Richard sseruwagi project_report_draft_copy

MAKERERE UNIVERSITY
COLLEGE OF ENGINEERING DESIGN ART AND
TECHNOLOGY
SCHOOL OF ENGINEERING
DEPARTMENT OF ELECTRICAL AND
COMPUTER ENGINEERING.
DESIGN OF COMPUTER BASED POWER AND MACHINE LABS
FINAL YEAR PROJECT REPORT
A final year project report submitted in partial fulfillment of the requirement for the award
of the degree in Bachelor of Science in electrical engineering
Student’s name: Richard Sseruwagi
Registration No. 08/U/469
Student No. 208 000 830

i
Declaration
I Richard Sseruwagi declare that the information presented in this document is an original composition
and has never been presented anywhere for academic purposes.
Richard Sseruwagi
………….......................................... Date: …………………………………………
Supervisor
Mr. Cosmas Mwikirize
………………………………………………… Date: …………………………………….
Co supervisor
Dr. Julius Butime
………………………………………………… Date: ………………………………………..

ii
Dedication
I dedicate this piece of work to my dear lovely Mum Mrs. Jane Lugoloobi and brother Mr. Paul Wamala.
They have contributed greatly to the person I am today.

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Acknowledgements
By no means have I been an island all the way through this research to the completion of this report. I
thank the Almighty God for giving me the grace to pursue my happiness in all things and for having been
a provider despite the situations.
I feel indebted to all my college supervisors; Mr. Cosmas Mwikirize and Dr. Julius Butime. They have
been very instrumental in this project.
I also want to appreciate the work of my project partner Mr. David Ssemwogerere.
Finally I want to appreciate the work of all my family, friends and relatives who have always been there
in times of need. My work would not be complete without you, Mum
Richard Sseruwagi

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Table of Contents
Declaration.....................................................................................................................................................i
Dedication..................................................................................................................................................... ii
Acknowledgements...................................................................................................................................... iii
Table of Contents......................................................................................................................................... iv
List of figures............................................................................................................................................... vii
List of tables............................................................................................................................................... viii
List of acronyms........................................................................................................................................... ix
Preface .......................................................................................................................................................... x
Chapter1. Introduction ................................................................................................................................1
1.1. Project Background............................................................................................................................1
1.1.1 Power systems lab background ...................................................................................................1
1.1.2 Machines lab back ground...........................................................................................................1
1.2. Problem statement............................................................................................................................1
1.3 Objectives............................................................................................................................................1
1.3.1. General objective........................................................................................................................1
1.3.2 Specific objectives of the project.................................................................................................1
1.4 Justifications........................................................................................................................................2
1.5 Scope...................................................................................................................................................2
1.6 Methodology.......................................................................................................................................2
Chapter 2: Literature Review........................................................................................................................3
2.0 Power system planning.......................................................................................................................3
2.1. Stability studies..................................................................................................................................4
2.1.1 TRANSIENT STABILITY STUDIES....................................................................................................8
2.2 Optimal power flow/Load flow studies ............................................................................................12
Formulation of network equations.....................................................................................................12
2.3. Programming logic controllers (PLC)................................................................................................18
2.3.1 Structure of a PLC.......................................................................................................................18
2.3.2 Types of PLC programming ........................................................................................................20
2.4 Induction motors ..............................................................................................................................21

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2.4.1 Introduction ...............................................................................................................................21
2.4.2 Induction motor Protection .......................................................................................................26
2.5 Adjustable speed drives or Variable speed drives (VSD) ..................................................................30
Control platforms................................................................................................................................31
Chapter 3. Design and simulation of the Project........................................................................................33
3.0 Power System Laboratory.................................................................................................................33
Why use both LabVIEW and MATLAB.................................................................................................33
Power lab requirements .....................................................................................................................33
Summary of programs ........................................................................................................................34
Load flow programs ............................................................................................................................34
Transient stability program.................................................................................................................38
3.1 Machines Lab Design ........................................................................................................................41
Operational Description......................................................................................................................41
Equipment Layout...............................................................................................................................41
Component description ......................................................................................................................42
Program description: ..........................................................................................................................44
PLC module installation ......................................................................................................................48
Power requirements of the induction motor. ....................................................................................50
Motor contactor connection to PLC....................................................................................................50
Addressing the devices .......................................................................................................................52
Chapter 4. Challenges, Conclusions and recommendations.......................................................................53
4.1. Summary of results..........................................................................................................................53
4.2. Challenges and limitations...............................................................................................................53
4.3. Recommendations...........................................................................................................................53
References ..................................................................................................................................................54
Appendix I: Budget and Code .....................................................................................................................57
Budget for the Project.............................................................................................................................57
COMPUTER BASED POWER AND MACHINES LAB PROJECT BUDGET .....................................................57
Flow charts..............................................................................................................................................58
Matlab script code ..................................................................................................................................59
Load flow:Radial power system..........................................................................................................59
Load flow: ring power system.............................................................................................................60

vi
Transient stability................................................................................................................................62
Appendix II:Labs..........................................................................................................................................64
PROJECT CD.................................................................................................................................................72

vii
List of figures
Figure 1. A figure illustrating power system studies.....................................................................................3
Figure 2. a diagram of a synchronous machine showing torque acting on it...............................................6
Figure 3,Plots of delta against time ..............................................................................................................7
Figure 4. An equivalent circuit for one phase of the system......................................................................13
Figure 5. The Basics parts of a PLC..............................................................................................................18
Figure 6. a simple model containing the virtual components of a PLC memory........................................19
Figure 7. The construction of a squirrel cage motor...................................................................................23
Figure 8. the structure of a wound rotor induction motor.........................................................................24
Figure 9. A block diagram showing the connection of external resistors to the rotor...............................24
Figure 10. Power flow in motor ..................................................................................................................29
Figure 11,Line regenerative variable frequency drives, showing capacitors(top cylinders) and inductors
attached which filter the regenerated power. Source: wikepia.................................................................30
Figure 12.General configuration of electronic VSDs...................................................................................32
Figure 13. summary of program architecture.............................................................................................34
Figure 14. The radial power system............................................................................................................35
Figure 15.Front panel of the lab in labVIEW...............................................................................................35
Figure 16.Block diagram of radial power system load flow in labVIEW .....................................................36
Figure 17. The ring power system...............................................................................................................37
Figure 18.Front panel of the ring power system load flow solver in LabVIEW...........................................38
Figure 19. The Front panel of the running program for transient stability ................................................39
Figure 20. An unstable system....................................................................................................................40
Figure 21. A stable system ..........................................................................................................................40
Figure 22. PLC program flow chart .............................................................................................................43
Figure 23. PLC program in LOGO! Soft Comfort Demo version..................................................................44
Figure 24. Temperature sensor...................................................................................................................49
Figure 25. an induction motor diagram......................................................................................................50
Figure 26. Connection of variable speed drive to the outputs of the PLC..................................................51
Figure 27. An ethernet port on a PLC for network communication ...........................................................51
Figure 1. The ring power system.................................................................................................................65

viii
List of tables
Table 1. A summary of the project methodology.........................................................................................2
Table 2. Project Bugdet...............................................................................................................................57

ix
List of acronyms
PLC programmable logic controllers
NR Newton Raphson
DCS Distributed Control System
SCADA Supervisory Control and Data Acquisition
VSD variable speed drives
CPU Central Processing Unit
NO normally open
NC normally closed
SFC Sequential Function Chart
FBD Function Block Diagram
LD Ladder Diagrams
ST Structured Text
IL Instruction List
RTE run time engine

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Preface
This is a final year project report. The project title is development of computer based power and
machine labs. This report contains fives chapters
Chapter one is an introductory chapter it contains the project background, the problem statement, the
project objectives, the justification and a brief description of the project methodology.
Chapter two is a literature review chapter on power systems planning with emphasis on load flow and
transient stability studies. Under load flow studies the report contains of the several load flow methods,
the reasons for carrying out load flow.it also contains details on induction motors, PLCs, VSDs and
temperature sensors.
Chapter three contains the lab designs, system requirements and actual implementations of both the
machines and power systems lab.
Chapter four is a conclusive chapter. It contains a summary of the results, challenges and limitations;
and recommendations.

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Chapter1. Introduction
1.1. Project Background
1.1.1 Power systems lab background
Load flow studies and transient stability studies are done in power systems engineering I and II; and network
theory II course units of the Bsc. Electrical Engineering program. These studies are carried out in the planning
of a power system. The project aims at designing a load flow and transient stability lab using an easy
programming environment.
Power systems load flow and transient stability programs have also been implemented before using
MATLAB/Simulink in several universities around the world like IIT Bombay India.
1.1.2 Machines lab back ground
Induction machines, PLC and VSDs are studied under three course unit Electrical machines, power electronics
and energy conversion course units. With the knowledge from these course units, this project aims at
simulating an induction motor temperature protection lab that can remotely be accessed by students.
Similar projects have been implemented before in these same areas in the universities all over the world
like IIT. Examples include these below
Speed Control of 3-Phase Induction Motor Using PIC18 Microcontrollers by Padmaraja Yedamale
Microchip Technology.
Fault Detection and Protection of Induction Motors Using Sensors by Ramazan Bayindir ,Ibrahim Sefa,
IIhami Colak, Askin Bektas 3rd September 2008.
Video from www.youtube.com 21st
august, 2011. Video name: smart motor control center using a
PLC.
1.2. Problem statement
Despite power systems engineering and electrical machines being core course units of the Bsc. Electrical
engineering course there is not enough equipment to enable students carry out labs in these fields. Let alone
equipment in these fields is costly. This project seeks to be a stepping stone for more of the other labs that
will be designed in the respective fields especially in industrial automation. It aims at creating laboratories
that can be done on a computer.
1.3 Objectives
1.3.1. General objective
To develop power and machine labs to give every student an opportunity to carry out simple power and
electrical machines studies using computer based platforms
1.3.2 Specific objectives of the project
To design for the development of an induction motor protection system using a programmable logic
controller

