IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
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Electrical Power Quality of Iron
and Steel Industry in Turkey
Özgül Salor, Member, IEEE, Burhan Gültekin, Student Member, IEEE, Serkan Buhan, Burak Boyrazoğlu,
Tolga İnan, Tevhid Atalık, Adnan Açık, Alper Terciyanlı, Student Member, IEEE,
Özgür Ünsar, Student Member, IEEE, Erinç Altıntaş, Yener Akkaya, Ercüment Özdemirci,
Işık Çadırcı, Member, IEEE, and Muammer Ermiş, Member, IEEE
Abstract—The iron and steel industry has been growing increasingly in Turkey in the last decade. Today, its electricity demand is
nearly one tenth of the installed generation capability of 40 GW in
the country. In this paper, power quality (PQ) investigations based
on the arc furnace installations of the iron and steel plants using
field measurements according to the international standard IEC
61000-4-30 are documented. Interharmonics and voltage flicker
problems occurring both at the common-coupling points of those
plants and at the arc furnace and static var compensator (SVC)
systems of the plants themselves are determined with the use
of GPS receiver synchronization modules attached to the mobile
PQ measurement systems. It has been observed that flicker and
interharmonic problems are dominant at the points of common
Paper PID-2009-04, presented at the 2007 Industry Applications Society
Annual Meeting, New Orleans, LA, September 23–27, and approved for
publication in the IEEE T RANSACTIONS ON I NDUSTRY A PPLICATIONS by
the Metals Industry Committee of the IEEE Industry Applications Society.
Manuscript submitted for review November 30, 2007 and released for publication June 22, 2009. This work was supported by the Public Research Grant
Committee (KAMAG) of The Scientific and Technological Research Council
of Turkey (TÜBİTAK).
Ö. Salor and A. Açık are with the Power Electronics Department,
TÜBİTAK UZAY Research Institute, The Scientific and Technological Research Council of Turkey (TÜBİTAK), 06531 Ankara, Turkey (e-mail: ozgul.
salor@uzay.tubitak.gov.tr; adnan.acik@uzay.tubitak.gov.tr).
B. Gültekin, T. İnan, and A. Terciyanlı are with the Middle East Technical University, 06531 Ankara, Turkey, and also with the Power Electronics
Department, TÜBİTAK UZAY Research Institute, The Scientific and Technological Research Council of Turkey (TÜBİTAK), 06531 Ankara, Turkey
(e-mail: burhan.gultekin@uzay.tubitak.gov.tr; tolga.inan@uzay.tubitak.gov.tr;
alper.terciyanli@uzay.tubitak.gov.tr).
S. Buhan and I. Çadırcı are with Hacettepe University, 06532 Ankara,
Turkey, and also with the Power Electronics Department, TÜBİTAK UZAY Research Institute, The Scientific and Technological Research Council of Turkey
(TÜBİTAK), 06531 Ankara, Turkey (e-mail: serkan.buhan@uzay.tubitak.gov.
tr; isik.cadirci@uzay.tubitak.gov.tr).
B. Boyrazoğlu is with Renaissance Constructions, Moscow, Russia (e-mail:
burak.boyrazoglu@uzay.tubitak.gov.tr).
T. Atalık is with Başkent University, 06530 Ankara, Turkey, and also with
the Power Electronics Department, TÜBİTAK UZAY Research Institute, The
Scientific and Technological Research Council of Turkey (TÜBİTAK), 06531
Ankara, Turkey (e-mail: tevhid.atalik@uzay.tubitak.gov.tr).
Ö. Ünsar is with Hacettepe University, 06532 Ankara, Turkey, and also
with the Turkish Electricity Transmission Corporation (TEIAŞ), 06100 Ankara,
Turkey (e-mail: ozgur.unsar@yahoo.com.tr).
E. Altıntaş is with the Middle East Technical University, 06531 Ankara,
Turkey, and also with the Turkish Electricity Transmission Corporation
(TEIAŞ), 06100 Ankara, Turkey (e-mail: erincaltintas@gmail.com).
Y. Akkaya and E. Özdemirci are with the Turkish Electricity Transmission
Corporation (TEIAŞ), 06100 Ankara, Turkey (e-mail: yener.akkaya@teias.
gov.tr; ercument.ozdemici@teias.gov.tr).
M. Ermiş is with the Middle East Technical University, 06531 Ankara,
Turkey (e-mail: ermis@metu.edu.tr).
Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TIA.2009.2036547
couplings where arc furnace installations are supplied. Based on
the field measurements obtained with collaborative work of five
arc furnace plants, it is possible to say that contemporary SVC
systems cause interharmonic amplification problems around the
second harmonic, and novel methods are required to solve this
problem.
Index Terms—Arc furnace, flicker, group harmonic,
interharmonic–flicker relation, interharmonics, iron and steel
industry, ladle furnace, power quality (PQ), single-line harmonic,
subgroup harmonic.
I. I NTRODUCTION
HE iron and steel industry has been growing increasingly
in Turkey in the last decade. Today, its electricity demand
is nearly one-tenth of the installed generation capability of
40 GW in the country. Steel production in Turkey is based on
extensive use of arc and ladle furnaces in most of the plants,
which is the cause of power quality (PQ) problems at those
locations of the Turkish Electricity Transmission System.
PQ of electric arc furnaces (EAF) has been investigated
previously by some other researchers [1]–[5]. Arc furnace
characterization of one plant has been achieved in [1] in terms
of PQ parameters given in the IEC standard 61000-4-30 [6]. In
[2], different phases of EAF operation connected to the 13.5-kV
voltage level have been considered for obtaining a single-phase
equivalent circuit of the EAF.
In [3], the compatibility between the PQ disturbance levels
and the Argentinean regulations for EAF operation has been
considered. Measuring system accuracy for PQ of EAF installations has been investigated in [4]. In [5], flicker propagation
in the network based on interharmonic analysis on arc furnaces
is introduced.
In this paper, we present very detailed and extensive investigations and results obtained from the PQ of arc furnace installations in Turkey. The main focus is the investigation of the PQ
problems caused by the iron and steel industry plants connected
directly to the Turkish Electricity Transmission System. The
critical points of the transmission system are being monitored
by the mobile PQ monitoring systems developed through the
National Power Quality Monitoring Project [7]. By taking oneweek snapshots of all PQ parameters specified in IEC 610004-30 [6], PQ of the iron and steel plants has been assessed.
Based on this assessment, detailed investigation on the selected
five plants supplied from the same busbar has been carried
out. Raw data of voltage and current waveforms have been
T
0093-9994/$26.00 © 2010 IEEE
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 1. Location of iron and steel plants on the Turkish Electricity Transmission System.
collected for approximately 2 h at each plant based on a measurement schedule. This schedule requires collaborative work
of all plants, since the arc furnace operation at the plants other
than the measured one was stopped for 15 min. Contribution
of the flicker and harmonics of each plant could be observed
using these measurements, while it is also possible to evaluate
the effectiveness or inefficiencies of the static-var-compensator
(SVC)-type flicker compensation systems. It has been shown
that, with the common practices of compensation systems, it is
not possible to solve the flicker problem at the point of common
coupling (PCC) from where arc furnaces are supplied.
Section II presents the general overview of the PQ of the
iron and steel plants in Turkey. In Section III, description of the
selected plants is given for detailed investigation. Measurement
scenarios at those plants are presented in Section IV. In
Section V, observations on the harmonic content of the EAFs on
the electric network are given. Sections VI and VII summarize
the harmonic computation methods used based on IEC 610004-30, and flicker–interharmonic relationship observations are
presented, respectively, from theoretical and experimental perspectives. Assessment of the performance of SVC-type flicker
compensation systems installed at EAF plants in terms of
reactive power compensation, harmonic filtering performance,
and flicker compensation performance is explained in detail in
Section VIII. Section IX presents the PQ interaction of EAFs in
multifurnace operations.
II. C OUNTRYWIDE PQ S NAPSHOT OF I RON
AND S TEEL P LANTS
Major iron and steel plants are marked on the map of the
Turkish Electricity Transmission System in Fig. 1. Steel production in only four of these plants is based on blast furnaces.
At three points or regions of the Turkish Electricity System,
multifurnace operation takes place. PQ of all of those plants
has been investigated based on the field measurements carried
out according to IEC 61000-4-30 for Class B performance by
using the mobile monitoring systems [7]. By the end of year
2008, the National Power Quality Monitoring Center started
to operate for remote monitoring of the Turkish Electricity
Transmission System and its customers by permanent monitors
designed through the National Power Quality Project [8]. This
system will monitor the feeders of heavy industry, including
iron and steel plants, continuously.
The PQ measurements have been carried out at 400 kV, and
154-kV PCCs for iron and steel plants. From the results of
Fig. 2. Long- and short-term flicker cumulative probability function for some
plants connected to different PCCs at 400 kV.
the continuous PQ measurements lasting seven days at major
transformer substations supplying power to arc furnace plants,
the following problems have been identified.
1) Although almost all of the plants are equipped with
modern SVC systems, measured flicker and current total
demand distortion (current TDD) values exceed the limits
specified in the Turkish Electricity Transmission System
Supply Reliability and Quality Regulation [9], which
complies with the IEEE Std. 519-1992 [10]. The problem
is more serious at transformer substations or busbars
supplying multiple arc furnaces as shown in Figs. 2–14.
Cumulative probability function CPF(x) in the figures
indicates the percentage of the total measurement time for
which the measured parameter is below a value x, given
in the horizontal axis. All harmonic analyses have been
carried out using the single-line harmonic components
directly in this part of the work. Single-line harmonic
frequency concept is presented in IEC 61000-4-7 [11].
Different harmonic analysis techniques given in [11]
are summarized in Section VI. Since the power system
frequency in Turkey is 50 Hz, ten-cycle Discrete Fourier
Transform (DFT) computation is used as suggested in
IEC 61000-4-30 [6].
2) In all arc furnace installations, the second harmonic current component at the PCC exceeds the limit values even
after filtration. Current waveforms of arc furnaces are rich
in interharmonics at low frequencies, particularly in melting state. For instance, the dominant flicker modulation
frequency of 8.8 Hz causes interharmonics in line current
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
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Fig. 6. Fourth harmonic cumulative probability function for some plants
connected to different PCCs at 154 kV.
Fig. 3. Long- and short-term flicker cumulative probability function for some
plants connected to different PCCs at 154 kV.
Fig. 7. Fifth harmonic cumulative probability function for some plants connected to different PCCs at 154 kV.
Fig. 4. Second harmonic cumulative probability function for some plants
connected to different PCCs at 154 kV.
Fig. 8. Primary current TDD cumulative probability function for some plants
connected to different PCCs at 154 kV.
Fig. 5. Third harmonic cumulative probability function for some plants
connected to different PCCs at 154 kV.
waveforms at frequencies of f = 50k ± 8.8 Hz, where
k = 1, 2, 3, . . .. This fact has also been pointed out by
some other researchers [14], [15]. Some of these lowfrequency interharmonic components in the line currents
are obviously amplified when attempted to be filtered out
by C-type second harmonic and second-order third harmonic filters. On this occasion, the causes of undesirably
high values of voltage flicker, and current harmonics and
interharmonics at PCC have been investigated not only
for multi-furnace installations but also for single EAF
operation. The findings and the related discussion will
be reported in the following sections. Mitigation methods
will be discussed within the scope of another paper.
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 9. Primary current TDD cumulative probability function for a plant
connected to a 154-kV PCC.
Fig. 10. Second harmonic cumulative probability function for a plant connected to a 400-kV PCC.
Fig. 11. Third harmonic cumulative probability function for a plant connected
to a 400-kV PCC.
III. D ESCRIPTION OF S ELECTED P LANTS
FOR D ETAILED I NVESTIGATION
As a result of these observations, five plants with arc furnace
installations which are supplied from the same busbar of the
transmission system are selected for further investigations on
the PQ parameters. These five plants are those on the western
side of Turkey (İzmir/Aliağa region), as shown on the map in
Fig. 1. Single-line diagram of the five plants is shown in Fig. 15.
IV. M EASUREMENT S CENARIOS
AT THE S ELECTED P LANTS
The measurements at the five selected plants were organized
with a collaborative effort of all plants. At each plant, raw
Fig. 12. Fourth cumulative probability function for a plant connected to a
400-kV PCC.
Fig. 13. Fifth harmonic cumulative probability function for a plant connected
to a 400-kV PCC.
Fig. 14. Primary current TDD cumulative probability function for a plant
connected to a 400-kV PCC.
data of currents and voltages are recorded for approximately
2 h. During this 2-h period, other four plants were organized
such that they stop furnace operation and their SVC systems
for 15 min at the same time. Three-phase current and voltage
measurements are collected at both the supply side and the
plant side. Arc furnaces, ladle furnaces, where applicable, and
SVC unit currents and voltages are recorded separately. All
measurements are synchronized by a GPS receiver module.
This measurement process is repeated at each one of the five
selected plants. Measurement points are as shown in Fig. 16.
The 15-min off period of the other plants connected to the
same bus guarantees that, during this period, if any current
harmonics or interharmonics are observed at the SVC unit
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Fig. 15. Single-line diagram of the selected five plants.
5
Power (UHP) EAF, together with its flicker compensation system, are shown in Fig. 17 over one tap-to-tap period. Furnace
charging, boring, melting, and refining periods are apparent
from these records. Seven-day flicker and current TDD variations of the same EAF + SVC installation (36 kV) are shown
in Fig. 18.
IEC 61000-4-30 gives the ten-cycle (for 50-Hz systems)
gapless harmonic and interharmonic subgroup measurement,
denoted in IEC 61000-4-7 as the basic measurements for classA performance.
