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Transcript of 9.1_DPFCCS_PFC
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8/17/2019 9.1_DPFCCS_PFC
1/2
PFC EngineeringStation Road
Great ChesterfordEssex CB10 1NY
t: 01799 530728
f: 01799 530235
w: pfc-engineering.com
The Energy
Solution
Specialists.
Detuned Power Factor Correction
Case Study – Plastics Factory
We were asked to attend site to carry
out a power factor correction survey on a
plastics factory who, due to their impending
increase in load, had a requirement for
more power factor correction. As a normal
part of our power factor correction survey
our survey engineer measured the voltage
harmonics to determine whether any powerfactor correction recommend would have
to incorporate detuning reactors to avoid
harmonic overloading of the capacitors.
During this survey the voltage harmonics
were recorded as being in excess of 8%.
Such a level of harmonic voltage distortion
is beyond even the IEC compatibility limits,
meaning that any equipment connected
to such a distorted supply cannot be
guaranteed to function correctly.
BY INSTALLING OUR DETUNED
POWER FACTOR CORRECTION
SYSTEM WE MANAGED TO NOT
ONLY PREVENT A DAMAGING
HARMONIC RESONANCE, BUT
ACTUALLY REDUCE THE LOAD
HARMONICS, POTENTIALLY
INCREASING THE LIFE OF THE
CLIENTS PLANT.
The installation at the time of the survey
included a 400 kVAr power factor correction
bank arranged in four steps of 100kVAr, all
of which was in circuit at the time of the test.
The immediate suspicion was that the power
factor correction capacitors were forming a
resonant or at least partial resonant circuit
with the supply transformer leading to a
magnification of the loads natural harmonic
levels. In order to test this theory the
capacitor banks were all switched out of
circuit and the harmonic voltage measured
once again. Upon doing this the voltage
distortion was found to be in the region of
3.5% to 4.0%, clearly supporting the theory
that the capacitors were exacerbating a
previously moderate harmonic issue. Upon
closer analysis of the specific harmonics
contributing to the overall harmonic
distortion it was discovered that the 5th
harmonic was the dominant harmonic.
In order to determine the true extent of the
problem a period of harmonic logging was
commissioned with the original power factor
correction operating. Figure 1 shows the
profile of the voltage total harmonic voltage
distortion captured with the original power
factor correction running. The first couple of
days of the analysis were during the weekend
and consequently no plant was operating.
Once the plant started operating on the
Sunday night there was an immediate jump
in the voltage THD, with the distortion levelpeaking at more than 8%. Figure 2 shows
the profile of the 5th harmonic voltage taken
during the same period. It can be seen that
this profile is almost identical to the THD
profile, indicating that the 5th harmonic is by
far the dominant harmonic.
From the predicted increase in loading it
was calculated that the total future power
factor correction requirement was 600
kVAr. Clearly this amount of power factorcould not be connected without detuning
reactors as it would result in harmonics
levels even higher than the elevated values
existing at the time. In cases such as this
the most common solution would be to
install capacitors with 189 Hz detuning
reactors, which prevent the magnification
of harmonics for all of the harmonics from
the 5th order upwards. Normally the total
harmonic distortion of a supply consists of
contributions from a number of harmonics
whose magnitude decreases as the
harmonic order increases. As has already
been mentioned, the harmonic distortion at
this site is overwhelmingly dominated by the
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8/17/2019 9.1_DPFCCS_PFC
2/2
PFC EngineeringStation Road
Great ChesterfordEssex CB10 1NY
t: 01799 530728
f: 01799 530235
w: pfc-engineering.com
The Energy
Solution
Specialists.
5th harmonic and as such any reduction in
this harmonic would have a profound impact
on the total harmonic distortion. With this in
mind it was recommended that a 210 Hz
detuned power factor correction system
was installed at this site. The effect of tuning
the power factor correction to 210 Hz is that
as well as preventing magnification of all of
the major harmonics it actually provides
filtration of the 5th harmonic.
The larger the capacitor bank, the greaterthe filtration effect is and bearing in mind the
recommended capacitor bank size for this
site was 600 kVAr the potential filtration was
significant.
Based upon the commercial and technical
arguments presented for this project, the
installation of a 600 kVAr, 210 Hz detuned
power factor correction system was
commissioned. Figure 3 and Figure 4
show, respectively, a profile of the voltage
total harmonic distortion and 5th harmonic
distortion with all of the replacement
detuned power factor correction in circuit.
