Simultaneous measurements of streamer and partial discharge processes in perfluorinated polyether

In this paper, the effect of polarity on prebreakdown phenomena in perfluorinated polyether (PFPE) under nonuniform field was investigated. The inception and propagation of streamers were observed using a high speed and high magnification shadowgraph system. The current pulses were also measured simultaneously using a LED current pulse measurement system. The streamer inception voltage for both polarities were -9.99 kV and +12.86 kV, respectively. The deviation of time delay from the voltage application to the streamer inception was larger for a positive point than a negative. The initial shape of the negative streamer was a filament which emanated from a needle tip. On the other hand, for a positive point, a filamentary streamer started at about 9 μm away from a needle tip, and propagated toward a needle tip. These experimental results suggested that the inception of a positive streamer needs a much higher field than a negative one due to the higher ionization potential of the fluorine atom in PFPE as well as breakdown voltage