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PSZ 19:16 (Pind. 1/07)

DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT

MOHD AZMI B MOHD RAZALI Author’s full name :

5 OCTOBER 1987 Date of birth :

CONTINGENCY ANALYSIS FOR POWER TRANSMISSION Title :

SECURITY.

2009/2010 Academic Session:

I declare that this thesis is classified as :

I acknowledged that Universiti Teknologi Malaysia reserves the right as follows :

1. The thesis is the property of Universiti Teknologi Malaysia.

2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose

of research only.

3. The Library has the right to make copies of the thesis for academic exchange.

Certified by :

SIGNATURE SIGNATURE OF SUPERVISOR

871005-03-5055 DR MD PAUZI B. ABDULLAH

(NEW IC NO. /PASSPORT NO.) NAME OF SUPERVISOR

Date : 26 APRIL 2010 Date : 26 APRIL 2010

NOTES : * If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the letter from

the organisation with period and reasons for confidentiality or restriction.

UNIVERSITI TEKNOLOGI MALAYSIA

CONFIDENTIAL (Contains confidential information under the Official Secret

Act 1972)*

RESTRICTED (Contains restricted information as specified by the

organisation where research was done)*

OPEN ACCESS I agree that my thesis to be published as online open access

(full text)

“Here, I declare that I have read this project report and in my opinion it is fully

adequate in terms of scope and quality in part fulfillment of the requirement for the

Bachelor’s Degree of Electrical Engineering (Power).”

Signature : ………………………

Supervisor : DR MD PAUZI B ABDULLAH

Date : 26 APRIL 2010

CONTINGENCY ANALYSIS FOR POWER TRANSMISSION SECURITY

MOHD AZMI B MOHD RAZALI

Submitted to the Faculty of Electrical Engineering

in partial fulfillment of the requirement for the degree of

Bachelor in Electrical Engineering (Power)

Faculty of Electrical Engineering

Universiti Teknologi Malaysia

APRIL 2010

ii

I declare that this thesis entitled “ Contingency Analysis for Power Transmission

Security “ is the result of my own research except as cited in the references. The thesis

has not been accepted for any degree and is not concurrently submitted in candidature of

any other degree.

Signature : ....................................................

Name : MOHD AZMI B MOHD RAZALI

Date : 26 APRIL 2010

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To my beloved mother and father

iv

ACKNOWLEDGEMENT

Alhamdulillah, with Allah S.W.T blessing, praise to Almighty Allah S.W.T for

without his guidance I will not been able to complete my Final Year Project. Peace

and blessing to Prophet Rasullallah S.A.W who has bring the light to all mankind.

I would like to thank and express my deepest gratitude to my intelligent

supervisor Dr Md. Pauzi B. Abdullah that has guided me from the beginning of the

Project, until it is completed. Without his help, support and guidance, I will not be

able to complete my final year project and also my thesis.

Special thanks to my mom, my father and my dear family, you all my main

drive to strive in life. Thanks for everything mom. Thankfulness also for my special

love, Nor Faiza Bt Ahmad Jasman for give support, encouragement, inspiration and

understanding me.

I also like to thank all of my friends for their support and encouragement

throughout conducting this project. Thanks for sharing the knowledge and

information that I needed for my project.

Finally, I would like to thank those who give me helps direct or indirectly

towards successfully completing this project. May God bless all of you for your

kindness.

v

ABSTRACT

Power system security must be concern all the time to ensure that the system

always operate in a good condition. To make sure that the system operates in a good

condition, security assessment must be done on the system. There is many ways to

assess the security of the power system. One of the ways is to make sure that there is

no problem occurs at the transmission line such as power overload when one of the

transmission lines out. If there is a power overload in the system, contingency

analysis must be done on the system to secure back the system. To secure back the

system, transmission line in the system must be rank first according to its severity

using appropriate formula. This is because there are many transmission lines in the

system, only the most severe line only will be focused when come to the analysis

part. In this project, Power World software is used for the analysis and a modified

IEEE 14-bus system is used as the test system. This project only concern about the

transmission line in the system. In this project also only study about the method to

ranking the transmission line in the system. Transmission line in the system was

ranked by using the MW performance index formula.

