Investigation of partial discharges in SF6 using a computer-based data acquisition system

Investigations aimed at developing a new method of testing SF₆ gas, from a gas insulated substation (GIS), for impurities is described. The method involves observation and analysis of the properties and characteristics of corona discharge produced when an SF₆ sample is subjected to the nonlinear electric field of a point-plane test geometry. These properties are sensitive to the presence of impurities and analysis of the discharges should provide information which allows some estimation of the impurity, perhaps even species and concentration. Preliminary to such development, a number of experiments involving partial discharge (PD) recording and analysis in SF₆ samples contaminated by moisture are described. The results of the experiments indicate that statistical analysis of the data may provide possible means of impurity evaluation