The influence of liquid viscosities on bubble breakdown

Insulating liquid, because of high breakdown strength and superior self-recovery property, is widely applied to intense electron beam accelerator, transformer, and superconducting fault current limiters, etc. However, the formation of bubbles caused by heat transfer in power equipment seriously hurts the performance of the insulating strength in liquid. The objective of this paper is to study the influence of liquid viscosity on discharge processes in the presence of bubbles. The effect of bubble size, movement, and burst are also investigated. A high-voltage pulsed source is adopted to generate an electric field between a pair of plane electrode, and then bubbles are injected into the gap filled with dimethicone with different viscosities. The internal and external fields of non-identical distribution cause the deformation of bubbles in the direction of the applied field. Not only that, it can be observed that bubbles may burst without triggering breakdown. Moreover, there are three discharging patterns existing in pre-breakdown and breakdown processes: bush-like shape, cylinder-like shape, and mushroom-like shape. In addition, two possible discharging mechanisms are proposed according to the experiment results.