vi

ABSTRAK

Keselamatan sistem kuasa perlu di titik beratkan pada setiap masa untuk

memastikan sistem beroperasi dalam keadaan yg baik. Untuk memastikan sistem

sentiasa beroperasi dalam keadaan yg baik, penilaian keselamatan sistem perlu

dilakukan. Terdapat banyak cara untuk menilai keselamatan sistem. Salah satu cara

adalah dengan memastikan tiada kuasa berlebihan di dalam talian penghantaran

apabila satu talian mengalami kerosakan. Jika terdapat kuasa berlebihan di dalam

talian, analisis luar jangkaan perlu dilakukan untuk mengembalikan kestabilan pada

sistem. Untuk mengembalikan kestabilan pada sistem, kesemua talian penghantaran

dalam sistem perlu dikelaskan mengikut tahap kerosakan. Ini adalah penting kerana

terdapat banyak talian penghantaran dalam sistem, jadi fokus hanya pada talian

penghantaran yg mempunyai kerosakan yg tinggi untuk di analisis. Dalam projek ini,

sistem ubah suai IEEE 14-palang di uji dengan menggunakan perisian Power World.

Projek ini hanyala menitik beratkan talian penghantaran dalam sistem. Dalam projek

ini juga hanya mempelajari cara-cara untuk mengkelaskan talian penghantaran

mengikut tahap kerosakan dalam sistem. Talian penghantaran telah dikelaskan

dengan menggunakan formula MW prestasi index.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION OF THESIS ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xiii

LIST OF APPENDICES xiv

1 INTRODUCTION

1.1 Background of study 1

1.2 Problem statement 2

1.3 Objectives of the project 3

viii

1.4 Scope of the project 3

2 LITERATURE REVIEW

2.1 Power system security 4

2.2 Contingency analysis 5

2.3 Distribution factor and performance

Indices 6

2.3.1 Contingency analysis using linear

sensitivity factors 6

2.3.2 Distribution factors 7

2.3.3 Line outage distribution factor

(LODF) 7

2.3.4 MW performance index 8

2.4 Method from previous research 9

2.4.1 Automatic Contingency Selection

And Ranking Using An Analytic

Hierarchical Process By Jizhong Zhu 9

2.4.2 Line Flow Contingency Selection And

Ranking Using Cascade Neural

Network By Rajendra Singh 9

2.4.3 Transmission Losses Based MW

Contingency Ranking By Aydogan

Ozdemir 10

3 METHODOLOGY

3.1 Introduction 11

3.2 IEEE 14-bus system 13

3.3 Simulate the system using Power

ix

World software 14

3.4 Modified IEEE 14-bus system 15

4 RESULT AND DISCUSSION

4.1 introduction 17

4.2 Analyzing the test system 18

4.3 Percentage of power flow over the

limit in transmission line 19

4.4 MW performance index method 20

4.5 Calculating MW performance index 21

4.6 Graph MW performance index versus

Line out using data in table 4.5.2 24

4.7 Comparison between the results of the line

ranking (due to the percentage of power flow

over the limit in line) with the result of the

line ranking using the performance index

PIMW formula due to its severity 29

4.8 Summary 30

5 CONCLUSION AND RECOMMENDATION

5.1 Conclusion 31

5.2 Recommendation 32

REFERENCES 33

APPENDICES 35

x

LIST OF TABLES

TABLE NO. TITLE PAGE

4.3.1 Percentage of line over limit 19

4.4.1 Power flow in each line (MW) when

one line out 20

4.5.2 Ranking using MW performance index

Formula 23

4.7.1 Final ranking 29

xi

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.4.1 Transmission line 3

3.1.1 Flow chart of the methodology 12

3.2.1 IEEE 14-bus system 13

3.3.1 Mainframe of the power world software 14

3.4.1 Modified IEEE 14-bus system 15

4.2.1 12-bus system 18

4.6.1 Graph MW performance index versus

line out for n=1 24


line out for n=2 25


line out for n=3 26


line out for n=4 27

xii


line out for n=5 28

xiii

LIST OF SYMBOLS

Pl - The mw flow of line l

- The mw capacity of line l

NL - The number of lines of the system

Wli - Real non-negative weighting factor

n - Exponent of penalty function.

P - Power

V - Voltage

xiv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Parameters of the IEEE 14-bus system 35

B Parameters of the 12-bus system 39

C Getting started with a Power World

Simulator 41

CHAPTER 1

INTRODUCTION

1.1 Background of study

Security Assessment is a term used to describe the process of ensuring system

operating security. Typically, power systems operating in an N-1 condition are

considered secure. N-1 means that the system will remain in a secure operating state

if any single event or failure occurs. In a secure state all system parameters are

operating as desired with all voltages within their specified limits, no power lines

overloaded, all loads on line and being provided with power.

