POWER FACTOR CORRECTION IN LV 
DISTRIBUTION SYSTEMS AND ITS COST 
BENEFIT ANALYSIS 
Master of Science Dissertation 
D.A.P. AMARASENA 
Department of Electrical Engineering 
University of Moratuwa, Sri Lanka 
March 2006 
85786 
ABSTRACT 
When the complex power definition is analyzed, it will be seen that, if a pure resistive 
load is connected to an AC source, the source will be fully utilized while the reactive 
power delivered will be zero. A practical load, however, absorbs both active power 
and reactive power. The active power does the useful work, while the reactive power 
is required to produce the electromagnetic field. Both the active and the reactive 
powers place a burden on the conductor (or on distribution line), however the power 
company must provide the current to the load whether it is inductive or capacitive,and 
this current generates the power losses in the distribution lines and also increases the 
maximum demand. 
The aim of this study is to analyze LV distribution feeders of substations to find the 
optimum point along the feeder to correct the power factor. At this particular point, 
the loss, which considered as the main burden are at minimum level while some 
reduction in maximum demand. To find the optimum point, calculation for each and 
every point load (i.e.pole load) is very difficult and complex task without having a 
specially developed computer software package. Hence the whole loads of the 
distribution feeder are generalized to thirteen point loads(i.e. twelve spans). 
Calculations have been done based on practically obtained data to determine the 
optimum location for power factor correction. This shows that, pay back period is very 
attractive and results were quite differing from case to case due to different loading 
patterns of the feeders. 
Still this type of power factor correction is not being practiced by both the utilities 
(CEB& LECO)of Sri Lanka. This study shows that there is a high potential to 
improve the LV system performance by having a relatively low investment with farley 
short pay back periods. 
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DECLARATION 
The work submitted in this dissertation is the result of my {wn investigation, except 
where otherwise stated. 
It has not already been accepted for any degree, and is also not being concurrently 
s~A:: other degr~. 
D.A.P. Amarasena 
Date: 1 f /~.&~~ 
I endorse the declaration by the candidate. 
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Prof. H. Y. R Perera 
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ACKNOWLEDGEMENT 
Thanks are due first to my supervisor, Prof. II.Y.R Perera, for his great insights, 
p~rspectives and guidance. 
My sincere thanks go to the officers in Postgraduate office, Faculty of Engineering. 
University of Moratuwa, Sri Lanka for helping in various ways to clarify the things 
related to my academic works in time \\-ith excellent cooperation and guidance. 
Sincere gratitude is also extended to the people who serve in the Department of 
Electrical Engineering Office. 
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I am very much grateful to Mr. II.H. Sumanadasa, Branch manager of Lanka 
Electricity Company (Pvt.) Limited and Mr. Daminda Darshana, Electrical Engineer 
of Lanka Electricity Company (Pvt.) Limited for their assistance and cooperation 
during the research work 
Finally, all my friends and postgraduate students in University of Moratuwa and all 
the others who helped me in various ways through my research are also appreciated. 
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TABLE OF CONTENTS 
Page 
DECLARATION ................................................................................................ I 
ABSTRACT ...................................................................................................... II 
ACKNOWLEDGEMENT ................................................................................ IV 
TABLE OF CONTENTS .................................................................................. V 
LIST OF FIGURES ....................................................................................... VIII 
j LIST OF TABLES .......................................................................................... IX 
LIST OF ACRONYMS ..................................................................................... X 
CHAPTER 1 - INTRODUCTION ...................................................................... 1 
1.1 General Background ................................................................. .................. 1 
1.1.1 Low-Voltage (LV) Distribution System ............................................................ 1 
1.1.2 LV Distribution Losses ................................................................................... 1 
1.2 Power Factor and its Impact to LV Distribution System .............................. 2 
1.2.1 Power Factor .............................. ............................................................... 2 
1.2.2 Causes of Low Power Factor ......................................................................... 3 
1.2.3 Benefits of Improving Power Factor ............................................................... 3 
1.3 Motivation .......................................................................... : ........................ 5 
1.4 Objectives ........................................................ !i-' ......................................... 5 
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1. 5 Methodology ............................................................................................... 5 
1.5.1 Literature Survey ........................................................................................... 5 
1.5.2 Site Selection ............................................................. ......................... ,. .......... 6 
1.5.3 Data Collection ............................................................................... -::: ............ 6 
1.5.4 Data Analysis ........................................................... .. .................................... 7 
CHAPTER 2 - PROBLEM IDENTIFICATION AND PROPOSEQ._SdeUTION 8 
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2.1 Problem Identification ....................................................................... -::~ ....... 8 
2.2 Proposed Solution ...................................................................................... 8 
CHAPTER 3- THEORETICAL DEVELOPMENTS ....................................... 10 
3.1 Analysis of Distribution Calculation in LV System .................................... 10 
3.1.1 Power Factor Referred to Receiving End Voltage ........................................ 10 
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3. 1.2 Power factors referred to respective load voltages ....................................... 12 
3. 1.3 Power and Loss Calculations ....................................................................... 13 
3.2 Simulation of Distribution Feeder for Optimum PF Location ..................... 14 
