输电线路覆冰容易造成电气和机械方面的事故，严重威胁电力系统运行的稳定性和安全性。国内外多次大面积的冰灾都引发了输电线路大规模的断线和倒塔，造成了数额庞大的经济损失，影响了人们正常的生产生活秩序。建立完善的导线覆冰模型有助于深入理解覆冰机理，对输电线路覆冰的预测和除冰策略的制定都具有重要的理论和应用价值。然而，大多数现有模型并未考虑导线带电这一因素，模型的预测结果与实际高压线路的覆冰情况仍存在一定差异。本文建立了直流输电线路导线的雾凇覆冰模型，主要工作如下：在水滴荷电量的研究方面，应用任意时刻水滴荷电量的计算公式划分了靠近导线水滴的三个运动阶段。为准确获取相关参数，基于多物理场耦合仿真，建立了直流电晕放电模型，比较了基于Kaptzov假设和基于二阶拟合修正的两种仿真策略。通过对覆冰后导线直流电晕电流的测量，选取了最符合雾凇覆冰条件的粗糙度系数。最终分析了直流导线雾凇覆冰时水滴荷电量的影响因素。计算结果表明，电场强度、水滴大小和风速都会改变靠近导线水滴的荷电量。在水滴碰撞率的影响因素方面，稳态仿真时额外引入了导线周围电场，瞬态仿真时额外考虑了粒子所受的介电泳力和电场力。不同电场强度下碰撞率的计算结果表明，当导线起晕不充分时，介电泳力的吸引作用导致碰撞率的增加；当导线起晕后，电场力的排斥作用导致碰撞率的减小。碰撞率的变化幅度随风速、水滴直径和导线直径的减小而降低。此外，不同绞线结构下的计算结果表明，绞线间存在类似于分裂导线的遮蔽效应。当绞线股数较小时，这种效应随绞线股数和旋转角度的增加呈先增强后减弱的趋势；当绞线股数较大时，碰撞率则接近光滑圆柱表面的情况。降低风速或减小水滴直径能延缓遮蔽效应的出现。在覆冰的建模和试验方面，计算了整体冻结系数作为雾凇覆冰的判据。基于Bain-Gayet冰密度公式，导出了覆冰增长厚度的计算式。比较了拉格朗日多项式法和样条曲线法，选取了高阶多项式作为冰形边界的拟合手段。使用激光粒度分析仪等测量装置和电晕笼等试验装置，在人工气候室内开展了与仿真条件相同的覆冰试验。结果表明，随着电场强度的增加，覆冰形状先向外扩张后向内收缩，覆冰量和覆冰密度都先增大后减小。仿真模型的预测结果与试验结果能很好地对应，验证了直流雾凇覆冰模型的正确性。
Transmission line icing can easily cause electrical and mechanical accidents, seriously threatening the stability and safety of power system operation. Several icing disasters at home and abroad have caused large-scale broken wires and even structural failure of the whole electricity grid, resulting in extremely great economic losses, and affecting the normal the production and life order of society.The establishment of a suitable conductor icing model contributes to better understand the mechanism of icing, which has significant theoretical and practical value for the prediction of transmission line icing and the formulation of de-icing strategies. However, many existing models do not give enough consideration to the energized conductor, and the prediction results are different from the actual icing of high-voltage transmission lines. In this paper, the rime icing model on the DC conductor is established, and the main work is as follows:In the research of water droplet charge, the calculation formula of water droplet charge at any time is applied to divide three movement stages close to the conductor. To accurately achieve relevant parameters, a DC corona discharge model is established based on multi-physical field coupling simulation, and two strategies of Kaptzov hypothesis and second-order fitting correction are compared. Through the measurement of DC corona current of the icing conductor, the roughness coefficient most suitable for rime icing condition is selected. Finally, the influence factors on water droplet charge under rime icing of the DC conductor are analyzed. The calculation results show that the droplet size, electric field strength and wind velocity all change the charge of water droplets near the conductor.With regard to the interfering factor of the collision efficiency, the electric field around the conductor is additionally introduced to the steady-state simulation, and the dielectrophoretic force and electric field force on particles are additionally considered in the transient simulation. The calculation results of the collision efficiency under different electric field strengths show that without sufficient corona discharge, the collision efficiency increases under the attraction of the dielectrophoretic force. After corona discharge, the collision efficiency decreases under the repulsion of electric field force. The amplitude of these changes decreases with the decline of wind velocity, water droplet diameter and the conductor diameter. In addition, the calculation results under different strand structures show that there is a shielding effect between the strands, similar to bundled conductors. When the number of strands is small, this effect first enhances and then weakens with the increase of the number and the rotation angle. When the number of strands is large, the collision efficiency is very close to that of smooth cylindrical surface. Reducing the wind speed or the diameter of water droplets can delay the emergence of the shielding effect.In terms of the modeling and testing of icing, the overall freezing efficiency is calculated as the criterion of rime icing. Based on the Bain-Gayet ice density formula, the ice growth thickness is derived. The Lagrange polynomial and spline curve are compared, and the high-order polynomial is selected as the fitting method of ice shape boundary. Using measuring devices such as laser particle size analyzer and test devices such as corona cage, the icing tests consistent with the simulation conditions are carried out in the artificial climate room. The results show that the icing shape first expands outwardly and then contracts inwardly, and both the icing mass and the ice density first increase and then decrease with the increase of the electric field strength. The predicted results of the simulation model are in good agreement with the experimental results, verifying the correctness of the energized rime icing model.
