Assessment of wind turbines generators influence in aeronautical radars Electrical and Computer ...

140 Pages·2013·3.23 MB·English

Assessment of wind turbines generators influence in aeronautical
radars

Ricardo Manuel Lopes dos Santos

Thesis to obtain the Master of Science Degree in
Electrical and Computer Engineering

Examination Committee
Chairperson: Prof. Fernando Duarte Nunes
Supervisor: Prof. Luis Manuel de Jesus Sousa Correia
Member of Committee: Prof. António Manuel Restani Graça Alves Moreira
Member of Committee: Eng. Álvaro Ramalho de Melo Albino

October 2013
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To the Ones I love

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Acknowledgements
Acknowledgements
My first acknowledgement is to Prof. Luis M. Correia, the supervisor not only of the thesis but also of
the personal development during the last year. He proved to be not only a good Professor, but also an
inspiring person, sharing his knowledge, and was always available to help. I would also like to thank
him for the opportunity of developing my thesis in collaboration with NAV Portugal, which turned out to
be a valuable experience, and for being part of GROW, where I learned more about other
telecommunication topics as well as presentation skills.
I wold like to thank all the GROWers, especially to Carla Oliveira and Michal Mackowiak, for following
my work, making suggestions, and correcting my Thesis.
To the engineers from NAV Portugal, namely Eng. Carlos Alves, Eng. Luís Pissarro and Eng. Álvaro
Albino, whose contribution for the work is indisputable. I am thankful for the numerous exchanged
emails to clarify my doubts, the regular meetings to give feedback from the work, and the help
developing the final document.
To my GROW colleagues, a very special thanks for following me in this journey, giving their friendship
and support, especially to Diogo, Dinis, and, Joana. And to all my old friends, Pedro L., J. Pedro,
André, Pedro D., Marco, Andreia, Joana, Marta and Sara. For them I wish the best success in their
working careers.
Finally, to the persons most important for me in my live, a very especial thanks to my great mom,
grandparents, godparents, father, brother, and sisters for their unconditional and constant support,
encouragement, belief and everything that they have done for me. At last, but not the least, I would
like to thank to my great love, Filipa.

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Abstract
Abstract
Airspace surveillance radars are very sensitive to interferences. The presence of wind turbines can
create problems to some telecommunication systems relying on line of sight communication. This
thesis analyses the disturbance in the propagation of the signals created by the movement of the
rotating blades. A model is developed to characterise the wind turbine from the radar viewpoint, using
the radar cross section concept and the diffraction theory. A model to quantify the impact on primary
and secondary radars was also developed. The models used to describe the most probable airplane
positions are also presented. A simulator was developed to know the amount of interference caused
by the wind turbines for various scenarios. Simulation results show a great impact created by wind
turbines on a primary radar, up to 36.05 dBsm. The results also show some critical points identified for
the secondary radar, when the airplane lies in the same azimuth as the wind turbine. The Doppler shift
could generate false targets in primary radar, due to the high velocities at the blade edge, up to 282
km/h. Finally, one defines exclusion regions around the radar, which can go up to 13 km, depending
on the surrounding terrain and the radar characteristics.
Keywords
Primary Radar, Secondary Radar, Wind Turbine, Interference, Diffraction, Exclusion Region.

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Resumo
Resumo
Os radares de vigilância do espaço aéreo são muito sensíveis a interferências. A presença de
turbinas eólicas pode provocar problemas nos sistemas de telecomunicações que têm por base a
comunicação em linha de vista. É analisada a perturbação na propagação dos sinais criados pelo
movimento de rotação das pás. É desenvolvido um modelo para caracterizar a turbina eólica sob o
ponto de vista do radar, usando o conceito de secção eficaz, e a teoria da difração. É também
desenvolvido um modelo para quantificar o impacto criado nos radares primário e secundário. Um
modelo usado para descrever as posições mais prováveis dos aviões é também apresentado. É
desenvolvido um simulador para conhecer a quantidade de interferência causada pelas turbinas para
os vários cenários identificados. Os resultados mostram um grande impacto causado pelas turbinas
no radar primário, até 35 dBsm. O simulador também identifica alguns pontos críticos para o radar
secundário, quando o avião e a turbina se encontram no mesmo azimute. O desvio de Doppler pode
originar falsos alarmes no radar primário, devido às elevadas velocidades observadas no extremo das
pás, até 282 km/h. Por fim, são identificadas as regiões de exclusão à volta do radar, que podem ir
até 13 km, dependendo no perfil do terreno e das características do radar.
Palavras-chave
Radar Primário, Radar Secundário, Turbinas Eólicas, Interferência, Difração, Região de Exclusão

