Download - Presentation Harmonics Filters LM 20081013
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3b. Harmonicsand the effect on power quality
Power Quality Solutions by EPCOS
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 2
Example for harmonic representations
0 pipipipipipipipi 2
VI1
I5I7
1 3 5 7 9 11 13 15 17 19 21 23
Ih/I1100%
50%
25
Definition: Harmonics are integral multiples of some fundamental frequency that, when added
together, result in adistorted waveform.
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 3
Power quality according EN50160Supply voltage phenomenon
Acceptable limits Monitoring Period
Acceptance Percentage
Slow voltage changes +10% / -10% Unom 1 Week 95%
Voltages Sags or Dips (
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 4
Power quality according EN50160
1,5 %25.
1,5 %23.
1,5 %19.
2,0 %17.
0,5 %21.3,0 %13.
0,5 %6.-24.0,5 %15.3,5 %11.1,0 %4.1,5 %9.5,0 %7.
2,0 %2.5,0 %3.6,0 %5.
Relativevoltage
Orderh
Relativevoltage
Orderh
Relativevoltage
Orderh
Multiples of 3Not multiples of 3EVEN HARMONICSODD HARMONICS
Standard EN50160 prescribes: Under normal operating conditions, during each period of one week, 95% of the 10 minute mean rms value of each individual harmonic voltage shall be less than or equal to the value given in Table 1. The TDH of the supply voltage (including all harmonics up to the order 40) shall be less than or equal to 8 %.
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 5
Harmonics sequence - differentiation
Definition: Harmonic sequence is the phase rotation relationship with respect to the fundamental component. Positive sequence harmonics ( 4th, 7th, 10th , .) have the same phase rotation as the fundamental component. These harmonics circulate between the phases. Negative sequence harmonics ( 2nd, 5th, 8th ) have the opposite phase rotation with respect to the fundamental component. These harmonics circulate between the phases. Zero sequence harmonics ( 3rd, 6th, 9th, ) do not produce a rotating field. These harmonics circulate between the phase and neutral or ground. These third order or zero sequence harmonics, unlike positive and negative sequence harmonic currents, do not cancel but add up arithmetically in the neutral.
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 6
Problems caused by harmonics
Overheating of transformers (K-Factor), and rotating equipment Neutral overloading / unacceptable neutral-to-ground voltages Failed capacitor banks Breakers and fuse tripping Unreliable operation of electronic equipment, and generators Wasted energy / higher electric bills and Wasted capacity - Inefficient distribution of power
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 7
Problems caused by harmonics
Real case examples:
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 8
Cost caused by harmonics
Additional investment due to faster equipment derating
Higher energy consumption
Higher downtime of production equipment
Higher maintenance and repair cost
Reduced product quality
Reduced production output
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 9
Solutions for reducing the harmonic content
Increase fault level (reduction of impedances) Limiting total output / simultaneously working harmonic sources Balanced connection of 1-phase loads to the 3-phases Using equipment with higher pulse number Use harmonic filtering techniques
De-tuned harmonic filters Tuned harmonic filter Active harmonic filter
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3c. Filtering techniques
Power Quality Solutions by EPCOS
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 11
How to select the right filter (EPCOS rules)1. Are there harmonics THD-Iwoc >10% or THD-Vwoc > 3% ?
yes: Harmonic filters no: standard PFC without reactors
2. Is there 3rd harmonic, THD-I3 > 0.2 THD-I5 ? yes: use p=14% no: use p= 7% or 5.67%
3. Is THD-Iwoc < 20% ? yes: use p= 7% no: use p= 5.67%
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 12
When to select Active filter
If uncompensated PF is close to 1 and high harmonic distortion has to be reduced
Extraordinary high content of non linear load and very tough requirements for power quality, e.g. THD-V < 3 %
Dynamic change of harmonic distortion
In case of sensitive equipment (e.g. semiconductor fab, hospital, ...)
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 13
PFC Filter standard or detuning?
PFC without detuned filter PFC with 5,67% detuned filter
PFC with 7% detuned filter PFC with 14% detuned filter
Blue=System without PFC Green=System with PFC
25% 5%
5% 5%
Capacitors without reactors are amplifying the harmonics!
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Filtering techniques
1. Detuned Harmonic Filters
Power Quality Solutions by EPCOS
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 15
Targets of detuned harmonic filters
Correct the Power Factor
Improvement of power quality and system lifetime
Protect capacitors,distribution equipment and loads in general
Filtering harmonics
Avoid resonance risk
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 16
Filter frequency < lowest harmonic
f (Hz)
IZI (ohm)
fr fsf1
Impedance withPFC Detuned Filter
Harmonic currents spectrum
Impedance with capacitors
Impedancewithout capacitors
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 17
Detuned harmonic filter
ImpedanceImpedance
o
00,020,040,060,08
0,10,120,14
50 150 250 350 450 550
189Hz5th 7th 11th
CLfXX
pC
L==
224100100 pi
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 18
5% 224 Hz
5.5% 213 Hz
5.67% 210 Hz
14% 134 Hz
6% 204 Hz
7% 189 Hz
8% 177 Hz
12.5% 141Hz
Typical frequencies (50Hz grid)
CLfXX
pC
L==
224100100 pi
p =fnfres
1002
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 19
Formulas for calculation of detuned filters
pUU NC
=
100100
CN
CC NU
UpQ
= 2
2
1001
fU
p
NCN
C
=
pi2100
1
2
CfpL
= 224100 pi
1002
Re
=
sff
p
CLfXX
pC
L==
224100100 pi
Reactors connected in series with capacitors result into an increased voltage across the capacitor. Capacitors used for de-tuned filters are therefore required to have voltage ratings higher than the line voltage.
e.g. UN = 400V, P=7%, calculate UC = 430VA 440V capacitor can be used.
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 20
Easy filter selection with our selection tables
7% 50kvar Capacitor Contactor
Reactor
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 21
Detuned Filters
Advantages: Low cost, easy design Easy control to compensate the
desired reactive power Very less risk
Disadvantages: Cannot filter the harmonic current
efficiently (max. is 50%)
Fuses
Contactors
Reactors
Capacitors
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 22
Customer benefits of detuned filters (1) Improvement of Power Factor
Reduction of harmonics
Reduction of ohmic losses, real kW energy savings
Elimination of power utilities penalties on low power factor
Power Quality improvement
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 23
Customer benefits of detuned filters (2) Climatic protection, reduction of greenhouse gas emissions
Reduction of new investment for distribution equipment (transformers, LV switchgear )
Reduction of equipment maintenance cost and down time of production equipment
Improvement of production process stability and reliability
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 24
Summary detuned filters
Resonance frequency not close to any harmonic
Filter frequency ffilter < fharmonic
A certain reduction of harmonic distortion
Capacitors are blocked against resonance, therefore de-tuned
filters are also known as anti-resonance- filter
More reliable than standard PFC banks
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Power Quality Solutions FK PC PM PFC Lukas Motta May 2008 - page 25
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