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To carry out load flow and transient stability studies in a power system.
1.4 Justifications
The labs would be easily accessed by students
The labs are cost effective only one piece of equipment would be put online and used by multiple
users are set time intervals.
There are no electric hazards involved for example electric shocks
This report also is a contribution to the design and research in industrial automation field for the
college.
1.5 Scope
This project focuses on development of computer based labs for power system load flow studies on a radial
and ring power system and transient stability study on a simple power system for academic purpose. The
project also entails design for the development of an induction motor temperature protection system using a
PLC.
1.6 Methodology
Table 1. A summary of the project methodology
MILESTONES WORK PACKAGES DELIVERABLES
1.REQUIREMENTS ANALYSIS i. Literature review on load
flow, transient stability
and PLC hardware
structure.
ii. Familiarizing with NI
LabVIEW, MATLAB and
PLC programming
software.
2.DESIGN SPECIFICATIONS i. Power systems
configurations.
ii. Program flow chart
designs.
iii. Machines lab hardware
architecture.
Matlab code for load flow and
transient stability
PLC Program code
3. IMPLEMANTATION i. LabVIEW code for load
flow and transient
stability.
ii. PLC program coding.
Power lab program designs
Siemen PLC program
Machines lab Hardware
specifications.

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Chapter 2: Literature Review
2.0 Power system planning
Electric power systems have evolved over the century from low voltage dc links serving small areas to highly
interconnected HVAC serving several countries. Power systems are one of the largest man made system. They
consist of generation units normally synchronous , DC sources such solar panels, wind generators, and other
renewable energy sources; transmission back bone this consist of substations and transmission wires; and
loads, these are power consumption centers. They can be domestic, commercial and industrial. Running this
very large system is a real difficult task. It has stability issues.
Power systems planning is a process in which the aim is to decide on new as well as upgrading existing system
elements , to adequately satisfy the loads for a foreseen future. The main aim of planning electrical power
systems is to fully serve the interests of the consumers to be supplied with electricity. Power system studies
consist of studies for more than 10 years. Power systems planning studies are both done for the current and
future states of the power system. In that case they are both operational and planning studies respectively.
The figure below explains what entails power systems planning studies
Figure 1. A figure illustrating power system studies

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Explanation
First, suppose it’s foreseen that a predicted load in 10 years from now may be served by a new power plan
which is to be built. A power system planning engineer would have to decide on its capacity, type and the
point at which it should be connected to the network. Once that decision has been made, its construction has
to be started ahead of time so that the power plant is available in 10years.
Second, suppose a transmission line is to be built passing through a rugged area. One built it may be subject
to sever lightning. This affects the system in fractions of seconds. The designer should think have proper
protection or fault clearing systems in place to ensure the line doesn’t fail in the case of lightning. This is a
short term study of the power system. Provided sufficient information and resources are availed the system
designer should carry out a 1 week to 1 year study to decide in advance, on the maintenance of the power
system components. This type of study is called maintenance scheduling.
Operational planning starts from 1 week to minutes. These types of studies may be generally classified as.
Hours to 1 week (for example unit commitment)
Several minutes to 1 hour (economic dispatch, optimal power flow )
Minutes (automatic generation control)
Next is the power system dynamics study, which is done in the order of milli seconds to seconds. In this time
period, the effects of power plant excitation system and governors are considered significant. Two major
study areas are the small signal, large signal, voltage stability and sub synchronous resonance phenomenon,
The very far end of the diagram consists of very fast phenomenon of power system behavior. It is called
power system transients studies, involving studies on lightning, switching transients and similar,
In our study of the power system planning in this report we are going to focus only on two fields. Optimal load
flow studies/ load flow studies and transient stability of a simple power system.
2.1. Stability studies
The tendency of a power system to develop restoring forces equal to or greater than the disturbing forces to
maintain the state of equilibrium is known as “stability”.
The problem of interest is one where a power system operating under a steady load condition is perturbed,
causing the readjustment of the voltage angles of the synchronous machines. Such an occurrence may create
an imbalance between the system generation and load; it results in the establishment of a new steady-state
operating condition, with the subsequent adjustment of the voltage angles.
The disturbance could be a major disturbance such as the loss of a generator, a fault or the loss of a line, or a
combination of such events. It could also be a small load or random load changes occurring under normal
operating conditions. The time taken for adjustment to the new operating condition is called the transient
period. The system behavior during this time is called the dynamic system performance, which is of concern in
defining system stability.
The main criterion for stability is that the synchronous machines maintain synchronism at the end of the
transient period. So we can say that if the oscillatory response of a power system during the transient period
following a disturbance is damped and the system settles in a finite time to a new steady operating condition,
we say the system is stable. If the system is not stable, it is considered unstable. This primitive definition of
stability requires that the system oscillations be damped. This condition is sometimes called asymptotic
stability and means that the system contains inherent forces that tend to reduce oscillations. This is a

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desirable feature in many systems and is considered necessary for power systems. The definition also
excludes continuous oscillation from the family of stable systems, although oscillators are stable in a
mathematical sense. The reason is practical since a continually oscillating system would be undesirable for
both the supplier and the user of electric power. Hence the definition describes a practical specification for an
acceptable operating condition. The stability problem is concerned with the behavior of the synchronous
machines after a disturbance.
For convenience of analysis, stability problems are generally divided into three major categories-steady state
stability and transient state stability, transient state stability and dynamic stability.
THE SWING EQUATION
This is a mathematically modeled equation used to determine the stability of the power system. It considers
the energy flows within and without the system.
Under normal operating conditions, the relative position of the rotor axis and the resultant magnetic field axis
is fixed. The angle between the two is known as the power angle or torque angle δ. During any disturbance,
rotor will decelerate or accelerate with respect to the synchronously rotating air gap mmf, a relative motion
begins. The equation describing the relative motion is known as the swing equation.
Synchronous machine operation:
The equation of motion of a rotating machine.
Kinetic energy absorbed by a rotating mass = joules (1)
Where I is the moment of inertia
ω is the angular velocity in rad s-1
Angular momentum M= (2)
The inertia constant H is defined as energy stored per unit volt –ampere so if the VA rating of the machine isG.
Kinetic energy =
= =
Pole pairs or electrical angles per second
Thus (3)
Let
θm = rotor angle in Mechanical degrees
θsm = System angle in Mechanical degrees
Then (4)
where δm is the rotor position

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Differentiating (4) w.r.t to time twice to get the second derivative and assuming that θsm is constant gives that
Figure 2. a diagram of a synchronous machine showing torque acting on it
Now consider the synchronous machine above developing an electromagnetic torque Te and corresponding
electromagnetic power Pe while operating at a synchronous speed ωs if the input torque provided by the
prime mover, at the generator shaft is Ti , then under steady state conditions/
Here we have neglected any retarding torque due rotational losses. Therefore we have
And thus
Where E is the internal emf of the generator
V is the terminal generator emf
X is the fault reactance
Under a disturbance such as a change in load or a fault then
A disturbance occur will result in accelerating/decelerating torque Ta=Tm-Te (Ta>0 if accelerating, Ta<0 if
decelerating).
If is the accelerating power then
Where M and ϴsm have been defined as above and D is the damping coefficient
Neglecting D we obtain

7
Diving through by the base MVA G we get a
This is known as the swing equation
Stability analysis using the equal area Criterion
The solution to the swing equation is used to analyze the stability of a system
Figure 3,Plots of delta against time
The solution to
Is obtained using numerical methods discussed later.
If , then the system is unstable however, if then the system is
stable.
Factors that determine the stability of a power system
Clearing time by the circuit breakers in case of a fault
Generator output electrical power
The main factor we analyze in this report is the critical clearing time which is the minimum time within which
a fault must be cleared if the power system is to remain stable. The corresponding power angle is the critical
power angle.

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2.1.1 TRANSIENT STABILITY STUDIES
The transient stability studies involve the determination of whether or not synchronism is maintained after
the machine has been subjected to severe disturbance. This may be sudden application of load, loss of
generation, loss of large load, or a fault on the system. In most disturbances, oscillations are of such
magnitude that linearization is not permissible and the nonlinear swing equation must be solved
Transient stability studies are done by obtaining numeral solution to the swing equation.
Numerical solutions to the swing equation are below
The swing equation can be solved using
Step by step method
Runge-Kutta method
Euler modified method
Predictor-corrector routines
Assumptions:
The accelerating power at the constant at the commencement of a time interval considered to be
constant from the middle of the previous interval to the middle of the interval considered.
The angular velocity is constant over a complete interval and is computed for the middle of the
interval.
a) Step by step/ point by point method
The swing equation may be solved iteratively by the step by step procedure explained below. It is always
required to know the critical clearing time corresponding to critical clearing angle so as to design the
operating times of the relay and circuit breaker so that time taken by them should be less than the critical
clearing time for stable operation of the system. So the point-by-point method is used for the solution of
critical clearing time associated with critical clearing angle. The step-by-step or point-by-point method is the
conventional, approximate but proven method. This involves the calculation of the rotor angle as time is
incremented. The accuracy of the solution depends upon the time increment used in the analysis.
Assumptions
It is assumed that the accelerating power Pa and the relative rotor angular velocity ωr are constant within each
of a succession of intervals; their values are used to find the change in δ during each interval.
Initially we need to find Pa (0+)
The swing equation may be written
The change in is given by

