Surface flashover of dielectric materials used in pulsed power research

Selection procedures for insulators used under high-voltage/high-current pulsed power conditions are not well defined, and insulator failure has occurred in large pulsed power facilities when the materials were selected based on experience with low frequency systems. For the latter systems, reliable design rules and procedures have been validated for applications under DC and power frequency conditions (50/60 Hz and 400 Hz in aircraft applications). A preliminary investigation of solid dielectric material behaviour under high dE/dt conditions in transformer oil has been undertaken. A 10-stage Marx generator, capable of producing output voltages in the region of 750 kV, was used in conjunction with an adaptable test assembly to determine the flashover properties of different materials. Results on the behaviour and ageing of solid insulators are reported, along with hold-off voltage performance and degradation due to surface discharges.