case study power system studies

VIRTUAL LABORATORY INTO JKUAT ELECTRICAL ENGINEERING
SYLLABI: CASE STUDY POWER SYSTEM STUDIES
1*
2
Kibet A.K. , Muriithi C. M. ,
School of Electrical & Electronics, Computer and Information Engineering
2
Department of Electrical & Electronic Engineering,
Jomo Kenyatta University of Agriculture & Technology, Kenya
1
2
[email protected], [email protected]
1
ABSTRACT
Power system panels are some of the most educative systems as far as power system analysis is
concerned. Along the electrical engineering in the developing nations the learners are forced to
imagine some of the colossal facts in the field. This is because of lack of equipments which are
too expensive rendering them lame in practical aspects of the studies. This is contrary to many
other courses where the specimens are easily available and the dangers involved are manageable
such as working with plant specimens. It is therefore a milestone to introduce a unit that will
equip students with the actual world through virtualization of the complicated systems in order to
demystify the internal detailed operation of the system and subsystems. This Study explores the
academic significance behind introduction of virtual laboratories in developing countries with
emphasis on power systems.
INTRODUCTION
Virtual laboratories are the emulation of the actual existence of a system or an equipment using
the available paraphernalia such as models both software and miniature icons. There are many
softwares that have been developed thanks to the technological mile age pertaining to the
computerization of the systems. This has made it possible for large systems to be represented on
a simple computer designed model. This models help in simulation of large networks involving
very high voltage ratings. This gives a platform through which various tests can be conducted
without fear of economic implications in terms of damage of components. Experiments that
would have otherwise been an imagination in the real world can now be performed virtually.
Moreover the new systems can be developed and tested before actual execution of the project
[1].
The advancement in information technology has made it possible for hardware experiments to be
redesigned such that they can be performed using computer simulations. This can be integrated
very well in the distant learning which is increasing rapidly in this global village. Power system
analysis toolbox (PSAT); an open source software, is one of the software that is being used in a
number of institutions at undergraduate and graduate levels [2]
Apart from the well packaged help, software forums have also been established where student’s
problems are attended to remotely and has a number of simulated examples. The Kenyan system
of education is more of theoretical as far as power system studies are concerned. This is mainly
because of lack of facilities that include power system panels which are very expensive and out
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of reach for the students. This forces students to learn through mere imagination and therefore
some of the important attributes of machines cannot be felt [5].
METHODOLOGY
The SimPower System Blockset
Our major area of concern is in power system analysis which involves very large power systems
such as the Kenyan system. Despite the fact that power system laboratories have been done
virtually due to the impossibility of performing experiments in high voltage transmission systems
which demand the use of high voltages and powers in KVA and MVA ratings respectively, this
has not been effected in Kenyan education system. Transient Network Analyzers (TNA) has
always been used in the past however with the introduction of digital computers the studies have
made debut from the TNA to computer based simulations. This has been promoted further by the
invisible nature of electricity which has been made possible through the use of the software. This
phenomenon has made computer based units more efficient in solution seeking particularly for
didactic and research purposes. Through simulation, heavy time domain and state estimations
have been made possible [3]. It has also been possible in the contemporary society to have very
complex systems and perform the various analyses to determine the various parameters and
general behaviour of the system [8]
Despite the fact that most of the software does not provide an ability to change the source code,
it gives room for creating custom models which are often the greatest and crucial parts of
computational efficiency. This catapults the flexibility in the world of academia. The power
system has made a great advancement in the incorporation of software simulation such as the use
of UWPFLOW, PST, PSAT and power WEB. Power System analysis tool box is one of the
widely used in most of the universities across the world.
Other platforms for simulation include; Network Torsion Machine Control (NOTOMAC) which
performs Load flow calculations, Simulation in time domain, Calculations in frequency domain
and optimization and identification; PSCAD/EMTDC which is a powerful graphical interface
that can be used to perform various studies such as contingency studies, relay coordination,
transformer saturation effects, control and optimal design of controller parameters among others
and PCFLO which performs load flow, short circuit, and harmonic analysis.
One of the toolboxes, SimPowerSystem tool box found in Matrix laboratory (MATLAB); one of
the most widely used engineering simulation tools in the computer era. It contains various tool
boxes for diverse application.