Modern power systems are often operated near capacity. During periods of

peak demand, power lines may be loaded to near capacity. Operating a power system

near capacity requires quick response by operators in the event of an unexpected

change in the system operating configuration. Rapid security assessment is needed in

order for the system to continue to operate normally when contingencies occur.

As the demand for power increases, existing power grids are being more

frequently loaded nearly to capacity. As a result, system operators must rapidly

2

respond to sudden or unexpected changes in the systems operating configuration. For

example, wind or lightning may suddenly damage power lines taking them out of

service. When contingencies occur, operators must rapidly assess and reconfigure

systems if a normal operating state is to be maintained.

Because rapid assessment is becoming increasingly important, expert systems

have been developed to assist operators in making decisions regarding security

assessment. When sudden changes occur, there may not be sufficient time for

operators to run numerous power flow scenarios. This is where an expert system can

be very helpful.

An expert system is a computer system that can behave like an expert. In this

case, the system will behave like a power system expert. In the event of a failure or

sudden change, the expert system can rapidly assess the power system operating

condition and provide the operators with a weighted list that indicates which power

lines in a network are most critically loaded and which is least critically loaded using

knowledge based approach. This greatly reduces the operators work load and can

vastly improve response time. The end result is improved system reliability.

1.2 Problem Statement

In case of a line failure, bus voltages and currents change due to the

modification in the grid topology. In order to find these altered voltages and currents,

generally, the entire load flow calculations have to be redone. The method that will

be used to identify and ranking which line is the most severe is MW performance

index (PIMW). This is what we call it contingency analysis.

3

1.3 Objectives of the project

i. To study power system security assessment for transmission line.

ii. To study MW different performance index (PIMW) in determining

critical contingencies.

iii. To develop a modified IEEE-14 bus system model by using Power

World software for security analysis.

iv. To compare MW different performance index (PIMW) by using a

modified IEEE 14-bus system.

1.4 Scope of the project

In this project only concentrate on MW line limit and voltage limits are

neglected. For this project, a modified IEEE-14 bus system will be used as a test

system. The system will be test and run by using Power World software. In this

project, it is assumed that contingency only occur at one line at a time.

Figure 1.4.1: transmission line

CHAPTER 2

LITERATURE REVIEW

2.1 Power system security[2]

The security of a power system is measured by the ability of the system to

withstand contingency cases without violating normal operating conditions. The

conditions to be monitored are generally the MW flow on each branch and voltage

on each bus. One reliable way of testing the impact of a contingency case on a power

system is to simulate the situation by a power flow solution. Due to the huge number

of contingency cases to be analyzed, it is infeasible to simulate each case in detail by

full AC solution. The most accepted approach is to deal with the problem in two

steps; contingency selection and contingency analysis. In contingency selection, a

fast screening method is applied to select the most severe contingency cases or to

rank all the cases according to their severities. In contingency analysis, detailed

power flow studies are applied to only the potential critical cases. Contingency

screening is performed using distribution factors approach. Distribution factors are

widely used in real-time contingency ranking owing to the speed with which this

analysis can be performed once these factors are evaluated and stored. This is

5

followed by contingency analysis, which is performed on the potentially critical

cases.

2.2 Contingency Analysis[2]

Contingency evaluation is one of the most important tasks encountered by

planning and operation engineers of bulk power systems. In the planning stage,

contingency analysis is used to examine the performance of a power system and the

need for new transmission expansion due to load growth or generation expansion. In

the operation stage, contingency analysis assists engineers to operate the power

system at a secure operating point, where equipment are loaded within their safe

limits and power is delivered to customers with acceptable quality standards.

In general, the state of a power system is determined based on its ability to

meet the expected demand under different contingency levels. In this type of

analysis, the objective is to find overloads or voltage violations under such

contingencies and the proper measures that are needed to alleviate these violations.

Identification of these contingencies and determination of the corrective actions often

involve exhaustive load flow calculations. Contingency analysis is an important

aspect of power system security assessment. As various probable outages compose a

‘contingency-set’, some cases in the contingency-set may lead to transmission line

over loads or bus voltage limit violations during power system operations. Such

critical contingencies should be quickly identified for further detailed evaluation or,

where possible, corrective measures taken. The process of identifying these critical

contingencies is referred to as “contingency selection”. The traditional procedure of

contingency selection is based on the results of a full AC load flow solution. In order

to cope with the computational burden, current practice is to perform contingency

analysis in two phases: contingency selection (or screening) and contingency

evaluation. In the contingency selection phase, the original list of contingencies is

screened to a shorter list by eliminating large number of cases expected to have no

violation. In the contingency evaluation phase, full ac power flow analysis is

6

performed on the potentially severe cases selected by the contingency selection

phase.

