Switching impulse strength of air insulation: leader inception criterion

The author introduces a general criterion for leader inception of phase-to-ground air insulation under positive critical switching impulses. This criterion established the correspondence between continuous leader initiation in the vicinity of the highly stressed electrode and conditions prevailing later at the instant of the final jump. The criterion is applied to several complex electrode configurations, including rod-rod, conductor-rod, and conductor-structure gaps, where both analytic and digital techniques are used to compute the leader inception voltage, 50% breakdown voltage, and gap factor. The theory has been systematically tested against available experimental results with quite satisfactory agreement