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
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
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