Electro-optic precursors of critical transitions in dielectric liquids

Motivated by the search for approaches to non-destructive breakdown test and impurity detection in dielectric liquids, we explore the possibility of early warning of breakdown initiation in high voltage pulsed transformer oil from the data of Kerr electro-optic measurements. It is found that the light intensities near the rough surfaces of electrodes both fluctuate in repeated measurements and vary spatially in a single measurement. We show that the major cause is electrostriction which brings disturbances into optical detection. The calculated spatial variation has a strong nonlinear dependence on the applied voltage, which generates a precursory indicator of the critical transitions. (C) 2014 AIP Publishing LLC.