A comparative presentation of sphere gaps and sphere - rod gaps understandard lightning impulse voltages

摘要

The present paper is a report of anrnexperimental work concerning the breakdown ofrnsphere – rod air gaps aiming to supplement the datarnalready available in the literature. The differencesrnbetween both the sparkover voltages and thernbreakdown mechanisms of rod – rod and rod – planerngaps suggest that the examination of sphere – rodrngaps, an intermediate gap configuration in terms ofrnelectric field uniformity, could be of interest.rnEspecially if any of them could be used for calibratingrnand/or measuring purposes replacing the morernexpensive sphere gaps. The influence of gap spacingrnand polarity on the sparkover voltage of sphere - rodrngaps has been investigated under standard lightningrnimpulse waveshapes. Furthermore, as with sphererngaps, irradiation was used for values of the S/D ratiornless than 0,2 in an attempt to decrease the scatter ofrnthe measured values. Also, a comparison in thernbreakdown processes between sphere - rod and sphererngap systems is presented taking into account variousrnpertinent parameters. Eventually, it was consideredrnnecessary to investigate the impact of absoluternhumidity on the breakdown voltage and to calculaternhumidity correction factors.