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Similary the change in the power angle for the first interval is
And so
Evaluation of
If there is no discontinuity in the swing curve during an iteration interval, then is equal to half of
immediately after the fault. If there is a discontinuity at the beginning of the ith
interval, then
Where and are, respectively the acceleration power immediately before and after the fault
is cleared.
If the discontinuity occurs at the middle of an interval, then for that interval
For this case, at the beginning of the interval immediately following the clearing of the fault,
is given by
Algorithm used for the method
With this algorithm the critical clearing angle and the corresponding critical clearing time can be solved for
any power system.
b) RUNGE-KUTTA (R-K) METHODS
The R-K methods approximate the Taylor series solution; however, unlike the formal Taylor series solution,
the R-K methods do not require explicit evaluation of derivatives higher than the first. The effects of higher

10
derivatives are included by several evaluations of the first derivative. Depending on the number of terms
effectively retained in the Taylor series, we have R-K methods of different orders.
Second-order R-K method
Consider this differential equation.
Where x is the state vector of n dependent variables and t is the independent variable (time). Our objective is
to solve x as a function of t, with the initial values of x and t equal to and respectively.Referring to the
above differential equation, the second order R-K formula for the value of x at t = t0+ ∆t is
where
This method is equivalent to considering first and second derivative terms in the Taylor series; error is on the
order of ∆t.
A general formula giving the value of x for (n+1)st
step is
Where

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Fourth-order R-K method
The general formula giving the value of x for the (n + 1) th
step is
Where
The physical interpretation of the above solution is as follows:
k1 = (slope at the beginning of time step) ∆t
k2 = (first approximation to slope at mid-step) ∆t
k3 = (second approximation to slope at mid-step) ∆t
k4 = (slope at the end of step) ∆t
Thus ∆x is the incremental value of x given by the weighted average of estimates based on slopes at the
beginning, midpoint, and end of the time step.
This method is equivalent to considering up to fourth derivative terms in the Taylor series expansion; it
has an error on the order of ∆t
c) Modified Euler method
This method is also based on the Taylor’s expansion of an equation.
Assume the equation to be solved is
Where the initial condition is such that
The first procedure is to find an initial approximation.
Where h is the unit step change in t.
Then y is calculated from it using this equation.

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2.2 Optimal power flow/Load flow studies
This is mainly steady state analysis of an interconnected power system during normal operation. It is
assumed that the system is under normal operating condition and is represented by a single line
diagram.
Load flow studies are essential for the planning, economic operation, scheduling and exchange of
power between utilities. Load flow studies are also required for transient stability, dynamic stability,
contingency and state estimation
Load flow studies are done by generating network equations. The commonest is the node voltage
method where the nodes are taken to be the buses in the power system. The network equations which
are in the nodal admittance form results in complex linear simultaneous equations in terms of node
currents. The solutions are gotten using iterative methods or simpler methods. The load flow results
give the bus voltage magnitudes and phase angles and hence power flow through the transmission line,
line loses and power injected at all the buses.
The purpose of load flow is to investigate the following
The flow of real and reactive power in the branches of the network
Bus bar voltages
The effect of rearranging circuits and incorporating new circuits on the system, (loading)
The effect of temporary loss of generation and transmission on system loading
The effect of injecting in-phase and quadrature boost voltages on system loading
Optimum system running conditions and load distribution
Minimizing of system losses
Optimum rating and tap range of tap changing transformes
Improvement from change of conductor size and system voltage.
Types of bus bars or nodes in a power system
To enable us form network equations the buses in the power system are classified according the
quantities P,Q, V , and δ i.e. real power, reactive power, bus voltage and angles.
Slack, swing or floating bus bar
This is the node having a voltage specified constant in magnitude and phase. It is taken as the
reference bus. The effective generator at this node supplies the losses to the network.
Load nodes or P,Q bus bar
This node has the real and reactive power outflow known
Generator nodes or P,V bus bar
This node has the voltage and real power magnitude specified.
Formulation of network equations
The network equations are based on ohms law.
[ V ] =[ I] [Z]
Where
[V] is the nodal voltage matrix

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Figure 4. An equivalent circuit for one phase of the
[I] Is the nodal current matrix
[Z] is the impedance matrix
Since we are normally interested in the current
[I] = [Y] [V]
[Y] Being the nodal admittance matrix
Load flow studies are based on a nodal voltage analysis of a power system. As an example, consider the
very simple system represented by the single-line diagram. Here two generators (1 and 2) are
interconnected by one transmission line and are separately connected to a load (3) by two other lines.
If the phasor currents injected into the system are I1, I2, and I3, and the lines are modeled by simple
series admittances, then it is possible to draw the equivalent circuit for one representative phase of the
balanced three-phase system below.
Generator, 1
Generator, 2
y13 y23
I1
I2
V3
load, 3 I3
Single-line diagram of the sample example power system

14
I1= (V1-V2)*y21 + (V1-V3)*y31
I2= (V2-V3)*y32+(V2-V1)*y21
I3= (V3-V2)*y32 + (V3-V1)*y31
thus
I1= (y21+ y31)* V1 + V2 *-y21 -V3*y31
I2= -V1*y21 + (y32+ y21)* V2 -V3*y32
I3= -V1*y31 -V2*y32+ (y31 + y32)*V3
This is further reduced to
I1= Y11* V1 + V2 *Y12 +V3*Y31
I2= V1*Y21 + Y21* V2 + V3*Y32
I3= V1*Y31 +V2*Y32+ Y32*V3
Where
Yii = is the bus self-admittance
Yin =- yin is the mutual admittance
This can be written as
Calculation of power flow
Substituting and making Vi the subject gives

15
This equation is iteratively solved to get the bus voltage and angle at any given bus.
Methods used to solve network equations.
For systems with few bus bars the above equations can easily be solved algebraically. For cases with
many bus bars numerical methods are used to obtain solutions
Newton raphson
Gauss
Gauss siedel
Fast decoupled method
Stochastic search techniques such as the genetic algorithm and simulated annealing
Fuzzy logic application
Hybrid Particle Swarm Optimization
a) Gauss-Seidel Method
Gauss-Seidel method is also known as the method of successive displacements. To illustrate the
technique, consider the solution of the nonlinear equation given by
Above function is rearranged and written as
If x=(k) is an initial estimate of the variable x, the following iterative sequence is formed
A solution is obtained when the difference between the absolute value of the successive iteration is
less than a specified accuracy, i.e.
Where ε is the desire accuracy
The process is repeated until the change in variable is within the desired accuracy. So the Gauss-Seidel
method needs much iteration to achieve the desired accuracy, and there is no guarantee for the
convergence.
b) Newton-Raphson Method
This is an iterative method which approximated the set of nonlinear simultaneous equations to a set of
linear equations using Taylor’s series expansions and the terms are restricted to the first order or
second order approximation. The Newton-Raphson method using the bus admittance matrix in either
first or second – order expansion of Taylor series has been evaluate as a best solution for the reliability
and the rapid convergence.
If x
(0)
is an initial estimate of the solution, and ∆ x
(0)
is a small deviation from the correct solution, we
must have
Expanding the left-hand side of the above equation in Taylor’s series about x(0) yields
Assuming the error ∆ x
(0)
is very small, the higher-order terms can be neglected, which result in

16
where
Adding ∆ x
(0)
to the initial estimate will result in the second approximation
Successive use of this procedure yields the Newton-Raphson algorithm
can be rearranged as
where
J
(k)
is called the Jacobean matrix. Element of this matrix are the partial derivatives evaluated at X
(k)
.
It is assumed that J
(k)
has an inverse during each iteration. Newton’s method, as applied to a set of
nonlinear equations reduces the problem to solving a set of linear equations in order to determine the
values that improve the accuracy of the estimates.
c) Fast Decoupled Method
When solving large scale power transmission systems, an alternative strategy for improving
computational efficiency and reducing computer storage requirements is the decoupled power flow
method, which makes use of an approximate version of the Newton-Raphson procedure.
The Fast decoupled power flow solution requires more iterations than the Newton-Raphson
method, but requires considerably less time per iteration and a power flow solution is obtained very
rapidly. This technique is very useful in contingency analysis where numerous outages are to be
simulated or a power flow solution is required for on-line control.
d) Stochastic Search Techniques
Introduction to general principles
Recent developments in load flow analysis have moved attention away from the iterative methods and
towards so-called stochastic search methods. Examples of such methods include two such methods –
Genetic Algorithms and Simulated Annealing. Both approaches use a series of trial solutions to the
problem and develop better solutions in the light of experience gained from these trials. The
computational effort for each trial is kept as low as possible, so a very large number of trials can be
conducted.
For example suppose there are three variables: the voltage magnitude |V3| and the phase angles δ2 ,
and δ3
In any one trial some appropriate values are chosen for these variables. The choice may be an entirely
random selection across the entire possible range of values (termed the’ search space’) or the choice
may be informed by previous experience. Once these trial values are chosen, the phasor voltages at all

