Analysis of Airflow Distribution and Upper Surface Heavily Polluted Areas on Series Double-Column Isolating Switch Insulators for EMUs

When the heavily polluted zones (HPZs) on the leeward side of the high voltage isolating switch insulators (HVISIs) on the high-speed train roof increases, the flashover voltage decreases, thereby increasing the risk of interrupting the train’s power supply. This paper proposes proportion of heavily polluted areas (PHPA) calculation method based on the circumferential angle α, which corresponds to the lowest pressure points, and the circumferential angle β, which corresponds to the boundary layer separation points. The results show that the PHPA for both the upstream insulator (UI) and the downstream insulator (DI) is less than 29.2%. The HPZs on the leeward side of the UI are symmetrically distributed along the flow direction centerline. In contrast, the leeward HPZs of the DI, affected by the wake of the UI, are asymmetrical. The PHPA derived from α is greater than the experimental result, while that obtained from β is smaller than the experimental result. The relative difference between the average value derived from α and β is less than 13.9% compared to the experimental result, the universality of the proposed calculation method was verified with other series double-column insulators. The proposed calculation method can effectively reduce the experimental workload when measuring HPZs, and it can also provide a reference for the preliminary work on structural optimization design for new anti-pollution insulators.