cable Characteristics

Extremely High Voltagee.g. 400kV, 132kV

High voltage & High currente.g. 11kV & up to 1000A

Radiations Electric Field Magnetic Field ( due to high current)

Orientation Horizontal Vertical

Aspects of high voltage cables in OverHead Lines as compared to in High-rise Building

Case 2 - Cable Arrangement & Human Body Model

Figure of Case 1Different arrangements of the

current conductor

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. LeungA Study on Human Exposure to Power Frequency Radiation in High-Rise Buildings2011 Asia-Pacific Symposium on EMC, Jeju Island, Korea

Case 1 2 3 4

Max B-field 230T (170) 130T(105) 46T(96) 70T(96)

Flat Configuration Trefoil Configuration

Case 2: Magnetic field distribution

Over the ICNIRP Limit at when 1m away from the 3-phase cable

Case 2: Typical Measurement of H-field inside a typical high-rise building in Hong Kong

Location

Magnetic-field Strength

( μT )

Floor

level

1m above

floor level

1 16.0 10.1

2 32.7 16.6

3 39.8 /

4 30.2 20.0

5 44.7 14.1

Office floor, 1 floor below the transformer room

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 buildingTo be published in European Transactions on Electric Power

APPLICATION OF ICNIRP GUIDELINE

MOBILE COMMUNICATIONS 3. BASE STATION

4. MOBILE PHONE

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

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Case 3. RFI from Base Stations –

Feb. 2007Feb. 2009

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Case 3. RF radiation from mobile phone base stationA Real Case

• Mobile base stations are located next to a residential building.

• Concern of RF exposure.

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

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Only 1 % of the ICNIRP limit.

Distance from 3 m 15 m 30 m 124 m 300 m transmission source

Power density .00004 mW .00006 mW .00004 mW .00002 mW .00013 mWper square meter*

Number of times below 13,750 9,167 13,750 27,500 4,230internationally recognized safety standards**

Case 3. Estimation on Radiation from Base Station Tower

*1 milliwatt (mW) = 1/1,000 watt**The ANSI/IEEE and NCRP safety standards for the general public in theenvironment depicted above are .550 milliwatts per square centimeter (5.5 watts per meter).ICNIRP limit = 2 watts per meter.

40 m

20 Channels10 Watts/Channel

Abstract from RF Bioeffect Research To Address Human Safety Concerns By Dr. C K Chou, 6 Nov 2007

Case 4. Mobile phoneSAR 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.

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The SAR induced in the human body can be changed under different environment.

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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– 10.29 Million

• ~16 hours of simulation time

• Time step– 1.0563 x 10-12s

• Simulation boundary– Perfect Matching Layer (PML)

– 2nd Order Mur Absorbing Boundary Condition (ABC)

Simulation boundaryC. 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. 2207-2210, August 2008.

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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 enclosure 31

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Human exposure inside metallic elevator from mobile phone radiation - SAR

• Localized Peak SAR and Whole body average SAR values

Over the safety limit of

0.08 W/kg by 3.8%

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.

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 (copper) Window (glass)

Relative Permittivity (εr) 1 8

Conductivity (σ) 1 x 107 S/m 0 S/m

Casing

Window

Head

Body

Mobile

Human exposure inside Vehicle from mobile phone radiation – Field Distributions

E.g. Five Passengers – Max SAR:

Left Hand User Right Hand User

0.044W/kg(0.96%)

0.050W/kg(1.09%)

0.044W/kg(1.39%)

4.590W/kg0.082W/kg

0.149W/kg(3.35%)

0.062W/kg(1.39%)

0.030W/kg(0.68%)

4.443W/kg0.220 W/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. 706-711

0.082W/kg(1.79%)

0.220 W/kg(4.94%)

APPLICATION OF ICNIRP GUIDELINE

WIRELESS COMMUNICATIONS

5. WIFI

6. RFID

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Case 5. RFI Wi-Fi systems

Feb. 2007

Case 5. Measurement of WIFI Radiations in General Public

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Locations Freq (GHz) E (V/m) S (W/m2)

Lan Kwai Fong – Café 2.44 0.11 33.22

Wellington Street – Café 2.41 0.14 54.93

Admiralty – Food Court 2.46 0.02 1.07

Causeway Bay – Shopping Mall– Café

2.462.45

0.040.17

3.5776.97

Departure Hall, Aiport – Public Area– Café

2.412.44

0.020.05

1.476.13

PolyU – Canteen 2.45 0.06 9.75

CityU – Podium 2.41 0.02 1.47

Residential area – Living Room– 50cm away from router

2.432.44

0.370.59

355.87918.41

ICNIRP Limit 2.45 61 10 x 106

Less than 1 % of ICNIRP Limit!!

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Case 6. RFI - RFID systems

Feb. 2007

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Case 6. RF radiation from RFID systems

• RFID systems at Chek Lap Kok Airport was installed in 2005.

• RFID systems for reading tags on luggage– >200 RFID readers– >500 RFID antennas

• Frequency– 920-925 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. 924-928, April 2007.

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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– 0.00294 V/m at

920.3 MHz• 0.003% of occupational

exposure limit • 0.007% of general

public exposure limit

0.00294 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. 924-928, Apr. 2007.

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…

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Thank you!

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