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  • Prague, 8-11 June 2009

    QUICK AND EFFICIENT METHOD FOR LOW-FREQUENCY EMF EVALUATION

    OF ELECTRIC POWER SYSTEMS CONSIDERING MULTIPLE SOURCES WITH

    DIFFERENT FREQUENCIES AND HARMONICS

    Ernst SCHMAUTZER, Katrin FRIEDL, Maria AIGNER

    Institute of Electrical Power Systems University of Technology, Graz, Austria

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Content

    • Introduction

    • ICNIRP: Reference Levels of ELF EMF (µT, kV/m)

    Basic Restrictions (mA/m², induced current densities)

    • Proposal of the new method:

    Exposition Ratio ER

    Total Exposition Ratio TER

    Harmonic Factor kH for Magnetic and Electric Fields

    • Application of the Proposed Method: Example

    • Conclusion

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Indroduction

    • Aim: Evaluation of electric and magnetic fields according to ICNIRP

    considering several sources with

    different fundamental frequencies including their harmonics.

    • ICNIRP

    – Magnetic and electric fields are individually handled

    – Reference values for different fundamental frequencies

    • General public exposure

    • Occupational exposure

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    0.01

    0.10

    1.00

    10.00

    100.00

    1.000.00

    10.000.00

    100.000.00

    0. 1 1 10 10 0

    10 00

    10 00

    0

    1E +0

    5

    1E +0

    6

    1E +0

    7

    1E +0

    8

    1E +0

    9

    1E +1

    0

    1E +1

    1

    1E +1

    2

    Frequency in Hz

    R ef

    er en

    ce le

    ve l i

    n µT

    o r k

    V/ m

    Reference level for general public exposure B in µT

    Reference level for general public exposure E in kV/m

    Reference Levels for General Public Exposure (ICNIRP)

    10 kV/m, 300 µT … for 16.7 Hz

    FFT

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Classical Approach (ICNIRP)

    Ei … electric field strength at frequency i in Vm-1

    EL,i… electric field reference level at frequency i in Vm-1

    a … 610 Vm-1 for occupational exposure and 87 Vm-1 for general public exposure

    ≤∑ ∑ 65 kHz 10 MHz

    j j

    i=1 Hz i>65 kHzL,j

    H H + 1

    H b

    ≤∑ ∑ 1MHz 10MHz

    i i

    i=1Hz i>1MHzL,i

    E E + 1

    E a

    Hj … magnetic field strength at frequency j in Am-1

    HL,j … magnetic field reference level at frequency j in Am-1

    b … 24.4 Am-1 (30.7 µT) for occupational exposure and 5 Am-1 (6.25 µT) for general public exposure

    Magnetic field

    Electric field

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    0.01

    0.10

    1.00

    10.00

    100.00

    1.000.00

    10.000.00

    100.000.00

    1.000.000.00

    0. 1 1 10 10 0

    10 00

    10 00

    0

    10 00

    0 0

    1E +0

    6

    1E +0

    7

    1E +0

    8

    1E +0

    9

    1E +1

    0

    1E +1

    1

    1E +1

    2

    Frequency in Hz

    R ef

    er en

    ce le

    ve l i

    n µT

    o r

    kV /m

    Reference level for occupational exposure B in µT

    Reference level for occupational exposure E in kV/m

    Reference Levels for Occupational Exposure (ICNIRP)

    30 kV/m, 1500 µT … for 16.7 Hz

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Practical Application of the ICNIRP Guidelines

    • Two Step procedure – Control of the compliance with the reference levels (µT, kV/m)

    – Control of the mandatory compliance with the basic restrictions

    (mA/m², current density in central nervous system, extremities)

    – Target group: Healthy people

    – Pacemaker ?

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Induced current density

    Illustration of magnetic induced electric curl fields (human body) in the horizontal oriented magnetic alternating field

    Position of transversal head cut

    Chest cut

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Classical Approach Reference Levels – Fields Including Harmonics

