雷电定位系统反演地闪回击电流的准确度受回击速度取值的影响

Effect of Lightning Return Stroke Speed on Accuracy of Inversed Return Stroke Peak Current Using Lightning Location System

目前国内外广域雷电定位系统在反演地闪回击电流时,一般设定回击速度为1×10^(8) m/s至2×10^(8) m/s之间的某一固定值,该文探讨了这种取值方式对回击电流反演准确度的影响。首先,介绍了利用雷电定位系统反演地闪回击电流的方法,分析了地闪回击速度对雷电定位系统反演回击电流的重要影响。其次,基于Lundholm等人提出的负极性回击电流与回击速度之间的关系式,分析了对于负极性首次回击,25 kA以下回击电流可能被低估,160 kA以上回击电流可能被高估;对于负极性后续回击,5 kA以下回击电流可能被低估,32 kA以上回击电流可能被高估。然后,回顾和总结了4种回击(负极性首次回击、负极性后续回击、正极性首次回击和正极性后续回击)的速度观测结果,认为在雷电定位系统中有必要区别对待各种类型的回击来进行回击电流的反演。最后,从个例角度比较了中国电网雷电地闪定位系统反演回击电流与人工引雷和输电铁塔实测回击电流;基于2012—2019年在武汉获取的大样本数据,对比了系统反演回击电流的累积概率分布曲线和IEEE推荐的曲线。结果表明,总体上中国电网雷电定位系统可以较好反演地闪回击电流,对于负地闪后续回击可能存在一定程度高估,这可能与系统设置的回击速度比实际偏小有关。

At present,the return stroke speed is generally set to some fixed value between 1×10^(8) m/s and 2×10^(8) m/s when the nationwide lightning location systems are used to invert Cloud to Ground lightning return stroke currents.In this paper,the impact of adopting this method on the accuracy of the return stroke current inversion is discussed.Firstly,the method of using the lightning location system to invert the return stroke current is introduced,and the important influence of the speed of the return stroke on the peak current is analyzed.Secondly,based on the relationship between the negative return stroke current and the return stroke speed proposed by Lundholm et al.,the analysis on the negative first return stroke reveals that the return stroke current below 25 kA may be underestimated,and the return stroke current above 160 kA may be overestimated.For negative subsequent return strokes,the return stroke current below 5 k A may be underestimated,and the return stroke current above 32 kA may be overestimated.Then,the return stroke speed observation results of negative first return strokes,negative subsequent return strokes,positive first return strokes and positive subsequent return strokes are summarized.It is believed that it is necessary to treat various types of return strokes in the lightning location system differently.Finally,for individual cases,the inversed return stroke currents and those measured from artificially triggered lightning and transmission towers are compared.Based on large samples obtained in Wuhan from 2012 to 2019,the cumulative probability distribution curve of the system inversed return stroke currents and the curve recommended by IEEE are compared.It is considered that the lightning location system of China’s power grid can retrieve reasonable return stroke currents,though the peak current of negative subsequent return strokes may be overestimated to a certain extent,which may be related to the fact that the return stroke speed set by the system is smaller than the actual value.