It can be seen that as opposed to the
original level of 8%, the voltage THD with
the detuned capacitors in circuit was barely
2%. In addition to this the 5th harmonic
voltage no longer dominates the voltage
THD to the same degree as before, this time
only constituting approximately 1.6% of the
2.2% distortion.
Conclusion
From the preceding results it is apparent
that the old power factor correction was
producing a serious harmonic resonantcondition. The additional harmonics
imposed upon the supply transformer would
have produced significant additional stress
upon the supply transformer, potentially
reducing the lifespan of the transformer and
compromising the integrity of the supply.
By installing 210 Hz detuned power factor
correction, a solution to the poor load
power factor has been implemented that
provides both an economical and technical
advantage, resulting in a supply that
operates efficiently with little potential for
mal-operation of connected equipment due
to excessive voltage harmonic distortion.
Figure 1: Profile of voltage total harmonic distortion captured during
initial harmonic analysis period.
0
1
2
3
4
5
6
7
8
9
10
1 1 : 3 4 : 0 0
1 3 : 1 0 : 0 0
1 4 : 4 6 : 0 0
1 6 : 2 2 : 0 0
1 7 : 5 8 : 0 0
1 9 : 3 4 : 0 0
2 1 : 1 0 : 0 0
2 2 : 4 6 : 0 0
0 0 : 2 2 : 0 0
0 1 : 5 8 : 0 0
0 3 : 3 4 : 0 0
0 5 : 1 0 : 0 0
0 6 : 4 6 : 0 0
0 8 : 2 2 : 0 0
0 9 : 5 8 : 0 0
1 1 : 3 4 : 0 0
1 3 : 1 0 : 0 0
1 4 : 4 6 : 0 0
1 6 : 2 2 : 0 0
1 7 : 5 8 : 0 0
1 9 : 3 4 : 0 0
2 1 : 1 0 : 0 0
2 2 : 4 6 : 0 0
0 0 : 2 2 : 0 0
0 1 : 5 8 : 0 0
0 3 : 3 4 : 0 0
0 5 : 1 0 : 0 0
0 6 : 4 6 : 0 0
0 8 : 2 2 : 0 0
0 9 : 5 8 : 0 0
1 1 : 3 4 : 0 0
1 3 : 1 0 : 0 0
1 4 : 4 6 : 0 0
1 6 : 2 2 : 0 0
1 7 : 5 8 : 0 0
1 9 : 3 4 : 0 0
2 1 : 1 0 : 0 0
2 2 : 4 6 : 0 0
0 0 : 2 2 : 0 0
0 1 : 5 8 : 0 0
0 3 : 3 4 : 0 0
0 5 : 1 0 : 0 0
0 6 : 4 6 : 0 0
V o l t a g e d i s t o r t i o n ( %
)
Voltage total harmonic distortion with original PFC
Vthd L1 Vthd L2 Vthd L3
Figure 2: Profile of voltage 5th harmonic distortion captured during initial
harmonic analysis period.
0
1
2
3
4
5
6
7
8
9
1 1 : 3 4 : 0 0
1 3 : 1 0 : 0 0
1 4 : 4 6 : 0 0
1 6 : 2 2 : 0 0
1 7 : 5 8 : 0 0
1 9 : 3 4 : 0 0
2 1 : 1 0 : 0 0
2 2 : 4 6 : 0 0
0 0 : 2 2 : 0 0
0 1 : 5 8 : 0 0
0 3 : 3 4 : 0 0
0 5 : 1 0 : 0 0
0 6 : 4 6 : 0 0
0 8 : 2 2 : 0 0
0 9 : 5 8 : 0 0
1 1 : 3 4 : 0 0
1 3 : 1 0 : 0 0
1 4 : 4 6 : 0 0
1 6 : 2 2 : 0 0
1 7 : 5 8 : 0 0
1 9 : 3 4 : 0 0
2 1 : 1 0 : 0 0
2 2 : 4 6 : 0 0
0 0 : 2 2 : 0 0
0 1 : 5 8 : 0 0
0 3 : 3 4 : 0 0
0 5 : 1 0 : 0 0
0 6 : 4 6 : 0 0
0 8 : 2 2 : 0 0
0 9 : 5 8 : 0 0
1 1 : 3 4 : 0 0
1 3 : 1 0 : 0 0
1 4 : 4 6 : 0 0
1 6 : 2 2 : 0 0
1 7 : 5 8 : 0 0
1 9 : 3 4 : 0 0
2 1 : 1 0 : 0 0
2 2 : 4 6 : 0 0
0 0 : 2 2 : 0 0
0 1 : 5 8 : 0 0
0 3 : 3 4 : 0 0
0 5 : 1 0 : 0 0
0 6 : 4 6 : 0 0
V o l t a g e d i s t o r t i o
n ( % )
Voltage 5th harmonic distortion with original PFC
Vthd L1 Vthd L2 Vthd L3
Figure 3: Profile of voltage total harmonic distortion captured after the
installation of the detuned power factor correction.
