Streamer development on silicone-rubber insulator surfaces

Streamers have been generated by application of a pulsed voltage at a point and propagated in a uniform guiding field over silicone-rubber insulator surfaces in ambient air. Two insulator profiles have been used: a simple, smooth cylindrical surface; and a similar surface but with a shed of practical dimensions. Comparison has been made with parallel studies in air alone. Streamer-propagation characteristics were studied, using photomultipliers and photography in the ultraviolet range of the spectrum. The threshold fields required for streamer growth were measured at all three conditions; velocities of growth were measured using three photomultipliers and general spatial characteristics were recorded photographically. The results are discussed in terms of fundamental processes. Comparisons made between the two profiles show that the presence of the shed increases the threshold field needed for propagation; estimates of the energy loss occurring at the shed are made.