Breakdown Streamers in Coronas with Heated Discharge Electrode

Experiments have been carried out on a wire-tube corona apparatus to measure the breakdown voltage and the maximum prebreakdown corona current with and without heating the discharge electrode. Positive and negative polarities were employed on discharge electrodes of different diameters in clean air at room temperature. The results showed that the triggering of the break- down streamers, and hence the breakdown characteristics, are affected appreciably by the temperature of the discharge electrode in positive corona. In the negative corona, however, the breakdown characteristics were found to be practically independent of the temperature of the discharge electrode. Interpretation of these results indicate that the triggering mechanism of the breakdown streamers in the positive corona is mainly dependent upon the physical nature of the local breakdown in the vicinity of the discharge electrode; in particular, it is dependent upon the ion space charge density distribution in this localized region. In the negative corona, however, the electric field and its gradient in the vicinity of the outer electrode are the main factors governing the breakdown condition. The negative streamers, initiated from the vicinity of the discharge electrode, normally called "Feathers", have a negligible effect.