In IEC-61000-4-7, however, three different methods of harmonic and interharmonic computation practices are given. In
the case of fluctuating harmonics and interharmonics, these
three methods give close but different results, which may
affect the performance of spectrum estimations significantly
for different cases of harmonic and interharmonic contents of
the signal. These three computation methods are summarized
briefly in the following.
1) Harmonic and interharmonic groups:
Harmonic group denoted by Gg,n is the square root
of the sum of the squares of a harmonic and the spectral components adjacent to it within the time window,
such that
Fig. 16. Synchronous measurement points at a typical EAF plant.
(Measurement Point 3) or the supply side of the plant (Measurement Point 1), those harmonics and interharmonics are mainly
the result of the EAF operation only at the measured plant.
This type of measurement can be used to understand whether
the plant is a harmonic source or a harmonic sink on the
electricity transmission network, when the frequency spectra
of the currents recorded with all plants in operation and with
four of them out of operation are compared. It is also possible
to detect any ineffectiveness of the SVCs at the measured plant
using the same comparison.
In order to observe the effectiveness of the SVC system, SVC
of the current plants is turned off and on during the 15-min
idle period of other plants and also when other plants are in
operation. This brings out four cases of measurements at every
plant: other plants on, SVC on; other plants on, SVC off;
other plants off, SVC on; and other plants off, SVC off. The
measurement periods are summarized in Table I. When there
are more than one arc furnace and ladle furnace at a plant, arc
furnaces and their SVCs other than the measured arc furnace
were turned off during the periods when other plants were off.
This measurement scenario has been a very costly practice,
since the plants had to be turned off four times for a 15-min
period, 1 h in total, while data were collected at every one of
the other four plants. Moreover, turning off the SVC of the
measured plant was required twice: first while the other plants
are operative and second while they are inoperative. Moreover,
turning off the SVCs causes inefficiencies of the EAF operation,
which brings additional expenses.
V. ARC F URNACES AS H ARMONIC S OURCES
ON THE N ETWORK
EAF is the most problematic load on the electric network.
Active and reactive power consumptions of an Ultra High
G2g,n =
4
2
C2
Ck−5
2
+
Ck+i
+ k+5
2
2
i=−4
(1)
for 50-Hz power systems, where Ck is the rms of amplitude of the (k)th spectral component obtained from the
DFT for the (n = k/10)th harmonic component. (Since
the resolution is 5 Hz and the system frequency is 50 Hz,
every 10th DFT sample corresponds to a harmonic, i.e.,
10th is the fundamental, 20th is the second harmonic, and
so on.)
Similarly, interharmonic group is defined as
9
2
=
Cig,n
2
Ck+i
(2)
i=1
for 50-Hz power systems, where Ck+i is the (k + i)th
DFT sample, and they are the DFT samples between the
(n)th and the (n + 1)th harmonics (for example, nine
adjacent DFT samples between 55 and 95 Hz for the
interharmonics between second and third harmonics).
2) Harmonic and interharmonic subgroups:
The harmonic grouping considers only the previous
and the next DFT components around the harmonic component itself
1
G2sg,n =
2
Ck+i
.
(3)
i=−1
In the interharmonic subgroup case, the effects of
fluctuations of harmonic amplitudes and phases are partially reduced by excluding the components immediately
adjacent to the harmonic frequencies
2
=
Cisg,n
8
i=2
2
Ck+i
.
(4)
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
TABLE I
M EASUREMENT S CHEDULE (P HASES OF THE EAF: C—C HARGING , B—B ORING , M—M ELTING , AND R—R EFINING )
Fig. 17. Active and reactive power consumptions of a UHP EAF together with
its flicker compensation system in one tap-to-tap period (1-s averages).
3) Single-line harmonic frequency:
This is the single-line measurement of the current or
voltage frequency amplitude component obtained directly
from the 5-Hz-resolution DFT samples according to IEC
61000-4-7.
The spectra in Figs. 19–21 are calculated from the
current data measured in boring, melting, and refining periods, respectively. Fig. 22 shows a pictorial explanation
of the harmonic and interharmonic group and subgroup
concepts. The spectrum in the figure is taken from the
current spectrum of the boring phase shown in Fig. 19.
The harmonic and interharmonic group and subgroup
values obtained from the current waveform in Fig. 19 are
given in Table II.
As observed from Table II, there is a drastic difference
between single line and subgroup, as well as single line and
group harmonic current components particularly for the second
harmonic. However, IEEE Std 519-1992 and Turkish Std 2004
[9] are not defined in the given current harmonic penalty limits
whether these are calculated as subgroup, group, or singleline components. This is the case for most of the research
papers given in the literature, as well. Therefore, the standards
mentioned earlier need to be revised so as to define the limit
Fig. 18. Seven-day (a) current TDD, (b) short-term flicker (Pst ), and (c) longterm flicker (Plt ) variations of UHP EAF.
values according to IEC 61000-4-7 as harmonic subgroups. On
the other hand, in the design and performance assessment of
SVC-type flicker compensation systems applied to the EAFs, it
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Fig. 19. Ten-cycle waveform of the line current of the EAF during boring
phase and its DFT with 5-Hz resolution.
7
Fig. 22. Illustration of the harmonic and interharmonic group and subgroup
computations.
TABLE II
H ARMONIC AND I NTERHARMONIC C OMPUTATIONS FOR L INE C URRENT
OF EAF IN B ORING P HASE S HOWN IN F IG . 21
Fig. 20. Ten-cycle waveform of the line current of the EAF during melting
phase and its DFT with 5-Hz resolution.
in the definition of harmonic limits brings together serious
difficulties in the design and performance evaluation of passive
shunt second and third harmonic filters of SVC-type flicker
compensation systems as will be discussed in Section VIII.
Measurements obtained at MP2 in Fig. 16 show that harmonic contents of EAFs are very rich. Particularly low order
current harmonics such as second and third are observed to
be significant. Sample results for boring, melting, and refining
periods of a High Power (HP) EAF are shown in Fig. 23.
The richest harmonic content and TDD have been obtained for
boring period. Since electric arc is highly stable during refining,
the best harmonic content and TDD values have been obtained
for the refining period.
Fig. 21. Ten-cycle waveform of the line current of the EAF during refining
phase and its DFT with 5-Hz resolution.
is important to consider whether interharmonics and associated
harmonic components injected to the supply side are calculated
as single line or subgroup.
The rich interharmonic content between fundamental and
second single-line harmonic frequency, and the lack of clarity
VI. H ARMONIC C ONTENT C OMPUTATION
BASED ON IEC 61000-4-7
The mobile systems collecting the voltage and current waveform data are sampling the data at a frequency of 3200 Hz. This
sampling rate corresponds to 64 samples per cycle; however,
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 23. Sample results for boring, melting, and refining periods of an HP EAF (harmonic subgroups, ten-cycle averages with five-cycle overlapping windows).
when the supply frequency deviates from 50 Hz, a single cycle
of the waveform is covered by more or less than 64 samples.
This loss of synchronization causes leakage on the DFT samples due to the picket fence effect [17]. According to IEC
61000-4-30, harmonics and interharmonics should be analyzed
in ten-cycle windows which correspond to a frequency resolu-
tion of 5 Hz. With a constant sampling rate of 3200 Hz, the tenth
DFT sample represents the 50-Hz component. When the system
frequency is 49.5 Hz, for example, a leakage occurs from the
tenth DFT sample toward the ninth DFT sample. This causes
an interharmonic to appear, although it does not exist in the
supply frequency. In this paper, a resampling process through
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
9
Fig. 24. Block diagram of the resampling process to sample ten cycles at
640 equally spaced points.
interpolation is therefore achieved at every ten-cycle to prevent
the leakage.
The algorithm is summarized in Fig. 24. Power cycles are
detected using a low-pass filter with a cutoff frequency at
75 Hz followed by a zero-crossing detection block. By using
the zero-crossing points, data are split into ten-cycle blocks
with rectangular windows. The ten-cycle blocks are resampled
through cubic-spline interpolation such that each ten-cycle data
blocks are sampled with a frequency of 64 samples/cycle.
Each 640-sample block is the input to the DFT block, which
outputs a 640-sample DFT output. In this case, the frequency
resolution of the DFT samples changes from the rate of 5 Hz
to 64 × fs /640 = fs /10, where fs is the supply frequency.
The 10th DFT sample again corresponds to the first harmonic
frequency, which is fs , and 20th DFT sample corresponds to
the second harmonic. No leakage occurs from the harmonic
frequencies to the neighborhood interharmonic frequencies in
this case. This approach is used to obtain the harmonic and
interharmonic analyses of the voltage and current waveforms
presented in Section VIII.
VII. F LICKER –I NTERHARMONIC R ELATIONSHIP
The relationship between flicker and interharmonics has been
investigated previously, and it has been shown that flicker and
interharmonics are the causes of each other [14]–[16]. Light
flicker occurs when the voltage amplitude fluctuates in time.
Therefore, flicker can be modeled as an amplitude-modulated
(AM) signal whose carrier frequency is the 50-Hz supply
frequency as given in IEC 61000-4-15 [18]
y(t) = (A + m(t)) c(t)
= (A + M cos(wm t + φ)) sin(wc t)
(5)
where m(t) is the message signal, M is the amplitude of flicker,
wm is the flicker frequency, wc is the power system frequency,
and A is its amplitude. y(t) can also be expressed as
y(t) = A sin(wc t) +
M
[sin ((wc + wm )t + ϕ)
2
+ sin ((wc − wm )t + φ)] . (6)
The fluctuation of the voltage amplitude shown in (5) causes
the interharmonic frequencies (wc + wm ) and (wc − wm ) to
Fig. 25. Time waveform of (9) with A = 1, M = 0.1, and the same 50-Hz
signal with 45- and 55-Hz interharmonics.
appear in the frequency spectrum of v(t) as shown in (6).
In the case of any harmonics existing in the power system,
interharmonics also appear around the harmonics as shown in
the example for a second harmonic in (7) and (8). For the sake
of simplicity, it is assumed that the fundamental and the second
harmonic are in phase in (7) and (8).
y(t) = (A+M cos(wm t+φ)) [sin(wc t)+M2 sin(2wc t)]
(7)
where AM2 product is the amplitude of the second harmonic
component. y(t) can also be expressed as
y(t)
= A sin(wc t)
M
[sin ((wc +wm )t+ϕ)+sin ((wc −wm )t+φ)]
2
M M2
+AM2 sin(2wc t)
2
× [sin ((2wc +wm )t+ϕ)+sin ((2wc −wm )t+φ)] . . . .
+
(8)
This shows that any voltage fluctuation, which can be approximated as an AM, creates interharmonics around the fundamental and around the harmonics, if they exist. The reverse
is also true, i.e., if there are interharmonics close to the fundamental or the harmonics, they result in fluctuations in the signal
amplitude.
In the case of any interharmonics occurring on only one
side of the fundamental or the harmonics, signal amplitude
fluctuation also occurs. A single interharmonic at 55 Hz given
can be represented as an AM signal plus a low-amplitude
additive signal at 45 Hz, as explained in the following equation:
y(t) = A sin(2π50t) + M sin(2π55t)
= (A + M cos(2π5t)) sin(2π50t) − M sin(2π55t). (9)
Time waveforms of the 50-Hz signal with amplitude 1 with
additive 10% 55-Hz interharmonic and with additive 45-Hz
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 26. Sensitivity curve of the eye–brain set as a function of the frequency
of flicker.
interharmonic are shown in Fig. 25 up and down, respectively.
Both interharmonics create similar voltage amplitude fluctuations. According to IEC 61000-4-15, human eye is the most
sensitive to the voltage fluctuations around 8.8 Hz. The sensitivity is reduced as the flicker frequency deviates up and down
from 8.8 Hz, as shown in Fig. 26 [19]. Hence, interharmonics
approximately 10 Hz apart from the fundamental and also from
the harmonics give the highest contribution to the light flicker
problem.
Since experimentation on systems consisting of multi-EAFs
is very expensive and flicker calculations need long-term measurements (one point for Pst needs 10 min and one point
for Plt needs 2 h), a close correlation between current and
voltage interharmonics in the range of 60–90 Hz (subgroup
interharmonic—1), which is the main cause of flicker, will
be very useful. This correlation permits indirect estimation of
voltage flicker from the current interharmonic data collected for
a short time period. From the short-term current interharmonic
data, one can comment on the existence of flicker and also
on the variation of it. As it can be observed from Figs. 19
and 20, interharmonics around the fundamental are the most
dominant ones. Interharmonics around the second and third
harmonics are also significant. Therefore, the variations in
voltage interharmonics between the first and second components (60–90 Hz) against current interharmonics can give us
an idea about the mentioned correlation and, hence, the status
of the flicker. For various EAFs, voltage and current data
are simultaneously collected on the Medium Voltage (MV)
side of the furnace transformer (at MP1 in Fig. 16), and a
sample interharmonic scattered diagram for Plant-5 is shown
in Fig. 27. The bar charts of current interharmonic, voltage
interharmonic, and short-term flicker as a function of time at
Plant-5 are shown in Fig. 28. These plots show that there is a
good correlation between voltage and current interharmonics,
and therefore, the variations in current interharmonic content
can be used as a good indicator in estimating the state of the
flicker.
For proper design of SVC-type flicker compensation systems, the presence of these interharmonics should be taken
into consideration, particularly in the performance evaluation of
existing passive shunt second- and third-order harmonic filters,
as to be discussed in Section VIII.
In the evaluation of flicker contribution of each plant in
multiarc furnace operation, the harmonic and interharmonic
Fig. 27. Voltage interharmonic subgroup-1 versus current interharmonic
subgroup-1 (same data as in Fig. 28).
Fig. 28. (a) Current interharmonic subgroup-1 (10-min averages), (b) voltage
interharmonic subgroup-1 (10-min averages), and (c) short-term flicker (10-min
averages) for Plant-5 during the whole measurement period.
spectra will be obtained for each plant separately for a time
duration of 10 min (for short-term flicker computation Pst )
when all other plants are off.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
11
Fig. 29. Common harmonic filter topologies for SVC-type flicker compensation systems. (a) SVC Type-1. (b) SVC Type-2. (c) SVC Type-3.
