Formation Mechanism and Optimization Method of Streak-Shaped Pollution for the Roof Insulator of EMUs

Roof insulators are one of the key pieces of equipment to ensure the electrical safety of high-speed railways (HSRs). When the umbrella skirt of a roof insulator is seriously polluted in various environments, the risk of pollution-induced flashover rises. Field experience shows that the flashover possibility of roof insulators in coastal intercity railways is much higher than that in other regions. However, the pollution characteristics of roof insulators under those conditions are still unclear. In this work, we investigated the pollution characteristics of roof insulators used in the coastal intercity railway of electric multiple units (EMUs) of China. Aspects of the pollution spatial distribution, the statistical content, and the pollution constituent on the surface of the umbrella skirt of insulators are taken into account. The airflow field and electric field distribution around the pantograph support insulator (PSI) are also simulated based on finite element software. To reduce the formation of streak-shaped pollution, the umbrella skirt is optimized by the streamlined structure. The results indicate that a novel phenomenon of streak-shaped pollution distribution might form on the surface of the insulator, which would severely aggravate the distortion of electric field distribution. The calculated turbulence dissipation rates are found to spatially agree well with the streak-shaped pollution distribution. The streamlined structure effectively reduces the turbulence dissipation rate at the junction of the windward and leeward surfaces, to inhibit the formation of streak-shaped pollution.