17
three nodes are defined, because all of the other voltage magnitudes and phase angles are fixed.
Therefore the currents injected at each node can be evaluated directly using the load flow equations
formulated above.
The success of the trial needs to be judged by some quantitative criterion. The trial values of node
voltage lead to values of input power and reactive power (P, Q) that do not exactly match the pre-
defined values (Ps, Qs). The extent of the mis-match can be quantified conveniently, for this particular
problem, with the error function:
The stochastic search techniques use the error function to inform the selection of new potential
solutions for the subsequent round of trials. It is this selection process which is defined by the particular
search technique.
i. Genetic Algorithms
Genetic Algorithms imitate the process of evolution, where the fittest individuals are likely to survive in
a competing environment. A genetic algorithm starts with a random population of potential individuals,
or chromosomes, each representing one possible solution to a problem. The chromosomes are simply a
collection of genes, each gene being one of the solution variables. The chromosomes are then evolved
through successive generations. During each generation, all the chromosomes are evaluated, according
to a defined fitness criterion, and the best chromosomes are selected to mate and generate offspring.
The least fit chromosomes of each population are then replaced by the offspring so that the population
size remains constant. After several generations, the algorithm converges to the best chromosome
which represents an optimal solution to the problem.
A further refinement of the evolution process, again mirroring nature, is that any chromosome in any
generation has a finite probability of suffering mutation, in which some of the genes are randomly
perturbed. It is this process which ensures that the genetic algorithm does not converge to a local
minimum when searching for a global problem solution.
When applied to the load flow problem, the genes are the nodal voltage magnitude and phase angle
values and each chromosome contains a complete set of the genes needed to define uniquely a trial
solution. The fitness of each chromosome is evaluated using the error criterion, which is used as the
basis of selection for the chromosomes in the next generation.
ii. Simulated Annealing
Simulated annealing is a global search technique in which a randomly-generated potential solution, Y,
to a problem is compared to an existing solution, X. The probability of Y being accepted for investigation
depends on the proximity of Y to X and the extent to which the solution has been developed, as
represented by a ‘temperature’ parameter, T, which reduces throughout the annealing process. Both
potential solutions are investigated and Y is chosen to replace X as the existing solution according to a
probability function which again depends on the temperature T.
To apply this concept to load flow studies in general, it is assumed that the solutions X and, Y, represent
information about possible nodal voltage value

18
2.3. Programming logic controllers (PLC)
A PLC (Programmable Logic Controllers) is an industrial computer used to monitor inputs, and
depending upon their state make decisions based on its program or logic, to control (turn on/off) its
outputs to automate a machine or a process. PLCs are digitally operating electronic apparatus which
uses a programmable memory for the internal storage of instructions by implementing specific functions
such as logic sequencing, timing, counting, and arithmetic to control, through digital or analog
input/output modules, various types of machines or processes. They are based on the Boolean logic
operations whereas some models use timers and some have continuous control. These devices are
computer based and are used to control various process and equipment within a facility. Nowadays PLCs
control the components in the DCS and SCADA systems but they are primary components in smaller
control configurations. PLCs have replaced conventional relay systems in industries.
Advantages of PLC control over relays
PLCs are rugged and are designed to withstand vibrations, temperature, humidity, and noise.
Have interfacing for inputs and outputs already inside the controller.
Easily programmed and have an easily understood programming language.
PLC are flexible since there programs can be modified to suite a change of conditions while
physical relays would need to be physically replaced
PLCs are more reliable than relays due to the absence of moving parts.
PLCs are much less bulky than conventional relay control systems.
2.3.1 Structure of a PLC
The basic components of a PLC are as shown below
Figure 5. The Basics parts of a PLC
Input module

19
This serves as an interface between the actual control devices and the CPU. The inputs are sensing
devices such as temperature sensors, optical sensors, torque sensors, etc.
Output module
This serves as an interface between the actual device being controlled and the CPU.
A central processing unit (CPU).
The CPU is the brain of a PLC. It’s a complex circuit composed of one or more microprocessors. The CPU
contains two types of memory; volatile and non-volatile memory. The CPU is a computer which can
simulate the required relay contacts and relay coil, as well the connection between them. It has a
memory function and an operational function. We can imagine that it contains an enormous stock of
contacts and relay coils. This inventory of parts is stored in the memory of the CPU.
Figure 6. a simple model containing the virtual components of a PLC memory
The contacts that correspond to the relay coils (rectangles) in the input module. The number of contacts
per coil and their NO (normally open) and NC (normally closed) condition is set by means of the
programming unit. The contacts are I1, I2 and I3 for the input module and O1, O2, O3 and O4 for the
output module.
The coils of the relays associated with the four NO contacts in the output module. These particular coils
carry the same reference number as the contacts they activate. 111,112 and 113
The relay coils and contacts of the internal relays. The coils and contacts of these internal relays operate
entirely inside the CPU; they don’t appear in the input or output modules.

20
The CPU performs the following sequential functions
During a brief interval, the CPU checks all the input modules and recorded the on/off status
of the external control devices that are connected to them.
The CPU runs the programs of the user. During this period and depending on the program
and the status of the inputs that have been recorded the CPU decides which outputs should
be activated. While the CPU program is being carried out, these decisions are stores in a
memory section reserved for this purpose.
The CPU transmits the memorized decisions to the output modules. During this interval, the
output modules activate or deactivate the external devices that are connected to the output
terminals. The operating cycle consists of taking successive readings of the status of inputs,
carrying out the user program, and transmitting the results to the output modules. The
operating cycle is known as scanning. The sequential scanning process goes on continually
when the PLC is in operation. The time to make a complete scan depends upon the speed of
the PLC and the size of the user program.
During the scanning process, the CPU systematically checks the correct function of the
hardware by diagnostic analysis.
The programming unit
This normally consists of a keyboard and display unit to program the CPU. It enables us to select the
different types of ‘relays’ and ‘contacts’ that the computer can simulate, as well as the way they are to
be connected.
The power supply
This furnishes the power needed by the CPU, by the I/O modules and the programming unit. It can be
24V to 120V ac or 5V to 100V dc.
2.3.2 Types of PLC programming
Programming languages for a PLC are lists of symbols used and the way they have to be configured to
program a PLC. Below are examples of PLC programming languages.
Ladder diagram
This is one of the simplest of the programming languages. In programming from the keyboard the
desired circuit is progressively displayed on the monitor. The desired function in selected by pushing an
appropriate key to create a NO or NC ‘contact’ an ‘internal relay coil’ an ‘output relay coil’ and so forth/
when the function is chosen it’s given a reference number. This procedure is followed for the rest of the
control circuit.
Boolean logic language

21
This is based on Boolean algebra. One of the major draw backs of this language is the difficulty one has
in reading it but starting from a ladder diagram its quite easy to develop code for a Boolean algebraic
program.
Instruction List (IL)
It’s a low-level textual language with a structure similar to assembler. IL is well suited for solving small
straightforward problems and producing optimized code, but it does not support structured
programming.
Structured Text (ST):
This is a high-level procedural programming language. ST borrows its syntax from Pascal, augmenting it
with some features from Ada. ST enforces data typing and support structured programming. Sometimes
considered the new PLC programming language, it provides useful means to handle the complexity and
modularity of modern programmable controllers.
Ladder Diagrams (LD):
This is an evolution of electrical wiring diagrams. LDs supply a programming style borrowed from
electronic and electrical circuits. LDs are ill suited for the complexity of today's controllers and
structured programming, but help legacy systems.
Function Block Diagram (FBD):
This is a graphical language. Controllers are modeled as signal and data flows through processing
elements (function block). FBD transforms textual programming (ST) into connecting building blocks,
thus improving modularity and software reuse.
Sequential Function Chart (SFC):
This is also a graphical language. SFC is used for structuring the internal behavior of PLC processing
elements. SFC elements partition processing elements into sets of steps and transitions among them
interconnected by directed links. Steps are associated with actions; transitions with predicates
(conditions).
2.4 Induction motors
2.4.1 Introduction
Most Industrial processes today are based on motor operation. So the protection of motors is a relevant
subject for the reliability and durability of motors. Motors are either ac or dc motors. The majority of the
electrical motors in industry today operate on alternating current since alternating voltage can be easily
transformed from high voltages to low voltages or vice versa, it can be transmitted over a much greater
distance without too much loss in efficiency. However, there are other advantages in the use of AC
motors besides the wide availability of AC power.

22
Comparisons of AC versus DC motors
They have a readily available power supply
They are cheaper
They have a lower maintenance cost
They are lighter
However DC motors are best suited for applications that require variable-speed motors. Most AC motors
nowadays come with AC drives. AC motors are manufactured in many different sizes, shapes, and
ratings, for use on an even greater number of applications. They are designed for use with either single-
phase or poly-phase power systems. This unit cannot possibly discuss all aspects of the subject of AC
motors. Consequently, it will deal with the most common type, which is the three phase induction
motor.
Three phase AC motors.
There are two main classes of three phase AC motors: synchronous and Asynchronous.
The main difference between these two classes is in their construction. While both have the same stator
construction, their rotors vary greatly. The purpose of the rotor in both classes is to create a rotating
magnetic field.
Synchronous motor.
These have a rotor speed equal to the speed of the stator magnetic field. In other word the speed of the
shaft is rotating at the same speed as the rotating magnetic field.
Asynchronous motor
This is one where the motor speed is not equal to the speed of the rotating magnetic field. These are
basically called induction motors.
Three phase induction motors
There are two main types of induction motors
Squirrel cage and wound rotor motors.
Both motors operate on induction and the principles are very similar. Let's first discuss the squirrel-cage
motor and its construction since it is the simplest form.
SQUIRREL-CAGE INDUCTION MOTOR
Construction
Stator

23
The stationary winding of the motor and it provides the rotating magnetic field. The stator windings are
wound around the laminated pole pieces, which are mounted to the outside housing of the motor. It is
also connected to the AC supply.
Rotor
The rotating member of the motor and it provides the torque or power to do the mechanical work. The
rotor is made of circular laminations with copper or aluminum bars imbedded around the outside edge.
It is connected to the shaft of the motor.
End Bells
Support the shaft of the motor and house the bearings.
Figure 7. The construction of a squirrel cage motor
THE WOUND ROTOR INDUCTION MOTOR
The motor consists of three electrical parts:
1. A set of insulated windings mounted on the body of the motor. These windings are similar to those
of the squirrel-cage induction motor and are also called the stator windings.
2. A set of insulated windings recessed into the laminated plates of the rotor. These windings are
always connected in the wye configuration with the three free ends brought out and each one
connected to each of three brass rings mounted on the motor shaft. These rings are the slip rings.
3. A means of making electrical connection with the slip rings is needed so that current may flow
through the rotor windings when they are in rotation. These connections are by means of brushes,
which are held in position in contact with the slip rings by the brush-holder

24
Figure 8. the structure of a wound rotor induction motor
As stated the wound rotor is constructed of windings instead of shorting bars, as in the squirrel-cage
induction motor. Like the squirrel-cage induction motor, it receives its power through induction. Its
windings are connected in a star configuration, and are accessible through the use of slip rings and brush
assembly.
Figure 9. A block diagram showing the connection of external resistors to the rotor
This access to the rotor circuit is the major advantage of the wound rotor induction motor. It allows
changes in rotor impedance, through external resistance changes. This allows the torque of the motor
to be controlled. The wound rotor induction motor can be used where the maximum torque is desired
throughout the entire speed range. As the speed changes, rotor circuit resistance is varied to maintain
the resistance of the rotor equal to the inductive reactance of the rotor (R = XL). When R and XL are
equal, the phase angle of the impedance of the rotor is 45°.
Rotating Magnetic Field
The speed of the rotating magnetic field is called the synchronous speed of the motor. The following
formula can be used to determine the speed of the rotating magnetic field created by the stator.