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Table of Contents
Table of Contents

Acknowledgements .................................................................................. v 
Abstract .................................................................................................. vii 
Resumo .................................................................................................. viii 
Table of Contents .................................................................................... ix 
List of Figures ......................................................................................... xii 
List of Tables ......................................................................................... xiv 
List of Acronyms ..................................................................................... xv 
List of Symbols ...................................................................................... xvii 
List of Software ...................................................................................... xxi 
1  Introduction .................................................................................... 1 
1.1  Overview .................................................................................................. 2 
1.2  Motivation and Contents .......................................................................... 5 
2  Basic Concepts ............................................................................. 7 
2.1  The Aeronautical Surveillance System .................................................... 8 
2.1.1  The Current Surveillance Systems ........................................................................ 8 
2.1.2  Primary Surveillance Characterisation .................................................................. 9 
2.1.3  Secondary Surveillance Characterisation ........................................................... 12 
2.2  Wind Turbine Characterisation .............................................................. 18 
2.3  Influence of Wind Turbine on Air Surveillance Systems ........................ 20 
2.3.1  Wind Turbine Modelling ....................................................................................... 20 
2.3.2  Assessment Regions ........................................................................................... 22 
2.4  State of the Art ....................................................................................... 24 
3  Model Development and Implementation .................................... 27 
3.1  Propagation Models ............................................................................... 28 
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3.1.1  Line of Sight ......................................................................................................... 28 
3.1.2  Diffraction over Terrain ........................................................................................ 29 
3.1.3  Atmospheric Attenuation ..................................................................................... 30 
3.1.4  Spherical Earth Model ......................................................................................... 31 
3.2  Wind Turbine Radar Cross Section ....................................................... 33 
3.2.1  Radar Cross Section Prediction Methods ........................................................... 33 
3.2.2  Wind Turbine Tower Radar Cross Section .......................................................... 34 
3.2.3  Blades Mono-Static Radar Cross Section ........................................................... 35 
3.3  Diffraction on the Wind Turbine Blades ................................................. 36 
3.4  Models to Assess the Wind Turbine Influence on Radars ..................... 37 
3.4.1  Wind Turbine Shadow Region ............................................................................. 37 
3.4.2  Impact on Primary Radar Performance ............................................................... 38 
3.4.3  Impact on Secondary Radar Performance .......................................................... 41 
3.5  Doppler Effect ........................................................................................ 43 
3.6  Flight Routes ......................................................................................... 44 
3.7  Interference Simulator ........................................................................... 46 
3.7.1  Simulator Structure and Parameters ................................................................... 46 
3.7.2  Local Spherical Coordinate System .................................................................... 47 
3.7.3  Diffraction Coefficient Algorithm .......................................................................... 49 
3.7.4  Primary Radar Interference Simulator ................................................................. 49 
3.7.5  Secondary Radar Interference Simulator ............................................................ 50 
3.8  Model Assessment ................................................................................ 52 
4  Analysis of Results and Definition of Exclusion Regions ............. 55 
4.1  NAV Portugal’s Surveillance Systems ................................................... 56 
4.2  Scenarios Definition ............................................................................... 58 
4.3  Doppler Effect Impact Assessment ........................................................ 62 
4.4  Interference Simulator Results .............................................................. 64 
4.4.1  Primary Radar ...................................................................................................... 64 
4.4.2  Secondary Radar ................................................................................................. 68 
4.5  Exclusion Region Definition ................................................................... 72 
4.5.1  Primary Radar ...................................................................................................... 72 
4.5.2  Secondary Radar ................................................................................................. 74 
5  Conclusions ................................................................................. 77 
Annex A.  Building Restricted Areas for Surveillance Facilities ............ 81 
Annex B.  Recommended SSR Protection Range ............................... 83 
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