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National Power & Energy Conference (PECon) 2004 Proceedings, Kuala Lumpur, Malaysia
‘25
Windows Based Graphical Tool For Symmetrical
Components Analysis
Zainuddin Mat Isa and Marizan Sulaiman
ALsirucr-A new windows based graphical tool to
facilitate the teaching and learning the symmetrical
components analysis is described in this paper. This
software provides a user-friendly environment to aid the
studies of symmetrical components. The software
calculates and disptays graphically the ABC sequence and
the corresponding phasors of symmetrical components.
Taking the advantages o f the Graphical User Interface
(CUI), it provides the student with Interactive visual
communication to analyze and better understand the
relationship between the ABC sequence and symmetrical
components. Students can manipdate the graphical
displays either using keyboard input or mouse operation.
Besides, students can use this tool to analyze the
unsymmetrical short circuit fault currents. It is hoped that
this tool will make the learning process mote interactive,
interesting and user’friendly.
’
Keywords: Graphical User Interface (GUI), Teaching
and Learning, Symmetrical Components, Fault Analysis,
Phasor Representation.
I,
INTRODUCTION
A Graphical User Interface (CUI) would better
enable the students to visualize the effect of parameter
changes on the power system being studied. The GUI
environment keeps most of the tedious and repetitive
calculations in the background, allowing the students to
spend more time to analyze the results obtained.
Therefore, many power system analysis software have
been developed [ 1:2] by taking the advantages o f GUI.
The objective o f this- project is to develop an
educational tool for the analysis of symmetrical
components. This software provides an interactive and
user-friendly environment. In this package, the phasors
can be graphically manipulated either using a mouse or
manually edited by entering numerical values through
the keyboard, Using this software, sfudents will be able
the leaming process in the classroom, as well as in the
students’ self-study.
11. SYMMETRICAL COMPONENTS
A set of unbalanced phasors can be represented by
three sets of batanced phasor components called
positive-sequence, negative-sequence,
and zerosequence. The two of the com onent sets (positive and
negative) are displaced by 120 and the other set (zero)
!
is in phase (according to Fortescue’s theorem) [1-51,
Figure f illustrates the t h e e sets of balanced phasors.
IdeaIly, the positive-sequence set is the onIy one
present during balanced operation. The presence of
negative-sequence and zero-sequence components
indicates unbalanced operation of the power system
during faults. All three-phase quantities in a power
system can be represented by the sum of the
symmetricai components. For example, the phase
volteges can be expressed in terms o f their symmetrical
components, as given by Equations (I), (2), and (3).
v, = Val3 + v,, + v,,
(1)
vb=vbO+vbl+ V b 2
=
-k Vcl
(2)
(3)
v, v, + v,,
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Using the “a” operator (a = 1L120°), the phase
quantities can be express in terms of the A-phase
components, given in-ihe matrix form in Equations (4).
to see the relationship between phase sequences and
sequence components and the different between line-toneural and line-to-line types of phasors. This interactive
and compreliensive software. supplements and enhances
Zainuddin Mat Isa i s with Faculty of Electrical Engineering, Kolej
Universiti
Teknikal
Kebangsaan
Malaysia
(email:
zainuddin~kulktii.cdu.mv).
Marizan Sulaiman is Profesor with Faculty of Electrical
Engineering,Kolej Universiti Teknikal Kebangsaan Malaysia (email:
mariznn~kutkm.edu.n~v~.
0-7803-8724-4/04/$20.00 02004 IEEE,
Fig. I . Positive-Sequence, Negative-Sequence, and ZcroSequence Components
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Solving for the inverse of the matrix in Equations (4),
the sequences voltages can be expressed as follows:
113 (V, + V, +VJ
(5)
Val= 1/3(V, + a Vb + a2 V,)
(6)
vn= 113 (v, + a‘ vb+ a v,)
(7)
V,
=
r
or in matrix form:
111. DESCRIPTION OF THE SOFTWARE
These equations show how to resolve the three
unsymmetrical phasor into their symmetrical
components. The proceeding equations could have been
written for any set of related phasor such a5 for currents
instead of for voltages. Phase and sequence currents in
the matrix form can be expressed as:
Tlus software is written in Microsoft Visual Basic
6.0 (VB6) language and standard Windows functions
and features are included, Figure 2 shows some of the
GUI features in this software package. This software
contains four main menus, “File”, “Edit”, “View”, and
“Help”. Under the pull-down “File” menu, students can
choose to open, print or save the current interface that
contains both image and numerical data of the phasors
such as shown in Figure 2. The students are able to
save the current data as a graphic file either in BMP,
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fig. 2. Main GUI for symmetrical components analysis software
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JPG or .CIF format or keep it as a data file (DAT) for
future reference. In addition, the particular interface or
data can be copied into other programs such as
Microsoft Words and Paint using standard cut,*copy
and paste functions under the “Edit” menu. This will
help students to document the exercises done.
Under the “View” menu, students can select lineto-neutral, line-to-line, or phasor addition of the
symmetrical component options. Under these three
options, students can also select the subs-menu ‘V’ or
‘I’ to view the relationship between voltages or currents
for the corresponding symmetrical components. AH
these options allow them to graphicalIy examine the
characteristics of the symmetrical components in the
line-to-neutral or the respective line-to-line format for
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Fig. 4. The effect o f varying the value o f negative-sequence componcnt
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Figure 2, there are four picture boxes for displaying the
phasors. The box on the left shows the phasors for ABC
sequence while three smaller boxes on the right side
display the corresponding positive-, negative-, and
zero- sequence phasors. Even though, the sizes of these
picture boxes are fixed, the lengths of the phasor
images are rescaled automatically when users enter new
data. The values of magnitude and angle for the ABC
sequence phasors or symmetrical components can be
modified either using keyboard or mouse. After
entering the input data using keyboard, user must press
the corresponding “OK” button to update the phasor
images for both the ABC sequence and symmetrical
components. Changing the data using a mouse is
straight forward. By clicking the mouse button over an
arrow of particular phasor, the phasor can be moved as
desired. As the phasor is being dragged, the images and
Fig. 3. Changing magnitudes and angles of the ABC sequence
both voltages and currents in y e connection. It also
helps them in understanding the relationship between
the ABC sequence and symmetrical components.