    ≤∑ ∑ 65 kHz 10 MHz

    j j

    i=1 Hz i>65 kHzL,j

    H H + 1

    H b

    ≤∑ ∑ 1MHz 10MHz

    i i

    i=1Hz i>1MHzL,i

    E E + 1

    E a

    Magnetic field

    Electric field

    0.01

    0.10

    1.00

    10.00

    100.00

    1.000.00

    10.000.00

    100.000.00

    0. 1 1 10 10 0

    10 00

    10 00

    0

    1E +0

    5

    1E +0

    6

    1E +0

    7

    1E +0

    8

    1E +0

    9

    1E +1

    0

    1E +1

    1

    1E +1

    2

    Frequency in Hz

    R ef

    er en

    ce le

    ve l i

    n µT

    o r k

    V/ m

    Reference level for general public exposure B in µT

    Reference level for general public exposure E in kV/m

    0.01

    0.10

    1.00

    10.00

    100.00

    1.000.00

    10.000.00

    100.000.00

    1.000.000.00

    0. 1 1 10 10 0

    10 00

    10 00

    0

    10 00

    0 0

    1E +0

    6

    1E +0

    7

    1E +0

    8

    1E +0

    9

    1E +1

    0

    1E +1

    1

    1E +1

    2

    Frequency in Hz

    R ef

    er en

    ce le

    ve l i

    n µT

    o r k

    V /m

    Reference level for occupational exposure B in µT

    Reference level for occupational exposure E in kV/m

    General Public Exposure

    Occupational Exposure

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Harmonic Factor kH, 16,7Hz (a fingerprint)

    • Based on series of measurements

    • Sum of RMS-values (obtained by FFT)

    • Phaseless approach → 20 % overweighted

    compared to the approchaes including phase information (e.g. 50 Hz HV power grid)

    ∑ ∑ ν

    1

    L,ν

    L,1

    I I

    H H,ν B ν ν B

    k = k =

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    kH Considering Several Frequencies Including Phase Information

    Results of weighting functionsTime course of signal

    FFT

    ( ) ( )ν ν νν ν

    W F A cos Θ + φ 1⋅ ≤∑

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Calculation of the Harmonic Factor kH

    • Linear interrelationship between magnetic flux density and current

    • kH derived by RMS-values of harmonics (FFT)

    j j

    ff f

    ν

    f 1

    B I I = =

    B I I

    ν

    1

    L,ν

    L,1

    I I

    H,B H,B,ν B ν ν B

    k = k =∑ ∑

    ν f Iν Iν/I1 BL,ν BL,ν/BL,1 kH,ν - Hz A % µT % -

    1 50 1000.0 100.00 100.0 100.0 1.000 3 150 0.0 0.00 33.3 33.3 0.000 5 250 7.0 0.70 20.0 20.0 0.035 7 350 7.0 0.70 14.3 14.3 0.049

    ΣkH,ν=kH 1.08

    ν f Iν Iν/I1 BL,ν BL,ν/BL,1 kH,ν - Hz A % µT % -

    1 16.7 350 100.00 300.0 100.0 1.000 3 50.0 0 0.00 100.0 33.3 0.000 5 83.3 3 0.86 60.0 20.0 0.043 7 116.6 3 0.86 42.9 14.3 0.060

    ΣkH,ν=kH 1.10

    B B, 50 Hz H,BER = ER k⋅

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Exposition Ratio ER Applicable for the electric & the magnetic field

    • ER = Ratio of Field Strength / Reference Value

    • ER for one source and one frequency

    • ER for one source and several frequencies

    Examplary situation with three sources

    and a base load

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Exposition Ratio ER

    • One source and one frequency

    • One source and several frequencies

    ⋅ j 0 j j

    B,j L,j 0 L,j L,j

    H μ H B ER = = =

    H μ H B i

    E,i L,i

    E ER =

    E

    ∑ ∑ ∑ 10MHz 10MHz 10MHz

    j j B B,j

    j=1Hz j=1Hz j=1HzL,j L,j

    H B ER = ER = =

    H B ∑ ∑ 10MHz 10MHz

    i E E,i

    i=1Hz i=1Hz L,i

    E ER = ER =

    E

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Total Exposition Ratio TER

    • Considering all sources n & all relevant frequencies

    • Summing up ERB and ERE → TERB and TERE

    • Total Exposition Ratio for the Magnetic Field

    • Total Exposition Ratio for the Electric Field

    ∑B B n

    TER = ER

    ∑E E n

    TER = ER

  • Prague, 8-11 June 2009

    Schmautzer-Austria Session 2 Paper 0627

    Example

    Start

    Identification of influencing sources

    Railway Overhead power line Cable Base load

    Normalized expositon ratio for the fundamental frequency at the imission point Pi

    ERB,Source,ff,(Pi)

    ERB, Sour

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