Properties of creeping discharge progressed in narrow gap between two solid dielectrics in PFAE oil

The behaviors of creeping streamers progressed in a narrow gap between two solid dielectric plates immersed in palm fatty acid ester (PFAE) oil have been investigated using ±1.2/50 μs and ±1.2/1000 μs lightning impulse voltages with ±140 kV_peak in maximum. It is shown that the growth of positive and negative streamers and the flashover voltage are affected by two interfaces between solid dielectrics, the presence of the back side electrode and the wave tail of applied impulse voltages. The temporal progressing processes of the creeping discharges in PFAE oil are observed using a high-speed image converter camera (ICC). These results on the creeping discharge are compared with those in commercial mineral oil.