2.3 Distribution factors and performance indices[2]

The security of a power system is measured by the ability of the system to

withstand contingency cases without violating normal operating conditions. The

conditions to be monitored are generally the MW flow on each branch and voltage

on each bus. One reliable way of testing the impact of a contingency case on a power

system is to simulate the situation by a power flow solution. Due to the huge number

of contingency cases to be analyzed, it is infeasible to simulate each case in detail by

full AC solution. The most accepted approach now is to deal with the problem in two

steps; contingency selection and contingency analysis. In contingency selection, a

fast screening method is applied to select the most severe contingency cases or to

rank all the cases according to their severities. In contingency analysis, detailed

power flow studies are applied to only the potential critical cases.

2.3.1 Contingency analysis using linear sensitivity factors[2]

This method can be used to prepare the list of “critical” cases from a set of

cases. Hence the non-violated cases can be eliminated. For many systems DC load

flow models provides adequate capability. DC load flow provides sufficient accuracy

with respect to the real power (megawatt) flows. Hence DC power flow is used to

prepare the set of critical cases using the linear sensitivity factors. Performance index

(PI) is then calculated to quantify the severity of the contingency. Ranking is given

based on the PI value. Hence the critical cases list is prepared on the ranking of the

contingencies. Full AC power flow can then be run on the critical cases.

7

2.3.2 Distribution factors[2]

The distribution factors approach has long been adopted by many utilities as

means of simulating a large number of contingencies. The method is known to be a

useful approximation. For a system with K contingencies and M monitored branch

flows, an ‘M × K’ array of distribution factors has to be computed. This computation

is time consuming and is usually performed off-line. The factors need to be

computed only after every topology change, which is less frequent than the actual

simulation interval; the speed with which it can perform the simulation is quite fast.

2.3.3 Line outage distribution factors (LODF)[1]

The line outage distribution factors are only applied to the testing for

overloads transmission circuit are lost. By definition, the line outage distribution

factor has the following meaning:

,

where:

= line outage distribution factor when monitoring line l after an outage on line k.

= change in MW flow on line l.

= original flow on line k before it was outage (opened).

If one knows the power on line l and line k, the flow on line l with line k out

can be determined using ‘d’ factors.

8

Where:

= flow on line l with line k out.

, =preoutage flow on lines l and k, respectively.

By precalculating the line outage distribution factors, a very fast procedure

can be set up to test all lines in the network for overload for the outage of a particular

line.

2.3.4 MW performance index (PIMW)[2]

An index for quantifying the extent of line overloads may be defined in terms

of MW performance index:

where Pl, the mw flow of line 1; , the mw capacity of line l; NL, the number of

lines of the system; Wli, real non-negative weighting factor (= 1); n, exponent of

penalty function.

The performance index PIMW contains all line flows normalized by their

limits. These normalized flows are raised to an even power (by setting n = 1,2,….)

thus, the use of absolute magnitude of flows is avoided. This index PIMW has a

small value, when all line flows are within their limits and a high value when there

are lines overloads.

9

2.4 Method from the previous research

2.4.1 Automatic Contingency Selection And Ranking Using An Analytic

Hierarchical Process By Jizhong Zhu[8]

A new approach in the power system analysis to automatic contingency

selection (ACS) and ranking, using an analytic hierarchical process (AHP) is

developed. ACS for the real and reactive power subproblems is solved by network

flow programming, based on the existence of weak coupling between real and

reactive quantities in power systems. The performance indices to assess the severity

of contingencies are defined as the total real and reactive load to be curtailed. In the

rank calculation, this paper takes into consideration the relative importance of

transmission lines and the situation that the real and reactive power security

constraints may be violated as the line outage appears, so that the precise information

for the real time security analysis can be provided. The results on IEEE-14 bus test

system are given in the paper.

2.4.2 Line Flow Contingency Selection And Ranking Using Cascade Neural

Network By Rajendra Singh[9]

Line flow or real-power contingency selection and ranking is performed to

choose the contingencies that cause the worst overloading problems. In this paper, a

cascade neural network-based approach is proposed for fast line flow contingency

selection and ranking. The developed cascade neural network is a combination of a

filter module and a ranking module. All the contingency cases are applied to the filter

module, which is trained to classify them either in critical contingency class or in

non-critical contingency class using a modified BP algorithm. The screened critical

contingencies are passed to the ranking module (four-layered feed-forward artificial

neural network (ANN)) for their further ranking. Effectiveness of the proposed

ANN-based method is demonstrated by applying it for contingency screening and

10

ranking at different loading conditions for IEEE 14-bus system. Once trained, the

cascade neural network gives fast and accurate screening and ranking for unknown

patterns and is found to be suitable for on-line applications at energy management

centre.

