Experimental Deformation Characteristics of Water Droplets under Rain-Fog Conditions near Energized Transmission Lines Using a Corona-Cage Setup

To reveal the deformation characteristics of fog droplets under rain-fog conditions near energized transmission lines, a droplet deformation observation platform based on a corona-cage setup was developed, and a coupled laminar-flow, level-set, and electric-field simulation model was also established for comparison. The effects of conductor distance and droplet diameter on the electric-field distribution and deformation characteristics were systematically investigated. The results show that in the near-field region (0–300 mm from the conductor), the electric field strength at the droplet center is approximately 0.2 kV/cm higher than that in the surrounding region. In the far-field region (300–500 mm), the electric field around the droplet decays rapidly, with the field strength at the droplet center decreasing by 90.6% and that on the droplet surface decreasing by 86.2%. As the droplet approaches the conductor, it exhibits radial elongation and axial contraction. At a distance of 20 mm from the conductor, the deformation ratio reaches 2.89, and severe electric-field distortion occurs at the droplet tip, which can easily induce corona discharge and surface flashover. Increasing the droplet diameter causes the central electric field strength to decrease linearly, while the deformation ratio increases linearly. The experimental results agree well with the simulation results regarding droplet deformation characteristics and electric-field distribution. This study provides theoretical support and experimental evidence for optimizing external insulation design and suppressing corona discharge on transmission lines under rain fog conditions.