Characteristic of Impulse Grounding Resistance of a Grounding Grid by Triggered Lightning Flash
In this paper,based on the triggered lightning technique,the impact of impulse grounding resistance was studied for 44 return strokes,5 initial continuous current pulses(ICCP),and 24 M-components of eight triggered lightning events that occurred in the summer of 2019.The goal of the study was to explore the dynamic variation of impulse grounding resistance with lighting current injection.It was found that the impulse grounding resistances of the ICCP,M-component and return stroke were lower than that of the DC grounding resistance,while those of the ICCP and M-component superimposed on continuous current after the return stroke were slightly higher than that of the return stroke,with respective average values of 11.2 Ω and 10.8 Ω.Moreover,the average value of impulse grounding resistance in the M-component superimposed on the falling edge of the return stroke was 7.8 Ω,which was clearly a smaller return stroke,and the minimum value reached up to 2.4 Ω.The impulse grounding resistance of the ICCP and M-component decreased with the increase of lightning current,and there was no obvious correlation with the current peak of the return stroke.Finally,the impulse grounding resistance of the M-component superimposed on the falling edge of the return stroke decreased exponentially with the increase of the current peak and background current value and was inversely proportional to the current peak of the return stroke.The impulse grounding resistance exhibited a dynamic change process with the injection of lightning current.After the current peak decrease of the return stroke,it increased slowly in the small current and decreased rapidly in the large current.The effects of spark and inductance differed in the varying physical processes of lightning,and both determined the ionization degree of soil,which in turn determined the magnitude and variation of the impulse grounding resistance.
artificially triggered lightningreturn strokeinitial continuous current pulseM-componentimpulse grounding resistance
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