2.4.3 Transmission Losses Based MW Contingency Ranking By Aydogan

Ozdemir[10]

Contingency ranking and selection is an indispensable tool for static security

analysis. Several performance indices suffer either from misranking or computational

inefficiencies. This paper presents a new performance index for MW line flow

contingency selection and ranking. The proposed index is derived from real power

transmission losses. It is a quadratic function of bus voltage angles and can easily be

calculated from real power flows or DC load flow. It improves both the selectivity

and the ranking of second order performance index without excessive computational

effort. The proposed method is tested on IEEE 24-bus reliability test system and

IEEE 30-bus test system. The results are compared with those of the conventional

second order performance index and of the tenth order reference performance index

from the point of ranking and selectivity.

11

CHAPTER 3

METHODOLOGY

3.1 Introduction

Before conducting the project, methodology of the project must be plan to

make sure that the project running smoothly. Figure 3.1.1 show the steps in doing

this project.

Study the concept of security in power system

Study how to use MW performance index formula

Choose reference system

Modified the system

Running the system

12

Analyzed the system

Figure 3.1.1: flow chart of the methodology

Figure 3.1.1 show the flow chart of the methodology. First of all I have to

study about the concept of the security in power system. Before conducting this

project, I have to study about the concept of the security in power system and

understand it to get a good result at the end of this project. The concept of the

security in power system has been discussed in literature review part.

Secondly I have to study how to use MW performance index (PIMW) formula.

Actually there were many people who had done the same project before but using

different method to rank the severity of the line. All of their technical reports also

had been published in several websites such as IEEE Xplore, Google Patent and US

Patent and science direct. The files are free to be downloaded from Google Patent

and US Patent. While for IEEE Xplore, user needs to be registered before being

allowed to view the full text files. It means that users are required to join the

organization and of course certain amount for their annual member fee is necessary.

For my project, I use MW performance index (PIMW) method to rank the severity of

the line. This method has been discussed earlier in literature review part (2.3.4) about

how to use this formula. This formula must be study and understand it first to get a

good result.

Third step I have to chose the reference system. In this project, I use IEEE

14-bus system as a reference. From the IEEE 14-bus system, I modified it because

power world software student version only limited to 13 buses only. After created the

modified system, I have run the system using the Power World software (student

version). Finally I have analyzed the tested system.

13

3.2 IEEE 14-bus system

For this project, IEEE 14-bus system is chosen for the case studies. The

original system consist of two generators, three synchronous compensators, eleven

loads, three transformer, 14 buses, fifth teen lines. The system is shown in figure

3.2.1:

.

Figure 3.2.1: IEEE 14-bus system

Parameters for this system are as in appendix A.

14

3.3 Simulate the System Using Power World Software (student version)

After choosing the system, I will simulate the system by using this software.

Power World Simulator is an interactive power systems simulation package designed

to simulate high voltage power systems operation on a time frame ranging from

several minutes to several days. The software contains a highly effective power flow

analysis package capable of efficiently solving systems with up to 100,000 buses but

for student version, it is limited to systems with 13 buses maximum only. By using

Power World software, I can do contingency analysis of the modified system that I

have created. Figure 3.3.1 shows the mainframe of the power world software:

Figure 3.3.1: mainframe of the power world software

15

3.4 Modified IEEE 14-bus system

Due to restrictions in the Power World (student version) the original system

has been modified. By using this software, I have created 12-bus system. Figure

3.4.1 shows the modified system that I have designed. From the figure 3.4.1, if

compared to the system below with actual IEEE 14-bus system, it can be seen that I

have take out bus 7 and bus 8 to complete this modified system. I also have taken out

the transformer between bus 5 and bus 6 and transformer between bus 4 and 9. I

replace the transformer with the transmission line. :

Figure 3.4.1: Modified IEEE 14-bus system

16

The parameters of this modified system are as in appendix B. First of all, before

taking any line out, I have to make sure that the system is in secure. This mean,

before taking any line out, there is no power flow in other line is over the limit. I

have set the power flow limit for each line is 100MW accept for line between bus 4

and bus 9 and line between bus 5 to bus 6 I set it limit to 150MW. Figure 3.4.1 show

that the system is in secure. Blue color on the line indicate that the power flow in that

line is below the limit and orange color on the line indicate that power flow in that

line almost reaching the limit.

