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Lightning Protection of Small Wind Turbines

Lightning Protection of Small Wind Turbines. Connie-Ann Bracht B.Sc. Industrial Engineering. Overview. Impressions How does a lightning strike develop? – Basics: Lightning Physics. Which direct and indirect effect can a 200kA lightning impact have to a wind turbine? – Experiences.

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Lightning Protection of Small Wind Turbines

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  1. Lightning Protectionof Small Wind Turbines Connie-Ann Bracht B.Sc. Industrial Engineering

  2. Overview • Impressions • How does a lightning strike develop? – Basics: Lightning Physics. • Which direct and indirect effect can a 200kA lightning impact have to a wind turbine? – Experiences. • What can we do about it? - Basics: Lightning Protection Concepts. • Best practice protection elements • IEC61400-24: Lightning Protection of Wind Turbines • Interesting Literature WindEmpowerment, C.-A. Bracht

  3. WindEmpowerment, C.-A. Bracht

  4. WindEmpowerment, C.-A. Bracht

  5. Overview • Impressions • How does a lightning strike develop? – Basics: Lightning Physics. • Which direct and indirect effect can a 200kA lightning impact have to a wind turbine? – Experiences. • What can we do about it? - Basics: Lightning Protection Concepts. • Best practice protection elements • IEC61400-24: Lightning Protection of Wind Turbines • Interesting Literature WindEmpowerment, C.-A. Bracht

  6. Negative cloud to ground flashes Each lightning flash is different due to: current, charge, energy, wave form, number of repetitive impacts, duration etc. WindEmpowerment, C.-A. Bracht

  7. Lightning physics Typical waveform: 10μs/350μs Peak current: I in [kA] - up to 300 kA Steepness of current impulse: di/dt in [kA/μs] - up to 160 kA/μs Charge transferred: Q in [C] - up to 600 C Specific energy: W/R in [MJ/Ω] - up to 20 MJ/Ω WindEmpowerment, C.-A. Bracht

  8. Overview • Impressions • How does a lightning strike develop? – Basics: Lightning Physics. • Which direct and indirect effect can a 200kA lightning impact have to a wind turbine? – Experiences. • What can we do about it? - Basics: Lightning Protection Concepts. • Best practice protection elements • IEC61400-24: Lightning Protection of Wind Turbines • Interesting Literature WindEmpowerment, C.-A. Bracht

  9. Indirect effects of lightning currents Goal: Potential equalization while minimizing step & touch voltages as well as transient voltages/currents. WindEmpowerment, C.-A. Bracht

  10. Sufficient earth foundation is essential WindEmpowerment, C.-A. Bracht

  11. WindEmpowerment, C.-A. Bracht

  12. Personal Safety Safety procedure to protect people: • Local weather forecast • Safe location (e.g. cars, robust houses, position not standing) • Safe position (to crouch down and to keep feet close to each other) • Recognize high electrical fields (crackling sounds, hair standing on ends etc.) • Intermediate earthing system connections • First aid training WindEmpowerment, C.-A. Bracht

  13. Overview • Impressions • How does a lightning strike develop? – Basics: Lightning Physics. • Which direct and indirect effect can a 200kA lightning impact have to a wind turbine? – Experiences. • What can we do about it? - Basics: Lightning Protection Concepts. • Best practice protection elements • IEC61400-24: Lightning Protection of Wind Turbines • Interesting Literature WindEmpowerment, C.-A. Bracht

  14. Lightning protection concepts 1) Choose location where lightning is rare (NASA overview) 2) Build structures with reduced height 3) Provoke impacts other than in structure 4) Implement state-of-the-art protective devices (testing is essential) 5) Isolate system or create sufficient parallel path to ground WindEmpowerment, C.-A. Bracht

  15. WindEmpowerment, C.-A. Bracht

  16. Only one aspect: The number of impacts per km2 WindEmpowerment, C.-A. Bracht

  17. Overview • Impressions • How does a lightning strike develop? – Basics: Lightning Physics. • Which direct and indirect effect can a 200kA lightning impact have to a wind turbine? – Experiences. • What can we do about it? - Basics: Lightning Protection Concepts. • Best practice protection elements • IEC61400-24: Lightning Protection of Wind Turbines • Interesting Literature WindEmpowerment, C.-A. Bracht

  18. Design Best Practice • Interception: - Sharp&vortex generating receptor in blade • Sharp&long Franklin Rod • Possible: steel or copper • Conductive path: • Simple, solid, isolated and short earthing path with as few connections as possible • Copper brushes at rotating parts • Low resistance earthing system, using ring electrodes connected to reinforcement WindEmpowerment, C.-A. Bracht

  19. Examples WindEmpowerment, C.-A. Bracht

  20. House applications WindEmpowerment, C.-A. Bracht

  21. Old patent 1781: Franklin Rod WindEmpowerment, C.-A. Bracht

  22. Overview • Impressions • How does a lightning strike develop? – Basics: Lightning Physics. • Which direct and indirect effect can a 200kA lightning impact have to a wind turbine? – Experiences. • What can we do about it? - Basics: Lightning Protection Concepts. • Best practice protection elements • IEC61400-24: Lightning Protection of Wind Turbines • Interesting Literature WindEmpowerment, C.-A. Bracht

  23. IEC61400-24 Lightning Protection of Wind Turbines WindEmpowerment, C.-A. Bracht

  24. What to adapt from IEC61400-24 • Transient protection of grid connection and communication/control systems due to indirect lightning effects (ensure that system continues working after high transient voltages and currents) • Direct lightning strikes are relatively rare (depending on height and Rolling Sphere model) • Ultimate lightning protection system: lightning rod reaching above rotor, equipotential bonding, surge protection device (SPD), testing r=20m Rolling sphere model Possible lightning attachment to each point of the structure that can be touched by the sphere. WindEmpowerment, C.-A. Bracht Source: IEC 61400-24

  25. Suggestion WindEmpowerment, C.-A. Bracht

  26. Overview • Impressions • How does a lightning strike develop? – Basics: Lightning Physics. • Which direct and indirect effect can a 200kA lightning impact have to a wind turbine? – Experiences. • What can we do about it? - Basics: Lightning Protection Concepts. • Best practice protection elements • IEC61400-24: Lightning Protection of Wind Turbines • Interesting Literature WindEmpowerment, C.-A. Bracht

  27. Literature • IEC 61400-24: Lightning Protection of Wind Turbines • The Art and Science of Lightning Protection (Martin A.Uman) • Blitz und Blitzschutz (by VDE-Schriftenreihe Band 128) • Handbuch für Blitzschutz und Erdung (by Hasse/Wiesinger) • Lightning Protection Guide (by DEHN + Söhne) • PhD Blade Lightning Protection (Soeren Find Madsen) • Patents • Etc. WindEmpowerment, C.-A. Bracht

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