Virtual Laboratories
The virtual laboratories proposed in this paper shall be established systems that will enable
students to interact well with the software with the sole purpose of boosting understating of the
real case scenarios which would have just been overviewed theoretically. The basic equipments
required for the establishment of these laboratories are the softwares to be made available in the
various computer laboratories and the various real case setups to be structured in a manner that
can be simulated by the students and thus will catapult the student thinking beyond mere
theoretical precepts [6].
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The main reason for introduction of these laboratories is that they are cheap for instance Matlab
student license costs only $1500, readily available, and accessible and expand under study
horizon. The actual laboratories are expensive for example one control panel costs around
$16000 coupled with running costs such as for the electric energy and the maintenance costs, out
of reach and are too dangerous to carry out some tests. [4]
Power System Studies
The technical or scientific field of the Power Systems Laboratory mainly entails design of
electric and integrated systems which calls for planning, design and operation as well as the
analysis of the systems developed. SimPowerSystem provides such a platform where this can be
practiced. It is a block set that works closely with SimMechanics found within MATLAB and
provide the capability of physical modeling of electrical or mechanical system as well as their
control system. It is from the physical system that various parameters can be performed. Static,
dynamic and hybrid systems can also be fabricated and studied using the same platform through
variation of some of the running configurations. [7]
Electrical power systems is a combination of electrical and mechanical system;
electromechanical which include motors and generators. Need to achieve high efficiency coupled
with non linearity of the power system parameters has necessitated the use of complicated
control mechanisms through the use of sophisticated power electronic devices. Simulation
therefore using SimPowerSystem is such a timely arena where all this can be achieved. This is a
modern design tool which makes it possible for engineers to build systems that represent and
actual case scenario with ease. Simulink is the mother which houses SimPowerSystem toolbox
and uses simple drag and drop mechanisms. The tool box also provide interactions with various
attributes such as mechanical, thermal, control among others that lead to successful operation of
@
a system. The computational engine for all the arithmetic is MATLAB which also acts as a link
through which the various toolboxes can be interlinked to operate as a unit. It is equipped with
several examples of models which provide a stepping stone for first time users with very lucid
demonstration. The debugging tools are also excellent since it gives a clear guidance to the
location of a fault in the connection and suggests a solution. The libraries contain herein have
various standard models of machines whose validity is traced back to power system testing and
simulation laboratories in Quebec coupled with the experience of Ecole de Technologie
supérieure and Université Laval [6]
CASE STUDY
The case studied is a simple system comprising of three buses. The system has two generators
and an RL load supplied at 220KV transmission line. The buses are swing bus (slack bus); PV
bus (generator) and PQ (load bus).
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Figure 1: Line diagram of the three phase system
The main task in this study is to test the behaviour of the generator connected to the PV bus
whenever a fault occurs at a given point in the circuit. The fault has been introduced in one of the
transmission lines and the circuit breakers programmed to respond after 2/60 seconds by
isolating the transmission line and reconnecting back once the fault has been cleared with a time
delay of 2/60 seconds. The parameters that have been checked in the system include the phase
angle, the speed and the power although the numbers of features of the machine that can be
examined are more. The system assembled is as shown in fig. 2.
The software gives a provision of determining discrete as well as continuous output through the
application of the various measuring equipment such as scope and display. A three phase fault is
introduced between the fifth and the seventh second and the circuit breakers were programmed to
isolate the transmission line affected after the sixth and eighth second. The outputs from the
scopes after running the system for ten seconds were then captured into the workspace and the
curves plotted as indicated in the next section.