3.2.1 Tools Selection .............................................................. .............................. 14 
3.2.2 Justification of Thirteen Poles Selection for Calculation ............................... 14 
3.2.3 Development of Spread-sheet Calculations ................................................. 15 
CHAPTER 4 - SITE SELECTION AND OAT A COLLECTION ...................... 17 
4.1 Site Selection .. .. ... ................................................................ ..... .. ............. 17 
4.1.1 Distribution Substation - Sub-A .................................................................... 17 
4.1.2 Distribution Substation - Sub-S .................................................................... 17 
4 .2 Data Collection ........................................... ... ......................... .................. 18 
CHAPTER 5 - CALCULATIONS .................................... J .............................. 19 
5.1 Sample Calculation ................. .. ............ .. ........ ..... ........................ .. .... ...... 19 
5.2 Distribution Substation- Sub-A .............................. ...... ... ...................... ... 21 
5.2.1 Daily Current and PF Variation .................. .. ...... .. .. .................. ..................... 21 
5.2.2 Daily Active (P), Reactive (Q) and Apparent (S) Power Variation ................. 22 
5.2.3 Calculation of the losses ...................................... .. ........ .... .... ...................... 23 
5.3 Distribution Substation- Sub-8 ...................................................... .. .... .. .. 25 
5.3.1 Daily Current and PF Variation .................................... ................................. 25 
5.3.2 Daily Active (P), Reactive (Q) and Apparent (S) Power Variation ................. 27 
5.3.3 Calculation of the losses .............................................................................. 28 
CHAPTER 6- RESULTS AND ANALYSIS ................................................... 31 
6.1 Distribution Substation- Sub-A ........................................ ~ ....................... 31 
6.2 Distribution Substation- Sub-8 .................. ...  7 ......................................... 32 
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CHAPTER 7- CONCLUSIONS ..................................................................... 34 
7 .1 Conclusions and Remarks ... .. ... .. ......................... .... ......... .... .. .. ... ._.. : ..... .. .. 34 
7 .2 Recommendations for Future Research .. .. .. ............................................. 35 
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REFERENCES .......................................................................... ~:; .................. 36 
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APPENDICES ................................................................................................ 37 
Appendix A: Sample Calculation ................. ... ....................... ... ........ ............. 38 
Appendix 8 : Measured Data ......................... ............... .... .... ... ....................... 43 
Appendix C: Field Data .. ............................ .... ............. ............ ... ................... 49 
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09 · ..................................... v-qns JO SUO!le1no1e~ OIN pue sasso1 :a X!puaddy 
LIST OF FIGURES 
Page 
Figure 1.1 : The Power Triangle .................................................................................... 3 
Figure 2.1 : Arrangement of loads connected to feeder ................................................. 8 
Figure 3.1 : Loads distributor ....................................................................................... I 0 
Figure 3.2 :Vector diagram of PF referred to receiving end voltage .......................... 11 
Figure 3.3: Vector diagram ofPF referred to respective load voltages ...................... 12 
Figure 3.4 : Generalized feeder data for thirteen poles ................................................ 15 
Figure 5.1 : Losses variation at different pole position after PF correction at pole i for 
sample calculation ................................................................................................ 20 
Figure 5.2 :Daily Current and PF Variation - Sub-A .............. / ............................... 21 
Figure 5.3 :Daily Current & Time Period Averaged Current - Sub-A ....................... 22 
Figure 5.4: Daily PF & Time Period Averaged PF - Sub-A ...................................... 22 
Figure 5.5: Daily Active ( P ), Reactive (Q) and Apparent ( S) Power Variation -
Sub-A ................................................................................ ................................... 23 
Figure 5.6 : Losses variation at different pole position for different time periods after 
PF correction at pole i Sub-A ............................................................................ 24 
Figure 5.7: Daily Current and PF Variation - Sub-B .................................................. 26 
Figure 5.8 : Daily Current & Time Period Averaged Current-Sub-B ....................... 27 
Figure 5.9: Daily PF & Time Period Averaged PF- Sub-:B ....................................... 27 
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Figure 5.10 : Daily Active ( P ), Reactive ( Q) and Apparent ( S) Power Variation-
Sub-B .................................................................. ,.1,. ............................................ 28 
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Figure 5.11 : Losses variation at different pole position for different time periods after 
PF correction at pole i- Sub-B ............................................................................ 29 
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LIST OF TABLES 
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Table 3.1 : Feeders Length and Pole data of Substations ............................................ 14 
Table 5.1 :Input data for sample calculation ............................................................... 19 
Table 5.2 : Losses after PF correction at pole i for sample calculation ....................... 20 
Table 5.3 :Time Period Averaged Current & PF - Sub-A .......................................... 2 1 
Table 5.4 : Losses for different time period after PF correction at pole i- Sub-A ...... 24 
Table 5.5: Time Period Averaged Current & PF- Sub-B .......................................... 26 
Table 5.6: Losses for different time period after PF correction at pole i - Sub-B ...... 29 
Table 6.1 :Total cost saving - Sub-A .......................................................................... 31 
fable 6.2 : Total cost saving-Sub-B ............................................ ~ .. .......................... 32 
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LIST OF ACRONYMS 
AC - Alternative Current 
CEB - Ceylon Electricity Board 
EMR - Energy Management Report 
LECO - Lanka Electricity Company (Private) Limited 
LV - Low Voltage 
MD -Maximum Demand 
PF - Power Factor 
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