High-speed schlieren studies of electrical breakdown in liquid hydrocarbons

Although numerous theories have been proposed to explain breakdown in dielectric liquids, a unified understanding of its origin is still lacking. Measurements of such breakdowns are difficult because it is an ultrafast transient event, lasting only nanoseconds. Within that time, quantities of interest such as conduction current can change from milliamperes to tens of thousands of amperes. Moreover, even by taking extreme precautions such as using isolation transformers and well-shielded cables, the electromagnetic radiation associated with breakdown can strongly disturb electronic equipment. Such problems pose great difficulties for investigation of electrical breakdown events based on electrical measurements. In the present study, an optical method based on a laser-schlieren system was used and the spatial development of electrical breakdown in liquid hydrocarbons was recorded photographically.