Impulse Creeping Streamer and Propagation Velocity in Vegetable and Mineral Oils with Pressboard Interface

This paper presents an experimental study on the creeping discharge propagating over the pressboard surface in two vegetable oils(PFAE(palm fatty acid ester)oil and CRS(crude rapeseed)oil)and commercial mineral oil under the quasi-square impulse voltage with any pulse width.The pressboard impregnated with the sample oil is immersed completely into the same oil.The tungsten needle electrode is installed in the pressboard surface with and without the counter electrode to generate a creeping discharge.The other side of pressboard has the thin copper rod as a back side electrode.A comparison of the shape and stopping length of positive and negative streamers,discharge current,emitted light signal,and temporal variation and velocity of streamer propagation is reported for all different oil-pressboard interfaces.It has been shown that the behavior of creeping streamers has unique characteristics and polarity effects,and the traveling mode and propagation velocity of streamers are greatly different depending on the type of oil.