Abstract
The streamer is the main process in an air gap discharge, and the inception characteristics of streamers have been widely applied in engineering. Streamer inception characteristics under DC voltage have been studied by many researchers, but the inception characteristics under impulse voltage, and particularly under lightning impulse voltage with a high voltage rise rate have rarely been studied. A measurement system based on integrated optoelectronic technology has been proposed in this paper, and the streamer inception characteristics in a 1-m-long rod-plane air gap that was energized by a positive lightning impulse voltage have been researched. We have also measured the streamer inception electric field using electrodes with different radii of curvature and different voltage rise rates. As a result, a modified empirical criterion for the streamer inception electric field that considers the voltage rise rate has been proposed, and the wide applicability of this criterion has been proved. Based on the streamer inception time-lag obtained, we determined that the field distribution obeys a Rayleigh distribution, which explains the change law of the streamer inception time-lag. The characteristic parameter of the Rayleigh distribution lies in the range from 0.6 to 2.5 when the radius of curvature of the electrode head is in the range from 0.5 cm to 2.5 cm and the voltage rise rate ranges from 80 kV/μs to 240kV/μs under positive lightning impulse voltage.
Highlights
The streamer is the main process in an air gap discharge, and streamer inception characteristics have been widely used in engineering.[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]
Under positive lightning impulse voltage, two conditions need to be satisfied for the streamer inception: the applied voltage reaches the minimum voltage for the streamer inception at least; the effective free electrons exist in the space
A(x)Rayleigh and D(x)Rayleigh are both proportional to μ, and when μ increases, A(x)Rayleigh and D(x)Rayleigh both increase. This indicates that the mean and the dispersity of the streamer inception time-lag both increase; i.e., when the frequency of appearance of the effective free electrons decreases, both the mean and the variance of statistical time-lag for the appearance of the effective free electrons increase, which means that the mean and the dispersity of the streamer inception time-lag increase
Summary
The streamer is the main process in an air gap discharge, and streamer inception characteristics have been widely used in engineering.[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18] The inception characteristics of streamers under DC voltage have been widely researched,[6,7,8,9,10,11,12] but these inception characteristics under impulse voltage and under lightning impulse voltage with a high voltage rise rate have rarely been studied. Many relevant research studies and results for the streamer inception electric field criterion under DC voltage have already been published.[19,20,21,22] Under a positive DC voltage, the streamer originates at the electrode at which the ionization coefficient α is equal to the attachment coefficient η. When compared with the streamer inception conditions under DC voltage, streamer initiation under positive impulse voltage must meet two conditions: first, under the action of an impulse voltage, the applied voltage on the electrode or the electric field on the electrode tip should produce the streamer inception voltage U0 or field E0; second, it is essential to ensure that free electrons appear at the head of the rod electrode. The streamer inception characteristics in a 1-m-long rod-plate air gap under positive lightning impulse voltage have been studied experimentally. The streamer inception time-lag distribution under lightning impulse voltage was demonstrated to be a Rayleigh distribution, and the variation law of the streamer inception time-lag is explained on this basis
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