VIII. A SSESSMENT OF THE P ERFORMANCE OF SVC-T YPE
F LICKER C OMPENSATION S YSTEMS
Practices of multinational SVC manufacturers can be summarized in three basic topologies shown in Fig. 29(a)–(c).
The basic difference between SVCs in Fig. 29(a) and (b)
is in the type of second harmonic filter. However, the SVC
in Fig. 29(c) does not include any second harmonic filter.
These three common practices of SVC-type flicker compensation systems will be investigated in this section in terms of
reactive power performance, harmonic filtering performance,
and flicker compensation performance by using synchronous
data collected in Plants 2, 3, and 5 according to the scenarios
described in Section IV.
A. Reactive Power Compensation Performance
It has been observed that SVC-type flicker compensation
systems perfectly compensate rapidly changing reactive power
demand of EAFs. The mean power factor (PF) of an EAF can
be kept at nearly unity by a well-designed SVC.
B. Harmonic Filtering Performance
First, frequency characteristics of passive shunt harmonic
filters in Fig. 29 are obtained by using parameters given in
design documents of SVC manufacturers for Plants 2, 3, and 5.
For this purpose, 1-A harmonic frequency is injected from the
Fig. 30. (a) Common-practice Type-1 model. (b) Frequency response of the
SVC. (c) Field data frequency spectra of the EAF and supply currents of ten
cycles from boring phase of EAF.
EAF side, and the corresponding harmonic current component
reflected to the supply side is computed [see Figs. 30(a), 36(a),
and 43(a)]. The current harmonic injected by EAF varies from
50 to 400 Hz in 63 × 10−4 steps. The resulting frequency
characteristics, as an example, the one in Fig. 30(b), should be
interpreted in the following manner.
1) For harmonic frequencies fn , the magnitude greater than
1 A in the supply side means an amplification, and less
than 1 A means attenuation. These filter characteristics
may be subjected to minor changes in time because of
drift in capacitance values owing to aging.
2) For each SVC type, sample harmonic contents of line
currents on both EAF side (MP2) and supply side (MP1)
are calculated for ten-cycle window from synchronously
collected data. The black-colored harmonic and interharmonic bars (5-Hz resolution) show the EAF side, and the
gray (or red) colored bars show the supply side. Therefore, for any harmonic frequency, if the gray-colored
bar is greater than the black-colored bar, the associated
harmonic is said to be amplified by SVC.
12
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 31. Second harmonic single-line component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
3) The raw data are calculated for a short period as defined
in Section IV when the other EAFs are off. Since the most
problematic harmonic is the second harmonic component
for all SVC types, single-line harmonic, harmonic subgroup, and harmonic group computations for the second
harmonic component are given in three different forms. In
the first group of plots, their variations are given against
time in the form of 1-s average data. Here, again, the
black-colored curves correspond to the EAF-side current
(MP2), and the gray-colored curves correspond to the
supply-side current (MP1). In the second group of characteristics, scattered diagrams for single line, harmonic
subgroup, and harmonic group for the second harmonic
component are given. Each point in a scattered diagram
corresponds to a ten-cycle window. For the harmonic
component higher than second (i.e., third, fourth, and
fifth), the filtering performances of SVCs are illustrated
by the curves in which the variations in each harmonic
subgroup are given against time. Here, again, the blackcolored curves stand for EAF side, and the gray (or red)
colored curves for supply side.
Below are the detailed analyses on the different SVC types
given in Fig. 29.
1) SVC Type-1: As it can be observed from Fig. 30(b), SVC
Type-1 amplifies all harmonics and interharmonics in the range
from 50 to 120 Hz. These expectations are confirmed from the
experimental data in Fig. 30(c) and Figs. 31–35. In scattered
diagrams, the diagonal of the graph, marked by a dashed line,
shows the case in which EAF harmonic is neither amplified
nor attenuated. Scattered points appearing densely above the
Fig. 32. Second harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 33. Second harmonic group component EAF (IEAF ) versus supply (IS )
currents, when other plants are off and SVC of the plant is on.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
13
Fig. 34. Third harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 36. (a) Common-practice Type-2 model. (b) Frequency response of the
SVC. (c) Field data frequency spectra of the EAF and supply currents of ten
cycles from boring phase of EAF.
Fig. 35. Fourth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
diagonal mean that filtering performance of the harmonic under
investigation is ineffective; that is, it amplifies EAF harmonics
to an extent observed from the associated scattered diagram. As
it can be seen from Figs. 34 and 35, SVC Type-1 filters out the
third and fourth harmonics, particularly the third one.
2) SVC Type-2: As it can be observed from Fig. 36(b),
the ranges of 50–95 Hz, 105–125 Hz, and 160–175 Hz, all
interharmonics are amplified by the SVC. This is verified by the
field data shown in Fig. 36(c) and Figs. 37–39. It is observed
that the single-line harmonic points at 100 Hz are scattered
equally around the diagonal, which shows that this component
is usually not amplified. On the other hand, the subgroup and
group harmonic computations show that a 100-Hz component
is amplified. This is due to the fact that, in subgroup and
group computations, interharmonics around 100 Hz are also
considered. As it can be seen from Figs. 40–42, SVC Type-2
filters out the third, fourth, and fifth harmonic components,
successfully.
3) SVC Type-3: As it can be observed from Fig. 43(b),
SVC Type-3 amplifies all harmonics and interharmonics in
the range of 50–130 Hz. A drastic amplification of second
harmonic occurs. This is the undesirable effect of the secondorder undamped third harmonic filter. This fact is verified by
14
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 37. Second harmonic single-line component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 38. Second harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 39. Second harmonic group component EAF (IEAF ) versus supply (IS )
currents, when other plants are off and SVC of the plant is on.
Fig. 40. Third harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Fig. 41. Fourth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
the experimental data shown in Figs. 44–46 for all harmonic
computation types (single line, harmonic subgroup, and harmonic group). Third, fourth, and fifth harmonic components are
filtered out as it can be seen in Figs. 47–49, respectively.
Table III summarizes the harmonic filtering performance
of SVC-type flicker compensation systems according to the
data collected in the field. The existing common practice for
SVCs cannot filter out the second harmonic subgroup, but
amplifies it. However, harmonic subgroup higher than second
can be filtered out successfully by a properly designed SVC.
One should never forget the effects of Thyristor Controlled
Reactor (TCR) on the aforementioned harmonic curves. An
SVC operating in the steady state (at constant firing angle α)
creates only odd harmonics, excluding third and its powers,
and the magnitudes of these harmonics are normally very low.
However, in the transient states, i.e., in boring and melting
periods, significant low harmonic components will also arise
because of asymmetrical consecutive half current cycles and
also unbalanced third harmonic components. In summary, TCR
harmonics are not necessarily in phase with EAF harmonics.
When they are superimposed, a higher or a lower harmonic
content than those of EAF may be obtained at all harmonic
and interharmonic frequencies. In the previous harmonic characteristics and waveforms, TCR harmonics were not taken into
account. Experimental points scattered more than the expected
one may be attributed to the TCR harmonics. During the field
tests, it was not possible to disconnect only the TCR part of
SVC from the network.
15
Fig. 42. Fifth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
C. Flicker Compensation Performance
In Section VII, it has been shown that current and voltage
interharmonics are correlated, i.e., if there are current interharmonics, then there are voltage interharmonics, and this leads
to light flicker. Since all three common practices of SVC-type
flicker compensation systems amplify the frequencies around
second harmonics as shown in Figs. 30(b), 36(b), and 43(b), a
flicker problem exists in all busbars supplying arc furnaces. The
amplification of interharmonics by the SVC system is shown in
Figs. 50 and 51. In this particular experiment, the SVC system
of Plant-2 is turned off, while the other plants are off. Ten-cycle
first interharmonics of both voltage and current (at MP1) are
computed for this interval to observe the effect of the SVC on
the interharmonics and, hence, the light flicker. Although the
SVC-type flicker compensation system is originally designed
to reduce the flicker level, due to the improper design of the
harmonic filters, (particularly the second harmonic filter), the
SVC systems amplify the interharmonics around the second
harmonic, which causes the light flicker effect. This phenomenon has been observed for all three common practices. It is
obvious that a novel design approach is required for filtering
the second harmonic components.
IX. PQ I NTERACTION B ETWEEN EAFs
IN M ULTIFURNACE O PERATIONS
In order not to face a significant PQ problem, during the
operation of EAF and multi-EAFs, among the site selection
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 44. Second harmonic single-line component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 43. (a) Common-practice Type-3 model. (b) Frequency response of the
SVC. (c) Field data frequency spectra of the EAF and supply currents of ten
cycles from boring phase of EAF.
criteria in the planning and design phase of EAF installation(s),
one of the most important criteria is the suitability and adequacy
of the grid to which the EAF(s) is going to be connected. The
well-known criteria in the selection of connection point to the
grid are as follows.
A. SCVD Method
Short-circuit voltage depression (SCVD) is usually expressed as the percentage voltage drop at PCC when EAF
goes from open circuit to short circuit on all three phases.
In order not to present a flicker problem, SCVD should be
≤ 2% at voltages ≤ 132 kV and ≤ 1.6% at higher voltages
(> 132 kV) [20]. SVCD value is directly proportional to the
sum of source impedance, impedances of power transformer
and EAF transformer, feeder impedance, reactance of series
reactor if present, and EAF secondary circuit impedance.
In the planning phase, the most important contribution to the
reduction of SCVD value is to connect EAF to one of the
strongest points of utility grid at the highest possible voltage
level.
Fig. 45. Second harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Fig. 46. Second harmonic group component EAF (IEAF ) versus supply (IS )
currents, when other plants are off and SVC of the plant is on.
17
Fig. 48. Fourth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
B. SCM V Amin /M V AEAF Ratio
Fig. 47. Third harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
In the literature, it is recommended by some researchers that
the ratio of SCM V Amin (minimum value of Short Circuit
Mega Volt-Ampere) to the total arc furnace Mega Volt-Ampere
(MVA) rating should not be lower than 80, while some others
suggest that it should not be lower than 50, in order not to cause
flicker, or to make the flicker problem solvable economically
[12], [13]. For the multifurnace system shown in Fig. 15, these
calculations have been made, and SCVD values are roughly
estimated to be as follows:
1) 1.74% SCVD if only the largest EAF is short circuited;
2) 3.4% SCVD if two EAFs are simultaneously short
circuited;
3) 6.6% SCVD if three EAFs are simultaneously short
circuited;
4) 8.4% SCVD if all EAFs are simultaneously short
circuited.
It is shown that the recommended SCVD values will be
exceeded in the case when more than one EAF are supplied
from the same point.
SCM V Amin /M V AEAF ratio is found to be 70 even for the
smallest EAF. When all EAFs are considered, this ratio drops
to a dramatic value of 8. It is seen that a wrong planning has
obviously been made for iron and steel plants’ site containing
multifurnaces. On this occasion, it is not possible to solve the
flicker problem at PCC even to reduce it by the use of SVCtype flicker compensation systems because of the interactions
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 50. Interharmonic subgroup-1 of the voltage waveform from melting
phase of Plant-2 (ten-cycle averages with five-cycle overlaps).
Fig. 51. Interharmonic subgroup-1 of the current waveform from melting
phase of Plant-2 (ten-cycle averages with five-cycle overlaps).
Fig. 49. Fifth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
TABLE III
H ARMONIC F ILTERING P ERFORMANCES OF T HREE C OMMON P RACTICES
(F: F ILTERED , A: A MPLIFIED )
between EAFs and amplifications of interharmonics by existing
second harmonic or third filter as discussed in Section VIII.
The experimental results obtained from these plants prove
these propositions indeed. Sample short-term (Pst ) and longterm (Plt ) flicker values collected for seven-day time periods
for multifurnace operation are shown in Fig. 52.
Obviously, Pst and Plt values are much higher than the limit
values given in the associated standards [9]. It is worth noting
that the SVC-type flicker compensation systems designed by
multinational companies have been in operation during the
measurement period. Despite these facts, these EAFs are operating and producing millions of tones of steel every year. This
problem cannot be solved with current technology, but it can be
made less serious by reorganizing the structure of EAF power
Fig. 52. Seven-day flicker variation at PCC supplying multi-EAFs: (a) Pst
and (b) Plt .
system in this region. That is, nine EAFs in five iron and steel
plants can be subdivided in the three groups for connection to
three different points of the utility grid. Furthermore, transmission voltage level at PCCs should be upgraded from 154 to
400 kV. One further countermeasure is needed in reducing
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
flicker. That is, a new power plant installation with 1000-MW
installed capacity seems to be inevitable in addition to the
existing two thermal plants and one natural gas plant located
around this region.
X. C ONCLUSION
The following conclusions can be drawn from the results of
intensive experimental work carried out in the field on both
single-furnace and multifurnace plants.
1) In order to avoid flicker, the most critical step is the
planning stage of EAF installations. For the candidate
connection point of EAF(s) to utility grid, first, simple
calculations of SCVD and SCM V Amin /M V AEAF ratio
are to be carried out. These values should be safely lower
than the recommended values, because after installation
of SVC-type flicker compensation systems, flicker will
normally be increased.
2) An SVC-type flicker compensation system can compensate satisfactorily the rapidly changing reactive power
demand of EAFs and keep the PF nearly at unity.
3) Passive shunt filters of carefully designed SVCs can
successfully filter out harmonic current components produced by EAFs except second harmonic. The widely
applied passive shunt filter topologies are experimentally
proven to lead to amplification of second harmonic subgroup and groups even to the amplification of single-line
second harmonic component for many cases. In SVCtype flicker compensation systems, second harmonic filter
seems to be integrated into the system not for the purpose
of attenuation of the second harmonic component but
to limit its magnitude owing to the third harmonic filter
magnification.
