Influence of irradiation on impulse breakdown of sphere gaps and sphere-rod gaps

The influence of irradiation on the breakdown of sphere and sphere-rod gaps for short gap spacings, has been investigated under standard impulse waveshapes of both polarities. It is known that, for short gap spacings, in nonirradiated sphere gaps and sphere-rod gaps the values of the standard deviations of the breakdown probability distributions are relatively large, and the same is true for the influence of humidity on the sparkover voltage. However, the experiments showed that irradiation acts interactively with other discharge parameters, i.e. impulse shape, gap spacing, polarity, absolute humidity, diameter of the spheres and the shape of the earthed electrode. It was found that the breakdown mechanism of small gaps is influenced by irradiation and that the irradiated gaps in most cases become more reliable for measuring and/or calibrating purposes