Inhomogeneous Field Breakdown in GIS - The Prediction of Breakdown Probabilities and Voltages Part I: Overview of a Theory for lnhomogeneous Field Breakdown in SF6

Inhomogeneous field breakdown in SF6 has been investigated, and a theory has been developed which predicts the breakdown voltage for fast rising (rectangular) waveforms applied to arbitrary electrode geometries and gas pressures. This theory facilitates the analytical design of aspects of many GIS components where previously engineering judgement and development testing were necessary. An analytical approach is both more economic and more reliable. Extensions of the theory, presently underway, will permit breakdown voltage prediction for arbitrary surge waveform, which will facilitate the assessment of test waveform efficacy and the development of more reliable field, factory, and type tests. The present paper is intended to summarize this research in a form relevant to the working power engineer.