4) In EAF installations, the major cause of the light flicker is
interharmonics around the existing harmonics. Therefore,
interharmonics primarily between fundamental and second harmonic components, secondarily between second
and third harmonic components, are the causes of flicker.
Since interharmonics between fundamental and second
harmonic components are significantly amplified by all
widely used passive filters, the operation of the SVCtype flicker compensation system is shown to increase the
flicker level at PCC. Therefore, one can conclude that the
known SVC-type flicker compensation systems cannot be
a solution to an existing flicker problem of single and
multi-EAF installations.
5) Because of the interaction between several SVCs and
EAFs during multifurnace operation light flicker, interharmonics and second harmonic subgroup are more
complex and usually more drastic in comparison with
single EAF operation. The best approach to solve these
problems is to avoid or minimize these risks in the
planning phase by selecting the most proper connection
point in the utility grid for EAF installation. To solve
flicker, interharmonics, and second harmonic problems of
the existing EAF installations, new active devices such
as active-power-filter D-STATCOM systems should be
exercised.
19
ACKNOWLEDGMENT
The authors would like to thank the arc furnace plant authorities in the Izmir/Aliağa region of Turkey for supplying
the opportunity of field measurements and their collaborative
work of making the PCC measurements during various operating conditions of the plants. This research and technology
development work is carried out as a subproject of the National
Power Quality Project of Turkey.
R EFERENCES
[1] J. G. Mayordomo, E. Prieto, A. Hernandez, and L. F. Beites, “Arc furnace
characterization from an off-line analysis of measurements,” in Proc.
IEEE 9th Int. Conf. Harmonics Quality Power, Orlando, FL, Oct. 2000,
pp. 1073–1078.
[2] P. E. Issouribehere, F. Issouribehere, and G. A. Barbera, “Power quality
and operating characteristics of electric arc furnaces,” in Proc. IEEE
Power Eng. Soc. General Meeting, 2005, pp. 784–791.
[3] P. E. Issouribehere, J. C. Barbero, G. A. Barbera, and F. Issouribehere,
“Compatibility between disturbance emission and Argentinian power
quality regulations in iron and steel industries,” in Proc. IEEE/PES, TDC
(Latin America), pp. 1–6.
[4] B. Boulet, J. Wikston, and L. Kadar, “The effect of measuring system
accuracy on power quality measurements in electric arc furnaces,” in
Conf. Rec. IEEE IAS Annu. Meeting, 1997, pp. 2151–2155.
[5] A. Hernandez, J. G. Mayordomo, R. Asensi, and L. F. Beites, “A
method based on interharmonics for flicker propagation applied to arc
furnaces,” IEEE Trans. Power Del., vol. 20, no. 3, pp. 2334–2342,
Jul. 2005.
[6] Testing and Measurement Techniques-Power Quality Measurement
Methods, IEC 61000-4-30, 2003.
[7] E. Özdemirci, Y. Akkaya, B. Boyrazoglu, S. Buhan, A. Terciyanli,
O. Unsar, E. Altintas, B. Haliloglu, A. Acik, T. Atalik, Ö. Salor,
T. Demirci, I. Cadirci, and M. Ermis, “Mobile monitoring system to take
PQ snapshots of Turkish electricity transmission system,” in Proc. IEEE
IMTC, Warsaw, Poland, 2007, pp. 1–6.
[8] T. Demirci, A. Kalaycıoğlu, Ö. Salor, S. Pakhuylu, M. Dagh,
T. Kara, H. S. Aksuyek, C. Topcu, B. Polat, S. Bilgen, S. Umut,
I. Cadirci, and M. Ermis, “National PQ monitoring network for Turkish
electricity transmission system,” in Proc. IEEE IMTC, Warsaw, Poland,
2007, pp. 1–6.
[9] Turkish Electricity Transmission System Supply Reliability and
Quality Regulation, 2004. Last accessed on December 12, 2009. [Online].
Available: http://www.teias.gov.tr/yonetmelikler/supply.doc
[10] IEEE Recommended Practices and Requirements for Harmonic Control
in Electrical Power Systems, IEEE Std. 519-1992, 1992.
[11] Testing and Measurement Techniques—General Guide on Harmonics
and Interharmonics Measurements and Instrumentation, for Power
Supply Systems and Equipment Connected Thereto, IEC 61000-4-7,
2002.
[12] B. Bharat, “Arc furnace flicker measurement and control,” IEEE Trans.
Power Del., vol. 8, no. 1, pp. 400–410, Jan. 1993.
[13] S. R. Mendis, M. T. Bishop, and J. F. Witte, “Investigations of voltage
flicker in electric arc furnace power systems,” IEEE Ind. Appl. Mag.,
vol. 2, no. 1, pp. 28–38, Jan./Feb. 1996.
[14] T. Keppler, N. R. Watson, J. Arrillaga, and S. Chen, “Theoretical assessment of light flicker caused by sub- and interharmonic frequencies,” IEEE
Trans. Power Del., vol. 18, no. 1, pp. 329–333, Jan. 2003.
[15] T. Tayjasanant, W. Wang, and C. Li, “Interharmonic-flicker curves,” IEEE
Trans. Power Del., vol. 20, no. 2, pp. 1017–1024, Apr. 2005.
[16] J. A. Pomilio and S. M. Deckman, “Flicker produced by harmonics
modulation,” IEEE Trans. Power Del., vol. 18, no. 2, p. 67,
Apr. 2003.
[17] A. Testa, D. Gallo, and R. Langella, “On the processing of harmonics and
interharmonics: Using Hanning window in standard framework,” IEEE
Trans. Power Del., vol. 19, no. 1, pp. 28–34, Jan. 2004.
[18] Testing and Measurement Techniques-Flickermeter- Functional and
Design Specifications, IEC 61000-4-15, 1998.
[19] G. Diez, L. I. Eguiluz, M. Manana, J. C. Lavandero, and A. Ortiz,
“Instrumentation and methodology for revision of European flicker
threshold,” in Proc. 10th Int. Conf. Harmonics Quality Power, 2002,
pp. 262–265.
[20] T. J. E. Miller, Reactive Power Control in Electric Systems. NewYork:
Wiley-Interscience, 1982.
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Özgül Salor (S’98–M’05) received the B.Sc., M.Sc.,
and Ph.D. degrees in electrical engineering from the
Middle East Technical University, Ankara, Turkey, in
1997, 1999, and 2005, respectively.
From 2001 to 2003, she was a Professional Researcher at the University of Colorado, Boulder.
Since 2006, she has been with the Power Electronics
Department, TÜBİTAK UZAY Research Institute,
The Scientific and Technological Research Council
of Turkey (TÜBİTAK), Ankara, where she is currently a Chief Senior Researcher. She is also a parttime Lecturer in the Department of Electrical and Electronics Engineering,
Gazi University, Ankara. Her research interests are speech-signal processing
and signal processing for power quality.
Burhan Gültekin (S’03) received the B.Sc. and
M.Sc. degrees in electrical and electronics engineering from the Middle East Technical University,
Ankara, Turkey, in 2000 and 2003, respectively,
where he is currently working toward the Ph.D.
degree.
He is currently a Chief Senior Researcher in the
Power Electronics Department, TÜBİTAK UZAY
Research Institute, The Scientific and Technological
Research Council of Turkey (TÜBİTAK), Ankara.
His areas of research are in reactive power compensation systems and power quality issues.
Tevhid Atalık received the B.Sc. degree in electrical
and electronics engineering from Uludað University,
Bursa, Turkey, in 2000, and the M.Sc. degree in electrical and electronics engineering from Hacettepe
University, Ankara, Turkey, in 2003. He is currently
working toward the Ph.D. degree at Başkent University, Ankara.
He is currently a Senior Researcher in the Power
Electronics Department, TÜBİTAK UZAY Research
Institute, The Scientific and Technological Research
Council of Turkey (TÜBİTAK), Ankara. His areas of
research include power quality analysis and hardware design.
Adnan Açık received the B.Sc. and M.Sc. degrees
in electrical and electronics engineering from the
Middle East Technical University, Ankara, Turkey,
in 1995 and 1998, respectively.
He is currently a Chief Senior Researcher in the
Power Electronics Department, TÜBİTAK UZAY
Research Institute, The Scientific and Technological
Research Council of Turkey (TÜBİTAK), Ankara.
His main areas of research are in power quality and
switch-mode power supplies.
Serkan Buhan received the B.Sc. degree in electrical and electronics engineering from Hacettepe
University, Ankara, Turkey, in 2005, where he is
currently working toward the M.Sc. degree in power
quality.
He is currently a Researcher in the Power Electronics Department, TÜBİTAK UZAY Research Institute, The Scientific and Technological Research
Council of Turkey (TÜBİTAK), Ankara. His areas
of research include power quality analysis using
wavelets.
Alper Terciyanlı (S’03) received the B.Sc. and
M.Sc. degrees in electrical and electronics engineering from the Middle East Technical University,
Ankara, Turkey, in 2001 and 2003, respectively,
where he is currently working toward the Ph.D.
degree in medium-voltage ac motor drives.
He is currently a Chief Senior Researcher in the
Power Electronics Department, TÜBİTAK UZAY
Research Institute, The Scientific and Technological
Research Council of Turkey (TÜBİTAK), Ankara.
His areas of research include reactive power compensation systems and power quality issues.
Burak Boyrazoğlu received the B.Sc. degree in
electrical and electronics engineering from the
Middle East Technical University, Ankara, Turkey,
in 2005.
From 2006 to 2008, he was a Researcher in the
Power Electronics Department, TÜBİTAK UZAY
Research Institute, The Scientific and Technological
Research Council of Turkey (TÜBİTAK), Ankara.
Currently, he is with Renaissance Constructions,
Moscow, Russia.
Özgür Ünsar (S’07) received the B.Sc. degree
in electrical and electronics engineering from the
Middle East Technical University, Ankara, Turkey,
in 2006. He is currently working toward the M.Sc.
degree at Hacettepe University, Ankara.
He is currently a Researcher with the Turkish
Electricity Transmission Corporation (TEIAŞ),
Ankara. His current areas of research include power
quality measurement and analysis.
Tolga İnan received the B.Sc. and M.Sc. degrees
in electrical and electronics engineering from the
Middle East Technical University, Ankara, Turkey,
in 2000 and 2003, respectively, where he is currently working toward the Ph.D. degree in 3-D face
recognition.
He is currently a Senior Researcher in the Power
Electronics Department, TÜBİTAK UZAY Research
Institute, The Scientific and Technological Research
Council of Turkey (TÜBİTAK), Ankara. His areas
of research include pattern recognition, computer
vision, machine learning, and power quality analysis.
Erinç Altıntaş received the B.Sc. degree in electrical and electronics engineering from the Middle
East Technical University, Ankara, Turkey, in 2006,
where he is currently working toward the M.Sc.
degree.
He is currently a Researcher with the Turkish
Electricity Transmission Corporation (TEIAŞ),
Ankara. His current areas of research include power
quality measurement and analysis.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Yener Akkaya received the B.Sc. degree in electrical
and electronics engineering from Istanbul Technical University, Istanbul, Turkey, in 1989, and completed the Public Administration Master Program at
TODAIE, Ankara, Turkey, in 1997.
Since 1989, he has been with the Turkish Electricity Transmission Corporation (TEIAŞ), Ankara,
where he was with the Administration and Maintenance Department and has been the Director of the
Research and Development Department since 2003.
His current research interests are power quality and
transmission system planning.
Ercüment Özdemirci received the B.Sc. and M.Sc.
degrees in electrical and electronics engineering
from Fýrat University, Elazýð, Turkey, in 1998 and
2001, respectively.
From 1998 to 2003, he was with the Department
of Load Dispatch, Turkish Electricity Transmission
Corporation (TEIAŞ), Ankara, Turkey, where he is
currently in the Department of Transmission Planning. His current research interests are power quality, load-frequency control, and transmission system
planning.
21
Işık Çadırcı (M’98) received the B.Sc., M.Sc.,
and Ph.D. degrees in electrical and electronics
engineering from the Middle East Technical
University, Ankara, Turkey, in 1987, 1988, and 1994,
respectively.
She is currently a Professor of electrical engineering at Hacettepe University, Ankara, and also
the Head of the Power Electronics Department,
TÜBİTAK UZAY Research Institute, The Scientific and Technological Research Council of Turkey
(TÜBİTAK), Ankara. Her areas of interest include
electric motor drives, switch-mode power supplies, and power quality.
Dr. Çadırcı received the 2000 Committee Prize Paper Award from the Power
Systems Engineering Committee of the IEEE Industry Applications Society and
also the IEEE Industry Applications Magazine Prize Paper Award, Third Prize,
in 2007.
Muammer Ermiş (M’99) received the B.Sc., M.Sc.,
and Ph.D. degrees in electrical engineering from the
Middle East Technical University (METU), Ankara,
Turkey, in 1972, 1976, and 1982, respectively, and
the M.BA. degree in production management from
Ankara Academy of Commercial and Economic Sciences, Ankara, in 1974.
He is currently a Professor of electrical engineering at METU. He is also currently the Manager of
the National Power Quality Project of Turkey. His
current research interest is electric power quality.
