直流绝缘子带电自然覆雪形成机理及其放电发展过程的模型化研究

Long-term research and exploration on snow-covered insulator have been carried out in the climate chamber at home and abroad, but there is a big difference between manual test and field test, which has caused the flashover problem of snow-covered insulator that remains unsolved. This project intends to use the numerical simulation calculation and field test to study the physical process of the natural snowfall accretion on DC insulator and its discharge development characteristics. The research includes: (1) Analyzing the stress of wet snow particles in electric field and flow field, studying the motion law of particles, and proposing the conditions of collision and accumulation of particles on the surface of insulators based on the theory of collision dynamics to establish the snow-covered growth model for insulators. (2) Building the equivalent physical model of discharge cell based on the principle of arc current and arc temperature equivalence, and studying the volt-ampere characteristics, temperature characteristics, dynamic characteristics of arc and dynamic resistance characteristics of residual snow layer to establish the time domain models of arc and residual snow layer. (3) Characterizing the coexistence of “multi-arc, multi-snow-layer” in the flashover process of snow-covered insulators with air gap arc, creeping arc and residual snow layers not bridged by arc, establishing a physical mathematical model of discharge and proposing critical flashover conditions and flashover criteria. The research work of this project can provide a certain degree of theoretical support for promoting the research of snow-covered insulator from manual test to numerical simulation.

国内外在人工气候室对绝缘子覆雪开展了长期的研究和探索，但人工试验与现场试验之间存在较大的差异，导致绝缘子雪闪问题尚未解决。本项目拟采用数值仿真计算和现场试验相结合的方法研究直流绝缘子带电自然覆雪的物理过程及其放电发展特性。研究内容包括：（1）分析湿雪颗粒在电场和流场中的受力情况，研究颗粒的运动规律，基于碰撞动力学理论，提出颗粒在绝缘子表面碰撞积聚的条件，建立绝缘子覆雪增长模型；（2）基于电弧电流、电弧温度等效性原则，搭建放电单元的等效物理模型，研究电弧的伏安特性、温度特性和动力学特性以及剩余雪层的动态电阻特性，建立电弧和剩余雪层电阻的时域模型；（3）以空气间隙电弧、沿面电弧和未被电弧桥接的剩余雪层表征覆雪绝缘子闪络过程中“多电弧-多雪层”并存的特征，建立放电的数学物理模型，提出临界闪络条件和闪络判据。本项目研究工作可为推动绝缘子覆雪研究由人工试验向数值模拟方向发展提供理论支持。

人工气候室获得的绝缘子覆雪增长、放电发展过程和静态闪络模型并不能有效地反映绝缘子自然覆雪的规律与动态闪络的本质。本项目采用数值仿真计算和现场试验相结合的方法，针对直流绝缘子覆雪增长数值模拟方法、电弧动态发展特性和覆雪绝缘子闪络动态模型展开了研究。在项目执行期，申请人按照计划完成了研究工作：（1）依据场致荷电理论，推导了直流电场作用下雪晶颗粒运动的控制方程，研究了颗粒运动的物理过程，对比了交直流电场对颗粒运动的影响，揭示了绝缘子伞裙不同位置覆雪形态的差异，建立了绝缘子覆雪增长动态模型，并进行了试验验证，实现了绝缘子覆雪增长的三维可视化模拟；（2）基于覆雪绝缘子闪络试验，对比分析了自然环境与人工气候室覆雪绝缘子交直流闪络特性和放电发展过程的差异，并研究了直流放电电弧的动态特性，建立了电弧的电阻、电感和电容(R-L-C)的时域数学模型和剩余雪层电阻的时域数学模型；（3）根据覆雪绝缘子闪络过程中的试验现象，考虑闪络过程中电弧与雪层并存的特征，联合R-L-C时域模型和剩余雪层电阻时域模型，构建了覆雪绝缘子放电发展的物理数学模型，利用能量守恒定律，建立了覆雪绝缘子动态闪络模型，并通过试验进行了验证。本项目的研究成果可推进绝缘子覆雪从试验研究和静态模型向数值模拟和动态模型发展。