He, Jinliang, Yang, Guohua, Li, Quanxin, Zhang, Jianpei, Zhang, Yang, Lyu, Weitao, Fu, Lei, Zhuang, Chijie, and Zhang, Bo
Lightning is the severest threaten to safe operation of wind turbines. In this letter, the authors present the first altitude‐triggered lightning experiment involving an elevated 12 m‐long wind turbine blade placed on the ground. A total of 50 precursors with amplitude over 62.9 A were observed through measurements of channel‐base current, fast electric field, and optical data. The air gap with around 3–5 m has been bridged between the wire's lower extremity and the metal blade tip during ascending of the rocket and it is observed to be luminous by slow framing rate camera. The precursors are classified into three groups, namely bipolar pulses, unipolar pulses, and group pulses. Excluding the precursors preceding the initial stage and M‐components at the late‐time of the initial stage, five stages are classified. In the first stage, the current remains limited at a relatively small value, while the electric field exhibited a slow rising behavior with positive polarity. In the second stage, the current starts to increase, and the electric field rapidly intensifies due to the accumulating charge, and the wire is assumed to experience an explosion. In the third stage, the reconnection process occurs. The current is characterized by a peak value of 1.45 kA with 10%–90% risetime of 10.4 μs. The electric fields suffer from notable decrease and are characterized by a microsecond‐scale V‐shape pulse. The current cutoff is quite short that almost not found. In the fourth step, the current is characterized by superimposed pulses. The final stage is the channel darkening. Observation results are reported in detail about the altitude‐triggered lightning experiment involving an elevated 12 m‐long wind turbine blade placed on the ground. There are fruitful precursors prior to the beginning of the initial stage. The precursors demonstrate that the air gap with around 3–5 m has been bridged between the wire and the metal blade tip. The precursors are grouped into three groups, namely bipolar pulses, unipolar pulses, and group pulses. The initial stage is classified into five periods. The triggering wire is believed to be vapourized during the second stage. The so‐called initial current variation (ICV), also called reconnection process, occurs at the third stage. The superimposed pulses are found immediately after the reconnection process in the fourth stage. The late‐time of the initial stage is also characterized by superimposed pulses associated with M‐components. This work is potentially helpful to understand the physical process lightning strikes a wind turbine, and design lightning protection strategies for wind turbines. First altitude‐triggered lightning experiment associated with an elevated 12 m‐long wind turbine blade has been conducted through simultaneous measurements of current, electric fields and optical dataThe 50 precursors over 62.9 A proceeding the initial stage are classified into three groups: (a) bipolar pulses with the notably initial positive peak and followed by the negative excursion; (b) unipolar pulses with the notably initial positive peak but with quite flat late‐time response; and (c) group pulsesFive stages associated with channel reestablishment are classified according to the measured current and electric field, in which the current cutoff is quite short that almost not found First altitude‐triggered lightning experiment associated with an elevated 12 m‐long wind turbine blade has been conducted through simultaneous measurements of current, electric fields and optical data The 50 precursors over 62.9 A proceeding the initial stage are classified into three groups: (a) bipolar pulses with the notably initial positive peak and followed by the negative excursion; (b) unipolar pulses with the notably initial positive peak but with quite flat late‐time response; and (c) group pulses Five stages associated with channel reestablishment are classified according to the measured current and electric field, in which the current cutoff is quite short that almost not found