Dr. Ermiş received the “The Overseas Premium” paper award from the
Institution of Electrical Engineers, U.K., in 1992, and the 2000 Committee
Prize Paper Award from the Power Systems Engineering Committee of the
IEEE Industry Applications Society. He was the recipient of the 2003 IEEE
PES Chapter Outstanding Engineer Award.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
1
Electrical Power Quality of Iron
and Steel Industry in Turkey
Özgül Salor, Member, IEEE, Burhan Gültekin, Student Member, IEEE, Serkan Buhan, Burak Boyrazoğlu,
Tolga İnan, Tevhid Atalık, Adnan Açık, Alper Terciyanlı, Student Member, IEEE,
Özgür Ünsar, Student Member, IEEE, Erinç Altıntaş, Yener Akkaya, Ercüment Özdemirci,
Işık Çadırcı, Member, IEEE, and Muammer Ermiş, Member, IEEE
Abstract—The iron and steel industry has been growing increasingly in Turkey in the last decade. Today, its electricity demand is
nearly one tenth of the installed generation capability of 40 GW in
the country. In this paper, power quality (PQ) investigations based
on the arc furnace installations of the iron and steel plants using
field measurements according to the international standard IEC
61000-4-30 are documented. Interharmonics and voltage flicker
problems occurring both at the common-coupling points of those
plants and at the arc furnace and static var compensator (SVC)
systems of the plants themselves are determined with the use
of GPS receiver synchronization modules attached to the mobile
PQ measurement systems. It has been observed that flicker and
interharmonic problems are dominant at the points of common
Paper PID-2009-04, presented at the 2007 Industry Applications Society
Annual Meeting, New Orleans, LA, September 23–27, and approved for
publication in the IEEE T RANSACTIONS ON I NDUSTRY A PPLICATIONS by
the Metals Industry Committee of the IEEE Industry Applications Society.
Manuscript submitted for review November 30, 2007 and released for publication June 22, 2009. This work was supported by the Public Research Grant
Committee (KAMAG) of The Scientific and Technological Research Council
of Turkey (TÜBİTAK).
Ö. Salor and A. Açık are with the Power Electronics Department,
TÜBİTAK UZAY Research Institute, The Scientific and Technological Research Council of Turkey (TÜBİTAK), 06531 Ankara, Turkey (e-mail: ozgul.
salor@uzay.tubitak.gov.tr; adnan.acik@uzay.tubitak.gov.tr).
B. Gültekin, T. İnan, and A. Terciyanlı are with the Middle East Technical University, 06531 Ankara, Turkey, and also with the Power Electronics
Department, TÜBİTAK UZAY Research Institute, The Scientific and Technological Research Council of Turkey (TÜBİTAK), 06531 Ankara, Turkey
(e-mail: burhan.gultekin@uzay.tubitak.gov.tr; tolga.inan@uzay.tubitak.gov.tr;
alper.terciyanli@uzay.tubitak.gov.tr).
S. Buhan and I. Çadırcı are with Hacettepe University, 06532 Ankara,
Turkey, and also with the Power Electronics Department, TÜBİTAK UZAY Research Institute, The Scientific and Technological Research Council of Turkey
(TÜBİTAK), 06531 Ankara, Turkey (e-mail: serkan.buhan@uzay.tubitak.gov.
tr; isik.cadirci@uzay.tubitak.gov.tr).
B. Boyrazoğlu is with Renaissance Constructions, Moscow, Russia (e-mail:
burak.boyrazoglu@uzay.tubitak.gov.tr).
T. Atalık is with Başkent University, 06530 Ankara, Turkey, and also with
the Power Electronics Department, TÜBİTAK UZAY Research Institute, The
Scientific and Technological Research Council of Turkey (TÜBİTAK), 06531
Ankara, Turkey (e-mail: tevhid.atalik@uzay.tubitak.gov.tr).
Ö. Ünsar is with Hacettepe University, 06532 Ankara, Turkey, and also
with the Turkish Electricity Transmission Corporation (TEIAŞ), 06100 Ankara,
Turkey (e-mail: ozgur.unsar@yahoo.com.tr).
E. Altıntaş is with the Middle East Technical University, 06531 Ankara,
Turkey, and also with the Turkish Electricity Transmission Corporation
(TEIAŞ), 06100 Ankara, Turkey (e-mail: erincaltintas@gmail.com).
Y. Akkaya and E. Özdemirci are with the Turkish Electricity Transmission
Corporation (TEIAŞ), 06100 Ankara, Turkey (e-mail: yener.akkaya@teias.
gov.tr; ercument.ozdemici@teias.gov.tr).
M. Ermiş is with the Middle East Technical University, 06531 Ankara,
Turkey (e-mail: ermis@metu.edu.tr).
Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TIA.2009.2036547
couplings where arc furnace installations are supplied. Based on
the field measurements obtained with collaborative work of five
arc furnace plants, it is possible to say that contemporary SVC
systems cause interharmonic amplification problems around the
second harmonic, and novel methods are required to solve this
problem.
Index Terms—Arc furnace, flicker, group harmonic,
interharmonic–flicker relation, interharmonics, iron and steel
industry, ladle furnace, power quality (PQ), single-line harmonic,
subgroup harmonic.
I. I NTRODUCTION
HE iron and steel industry has been growing increasingly
in Turkey in the last decade. Today, its electricity demand
is nearly one-tenth of the installed generation capability of
40 GW in the country. Steel production in Turkey is based on
extensive use of arc and ladle furnaces in most of the plants,
which is the cause of power quality (PQ) problems at those
locations of the Turkish Electricity Transmission System.
PQ of electric arc furnaces (EAF) has been investigated
previously by some other researchers [1]–[5]. Arc furnace
characterization of one plant has been achieved in [1] in terms
of PQ parameters given in the IEC standard 61000-4-30 [6]. In
[2], different phases of EAF operation connected to the 13.5-kV
voltage level have been considered for obtaining a single-phase
equivalent circuit of the EAF.
In [3], the compatibility between the PQ disturbance levels
and the Argentinean regulations for EAF operation has been
considered. Measuring system accuracy for PQ of EAF installations has been investigated in [4]. In [5], flicker propagation
in the network based on interharmonic analysis on arc furnaces
is introduced.
In this paper, we present very detailed and extensive investigations and results obtained from the PQ of arc furnace installations in Turkey. The main focus is the investigation of the PQ
problems caused by the iron and steel industry plants connected
directly to the Turkish Electricity Transmission System. The
critical points of the transmission system are being monitored
by the mobile PQ monitoring systems developed through the
National Power Quality Monitoring Project [7]. By taking oneweek snapshots of all PQ parameters specified in IEC 610004-30 [6], PQ of the iron and steel plants has been assessed.
Based on this assessment, detailed investigation on the selected
five plants supplied from the same busbar has been carried
out. Raw data of voltage and current waveforms have been
T
0093-9994/$26.00 © 2010 IEEE
2
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 1. Location of iron and steel plants on the Turkish Electricity Transmission System.
collected for approximately 2 h at each plant based on a measurement schedule. This schedule requires collaborative work
of all plants, since the arc furnace operation at the plants other
than the measured one was stopped for 15 min. Contribution
of the flicker and harmonics of each plant could be observed
using these measurements, while it is also possible to evaluate
the effectiveness or inefficiencies of the static-var-compensator
(SVC)-type flicker compensation systems. It has been shown
that, with the common practices of compensation systems, it is
not possible to solve the flicker problem at the point of common
coupling (PCC) from where arc furnaces are supplied.
Section II presents the general overview of the PQ of the
iron and steel plants in Turkey. In Section III, description of the
selected plants is given for detailed investigation. Measurement
scenarios at those plants are presented in Section IV. In
Section V, observations on the harmonic content of the EAFs on
the electric network are given. Sections VI and VII summarize
the harmonic computation methods used based on IEC 610004-30, and flicker–interharmonic relationship observations are
presented, respectively, from theoretical and experimental perspectives. Assessment of the performance of SVC-type flicker
compensation systems installed at EAF plants in terms of
reactive power compensation, harmonic filtering performance,
and flicker compensation performance is explained in detail in
Section VIII. Section IX presents the PQ interaction of EAFs in
multifurnace operations.
II. C OUNTRYWIDE PQ S NAPSHOT OF I RON
AND S TEEL P LANTS
Major iron and steel plants are marked on the map of the
Turkish Electricity Transmission System in Fig. 1. Steel production in only four of these plants is based on blast furnaces.
At three points or regions of the Turkish Electricity System,
multifurnace operation takes place. PQ of all of those plants
has been investigated based on the field measurements carried
out according to IEC 61000-4-30 for Class B performance by
using the mobile monitoring systems [7]. By the end of year
2008, the National Power Quality Monitoring Center started
to operate for remote monitoring of the Turkish Electricity
Transmission System and its customers by permanent monitors
designed through the National Power Quality Project [8]. This
system will monitor the feeders of heavy industry, including
iron and steel plants, continuously.
The PQ measurements have been carried out at 400 kV, and
154-kV PCCs for iron and steel plants. From the results of
Fig. 2. Long- and short-term flicker cumulative probability function for some
plants connected to different PCCs at 400 kV.
the continuous PQ measurements lasting seven days at major
transformer substations supplying power to arc furnace plants,
the following problems have been identified.
1) Although almost all of the plants are equipped with
modern SVC systems, measured flicker and current total
demand distortion (current TDD) values exceed the limits
specified in the Turkish Electricity Transmission System
Supply Reliability and Quality Regulation [9], which
complies with the IEEE Std. 519-1992 [10]. The problem
is more serious at transformer substations or busbars
supplying multiple arc furnaces as shown in Figs. 2–14.
Cumulative probability function CPF(x) in the figures
indicates the percentage of the total measurement time for
which the measured parameter is below a value x, given
in the horizontal axis. All harmonic analyses have been
carried out using the single-line harmonic components
directly in this part of the work. Single-line harmonic
frequency concept is presented in IEC 61000-4-7 [11].
Different harmonic analysis techniques given in [11]
are summarized in Section VI. Since the power system
frequency in Turkey is 50 Hz, ten-cycle Discrete Fourier
Transform (DFT) computation is used as suggested in
IEC 61000-4-30 [6].
2) In all arc furnace installations, the second harmonic current component at the PCC exceeds the limit values even
after filtration. Current waveforms of arc furnaces are rich
in interharmonics at low frequencies, particularly in melting state. For instance, the dominant flicker modulation
frequency of 8.8 Hz causes interharmonics in line current
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
3
Fig. 6. Fourth harmonic cumulative probability function for some plants
connected to different PCCs at 154 kV.
Fig. 3. Long- and short-term flicker cumulative probability function for some
plants connected to different PCCs at 154 kV.
Fig. 7. Fifth harmonic cumulative probability function for some plants connected to different PCCs at 154 kV.
Fig. 4. Second harmonic cumulative probability function for some plants
connected to different PCCs at 154 kV.
Fig. 8. Primary current TDD cumulative probability function for some plants
connected to different PCCs at 154 kV.
Fig. 5. Third harmonic cumulative probability function for some plants
connected to different PCCs at 154 kV.
waveforms at frequencies of f = 50k ± 8.8 Hz, where
k = 1, 2, 3, . . .. This fact has also been pointed out by
some other researchers [14], [15]. Some of these lowfrequency interharmonic components in the line currents
are obviously amplified when attempted to be filtered out
by C-type second harmonic and second-order third harmonic filters. On this occasion, the causes of undesirably
high values of voltage flicker, and current harmonics and
interharmonics at PCC have been investigated not only
for multi-furnace installations but also for single EAF
operation. The findings and the related discussion will
be reported in the following sections. Mitigation methods
will be discussed within the scope of another paper.
4
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 9. Primary current TDD cumulative probability function for a plant
connected to a 154-kV PCC.
Fig. 10. Second harmonic cumulative probability function for a plant connected to a 400-kV PCC.
Fig. 11. Third harmonic cumulative probability function for a plant connected
to a 400-kV PCC.
III. D ESCRIPTION OF S ELECTED P LANTS
FOR D ETAILED I NVESTIGATION
As a result of these observations, five plants with arc furnace
installations which are supplied from the same busbar of the
transmission system are selected for further investigations on
the PQ parameters. These five plants are those on the western
side of Turkey (İzmir/Aliağa region), as shown on the map in
Fig. 1. Single-line diagram of the five plants is shown in Fig. 15.
IV. M EASUREMENT S CENARIOS
AT THE S ELECTED P LANTS
The measurements at the five selected plants were organized
with a collaborative effort of all plants. At each plant, raw
Fig. 12. Fourth cumulative probability function for a plant connected to a
400-kV PCC.
Fig. 13. Fifth harmonic cumulative probability function for a plant connected
to a 400-kV PCC.
Fig. 14. Primary current TDD cumulative probability function for a plant
connected to a 400-kV PCC.
data of currents and voltages are recorded for approximately
2 h. During this 2-h period, other four plants were organized
such that they stop furnace operation and their SVC systems
for 15 min at the same time. Three-phase current and voltage
measurements are collected at both the supply side and the
plant side. Arc furnaces, ladle furnaces, where applicable, and
SVC unit currents and voltages are recorded separately. All
measurements are synchronized by a GPS receiver module.
This measurement process is repeated at each one of the five
selected plants. Measurement points are as shown in Fig. 16.
The 15-min off period of the other plants connected to the
same bus guarantees that, during this period, if any current
harmonics or interharmonics are observed at the SVC unit
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Fig. 15. Single-line diagram of the selected five plants.
5
Power (UHP) EAF, together with its flicker compensation system, are shown in Fig. 17 over one tap-to-tap period. Furnace
charging, boring, melting, and refining periods are apparent
from these records. Seven-day flicker and current TDD variations of the same EAF + SVC installation (36 kV) are shown
in Fig. 18.
IEC 61000-4-30 gives the ten-cycle (for 50-Hz systems)
gapless harmonic and interharmonic subgroup measurement,
denoted in IEC 61000-4-7 as the basic measurements for classA performance.
In IEC-61000-4-7, however, three different methods of harmonic and interharmonic computation practices are given. In
the case of fluctuating harmonics and interharmonics, these
three methods give close but different results, which may
affect the performance of spectrum estimations significantly
for different cases of harmonic and interharmonic contents of
the signal. These three computation methods are summarized
briefly in the following.
