Bubble Dynamics and Migration Mechanism in Insulation Oil Under Extremely Inhomogeneous Electric Field

The existence of bubbles in transformer oil is easy to cause partial discharge, resulting in the deterioration of insulating oil. In order to clarify the migration and distortion law of bubbles under the action of complex electric field in oil immersed power equipment, the dynamic characteristics of bubbles in insulating oil under extremely inhomogeneous AC electric field were observed by using experimental methods, and the migration path, rate and distortion degree of bubbles under different field intensities were analyzed by means of numerical simulation. The results show that the electric field force can stretch and push away the bubbles, and accelerate the upward movement of the bubbles, especially for micron bubbles; the stretching direction of the bubbles is always parallel to the direction of the electric field. When the field strength is large enough, the small bubbles will rise in pairs, which will increase the enhancement effect on the electric field. The field strength enhancement coefficient at the interface of "bubble pair" can reach 2.28, making it easier for partial discharge to occur inside the bubbles, which should be paid attention to in equipment design and operation. The experimental and simulation results are basically consistent, which verifies the rationality of the simulation model. © 2022 Chin. Soc. for Elec. Eng.