Lightning Attachment C Haracteristics Of Glass And Carbon Fiber Reinforced Polymer Wind Turbine Blades

With the development of large-scale wind turbine blade,the lightning strike is one of the most severe threats and a key factor that influences efficiency and safe operation of the wind turbines(WTs).Wind turbine blades(WTBs)are equipped with lightning protection systems(LPSs)containing receptors and down conductor to interrupt lightning strikes.However,severe damages due to lightning strikes happen repeatedly,which results in causing huge losses.Wind power can be enhanced by increasing the swept area of the wind turbine and building wind turbine in elevated sites like mountains ridges,such as costal and offshore regions or at locations with high wind,but in both cases the lightning incidents to the wind turbine will increase.Swept area of the wind turbine can be increased by increasing the length of the wind turbine blade.Composite materials are being used in new generation win,d turbine blade to make blade strong and long.Every composite material has different properties.Mostly composite materials are used in the main beam of the wind turbine blade to make it strong.In this dissertation,glass fiber reinforced polymer(GFRP)and carbon fiber reinforced polymer(CFRP)composite material were used in the main beam of wind turbine blade to analyze the lightning attachment characteristics of these materials.Different types of lightning protection systems(LPSs)are made in accordance with the design and properties of composite material used in the wind turbine blade to withstand 100%lightning strikes.New CFRP composite material is an electrically conductive material,so metallic mesh was used as new lightning protection system to protect it from direct lightning strikes.Wind turbine blade specimens/models made of GFRP and CFRP composite materials were used in experiments work and simulations work to determine the effect of new composite blade materials and new lightning protection systems on lightning attachment manner to the wind turbine blade.Experiment work was performed by using high voltage strike attachment tests according to the IEC 61400-24 'Lightning Protection of Wind Turbines' standard to study the lightning attachment characteristics of GFRP and CFRP composite material wind turbine blade with different types of lightning protection systems.A standard switching waveforms of 250/2500 ?s were used in high voltage strike attachment tests.Both positive and negative polarity-switching impulses were applied to the plane/rod electrode under different air gap and lateral distances(LDs)with different blade orientation to analyze the effect of switching impulse polarity,blade orientation,LD and different types of lightning protection system on the lightning attachment manner to the wind turbine blade.3D electrostatic simulation based on finite element method(FEM)were used on GFRP and CFRP wind turbine blade models with same configuration of GFRP and CFRP wind turbine blade specimens used in experiments to determine the lightning attachment characteristics.The purpose of the 3D Finite element method(FEM)based simulation was to obtain reliable models correlated with experimental results.Experiments results were compared with the high voltage strike attachment test results to see the similarity and compatibility within the simulation and experiment results.Simulation and experimental results were almost same and had no significant difference.It was determined from experiments results that discharge attachment paths under positive and negative lightning strikes were dissimilar,and the positive discharges were difficult to intercept by lightning protection system used in wind turbine blade to protect it from direct lighting strikes.The results show that orientation of wind turbine blade has significant effect on the lighting attachment manner to the wind turbine blade,lightning attachment efficiency of the lightning protection system significantly decreases when wind turbine blade orientation moves from vertical position to horizontal position.Experiments results show that both composite materials GFRP and CFRP has no effect on the lightning attachment manner to the wind turbine blade.CFRP is an electrically conductive material,but no upward leader was observed from its surface.The metallic mesh was used as new lightning protection system to protect the conductive surface of the CFRP main beam also has no significant effect on the lightning attachment manner to the wind turbine blade,no upward leader was also observed from the metallic mesh.Simulation results show that length of GFRP main beam has no effect on lightning attachment manner but the length of CFRP main beam has significantly effect on the lightning attachment manner to the wind turbine blade.It was observed that length of CFRP main beam effects on the distribution of electric field intensity on the surface of the wind turbine blade and can divert the lightning attachment point from LPS to tip of the CFRP main beam.The efficiency of lightning protection system increases with full-length CFRP main beam.Simulation results show that lateral distance between downward leader and wind turbine blade is a key factor,which influences the interception efficiency.Lightning attachment point moves from LPS to the blade body when lateral distance increases or decreases than 0m.It was analyzed form the experiments and simulations results that tip receptor has better interception efficiency than side receptor.Internal down conductor has also effect on the lightning attachment manner.Different size and quantity of side receptor as lightning protection systems were used in simulation to see the effect of receptor size and quantity on the lightning attachment manner.Results show that size and quantity of side receptors have no significant effect on the lightning attachment manner to the wind turbine blade but it is better to use more than one side receptor because,if first side receptor fails to intercept the lightning strike than second or third will intercept it.Experiments and simulation results will help to understand the lightning attachment characteristics of the GFRP and CFRP wind turbine blade.Results will contribute to optimize the design of lightning protection system for new-generation wind turbine blade.