1) Harmonic and interharmonic groups:
Harmonic group denoted by Gg,n is the square root
of the sum of the squares of a harmonic and the spectral components adjacent to it within the time window,
such that
Fig. 16. Synchronous measurement points at a typical EAF plant.
(Measurement Point 3) or the supply side of the plant (Measurement Point 1), those harmonics and interharmonics are mainly
the result of the EAF operation only at the measured plant.
This type of measurement can be used to understand whether
the plant is a harmonic source or a harmonic sink on the
electricity transmission network, when the frequency spectra
of the currents recorded with all plants in operation and with
four of them out of operation are compared. It is also possible
to detect any ineffectiveness of the SVCs at the measured plant
using the same comparison.
In order to observe the effectiveness of the SVC system, SVC
of the current plants is turned off and on during the 15-min
idle period of other plants and also when other plants are in
operation. This brings out four cases of measurements at every
plant: other plants on, SVC on; other plants on, SVC off;
other plants off, SVC on; and other plants off, SVC off. The
measurement periods are summarized in Table I. When there
are more than one arc furnace and ladle furnace at a plant, arc
furnaces and their SVCs other than the measured arc furnace
were turned off during the periods when other plants were off.
This measurement scenario has been a very costly practice,
since the plants had to be turned off four times for a 15-min
period, 1 h in total, while data were collected at every one of
the other four plants. Moreover, turning off the SVC of the
measured plant was required twice: first while the other plants
are operative and second while they are inoperative. Moreover,
turning off the SVCs causes inefficiencies of the EAF operation,
which brings additional expenses.
V. ARC F URNACES AS H ARMONIC S OURCES
ON THE N ETWORK
EAF is the most problematic load on the electric network.
Active and reactive power consumptions of an Ultra High
G2g,n =
4
2
C2
Ck−5
2
+
Ck+i
+ k+5
2
2
i=−4
(1)
for 50-Hz power systems, where Ck is the rms of amplitude of the (k)th spectral component obtained from the
DFT for the (n = k/10)th harmonic component. (Since
the resolution is 5 Hz and the system frequency is 50 Hz,
every 10th DFT sample corresponds to a harmonic, i.e.,
10th is the fundamental, 20th is the second harmonic, and
so on.)
Similarly, interharmonic group is defined as
9
2
=
Cig,n
2
Ck+i
(2)
i=1
for 50-Hz power systems, where Ck+i is the (k + i)th
DFT sample, and they are the DFT samples between the
(n)th and the (n + 1)th harmonics (for example, nine
adjacent DFT samples between 55 and 95 Hz for the
interharmonics between second and third harmonics).
2) Harmonic and interharmonic subgroups:
The harmonic grouping considers only the previous
and the next DFT components around the harmonic component itself
1
G2sg,n =
2
Ck+i
.
(3)
i=−1
In the interharmonic subgroup case, the effects of
fluctuations of harmonic amplitudes and phases are partially reduced by excluding the components immediately
adjacent to the harmonic frequencies
2
=
Cisg,n
8
i=2
2
Ck+i
.
(4)
6
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
TABLE I
M EASUREMENT S CHEDULE (P HASES OF THE EAF: C—C HARGING , B—B ORING , M—M ELTING , AND R—R EFINING )
Fig. 17. Active and reactive power consumptions of a UHP EAF together with
its flicker compensation system in one tap-to-tap period (1-s averages).
3) Single-line harmonic frequency:
This is the single-line measurement of the current or
voltage frequency amplitude component obtained directly
from the 5-Hz-resolution DFT samples according to IEC
61000-4-7.
The spectra in Figs. 19–21 are calculated from the
current data measured in boring, melting, and refining periods, respectively. Fig. 22 shows a pictorial explanation
of the harmonic and interharmonic group and subgroup
concepts. The spectrum in the figure is taken from the
current spectrum of the boring phase shown in Fig. 19.
The harmonic and interharmonic group and subgroup
values obtained from the current waveform in Fig. 19 are
given in Table II.
As observed from Table II, there is a drastic difference
between single line and subgroup, as well as single line and
group harmonic current components particularly for the second
harmonic. However, IEEE Std 519-1992 and Turkish Std 2004
[9] are not defined in the given current harmonic penalty limits
whether these are calculated as subgroup, group, or singleline components. This is the case for most of the research
papers given in the literature, as well. Therefore, the standards
mentioned earlier need to be revised so as to define the limit
Fig. 18. Seven-day (a) current TDD, (b) short-term flicker (Pst ), and (c) longterm flicker (Plt ) variations of UHP EAF.
values according to IEC 61000-4-7 as harmonic subgroups. On
the other hand, in the design and performance assessment of
SVC-type flicker compensation systems applied to the EAFs, it
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Fig. 19. Ten-cycle waveform of the line current of the EAF during boring
phase and its DFT with 5-Hz resolution.
7
Fig. 22. Illustration of the harmonic and interharmonic group and subgroup
computations.
TABLE II
H ARMONIC AND I NTERHARMONIC C OMPUTATIONS FOR L INE C URRENT
OF EAF IN B ORING P HASE S HOWN IN F IG . 21
Fig. 20. Ten-cycle waveform of the line current of the EAF during melting
phase and its DFT with 5-Hz resolution.
in the definition of harmonic limits brings together serious
difficulties in the design and performance evaluation of passive
shunt second and third harmonic filters of SVC-type flicker
compensation systems as will be discussed in Section VIII.
Measurements obtained at MP2 in Fig. 16 show that harmonic contents of EAFs are very rich. Particularly low order
current harmonics such as second and third are observed to
be significant. Sample results for boring, melting, and refining
periods of a High Power (HP) EAF are shown in Fig. 23.
The richest harmonic content and TDD have been obtained for
boring period. Since electric arc is highly stable during refining,
the best harmonic content and TDD values have been obtained
for the refining period.
Fig. 21. Ten-cycle waveform of the line current of the EAF during refining
phase and its DFT with 5-Hz resolution.
is important to consider whether interharmonics and associated
harmonic components injected to the supply side are calculated
as single line or subgroup.
The rich interharmonic content between fundamental and
second single-line harmonic frequency, and the lack of clarity
VI. H ARMONIC C ONTENT C OMPUTATION
BASED ON IEC 61000-4-7
The mobile systems collecting the voltage and current waveform data are sampling the data at a frequency of 3200 Hz. This
sampling rate corresponds to 64 samples per cycle; however,
8
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 23. Sample results for boring, melting, and refining periods of an HP EAF (harmonic subgroups, ten-cycle averages with five-cycle overlapping windows).
when the supply frequency deviates from 50 Hz, a single cycle
of the waveform is covered by more or less than 64 samples.
This loss of synchronization causes leakage on the DFT samples due to the picket fence effect [17]. According to IEC
61000-4-30, harmonics and interharmonics should be analyzed
in ten-cycle windows which correspond to a frequency resolu-
tion of 5 Hz. With a constant sampling rate of 3200 Hz, the tenth
DFT sample represents the 50-Hz component. When the system
frequency is 49.5 Hz, for example, a leakage occurs from the
tenth DFT sample toward the ninth DFT sample. This causes
an interharmonic to appear, although it does not exist in the
supply frequency. In this paper, a resampling process through
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
9
Fig. 24. Block diagram of the resampling process to sample ten cycles at
640 equally spaced points.
interpolation is therefore achieved at every ten-cycle to prevent
the leakage.
The algorithm is summarized in Fig. 24. Power cycles are
detected using a low-pass filter with a cutoff frequency at
75 Hz followed by a zero-crossing detection block. By using
the zero-crossing points, data are split into ten-cycle blocks
with rectangular windows. The ten-cycle blocks are resampled
through cubic-spline interpolation such that each ten-cycle data
blocks are sampled with a frequency of 64 samples/cycle.
Each 640-sample block is the input to the DFT block, which
outputs a 640-sample DFT output. In this case, the frequency
resolution of the DFT samples changes from the rate of 5 Hz
to 64 × fs /640 = fs /10, where fs is the supply frequency.
The 10th DFT sample again corresponds to the first harmonic
frequency, which is fs , and 20th DFT sample corresponds to
the second harmonic. No leakage occurs from the harmonic
frequencies to the neighborhood interharmonic frequencies in
this case. This approach is used to obtain the harmonic and
interharmonic analyses of the voltage and current waveforms
presented in Section VIII.
VII. F LICKER –I NTERHARMONIC R ELATIONSHIP
The relationship between flicker and interharmonics has been
investigated previously, and it has been shown that flicker and
interharmonics are the causes of each other [14]–[16]. Light
flicker occurs when the voltage amplitude fluctuates in time.
Therefore, flicker can be modeled as an amplitude-modulated
(AM) signal whose carrier frequency is the 50-Hz supply
frequency as given in IEC 61000-4-15 [18]
y(t) = (A + m(t)) c(t)
= (A + M cos(wm t + φ)) sin(wc t)
(5)
where m(t) is the message signal, M is the amplitude of flicker,
wm is the flicker frequency, wc is the power system frequency,
and A is its amplitude. y(t) can also be expressed as
y(t) = A sin(wc t) +
M
[sin ((wc + wm )t + ϕ)
2
+ sin ((wc − wm )t + φ)] . (6)
The fluctuation of the voltage amplitude shown in (5) causes
the interharmonic frequencies (wc + wm ) and (wc − wm ) to
Fig. 25. Time waveform of (9) with A = 1, M = 0.1, and the same 50-Hz
signal with 45- and 55-Hz interharmonics.
appear in the frequency spectrum of v(t) as shown in (6).
In the case of any harmonics existing in the power system,
interharmonics also appear around the harmonics as shown in
the example for a second harmonic in (7) and (8). For the sake
of simplicity, it is assumed that the fundamental and the second
harmonic are in phase in (7) and (8).
y(t) = (A+M cos(wm t+φ)) [sin(wc t)+M2 sin(2wc t)]
(7)
where AM2 product is the amplitude of the second harmonic
component. y(t) can also be expressed as
y(t)
= A sin(wc t)
M
[sin ((wc +wm )t+ϕ)+sin ((wc −wm )t+φ)]
2
M M2
+AM2 sin(2wc t)
2
× [sin ((2wc +wm )t+ϕ)+sin ((2wc −wm )t+φ)] . . . .
+
(8)
This shows that any voltage fluctuation, which can be approximated as an AM, creates interharmonics around the fundamental and around the harmonics, if they exist. The reverse
is also true, i.e., if there are interharmonics close to the fundamental or the harmonics, they result in fluctuations in the signal
amplitude.
In the case of any interharmonics occurring on only one
side of the fundamental or the harmonics, signal amplitude
fluctuation also occurs. A single interharmonic at 55 Hz given
can be represented as an AM signal plus a low-amplitude
additive signal at 45 Hz, as explained in the following equation:
y(t) = A sin(2π50t) + M sin(2π55t)
= (A + M cos(2π5t)) sin(2π50t) − M sin(2π55t). (9)
Time waveforms of the 50-Hz signal with amplitude 1 with
additive 10% 55-Hz interharmonic and with additive 45-Hz
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 26. Sensitivity curve of the eye–brain set as a function of the frequency
of flicker.
interharmonic are shown in Fig. 25 up and down, respectively.
Both interharmonics create similar voltage amplitude fluctuations. According to IEC 61000-4-15, human eye is the most
sensitive to the voltage fluctuations around 8.8 Hz. The sensitivity is reduced as the flicker frequency deviates up and down
from 8.8 Hz, as shown in Fig. 26 [19]. Hence, interharmonics
approximately 10 Hz apart from the fundamental and also from
the harmonics give the highest contribution to the light flicker
problem.
Since experimentation on systems consisting of multi-EAFs
is very expensive and flicker calculations need long-term measurements (one point for Pst needs 10 min and one point
for Plt needs 2 h), a close correlation between current and
voltage interharmonics in the range of 60–90 Hz (subgroup
interharmonic—1), which is the main cause of flicker, will
be very useful. This correlation permits indirect estimation of
voltage flicker from the current interharmonic data collected for
a short time period. From the short-term current interharmonic
data, one can comment on the existence of flicker and also
on the variation of it. As it can be observed from Figs. 19
and 20, interharmonics around the fundamental are the most
dominant ones. Interharmonics around the second and third
harmonics are also significant. Therefore, the variations in
voltage interharmonics between the first and second components (60–90 Hz) against current interharmonics can give us
an idea about the mentioned correlation and, hence, the status
of the flicker. For various EAFs, voltage and current data
are simultaneously collected on the Medium Voltage (MV)
side of the furnace transformer (at MP1 in Fig. 16), and a
sample interharmonic scattered diagram for Plant-5 is shown
in Fig. 27. The bar charts of current interharmonic, voltage
interharmonic, and short-term flicker as a function of time at
Plant-5 are shown in Fig. 28. These plots show that there is a
good correlation between voltage and current interharmonics,
and therefore, the variations in current interharmonic content
can be used as a good indicator in estimating the state of the
flicker.
For proper design of SVC-type flicker compensation systems, the presence of these interharmonics should be taken
into consideration, particularly in the performance evaluation of
existing passive shunt second- and third-order harmonic filters,
as to be discussed in Section VIII.
In the evaluation of flicker contribution of each plant in
multiarc furnace operation, the harmonic and interharmonic
Fig. 27. Voltage interharmonic subgroup-1 versus current interharmonic
subgroup-1 (same data as in Fig. 28).
Fig. 28. (a) Current interharmonic subgroup-1 (10-min averages), (b) voltage
interharmonic subgroup-1 (10-min averages), and (c) short-term flicker (10-min
averages) for Plant-5 during the whole measurement period.
spectra will be obtained for each plant separately for a time
duration of 10 min (for short-term flicker computation Pst )
when all other plants are off.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
11
Fig. 29. Common harmonic filter topologies for SVC-type flicker compensation systems. (a) SVC Type-1. (b) SVC Type-2. (c) SVC Type-3.