25
Note: When motor manufacturers describe a 2-pole motor, they are talking about the numbers of poles
that are created in the rotor due to the rotating magnetic field. For a 2-pole motor which has only 1 pair
of poles per phase.
Induction Motor Slip
An induction motor cannot run at synchronous speed since the rotor would be standing still with respect
to the rotating field and no current would be induced in the rotor. The rotor speed must be slightly less
than synchronous speed in order that current be induced in the rotor to permit rotor rotation. The
difference between rotor speed and synchronous speed is called slip:
Slip can also be expressed as a percentage of the synchronous speed
X100%

26
2.4.2 Induction motor Protection
As stated above, Induction motors make up to 70% of the world’s industry. So protection of induction
motors from faults is essential in cutting capital investment costs. The basic aim in protecting motors
is to permit the motor to operate up to its thermal and mechanical limits while not exceeding
them and providing maximum sensitivity for faults. High temperature destroys the insulation
leading to further faults.
Common causes of motor faults include single phasing, overload, voltage imbalance, Voltage too
low/high, bearing failure, rapid duty cycle, restricted ventilation, moisture and vibrations.
Induction motor protection examples include
Overload protection
Thermal overload
Electronic overload
Short circuit protection
Vibration protection
Auxiliary temperature protection.
Figure 10. Unbalance phase motor damage. Figure 11. Overload damage
If mechanical failures are eliminated, protecting the motor windings from over temperature is the prime
function of motor protection. Emphasis in this report is temperature protection.
Temperature protection is done using three main techniques.
direct temperature measurement;
thermal model-based stator winding temperature estimation
Parameter-based stator winding temperature estimation.

27
The direct temperature measurement of the stator winding is typically performed using
embedded thermal sensors, such as thermocouples, resistance thermal detectors (RTDs), infrared
thermal sensors, etc. The embedded thermal sensors are not considered cost-efficient, especially
for small- to medium- size motors, due to the high cost of their installation. Therefore, the practical
application of these embedded thermal sensors is limited.
Thermal model-based stator winding temperature estimation techniques are broadly used in the
thermal overload relays for thermal protection. These techniques first calculate the losses in a
motor, and then estimate the stator winding temperature based on a motor’s thermal model.
However, the main drawback of these thermal model-based approaches is that the thermal
parameters are not constant and measurements must be made for each motor under different
operating conditions. In addition, as the thermal parameters are fixed after identification, these
methods cannot adapt to the change in the cooling capability of the motor.
Parameter-based stator winding temperature estimation techniques are proposed to estimate
the stator winding temperature from the stator resistance, given that the variations of temperature
are proportional to the variations of resistance for stator injection-based methods are proposed to
estimate the stator winding resistance motor’s dc model. However, the application of these dc
signal injection methods is limited due to their high intrusiveness because an extra dc injection
needs to be installed in series with one of the motor loads. The major advantage parameter-based
methods are:
they can adapt to the change in the cooling capability of the motor;
only the motor terminal quantities are required;
The motor’s normal operation is not interrupted.
In this project direct temperature measurement of the stator winding is used. This is done with the help
of temperature sensing devices as mentioned above such as Klixons, Thermocouples, thermistors, and
Resistive Temperature Devices (RTDs). Temperature sensors are normally built into the windings and
measure the actual winding temperatures. There are several advantages for using this type of
protection. First, sensors detect changes in ambient temperature. Also, sensors can detect variations in
cooling conditions such as blocked ventilation or a broken fan.
Temperature sensors
Temperature sensors are devices that are used to monitor temperature changes. Temperature sensors
are categorized into contact and non-contact. Contact Temperature Sensors are required to be in
physical contact with the object being sensed and use conduction to monitor changes in temperature.
They can be used to detect solids, liquids or gases over a wide range of temperatures.
Non-contact Temperature Sensors use convection and radiation to monitor changes in temperature.
They can be used to detect liquids and gases that emit radiant energy as heat rises and cold settles to

28
the bottom in convection currents or detect the radiant energy being transmitted from an object in the
form of infra-red radiation. Examples of temperature sensing devices
Resistive temperature devices (RTD)
These are sensors in which the resistance increases as the temperature increases. The increase in
temperature is expressed in relation to degrees. Resistive temperature devices can measure
temperature ranging from 4000
F to 12000
F. They have a relatively high sensitivity.
Thermistors
These are semiconductor devices. Changes in temperature affect the resistance of the semiconductor.
Increase in temperature decreases the resistance. These temperature sensors are used in a wide
number of household appliances. Thermistors are more sensitive compared relative to other sensors.
They also have a medium to fast response time.
LM35 temperature sensors.
These temperature sensors are more precise compared to thermistors. The voltage does not have to be
boosted as these temperature sensors use a higher voltage. It is designed in way to be included in an
incorporated circuit on a circuit board. The voltage measured by this device can be expressed in Celsius
temperature. It does not require any adjustments to give accurate readings. A good thing about LM 35
temperature sensors is that it works with minimum power so the device does not heat up. When it is
included in circuits, it can give rise to many events like activating a relay when the device reaches a
certain temperature.
Other temperature sensing devices which are not of interest in this report include thermostat, infrared
sensors, liquid expansion devices, molecular change of state, silicon diodes, bimetallic devices and
thermo couples.
The temperature changes in an induction motor result from losses within the induction motor.

29
Figure 10. Power flow in motor
During normal running conditions, the current flowing through the stator windings produces stator
copper losses proportional to the square of the current. However, the losses in the stator iron are due to
magnetization and eddy currents, which are a function of voltage. The main losses in the rotor are the
rotor copper losses caused by the current induced in the cage. These losses are dependent on the
loading on the motor. Frictional losses (air and bearings) and additional losses are relatively small and
are of less importance. The heat generated in the rotor and stator leads to respective temperature rise.
The steady-state temperatures are a function of the size of the losses and for the most part a function of
the load. The heat flows between those areas and to the ambient air. The thermal conductivity of the
heat transfer paths partly depends on the speed of the motor, since an internal or an external fan's
performance is speed dependent. With an unbalanced supply and with harmonic distortions, extra
losses are created, particularly in the rotor. The negative sequence currents caused by supply
asymmetry and harmonic currents do not generate back emf. For this reason, these negative sequence
currents can reach relatively high values. This is similar to the conditions with a symmetrical supply
when staring a motor. The starting current of a motor at rest is limited only by the resistance and
inductance in the stator and the rotor. The effective rotor resistance is increased due to the effect of
current displacement or skin effect because the frequency of the current in the rotor equals line
frequency

30
2.5 Adjustable speed drives or Variable speed drives (VSD)
This is electronic equipment used to control the speed of machinery. In case speeds can be selected
from several different pre-set ranges, usually the drive is said to be adjustable speed. If the speed can be
changed without steps over a range, the drive is usually referred to as a variable speed drive. These
drives can be electronic, mechanical, electromechanical or hydraulic in nature.
Figure 11,Line regenerative variable frequency drives, showing capacitors(top cylinders) and inductors attached which filter
the regenerated power. Source: wikepia
Benefits for using drives
Reduction in energy requirements
Smoother operation
Acceleration control
Different operating speed for each process recipe
Compensate for changing process variables
Allow slow operation for setup purposes
Adjust the rate of production
Allow accurate positioning
Control torque or tension
Disadvantages
VSDs induces power line and output harmonics
Motor heating at low speeds
High initial costs.
High maintenance costs

31
Control platforms
Most drives use one or more of the following control platforms
PWM V/Hz scalar control
PWM field-oriented control (FOC) or vector control
Direct torque control (DTC).
VSD operation differs from technology to technology. The table below is a summary of the basic
electronic VSDs using scalar control platforms.
Sample operation of electronic VSD.
The speed of the rotating field created by the induction motor stator winding is directly linked with the
voltage and frequency applied to the windings. Electronic Variable Speed Drives can produce variable
frequency, variable voltage waveforms. If these waveforms are applied to the stator windings there will
Type of VSD Main characteristics
Advantages Disadvantages
Pulse-Width
Modulation
(PWM)
Voltage Source
Inverter (VSI)
Good power factor throughout speed
range.
Low distortion of motor current.
Wide speed range (100:1).
Multi motor capability
Limited to VSDs bellow 1 MW.
Slightly (about 1%) less efficient than VSI
or CSI.
Basic circuit has no regeneration
capability
Six-step Voltage-
Source Inverter
(VSI
Good efficiency.
Simple circuit configuration.
Wide speed range (10-200%).
Multi-motor capability.
Poor power factor at low speeds (unless
a
rectifier/chopper AC/DC converter is
used).
No regeneration capability.
Operation below 10% of rated speed can
produce
cogging.
Force
Commutated
Current-Source
Inverter (CSI)
Simple and robust circuit design.
Regenerative capability.
Built-in short circuit protection.
Wide speed range (10-150%).
Bulky.
Poor power factor at low speed/load.
Possible cogging below 10% of rated
speed
Load-
Commutated
Inverter (LCI)
Simple and inexpensive circuit design.
Regeneration capability.
Built-in short-circuit protection
Poor power factor at low speed.
Can only be used with synchronous
motors.
Cyclo-Converters Can operate down to zero speed.
High torque capability with field-
oriented control.
Can be used with induction and
synchronous
motors.
Cannot be used above 33% of input
frequency.
Complex circuit design.
Poor power factor at low speed.

