Prebreakdown current and breakdown propagation velocity in polyethylene under a highly nonuniform field condition

Abstract

The electrical breakdown phenomenon in polyethylene for point-to-plane gap configurations has been investigated using a photo-optical current-measuring technique and a 760 ns rectangular high-voltage pulse generator. The waveform of prebreakdown current in polyethylene is essentially the same as those in liquid dielectrics. Discharge from a positive point is more intense and faster than that from a negative point. A linear relation to formative time lag and gap spacing is obtained for gap lengths greater than some critical value, indicating a constant propagation velocity in this region. The velocities are deduced to be 1.7 km s-1 for a positive point at 50 kV and 0.38 km s-1 for a negative point at 60 kV. These values are coincident with those of liquid dielectrics.