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A Simulation Method for the Wind Turbine‘s Electric Field Distribution Caused by the Stepped Lightning Leader. B. Lewke, S. Krämer, Y. Méndez Hernández and J. Kindersberger May 9th, 2007 Laboratory for High Voltage Technology and Power Transmission Technical University of Munich &
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A Simulation Method for the Wind Turbine‘s Electric Field Distribution Caused by the Stepped Lightning Leader B. Lewke, S. Krämer, Y. Méndez Hernández and J. Kindersberger May 9th, 2007 Laboratory for High Voltage Technology and Power Transmission Technical University of Munich & GE Global Research
Average Downtime Loss Repartition • Lightning faults cause more loss in wind turbine availability and production than the average fault. Source: VDE DIN IEC 88/117/CD(VDE 0127 Teil 24): 2000-06 Motivation
Ground flash density 1994 • Exposed Positions • High structure • Critical material compound • Steel, copper • Glass-fiber, carbon-fiber • Sensible electronics • Current amplitudes up to 200 kA have to be considered • Probability of lightning strike increases with increasing facility height • Lightning strikes per year and facility (IEC 61400-24)Example: Offshore, North sea (1.5 MW): Ref.: Spherics GmbH N_g: average, annual ground flash density A_d: equiv. collection area of direct lightning strikes to the facility C_d: Environmental factor; C_d =1 (shallow), C_d=2 (hills) Lightning and Wind Turbines
Ref.: LM Glassfiber Example for Common Lightning Protection System of Rotor Blades
Mirror charge principle to simulate excitation Leader Leader WT/Goundpotential Tip height: 20m; Peakcurrent: 2.9 kA Tip height: 30m; Peakcurrent: 5.4 kA Tip height: 45m; Peakcurrent: 10.1 kA Tip height: 60m; Peakcurrent: 15.7 kA Spiegelladungsprinzip Modeling in ANSYS
Magnitude of E-Field [kV/cm] Magnitude of E-Field [kV/cm] Radius of Corona Sheath [m] Length of Leader Channel [m] Validation of Model
2D-Cross Section Model of Rotor Blade Tip for E-Field Calculations
Down conductor Excitation path Down-conductor Distribution of Electrical Potential
Round shaped, no insulation round shaped, insulation (ETFE) Round shaped, insulation (FEP) rectangular shaped Pathlength [m] (round shaped down conductor) Electric Field [kV/cm] Pathlength [m] (rectangular shaped down conductor) Electric Field Strength at Internal Down-Conductor