Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Kim Bertelsen (1) F P Javier Lopez (3) Stephan Vogel (2) Joachim Holbøll (2) Søren Find Madsen (3)
(1) Global Lightning Protection Services A/S, Herning, Denmark (2) Technical University of Denmark, Lyngby, Denmark (3) Global Lightning Protection Services A/S, Hedehusene, Denmark
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Mr. Bertelsen has worked with lightning protection of wind turbines in more than 20 years and is co-founder and CEO of Global Lightning Protection Services A/S. The key areas of Mr. Bertelsens work is design and construction of lightning protection systems for wind turbines, surge protection and analysis of indirect effects and verification tests of complex wind turbine components and systems. Kim is involved actively in the IEC standardization committees concerning general and wind turbine specific lightning protection standards, chairing the group concerning risk evaluation during the maintenance process of IEC 61400-24.
Enhanced lightning effects testing for optimized wind turbine reliability
Lightning related damages and costs are regarded being one of the larger issues for wind turbine operators in certain regions of the world, and the effort in improving designs, manufacturing quality and scheduled maintenance of modern wind turbines has become very important for the manufacturers. Since 2010, wind turbines may have been certified according the IEC 61400-24 Wind turbines – Part 24: Lightning protection, requiring verification of the applied protection measures. The present paper presents a new mean of verification, namely full scale lightning current testing on complete nacelles and wind turbine blades.
The ELITE (Enhanced LIghtning effects Testing) project starts by investigating the actual lightning exposure of wind turbines by gathering information from many research communities, wind turbine manufacturers, owners and operators of the systems. This information is compiled into design and test requirements, which is the basis for the generator design. The generator is designed to inject lightning current pulses (IEC LPL1) into full scale structures like 50-100m blades and 3-10MW nacelles, to investigate the overall exposure and determine the compliance with the lightning protection standards.
Main body of abstract
One of the requirements in IEC 61400-24 states that the lightning protection concept applied on the wind turbine needs to be verified. The verification is conducted using
1. High voltage and high current testing
2. Numerical modeling, using models verified by field data or testing
3. Comparison with similar wind turbine designs with a proven and successful field experience
The design and materials used in wind turbine nacelles and blades are improving constantly, such that comparison with previous designs with proven track record becomes difficult. The verification tests described in Annex D of IEC 61400-24 have therefore been used on a large variety of sub components, subsystems and complete full scale assemblies. The outcome of such tests gives engineering insight into how the different structures react upon the lightning exposure, and has also been used to issue certificates on designs complying with the test requirements.
Modern wind turbines and wind power plants are very advanced power generating units, which due to requirements of the TSO (Transmission System Operator) can participate in power and voltage stability. This implies that the wind turbine contains a large amount of measurement and control systems, sensitive power electronics and a large variation of mission critical components. Due to complex electromagnetic and direct couplings of the different systems, the installations can only rarely be tested and validated on a subsystem level. The solution is therefore to conduct full scale tests of the turbine main components, where the system is exposed to the full threat.
The ELITE project (Enhanced lightning effects testing for optimized wind turbine reliability) has the main purpose of designing and constructing an impulse current generator capable of injecting real lightning current with the correct amplitude and waveform into structures of realistic size (3-10MW nacelles and blades of 50-100m). The paper will present in more detail the rationale behind such tests, the research in investigating the actual lightning environment to the wind turbines and the considerations of the specific generator design.
The content of the paper will outline the actual lightning exposure on wind turbines, based on review and information from installations worldwide and contributions from numerous lightning research groups, improving the design tools currently applied. The ELITE generator will enable tests of large and complex systems with realistic lightning impact, to verify and improve designs before installation. The cost reduction of validating designs on a laboratory level is considerably lower than after installation in field.