0
0.5
1
1.5
2
2.5
1 2 : 5 3 : 0 0
1 4 : 3 4 : 0 0
1 6 : 1 5 : 0 0
1 7 : 5 6 : 0 0
1 9 : 3 7 : 0 0
2 1 : 1 8 : 0 0
2 2 : 5 9 : 0 0
0 0 : 4 0 : 0 0
0 2 : 2 1 : 0 0
0 4 : 0 2 : 0 0
0 5 : 4 3 : 0 0
0 7 : 2 4 : 0 0
0 9 : 0 5 : 0 0
1 0 : 4 6 : 0 0
1 2 : 2 7 : 0 0
1 4 : 0 8 : 0 0
1 5 : 4 9 : 0 0
1 7 : 3 0 : 0 0
1 9 : 1 1 : 0 0
2 0 : 5 2 : 0 0
2 2 : 3 3 : 0 0
0 0 : 1 4 : 0 0
0 1 : 5 5 : 0 0
0 3 : 3 6 : 0 0
0 5 : 1 7 : 0 0
0 6 : 5 8 : 0 0
0 8 : 3 9 : 0 0
1 0 : 2 0 : 0 0
1 2 : 0 1 : 0 0
1 3 : 4 2 : 0 0
1 5 : 2 3 : 0 0
1 7 : 0 4 : 0 0
1 8 : 4 5 : 0 0
2 0 : 2 6 : 0 0
2 2 : 0 7 : 0 0
2 3 : 4 8 : 0 0
0 1 : 2 9 : 0 0
0 3 : 1 0 : 0 0
0 4 : 5 1 : 0 0
0 6 : 3 2 : 0 0
0 8 : 1 3 : 0 0
0 9 : 5 4 : 0 0
1 1 : 3 5 : 0 0
V o l t a g e d i s t o r t i o n ( % )
Voltage total harmonic distortion with detuned PFC
Vthd L1 Vthd L2 Vthd L3
Figure 4: Profile of voltage 5th harmonic distortion captured after the
installation of the detuned power factor correction
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
1 2 : 5 6 : 0 0
1 4 : 3 7 : 0 0
1 6 : 1 8 : 0 0
1 7 : 5 9 : 0 0
1 9 : 4 0 : 0 0
2 1 : 2 1 : 0 0
2 3 : 0 2 : 0 0
0 0 : 4 3 : 0 0
0 2 : 2 4 : 0 0
0 4 : 0 5 : 0 0
0 5 : 4 6 : 0 0
0 7 : 2 7 : 0 0
0 9 : 0 8 : 0 0
1 0 : 4 9 : 0 0
1 2 : 3 0 : 0 0
1 4 : 1 1 : 0 0
1 5 : 5 2 : 0 0
1 7 : 3 3 : 0 0
1 9 : 1 4 : 0 0
2 0 : 5 5 : 0 0
2 2 : 3 6 : 0 0
0 0 : 1 7 : 0 0
0 1 : 5 8 : 0 0
0 3 : 3 9 : 0 0
0 5 : 2 0 : 0 0
0 7 : 0 1 : 0 0
0 8 : 4 2 : 0 0
1 0 : 2 3 : 0 0
1 2 : 0 4 : 0 0
1 3 : 4 5 : 0 0
1 5 : 2 6 : 0 0
1 7 : 0 7 : 0 0
1 8 : 4 8 : 0 0
2 0 : 2 9 : 0 0
2 2 : 1 0 : 0 0
2 3 : 5 1 : 0 0
0 1 : 3 2 : 0 0
0 3 : 1 3 : 0 0
0 4 : 5 4 : 0 0
0 6 : 3 5 : 0 0
0 8 : 1 6 : 0 0
0 9 : 5 7 : 0 0
1 1 : 3 8 : 0 0
V o l t a g e d i s t o r t i o n ( %
)
Voltage 5th harmonic distortion with detuned PFC
Vthd L1 Vthd L2 Vthd L3
