高速气流对针板沿面直流放电特性的影响

Effect of High-speed Airflow on the Surface DC Discharge Characteristics of the Needle Plate

暴露在大气环境中的绝缘设备受到运行状态或者大气运动的影响,其绝缘介质表面往往处于气流环境中,其放电特性与静态气体相比有较大差异。以硅橡胶绝缘片为研究对象,通过风洞系统开展气流环境下绝缘介质表面闪络特性试验,发现气流方向垂直于电场方向时,电晕放电光区与放电路径沿着气流方向发生了偏移。分析气流环境下绝缘介质表面、气体薄层和气体中离子的运动轨迹变化,认为气流导致离子的运动轨迹发生偏转,并使得大量电子和离子被吹离绝缘介质表面,绝缘介质表面电子和离子浓度下降,这就削弱了流注头部的电场,使流注的发展变得困难。同时,气流环境导致绝缘介质表面电荷积聚途径与来源发生变化,随着气流速度的增加,绝缘介质表面电荷消散速率增快,绝缘介质表面法向电子通量与切向电子通量都减小,导致表面电荷累积量减少,进而削弱了绝缘介质的表面电场。电子的偏转和吹离效应以及表面电荷积聚量减少是导致高速气流环境下针板电极间沿面闪络电压上升的主要因素。

Insulating equipment exposed to the atmosphere is affected by operating state and atmospheric motion.The surface of the insulation medium is often in an airflow environment,and its discharge characteristics will vary greatly from those in the static air.In this paper,the silicone rubber insulation sheet was taken as the research object.The surface flashover characteristics of the insulation medium in the airflow environment were tested by the wind tunnel system.It is found that the corona discharge light region and the discharge path are offset along the airflow direction when the airflow direction is perpendicular to the electric field direction.The trajectory changes of particles in the insulation medium surface,gas thin layer and gas under airflow environment were analyzed.It is considered that the airflow causes the trajectory of the particles to deflect and causes a large number of electrons and particles to be blown off the insulation medium surface,so that the concentration of electrons and particles on the insulating medium surface decreases,which weakens the electric field of the steamer head and makes the development of the steamer more difficult.At the same time,the airflow environment changes the way of charge accumulation on the insulation medium surface and the source of charge.As the airflow velocity increases,the charge dissipation rate on the insulation medium surface increases,and the normal and tangential electron fluxes on the dielectric surface decrease,resulting in the decrease of surface charge accumulation,which weakens the surface electric field of the insulation medium.The deflection and blow-off effects of electrons and the reduction of surface charge accumulation are the main factors leading to an increase in the flashover voltage of the pinhole electrode under a high-speed airflow environment.