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CLEARANCE TO BUILDINGS FROM OVERHEAD 
TRANSMISSION LINES 
A dissertation submitted to the 
Department of Electrical Engineering, University of Moratuwa 
in partial fulfillment of the requirement for the 
Degree of Master of Science 
Supervised by 
Prof. J.R. Lucas 
Eng. W.D.A.S. Wijayapala 
Department of Electrical Engineering, 
University of Moratuwa 
By 
KANKANAMGE SHYAMALI 
Sri Lanka 
University of Moratuwa 
llll III I III III 
94848 
February 2010 9WW 
94348 
K.K.Shvamali 07/8415 
Declaration 
The work submitted in this thesis is the result of my own investigations except where 
otherwise stated. 
This subject has not been accepted for any degree, and is also not being 
concurrently submitted for any other degree by me or any other individual. 
K.K. Shyamali 
I endorse the declaration by the candidate. 
Prof. J.R. Lucas Eng. W.D.A.S. Wijayapala 
Msc. In Electrical Engineering Page i 
K.K.Shvamali 07/8415 
T A B L E O F C O N T E N T S 
T A B L E O F C O N T E N T S II 
ABSTRACT m 
ACKNOWLEDGEMENT iv 
LIST OF FIGURES v 
LIST OF TABLES vi 
LIST OF ANNEXES VII 
CHAPTER - 1 1 
INTRODUCTION AND SCOPE 1 
CHAPTER - 2 3 
PROBLEM IDENTIFICATION 3 
C H A P T E R - 3 7 
METHODOLOGY 7 
C H A P T E R - 4 4 1 
CONCLUSION 4 1 
REFERENCE 4 3 
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K.K.Shvamali 07/8415 
Abstract 
With the increasing demand for electricity supply and the country development, 
Searching of Transmission Line corridor across populated areas is a major difficulty 
faced by the utility company. Further, most of the funding agents are very much 
concerned about the environmental impacts due to the constructions. 
The width of Transmission Line corridor is proposed for two different Transmission 
Voltages and the sharing of single corridor for more lines and the required widths are 
proposed. Possibility of building construction and planting of trees within the 
Transmission Line corridor is decided and the maximum heights for constructions 
are also proposed. 
Msc. In Electrical Engineering Page iii 
• 
K.K.Shvamali 07/8415 
Acknowledgement 
First I offer my sincerest gratitude to my supervisors, Professor Rohan Lucas, and 
Eng. W.D.A.S. Wijayapala who supported me by encouraging throughout my thesis 
with their patience and knowledge. Also my thanks should go to Dr. J. P. 
Karunadasa, Head of the Department of Electrical Engineering, and the other 
members of the academic staff of the Department of Electrical Engineering, for their 
valuable suggestions and comments. 
Further, I would like to thank the officers in Post Graduate Office of the Faculty of 
Engineering of University of Moratuwa for helping in various ways to clarify the things 
related to my academic works in time with excellent cooperation and guidance. 
Sincere gratitude is also extended to the people who serve in the Department of 
Electrical Engineering office. 
Also, I thank my colleagues in the Transmission Design branch of Ceylon Electricity 
Board very much for providing assistance in numerous ways to carry out the studies 
of the project. 
I express my thanks and appreciation to my family for their understanding, motivation 
and patience. Lastly, but in no sense the least, I am thankful to all colleagues and 
friends for giving their fullest co-operation throughout the time of research and writing 
of this thesis. 
i 
Msc. In Electrical Engineering Page iv 
List of Figures 
Figure 2-1: minimum horizontal clearance for buildings 4 
Figure 3-1: Conductor Horizontal Displacement 7 
Figure 3-2: Conductor Swing Angle 8 
Figure 3-3: Equivalent Span 9 
Figure 3-4: Catenary Curve 15 
Figure 3-5: Design of Insulator Swing Angle of Tower 23 
Figure 3-6: Top View of Right-of-Way 34 
Figure 3-7: shared Corridor 35 
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K.K.Shvamali 07/8415 
List of Tables 
Table 3-1: Defined Equivalent Span in CEB 9 
Table 3-2: Conductor Properties 11 
Table 3-3: Conductor Horizontal Displacement Vs Equivalent Span for 132kV 18 
Table 3-4: Conductor Horizontal Displacement Vs Equivalent Span for 220kV 18 
Table 3-5: Classification of Wind Speed in www.windfinder.com 21 
Table 3-6: Classification of Wind Speed in Wind Energy Resource Atlas of Sri Lanka 
22 
Table 3-7: National Electrical Safety Code Basic Clearance 26 
Table 3-8: National Electrical Safety Code Basic Clearance 26 
Table 3-9: National Electrical Safety Code Basic Clearance 27 
Table 3-10: National Electrical Safety Code Basic Clearance 27 
Table 3-11: Minimum Horizontal Clearance to objects 132 KV 29 
Table 3-12: Minimum Horizontal Clearance to Rail Cars-132 KV 29 
Table 3-13: Minimum Horizontal Clearance to objects-220 KV 30 
Table 3-14: Minimum Horizontal Clearance to Rail Cars-220 KV 30 
Table 3-15: Minimum Horizontal Separation between 132kV conductor attachment 
point and the other objects 32 
Table 3-16: Minimum Horizontal Separation between 220kV conductor attachment 
point and the other objects 33 
Table 3-17: field exposure limits 39 
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* 
K.K.Shyamali 07/8415 
List of Annexes 
Annex 3-1: Catenary Curve Coordinates for 132kV ZEBRA Conductor at 75°C and 
No wind condition 
Annex 3-2: Catenary Curve Coordinates for 132kV ZEBRA Conductor at 15°C and 
Maximum wind condition 
Annex 3-3: Catenary Curve Coordinates for 220kV ZEBRA Conductor at 75°C and 
No wind condition 
Annex 3-4: Catenary Curve Coordinates for 220kV ZEBRA Conductor at 15°C and 
Maximum wind condition 
Annex 3-5: Wind Data from www.windfinder.com/windreports/ 
Annex 3-6: Drawings for Single Line Corridor 
Annex 3-7: Drawings for Shared Corridor 
Annex 3-8: Maximum Height of Buildings within Right-Of-Way 
Annex 3-9: Mature Height of Tree within Right-Of-Way 
Annex 3-10: Typical Right-Of-Way width specified in some references 
Annex 3-11: Sample List of Actual Spans 
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