Lie Ma

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.

While direct current (DC) ice-melting is currently adopted for some transmission lines, its application to 10 kV distribution transformers—often located in remote and rugged terrain—presents significant operational challenges. Disconnecting these transformers prior to ice-melting is a complex procedure that incurs substantial labor, material, and financial costs. Leaving transformers connected risks DC current flowing into idle windings, potentially causing damage. Furthermore, existing mobile DC ice-melting power supplies are bulky and impose stringent transportation requirements, rendering them unsuitable for use on mountain roads. To overcome these limitations, this paper proposes a compact, lightweight variable-frequency ice-melting device. The operating principle and output characteristics of the variable-frequency method are investigated in detail. Using Simulink, system modeling and simulation analyses are performed to obtain the voltage and current output characteristics, along with harmonic spectra. Simulation results demonstrate that the proposed device achieves significant miniaturization compared with conventional solutions: within the typical parameter range of conventional devices, the volume can be reduced by 44–58% and the weight by 43–52%. In addition, the selected LC filter parameters (L = 10.39 mH, C = 86.62 μF) represent an optimized compromise solution that effectively suppresses input harmonics while maintaining the output current total harmonic distortion (THD) within an acceptable limit of 3.6%. Experimental results further validate the feasibility of the variable-frequency ice-melting current. Based on a matrix converter topology, the proposed device enables flexible adjustment of the output melting voltage and frequency, exhibits excellent low-frequency performance and dynamic response, and maintains low output harmonic content—fully meeting the application requirements for variable-frequency ice-melting. The key novelty lies in a compact matrix-converter-based de-icing device with systematic low-frequency performance analysis, offering superior portability and adaptability over traditional DC solutions.