CHAPTER 4

RESULT AND DISCUSSION

4.1 Introduction

This chapter will discuss about the result of two analyses. The first analysis is

to study the percentage of power flow over limit in transmission lines under line

outage contingencies and the second analysis to study the ability of the MW

performance index (PIMW) method in detecting critical contingencies. After that the

comparison of these two analysis results are made.

18

4.2 Analyzing the test system

After make sure that the system is in secure, I run the system and take out one

line out (line between bus 1 and bus 2) as in figure 4.2.1:

Figure 4.2.1: 12-bus system

From the figure 4.2.1, it can be seen that when line between bus 1 and bus 2

was taken out, red color appeared on line between bus 1 and bus 5. This meant that

power flow in line between bus 1 and bus 5 is over the limit. After line between bus

1 and bus 2 was taken out, the reading of power flow in each of the other line was

taken. Then line between bus 1 and bus 2 is connected back and after that another

line is taken out and the power flow reading for each other lines are taken again. This

step was repeated for each line in the system. Next step, after taking all power flow

readings in each line when one line out, the lines were ranked according to its

severity by using MW performance index (PIMW) formula. Calculation process has

been done by using Microsoft office excel. This calculation was repeated by using

different value of n(n=1, 2, 3, 4, 5) of the PI. This ranking is later compared with the

19

percentage of power flow over limit results. As an example, from the figure 4.2.1, the

percentage of power flow in line over the limit (line between bus 1 and bus 5) is

120% and percentage of power flow in the line that almost reach its limit (line

between bus 5 and bus 6) is 83%. This step will determine the severity of each line

outage (contingency) to the other line flows.

4.3 Percentage of power flow over the limit in transmission line

Table 4.3.1: Percentage of line over limit

Table 4.3.1 shows that the percentage of power flow in line that over the

limit. When one line was taken out, there is a risk the power flow in other line is over

the limit that has been set. From the simulation, when one line was taken out, if on

other line appear red color it mean that power flow in that line is over the limit and if

on the other line appear orange color it mean that power flow in that line is almost

reaching the limit. The data in table 4.3.1 shows the ranking according to the

percentage of the power flow over the limit in the other line when one line was taken

20

out. This data were collected to compare the result of this ranking (due to the

percentage of power flow over the limit in line) with the result of the ranking using

the performance index PIMW formula. In table 4.3.1 show that only when line 5 to 6,

4 to 9, 1 to 5 and 1 to 2 was taken out one by one, there is power flow in other line is

over their limit.

4.4 MW performance index (PIMW) method

Table 4.4.1: Power Flow In Each Line (MW) When One Line Out

Table 4.4.1 show the data of the power flow in MW in each line when one

line was taken out at one time. From this data, line (taken out line) was rank by using

MW performance index (PIMW) formula until n=5. This data read from top to bottom.

Example, when line 1 to 2 out, power flow in line 1 to 5 becomes 120MW, line 2 to

3 is 10.53MW, line 2 to 4 is 47.07MW, line 2 to 5 is 40.69MW, and line 3 to 4 is

36.33MW and so on.

21

4.5 Calculating MW performance index

In this part I will show the example in calculating the MW performance index

by using this formula:

where Pl, the MW flow of line 1; , the mw capacity of line l; NL, the

number of lines of the system; Wli, real non-negative weighting factor (= 1); n,

exponent of penalty function. This calculation was using data in table 4.4.1. Always

set the value of Wl = 1 for every calculation, = 100MW for every line accept

line 4 to 9 and line 5 to 6 ( =150MW), and the value of n use in the calculation

are 1, 2, 3, 4, 5 one by one.

Refer to data in table 4.4.1, as example, PI index value when line 1 to 2 out:

There are 17 lines in the system. Pl is the MW flow in line. When line 1 to 2 taken

out, P1to2 =0MW, P1to5 =120MW, P2to3 =10.53MW, P2to5 =40.69MW, P3to4

=36.33MW, P4to5 =29.08MW, P4to9 =64.68MW, P5to6 =124.02MW, P6to11 =16.14MW,

P6to12 =34.15MW, P6to13 =62.53MW, P9to10 =3.64MW, P9to14 =28.83MW,

P10to11 =12.64MW, P12to13 =2.95MW, and P13to14 =16.07MW.

22

Firstly the calculation start with n=1. Insert all data mentioned above in MW

performance index formula:

= 3.3728

This calculation was repeated for n=2,3,4 and 5. After that, calculate the

performance index when other line out using the same steps. The calculation data

was shown in table 4.5.2.