32
be a shift of torque-speed curve, maintaining a constant pull-out torque, and the same slope of the
linear operation region of the curve. In this way, the motor speed is going to be proportional to the
applied frequency generated by the VSD.
Figure 12.General configuration of electronic VSDs.
The three-phase, 50Hz alternated current (AC) supply is initially converted to direct current (DC), then
filtered and finally, the DC/AC inverter converts the DC voltage to the variable voltage and variable
frequency output applied to the motor.

33
Chapter 3. Design and simulation of the Project
3.0 Power System Laboratory
The power systems programs are implemented using LabVIEW 2010 students’ edition and MATLAB
2012a. Matlab code is designed to run in a matlab script in LabVIEW while the LabVIEW is used to
generate a user interface with which the user can alter the power system parameter.
Why use both LabVIEW and MATLAB
LabVIEW is a kind of graphical programming language which can be used to establish Virtual instruments
for oneself conveniently. Despite there being some information processing functions in LabVIEW, it
doesn’t fully cater for the need of various numerical computation and analysis.
However, MATLAB is good for numerical analysis and processing. Therefore, it is necessary to integrate
LabVIEW with MATLAB. Inside LabVIEW there are library functions which are convenient to connect
some software standards such as TCP/IP, SQL database, DDE, and Active X. Though those modes can be
used to call MATLAB programs in LabVIEW, the process is relatively overelaborated. However, the
MATLAB Script node linking LabVIEW with MATLAB can also be realized using Active X mode; i.e.
LabVIEW as Active X automatic controller, MATLAB as Active X automatic Server. Using the MATLAB
Script node, a user can load *.m programs into block diagram or edit *.m files in a block diagram. In this
report we adopt the node mode to call MATLAB programs in LabVIEW.
Power lab requirements
Local Requirements:
A Networked computer with LabVIEW RTE
Internet explorer
Remote Requirements:
Computer with P.4 or better
LABVIEW Programming environment
Matlab 2011 (a or b) or 2012

34
Summary of programs
Figure 13. summary of program architecture
The diagram above is a summary of the program architecture. All the power lab programs are
implemented in the LabVIEW 2010 Student edition programming environment, the numerical code is
written in a matlab Script within the LabVIEW environment. So MATLAB 2011b needed to be installed on
the server computer. LabVIEW also creates the user interface needed to change the program
parameters during the lab.
Load flow programs
Two load flow programs were developed, one for a radial power system and the other for a ring power
system. The code is in the appendix.
Radial power system
The user can change the input MVA and power factor of the industrial and domestic loads. Thereby
changing the load conditions of the power system. The program outputs are the voltages at buses 2 and
3; the total current drawn from the generator, the percentage voltage drop on buses 2 and 3 and losses
in the transmission lines. Bus 1 is considered to be the generator bus with voltage V1. The generator
that is needed for that particular power system configuration can then be chosen.

35
Figure 14. The radial power system
Figure 15.Front panel of the lab in labVIEW

36
Figure 16.Block diagram of radial power system load flow in labVIEW
The ring power system
The program computes load flow of a 4 bus bar power system shown below using Gauss siedel. The user
can change the line and bus parameter as needed for the lab.

37
Figure 17. The ring power system

38
Figure 18.Front panel of the ring power system load flow solver in LabVIEW
Transient stability program
The code for the lab is also in appendix. The transient stability program determines the stability of the
power system below under different load condition and clearing time of a circuit breaker.

39
Figure 19. The Front panel of the running program for transient stability
The program allows the user to change the mechanical power output of the generator hence its
electrical power output and the critical clearing time of the circuit breakers at the buses.
The program plots a relation of angle against time. From the plot a conclusion of the system’s stability
can be made. If the graph doesn’t converge nor has a very large shift from its stability position then the
system is unstable, otherwise the system is stable.

40
Figure 20. An unstable system
Figure 21. A stable system

41
3.1 Machines Lab Design
The machines lab focuses on induction motor temperature protection using a PLC through a
variable speed drive.
Operational Description
Temperature sensor measures winding temperature of induction motor.
The PLC takes analogue temperature readings from the Temperature sensor via ADC
The PLC checks if the temperature reading is less than 60°C and if not, it switches the
motor off via a contactor or VSD
Motor can also be switched off using a local or remote computer
Equipment Layout
Below is the list of the equipment that male up the computer based lab
Computer
HMI
A.C Motor
Siemens LOGO 0BA7 PLC module
Temperature sensor (RT100 - analogue)
Analogue-Digital Converter
Power and Signal Cables
Contactor (24V) or AC/DC relay (240V output)
They relate to each other in the manner shown by the diagram

42
Component description
Computer:
The PLC programming language, Siemens LOGO! Soft Comfort is installed on the computer. Free
LOGO Soft Comfort download is available on the Siemens website although one needs a
registered version to be able to download the finished program designs to the PLC. Once the
software installation has been done, and then the desired PLC programs can be constructed,
which in this case was a motor temperature monitoring and switching system. The
programming involves combination of program blocks which do various functions, examples of
these include;
Inputs and Outputs: Digital, Analogue and Network
Basic Functions: AND, NOR, OR
Special Functions: Timers, Counters, Relays, etc
Data Logging Function, for recording process output and input data

43
Program Flowchart:
START
STOP
Read motor
parameters(temperat
ure)by PLC
Display motor parameters on
computer
Motor parameters =0o
C
Run ladder program
Is motor temperature>
70o
C
Update outputs
Is motor the motor
stopped?
Stop motor, trigger alarm for
operator
Figure 22. PLC program flow chart

44
Program description:
AI1 is where the program flow starts and it represents the analog input from the temperature
sensor into the PLC module.
B002 is an analogue amplifier for the analogue temperature values from the sensor with offset
at -50 and its parameters are shown in the dialogue box below
Figure 23. PLC program in LOGO! Soft Comfort Demo version

45
B003 is an analogue comparator and is used to compare two temperature inputs in case there’s
a value against which the motor temperature has to be measured in order to trigger the
protective system. Since this wasn’t important for this program, the second input was looped
using an analogue flag AM1 shown in the program

46
Q1 is a the digital output that is used to actuate the motor contactor depending on the
temperature value i.e if temperature reaches 70°C
L1 is the data logging command block which enables the PLC to record results
B006 is a message text block that enables the temperature output to be displayed.
BOO5 is an AND block that combines inputs from Q1 and L1, B007 as shown.
I1 represents a local digital input that acts as a switch to the motor through the contactor, and
is independent of the temperature value.
NI1 is a network input that allows remote devices such as computers, other PLCs and HMIs on
the PLC network to interact with the PLC module.
Q2 represents that arbitrary output from either I1 or NI1.
B007 and B009 are OR blocks that allow only one input to be received from more than one
possible output.
Q3 represents the final output from either Q1 or Q2 that is used to switch off the motor from
the contactor
Therefore the motor will automatically switch itself off if the temperature reaches 70°C but can
also be actuated using the remoter terminal network inputs and the local switch input.

47
The finished program can be simulated by pressing F3 in order to check for any errors and make
appropriate changes.
Once the programming is over, the program is downloaded onto the PLC module. This can be
done by use of a data card or Ethernet. Since it’s a lab, and we want to create a network the
Ethernet cable is used
PLC module
The PLC module is the heart of the whole system since it helps in implementing the control
program in order to achieve desired results.
Although there are many PLCs on the market, the Siemens LOGO! 0BA7 was the PLC module of
choice due to the following reasons
• Only readily available PLC module in Uganda
• It’s cheap
• Programming in LOGO! Soft Comfort is very easy, with practice
• Very efficient
• It has sufficient documentation
The Siemens LOGO! was designed as a micro automation module for industry for switching and
controlling and handles 24 digital and 8 analog inputs.
The logo control system is perfectly suited for small-scale automation projects and simplifies
design by replacing many time switches, counters and protective relays.

48
In this application, it controls through analog and digital inputs and outputs the varying load-
constant speed operation of an induction motor. Also, the PLC continuously monitors the inputs
and activates the outputs according to the control program.
This PLC system is of modular type composed of specific hardware building blocks (modules),
which plug directly into a proprietary bus: a central processor unit (CPU), a power supply unit,
input-output modules I/O, and a program terminal.
Such a modular approach has the advantage that the initial configuration can be expanded for
other future applications such as multi-machine systems or computer linking.
PLC module installation
The PLC module is mounted on a rail and screwed in place. It’s then connected to (12/24V |
0.8/2.0A) d.c power supply as shown below (note safety fuse)
Temperature sensor

49
Temperature Sensor Element (RT100) is used and provides an analogue output depending on
the measured temperature. The output is in form of a voltage level.
Figure 24. Temperature sensor
Sensor characteristics
Signal Status 0
Input current
< 5V d.c
< 1.0 mA
Signal Status 1
Input current
> 8V d.c
> 1.5 mA
It’s connected to the analog inputs on an expansion module as shown below

50
An expansion module with a grounded potential power supply is used. The sensor is connected
as shown above and since it’s a two wire connection, terminal M1+ and IC1 are short circuited
Analogue to Digital converter. (ADC)
This converts the analogue temperature readings from the temperature sensors to a digital format that
can be read by the PLC.
Induction motor.
Figure 25. an induction motor diagram
During thermal field analysis of the motor, the thermally critical parts of a motor are the stator windings
and the rotor cage.
Power requirements of the induction motor.
Voltage 380-415 V
Frequency 50Hz
Starting Current 9.1A
Velocity 1410 rpm
Power 4.0kW
Power factor 0.8 p.f.
Motor contactor connection to PLC
The motor’s speed drive/contactor/relay inputs are connected at the PLC outputs as shown
(max 16A). The PLC can also allow multiple loads to be connected.

