Corona Discharge Studies in SF6 with Insulators under Positive Switching Impulses

Corona discharge currents and corona inception time delays have been measured in SF6 with an insulating support under positive switching impulses. The insulator surface charging is found to have a significant influence on the corona discharge phenomena. Cumulative probability distribution function of the number of corona pulses is found to depend upon the insulator material and gas pressure. Based on the experimental results, the calculated corona inception time delay distribution with an insulator is found to fit into a log-normal distribution. The influence of insulator on electron initiating mechanism is analyzed using Von Laue diagrams for the corona time delay. The effect of gas pressure and the applied voltage on the inception time delay and pulse current with an insulator in the gap is discussed.