VIII. A SSESSMENT OF THE P ERFORMANCE OF SVC-T YPE
F LICKER C OMPENSATION S YSTEMS
Practices of multinational SVC manufacturers can be summarized in three basic topologies shown in Fig. 29(a)–(c).
The basic difference between SVCs in Fig. 29(a) and (b)
is in the type of second harmonic filter. However, the SVC
in Fig. 29(c) does not include any second harmonic filter.
These three common practices of SVC-type flicker compensation systems will be investigated in this section in terms of
reactive power performance, harmonic filtering performance,
and flicker compensation performance by using synchronous
data collected in Plants 2, 3, and 5 according to the scenarios
described in Section IV.
A. Reactive Power Compensation Performance
It has been observed that SVC-type flicker compensation
systems perfectly compensate rapidly changing reactive power
demand of EAFs. The mean power factor (PF) of an EAF can
be kept at nearly unity by a well-designed SVC.
B. Harmonic Filtering Performance
First, frequency characteristics of passive shunt harmonic
filters in Fig. 29 are obtained by using parameters given in
design documents of SVC manufacturers for Plants 2, 3, and 5.
For this purpose, 1-A harmonic frequency is injected from the
Fig. 30. (a) Common-practice Type-1 model. (b) Frequency response of the
SVC. (c) Field data frequency spectra of the EAF and supply currents of ten
cycles from boring phase of EAF.
EAF side, and the corresponding harmonic current component
reflected to the supply side is computed [see Figs. 30(a), 36(a),
and 43(a)]. The current harmonic injected by EAF varies from
50 to 400 Hz in 63 × 10−4 steps. The resulting frequency
characteristics, as an example, the one in Fig. 30(b), should be
interpreted in the following manner.
1) For harmonic frequencies fn , the magnitude greater than
1 A in the supply side means an amplification, and less
than 1 A means attenuation. These filter characteristics
may be subjected to minor changes in time because of
drift in capacitance values owing to aging.
2) For each SVC type, sample harmonic contents of line
currents on both EAF side (MP2) and supply side (MP1)
are calculated for ten-cycle window from synchronously
collected data. The black-colored harmonic and interharmonic bars (5-Hz resolution) show the EAF side, and the
gray (or red) colored bars show the supply side. Therefore, for any harmonic frequency, if the gray-colored
bar is greater than the black-colored bar, the associated
harmonic is said to be amplified by SVC.
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 31. Second harmonic single-line component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
3) The raw data are calculated for a short period as defined
in Section IV when the other EAFs are off. Since the most
problematic harmonic is the second harmonic component
for all SVC types, single-line harmonic, harmonic subgroup, and harmonic group computations for the second
harmonic component are given in three different forms. In
the first group of plots, their variations are given against
time in the form of 1-s average data. Here, again, the
black-colored curves correspond to the EAF-side current
(MP2), and the gray-colored curves correspond to the
supply-side current (MP1). In the second group of characteristics, scattered diagrams for single line, harmonic
subgroup, and harmonic group for the second harmonic
component are given. Each point in a scattered diagram
corresponds to a ten-cycle window. For the harmonic
component higher than second (i.e., third, fourth, and
fifth), the filtering performances of SVCs are illustrated
by the curves in which the variations in each harmonic
subgroup are given against time. Here, again, the blackcolored curves stand for EAF side, and the gray (or red)
colored curves for supply side.
Below are the detailed analyses on the different SVC types
given in Fig. 29.
1) SVC Type-1: As it can be observed from Fig. 30(b), SVC
Type-1 amplifies all harmonics and interharmonics in the range
from 50 to 120 Hz. These expectations are confirmed from the
experimental data in Fig. 30(c) and Figs. 31–35. In scattered
diagrams, the diagonal of the graph, marked by a dashed line,
shows the case in which EAF harmonic is neither amplified
nor attenuated. Scattered points appearing densely above the
Fig. 32. Second harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 33. Second harmonic group component EAF (IEAF ) versus supply (IS )
currents, when other plants are off and SVC of the plant is on.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
13
Fig. 34. Third harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 36. (a) Common-practice Type-2 model. (b) Frequency response of the
SVC. (c) Field data frequency spectra of the EAF and supply currents of ten
cycles from boring phase of EAF.
Fig. 35. Fourth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
diagonal mean that filtering performance of the harmonic under
investigation is ineffective; that is, it amplifies EAF harmonics
to an extent observed from the associated scattered diagram. As
it can be seen from Figs. 34 and 35, SVC Type-1 filters out the
third and fourth harmonics, particularly the third one.
2) SVC Type-2: As it can be observed from Fig. 36(b),
the ranges of 50–95 Hz, 105–125 Hz, and 160–175 Hz, all
interharmonics are amplified by the SVC. This is verified by the
field data shown in Fig. 36(c) and Figs. 37–39. It is observed
that the single-line harmonic points at 100 Hz are scattered
equally around the diagonal, which shows that this component
is usually not amplified. On the other hand, the subgroup and
group harmonic computations show that a 100-Hz component
is amplified. This is due to the fact that, in subgroup and
group computations, interharmonics around 100 Hz are also
considered. As it can be seen from Figs. 40–42, SVC Type-2
filters out the third, fourth, and fifth harmonic components,
successfully.
3) SVC Type-3: As it can be observed from Fig. 43(b),
SVC Type-3 amplifies all harmonics and interharmonics in
the range of 50–130 Hz. A drastic amplification of second
harmonic occurs. This is the undesirable effect of the secondorder undamped third harmonic filter. This fact is verified by
14
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 37. Second harmonic single-line component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 38. Second harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 39. Second harmonic group component EAF (IEAF ) versus supply (IS )
currents, when other plants are off and SVC of the plant is on.
Fig. 40. Third harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Fig. 41. Fourth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
the experimental data shown in Figs. 44–46 for all harmonic
computation types (single line, harmonic subgroup, and harmonic group). Third, fourth, and fifth harmonic components are
filtered out as it can be seen in Figs. 47–49, respectively.
Table III summarizes the harmonic filtering performance
of SVC-type flicker compensation systems according to the
data collected in the field. The existing common practice for
SVCs cannot filter out the second harmonic subgroup, but
amplifies it. However, harmonic subgroup higher than second
can be filtered out successfully by a properly designed SVC.
One should never forget the effects of Thyristor Controlled
Reactor (TCR) on the aforementioned harmonic curves. An
SVC operating in the steady state (at constant firing angle α)
creates only odd harmonics, excluding third and its powers,
and the magnitudes of these harmonics are normally very low.
However, in the transient states, i.e., in boring and melting
periods, significant low harmonic components will also arise
because of asymmetrical consecutive half current cycles and
also unbalanced third harmonic components. In summary, TCR
harmonics are not necessarily in phase with EAF harmonics.
When they are superimposed, a higher or a lower harmonic
content than those of EAF may be obtained at all harmonic
and interharmonic frequencies. In the previous harmonic characteristics and waveforms, TCR harmonics were not taken into
account. Experimental points scattered more than the expected
one may be attributed to the TCR harmonics. During the field
tests, it was not possible to disconnect only the TCR part of
SVC from the network.
15
Fig. 42. Fifth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
C. Flicker Compensation Performance
In Section VII, it has been shown that current and voltage
interharmonics are correlated, i.e., if there are current interharmonics, then there are voltage interharmonics, and this leads
to light flicker. Since all three common practices of SVC-type
flicker compensation systems amplify the frequencies around
second harmonics as shown in Figs. 30(b), 36(b), and 43(b), a
flicker problem exists in all busbars supplying arc furnaces. The
amplification of interharmonics by the SVC system is shown in
Figs. 50 and 51. In this particular experiment, the SVC system
of Plant-2 is turned off, while the other plants are off. Ten-cycle
first interharmonics of both voltage and current (at MP1) are
computed for this interval to observe the effect of the SVC on
the interharmonics and, hence, the light flicker. Although the
SVC-type flicker compensation system is originally designed
to reduce the flicker level, due to the improper design of the
harmonic filters, (particularly the second harmonic filter), the
SVC systems amplify the interharmonics around the second
harmonic, which causes the light flicker effect. This phenomenon has been observed for all three common practices. It is
obvious that a novel design approach is required for filtering
the second harmonic components.
IX. PQ I NTERACTION B ETWEEN EAFs
IN M ULTIFURNACE O PERATIONS
In order not to face a significant PQ problem, during the
operation of EAF and multi-EAFs, among the site selection
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 44. Second harmonic single-line component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
Fig. 43. (a) Common-practice Type-3 model. (b) Frequency response of the
SVC. (c) Field data frequency spectra of the EAF and supply currents of ten
cycles from boring phase of EAF.
criteria in the planning and design phase of EAF installation(s),
one of the most important criteria is the suitability and adequacy
of the grid to which the EAF(s) is going to be connected. The
well-known criteria in the selection of connection point to the
grid are as follows.
A. SCVD Method
Short-circuit voltage depression (SCVD) is usually expressed as the percentage voltage drop at PCC when EAF
goes from open circuit to short circuit on all three phases.
In order not to present a flicker problem, SCVD should be
≤ 2% at voltages ≤ 132 kV and ≤ 1.6% at higher voltages
(> 132 kV) [20]. SVCD value is directly proportional to the
sum of source impedance, impedances of power transformer
and EAF transformer, feeder impedance, reactance of series
reactor if present, and EAF secondary circuit impedance.
In the planning phase, the most important contribution to the
reduction of SCVD value is to connect EAF to one of the
strongest points of utility grid at the highest possible voltage
level.
Fig. 45. Second harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Fig. 46. Second harmonic group component EAF (IEAF ) versus supply (IS )
currents, when other plants are off and SVC of the plant is on.
17
Fig. 48. Fourth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
B. SCM V Amin /M V AEAF Ratio
Fig. 47. Third harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
In the literature, it is recommended by some researchers that
the ratio of SCM V Amin (minimum value of Short Circuit
Mega Volt-Ampere) to the total arc furnace Mega Volt-Ampere
(MVA) rating should not be lower than 80, while some others
suggest that it should not be lower than 50, in order not to cause
flicker, or to make the flicker problem solvable economically
[12], [13]. For the multifurnace system shown in Fig. 15, these
calculations have been made, and SCVD values are roughly
estimated to be as follows:
1) 1.74% SCVD if only the largest EAF is short circuited;
2) 3.4% SCVD if two EAFs are simultaneously short
circuited;
3) 6.6% SCVD if three EAFs are simultaneously short
circuited;
4) 8.4% SCVD if all EAFs are simultaneously short
circuited.
It is shown that the recommended SCVD values will be
exceeded in the case when more than one EAF are supplied
from the same point.
SCM V Amin /M V AEAF ratio is found to be 70 even for the
smallest EAF. When all EAFs are considered, this ratio drops
to a dramatic value of 8. It is seen that a wrong planning has
obviously been made for iron and steel plants’ site containing
multifurnaces. On this occasion, it is not possible to solve the
flicker problem at PCC even to reduce it by the use of SVCtype flicker compensation systems because of the interactions
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Fig. 50. Interharmonic subgroup-1 of the voltage waveform from melting
phase of Plant-2 (ten-cycle averages with five-cycle overlaps).
Fig. 51. Interharmonic subgroup-1 of the current waveform from melting
phase of Plant-2 (ten-cycle averages with five-cycle overlaps).
Fig. 49. Fifth harmonic subgroup component EAF (IEAF ) versus supply
(IS ) currents, when other plants are off and SVC of the plant is on.
TABLE III
H ARMONIC F ILTERING P ERFORMANCES OF T HREE C OMMON P RACTICES
(F: F ILTERED , A: A MPLIFIED )
between EAFs and amplifications of interharmonics by existing
second harmonic or third filter as discussed in Section VIII.
The experimental results obtained from these plants prove
these propositions indeed. Sample short-term (Pst ) and longterm (Plt ) flicker values collected for seven-day time periods
for multifurnace operation are shown in Fig. 52.
Obviously, Pst and Plt values are much higher than the limit
values given in the associated standards [9]. It is worth noting
that the SVC-type flicker compensation systems designed by
multinational companies have been in operation during the
measurement period. Despite these facts, these EAFs are operating and producing millions of tones of steel every year. This
problem cannot be solved with current technology, but it can be
made less serious by reorganizing the structure of EAF power
Fig. 52. Seven-day flicker variation at PCC supplying multi-EAFs: (a) Pst
and (b) Plt .
system in this region. That is, nine EAFs in five iron and steel
plants can be subdivided in the three groups for connection to
three different points of the utility grid. Furthermore, transmission voltage level at PCCs should be upgraded from 154 to
400 kV. One further countermeasure is needed in reducing
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
flicker. That is, a new power plant installation with 1000-MW
installed capacity seems to be inevitable in addition to the
existing two thermal plants and one natural gas plant located
around this region.
X. C ONCLUSION
The following conclusions can be drawn from the results of
intensive experimental work carried out in the field on both
single-furnace and multifurnace plants.
1) In order to avoid flicker, the most critical step is the
planning stage of EAF installations. For the candidate
connection point of EAF(s) to utility grid, first, simple
calculations of SCVD and SCM V Amin /M V AEAF ratio
are to be carried out. These values should be safely lower
than the recommended values, because after installation
of SVC-type flicker compensation systems, flicker will
normally be increased.
2) An SVC-type flicker compensation system can compensate satisfactorily the rapidly changing reactive power
demand of EAFs and keep the PF nearly at unity.
3) Passive shunt filters of carefully designed SVCs can
successfully filter out harmonic current components produced by EAFs except second harmonic. The widely
applied passive shunt filter topologies are experimentally
proven to lead to amplification of second harmonic subgroup and groups even to the amplification of single-line
second harmonic component for many cases. In SVCtype flicker compensation systems, second harmonic filter
seems to be integrated into the system not for the purpose
of attenuation of the second harmonic component but
to limit its magnitude owing to the third harmonic filter
magnification.