Furthermore, selecting fault analysis options provide
the students with the capability to observe the effect of
various types of faults and understand their boundaries.
Meanwhile, the options menu changes the setting such
as power factor. For easy excess, all of these options are
made available as push-button in toalbar as seen in
Figure 2. Besides, students can get the help by pressing
the F1 key or choosing from the “Help”.menu.
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IV. SOFTWARE IMPLEMENTATION
The example shown in Figure 2 is voltage
representation in the line-to-neuiral format. This
example shows a balanced three-phase AJ3C sequence,
with both the negative- and zero- sequence components
have zero inagnitude. For easy identification, each
phasor is labeled and color-coded. With reference to
Fig. 5. The line-to-line voltage phasor representation
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Fig. 6. The line-to-line current phasor representation
the corresponding numerical data of all the affected
phasor will be updated simultaneously.
Figure 3 and Figure 4 shows two different
examples. Comparing Figure 2 and 3, it can be seen that
by changing the phase A and phase B in the ABC
sequence, the corresponding symmetrical component
phasors are updated automatically. This will allows the
users to observe the changes not only on numerical data
but also graphically and interactively through the
phasors images. Figure 4 shows the changing o f ABC
sequence phasors with respect to the changing of
negative sequence phasor.
As mentioned earlier, the students can easily view
the corresponding ABC sequence and symmetrical
component phasors in the line-to-line format by
clicking on Line-to-Line push-button. The sofhKare will
convert the corresponding line-to-neutral values into the
Fig. 7. The line-to-line and line-to-neutral voltages relationship
Fig. 8. View the line-lo-line and he-to-neutral currents
relationship
line-to-line format by assuming that the system is
connected in ye-connection. In this system, the line
currents equal to phase currents and the magnitude of
line voltage is 43 greater than the phase voltage. Figure
5 and Figure 6 show the corresponding line-to-line
voltages and currents for phasor diagram of Figure 3.
Besides, students can observe that no zero-sequence
component exists if the s u m of the three phasors is zero.
Also through this option, the students can relate the
line-to-neutral and line-to-line phasor diagrams together
not only numerically but also graphically.
The third push-button or option is “Phasor” menu,
provided in this tool as phasor comparison and
summation push-button. There are four main sub-menu
in this option labeled “V”, “I”, “VI” and “+”. BY
clicking on “V” or “I” push-button, students are able to
view the corresponding line-to-line and line-to-neutral
Fig.9. The effect of leading p o w factor into phase voltage and
current
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The last option allows the students to view the addition
of symmetrical component phasors in order to build the
corresponding phase sequence. Therefore, this software
provides a user-friendly environment and easy to use
tool to aid students for better visualizing and analyzing
the symmetrical components.
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Fig. 10. The effect of lagging power factor into phase voltage and
current
valGges or currents (depending on the selection) in one
diagram as shown in Figure 7 and Figure 8. This will
probably enhance the students’ understanding the
relationship between these iwo formats. The third pushbutton will show the phase voltages and currents in
same diagram. This push-button is provided to
demonstrate the effect of power factor and it shows
graphically the meaning of leading and lagging power
factor. Figure 9 and Figure 10 show some examples for
this option. ‘Students are able to change the value of
power factor by clicking option push-button. Figure 1 I
shows the Option window, The “+” push-button is a
summation push-button. By clicking on this pushbutton, students are able to view the addition of the
symmetrical component phasors in order to construct
the corresponding ABC sequence as shown in Figure
Fig. 1 I .
The Option window inlerface
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12.
V. CONCLUSIONS
VI. REFERENCES
Yu, Chen, et al, “A Windows Based Graphical Packagc lor
Symmetrical Components Analysis”, lEEE Trnnvnclian on
PowerSyr~ems,Vol. 10, No. 4. Nov. 1994.
Yu,Liu. Wu, et al, “A GUI Based Visualizalion for Sequences
Network”. IEEE Tmnsaclion on Power Syrlemr. Vol. 13, No. I .
Feb. 1998.
Grainger, Stevenson, It., “Power System Analysis”, McGrawHill Book Company, 1994
Saadat, H., “Power System Analysis”. McGraw-Hill Book
Company, 1999
Glover, Sarma, “Power System Analysis and Design”,
BrooksiCote, 2002
VIL ACKNOWLEDGEMENT
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A Windows based GUI software package to
facilitate the learning and teaching symmetrical
components was developed. This software i s written in
Visual Basic 6.0. This software calculates and displays
graphically and interactively the ABC sequence and its
respective sy”etrica1 components. Four push-button
options are provided in ibis sohare to allow students
to study the symmetrical components in the line-toneutral and line-to-line format. Besides, the students
also have the capability to observe the difference
between phase voltage and line voltage in wyeconnection system The “VI” push-button option gives
students’ opportunity to view the different between
leading and lagging power factot in graphical display.
This project is supported by the short-term grant from
Kolej
Universiti Teknikal Kebangsaan
project
account
PJP/2003/FKE (07)
(KUTKM), under
Malaysia
number
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Fig. 12. The phasor addition of symmetrical components