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Table 4.5.2: ranking using MW performance index (PIMW) formula

)

Table 4.5.2 shows the ranking of line (taken out line) according to its

severity. Using different value of n its show that the ranking is not same if the value

of n change but it not has much different. That why the calculation must be done

until n=5. By this way, the severity of the line in the system can be rank accurately.

The performance index PIMW contains all line flows normalized by their limits.

These normalized flows are raised to an even power (by setting n = 1,2,….) thus,

the use of absolute magnitude of flows is avoided. This index PIMW has a small

value, when all line flows are within their limits and a high value when there are

lines overloads. There are 17 lines to be rank. Refer to table 4.5.2, line at ranking

number 1 has the highest severity and line at ranking number 17 has the lowest

severity. We can see that line between bus 5 and bus 6 is the most severe line for

each value of n (n=1, 2, 3, 4 and 5). Severity of the line is when that line is taken out,

the system is not in secure state (there is a power flow in other line is over the limit).

24

4.6 Graph MW performance index (PIMW) versus line out using data in table

4.5.2

The results of the PI by using difficult value of n are plotted in figure 4.6.1,

figure 4.6.2, figure 4.6.3, figure 4.6.4, and figure 4.6.5. From the figures, it is

observed that as n increase, the index of the credible contingencies is significant as

compared to other contingencies.

Figure 4.6.1: Graph MW performance index (PIMW) versus line out for n=1

Figure 4.6.1 show the graph of MW performance index versus line out for

value n= 1. It show that when the value of n=1, there is not much different of MW

performance index for each line out at one time. It also show that when line 5 to 6, 4

to 9, 1 to 5 and 2 to 4 out one by one have the higher MW performance index than

the other line.

PIMW

Line out

25



value n= 2. It show that when the value of n=2, the different of MW performance

index for each line out at one time is greater if compared with the graph in figure

4.6.1. It also show that when line 5 to 6, 4 to 9, 1 to 5 and 1 to 2 out one by one have

the higher MW performance index than the other line.

PIMW

Line out

26







Line out

PIMW

27







Line out

PIMW

28







All graphs above show the different in calculating MW performance index

(PIMW) for different value of n. from these 5 graph, it can be seen that line 5 to 6, 4 to

9, 1 to 5 and 1 to 2 are the line that have high MW performance index (PIMW)

compared to the other line for each value of n (n=1, 2, 3, 4 and 5). Value of n is one

of the factors in determining MW performance index (PIMW).

Line out

PIMW

29

4.7 Comparison between the results of the line ranking (due to the

percentage of power flow over the limit in line) with the result of the line

ranking using the performance index PIMW formula

Table 4.3.1 show that only when line 5 to 6, 4 to 9, 1 to 5 and 1 to 2 was

taken out one by one, there is power flow in other line is over their limit. Compared

with the result obtain from the table 4.5.2 and its graph show that line 5 to 6, 4 to 9, 1

to5 and 1 to 2 have higher performance index PIMW compared to the other line for

each different value of n. Due to the fact that index PIMW has a small value, when all

line flows are within their limits and a high value when there are lines overloads, this

comparison between the results of the line ranking (due to the percentage of power

flow over the limit in line) with the result of the line ranking using the performance

index PIMW formula due to its severity show that line 5 to 6, 4 to 9, 1 to 5 and 1 to 2

are the most severe compared to the other line.

Table 4.7.1: final ranking

Table 4.7.1 show the final ranking of the line due to its severity. Top ranking

is the most severe line and the bottom ranking is the lowest severity or not severe.

30

4.8 Summary

From the analysis it show that the comparison between the result of the

ranking due to percentage of power flow over limit in line with the result of the line

ranking using the performance index formula due to its severity prove the fact that

index PIMW has a small value, when all line flows are within their limits and a high

value when there are lines overloads.

CHAPTER 5

CONCLUSION AND FURTHER RECOMMENDATION

5.1 Conclusion

Security in power system is very important to make sure the system is in

secure state. There are many things to consider in the system to make sure that the

system is in secure state. One of it is make sure that there is no problem at the any

transmission line in the system or in other words, there is no power flow over the

limit in each of the transmission line. The security of a power system is tested

through contingency analysis. My project is focus on power transmission security.

The system is insecure if the power flow in any of the transmission line is over the

limit. By doing contingency analysis, the severe line can be identified and can be

ranked according to the severities. This is important because there are many

transmission lines in the system, so not all line to be focused. Thus the lines that are

identified as the severe contingencies will be considered further in analysis. In this

project, the ability of the performance index (PIMW) in determining critical

contingency have been studied and analyzed by

32

using a modified IEEE 14-bus system.. From the result, it is observed that the

transmission line in the system can be rank according to the severity by using MW

performance index (PIMW) formula.

