Effects of Chain Length on Prebreakdown Phenomena in Straight-chain Saturated Hydrocarbon Liquids

Abstract

Prebreakdown light emission, current and streamer in straight-chain saturated hydrocarbon liquids, n-pentane, nhexane, n-heptane, n-octane, n-nonane, and n-decanne, are investigated under non-uniform field conditions.
The light inception voltage and the breakdown voltage increase with the chain length, the liquid's density For a negative point, the breakdown voltage is much higher than the light inception voltage in all liquids but the difference between those decreases against the chain length. This voltage difference is not observed for a positive point except in n-pentane and n-hexane. The difference between the negative and the positive breakdown voltages decreases against the chain length. Regarding to the polarity effect, the negative breakdown voltage is much higher than the positive one in n-pentane, but there is no difference in n-decane.
A negative density change streamer has a bush like structure and propagates with stepped manner having an average speed of 70-160m/s, while for a positive one, the structure is a tree-like having an average speed of a few km/s. Only in n-pentane and n-hexane, a slow positive bush-like streamer is observed whose average velocity is about 200m/s, which is slightly faster than the negative bush like one.