Transcript

Prague, 8-11 June 2009

QUICK AND EFFICIENT METHOD FORLOW-FREQUENCY EMF EVALUATION

OF ELECTRIC POWER SYSTEMSCONSIDERING 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 10 100

1000

1000

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

Ref

eren

ce le

vel i

n µT

or k

V/m

Reference level for generalpublic exposure B in µT

Reference level for generalpublic exposure E in kV/m

Reference Levels forGeneral 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 10 100

1000

1000

0

1000

00

1E+0

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1E+0

7

1E+0

8

1E+0

9

1E+1

0

1E+1

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1E+1

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Frequency in Hz

Ref

eren

ce le

vel i

n µT

or

kV/m

Reference level foroccupational exposure B inµT

Reference level foroccupational exposure E inkV/m

Reference Levels forOccupational 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 ApproachReference 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 10 100

1000

1000

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

Ref

eren

ce le

vel i

n µT

or k

V/m

Reference level for generalpublic exposure B in µT

Reference level for generalpublic 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 10 100

1000

1000

0

1000

00

1E+0

6

1E+0

7

1E+0

8

1E+0

9

1E+1

0

1E+1

1

1E+1

2

Frequency in Hz

Ref

eren

ce le

vel i

n µT

or k

V/m

Reference level foroccupational exposure B inµT

Reference level foroccupational exposure E inkV/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 includingphase information(e.g. 50 Hz HV power grid)

∑ ∑ν

1

L,ν

L,1

II

H H,ν Bν ν B

k = k =

Prague, 8-11 June 2009

Schmautzer-Austria Session 2 Paper 0627

kH Considering Several Frequencies IncludingPhase Information

Results of weighting functionsTime course of signal

FFT

( ) ( )ν ν ννν

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

II

H,B H,B,ν Bν 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 1.0003 150 0.0 0.00 33.3 33.3 0.0005 250 7.0 0.70 20.0 20.0 0.0357 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 1.0003 50.0 0 0.00 100.0 33.3 0.0005 83.3 3 0.86 60.0 20.0 0.0437 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 ERApplicable 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,jL,j 0 L,j L,j

H μ H BER = = =

H μ H Bi

E,iL,i

EER =

E

∑ ∑ ∑10MHz 10MHz 10MHz

j jB B,j

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

H BER = ER = =

H B ∑ ∑10MHz 10MHz

iE E,i

i=1Hz i=1Hz L,i

EER = 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 Bn

TER = ER

∑E En

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, Source(Pi)

Further Sources?

TERB(Pi)=∑ERB, Sources,(Pi)

No

Yes

Define imission point Pi

Harmonic factorkH

Relevant current Irv

Exposition ratio for a specificexposition situation at the imission point

Examplary situation with three sources

and a base loadFlow Chart for Evaluating TERB

Prague, 8-11 June 2009

Schmautzer-Austria Session 2 Paper 0627

Magnetic Field ERB- Field Sources 1 & 2Field Source 1 :Railway

B,1ER = 0.021 1.827 2.05 = 0.079⋅ ⋅

B,2ER = 0.08 0.783 1.2 = 0.075⋅ ⋅

Field Source 2: Overhead Line

rvc

N

I 1827k = = =1.827I 1000

B,1 B,1,16.7 Hz 1 C H rvER =ER (P ) k k (I )⋅ ⋅

rvc

N

I 1800k = = = 0,783I 2300

B,2 B,2,50 Hz 1 C H rvER =ER (P ) k k (I )⋅ ⋅

Prague, 8-11 June 2009

Schmautzer-Austria Session 2 Paper 0627

Magnetic Field ERB- Field Source 3

1. Approach: Calculation with values fromgrafic / table

rvC

N

I 800k 0.8I 1000

= = =

Field Source 3: Cable

0,1 0,2 0,5 1 2 5 10 20 50 1000 6,667 3,333 1,333 0,667 0,333 0,133 0,067 0,033 0,013 0,007

Abstand d in m

Abstand a in m

2. Approach: Analytical calculation

( )B,3 B,3,16.7 Hz 1 C H rvER = ER (P ) k k I = 0.033 0.8 2.6 = 0.069⋅ ⋅ ⋅ ⋅

rv

j 3B,3,16.7 Hz 1

L,j L,j

0.2 I (A) 0.2 800(A)B x (m) 20(m)ER (P ) = = 0.0267B B (µT) 300(µT)

⋅ ⋅

= =

( )B,3 B,3,16.7 Hz 1 H rvER = ER (P ) k I = 0.0267 2.6 = 0.069⋅ ⋅

Prague, 8-11 June 2009

Schmautzer-Austria Session 2 Paper 0627

Magnetic Field ERB- Field Source 4 & TERB

Field Source 4: Base Load

Total Expositon Ratio TER of the magnetic field

42.3 % of the allowed range of the magnetic field (100 %) in P1is utilised

B,4ER = 0.20 (20 %)

N

B B,nn 1

TER ER=

= ∑

BTER 0.079 0.075 0.069 0.20 0.423 1= + + + = ≤

Prague, 8-11 June 2009

Schmautzer-Austria Session 2 Paper 0627

Conclusion• Simple method to evaluate electric and magnetic fields

• Considering several sources and different frequencies

• Use of precalculated exposition ratios ER (power lines, railways, appliances)

• Aggregation of several sources using ERs → summed up to TER

• TER <1: exposure to electric & magnetic fields is acceptable

• TER >1: detailed verification of situation

• Cardiac Pacemaker: can be treated in the same way using adequate limits

considering the influence of the magnetic and the electric field


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