Effect of Humidity on the Spark Breakdown Voltage

Abstract

THE influence of water vapour on the breakdown voltage of uniform field gaps has been investigated by Ritz¹. He found that the breakdown voltage of a 1-cm. uniform field gap at 760 mm. mercury pressure in air increased by 2 per cent for a change in the partial pressure of water vapour from 10 to 25 mm. mercury. More recently, Köhrmann² has published results which indicate that the presence of water vapour at 10 mm. mercury raised the breakdown voltage by 2.7 per cent above that of dry air at 760 mm. mercury. Lewis³ investigated the humidity effect for sphere gaps and quoted an increase of 0.13 per cent in voltage for each mm. mercury of water vapour. This value is rather low compared with the two other results and may be due to the fact that he used a gap of 0.4 cm. between 2-cm. spheres.