Presentation Harmonics Filters LM 20081013

3b. Harmonicsand the effect on power quality

Power Quality Solutions by EPCOS

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.


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 (


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 %.


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.


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


Problems caused by harmonics

Real case examples:


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


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

3c. Filtering techniques



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%


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, ...)


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!

Filtering techniques

1. Detuned Harmonic Filters



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


Filter frequency < lowest harmonic

f (Hz)

IZI (ohm)

fr fsf1

Impedance withPFC Detuned Filter

Harmonic currents spectrum

Impedance with capacitors

Impedancewithout capacitors


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


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


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.


Easy filter selection with our selection tables

7% 50kvar Capacitor Contactor

Reactor


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


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


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


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


Power Quality Solutions

Peak performance through great partnerships

Thank you for your attention!

Presentation Harmonics Filters LM 20081013

Documents

Transcript of Presentation Harmonics Filters LM 20081013