51
Figure 26. Connection of variable speed drive to the outputs of the PLC
Human Machine Interface/ remote user
The PLC can support remote user inputs from a computer or HMI using Ethernet connection
The Network input can be from the LOGO! PLC that supports an Ethernet connection to a
remote PC running the LOGO!Soft Comfort programming software, Human Machine Interface
or other LOGO PLC modules.
Figure 27. An ethernet port on a PLC for network communication

52
One LOGO! 0BA7 can support up to 8 communication connections with other Siemens devices
via Ethernet. You can select the following communication parameters:
Other LOGO! 0BA7 controllers
PC running LOGO! Soft Comfort V7.0 programming software
HMI with Ethernet access
SIMATIC S7 controllers with Ethernet access
Addressing the devices
You need to ensure that all network settings have been made correctly for successful
communication to take place.
Read out the IP address of LOGO!. Change to the menu and select the item Network; IP
address. Here you set the required address.
Then configure the network connection of your PC. Select the respective connection in the
network connections (Start; Settings; Network connections). Open the properties, select the
Internet Protocol TCP/IP and open the properties. Assign an additional IP address and a subnet
mask that match the set LOGO! Addresses.

53
Chapter 4. Challenges, Conclusions and recommendations
4.1. Summary of results
The main aim of the project was to develop computer based power and machine labs. The power labs
were developed and samples of lab manuals are attached to the report whereas for the machines labs
due to the lack of funding only system requirements and designs were developed. These can be used to
develop the actual lab.
4.2. Challenges and limitations
LabVIEW Matlab and Formula script limitations such as
i. LabVIEW Matlab script cannot create executable programs so users cannot run this
program independently on their own computer as simple running programs.
ii. Formula node doesn’t work with matrices, and complex numbers
iii. LabVIEW matlab script doesn’t support sparse matrices so Gauss Siedel numerical
method was used in the stead of newton raphson.
The remote lab could only run in internet explorer as LabVIEW RTE was only compatible with
that.
Expensive industrial equipment as the budget of US 2300$ was made. This equipment was both
expensive to hire and buy. Some lenders were willing to lend the equipment for about US 250 $
a day.
All PLC software which was free required hardware to be in place. The unlicensed PLC software
could not allow for PLC hardware simulations.
There’s no online java support for Siemens LOGO, hence program has to be directly installed on
computers
4.3. Recommendations
I recommend that the college purchases industrial automation equipment such as PLCs, VSDs etc. to
affectively enable student to
Learn PLC programming
Do other projects in industrial automation

54
References
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Approach. Kuwait: ublic Authority for Applied Education and Training (PAAET), KUWAIT.
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Motor Protection.
[4] By Hossein Seifi, M. S. (2011). Electric Power System Planning: Issues, Algorithms and Solutions.
London: Springer.
[5] Cory, B. W. (4th Edition). Electric Power Systems. . John Wiley and Sons. .
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Distribution Networks. K.N. Toosi University of Technology, Electrical Engineering Department,
Tehran-IRAN.
[13]Grainger, J. J. (Copy right 1994). Power System Analysis. McGraw-Hill Book.
[14]Hans-PetterHalvorsen. ( 2011). LabVIEWMathScript Tutorial. . Telemark University College,
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[18]Instrument, N. (2012, April 4th ). Developing Algorithms Using LabVIEW MathScript. Retrieved
April 4th, 2012, from Developing Algorithms Using LabVIEW MathScript:
http://www.ni.com/mathscript
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Algorithms Using LabVIEW MathScript.

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[20]Instruments, N. (2012, April 19th). Retrieved April 19th, 2012, from
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[21]Instruments, N. (2012, April 19th). Building Advanced User Interfaces in LabVIEW. Retrieved
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[22]Instruments, N. (2012, April 19th). Building Advanced User Interfaces in LabVIEW. Retrieved
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[23]Instruments, N. (2012, April 19th). LabVIEW User Interface Gallery. Retrieved April 19, 2012,
from http://zone.ni.com/devzone/cda/tut/p/id/3587
[24]J.G.Vlachogiannis. (2001.). Fuzzy Logic application in load flow studies. IEE.
[25]James Momoh, L. M. (Copyright 2010). Economic Market Design and Planning for Electric Power
Systems. wiley, IEEE.
[26]Jurgen Schlabbach, U. o.-H. (2008). Power system Engineering. Planning Desgin and operation of
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Using Sensors. IEEE.
[34]Shehryar Humayun, M. M. (2012, February). Developing a LabVIEW and MATLAB-based Test Bed
for Data Acquisition, Analysis and Calibration of Frequency Generators over GPIB. International
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[35]Smarajit Ghosh, K. S. (2008). An Efficient Method for Load−Flow Solution of Radial Distribution
Networks . World Academy of Science, Engineering and Technology .
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[37]Theodore, W. (5th Edition). Electrical Machines, Drives and Power Systems. Prentice Hall.
[38]Variable Frequency Drive, Energy Efficiency Reference Guide. (n.d.). natural Resources Canada.

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[39]wikipedia. (2012, ApriL 12). Retrieved April 12th, 2012, from
http://en.wikipedia.org/wiki/Eagle_%28program%29
[40]Wikipedia. (2012). Heun's Method. Retrieved May 3rd, 2012, from en Wikipedia:
https://en.wikipedia.org/wiki/Heun%27s_method
[41]Wikipedia. (n.d.). Wikipedia ,The Free Encyclopedia. Retrieved May 4th, 2012, from Adjustable-
Speed_drive: http://en.wikipedia.org/wiki/Adjustable-speed_drive
[42]Wildi, T. (5th Edition). Electric Machines,Drives and Power Systems. Prentice Hall.
[43]XIA, C. H. (n.d.). Neural Network Models and Design of Virtual Instrument Based on Joint
Programming of Labview and MATLAB for short term Load forecasting of Electric Power system.
China Three Gorges University, College of Electrical Engineering and Information Technology.
[44]Yao, X. (1995). A new simulated annealing algorithm’. International Journal of Computer, pp 161-
168.
[45]Zimmerman, G. P. (April 2008). Programmic Logic Controllers and Ladder Programming. South
Dakota School of Mines and Technology, Department of Humanities.

57
Appendix I: Budget and Code
Budget for the Project
Table 2. Project Bugdet
COMPUTER BASED POWER AND MACHINES LAB PROJECT BUDGET
HARDWARE REQUIREMENTS
DEVICE
QUANTIT
Y PRICE (USD) Total (USD)
Computers 3 320.00 960.00
PLC Module 1 240.00 240.00
Variable Speed Drive 1 320.00
Interfacing cables 1 160.00
Data Cards 1
Available from
ilabs
Power supply unit 1 80.00
Temperature sensors 72.00 72.00
Motor 1 160.00 160.00
SOFTWARE
REQUIREMENTS
PACKAGE
MATLAB/Simulink 1 Available -
Powersim 1 Available -
LabView 1 Available -
LOGO!Soft Comfort 1 240.00 240.00
php designer 1 Available -
OPERATIONAL
REQUIREMENTS
Expense type
Transport Costs lumpsum 100 100.00
Stationery costs lumpsum 40 40.00
Equipment Layout Room To be availabled -
AirtIme lumpsum 20 20.00
TOTAL COST
2,392.00

58
Flow charts
Flow chart for load flow

59
Matlab script code
Load flow: Radial power system
%This program calculates the Voltages and phase angles at two busbars in apower system.
%These are the base voltages of the three regions of the power system.
Vb1=11e3,Vb2=133e3,Vb3=33e3,Vb4=0.415e3;
%Calculation of base Currents
Ib1=Sb/(sqrt(3)*Vb1);
%Calcalation of base impedances
Zb1=Vb1*Vb1/Sb;
Zb2=Vb2*Vb2/Sb;
Zb3=Vb3*Vb3/Sb;
Zb4=Vb4*Vb4 /Sb;
%Per unit impedendace for the respective power systems component
zt1=0.1334*i ; Zt2=1.08*i; Zt3=0.0002*i; Z1=0.00148+ 0.00289*i;Z2=0.01093+0.0102*i; Zg = 0.0124;
%Assumption is Bus 1 is the Slack bus with 1V p.u
V1=1;
%Zt is the per unit impendance after the generator but before the industrial load
Zt=zt1+Z1+Zt2+Zg;
%Zm is the per unit impedance after the industrial load but before the domestic load
Zm=Z2+Zt3;
%Assume Sin industriial load base MVAand Sd is domestic load base MVA
Sin;Sd;%The perunit power outputs at the Buses
P2=(Sin*pf2)/Sb;
Q2=(Sin*sin(acos(pf2)))/Sb;
P3=(Sd*pf3)/Sb;
Q3=(Sd*sin(acos(pf3)))/Sb;
L2=P2+i*Q2;
L3=P3+i*Q3;
%The currents drawn by the domestic and industrial loads in p.u
I1=Sin/(sqrt(3)*Vi);
Iin=I1 * (pf2-i* sin(acos(pf2)))/Ib3;
I2=Sd/(sqrt(3)*Vi);
Id=I2 * (pf3-i* sin(acos(pf3)))/Ib4;
%From Kirchoff's Current law It is the pu current from the generator
It=Iin+Id;
V2pu=(V1-It*Zt);
V3pu=(V2pu-Id*Zm);

