Partial discharge（PD） characteristics of transformer oil contaminated by metallic particles are highly dependent on the motion behaviors of particles. In order to investigate the characteristics of the particle motion in moving transformer oil

a model of solid-liquid laminar two-phase flow was constructed based on the in-depth force analysis of particles

and particle trajectories at different oil flow speeds under uniform DC electric fields were simulated. In order to verify the model

an observation platform of particle motion was built to obtain actual particle trajectories between parallel plate electrodes. The experimental results agreed well with the simulation ones. Both results showed that the particles moved with oil flow in the horizontal direction while moving up-and-down in the vertical direction and colliding with electrodes. In addition

as the oil flow speed increased

the horizontal moving distance for particle sedimentation elongated

and the horizontal moving distance between two adjacent collisions increased. Therefore

the total number of collisions between particles and electrodes decreased

which explained the cause for the decrease of PD numbers with flow speeds.