Research On Lightning Transient Response And Protective Measures Of Wind Farm Based On Multiple Lightning Strikes

With the continuous decrease of fossil energy and the continuous deterioration of the ecological environment,it has become a common consensus to reduce the extraction of fossil fuels and vigorously develop clean energy.In recent years,China’s energy structure is being adjusted,and the proportion of clean energy has gradually increased.Among them,the scale of wind power is growing rapidly.Wind farms are often built in blast areas,where the density of lightning strikes is high and they are vulnerable to lightning strikes.CIGRE TB 549 states that 80%of ground lightning strikes are multiple lightning strikes.Multiple lightning strikes generally do not strike the same point,and the lightning strike locations are usually linear or patchy.With the gradual increase of the scale of wind farms,the probability of multiple lightning strikes to wind farms is getting higher and higher.It is of practical engineering significance to study the effects of multiple lightning strikes on transient overvoltages of wind farms.The purpose of this paper is to analyze the transient response of various equipment in the field when the wind farm is subjected to multiple lightning strikes,in order to provide a theoretical basis for the lightning protection design of the wind farm,and take effective lightning protection measures to reduce the probability and loss of lightning accidents.Firstly,the physical models of wind turbine blades,towers,cables,and grounding devices were analyzed using related theories of electrical networks,and transformed into RLC electrical models.The section lengths of towers and signal cables based on multiple lightning strikes were derived.The technical parameters of related equipment,using the electromagnetic transient simulation software ATP-EMTP to build a wind farm model including a wind turbine and a collector system,calculate the lightning transient response of key equipment in a single wind turbine and a combined wind power cluster,and Proposed effective lightning protection measures.The research results show that:when the blades of the unit wind turbine are subjected to lightning strikes,the transient potentials of the tower and the cable core are more affected by subsequent lightning strikes,and the transient potentials on both sides of the box transformer are more affected by the first lightning strike;under two lightning strikes,the wind turbine The amplitude of the potential of the tower obeys the rule of "gradual decrease from the top of the tower to the bottom of the tower",but at any part of the tower,the amplitude of the transient potential produced by subsequent lightning strikes is greater than that at the time of the first lightning strike;the signal cable core is temporarily The state potential is distributed in a "U"shape.In a combined wind turbine group,the peak value of the transient potential of the power cable in the tower when the lightning strikes the blades is several times or even ten times higher than when the lightning collector line is hit;the low-voltage side of the wind turbine box that is directly hit by lightning will produce a strong transient.Potential,the transient potential of the low-voltage side of the wind turbine box that has not been directly hit by lightning is small;the first lightning strike collector line will generate a strong transient voltage on the high-voltage side of all the turbine boxes of the entire wind turbine group,while the second lightning strike is only suffered The high voltage side of the generator box of a direct lightning strike generates a strong transient voltage.Connecting a surge protector in parallel with the control cable core not only has a better protection effect against the first lightning strike,but also has a significant effect on subsequent lightning strikes;the way of connecting the cable connector in series and grounding one end of the cable shield can effectively reduce both sides of the box transformer Lightning overvoltage,and can effectively reduce the intrusive wave steepness during subsequent lightning strikes.