60
V2=V2pu*Vb3;
V3=V3pu*Vb4;
%Percentage Voltage drops from the ideal.
perc2=(1-abs(V2)/Vb3)*100;
perc3=(1-abs(V3)/Vb4)*100;
Pl1=real(Z1)*(abs(It))^2*Sb;
Pl2=real(Z2)*(abs(Id))^2*Sb;
Load flow: ring power system
%this program carries out load flow analysis on the meshed power system of interest
% using Gauss Siedel Method
% 1 - Slack Bus..2 - PV Bus.. 3 - PQ Bus..
% Bus data for Load Flow Analysis.
fb = linedata(:,1); % From bus number
tb = linedata(:,2); % To bus number
r = linedata(:,3); % Resistance, R
x = linedata(:,4); % Reactance, X
b = linedata(:,5); % Ground Admittance, B/2
z = r + i*x; % Z matrix
y = 1./z; % To get inverse of each element
b = i*b; % Make B imaginary
nbus = max(max(fb),max(tb)); % no. of buses
nbranch = length(fb); % no. of branches
ybus = zeros(nbus,nbus); % Initialise YBus
% Formation of the Off Diagonal Elements...
for k=1:nbranch
ybus(fb(k),tb(k)) = -y(k);
ybus(tb(k),fb(k)) = ybus(fb(k),tb(k));
end
% Formation of Diagonal Elements....
for m=1:nbus
for n=1:nbranch
if fb(n) == m || tb(n) == m
ybus(m,m) = ybus(m,m) + y(n) + b(n);
end
end
end
ybus; % Bus Admittance Matrix
zbus = inv(ybus); % Bus Impedance Matrix
% Assumption, Bus 1 is considered as Slack bus.
bus = busdata(:,1); % Bus number.

61
type = busdata(:,2); % Type of Bus 1-Slack, 2-PV, 3-PQ.
V = busdata(:,3); % Initial Bus Voltages.
th = busdata(:,4); % Initial Bus Voltage Angles.
GenMW = busdata(:,5); % PGi, Real Power injected into the buses.
GenMVAR = busdata(:,6); % QGi, Reactive Power injected into the buses.
LoadMW = busdata(:,7); % PLi, Real Power Drawn from the buses.
LoadMVAR = busdata(:,8); % QLi, Reactive Power Drawn from the buses.
Qmin = busdata(:,9); % Minimum Reactive Power Limit
Qmax = busdata(:,10); % Maximum Reactive Power Limit
nbus = max(bus); % To get no. of buses
P = GenMW - LoadMW; % Pi = PGi - PLi, Real Power at the buses.
Q = GenMVAR - LoadMVAR; % Qi = QGi - QLi, Reactive Power at the buses.
Vprev = V;
toler = 1; % Tolerence.
iteration = 1; % iteration starting
while (toler > 0.00001) % Start of while loop
for c = 2:nbus
sumyv = 0;
for k = 1:nbus
if c ~= k
sumyv = sumyv + ybus(c,k)* V(k); % Vk * Yik
end
end
if type(c) == 2 % Computing Qi for PV bus
Q(c) = -imag(conj(V(c))*(sumyv + ybus(c,c)*V(c)));
if (Q(c) > Qmax(c)) || (Q(c) < Qmin(c)) % Checking for Qi Violation.
if Q(c) < Qmin(c) % Whether violated the lower limit.
Q(c) = Qmin(c);
else % No, violated the upper limit.
Q(c) = Qmax(c);
end
type(c) = 3; % If Violated, change PV bus to PQ bus.
end
end
V(c) = (1/ybus(c,c))*((P(c)-i*Q(c))/conj(V(c)) - sumyv); % Compute Bus Voltages.
if type(c) == 2 % For PV Buses, Voltage Magnitude remains same, but Angle changes.
V(c) ;
end
end
iteration = iteration + 1; % Increment iteration count.
toler = max(abs(abs(V) - abs(Vprev))); % Calculate tolerance.

62
Vprev = V; % Vprev is required for next iteration, V(i) = pol2rect(abs(Vprev(i)), angle(V(i)));
end % End of while loop / Iteration
iteration; % Total iterations.
V; % Bus Voltages in Complex form.
Vmag = abs(V) % Final Bus Voltages.
Ang = 180/pi*angle(V) % Final Bus Voltage Angles in Degree.
Transient stability
t=0 ; % initiating time
tf=0 ;
tfinal=4 ; % time end
tstep=0.001; % incremental time change
n=(tfinal-t)/tstep;
f=50; % frequency
H=2.52;M=H/(180*f) ; % contant of inertia
i=1;
E=1.2;V=1; % internal generator emf and terminal emf
x1=0.112;x2=0.223;x3=0.30; % reactances between different buses
x4=x1+x2+x3;
Pmaxbf=E*V/(x4); % maximum power before fault
delta=asin(Pm/Pmaxbf); % angle in radians
ddelta=0; % initiating angle to zero radians
time(1)=0;
ang(1)=delta;
time(1)=0 ;
switch m % m is the bus on which the fault occurs
case 1
x=x1;
Pmaxdf=V*E/x;
case 2
x=x1+x2;
Pmaxdf=V*E/x;
case 3
x=x1+x2+x3;
Pmaxdf=V*E/x;
end
Pmaxaf=2.00 ; % power after the fault
while t<tfinal, % iterations in relation to time
if (t==tf),
Paminus=Pm-Pmaxbf*sin(delta) ;

63
Paplus=Pm-Pmaxdf*sin(delta) ;
Paav=(Paminus+Paplus)/2 ;
Pa=Paav ;
end
if (t==tc),
Paminus=Pm-Pmaxdf*sin(delta) ;
Paplus=Pm-Pmaxaf*sin(delta) ;
Paav=(Paminus+Paplus)/2;
Pa=Paav;
end
if(t>tf && t<tc),
Pa=Pm-Pmaxdf*sin(delta) ;
end
if(t>tc),
Pa=Pm-Pmaxaf*sin(delta) ;
end
ddelta=ddelta+(tstep*tstep*Pa/M) ;
delta=(delta*180/pi+ddelta)*pi/180;
deltadeg=delta*180/pi ;
t=t+tstep ;
time(i)=t;
ang(i)=deltadeg ;
i=i+1 ;
end

64
Appendix II:Labs
Appendix II: Experiment 1- load flow analysis
Experiment Objective
In this experiment, you will determine the voltage level, phase angle at different buses in the power
system; and the real power losses in the transmission lines.
Experiment Requirements
Local Requirements:
A Networked computer with LabVIEW RTE
Internet explorer
Remote Requirements:
Computer with at least P.4 or better
LABVIEW Programming environment
Matlab 2011 (a or b) or 2012
Part 1
Theory
In power system load flow studies numerical method are used to determine the bus voltages and phase
angles. The numerical method of interest in this experiment is the Gauss siedel method. Gauss-Seidel
method is also known as the method of successive displacements. To illustrate the technique, consider
the solution of the nonlinear equation given by
Above function is rearranged and written as
If x=(k) is an initial estimate of the variable x, the following iterative sequence is formed

65
A solution is obtained when the difference between the absolute value of the successive iteration is
less than a specified accuracy, i.e.
Where ε is the desire accuracy
The process is repeated until the change in variable is within the desired accuracy. So the Gauss-Seidel
method needs much iteration to achieve the desired accuracy, and there is no guarantee for the
convergence.
Procedure
The circuit for the power system is represented by the diagram below.
Figure 28. The ring power system
i. On a networked computer, check whether LabVIEW RTE is installed. If it’s not installed go to
http://digital.ni.com/public.nsf/ad0f282819902a1986256f79005462b1/151be12c055f57ce8625
7043006cb4b3/$FILE/Windows%20RFP%20Plugins.zip

66
ii. Open internet explorer, browse to http://10.0.2.37/power_lab1.1 . This is the URL for accessing
the Lab client.
iii. From the power system diagram computer the per unit impedances for the generators,
transformer, and transmission lines. (Use a base MVA of 10.)
iv. Enter the values to the corresponding line data field.
v. Change all the values of Qmax to 1 and Qmin to -1 in the bus data field.
vi. Considering loads of 5, 8, and 9 MW; 1, 2 and 4MVAr for loads 1, 2 and 3 respectively, compute
the per unit power and enter them in the bus data field.
vii. Execute the program.
Questions
1. Of what importance are load flow studies in power systems planning?
2. What other numerical methods are used to carry out load flow analysis of power systems?
Compare these methods with Gauss Siedel.
3. Draw the single line diagram of the above power system and carry out load flow numerical
analysis of the power system using newton Raphson.
4. Compare your results
5. Comment on your results

67
Part two.
Theory.
Load flow studies for radial power systems are not carried using numerical method rather KCL is used.
In this second part of the lab you are to carry out load flow studies for a radial power system below.
Procedure
i. On a networked computer, check whether LabVIEW RTE is installed. If it’s not installed go to
http://digital.ni.com/public.nsf/ad0f282819902a1986256f79005462b1/151be12c055f57ce8625
7043006cb4b3/$FILE/Windows%20RFP%20Plugins.zip
ii. Open internet explorer, browse to http://10.0.2.37/power_lab1.2. This is the URL for accessing
the Lab client.
iii. Change the power factor of the industrial load to 0.85 and the that of the domestic load to 0.90.
iv. Change the VA of the industrial and domestic load to
10,000 and 6,000
2000 and 1000

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