山火引发高压和超高压输电线路跳闸的特性及机理

Recently and nationally wildfires have frequently caused the breakdowns of transmission lines. The stability and reliability of the whole electric power system are badly threatened. From the viewpoint of diaster prevention, this project adopts the route of factor examination and reverse tracing of the evolution of physical and chemical properties. The flashover properties and related reflecting parameters are to be explored by field surveys, accident statistics, small-scale characterization tests and medium-scale simulation tests. Decoupling control method shoud be developed to analyze the coupling effect among the three typical environmental factors (wind speed, slope and moisture content) that can affect the formation and properties of wildfires, among the four key fire source factors (high temperature, high heat output, severe flame and thick smoke) that can lead to the flashover of the high- and ultrahigh- voltage transmission lines, and between the three typical environmental factors and the four key factors, Hence, the coupling interaction modes and their function weight coefficients are obtained for the three typical environmental factors and the four key factors. Statistical analysis method should be developed to predict the formation probabilities of wildfires with medium and high intensities under the influences of the three typical environmental factors, and the occurence probabilities of flashovers under the influences of the four key factors belonging to wildfires. The evolution features of physical and chemical properties of conductors (steel cored aluminum stranded wires) are to be traced. Based on the above research results, the inherent mechanism of flashover induced by wildfires for transmission lines is to be comprehensively deduced. Certain paramter models are to be established among the three environmental factor parameters, the four key factor parameters (wildfire property parameters) and the flashover property parameters. Aiming at the key scientific and technological issues that need to be urgently solved in national economy and social development, this project urges the full overlapping and merging of electrodynamic science, fire science, material science, mathematics and relative disciplines. Therefore, this project shows prevailing scientific value, realistic meaning and applicative prospects.

近年来山火频繁引发输电线路跳闸事故，严重威胁到电力系统稳定性和可靠性。本项目从防灾角度出发，采用因素排查和物化特性演变反向追溯的思路，通过实地考察、事故统计、中小尺度模拟和表征试验探查跳闸特性和典型表征参数；发展解耦方法分别对影响山火形成和特性的三种典型环境因素（风速、坡度和湿度）间、致使输电线路跳闸的四种关键火源因素（高温、高热、热焰和烟尘）间以及环境因素与关键因素间的耦合效应进行解析，分别获取三种环境因素间和四种关键因素间的耦合作用模式和作用权重系数；发展统计分析方法预测环境因素影响下中高强度山火发生概率及其形成后关键因素影响下的跳闸发生概率；追踪过火后输电导线理化特性的演变；综合推演山火引发输电线路的本质跳闸机理，建立一定的参量模型。本项目瞄准国民经济和社会发展中迫切需要解决的关键科技问题，促进电力学、火灾学和材料学等学科的充分交叉融合，具有重要的科学价值、现实意义和应用前景。

数年来山火频繁诱发架空高压输电线路跳闸事故，阻碍大规模智能电网的良性建设和发展。由此，通过文献调研、实地考察、案例分析、事故统计、试验模拟和理论分析等手段对此议题开展研究，代表性工作包括10个方面：交叉性跨学科前沿追踪、非预期（易诱发输电线路跳闸）山火时间和空间分布特性、跳闸典型事故案例分析、植被型火源（木垛）下空气击穿放电特性、典型输电线路受火特性和机理分析、非预期山火条件和特征识别、跳闸行为和特性分析和识别、中高强度地表火和树冠火作用下初步跳闸机理、山火中高压输电线路-地面空间时序演化行为和机理分析，从中分析了不同强度山火类型中火羽流和烟羽流造成的高温、高热、热焰和浓烟火场环境对绝缘空气和输电线路的损益作用，探讨了风速、坡度和湿度等关键环境因素的影响效应，推演了输电线路相地和相间火焰离子化和放电通道的形成机理。结果表明，缓坡、斜坡以及90°以上的山谷夹角最易诱发山火并形成蔓延到输电线路走廊区域的中高火线强度上山地表火、冲冠火和树冠火，高温和热焰促发空气热电离和化学电离交融发生，火焰离子化加剧，针状烟尘（0.7-5.0 μm）易诱发畸形电场，风速超过4m/s时可使输电线路跳闸概率显著增加，植被型火焰可使单导线（110 kV）、双分裂（220 kV）和四分裂（500 kV）模拟导线下绝缘空气平均击穿场强分别下降72.96 %、71.09 %和66.64 %，烈火可同时使输电线路发生弧垂、熔断及诱使表面形成高电阻Al2O3薄膜并产生局部过热现象，火场和电场相互作用导致近地面层、中间层、近线路层出现水分汽化和输运、残炭余烬涌动、传热传质、气流辐散和辐合、全程荷电和电离及电荷富集和放电等复杂时序演化行为，“火舌”和“烟舌”产生“针尖”效应并形成极端不均匀电场，空间中热流涌动衔接小微尺度导电体形成二次离子和电子，发展流注和先导，构筑潜在放电通道。研究结果对从本质上提高空气绝缘水平避免闪络大有裨益。