电弧形态对雷电流光辐射强度观测的影响

Effect of arc channel shape on observation of lightning luminosity

光学手段进行雷电流电弧光辐射强度探测过程中,光强波形往往会出现畸变。利用高压实验室内冲击电流发生器模拟产生回击和连续电流两种雷电流分量,分别流过石墨电极构成的空气间隙,探究了不同电极形状和不同电极烧蚀程度下的电弧形态差异,使用通道光强探测系统同步观测电弧通道对应光辐射强度。研究结果表明,平面电极相较于曲面电极更容易产生扭曲的电弧,电极表面烧蚀也会扩大电弧通道的扭曲程度,这种形态的扭曲导致了光辐射强度波形产生畸变,具体表现为模拟回击电流光强波形中出现“驼峰”和幅值波动,以及模拟连续电流对应光强波形在平坦期向下凹陷。本文对雷电流光辐射强度观测的畸变波形成因进行了阐释,为提高光学测量手段精确性、进一步掌握雷电流发展过程和相关参数提供了依据。

A distortion has often been observed in the waveform of luminosity emitted by the lightning channel through optical means. The impulse current generator in high voltage laboratory was used to simulate two types of lightning current components(return stroke and continuing current) flowing through the air gap composed of graphite electrodes. The differences of the arc channels under the case of different electrode shapes and different electrode ablation degrees were investigated. The luminosity characteristics of the simulated lightning arc channels were synchronously observed through the lightning channel luminosity detection system. The obtained results indicate that the planar electrode is more prone to producing the distorted arc channel than does the curved electrode, and the surface ablation of the electrode can aggravate the distortion of the arc channel. Moreover, this distortion of lightning arc channel will, more or less, result in distortion of lightning luminosity waveform. The distortion in channel luminosity waveform corresponding to the simulated return-stroke current is featured with the ‘hump’ and also with the amplitude fluctuation, whereas for the simulated continuing current, its channel luminosity waveform exhibits the sag in the flat period. A reasonable interpretation for the origin of the distorted luminosity waveform was given. Results here can provide a basis for improving accuracy of optical measurement and, possibly, further for understanding the development process of lightning current.