直流均匀电场下流动变压器油中金属微粒运动行为研究

Motion Behaviors of Metallic Particles in Moving Transformer Oil Under Uniform DC Electric Fields

含金属微粒污染物变压器油的局部放电(partial discharge,PD)特性取决于微粒的运动行为。为了研究流动变压器油中金属微粒运动特性,在深入分析微粒受力的基础上,构建了基于层流状态的固–液两相流模型,仿真了直流均匀电场中不同油流速度下微粒的运动轨迹。为验证模型的正确性,搭建了金属微粒运动观测平台,获得了不同流速下平行板电极之间微粒的真实运动轨迹。实验结果与仿真结果相一致,二者均表明微粒在水平方向随着油流运动的同时,在竖直方向上下往复运动并与电极发生碰撞。此外,随着油流速率增加,微粒沉降过程所需的水平移动距离变长,相邻2次碰撞间的水平移动距离增加,导致了微粒与电极之间总的碰撞次数将减少。这解释了PD次数随油流速度减少的原因。

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.