| As the capacity of a single wind turbine continues to increase,the blade height to ground continues to increase,and the lightning attraction capacity is significantly enhanced.Inland wind turbines are usually installed in areas such as mountain tops,grasslands and Gobi where the soil resistivity is high,and failures of electrical equipment and control equipment inside the wind turbine caused by lightning backlash occur from time to time.It is important to know the detailed transient characteristics of wind turbine lightning is the basis for improving the lightning protection of wind farms,and the existing studies on the transient characteristics of wind turbine lightning have not considered the effect of natural grounding of reinforced concrete foundation,and there is an urgent need to carry out relevant research.The paper analyzes the physical structure of the wind turbine,establishes the equivalent simulation calculation model of the wind turbine,carries out a more comprehensive simulation calculation and theoretical analysis work,and at the same time proposes a lightning protection scheme for the first and second systems of the wind turbine.The main work of this paper is as follows:(1)Based on the calculation principle of momentum method,a three-dimensional equivalent model of wind turbine lightning strike electromagnetic transient considering the natural grounding effect of reinforced concrete foundation is constructed,and the influence of different influencing factors such as tower height,grounding system structure and lightning current waveform on the lightning strike transient characteristics of wind turbine tower is studied;(2)The lightning strike transient characteristics of wind turbine grounding system are calculated and analyzed,and the influence of different influencing factors on the lightning strike transient characteristics of the grounding system is considered.Calculated and analyzed the lightning strike transient characteristics of the grounding system of the wind turbine,considering the influence of different influencing factors on the lightning current and transient potential rise on the grounding system,and put forward suggestions for optimizing the grounding design of the wind turbine in the high soil resistivity area;(3)Studied the lightning strike transient characteristics of the first and second systems of the unit,considering the influence of different influencing factors on the lightning transient voltage distribution of the control cable and fiber optic cable and the residual voltage,current and absorbed energy of the transformer high-voltage side arrester,and the related protection scheme is proposed.The research results show that:(1)the transient lightning current waveform on the wind turbine tower shows obvious attenuation oscillation due to the folding and reflection process,the higher the height of the tower the smaller the frequency of the lightning current oscillation;the reinforcement in the natural grounding body of the wind turbine can improve the dispersion of the lightning current and significantly reduce the transient potential rise of the wind turbine tower.(2)In the high soil resistivity area,the reinforcement in the vertical pile foundation of the grounding body can significantly reduce the impact grounding resistance value of the wind turbine;the temporary potential rise of the grounding system is reduced to a small extent when the number of vertical pile foundation is increased or the vertical pile foundation is distributed at the edge of the bearing platform.(3)The potential difference between core and shield and between shield and tower is large when the shield of control cable is grounded at single end,while the potential difference between shield and tower is small when the shield is grounded at double end,and the potential difference between shield and tower varies with the height from ground in inverted ’U’ shape.(4)In the case of fiber optic cable metal sheath is not grounded between the fan fiber box and sheath potential difference and the electric field strength around the cable is high,while the fiber optic cable sheath are grounded inside and outside the fiber box,both have different degrees of reduction;while the potential difference between the fiber box and sheath with the increase in soil resistivity,with the increase in lightning current wave front time and decrease.(5)Transformer high-voltage side arrester residual voltage,current and absorbed energy are increased with the increase of lightning current amplitude and wind turbine grounding resistance value.The results of the paper can provide theoretical reference for wind farm lightning protection and have some practical engineering value. |
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