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Constant2
Vabc
1
A
Terminator
A
Scope1
a
B
A
B
b
b
C
c
b
C
C
a
B
b
C
c
m
C
b
Three-Phase
Transformer
c
1
(Two Windings)
C
B
B
Vf_
C
Three-Phase Breaker1
A
B
C
BUS 1
Pm
Ba
c
Three-Phase
Transformer
(Two Windings)1
BUS 2
Constant1
A
B
C
A
B
C
A
B
C
1
A
B
C
C
ctransmission line 1
A
Synchronous Machine
pu Standard1
A
A
a
a
B
Scope2
Iabc
B
Vf_
SynchronousConstant3Machine 1
pu Standard
Vabc
A
A
B
C
m
Pm
A
Iabc
Constant
Three-Phase
Series RLC Load
transmission line 3
A
B
C
Three-Phase
Series RLC Load1
A
Machines
Measurement
Demux
Fault
B
C
circuit breaker
A
transmission line 2
C
c
b
a
B
wm Rotor speed
Pe Electrical Power
0
Continuous
Display1
0
m
Delta Load Angle
Cc
b
B
Qeo
A
B
C
a
Iabc
A
Vabc
Peo
BUS 3
Display
Scope4
Scope 3
Fourier
Three-Phase
Parallel RL Load
magnitude
signal
angle
Figure 2: Schematic diagram of a three bus power system
RESULTS AND ANALYSIS
The outputs of the rotor speed, electrical power and load angle curves against time as shown in
fig: 3, 4 and five respectively.
Graph of rotor speed against Time
1.0025
1.002
1.0015
Speed( pu)
1.001
1.0005
1
0.9995
0.999
0.9985
0
0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18
Time (Minutes)
Figure 3: Graph of Rotor Angle against Time
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Graph of Electric Power against Time
3
2
Electric power in PU
1
0
-1
-2
-3
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.16
0.18
Time in Minutes
Figure 4: Graph of Electric power Against Time
Graph of Load angle against Time
35
30
25
Load Angle(deg)
20
15
10
5
0
-5
-10
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Time(Minutes)
Figure 5: Graph of Load Angle against Time
BUS 3:Voltage againts Time
2
1.5
1
Voltage in PU
0.5
0
-0.5
-1
-1.5
-20
0.02
0.04
0.06
0.08
0.1
Time in Minutes
0.12
0.14
0.16
0.18
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Figure 6: Graph of Bus voltage Against Time
Bus 3: Graph of Current Against Time
0.8
0.6
0.4
C u rre n t in P U
0.2
0
-0.2
-0.4
-0.6
-0.8
-10
0.02
0.04
0.06
0.08
0.1
Time in Minutes
0.12
0.14
0.16
0.18
Figure 7: Graph of Current against Time
These are just a few of the parameters of the machine generating to the PV bus that were
captured however there are other features that can also be established such as stator currents,
field current, mutual fluxes, stator voltage, mechanical torque among others which would have
been very cumbersome to test in a real machine.
The parameters are on prime significance when determining the various behaviours through
imposing some conditions to the system and therefore help in prior determination of the antidote
to the anticipated anomaly.
The behavior of the voltage magnitudes and the phase angles at the buses were captured as show
in fig: 6and 7
CONCLUSION
The introduction of virtual laboratories will go along way into the syllabi of the institutions of
higher learning will equip students with a higher level of practical background as they await to
use the real systems in the field. It is efficient and safe on the materials required to be used in the
actual experiments the virtual laboratories gives room for testing of new systems and models
before they are implemented and thus boosts technological advancement.
The paper tries to alienate the common practice of memorization and pattern recognition and
adopt concept mastery to both parties; the lecturer and the student and thus avoid the false sense
of subject mastery. This often results from the availability of such patterns in written articles that
have been widely used as teaching aids rather than the actual generation of the signals. As a
prerequisite for confident understanding one has to work and apply abstract concepts in the real
life scenarios.
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REFERENCE
B. Izaias Silva, K. R. (n.d). Modeling and Verifying Hybrid Dynamic Systems Using CheckMate .
Cheng K.W.E. Chan C.L., C. N. (n.d). Virtual Laboratory Development for Teaching Power
Electronics.
Core, S. &. (n.d). SHELL & CORE: LABORATORY. GSA Unit Cost Study .
Federico Milano, L. V. (2008). An Open Source Power System Virtual Laboratory:The PSAT
Case and Experience. VOL. 51, NO. 1,.
Mats Larsson, M. I. (2004). An Educational Tool for Power System Stability Studies.
ObjectStab.
Min Li, X. W. (2005). Q-DPM. An Efficient Model-Free Dynamic Power Management
Technique .
Navarro, I. R. (2002). Dynamic Load Models for Power Systems. Estimation of Time-Varying
Parameters During Normal Operation .
Subrata Karmakar, N. K. (2009). World Transactions on Engineering and Technology Education.
A remotely operated high voltage laboratory for impulse voltage testing .

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