气流环境对直流沿面电荷消散特性及其动力学过程的影响

Influence of Airflow Environment on the Charge Dissipation Characteristics and Dynamic Process of Direct Current Along the Surface

高速列车车顶绝缘设备,在气流环境中会与粉尘、金属颗粒等微小颗粒发生摩擦、碰撞带电,并在其表面形成表面电荷,引发沿面放电现象,严重时将威胁列车供电稳定性。为研究气流环境对表面电荷消散特性的影响,搭建气流环境表面电荷积聚试验平台,测量不同气流速度下表面电荷的消散规律。对气流环境表面电荷传导机制以及表面电荷脱陷/入陷动力学过程进行讨论,结果表明:气流环境会使得表面电荷消散加速,且气流速度越大,消散越快。气流环境下表面电荷消散主要受到气体侧复合以及介质表面薄层传导消散机制的影响,随着气流速度增大对于气体侧复合传导机制而言,减小的空气密度导致气体分子的平均自由程增大,使得空气中离子的迁移率以及离子浓度增大,从而加剧了表面电荷通过气体侧复合消散的速率;对于介质表面薄层传导而言,气流会摩擦绝缘介质表面造成温升,影响了载流子的入陷/脱陷过程,主要表现为陷阱捕获截面减小,载流子脱陷概率增加,同时随着气流速度增加,陷阱能级中心不断前移,陷阱能级减小,使得载流子更容易脱陷。

Insulation equipment on the roof of high-speed trains will cause frictional charging and collision charging with fine particles such as dust and metal particles in the airflow environment, and form surface charges on their surfaces, causing surface discharge phenomena, which will threaten the stability of train power supply in severe cases. In order to study the influence of the airflow on the surface charge dissipation characteristics, a test platform for surface charge accumulation in the airflow environment was built, and the dissipation law of surface charge under different air flow speeds was measured. The mechanism of surface charge conduction in the airflow environment was discussed. The results show that the airflow environment will accelerate the dissipation of surface charges, and the greater the airflow velocity, the faster the dissipation. The surface charge dissipation under the airflow environment is mainly affected by the gas-side recombination and the thin-film conduction dissipation mechanism on the surface of the medium. As the airflow velocity increases for the gas-side neutralization conduction mechanism, the reduced air density leads to an increase in the average free path of gas molecules and the ion mobility and ion concentration in the air increase, which intensifies the rate of surface charge neutralization and dissipation through the gas side. For the thin layer conduction on the surface of the medium, the air flow will rub the surface of the insulating medium and cause a temperature rise, which affects the trapping/detrapping process of the carrier. It mainly shows that the trap capture cross-section decreases, and the probability of carrier detrapping increases. As the airflow speed increases, the depth of the trap level continues to decrease, making carriers easier to detrap.