4) In EAF installations, the major cause of the light flicker is
interharmonics around the existing harmonics. Therefore,
interharmonics primarily between fundamental and second harmonic components, secondarily between second
and third harmonic components, are the causes of flicker.
Since interharmonics between fundamental and second
harmonic components are significantly amplified by all
widely used passive filters, the operation of the SVCtype flicker compensation system is shown to increase the
flicker level at PCC. Therefore, one can conclude that the
known SVC-type flicker compensation systems cannot be
a solution to an existing flicker problem of single and
multi-EAF installations.
5) Because of the interaction between several SVCs and
EAFs during multifurnace operation light flicker, interharmonics and second harmonic subgroup are more
complex and usually more drastic in comparison with
single EAF operation. The best approach to solve these
problems is to avoid or minimize these risks in the
planning phase by selecting the most proper connection
point in the utility grid for EAF installation. To solve
flicker, interharmonics, and second harmonic problems of
the existing EAF installations, new active devices such
as active-power-filter D-STATCOM systems should be
exercised.
19
ACKNOWLEDGMENT
The authors would like to thank the arc furnace plant authorities in the Izmir/Aliağa region of Turkey for supplying
the opportunity of field measurements and their collaborative
work of making the PCC measurements during various operating conditions of the plants. This research and technology
development work is carried out as a subproject of the National
Power Quality Project of Turkey.
R EFERENCES
[1] J. G. Mayordomo, E. Prieto, A. Hernandez, and L. F. Beites, “Arc furnace
characterization from an off-line analysis of measurements,” in Proc.
IEEE 9th Int. Conf. Harmonics Quality Power, Orlando, FL, Oct. 2000,
pp. 1073–1078.
[2] P. E. Issouribehere, F. Issouribehere, and G. A. Barbera, “Power quality
and operating characteristics of electric arc furnaces,” in Proc. IEEE
Power Eng. Soc. General Meeting, 2005, pp. 784–791.
[3] P. E. Issouribehere, J. C. Barbero, G. A. Barbera, and F. Issouribehere,
“Compatibility between disturbance emission and Argentinian power
quality regulations in iron and steel industries,” in Proc. IEEE/PES, TDC
(Latin America), pp. 1–6.
[4] B. Boulet, J. Wikston, and L. Kadar, “The effect of measuring system
accuracy on power quality measurements in electric arc furnaces,” in
Conf. Rec. IEEE IAS Annu. Meeting, 1997, pp. 2151–2155.
[5] A. Hernandez, J. G. Mayordomo, R. Asensi, and L. F. Beites, “A
method based on interharmonics for flicker propagation applied to arc
furnaces,” IEEE Trans. Power Del., vol. 20, no. 3, pp. 2334–2342,
Jul. 2005.
[6] Testing and Measurement Techniques-Power Quality Measurement
Methods, IEC 61000-4-30, 2003.
[7] E. Özdemirci, Y. Akkaya, B. Boyrazoglu, S. Buhan, A. Terciyanli,
O. Unsar, E. Altintas, B. Haliloglu, A. Acik, T. Atalik, Ö. Salor,
T. Demirci, I. Cadirci, and M. Ermis, “Mobile monitoring system to take
PQ snapshots of Turkish electricity transmission system,” in Proc. IEEE
IMTC, Warsaw, Poland, 2007, pp. 1–6.
[8] T. Demirci, A. Kalaycıoğlu, Ö. Salor, S. Pakhuylu, M. Dagh,
T. Kara, H. S. Aksuyek, C. Topcu, B. Polat, S. Bilgen, S. Umut,
I. Cadirci, and M. Ermis, “National PQ monitoring network for Turkish
electricity transmission system,” in Proc. IEEE IMTC, Warsaw, Poland,
2007, pp. 1–6.
[9] Turkish Electricity Transmission System Supply Reliability and
Quality Regulation, 2004. Last accessed on December 12, 2009. [Online].
Available: http://www.teias.gov.tr/yonetmelikler/supply.doc
[10] IEEE Recommended Practices and Requirements for Harmonic Control
in Electrical Power Systems, IEEE Std. 519-1992, 1992.
[11] Testing and Measurement Techniques—General Guide on Harmonics
and Interharmonics Measurements and Instrumentation, for Power
Supply Systems and Equipment Connected Thereto, IEC 61000-4-7,
2002.
[12] B. Bharat, “Arc furnace flicker measurement and control,” IEEE Trans.
Power Del., vol. 8, no. 1, pp. 400–410, Jan. 1993.
[13] S. R. Mendis, M. T. Bishop, and J. F. Witte, “Investigations of voltage
flicker in electric arc furnace power systems,” IEEE Ind. Appl. Mag.,
vol. 2, no. 1, pp. 28–38, Jan./Feb. 1996.
[14] T. Keppler, N. R. Watson, J. Arrillaga, and S. Chen, “Theoretical assessment of light flicker caused by sub- and interharmonic frequencies,” IEEE
Trans. Power Del., vol. 18, no. 1, pp. 329–333, Jan. 2003.
[15] T. Tayjasanant, W. Wang, and C. Li, “Interharmonic-flicker curves,” IEEE
Trans. Power Del., vol. 20, no. 2, pp. 1017–1024, Apr. 2005.
[16] J. A. Pomilio and S. M. Deckman, “Flicker produced by harmonics
modulation,” IEEE Trans. Power Del., vol. 18, no. 2, p. 67,
Apr. 2003.
[17] A. Testa, D. Gallo, and R. Langella, “On the processing of harmonics and
interharmonics: Using Hanning window in standard framework,” IEEE
Trans. Power Del., vol. 19, no. 1, pp. 28–34, Jan. 2004.
[18] Testing and Measurement Techniques-Flickermeter- Functional and
Design Specifications, IEC 61000-4-15, 1998.
[19] G. Diez, L. I. Eguiluz, M. Manana, J. C. Lavandero, and A. Ortiz,
“Instrumentation and methodology for revision of European flicker
threshold,” in Proc. 10th Int. Conf. Harmonics Quality Power, 2002,
pp. 262–265.
[20] T. J. E. Miller, Reactive Power Control in Electric Systems. NewYork:
Wiley-Interscience, 1982.
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 1, JANUARY/FEBRUARY 2010
Özgül Salor (S’98–M’05) received the B.Sc., M.Sc.,
and Ph.D. degrees in electrical engineering from the
Middle East Technical University, Ankara, Turkey, in
1997, 1999, and 2005, respectively.
From 2001 to 2003, she was a Professional Researcher at the University of Colorado, Boulder.
Since 2006, she has been with the Power Electronics
Department, TÜBİTAK UZAY Research Institute,
The Scientific and Technological Research Council
of Turkey (TÜBİTAK), Ankara, where she is currently a Chief Senior Researcher. She is also a parttime Lecturer in the Department of Electrical and Electronics Engineering,
Gazi University, Ankara. Her research interests are speech-signal processing
and signal processing for power quality.
Burhan Gültekin (S’03) received the B.Sc. and
M.Sc. degrees in electrical and electronics engineering from the Middle East Technical University,
Ankara, Turkey, in 2000 and 2003, respectively,
where he is currently working toward the Ph.D.
degree.
He is currently a Chief Senior Researcher in the
Power Electronics Department, TÜBİTAK UZAY
Research Institute, The Scientific and Technological
Research Council of Turkey (TÜBİTAK), Ankara.
His areas of research are in reactive power compensation systems and power quality issues.
Tevhid Atalık received the B.Sc. degree in electrical
and electronics engineering from Uludað University,
Bursa, Turkey, in 2000, and the M.Sc. degree in electrical and electronics engineering from Hacettepe
University, Ankara, Turkey, in 2003. He is currently
working toward the Ph.D. degree at Başkent University, Ankara.
He is currently a Senior Researcher in the Power
Electronics Department, TÜBİTAK UZAY Research
Institute, The Scientific and Technological Research
Council of Turkey (TÜBİTAK), Ankara. His areas of
research include power quality analysis and hardware design.
Adnan Açık received the B.Sc. and M.Sc. degrees
in electrical and electronics engineering from the
Middle East Technical University, Ankara, Turkey,
in 1995 and 1998, respectively.
He is currently a Chief Senior Researcher in the
Power Electronics Department, TÜBİTAK UZAY
Research Institute, The Scientific and Technological
Research Council of Turkey (TÜBİTAK), Ankara.
His main areas of research are in power quality and
switch-mode power supplies.
Serkan Buhan received the B.Sc. degree in electrical and electronics engineering from Hacettepe
University, Ankara, Turkey, in 2005, where he is
currently working toward the M.Sc. degree in power
quality.
He is currently a Researcher in the Power Electronics Department, TÜBİTAK UZAY Research Institute, The Scientific and Technological Research
Council of Turkey (TÜBİTAK), Ankara. His areas
of research include power quality analysis using
wavelets.
Alper Terciyanlı (S’03) received the B.Sc. and
M.Sc. degrees in electrical and electronics engineering from the Middle East Technical University,
Ankara, Turkey, in 2001 and 2003, respectively,
where he is currently working toward the Ph.D.
degree in medium-voltage ac motor drives.
He is currently a Chief Senior Researcher in the
Power Electronics Department, TÜBİTAK UZAY
Research Institute, The Scientific and Technological
Research Council of Turkey (TÜBİTAK), Ankara.
His areas of research include reactive power compensation systems and power quality issues.
Burak Boyrazoğlu received the B.Sc. degree in
electrical and electronics engineering from the
Middle East Technical University, Ankara, Turkey,
in 2005.
From 2006 to 2008, he was a Researcher in the
Power Electronics Department, TÜBİTAK UZAY
Research Institute, The Scientific and Technological
Research Council of Turkey (TÜBİTAK), Ankara.
Currently, he is with Renaissance Constructions,
Moscow, Russia.
Özgür Ünsar (S’07) received the B.Sc. degree
in electrical and electronics engineering from the
Middle East Technical University, Ankara, Turkey,
in 2006. He is currently working toward the M.Sc.
degree at Hacettepe University, Ankara.
He is currently a Researcher with the Turkish
Electricity Transmission Corporation (TEIAŞ),
Ankara. His current areas of research include power
quality measurement and analysis.
Tolga İnan received the B.Sc. and M.Sc. degrees
in electrical and electronics engineering from the
Middle East Technical University, Ankara, Turkey,
in 2000 and 2003, respectively, where he is currently working toward the Ph.D. degree in 3-D face
recognition.
He is currently a Senior Researcher in the Power
Electronics Department, TÜBİTAK UZAY Research
Institute, The Scientific and Technological Research
Council of Turkey (TÜBİTAK), Ankara. His areas
of research include pattern recognition, computer
vision, machine learning, and power quality analysis.
Erinç Altıntaş received the B.Sc. degree in electrical and electronics engineering from the Middle
East Technical University, Ankara, Turkey, in 2006,
where he is currently working toward the M.Sc.
degree.
He is currently a Researcher with the Turkish
Electricity Transmission Corporation (TEIAŞ),
Ankara. His current areas of research include power
quality measurement and analysis.
SALOR et al.: ELECTRICAL POWER QUALITY OF IRON AND STEEL INDUSTRY IN TURKEY
Yener Akkaya received the B.Sc. degree in electrical
and electronics engineering from Istanbul Technical University, Istanbul, Turkey, in 1989, and completed the Public Administration Master Program at
TODAIE, Ankara, Turkey, in 1997.
Since 1989, he has been with the Turkish Electricity Transmission Corporation (TEIAŞ), Ankara,
where he was with the Administration and Maintenance Department and has been the Director of the
Research and Development Department since 2003.
His current research interests are power quality and
transmission system planning.
Ercüment Özdemirci received the B.Sc. and M.Sc.
degrees in electrical and electronics engineering
from Fýrat University, Elazýð, Turkey, in 1998 and
2001, respectively.
From 1998 to 2003, he was with the Department
of Load Dispatch, Turkish Electricity Transmission
Corporation (TEIAŞ), Ankara, Turkey, where he is
currently in the Department of Transmission Planning. His current research interests are power quality, load-frequency control, and transmission system
planning.
21
Işık Çadırcı (M’98) received the B.Sc., M.Sc.,
and Ph.D. degrees in electrical and electronics
engineering from the Middle East Technical
University, Ankara, Turkey, in 1987, 1988, and 1994,
respectively.
She is currently a Professor of electrical engineering at Hacettepe University, Ankara, and also
the Head of the Power Electronics Department,
TÜBİTAK UZAY Research Institute, The Scientific and Technological Research Council of Turkey
(TÜBİTAK), Ankara. Her areas of interest include
electric motor drives, switch-mode power supplies, and power quality.
Dr. Çadırcı received the 2000 Committee Prize Paper Award from the Power
Systems Engineering Committee of the IEEE Industry Applications Society and
also the IEEE Industry Applications Magazine Prize Paper Award, Third Prize,
in 2007.
Muammer Ermiş (M’99) received the B.Sc., M.Sc.,
and Ph.D. degrees in electrical engineering from the
Middle East Technical University (METU), Ankara,
Turkey, in 1972, 1976, and 1982, respectively, and
the M.BA. degree in production management from
Ankara Academy of Commercial and Economic Sciences, Ankara, in 1974.
He is currently a Professor of electrical engineering at METU. He is also currently the Manager of
the National Power Quality Project of Turkey. His
current research interest is electric power quality.
Dr. Ermiş received the “The Overseas Premium” paper award from the
Institution of Electrical Engineers, U.K., in 1992, and the 2000 Committee
Prize Paper Award from the Power Systems Engineering Committee of the
IEEE Industry Applications Society. He was the recipient of the 2003 IEEE
PES Chapter Outstanding Engineer Award.