Investigations of corona discharge in SF6 using a computer-based data acquisition system

Describe investigations aimed at developing methods of testing SF ₆ gas from GIS (gas-insulated switchgear) for impurities. The method involves observation and analysis of partial discharge (PD) properties of corona produced when the SF₆ sample is subjected to the nonlinear AC electric field of a point-plane test geometry. The PD properties are quite sensitive to the presence of impurities and, thus, analysis of the discharges should provide information which allows some estimation of the impurity, perhaps even species and concentration. As a preliminary to such development the authors describe a number of experiments involving PD recording and analysis in SF₆ samples contaminated by moisture. The results of the experiments (recording phase angle and magnitude of discharges) indicate that statistical analysis of the data may provide a possible means of impurity evaluation