Electro-optical Measurement of Prebreakdown Current and Breakdown Time Lag in Polyethylene using Nano-second Rectangular Pulse Voltage.

Abstract

The electrical breakdown phenomena in polyethylene for point-to-plane electrode configuration has been investigated using a photo optical current measuring technique and a 760 nano-second rectangular high-voltage pulse generator. The wave forms of the prebreakdown current in polyethylene were essentially the same as those in liquid dielectrics. Discharge from positive point was more intense and faster than that from negative point in longer gap spacing. A linear relation to formative time lag and gap spacing was observed for gap length more than some critical values, which indicate a constant propagation velocity in this region. The velocities are deduced to be 1.7km/s for positive point of 50kV and 0.38km/s for negative 60kV. These values are coincident with those of liquid dielectrics. A new concept of breakdown model involving polarization effect is proposed.