| In recent years,countries around the world have continuously increased their efforts to exploit new energy,including clean energy such as water energy,wind energy,and solar energy.Focusing on the present and the global future development situation,China has promoted the development of wind power generation technology as a powerful means of new energy development.Driven by technology,the scale of wind farms and their single-unit capacity have increased year by year,and hidden safety issues have emerged.For inland wind farms that are often built in mountainous areas and fields,their regional characteristics are prone to highfrequency lightning,and the risk of lightning strikes is greater.In severe thunderstorm weather,the lightning current caused by downward lightning flowing into the wind turbine will cause strong electromagnetic and thermal effects,which will cause high-amplitude overvoltage in the power collection system of the wind turbine,and further lead to equipment damage and system collapse.Wind turbines have a high probability of being struck by multiple lightning strikes.Statistics of lightning strike data show that 80%of ground lightning strikes are multiple lightning strikes.However,domestic and foreign scholars rarely consider multiple lightning strikes in their research on lightning protection related to wind turbines.This paper focuses on considering the lightning transient response of the wind turbine power collection system under multiple lightning strikes,and proposes targeted lightning protection measures for related phenomena to reduce the impact on the system.Firstly,the mechanism of lightning and multiple lightning strikes is mainly expounded.After selecting the appropriate lightning current model,the corresponding current waveforms of direct lightning strike and induced lightning are simulated respectively.Then the RLC electrical model of the blades,towers,cables and grounding devices in the wind turbine is established,so that the wind turbine,box-type transformer and power collection circuit are built in the ATP-EMTP electromagnetic transient simulation software.Wind turbine collector system model.Considering the two situations of lightning strike on fan blades and lightning strike on collector lines,the transient overvoltage waveforms of signal cables,both sides of box-type transformers,and grounding devices during multiple lightning strikes are calculated and analyzed,so as to propose targeted lightning protection measures.The research results show that when the fan blade is struck by lightning,the amplitude of the overvoltage generated by the subsequent lightning strikes on the tower and the cable core is higher than that of the first lightning strike,and has obvious high-frequency characteristics;under multiple lightning strikes,the transient potential on the tower As the height above the ground increases,it tends to rise and reaches a peak value at the top of the tower.The potential amplitude on the cable core and the height above the ground show a concave trend;The overvoltage generated by the first lightning strike on both sides of the box transformer is higher than that of the subsequent lightning strikes,and the overvoltage generated by the subsequent lightning strikes on the signal cable is larger and more destructive;the lightning transient response on the grounding device shows that the first lightning strike The impact of the grounding device is greater,in which the amplitude of the impact grounding resistance decreases with the increase of the resistivity,while the per-unit value of the power frequency resistance does not change with the resistivity;the way of connecting cables in series can reduce the box in the case of multiple lightning strikes Change the overvoltage on both sides and reduce the steepness of the intrusion wave;the installation of the two-stage surge protector effectively reduces the lightning transient overvoltage on the signal cable and ensures the safe and reliable operation of the system. |
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