Assessment of air‐density correction for practical electrode systems

Abstract

A survey is given of available data on the effects of air density upon pre-discharges and sparkover f o r nonuniform Feld geometries under a variety of voltage waveshapes of both polarities. Semi-empirical relationships describing the trends of the experimental data are presented The correction methods set up by the IEC are reviewed and some emphasis has been given to the need to distinguish between the separate influences of pressure and temperature in the overall air-density Correction factors. The limits of applicability f o r density correction are also discussed. Finally. a generalised semi-empirical equation raking into account the main atmospheric variations is proposed. This is shown to offer a good accuracyfor the calculation of sparkover voltages over a wider densitv range thon has been hitherto been possible.

Étude numérique et expérimentale pour déterminer le champ électrique d'apparition des décharges couronnes à l'aide de la configuration d'électrodes tige-plan =

“…It is well known that the field non-uniformity factor of a hemispherically capped rodplane gap depends primarily on the ratio of the gap length to the radius of curvature of the rod tip [17][18]. However, there are other factors which affect the field factor, i.e.…”

“…The problem arises with the fact that the effect of air density seems to be dependent on the combination of air pressure and temperature and the only feasible way to perform the tests is keeping one parameter constant, while varying the other. This leads to different results achieved by different researchers [18]. Not to mention the fact that humidity levels are affected by air temperature as well.…”

“…The subject of the last category is generally on the effect of atmospheric parameters variation on the breakdown voltage in rod-plane gaps [18] [22][23] [28] [33][34][35][36][37][38][39]. All these studies have demonstrated that the IEC correction method [20] has many setbacks and can not be globally applied to all electrode configurations and voltage shapes.…”