5.2 Recommendation

This project focusing on contingency analysis for power transmission

security. No work being done to secure back the system. For further research, the

researcher can expand this project to determine the way to secure back the system.

The researcher may also use the bigger system to analyze the system. Other than that,

the researcher may use other performance index formulas to do the analysis. The

researcher also can use other software to test the system as example such as

MatPower.

33

REFERENCES

[1] Wood Allen J & Bruce F. Wollenberg(1984). “Power Generation, Operatio&

Control”, New York.

[2] J.Srivani & K.S. Swarup. “Power System Static Security Assesment And

Evaluation Using External System Equivalents”, Department of Electrical

Engineering, Indian Institute of Technology Madras, Chennai, India.

[3] http://www.ee.washington.edu/energy/apt/nsf/kbsmodule.html

[4] J. Deuse (2003 ). “Comprehensive approach of power system contingency

analysis”, Italy.

[5] Gabriela Glanzmann(2006). “Incorporation of N-1 Security into Optimal

Power Flow for FACTS Control”,Zurich.

[6] P.K. Iyambo, and R. Tzoneva, Member, IEEE(2007). “Transient Stability

Analysis of the IEEE 14-Bus Electric Power System”.

[7] Dr Ashwani Kumar. “ Introduction to Power World Simulator”. Department of Electrical Engineering National Institute of Technology Kurukshetra.

[8] Jizhong Zhu(1998). “Automatic Contingency Selection and Ranking Using

an Analytic Hierarchical Process”. Department of Electrical Engineering,

National University of Singapore, Singapore.

34

[9] Rajendra Singh(2007). “Line flow contingency selection and ranking using

cascade neural network”. Central Power Research Institute, Bhopal, India.

[10] Aydogan Ozdemir(2006). “Transmission losses based MW contingency

ranking”. Department of Electrical Engineering, Istanbul Technical

University, 34469 Maslak-Istanbul, Turkey.

35

APPENDIX A

Parameter of IEEE 14-bus system

39

APPENDIX B

Parameter of 12-bus system

Table B1: Generator data

Generator bus

no.

1 2 3 4 5

Power(MW) 120 120 120 0 0

Table B2: Load data

Bus no. P load(MW)

G

load(MW)

1 0 0

2 21.7 12.7

3 94.2 19

4 47.8 0

5 7.6 1.6

6 11.2 7.5

7 x x

40

8 x x

9 39.5 16.6

10 9 5.8

11 3.5 1.8

12 37.1 1.6

13 43.5 5.8

14 44.9 5

Table B3: Line data

41

APPENDIX C

GETTING STARTED WITH A POWER WORLD SIMULATOR

Power world simulator has two distinct modes that are edit mode and run

mode. Edit mode is used to construct new simulation cases or to modify existing

cases. Run mode is used to perform the actual power system simulation. We can

switch between the two modes at any time using edit mode and run mode buttons on

the program palette.

Creating a new case

To begin with, double click on the power world simulator icon. The simulator

is used to create new cases, modify the existing cases and simulate power systems.

To create new case, select a file, New Case from the main menu or click open

simulation case button on the file palette.

Inserting a bus

Select INSERT BUS from the main menu or select the bus button on the

INSERT palette. This prepares the simulator to insert a bus. Click on the on-line

background at the location where we want to place the new bus. This invokes the bus

option dialog. Use the bus option dialog box to specify the name, size, orientation,

area, zone, and nominal voltage of the bus as well as load and shunt components

connected to it. Click OK on the bus option dialog box to finish creating the bus and

to close the dialog box.

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Inserting a transmission line

To connect the buses together, we will now insert a transmission line between

them. Select INSERT TRANS. LINE from the main menu, click on the transmission

line button on the INSERT palette. Left click at the point where we want the line to

originate. Without holding down mouse, drag mouse, line sequence will follow.

Transmission line and transformers can be drawn as a series of line sequence.

Inserting text, bus and line fields

To add fields to display of a particular bus, follow the following procedure:

Right click on the bus to bring up local menu. Select add new fields around bus from

the local menu. This open the: INSERT BUS fields dialog. Use the insert bus field

dialog to designate the fields to add 8 fields per bus. Click OK, the specified bus

fields will be added to the on-line diagram.

Power flow list

To show this display, select CASE INFORMATION, POWER FLOW LIST

from the main menu. To view flow at just a few selected buses we may use quick

power flow list from a local menu and select quick power flow list.

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