Voltage-Time Characteristics of Particle-Initiated Impulse Breakdown in SF6 and SF6-N2

The paper comprises a theoretical and experimental investigation into the impulse breakdown voltage-time characteristics of a spherical- particle-contaminated coaxial-cylinder gap in compressed SF6 and SF6-N2 mixture. The experimental work was carried out on a 25/70-mm diameter coaxial-cylinder gap with a 3.2-mm spherical particle attached to the high-voltage electrode, at a gas pressure of 0.3 MPa under 0.5/50-??s and 1.2/50-??s impulses of both polarities. Whenever possible the results were compared to those previously obtained on a clean system from which the particle effect on impulse breakdown voltage and delay time was identified.