| Aiming at the problem of the tip corona discharge and the impact of corona particles on the lightning process under the thundercloud electric field environment.This paper adopts a combination of theory and experiment,using the thundercloud electric field generator,establishes a thundercloud-like electric field environment model in the laboratory.Analyzed the electric field intensity threshold of the corona discharge at the metal tip and the corona discharge characteristics under the background electric field environment.And on the basis of the previous experiments,the impulse voltage generator was used to establish a laboratory model to simulate the lightning connection process of the metal tip in the thundercloud electric field environment.The influence of the background particles formed by the corona discharge of the metal tip on the lightning impulse voltage wave was analyzed.The experiment shows:(1)The threshold value of corona discharge trigger electric filed intensity on the metal tip is basically independent of radius of curvature.It is concluded that in the laboratory environment(temperature 20?,pressure 101.2k Pa,air relative humidity30%),the threshold value of the positive corona trigger field intensity is about-9.95 k V/cm,the threshold value of the negative corona trigger field intensity is about+8.80 k V/cm.(2)The positive and negative corona discharge amplitude and discharge repetition rate are positively correlated with the tip electric field strength.After the electric field strength is stronger than a certain value,the discharge amplitude and repetition rate begin to remain stable,then decrease and finally disappear.Positive corona discharge gradually undergoes three typical development processes: no pulse,small number of pulses and suddenness,high pulse repetition rate and periodicity.Negative corona goes through three stages: no pulse,low pulse repetition rate and uniform amplitude,high discharge repetition rate and uniform amplitude.(3)In the same environment,the positive corona discharge pulse amplitude is high,and the discharge repetition rate is about several hundred hertz.The negative corona discharge pulse amplitude is low,and the discharge repetition rate is about several kilohertz.The amplitude of the positive corona discharge is variable and unstable,and the pulse interval is uneven.The amplitude of the negative corona discharge is stable,and the pulse interval is uniform.When the background electrostatic field is the same,the increase in tip curvature radius will weaken the intensity of the distortion,but will increase the range of the distortion,so the amplitude of the positive and negative corona discharge current increases with the increase of tip curvature radius,the discharge repetition rate decreases as the radius curvature increases.(4)The positive corona discharge near the metal tip has an obvious hindrance to the breakdown of the negative lightning impulse voltage.At the most violent moment of the corona discharge,the breakdown time to tip(r=0.05cm)increases by 48.7%compared with the absence of a background electric field,for tip(r=0.25cm)breakdown time increased by 164.5%.The occurrence of negative corona near the metal tip has a weak promotion effect on the breakdown of the negative lightning shock wave,but the effect of shortening the breakdown time is not obvious.(5)When a positive corona discharge occurs near the grounded metal tip,a background of positive ions is formed in the space.The positive ions combine with electrons in the space,reducing the initial electron concentration in the space,thereby hindering the gap discharge;When a negative corona discharge occurs near the tip,a negative ion background is formed in the space.The energy required for the negative ion to dissociate electrons is small,which can increase the initial electron concentration to a certain extent,thereby promoting gap discharge. |
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