On the electrical breakdown of gaseous dielectrics-an engineering approach

Quantitative criteria are derived for the onset of breakdown in atmospheric air and similar weakly electronegative gases. A comparable criterion is then formulated for strongly electronegative gases such as SF6. These criteria contain no quantities other than those which can be obtained directly from breakdown voltage measurements in a uniform field, i.e. from Paschen curve data. No specific data are required for the ionizing coefficients of the gas. The advantage, from an engineering point of view, is that it is much easier to perform reliable Paschen curve measurements than it is to measure ionization growth parameters. The price paid is that criteria formulated in this way cannot be used to yield unknown Paschen curves. The criteria can be applied to any nonuniform field configuration provided the electrostatic field distribution is known. Moreover, in many cases a simple analytical approximation to the field distribution can render an extensive calculation of the electrostatic field unnecessary. The discussion deals exclusively with situations in which the onset of breakdown in the system is synonymous with the onset of a corona discharge